Fabrication of 304L stainless steel and aluminum parts by laser foil printing and process automation

This work presents research conducted on a novel metal additive manufacturing process, called Laser Foil Printing (LFP), to fabricate metal parts with various geometries layer by layer using metal foil as the feedstock. To investigate the processability and characteristics of LFP for fabricating metal parts, the materials included 304L stainless steel and Al-1100 aluminum alloy. The LFP process parameter windows for both 304L and Al-1100 were determined, and the optimal process parameters with stable formation of the melt pools were selected to fabricate dense metal parts. The microstructure and properties of LFP-fabricated parts were characterized and analyzed using tensile testing, scanning electron microscopy, electron backscattered diffraction, and ANOVA analysis. The mechanical properties of fabricated parts were compared with those of parts fabricated by the Laser Powder Bed Fusion (L-PBF) process. The results showed that the 304L parts fabricated by LFP were 10-20% higher in strength and ductility than those fabricated by L-PBF due to the finer grains formed by faster cooling in LFP. Also, oxidation in LFP-fabricated parts was less compared with that in L-PBF fabricated parts because of smaller surface area in metal foil compared with metal powder. The density ( \u3e 99.3%) of Al-1100 aluminum alloy parts fabricated by LFP was much higher than the density ( \u3c 90%) of Al-1100 parts fabricated by L-PBF because of no air gaps in foil like those in powder particles. A fully automated LFP system was constructed and used to automatically fabricate 304L parts with various geometries. The parts’ dimensional accuracies and their mechanical properties were measured. These parts exhibited higher tensile strength than those fabricated by other laser additive manufacturing technologies --Abstract, page iv

B meson decays to baryons in the diquark model

We study B meson decays to two charmless baryons in the diquark model, including strong and electroweak penguins as well as the tree operators. It is shown that penguin operators can enhance \bar{B} \to \Bb_s \bar{\Bb} considerably, but affect \bar{B} \to \Bb_1 \bar{\Bb}_2 only slightly, where \Bb_{(1,2)} and \Bb_s are non-strange and strange baryons, respectively. The $\gamma$ dependence of the decay rates due to tree-penguin interference is illustrated. In principle, some of the \Bb_s \bar{\Bb} modes could dominate over \Bb_1 \bar{\Bb}_2 for $\gamma > 90^\circ$, but in general the effect is milder than their mesonic counterparts. This is because the $O_6$ operator can only produce vector but not scalar diquarks, while the opposite is true for $O_1$ and $O_4$. Predictions from diquark model are compared to those from the sum rule calculation. The decays \bar{B} \to \Bb_s \bar{\Bb}_s and inclusive baryonic decays are also discussed.Comment: 9 pages, 6 figures, Revte

Estimating fixed-effect panel stochastic frontier models by model transformation

Traditional panel stochastic frontier models do not distinguish between unobserved individual heterogeneity and inefficiency. They thus force all time-invariant individual heterogeneity into the estimated inefficiency. Greene (2005) proposes a true fixed-effect stochastic frontier model which, in theory, may be biased by the incidental parameters problem. The problem usually cannot be dealt with by model transformations owing to the nonlinearity of the stochastic frontier model. In this paper, we propose a class of panel stochastic frontier models which create an exception. We show that first-difference and within-transformation can be analytically performed on this model to remove the fixed individual effects, and thus the estimator is immune to the incidental parameters problem. Consistency of the estimator is obtained by either N→∞ or T→∞, which is an attractive property for empirical researchersStochastic frontier models; Fixed effects; Panel data

The Determinants of Price in Online Auctions: More Evidence from Quantile Regression

This study explores how seller reputations affect auction prices, and concludes that earlier findings may be biased due to the misspecification of seller reputation. This paper contributes to the literature by offering significant empirical evidence using Taiwanese Internet auction data. Our study reveals that the influence of seller reputations on auction prices is significant, irrespective of the assumptions of linear and non-linear relationships with price. However, failure to consider the non-linear setting of seller reputation would have led us to overestimate the impact of reputations on prices because marginal returns to an incremental increase in reputation declines rapidly for sellers who have more than 15 scores. In addition, using quantile regression, this study finds evidence of considerable differences in their impact on auction prices dependent on the distribution of price levels.Internet auction, reputation, Taiwan, Yahoo! Kimo, quantile regression

A Globally Flexible, Quadratic Almost Ideal Demand System: An Application for Meat Demand in Taiwan

A new demand system, combining the quadratic almost ideal demand system and the Fourier expenditure system, is introduced. An application for meat consumption in Taiwan indicates that the new demand system fits the data well and that the restriction to the usual specifications, such as locally flexible functional form, linear Engel curve, and both, are rejected.Food Consumption/Nutrition/Food Safety,

Lepton Flavor Violating Decays of Neutral Higgses in Extended Mirror Fermion Model

We perform the one-loop induced charged lepton flavor violating decays of the neutral Higgses in an extended mirror fermion model with non-sterile electroweak-scale right-handed neutrinos and a horizontal $A_4$ symmetry in the lepton sector. We demonstrate that for the 125 GeV scalar $h$ there is tension between the recent LHC result ${\cal B}(h \to \tau \mu) \sim$ 1% and the stringent limits on the rare processes $\mu \to e \gamma$ and $\tau \to (\mu$ or $e) \gamma$ from low energy experiments.Comment: 23 pages, 3 figures. Added some of referenc