Far-infrared optical properties of the pyrochlore spin ice compound Dy2Ti2O4

Near normal incident far-infrared reflectivity spectra of [111] dysprosium titanate (Dy2Ti2O4) single crystal have been measured at different temperatures. Seven phonon modes (eight at low temperature) are identified at frequency below 1000 cm-1. Optical conductivity spectra are obtained by fitting all the reflectivity spectra with the factorized form of the dielectric function. Both the Born effective charges and the static optical primitivity are found to increase with decreasing temperature. Moreover, phonon linewidth narrowering and phonon modes shift with decreasing temperature are also observed, which may result from enhanced charge localization. The redshift of several low frequency modes is attributed to the spin-phonon coupling. All observed optical properties can be explained within the framework of nearest neighbor ferromagnetic(FM) spin ice model

Defining and Testing a Safety Cognition Framework Incorporating Safety Hazard Perception

This material may be downloaded for personal use only. Any other use requires prior permission of the American Society of Civil Engineers. This material may be found at https://ascelibrary.org/doi/10.1061/%28ASCE%29CO.1943-7862.0001718 There has been insufficient research focusing on checking the reliability of construction employees’ hazard perceptions by comparing them with empirical safety data. There have also been limited studies focusing on how site employees’ perceptions could be affected by multiple external and internal factors such as workers’ experience levels

Hierarchical Learning for Cognitive End-to-End Service Provisioning in Multi-Domain Autonomous Optical Networks

This paper demonstrates, for the first time to our knowledge, hierarchical learning framework for inter-domain service provisioning in software-defined elastic optical networking (EON). By using a broker-based hierarchical architecture, the broker collaborates with the domain managers to realize efficient global service provisioning without violating the privacy constrains of each domain. In the proposed hierarchical learning scheme, machine learning-based cognition agents exist in the domain managers as well as in the broker. The proposed system is experimentally demonstrated on a two-domain seven-node EON testbed for with real-time optical performance monitors (OPMs). By using over 42000 datasets collected from OPM units, the cognition agents can be trained to accurately infer the Q-factor of an unestablished or established lightpath, enabling an impairment-aware end-to-end service provisioning with an prediction Q-factor deviation less than 0.6 dB

Synthesis, properties and applications of 2D layered MIIIXVI (M = Ga, In; X = S, Se, Te) materials

Group III-VI compounds MIIIXVI (M = Ga, In; X = S, Se, Te) are one class of important 2D layered materials and are currently attracting increasing interest due to their unique electronic and optoelectronic properties and their great potential applications in various other fields. Similar to 2D layered transition metal dichalcogenides (TMDs), MIIIXVI also have the significant merits of ultrathin thickness, ultrahigh surface-to-volume ratio, and high compatibility with flexible devices. More impressively, in contrast with TMDCs, MIIIXVI demonstrate many superior properties, such as direct band gap electronic structure, high carrier mobility, rare p-type electronic behaviors, high charge density, and so on. These unique characteristics cause high-performance device applications in electronics, optoelectronics, and optics. In this review, we aim to provide a summary of the state-of-the-art of research activities in 2D layered MIIIXVI materials. The scope of the review covers the synthesis and properties of 2D layered MIIIXVI materials and their van der Waals heterostructures. We especially focus on the applications in electronics and optoelectronics. Moreover, the review concludes with some perspectives on future developments in this field

Effective Field Theory of the Zero-Temperature Triangular-Lattice Antiferromagnet: A Monte Carlo Study

Using a Monte Carlo coarse-graining technique introduced by Binder et al., we have explicitly constructed the continuum field theory for the zero-temperature triangular Ising antiferromagnet. We verify the conjecture that this is a gaussian theory of the height variable in the interface representation of the spin model. We also measure the height-height correlation function and deduce the stiffness constant. In addition, we investigate the nature of defect-defect interactions at finite temperatures, and find that the two-dimensional Coulomb gas scenario applies at low temperatures.Comment: 26 pages, 9 figure

Ultrafast and ultrasensitive phototransistors based on few-layered HfSe2

Two-dimensional layered materials have exhibited great potential in electronic and optoelectronic applications, because of their unique chemical and physical properties. Recently, Hf-based transition metal dichalcogenides are predicted to own high room temperature mobility and are attracting increasing interest. However, only few experimental investigations are reported hitherto. In this paper, we demonstrate ultrafast and ultrasensitive back-gated HfSe2 phototransistors. Au-contacted HfSe2 phototransistors display a high on/off ratio of 106 and modest mobilities in the range of 2.6-6.5 cm2 V-1 s-1. Additionally, the phototransistors based on HfSe2 present prominent optoelectronic performance with a high responsivity of 252 A/W and an ultrafast response time of 7.8 ms, implying the sensitive photoswitching behavior. Moreover, the response time can be modulated by gate voltages. The excellent field effect transistor performance coupled to the sensitive and fast photodetection makes HfSe2 have a broad application prospect for electronic and optoelectronic devices in the future