2,309 research outputs found
Bayesian Estimation of Mixed Multinomial Logit Models: Advances and Simulation-Based Evaluations
Variational Bayes (VB) methods have emerged as a fast and
computationally-efficient alternative to Markov chain Monte Carlo (MCMC)
methods for scalable Bayesian estimation of mixed multinomial logit (MMNL)
models. It has been established that VB is substantially faster than MCMC at
practically no compromises in predictive accuracy. In this paper, we address
two critical gaps concerning the usage and understanding of VB for MMNL. First,
extant VB methods are limited to utility specifications involving only
individual-specific taste parameters. Second, the finite-sample properties of
VB estimators and the relative performance of VB, MCMC and maximum simulated
likelihood estimation (MSLE) are not known. To address the former, this study
extends several VB methods for MMNL to admit utility specifications including
both fixed and random utility parameters. To address the latter, we conduct an
extensive simulation-based evaluation to benchmark the extended VB methods
against MCMC and MSLE in terms of estimation times, parameter recovery and
predictive accuracy. The results suggest that all VB variants with the
exception of the ones relying on an alternative variational lower bound
constructed with the help of the modified Jensen's inequality perform as well
as MCMC and MSLE at prediction and parameter recovery. In particular, VB with
nonconjugate variational message passing and the delta-method (VB-NCVMP-Delta)
is up to 16 times faster than MCMC and MSLE. Thus, VB-NCVMP-Delta can be an
attractive alternative to MCMC and MSLE for fast, scalable and accurate
estimation of MMNL models
Privacy Mining from IoT-based Smart Homes
Recently, a wide range of smart devices are deployed in a variety of
environments to improve the quality of human life. One of the important
IoT-based applications is smart homes for healthcare, especially for elders.
IoT-based smart homes enable elders' health to be properly monitored and taken
care of. However, elders' privacy might be disclosed from smart homes due to
non-fully protected network communication or other reasons. To demonstrate how
serious this issue is, we introduce in this paper a Privacy Mining Approach
(PMA) to mine privacy from smart homes by conducting a series of deductions and
analyses on sensor datasets generated by smart homes. The experimental results
demonstrate that PMA is able to deduce a global sensor topology for a smart
home and disclose elders' privacy in terms of their house layouts.Comment: This paper, which has 11 pages and 7 figures, has been accepted BWCCA
2018 on 13th August 201
Effects of vitamin e and zinc supplementation on antioxidants in beta thalassemia major patients
Objective: In beta thalassemic patients, tissue damage occurs due to oxidative stress and it happens because of the accumulation of iron in the body. This study was conducted to determine the effect of zinc and vitamin E supplementation on antioxidant status in beta-thalassemic major patients. Methods: This double blind randomized clinical trial was carried out on 120 beta thalassemic patients older than 18 years. Patients were randomly categorized in four groups. Zinc (50mg/day) and vitamin E (400mg/day) supplements were administered for former and latter group, respectively. In the third group both supplements were administered in similar doses. The fourth (control) group received no supplement. The effect of supplementations on serum zinc and vitamin E, superoxide dismutase (SOD), glutathione peroxidase (GPX), total antioxidant capacity (TAC) and body mass index (BMI) were measured at the beginning and the end of the study. Findings: Serum zinc levels in group 1 and 3 were significantly increased (P<0.007 and P<0.005, respectively). Serum vitamin E levels in group 2 and 3 were also increased significantly (P<0.001). Mean GPX activity in group1, 2 and 3 decreased significantly (P<0.015, P<0.032 and P<0.029, respectively). Mean SOD activity and TAC did not show significant change after supplementation. BMI had significant increase in all treated groups (P<0.001). Conclusion: Our results suggest that beta thalassemic patients have enhanced oxidative stress and administration of selective antioxidants may preclude oxidative damage. © 2011 by Pediatrics Center of Excellence, Children's Medical Center, Tehran University of Medical Sciences, All rights reserved
Atomic White-Out: Enabling Atomic Circuitry Through Mechanically Induced Bonding of Single Hydrogen Atoms to a Silicon Surface
We report the mechanically induced formation of a silicon-hydrogen covalent
bond and its application in engineering nanoelectronic devices. We show that
using the tip of a non-contact atomic force microscope (NC-AFM), a single
hydrogen atom could be vertically manipulated. When applying a localized
electronic excitation, a single hydrogen atom is desorbed from the hydrogen
passivated surface and can be transferred to the tip apex as evidenced from a
unique signature in frequency shift curves. In the absence of tunnel electrons
and electric field in the scanning probe microscope junction at 0 V, the
hydrogen atom at the tip apex is brought very close to a silicon dangling bond,
inducing the mechanical formation of a silicon-hydrogen covalent bond and the
passivation of the dangling bond. The functionalized tip was used to
characterize silicon dangling bonds on the hydrogen-silicon surface, was shown
to enhance the scanning tunneling microscope (STM) contrast, and allowed NC-AFM
imaging with atomic and chemical bond contrasts. Through examples, we show the
importance of this atomic scale mechanical manipulation technique in the
engineering of the emerging technology of on-surface dangling bond based
nanoelectronic devices.Comment: 9 pages (including references and Supplementary Section), 8 figures
(5 in the main text, 3 in Supplementary
Late Cenozoic to Present Kinematic of the North to Eastern Iran Orogen: Accommodating Opposite Sense of Fault Blocks Rotation
The opposite-sense fault block rotation across the continental strike-slip faulting plays an important role in accommodating crustal deformation in the north of the East Iran orogen. This research constrains the post-Neogene kinematics of the NW-SE to E-W left-lateral transpressional zones at the northern termination of the N-S striking right-lateral Neh fault system in the East Iran orogen. Using two case studies, we analyzed the NW-SE Birjand splay and the E-W Shekarab transpression zone by analysis of satellite images, structural features, fault geometry and kinematics, GPS (Global Positioning System) velocities, fault- and earthquake-slip stress inversion, and paleomagnetic data. Our results show two distinctive regions of opposite-sense fault block rotations and with different rotation rates. As an asymmetric arc, the Birjand splay displays a transition from the prevailing N-S right lateral shear in the east to NW-SE left lateral transpression in the middle and E-W left lateral shear in the west. In the east, with clockwise fault block rotation, the N-S right lateral faults and the NW-SE oblique left-lateral reverse faults constitute push-ups through the restraining fault bends. In the west, with counterclockwise fault block rotation, the Shekarab transpression zone is associated with the duplex, pop-up, and shear folds. Our suggested kinematic model reveals that the N-S right-lateral shear is consumed on the left-lateral transpressional zones through the vertical axis fault block rotation. This led to an E-W shortening and N-S along-strike lengthening in the East Iran orogen. This research improves our understanding of how opposite fault block rotations accommodate India- and Eurasia-Arabia convergence in the north of the East Iran orogen. The suggested model has implications in the kinematic evolution of intra-plate strike-slip faulting through continental collision tectonics
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