Solidification Morphology Analysis of SLM of Cu Powder

The solidification morphology analysis of fine Cu powder melted by a raster scanned energy beam from a focused Nd:YAG laser is presented here. The powder was processed inside of sealed chamber where it was subjected to a high vacuum cycle. The laser fusion process consisted raster scanning a narrow rectangular pattern with a high density of scanning lines, the chamber was purged with inert gas during the process. Up to a 3.3 mm/s laser travel speed and maximum laser power level of 240 W were used to melt a 2 mm thick bed of loose powder. The resulting solidified ingots were separated into categories based on their shape integrity. Metallographic analysis by means of optical microscopy and scanning electron microscopy was performed on the cross section and longitudinal section of the ingots with homogeneous surface and complete shape integrity. Characterization revealed an elongated columnar grain structure with a grain orientation along the direction of the laser travel direction, some degree of porosity was observed too in some of the specimens. It was observed that grains diameter ranged from 10 to 100 µm and contained a two phase eutectic microstructure of copper and it oxides. Oxygen content was accounted from a 5.5 up to 8.1 atomic percent, a small percentage of chlorine was present, too. A 2 to 8 percent variation in the Vickers microhardness values were found between the different specimens when measured along the longitudinal section. These HV values corresponded to approximate 20-25% cold rolled oxygen free copper (80-90 HV). The ingots thus produced suggest that a multilayer structure from Cu powder could be build by the SLM process having sufficiently adequate compositional, microstructure and mechanical properties for functional applications.Mechanical Engineerin

Mechanical Behavior of SLS Components in Relation to the Build Orientation During the Sintering Process as Measured by ESPI

Selective Laser Sintering (SLS) allows producing real parts from CAD data from materials with different characteristics compared to the final model, presenting dissimilar mechanical properties between the prototype and the product. The purpose of this work is to correlate the mechanical behavior of beam-type specimens produced by SLS with build orientation angle used as a process parameter, also attempting to demonstrate how this parameter affects the accuracy of the Empirical Similitude Method (ESM). ESM presents itself as a valuable tool when creating scale models with SLS, specifically in the framework of evolutionary product design. More specifically, the Young modulus variation of test specimens of well-known dimensions and material (DuraformTM PA2 ), will be characterized by loading them within the elastic range. The resulting elastic deformations will be measured using the technique of Electronic Speckle Pattern Interferometry (ESPI) for small deformations in an out-of-plane configuration, contrasting these results with the elastic theory of deformations. As a main result, it was found that there exists a linear correlation between the build angle and the elastic modulus of the parts. Secondly, it was demonstrated empirically that the ESM predicts better the mechanical response of the part than TSM. Moreover, a 30% error reduction can be achieved within the ESM when using the build orientation angle as a process parameter.Mechanical Engineerin

A Mathematical Assessment of the Isolation Tree Method for Outliers Detection in Big Data

In this paper, the mathematical analysis of the Isolation Random Forest Method (IRF Method) for anomaly detection is presented. We show that the IRF space can be endowed with a probability induced by the Isolation Tree algorithm (iTree). In this setting, the convergence of the IRF method is proved using the Law of Large Numbers. A couple of counterexamples are presented to show that the original method is inconclusive and no quality certificate can be given, when using it as a means to detect anomalies. Hence, an alternative version of IRF is proposed, whose mathematical foundation, as well as its limitations, are fully justified. Finally, numerical experiments are presented to compare the performance of the classic IRF with the proposed one.Comment: 21 pages, 14 figures, 3 table

Objective Priors for Estimation of Extended Exponential Geometric Distribution

A Bayesian analysis was developed with different noninformative prior distributions such as Jeffreys, Maximal Data Information, and Reference. The aim was to investigate the effects of each prior distribution on the posterior estimates of the parameters of the extended exponential geometric distribution, based on simulated data and a real application

Laser Melting of Ti-Ni Shape Memory Alloy

The applicability of laser melting in fabrication of Ti-Ni shape memory alloy was investigated experimentally. Elemental powders of Ti and Ni and mechanically alloyed (MA) TiNi powder were used to fabricate specimens. The effects of powder characteristics on the microstructure and shape memory characteristics of the alloy were examined. The morphology and microstructure of the laser-melted specimens were varied with fabrication conditions. Parts fabricated from elemental powders exhibited a shape memory effect, but those from MA powder did not exhibit it, although the latter showed more homogeneous microstructure than the former.Mechanical Engineerin

Single Channel Function of Inositol 1,4,5-trisphosphate Receptor Type-1 and -2 Isoform Domain-Swap Chimeras

The InsP3R proteins have three recognized domains, the InsP3-binding, regulatory/coupling, and channel domains (Mignery, G.A., and T.C. Südhof. 1990. EMBO J. 9:3893–3898). The InsP3 binding domain and the channel-forming domain are at opposite ends of the protein. Ligand regulation of the channel must involve communication between these different regions of the protein. This communication likely involves the interceding sequence (i.e., the regulatory/coupling domain). The single channel functional attributes of the full-length recombinant type-1, -2, and -3 InsP3R channels have been defined. Here, two type-1/type-2 InsP3R regulatory/coupling domain chimeras were created and their single channel function defined. One chimera (1-2-1) contained the type-2 regulatory/coupling domain in a type-1 backbone. The other chimera (2-1-2) contained the type-1 regulatory/coupling domain in a type-2 backbone. These chimeric proteins were expressed in COS cells, isolated, and then reconstituted in proteoliposomes. The proteoliposomes were incorporated into artificial planar lipid bilayers and the single-channel function of the chimeras defined. The chimeras had permeation properties like that of wild-type channels. The ligand regulatory properties of the chimeras were altered. The InsP3 and Ca2+ regulation had some unique features but also had features in common with wild-type channels. These results suggest that different independent structural determinants govern InsP3R permeation and ligand regulation. It also suggests that ligand regulation is a multideterminant process that involves several different regions of the protein. This study also demonstrates that a chimera approach can be applied to define InsP3R structure-function

Finite-size scaling exponents in the interacting boson model

We investigate the finite-size scaling exponents for the critical point at the shape phase transition from U(5) (spherical) to O(6) (deformed $\gamma$-unstable) dynamical symmetries of the Interacting Boson Model, making use of the Holstein-Primakoff boson expansion and the continuous unitary transformation technique. We compute exactly the leading order correction to the ground state energy, the gap, the expectation value of the $d$-boson number in the ground state and the $E2$ transition probability from the ground state to the first excited state, and determine the corresponding finite-size scaling exponents.Comment: 4 pages, 3 figures, published versio

Reacción del precio de las acciones a los cambios de estructura de capital en empresas chilenas: Examinando los efectos de la estructura de propiedad, oportunidades de crecimiento y leverage

We analyzed the effects of ownership structure, capital structure and growth opportunities on stock price reactions when companies issued debt or equity.Our results, based on event study methodology and IV regressions from a sample of 70 Chilean firms, indicate that controlling shareholder ownership has a negative effect on stock price reactions for debt issuances and a positive effect for equity issuance. These results indicate that debt issuances are a substitute for majority shareholder monitoring, and that equity issuances are associated with superior corporate performance. Equity issuances are a means for expropriating wealth from non-controlling shareholders. Debt and growth opportunities have a non-linear effect.En este artículo analizamos los efectos de la estructura de propiedad, estructura de capital y las oportunidades de crecimiento sobre la reacción del precio delas acciones cuando las empresas emiten deuda o capital. Nuestros resultados, basados en la metodología de análisis de eventos y regresiones IV sobre unamuestra de 70 empresas chilenas, indican que la propiedad de los accionistas controladores tiene un efecto negativo en la reacción del precio de las acciones cuando las empresas emiten deuda y positivo cuando emiten acciones. Este resultado indica que las emisiones de deuda son un sustituto del control mayoritario de los accionistas y las emisiones de capital se asocian con un mayor desempeño corporativo. Las emisiones de capital son un medio para expropiar riqueza de los accionistas no controladores. Las oportunidades de deuda y crecimiento tienen un efecto no lineal