Studies on turbulent momentum, heat and species transport during binary alloy solidification in a top-cooled rectangular cavity

A two-dimensional transient fixed-grid enthalpy-based numerical method is developed to analyze the effects of turbulent transport during a binary alloy solidification process. Turbulence effects are introduced through standard k-ε equations, where coefficients are appropriately modified to account for phase-change. Microscopically-consistent estimates are made regarding temperature-solute coupling in a non-equilibrium solidification situation. The model is tested against laboratory experiments performed using an NH₄Cl-H₂O system in a rectangular cavity cooled and solidified from the top. Particular emphasis is laid on studying the interaction between Rayleigh-Benard type convection and directional solidification in the presence of turbulent transport. Numerical predictions are subsequently compared with experimental results regarding flow patterns, interface growth and evolution of the temperature field, and the agreement is found to be good.     

A Fuzzy-Neural Network Method for Modeling Uncertainties in Soil-Structure Interaction Problems

Abstract:   Uncertainty often recurs in structural system characterization as well as in choosing the mechanical model and in calibrating it. When analyzing a structure founded in cohesionless soils, the uncertainty in system modeling comes from soil inherent variability, site conditions, construction tolerance, and failure mechanisms. In this research, a Fuzzy-Neural Network method to predict the behavior of structures built on complex cohesionless soils is proposed. The method is based on an Artificial-Neural Network (ANN) for modeling the soil-foundation interaction. Its learning process analyzes over 200 records of building foundations, tanks, and embankments settlements on sand and gravel. Once validated, ANN is introduced in the soil-foundation-sovrastructure interaction model. Using fuzzy sets to define vague and ambiguous variables, the Fuzzy-Neural Network method predicts the system behavior and quantifies the uncertainty of its response. A numerical example shows the method effectiveness in the case of uncertainty in soil parameters and gives suggestions for successive applications.     

Distributed Transmit Antenna Selection (DTAS) Under Performance or Energy Consumption Constraints

Motivated by the transmit antenna selection (TAS) concept, used in Multiple-Input-Multiple-Output systems, we argue for distributed transmit antenna selection (DTAS), which corresponds to a method of selecting a subset of available relays in cooperative diversity systems. Assuming amplify and forward relays, the proposed selection method represents a low-complexity tool for determining the optimum relaying set. Two optimization problems are studied: the error probability minimization subject to total energy consumption constraints, and the dual one, the total energy consumption minimization under error performance constraints. Numerical examples verify the advantage of the proposed method in adapting the number of relaying terminals to the desired performance-consumption tradeoff.     

Kriterien für die Zulassung von Tierarzneimitteln gegen Zeckenbefall bei Hunden und Katzen: Ein Überblick der aktuellen Anforderungen und Möglichkeiten unter Berücksichtigung der derzeitig gültigen Leitlinien

Ohne Zusammenfassung The online version of the original article can be found under doi:.     

Investigation into Polarization of Unloaded and Loaded Microstrip Square-Ring Antennas

The polarization characteristic of unloaded and loaded square-ring microstrip antennas is investigated. Several different loading types like single-stub, dual-stub, notch, gap and shorting-pin are considered and their effects are studied. Loading enables feeding using a 50-Omega probe. The simulation and measurement results show that the loading techniques excite a loaded TMy ₁₁ mode that is orthogonal to the unloaded TMx ₁₁ mode. This indicates that by loading the ring antenna its polarization can be switched adaptively. However, the purity of the loaded and unloaded modes depends on the loading type. For some loading types like gap and shorting-pin, the excitation of the unloaded mode seems negligible, in comparison to the loadings by stub and notch. For the stub and notch loaded antennas the unloaded mode is also present, and its excitation efficiency is frequency dependent. Thus, their polarization plane, which is due to both loaded TMy ₁₁ and unloaded TMx ₁₁ modes, also becomes frequency dependant. The results of this investigation can be useful in selecting the loading methods for high-impedance microstrip ring antennas, and control of their impedance and polarization. The knowledge of the antenna polarization is essential in communications, and its dependence on the loading type can be used as an important parameter in design of adaptive antennas and sensors.     

Electrochemical mass transfer between an impinging jet and a rotating disk in a confined system

This paper presents the mass transfer results from an impinging liquid jet to a rotating disk. The mass transfer coefficients were measured using the electrochemical limiting diffusion current technique (ELDCT). Rotational Reynolds number (Re_r) in the range of 3.4 × 10⁴–1.2 × 10⁵, jet Reynolds number (Re_j) 1.7 × 10⁴–5.3 × 10⁴ and non-dimensional jet-to-disk spacing (H/d) 2–8 were taken into consideration as parameters. It was found that the jet impingement resulted in a substantial enhancement in the mass transfer compared to the case of the rotating disk without jet.     

Comparative Study of Rubidium and Cesium as Promoters in Carbon-supported Ruthenium Catalysts for Ammonia Synthesis

Sibunit-supported Ru-catalysts promoted with cesium or rubidium compounds have been comparatively studied with XPS. The cesium promoter interacts both with support and with active component. The absence of the promoter–support interaction in the case of rubidium provides a stronger interaction between promoter and active component compared to the cesium-based catalysts. These differences in the promoter–support and promoter–metal interactions are exhibited when a sequence of ruthenium and alkali introduction are changed.     

Smart phones and interactive reports leave traffic in the rearview mirror

To convey the dynamic information related to traffic conditions in various parts of a city, we propose an environment utilizing the technology of smart phones to provide information anywhere and anytime. Called ";The Interactive Traffic Beat Project,"; it uses a Web-based service to deliver this information to people through their cell phones at the right time so that valuable time can be saved and the chaos on the roads can be managed.     

Terahertz imaging: materials and methods

Terahertz (THz) imaging is rapidly developing. We present two new methods, based respectively on (a) a broadband thermal source (globar) and (b) a coherent, monochromatic source (optically-pumped THz laser). A room-temperature detector (Golay cell) is employed. Image quality is similar to that reported by others using more complex sources (quantum cascade lasers) and detectors (superconducting tunneling junctions).