Modified ball bond shear test for determination of adhesion strength of cold spray splats

A modified ball bond shear test was developed to measure the adhesion of cold sprayed splats to both bulk substrates and cold sprayed coatings. The technique was applied to the deposition of Ti feedstock powder (spherical morphology, 29 μm average dia.) onto a commercially pure bulk Ti plate and onto Ti coatings prepared with the same feedstock powder. Both an adhesion strength and adhesion energy were measured, with trends in adhesion examined as a function of in-air particle velocities between 580 and 825 m/s. Comparisons between cold spray splat on bulk materials versus coatings were conducted for two deposition conditions (694 and 825 m/s). Generally, the adhesion for splats deposited at the higher deposition condition were insensitive to the substrate material, while splats deposited at the lower deposition condition adhered better to the bulk material than to the coatings.     

Influence of Helium and Nitrogen Gases on the Properties of Cold Gas Dynamic Sprayed Pure Titanium Coatings

This study investigates the effect of propellant gas, helium, and nitrogen during cold spraying of titanium coatings. Coatings were characterized by SEM and were evaluated for their deposition efficiency (DE), microhardness, and porosity. In selected conditions, three particle velocities were investigated in which for each condition, the propelling gases?? temperature and pressure were attuned to attain similar particle velocities for each gas. Observations show that loosely bonded particles can be detached by high-pressure supersonic gas stream. Selected coatings were characterized by XPS to analyze the occurrence of oxidation and nitridation. Although generally accepted that coating characteristics can be affected by particle temperature, results show that for the same particle velocity, DE and coating density are also a function of substrate temperature. In addition, a thick and fully dense cold sprayed titanium coating was achieved with optimized spray parameters and nozzle using helium. The corresponding average particle velocity was 1173 m/s.     

Three-dimensional non-isothermal model development of high temperature PEM Fuel Cells

A three-dimensional non-isothermal mathematical model is developed in a triple mixed serpentine flow multichannel domain for a high temperature PEM Fuel Cell having a phosphoric acid doped PBI membrane as electrolyte and an active area of 25 cm² within Comsol Multiphysics. The inlet temperatures of cathode and anode reactants are taken as 438 K. Model predicts pressure, and temperature distribution along the channels and membrane current density distribution over the membrane electrodes. The model results are obtained at two different operation voltages, 0.45 V and 0.60 V. Resulting average current densities are respectively 0.313 A cm^?2 and 0.224 A cm^?2. The non-isothermal model results are compared to isothermal model results from a previous study and various other single channel non-isothermal model results available in the literature. The pressure drop at cathode compartment is predicted to be 6500 Pa, whereas it is found to be 6400 Pa for the isothermal model. The temperature difference within the system is found to be 0.18 K for the operation voltage of 0.6 V, whereas this value increases to 0.31 K for the operation voltage of 0.45 V. The temperature difference isocontours are illustrated for the whole cell. Considering changes in temperature, one can employ isothermal operation assumption for this system as an approximation and simplification for the governing equations, since the variation in the temperature within the cell is less than 1 K. It should be emphasized that multichannel model predictions are more realistic compared to single channel models. The model developed here can be extended to larger electrode active area and different multichannel configurations.     

A pattern recognition approach to tone detection

A pattern recognition approach is proposed for tone detection. Three basic tone features are extracted from the signal in the form of power, mean frequency, and spectral concentration. These three features are calculated for each signal sample taken during the decision interval and are represented by points in a three dimensional space.The actual tone detection function is then performed by partitioning the feature space in two decision volumes corresponding to the two alternatives (tone present and absent respectively) and by identifying the presence of associated clusters. A reject option is available when the decision volumes are not complementary, and allows the system to be insensitive to very noisy samples (e.g. impulsive noise).A non-linear classification method is presented which provides adaptive and robust detection in presence of non gaussian noise. Moreover global performance may be optimized on-line for unknown or time varying environments.Hardware and Software simulation results are presented and show good performance in presence of impulsive and interference noise.     

Capacity achieving high rate space-time block codes

It is well known, that the Alamouti scheme is the only space-time code from orthogonal design achieving the capacity of multiple-input multiple-output (MIMO) wireless communication system with n/sub T/=2 transmit antennas and n/sub R/=1 receive antenna. In this work, we propose the n-times stacked Alamouti scheme for n/sub T/=2n transmit antennas and show that this scheme achieves the capacity in the case of n/sub R/=1 receive antenna. For the more general case of more than one receive antenna, we show that if the number of transmit antennas is higher than the number of receive antennas we achieve a high portion of the capacity with this scheme.     

Mechanical Property Mapping of Cold Sprayed Ti Splats and Coatings

Profile nanoindentation and nanoindentation mapping were used to investigate the mechanical properties of commercially pure cold spray Ti splats and coatings deposited at increasing deposition velocities. Three regions in the cold spray Ti splats have been indentified: the impact region, the jetting region, and the upper splat region. The mechanical properties measured in these regions were tied to the cold spray deposition process with help of optical and scanning electron microscopes. The jetting region was observed to contribute to a metallurgical bonding of cold spray splats to cold spray splats and was measured to have low hardness in comparison to the splat impact site and similar to the hardness in the upper splat region. No increase in the profile coatings hardness with increase in the particle in-flight velocity and coating thickness was found. A correlation between the mechanical properties and the presently known deposition temperature, stress and dislocation density models was made.     

Ranking kinematics for revising by contextual information

Annals of Mathematics and Artificial Intelligence - Probability kinematics is a leading paradigm in probabilistic belief change. It is based on the idea that conditional beliefs should be...     

On operations of soft sets

Soft set theory, proposed by Molodtsov, has been regarded as an effective mathematical tool to deal with uncertainties. In this paper, first we prove that certain De Morgan’s law hold in soft set theory with respect to different operations on soft sets. Then, we discuss the basic properties of operations on soft sets such as intersection, extended intersection, restricted union and restricted difference. Moreover, we illustrate their interconnections between each other. Also we define the notion of restricted symmetric difference of soft sets and investigate its properties. The main purpose of this paper is to extend the theoretical aspect of operations on soft sets.