The Effect of Metal Thickness on Si Wire to Plasmonic Slot Waveguide Mode Conversion

We investigate mode converters for Si wire to plasmonic slot waveguides at 1550 nm telecom wavelength. The structures are based on a taper geometry. We provide optimal dimensions with more than 90% power transmission for a range of metal (Au) thicknesses between 30-250 nm. We provide details on how to differentiate between the total power and the power in the main mode of the plasmonic slot waveguide. Our analysis is based on the orthogonality of modes of the slot waveguide subject to a suitable inner product definition. Our results are relevant for lowering the insertion loss and the bit error rate of plasmonic modulators.Comment: 4 pages, 7 figures, 2 tables, preprint version of the published paper, includes only the English abstrac

A parametric evaluation of the removal as(III) and as(V) from aqueous water by red mud

In the present study, removal of arsenide (As(III)) and arsenate As(V) ions from water/wastewater by adsorption on red mud is investigated. Laboratory experiments were carried out to analyze removal capacity of the adsorbents, to achieve adsorption isotherms and kinetic parameters. Optimum doses of adsorbents, pH dependence of solutions, and contact time have been discussed. This study proposes the potential adsorbent material for water/wastewater which is contaminated with As species

Enhancing an Embedded Processor Core with a Cryptographic Unit for Performance and Security

We present a set of low-cost architectural enhancements to accelerate the execution of certain arithmetic operations common in cryptographic applications on an extensible embedded processor core. The proposed enhancements are generic in the sense that they can be beneficially applied in almost any RISC processor. We implemented the enhancements in form of a cryptographic unit (CU) that offers the programmer an extended instruction set. The CU features a 128-bit wide register file and datapath, which enables it to process 128-bit words and perform 128-bit loads/stores. We analyze the speed-up factors for some arithmetic operations and public-key cryptographic algorithms obtained through these enhancements. In addition, we evaluate the hardware overhead (i.e. silicon area) of integrating the CU into an embedded RISC processor. Our experimental results show that the proposed architectural enhancements allow for a significant performance gain for both RSA and ECC at the expense of an acceptable increase in silicon area. We also demonstrate that the proposed enhancements facilitate the protection of cryptographic algorithms against certain types of side-channel attacks and present an AES implementation hardened against cache-based attacks as a case study

Few photon transport in a waveguide coupled to a pair of collocated two-level atoms

We calculate the one- and two-photon scattering matrices of a pair of collocated non-identical two-level atoms coupled to a waveguide. We show that by proper choice of a two-photon input, the background fluorescence by the atoms may be completely quenched, as a result of quantum interference, and that when the atoms' detuning is smaller than their linewidths, extremely narrow fluorescence features emerge. Furthermore, the system emits a two-photon bound state which can display spatial oscillations/quantum beats, and can be tuned from bunched to anti-bunched statistics as the total photon energy is varied

Synthesis of titanium dioxide nanoparticles and their application for simultaneous photocatalytic oxidation of As(III) and sorption of As(V)

In this study, the effectiveness of TiO2 nanoparticles in removing arsenic species from water was enhanced by the photocatalytic oxidation by conversion of As(III) to As(V), which adsorbs more strongly onto the solid phase of adsorbent than As(III). Anatase nanoparticles were synthesized by using sol-gel method and the synthesized nanoparticles were characterized by X-ray diffraction and scanning electron microscopy. Batch adsorption experiment was carried out to analyze As(III) removal capacity of the anatase nanoparticles with and without presence of photocatalytic oxidation reaction. The maximum % of removal of As(III) was found ~56% at pH 6, respectively, when 1 g l-1 anatase nanoparticles were used at the As0 1 ppm without presence of photocatalytic oxidation reaction. In contrast, over 94.7% As(V) have been removed by anatase nanoparticles in a period of 120 min UV-light irradiation. Using photocatalytic oxidation process, As(III) removal from water was improved by UV-irradiation

Conservation of Waterlogged Wood of the Yenikapı Shipwrecks, Istanbul-Türkiye

Theodosian Harbour was one of the principal harbors of Byzantine Constantinople, actively serving trading ships from the 4th to the early 11th centuries AD at the Sea of Marmara shore of the imperial center. Almost ten years of rescue excavations by Istanbul Archaeology Museums in the silted harbor site revealed considerable archaeological evidence dating from the Ottoman and Byzantine periods to the Neolithic age. The artifacts uncovered within the Byzantine harbor context constitute the majority of archaeological finds yielding much information on the trading network of the imperial center. Upon the invitation of the Istanbul Archaeological Museums, Istanbul University undertook the removal, documentation, and construction technology studies of twenty-seven shipwrecks and the conservation work of 31 shipwrecks. For conserving the waterlogged timbers, mainly PEG (polyethylene glycol), preimpregnation+vacume freeze drying, or melamine-formaldehyde (Kauramin®) resin for the highly-degraded timbers is used. The present paper discusses the conservation processes of the shipwrecks excavated under the responsibility of the Istanbul University’s Department of Conservation of Marine Archaeological Objects