Acoustic metafluids made from three acoustic fluids

Significant reduction in target strength and radiation signature can be achieved by surrounding an object with multiple concentric layers comprised of three acoustic fluids. The idea is to make a finely layered shell with the thickness of each layer defined by a unique transformation rule. The shell has the effect of steering incident acoustic energy around the structure, and conversely, reducing the radiation strength. The overall effectiveness and the precise form of the layering depends upon the densities and compressibilities of the three fluids. Nearly optimal results are obtained if one fluid has density equal to the background fluid, while the other two densities are much greater and much less than the background values. Optimal choices for the compressibilities are also found. Simulations in 2D and 3D illustrate effectiveness of the three fluid shell. The limited range of acoustic metafluids that are possible using only two fluid constituents is also discussed.Comment: 12 pages, 11 figure

Home high above and home deep down below -- lending in Hungary

In Hungary in the pre-crisis period, the bank sector-initiated private credit boom significantly contributed to the accumulation of economic imbalances. Nevertheless, before the 2008 crisis no special regulatory measure was taken to mitigate the foreign exchange lending to unhedged borrowers, which was a main moving force of the credit boom. Depreciation of forint-denominated subsidized housing loans and the increased risk premium significantly deteriorated customers'positions and resulted in rocketing nonperforming loans. A recession, deteriorating portfolios, and lack of efficient workout. The introduction of strict regulation froze banking activity and the danger of recovery without lending emerged. This paper compares the pre- and post-crisis lending activity and analyzes the lack of regulation in the pre-crisis period and the inefficient regulation in the post-crisis period.Debt Markets,Banks&Banking Reform,Currencies and Exchange Rates,Bankruptcy and Resolution of Financial Distress,Emerging Markets

Nonself-adjoint semicrossed products by abelian semigroups

Let $\mathcal{S}$ be the semigroup \mathcal{S}=\sum^{\oplus k}_{i=1}\Sc{S}_i, where for each $i\in I$, $\mathcal{S}_i$ is a countable subsemigroup of the additive semigroup \B{R}_+ containing 0. We consider representations of $\mathcal{S}$ as contractions $\{T_s\}_{s\in\mathcal{S}}$ on a Hilbert space with the Nica-covariance property: $T_s^*T_t=T_tT_s^*$ whenever $t\wedge s=0$. We show that all such representations have a unique minimal isometric Nica-covariant dilation. This result is used to help analyse the nonself-adjoint semicrossed product algebras formed from Nica-covariant representations of the action of $\mathcal{S}$ on an operator algebra $\mathcal{A}$ by completely contractive endomorphisms. We conclude by calculating the $C^*$-envelope of the isometric nonself-adjoint semicrossed product algebra (in the sense of Kakariadis and Katsoulis).Comment: 14 page

On the renormalization of the bosonized multi-flavor Schwinger model

The phase structure of the bosonized multi-flavor Schwinger model is investigated by means of the differential renormalization group (RG) method. In the limit of small fermion mass the linearized RG flow is sufficient to determine the low-energy behavior of the N-flavor model, if it has been rotated by a suitable rotation in the internal space. For large fermion mass, the exact RG flow has been solved numerically. The low-energy behavior of the multi-flavor model is rather different depending on whether N=1 or N>1, where N is the number of flavors. For N>1 the reflection symmetry always suffers breakdown in both the weak and strong coupling regimes, in contrary to the N=1 case, where it remains unbroken in the strong coupling phase.Comment: 13 pages, 2 figures, final version, published in Physics Letters

Electronic spectra of linear HC5_5H and cumulene carbene H2_2C5_5

The $1 ^3\Sigma_u^- \leftarrow X^3\Sigma_g^-$ transition of linear HC$_5$H (A) has been observed in a neon matrix and gas phase. The assignment is based on mass-selective experiments, extrapolation of previous results of the longer HC$_{2n+1}$H homologues, and density functional and multi-state CASPT2 theoretical methods. Another band system starting at 303 nm in neon is assigned as the $1 ^1 A_1 \leftarrow X ^1 A_1$ transition of the cumulene carbene pentatetraenylidene H$_2$C$_5$ (B).Comment: 7 pages, 4 figures, 5 table

Open Educational Resources (OER) for Control Systems Engineering: Development Case with LabVIEW, Simulink, and Camtasia

The aim of this paper is to report on the development of control systems open educational resources. The paper reports on two control systems education software: 1- A LabVIEW based Control Systems Analysis Toolkit (CSAT) which was developed to assist lecturers in teaching control engineering and students to understand theoretical concepts, and 2- A Process Control Virtual Laboratory (PCVL), developed using LabVIEW. Both software have been created as a stand-alone educational application together with a detailed manual and learning activities. Existing Simulink exercises have been enhanced and specific video tutorials for the Simulink exercises have been developed. Evaluations have been conducted indicating positive impact on students