128,310 research outputs found
Periodic solutions of Duffing's equations with superquadratic potential
No full textAbstractThis paper is devoted to the study of harmonic and subharmonic solutions for the second order scalar nonlinear Duffing's equation x″ + g(x) = p(t, x, x′), where g and p are continuous functions with p bounded and periodic in the first variable and g satisfying the assumption g(x)sign(x) → + ∞, as ¦x¦ → + ∞. Among other results, we prove the existence of infinitely many harmonic and subharmonic solutions (of any order) p = p(t) and if the potential G(x) of g(x) satisfies certain conditions of superquadratic growth at ∞. The new existence results can be applied to situations in which the more classical superlinear growth condition g(x)x → + ∞, as ¦x¦ → + ∞, is not satisfied. In this manner, various preceding theorems are improved and sharpened (see the “Introduction” for more details). Proofs are based on a generalized version of the Poincaré-Birkhoff “twist” theorem due to W. Ding
Single-scattering properties of ice particles in the microwave regime: Temperature effect on the ice refractive index with implications in remote sensing
No full textThis database is from the paper: Ding, J., L. Bi, P. Yang, G. W. Kattawar, F. Weng, Q. Liu, and T. Greenwald, 2017: Single-scattering properties of ice particles in the microwave regime: temperature effect on the ice refractive index with implications in remote sensing, Journal of Quantitative Spectroscopy & Radiative Transfer, 190, 26-37. DOI: 10.1016/j.jqsrt.2016.11.026
Nanostructured optical fibre tapers and related applications
No full textIn the last decade, optical fibre tapers have attracted considerable interest because they offer a variety of enabling properties, including large evanescent fields, flexibility, configurability, high confinement, robustness and compactness. These distinctive features have been exploited in a wealth of applications ranging from telecommunication devices to sensors, from optical manipulation to high-Q resonators. Nanostructures on the optical fibre tapers are very promising since the size of the device can be extremely small. With the development of nanostructuring methods, sub-wavelength feature sizes have been achieved. In this thesis, nanostructured optical fibre tapers and some related applications are discussed.Light confinement is limited by diffraction and the minimum spot size is related to the light wavelength. In this thesis, light confinement in two and three dimensions is proposed and achieved with two typologies of nanostructured optical fibre tapers. The first group of devices exploits plasmons excited at the optical fibre tips to obtain high transmissivity, and confine light to a sub-wavelength dimension. Optical fibre tips were designed according to numerical simulations and coated by a layer of gold; an extremely small aperture was then opened at the tip apex. The experimental characterization and simulation results showed their improved transmission efficiency (higher than 10-2) and thermal expansion measurements showed no shape changes could be detected within the accuracy of the system (~2 nm) for 9 mW injected powers. Effective confinements to 10 nm or smaller can be envisaged by decreasing the aperture size and slope angle. Application of this small spot size source can include scanning near-field optical microscope, optical recording, photolithography and bio-sensing.The second group achieves three dimensional light confinement exploiting a Fabry-Perot microcavity formed by a microfibre grating similar to those used in distributed feedback lasers. Microfibres were patterned using a Focused Ion Beam (FIB) system. In this structure, the microcavity provides longitudinal light confinement, whereas air dielectric guiding by the microfibre provides diffraction limited confinement in the other two dimensions. Due to the high refractive index contrast between silica and air, strong reflection can be obtained by only dozens of notches. This device can be used for a wide range of applications, e.g. sensing and triggered single-photon sources.Light confinement in nanostructured optical fibre tapers was exploited in a micrometric thermometer. A compact thermometer based on a broadband microfibre coupler tip showed a dynamic range spanning from room temperature to 1511ºC with a response time of tens of microseconds. This is the highest temperature measured with a silica optical fibre device. An average sensitivity of 11.96 pm/ºC was achieved for a coupler tip with ~2.5 µm diameter. A resolution of 0.66ºC was achieved for a coupler tip diameter of ~12.6 µm. Better resolution can be achieved with smaller size microfibre coupler tips.Optical fibre tapers are commonly used to couple light to selected resonator modes. Here FIB was used to inscribe microgrooves on optical Bottleneck Microresonator (BMR) surfaces to excite selected whispering gallery modes. By monitoring the transmission spectrum of the optical fibre taper, substantial spectral clean-up was obtained in appropriately scarred BMRs. Single high-Q mode operation can be achieved by either using two asymmetrical perpendicular scars or placing the grooves closer to the BMR centre, providing the potential for high performance sensors and other optical devices.Finally, strong three dimensional localization has been achieved in Plasmonic Slot Nano-Resonators (PSNRs) embedded in a gold-coated optical fibre tapers. Different shapes PSNRs, embedded in thin gold metal film coated plasmonic microfibre, were numerically investigated. The intensity enhancement (in excess of 106) and the resonance wavelength depend on both the PSNR and microfibre dimensions. Theoretically and experimentally, the transversal excitation of a rectangular PSNR embedded in a thin gold film coated plasmonic fibre tip was discussed for the first time, and showed high localization and strong enhancement (7.24×103). This device can find a wide range of applications such as surface-enhanced Raman scattering, optical filtering, spectroscopy and bio-sensing
An Answer to Littlewood's Problem on Boundedness
No full textDing, T.. (1985). An Answer to Littlewood's Problem on Boundedness. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/3808
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
Das ding y los límites de la simbolización
No full textLa presente investigación "Das Ding y los límites de la simbolización, se enmarca en el proyecto de investigación "La melancolía. Del amor a la pulsión". El ...This research "Das Ding and the limits of symbolization", is part of research project "The melancholy.From love to drive". The aim is make an inquiry about t..
Hybrid interconnect network for on-chip low-power clock distribution
No full textClock is regarded as the heartbeat of modern synchronous digital integrated circuits. However, with the CMOS technology shrinking, it becomes critical to deliver high-quality global clock signal with low propagation delay and hence conventional metallic interconnect seems to meet its bottleneck, as a clock distribution network (CDN) might consume up to 50% of the overall power. To address these problems, this Letter proposes a novel combination of wireless and conventional metallic interconnect to improve the performance of on-chip clock distribution. By incorporating integrated wireless clock transceivers and efficient modulation technique, overall performance has been increased significantly with a total delay reduction of 66.8% compared with a new cornerstone tapered H-tree model from 400 to 130 ps. In addition, clock uncertainties are now predictable according to the displacement of transceivers,,33 ps of clock skew at 2.5 GHz input with highly unbalanced loads could be found within the proposed CDN, and hence, indicates a promising potential of future high-performance on-chip clock distribution.</p
Ding projective and Ding injective modules over trivial ring extensions
No full textsummary:Let be a trivial extension of a ring by an --bimodule such that , , and have finite flat dimensions. We prove that is a Ding projective left -module if and only if the sequence is exact and is a Ding projective left -module. Analogously, we explicitly describe Ding injective -modules. As applications, we characterize Ding projective and Ding injective modules over Morita context rings with zero bimodule homomorphisms
Reconstructed edges of T phase transition metal dichalcogenides
No full text© 2021 Elsevier LtdAs surfaces are to bulk materials, edge configurations greatly influence the properties and ensuing applications of two-dimensional (2D) materials. Being a large family of “beyond graphene”, 2D transition metal dichalcogenides (TMDCs) have many potential applications due to diverse phases and tunable properties. Unlike the well-studied H phase TMDCs initiated by MoS2, the edge structures of T phase TMDCs remain poorly studied. Herein, taking freestanding T phase PtSe2 as a prototype, we rationally construct 43 edge structures on the basis of conventional zigzag (ZZ) and armchair (AC) edges, and systematically evaluate their thermodynamic stabilities and relevant properties using density functional theory. Twelve most stable reconstructed edges (five ZZ-oriented and seven AC-oriented) are found to be highly stable at different experimental conditions, which can be achieved by precise control of synthesis conditions. Further Wulff constructions suggest hexagonal shapes with ZZ edges would be the equilibrium structures of the freestanding T phase PtSe2 clusters or quantum dots. Electronic structure calculations show tunable band gap via edge reconstruction. Some reconstructed edges also exhibit excellent catalytic activity for hydrogen evolution reaction. Our work is expected to advance the knowledge of edge structures of T-phase TMDCs, and motivates materials design via TMDC edge engineering.11Nsciescopu
The effect of high dietary magnesium level on laying performance and mineral content of eggshell and tibia ash in Tsaiya duck.
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