A Robust Approach to Optimal Matched Filter Design in Ultrasonic Non-Destructive Evaluation (NDE)

The matched filter was demonstrated to be a powerful yet efficient technique to enhance defect detection and imaging in ultrasonic non-destructive evaluation (NDE) of coarse grain materials, provided that the filter was properly designed and optimized. In the literature, in order to accurately approximate the defect echoes, the design utilized the real excitation signals, which made it time consuming and less straightforward to implement in practice. In this paper, we present a more robust and flexible approach to optimal matched filter design using the simulated excitation signals, and the control parameters are chosen and optimized based on the real scenario of array transducer, transmitter-receiver system response, and the test sample, as a result, the filter response is optimized and depends on the material characteristics. Experiments on industrial samples are conducted and the results confirm the great benefits of the method

Puzzling Tax Structures in Developing Countries: A Comparison of Two Alternative Explanations

Observed economic policies in developing countries differ sharply both from those observed among developed countries and from those forecast by existing models of optimal policies. For example, developing countries rely little on broad-based taxes, and make substantial use of tariffs and seignorage as nontax sources of revenue. The objective of this paper is to contrast the implications of two models designed to explain such anomalous policies. One approach, by Gordon-Li (2005), focuses on the greater difficulties faced in poor countries in monitoring taxable activity, and explores the best available policies given such difficulties. The other, building on Grossman-Helpman (1994), presumes that political-economy problems in developing countries are worse, leading to worse policy choices. The paper compares the contrasting theoretical implications of the two models with the data, and finds that the political-economy approach does poorly in reconciling many aspects of the data with the theory. In contrast, the forecasts from Gordon-Li model are largely consistent with the data currently available.

Tax Structure in Developing Countries: Many Puzzles and a Possible Explanation

Tax policies seen in developing countries are puzzling on many dimensions. To begin with, revenue/GDP is surprisingly small compared with that in developed economies. Taxes on labor income play a minor role. Taxes on consumption are important, but effective tax rates vary dramatically by firm, with many firms avoiding taxes entirely by operating through cash in the informal economy and others facing very high liabilities. Taxes on capital are an important source of revenue, as are tariffs and seignorage, all contrary to the theoretical literature. In this paper, we argue that all of these aspects of policy may be sensible responses if a government is able in practice to collect taxes only from those firms that make use of the financial sector. Through use of the financial sector, firms generate a paper trail, facilitating tax enforcement. The threat of disintermediation then limits how much can be collected in taxes. Taxes can most easily be collected from the firms most dependent on the financial sector, presumably capital-intensive firms. Given the resulting differential tax rates by sector, other policies would sensibly be used to offset these tax distortions. Tariff protection for capital-intensive firms is one. Inflation, imposing a tax on the cash economy is another.

MEMS-actuated wavelength drop filter based on microsphere whispering gallery modes

MEMS-enabled tuneable optical coupling between optical microsphere resonators and optical fibre waveguides is reported. We describe the design, fabrication and experimental characterization of a MEMS platform, based on electrothermal actuators, which controls the resonator-to-waveguide separation. We compare the simulated and experimental displacements of the actuators in an unloaded and loaded state, where the load is a 1 mm optical spherical resonator. We then demonstrate the proof of concept application of selective wavelength dropping using the MEMS platform by modulating the coupling between the spherical resonator and a tapered optical fibre waveguide

Interplay of water and a supramolecular capsule for catalysis of reductive elimination reaction from gold.

Supramolecular assemblies have gained tremendous attention due to their ability to catalyze reactions with the efficiencies of natural enzymes. Using ab initio molecular dynamics, we identify the origin of the catalysis by the supramolecular capsule Ga4L612- on the reductive elimination reaction from gold complexes and assess their similarity to natural enzymes. By comparing the free energies of the reactants and transition states for the catalyzed and uncatalyzed reactions, we determine that an encapsulated water molecule generates electric fields that contributes the most to the reduction in the activation free energy. Although this is unlike the biomimetic scenario of catalysis through direct host-guest interactions, the electric fields from the nanocage also supports the transition state to complete the reductive elimination reaction with greater catalytic efficiency. However it is also shown that the nanocage poorly organizes the interfacial water, which in turn creates electric fields that misalign with the breaking bonds of the substrate, thus identifying new opportunities for catalytic design improvements in nanocage assemblies

Generalized Quantum Telecloning

We present a generalized telecloning (GTC) protocol where the quantum channel is non-optimally entangled and we study how the fidelity of the telecloned states depends on the entanglement of the channel. We show that one can increase the fidelity of the telecloned states, achieving the optimal value in some situations, by properly choosing the measurement basis at Alice's, albeit turning the protocol to a probabilistic one. We also show how one can convert the GTC protocol to the teleportation protocol via proper unitary operations.Comment: 6 pages, 1 figure, RevTex4; v2: published version, 8 pages, 4 figures, RevTex4, to appear at Eur. Phys. J.