Markov random field or undirected graphical models (GM) are a popular class of GM useful in various fields because they provide an intuitive and interpretable graph expressing the complex relationship between random variables.The zero-inflated local Poisson graphical model has been proposed as a graphical model for count data with excess zeros. However, as count data are often characterized by over-dispersion, the local Poisson graphical model may suffer from a poor fit to data. In this paper, we propose a zero-inflated local negative binomial (NB) graphical model. Due to the dependencies of parameters in our models, a direct optimization of the objective function is difficult. Instead, we devise expectation-minimization algorithms based on two different parametrizations for the NB distribution. Through a simulation study, we illustrate the effectiveness of our method for learning network structure from over-dispersed count data with excess zeros. We further apply our method to real data to estimate its network structure.
Hybrid 2D/0D structures with various 2D materials and 0D quantum dots (QDs) have been studied to overcome the limitations of 2D materials. We develop a hybrid structure with MoS2 and silicon quantum dots (Si QDs) as a photodetector. I‐V transfer characteristics show the threshold voltage shift after decorating Si QDs on MoS2, which results from n‐type doping effect to the MoS2 channel from Si QDs. The field‐effect mobility of the MoS2/Si QDs device is increased by ∽5.8 times compared with that of the bare MoS2 device. We understand that the mobility enhancement is attributed to the surface defect passivation of MoS2 at the interface with Si QDs. We observe that the photoresponsivity of the structure MoS2/Si QDs was improved by ∽7.7 times compared with that of the bare MoS2 device under 500 nm illumination. Additionally, we observe that the photoluminescence (PL) intensity of MoS2 is increased about 4.5 times after decoration of Si QDs. We interpret the band alignment as the type I at the interface between Si QDs and MoS2. The mobility enhancement and the photoexcited charge transfer (CT) between MoS2 and Si QDs due to the illumination lead to enhancing the photoresponsivity of the MoS2/Si QDs hybrid structure.This article is protected by copyright. All rights reserved.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.