First-principles study of ultrathin (2 \times 2) Gd nanowires encapsulated in carbon nanotubes

Using density functional calculations, we investigate the structural and magnetic properties of ultrathin Gd and Gd-carbide nanowires (NWs) encapsulated in narrow carbon nanotubes (CNTs). The equilibrium geometry of an encapsulated (2 \times 2) Gd-NW is markedly different from that of bulk Gd crystals. The charge-density analysis shows pronounced spin-dependent electron transfer in the encapsulated Gd-NW in comparison with that of Gd-carbide NWs. We conclude that Gd-CNT hybridization is primarily responsible for both the structural difference and electron transfer in the encapsulated Gd-NW.Comment: 18 pages, 6 figures. (JCP version: 7 pages and small figures

Maximum Score Estimation of Preference Parameters for a Binary Choice Model under Uncertainty

This paper develops maximum score estimation of preference parameters in the binary choice model under uncertainty in which the decision rule is affected by conditional expectations. The preference parameters are estimated in two stages: we estimate conditional expectations nonparametrically in the first stage and then the preference parameters in the second stage based on Manski (1975, 1985)'s maximum score estimator using the choice data and first stage estimates. The paper establishes consistency and derives rate of convergence of the two-stage maximum score estimator. Moreover, the paper also provides sufficient conditions under which the two-stage estimator is asymptotically equivalent in distribution to the corresponding single-stage estimator that assumes the first stage input is known. These results are of independent interest for maximum score estimation with nonparametrically generated regressors. The paper also presents some Monte Carlo simulation results for finite-sample behavior of the two-stage estimator

Potential Solution to Meet Growing Demands of Refractory Metal: Selective Laser Melting of Molybdenum-Tungsten Alloy

Selective laser melting (SLM) of refractory metals has been of high interest in research due to the metals’ potential desirable characteristics in aeronautical and space applications. In particular, molybdenum and tungsten have been the focus of several studies in the search for high temperature and high strength purposes in applications like supersonic aircraft, re-entry vehicles, nuclear fission, power generation, and other space systems. However, there is still a significant knowledge gap to process defect-free alloys and making use of them in practical engineering functions. The aim of this study is to characterize the relationship between the microstructure and mechanical properties of the additive manufacturing (AM) of molybdenum and 30% tungsten system (Mo-30W) specimens and interpret how unique microstructural characteristics and defects relating to AM of Mo-30W alloys influence the fracture behavior. This study provides qualitative and quantitative approaches to characterize microstructure and mechanical properties of the various Mo-30W by evaluating the effects of print chamber atmosphere, print speeds, build orientations, and post processing heat treatments through means of mechanical tests, chemical composition analysis, porosity analysis, and fracture surface assessment

Silicon nanowire devices

Transport measurements were carried out on 15–35 nm diameter silicon nanowires grown using SiH4 chemical vapor deposition via Au or Zn particle-nucleated vapor-liquid-solid growth at 440°C. Both Al and Ti/Au contacts to the wires were investigated. The wires, as produced, were essentially intrinsic, although Au nucleated wires exhibited a slightly higher conductance. Thermal treatment of the fabricated devices resulted in better electrical contacts, as well as diffusion of dopant atoms into the nanowires, and increased the nanowire conductance by as much as 10^4. Three terminal devices indicate that the doping of the wires is p type

The use of Deleuze's theory of assemblage for process-oriented methodology

"Dealing with the complexity of social change during the process of civilization, Deleuze and Guattari (1987) proposed the concept of an assemblage that is only grasped in the dynamic relation between the machinic assemblage (e.g., the structure of organizations, physical materials and resources) and the enunciative assemblage (e.g., regulations, governing principles and symbolic expressions). Exploring the complex relationship between social change and social networks in terms of Deleuze's theory of assemblage, we argue that the process-oriented methodology should be conceptualized as 'time-related research'. It is required to produce the 'process-generated data' in the form of Deleuze's sense of an event during the process of the time-related research. It includes the 'insider perspective' and 'judgment systems' which function as a detached 'outside perspective'. Such judgment systems are necessary for generating knowledge that supports social interventions in order to make or produce 'events data,' which are generated from an interaction between the machinic assemblages and the enunciative assemblages within social fields." (author's abstract

Mg Alloy Surface Treatment

Before the surface treatment of magnesium alloy, it is necessary to consider the degree of electrical resistance, the apparent surface condition, and the degree of corrosion resistance, so that the most appropriate method could be used for the surface to be treated. Magnesium alloy also follows the basic rule of metal, and the best method is to process after mechanical and chemical cleaning

Competition between structural distortion and magnetic moment formation in fullerene C20_{20}

We investigated the effect of on-site Coulomb interactions on the structural and magnetic ground state of the fullerene C$_{20}$ based on density-functional-theory calculations within the local density approximation plus on-site Coulomb corrections (LDA+$U$). The total energies of the high symmetry ($I_{h}$) and distorted ($D_{3d}$) structures of C$_{20}$ were calculated for different spin configurations. The ground state configurations were found to depend on the forms of exchange-correlation potentials and the on-site Coulomb interaction parameter $U$, reflecting the subtle nature of the competition between Jahn-Teller distortion and magnetic instability in fullerene C$_{20}$. While the non-magnetic state of the distorted $D_{3d}$ structure is robust for small $U$, a magnetic ground state of the undistorted $I_{h}$ structure emerges for $U$ larger than 4 eV when the LDA exchange-correlation potential is employed.Comment: 4 figures, 1 tabl