Modeling of Bohemian and Moravian glass recipes from Gothic to Baroque periods

The Bohemian historical glasses have been neglected and have not been in focus of Archaeometric studies so far. Potassium-calcium wood ash glasses, produced in Bohemia and Moravia, from the beginning of the 14th century to the first half of the 18th century, are chemically different from the glasses produced in the same period in Western Europe. There are no written sources for glass batch recipes for Gothic (14th–1st half of 16th c.) and Renaissance (16th–17th c.) glass, while there are only few for the Baroque (end of 17th–18th c.) glass recipes. Systematically investigating the chemical composition and typology of archaeological glasses, we have chosen to reconstruct the glass recipes of potassium-calcium glasses from the three periods. In this study, the glass recipes (the ratio of the raw materials) were calculated based on the chemical composition of the historical glasses studied by X-Ray Fluorescence (XRF) and Scanning Electron Microscopy/Energy Dispersive System (SEM/EDS). The composition of the authentic natural raw materials was studied by XRF and X-Ray Diffraction (XRD): sand or quartz pebbles, beech ash and potash, limestone, NaCl, and As2O3. Model glasses confirmed our presumption of gradual development in the Bohemian glass batch recipes, which used very simple raw materials ratios.

Adaptive Numerical Modelling of Tsunami Wave Generation and Propagation with FreeFem++

A simplified nonlinear dispersive system of BBM-type, initially derived by D. Mitsotakis, is employed here in order to model the generation and propagation of surface water waves over variable bottom. The simplification consists in applying the so-called Boussinesq approximation. Using the finite element method and the FreeFem++ software, we solve numerically this system for three different complexities for the bathymetry function: a flat bottom case, a variable bottom in space, and a variable bottom both in space and in time. The last case is illustrated with the Java 2006 tsunami event. This article is designed rather as a tutorial paper even if it contains the description of completely new adaptation techniques.

Growth Kinetics of Interfacial Intermetallic Compound in Al(AA4343)/Steel(SUS316) Clad Strip

The composition and microstructure of intermetallic compounds (IMC) at the interface of aluminum(AA4343)-stainless steel(SUS316) were studied upon annealing at 550°C for 1h to 20h and at 610°C for 15min to 10h by means of optical microscope(OM) , scanning electron microscope (SEM) with energy dispersive system(EDS) and transmission Electron Microscopy (TEM). The results showed that the IMC was of 4.3μm to 36.1μm thick during heat treatment at 550°C for 1h to 20h, and the IMC contained Al-Fe-Si-Cr-Ni-Mo and Al-Fe-Si -Ni. During annealing at 610°C for 15min to 5h, the thickness of IMC was 31.2 μm to 208 μm, and the IMC were mainly of η-Fe2Al5 and τ10- Al4Fe1.7Si at 550°C for 10h. As the annealing time extended to 10h, natural delamination occurred at the interface between the aluminum alloy layer and IMC layer. The growth kinetics analysis showed that the relationship between the thickness of IMC “X” and time “t” followed the relational equation X=(kt)n. For AA4343(solid) - SUS316(solid), n was 1/2, and the growth constant k = 1.9×10-13m2/s at annealing temperature of 550 °C. When the temperature was 610°C, AA4343 - SUS316 was a liquid-solid contact reaction, n was 1, the growth constant k=1.45×10-8m/s.

Frequency-Dependent Schroeder Allpass Filters

Since the introduction of feedforward–feedback comb allpass filters by Schroeder and Logan, its popularity has not diminished due to its computational efficiency and versatile applicability in artificial reverberation, decorrelation, and dispersive system design. In this work, we present an extension to the Schroeder allpass filter by introducing frequency-dependent feedforward and feedback gains while maintaining the allpass characteristic. By this, we directly improve upon the design of Dahl and Jot which exhibits a frequency-dependent absorption but does not preserve the allpass property. At the same time, we also improve upon Gerzon’s allpass filter as our design is both less restrictive and computationally more efficient. We provide a complete derivation of the filter structure and its properties. Furthermore, we illustrate the usefulness of the structure by designing an allpass decorrelation filter with frequency-dependent decay characteristics.