Mixtures of Shifted Asymmetric Laplace Distributions

A mixture of shifted asymmetric Laplace distributions is introduced and used for clustering and classification. A variant of the EM algorithm is developed for parameter estimation by exploiting the relationship with the general inverse Gaussian distribution. This approach is mathematically elegant and relatively computationally straightforward. Our novel mixture modelling approach is demonstrated on both simulated and real data to illustrate clustering and classification applications. In these analyses, our mixture of shifted asymmetric Laplace distributions performs favourably when compared to the popular Gaussian approach. This work, which marks an important step in the non-Gaussian model-based clustering and classification direction, concludes with discussion as well as suggestions for future work

Unsupervised Learning via Mixtures of Skewed Distributions with Hypercube Contours

Mixture models whose components have skewed hypercube contours are developed via a generalization of the multivariate shifted asymmetric Laplace density. Specifically, we develop mixtures of multiple scaled shifted asymmetric Laplace distributions. The component densities have two unique features: they include a multivariate weight function, and the marginal distributions are also asymmetric Laplace. We use these mixtures of multiple scaled shifted asymmetric Laplace distributions for clustering applications, but they could equally well be used in the supervised or semi-supervised paradigms. The expectation-maximization algorithm is used for parameter estimation and the Bayesian information criterion is used for model selection. Simulated and real data sets are used to illustrate the approach and, in some cases, to visualize the skewed hypercube structure of the components

Parsimonious Shifted Asymmetric Laplace Mixtures

A family of parsimonious shifted asymmetric Laplace mixture models is introduced. We extend the mixture of factor analyzers model to the shifted asymmetric Laplace distribution. Imposing constraints on the constitute parts of the resulting decomposed component scale matrices leads to a family of parsimonious models. An explicit two-stage parameter estimation procedure is described, and the Bayesian information criterion and the integrated completed likelihood are compared for model selection. This novel family of models is applied to real data, where it is compared to its Gaussian analogue within clustering and classification paradigms

Research of the alloying additives content in high-silver solders on their susceptibility to soldering process and basic performance properties

Copper and its alloys with steel, including stainless steel, are soldered using brazing materials CuAgZn and CuAg- ZnSn. They are used for making connections in heating, cooling and renewable energy sources (RES) devices. The elements used in the above-mentioned alloys affect wettability, castability, corrosion resistance, impact resistance, plasticity, stress resistance and also increase the melting point of the solder. The article presents the impact of the percentage of alloying additives covered by the EN ISO 17672 standard on performance and susceptibility to soldering brazing materials Ag44 and Ag40Sn

Research of the alloying additives content in high-silver solders on their susceptibility to soldering process and basic performance properties

Copper and its alloys with steel, including stainless steel, are soldered using brazing materials CuAgZn and CuAg- ZnSn. They are used for making connections in heating, cooling and renewable energy sources (RES) devices. The elements used in the above-mentioned alloys affect wettability, castability, corrosion resistance, impact resistance, plasticity, stress resistance and also increase the melting point of the solder. The article presents the impact of the percentage of alloying additives covered by the EN ISO 17672 standard on performance and susceptibility to soldering brazing materials Ag44 and Ag40Sn

Graphite crystallizer and its surface quality as a factor affecting the copper continuous casting process

Pure copper is one of the best conducting metals among known materials, making it the first choice for wires and microwires. However, before subjecting to metal working, the material is being manufactured in the continuous casting lines. The experimental study conducted in laboratory conditions proved that the external surface quality, and thus the contact quality with the cooling system is being responsible for the worsening or improving of the heat transfer and therefore the temperature of the crystallizer itself. The conducted study might function as sort of a guideline for the industrial process

Graphite crystallizer and its surface quality as a factor affecting the copper continuous casting process

Pure copper is one of the best conducting metals among known materials, making it the first choice for wires and microwires. However, before subjecting to metal working, the material is being manufactured in the continuous casting lines. The experimental study conducted in laboratory conditions proved that the external surface quality, and thus the contact quality with the cooling system is being responsible for the worsening or improving of the heat transfer and therefore the temperature of the crystallizer itself. The conducted study might function as sort of a guideline for the industrial process

Optimalization of the metallurgical synthesis parameters of CuZn37 brass with nickel and silicon alloy additives

The modifying possibility of the commercial CuZn37 brass (M63) with nickel and silicon is being discussed throughout the article. The proposed alloy additives made it possible to improve the commercial brass properties by precipitation hardening, thus making it extremely competitive in comparison to base material. The study also discussed the conditions (temperature and time) of the metallurgical synthesis and its influence on the weight percentage of not only proposed alloy additives but also the amount of zinc loss from the commercial brass due to the evaporation during the metallurgical processes

Research on Cu-Mg castings cold drawing process and analysis of mechanical and electrical properties of obtained wires

The aim of the conducted research works which are presented in the article was to determine the mechanical and electrical properties of Cu-Mg wires obtained in cold drawing process with total deformation at the level of 95 %. Base material for the research was obtained with the use of continuous casting process which allowed to produce CuMg0.02, CuMg0.05 and CuMg0.5 cylindrical rods with 9,5 mm diameter which were next cold drawn up to 1,97 mm diameter. After the cold drawing process Vickers hardness measurements along with static tensile test and electrical conductivity analysis were performed in order to determine the evolution of castings properties as a result of the applied cold deformation