554 research outputs found
Negative Refraction and Subwavelength Lensing in a Polaritonic Crystal
We show that a two-dimensional polaritonic crystal, made of metallic rods
that support well defined plasmon oscillations, can act in a narrow frequency
range as a medium in which a negative refraction and subwavelength lensing can
occur. We show that surface modes are excited on the surface of the lens, and
that they facilitate restoration of the evanescent waves, which carry the
subwavelength image information. We demonstrate that this can occur in the
visible frequency range, for a wide range of materials, including silver and
aluminum rods, and carbon nanotubes. This flexibility should allow for an
experimental demonstration of this phenomenon in the visible frequency range.Comment: 14 pages; 4 figure
PROOF OF CONCEPT FOR 3-D PRINTABLE GEOMETRY OF MICROFLUIDIC BENTHIC MICROBIAL FUEL CELL DEVICE (MBMFC) WITH SELF-ASSEMBLED WIRING
Extensive use of Unmanned Underwater Vehicles (UUVs) and remote equipment in future Naval operations leads to an energy logistics challenge for their rechargeable batteries. A solution to this challenge is a distributed network of renewable power sources detached from mainland power grids. One potential solution is Benthic Microbial Fuel Cell (BMFC) devices. BMFCs must be optimized and upscaled to produce power at relevant scales. 3-D printing is a promising manufacturing method to achieve scalable BMFC devices.
In this thesis, we devised, developed, and optimized a protocol for clearance of microfluidic channels using square cross-sections embedded within PolyJet 3-D-printed chips. The developed protocol demonstrated 75% volumetric clearance of the embedded channels. The protocol was then used to clear channels with T-shaped cross-sections, which were used to produce an experimental proof of principle for self-assembled wiring within the microchannels due to fluidic surface tension. These advancements have opened the door to embedded wiring for 3-D printed biofuel cells and other microfluidic technologies. When perfected and manufactured at scale, biofuel cells could provide a solution to the critical logistics problem of recharging UUVs and similar equipment employed in remote maritime environments, thereby making an exceptional contribution to the U.S. Navy, U.S. national security, and the related research fields.Office of Naval Research, Arlington, VA 22203Lieutenant, United States NavyApproved for public release. Distribution is unlimited
Test of high-energy hadronic interaction models with high-altitude cosmic-ray data
Emulsion experiments placed at high mountain altitudes register hadrons and high-energy γ-rays with an energy threshold in the TeV region. These secondary shower particles are produced in the forward direction of interactions of mainly primary protons and alpha-particles in the Earth’s atmosphere. Single γ’s and hadrons are mainly produced by the interactions of the primary
cosmic-ray nuclei of primary energy below 1015 eV. Therefore the measurements are sensitive to the physics of high-energy hadronic interaction models, e.g., as implemented in the Monte Carlo air shower simulation program CORSIKA. By use of detailed simulations invoking various different models for the hadronic interactions we compare the predictions for the single-particle spectra with data of the Pamir experiment. For higher primary energies characteristics of so-called gamma-ray families are used for the comparisons. Including detailed simulations for the Pamir detector we found that the data are incompatible with the HDPM and SIBYLL 1.6 models, but are in agreement with QGSJET, neXus, and VENUS
Empirical description of the hadron-hadron and hadron-nucleus interaction at the accelerator energy range
Taking into account several assumptions, a formula is transformed into two expressions for kaon and baryon plus antibaryon production in proton interaction and for pion production in pion interactions. Combining both formulae, expression are obtained for the spectrum of kaons and baryons plus antibaryons produced in the meson interactions. For analysis of the cosmic ray propagation in the atmosphere in actual fact, instead of the formulae for interactions of protons and mesons with protons, formulae appropriate for interactions with air nuclei was used. Using the method outlined among others by Elias et al. (1980) simple corrections were introduced to the derived expressions to account for the fact that the target is an air nucleus
Improved superlensing in two-dimensional photonic crystals with a basis
We study propagation of light in square and hexagonal two-dimensional
photonic crystals. We show, that slabs of these crystals focus light with
subwavelength resolution. We propose a systematic way to increase this
resolution, at an essentially fixed frequency, by employing a hierarchy of
crystals of the same structure, and the same lattice constant, but with an
increasingly complex basis.Comment: 16 Pages, 5 Figure
String attractors : Verification and optimization
String attractors [STOC 2018] are combinatorial objects recently introduced to unify all known dictionary compression techniques in a single theory. A set γ ⊆ [1.n] is a k-attractor for a string S ∈ Σn if and only if every distinct substring of S of length at most k has an occurrence crossing at least one of the positions in γ. Finding the smallest k-attractor is NP-hard for k ≥ 3, but polylogarithmic approximations can be found using reductions from dictionary compressors. It is easy to reduce the k-attractor problem to a set-cover instance where the string's positions are interpreted as sets of substrings. The main result of this paper is a much more powerful reduction based on the truncated suffix tree. Our new characterization of the problem leads to more efficient algorithms for string attractors: we show how to check the validity and minimality of a k-attractor in near-optimal time and how to quickly compute exact solutions. For example, we prove that a minimum 3-attractor can be found in O(n) time when |Σ| ∈ O(3+ϵ√log n) for some constant ϵ > 0, despite the problem being NP-hard for large Σ. © Dominik Kempa, Alberto Policriti, Nicola Prezza, and Eva Rotenberg.Peer reviewe
Analisis Biaya Elemental Untuk Perencanaan Biaya Proyek Apartemen
Apartment's project cost planning involves a Quantity Surveyor to determine the target cost (budget) for the owner. Target cost must included all elements of the existing building. This study aims to determine the format and price range of each building element in the elemental cost analysis for apartment's project cost planning.The data were obtained by looking at historical data of the middle class apartment's projects Bill of Quantity in area of Surabaya, Solo and Semarang with reference to the format NPWC List of Elements, Australia.The results of the data analysis showed that the format of building elements that can be used in elemental cost analysis consists of 11 major elements are Preliminaries, Sub-structure, Super-structure, Finishes, Fittings, Services, Site Works, External Services, Waterproofing, Grills & Iron, and Pool. While the price range of elements in the elemental cost analysis showed that the apartment's project which has a basement, the price difference is 20-30% larger than projects that do not have a basement. For the project which has storey height ≥ 3m, the price difference is 3.5-20% larger than projects which has storey height < 3m. For projects which has a basement & storey height ≥ 3m, the price difference is 30% larger than the project which has a basement & storey height <3m
Magnetothermal Conductivity of Highly Oriented Pyrolytic Graphite in the Quantum Limit
We report on the magnetic field (0TT) dependence of the
longitudinal thermal conductivity of highly oriented pyrolytic
graphite in the temperature range 5 K 20 K for fields parallel to
the axis. We show that shows large oscillations in the
high-field region (B > 2 T) where clear signs of the Quantum-Hall effect are
observed in the Hall resistance. With the measured longitudinal electrical
resistivity we show that the Wiedemann-Franz law is violated in the high-field
regime.Comment: 4 Figures, to be published in Physical Review B (2003
Experimental Investigation of the Nature of the Knee in the Primary Cosmic Ray Energy Spectrum with the GAMMA experiment
We present preliminary results obtained by a novel difference method for the
study of the nature of the knee in the energy spectrum of the primary cosmic
radiation. We have applied this method to data from the GAMMA experiment in
Armenia. The analysis provides evidence for the possible existence of a nearby
source of primary cosmic rays in the Southern hemisphere.Comment: 17 pages, 5 figure
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