Refractive index of ionic liquids under electric field:Methyl propyl imidazole iodide and several derivatives

Ionic liquids have received wide attention due to their novel optoelectronic structures and devices as an optical means of regulating electricity.However,the quantitative testing and analysis of refractive index of ionic liquids under electric field are rarely carried out.In the present study,an experimental apparatus including a hollow prism is designed to measure the refractive indices of ionic liquids under different electric fields.Five groups of imidazole ionic liquids are experimentally investigated and an inversion is performed to determine the refractive indices under electric fields.The error propagation analysis of the apex angle and the minimum deflection angle are conducted,and the machining accuracy requirements of the hollow prism are determined.The results show that the refractive indices of imidazole ionic liquids change with the light wavelength,following a downward convex parabola.Furthermore,the refractive index decreases with the carbon chain length of ionic liquid at a given wavelength,presenting an order of C3MImI>C4MImI>C5MImI>C3MImBr>C3MImBF4.Notably,the refractive index of imidazole ionic liquid exhibits a nonlinear change with the applied voltage at 546 nm and a monotonical decrease at 1529 nm.Besides,the variation of refractive index at 1529 nm with the applied voltage is larger than that at 546 nm and 1013 nm.Importantly,the variation of refractive index is contrary to that of absorption coefficient under electric field.This study illustrates that the theory of electrode and carrier transport can be used to explain the law of variation of n–k value of ionic liquid under the electric field,and provides the support for the evaluation of physical properties of ionic liquids,the measurement of optical functional parameters and the regulation of electric–optic performances of optical devices.

Light absorption coefficients of ionic liquids under electric field

Ionic liquids have attracted a lot of research attention for their applications in novel optoelectronic structures and devices as an optical means of regulating electricity. Although the electro-optic effect of ionic liquids is mentioned in some literature, quantitative testing and analysis are hardly found in light absorption coefficients of ionic liquids under an electric field. In the present study, an experimental apparatus is designed to measure the absorption coefficients of ionic liquids under different electric fields. Five groups of imidazole ionic liquids are experimentally investigated and an inversion is performed to determine the spectral absorption coefficients of the imidazole ionic liquids under the electric fields. Different intensities with multiple interface refractions and reflections are also considered, and the various measurement errors are analyzed through uncertainties propagation analysis. Spectral absorptions of ionic liquids from 300 nm to 2500 nm are obtained and the absorption coefficients are retrieved. It is found that the absorption behavior of ionic liquids changes in some frequency bands under an applied electric field. The experimental results show that the absorption coefficient of the ionic liquid increases with the voltage increasing at 1520 nm and 1920 nm. The change rate is affected by the types of anions and cations in the ionic liquid and the diffusion rate of the ions therein. This study provides illustrations for the ionic liquid-based electro-optical regulation in terms of physical property parameters and the testing technique.

Search for age pattern across spiral arms of the Milky Way

The age pattern across spiral arms is one of the key observational features utilised to study the dynamic nature of the Galaxy’s spiral structure.With the most updated samples of high-mass star formation region(HMSFR)masers,O stars and open clusters,we investigated their distributions and kinematic properties in the vicinity of the Sun.We found that the Sagittarius-Carina Arm traced by HMSFRs,O stars((?)10 Myr)and young open clusters(<30 Myr)seem to deviate gradually towards the Galactic Anticenter(GAC)direction.The Local Arm traced by HMSFRs,O stars,young clusters and also mediumyoung clusters(30-100 Myr)are inclined to gradually deviate toward the Galactic Center(GC)direction.The properties for the Local Arm are supported by a simplified simulation of cluster motions in the Galaxy.Indications of systematic motions in the circular and radial velocities are noticed for the old open clusters(>200 Myr).These results are consistent with the idea that star formation can be triggered by spiral shocks of density waves,and indicate that the corotation radius of the Galaxy is located between the SagittariusCarina Arm and the Local Arm,close to the Solar circle.

A catalogue of 74 new open clusters found in Gaia Data-Release 2

Based on astrometric data from Gaia Data-Release 2(DR2),we employ an unsupervised machine learning method to blindly search for open star clusters in the Milky Way within the Galactic latitude range of|b|<20°.In addition to 2080 known clusters,74 new open cluster candidates are found.In this work,we present the positions,apparent radii,parallaxes,proper motions and member stars of these candidates.Meanwhile,to obtain the physical parameters of each candidate cluster,stellar isochrones are fit to the photometric data.The results show that the apparent radii and the observed proper motion dispersions of these new candidates are consistent with those of open clusters previously identified in Gaia DR2.

Super Edge-connectivity and Zeroth-order General Randi Index for -1≤α< 0

Let G be a connected graph with order n,minimum degree δ = δ（G） and edge-connectivity λ =λ（G）. A graph G is maximally edge-connected if λ = δ, and super edge-connected if every minimum edgecut consists of edges incident with a vertex of minimum degree. Define the zeroth-order general Randic index R_α-0（G） =Σ x∈V（G） d_G-α（x）, where dG（x） denotes the degree of the vertex x. In this paper, we present two sufficient conditions for graphs and triangle-free graphs to be super edge-connected in terms of the zeroth-order general Randic index for -1 ≤α 〈 0, respectively.

Super-Edge-Connectivity and Zeroth-Order Randi´c Index

Define the zeroth-order Randic index R^(0)(G)=∑x∈V(G)1/√dG1(x),where dG(x)denotes the degree of the vertex x.In this paper,we present two sufficient conditions for graphs and triangle-free graphs to be super-edge-connected in terms of the zeroth-order Randic index,respectively.

Componentwise Complementary Cycles in Multipartite Tournaments

The problem of complementary cycles in tournaments and bipartite tournaments was completely solved. However, the problem of complementary cycles in semicomplete n-partite digraphs with n 〉 3 is still open. Based on the definition of componentwise complementary cycles, we get the following result. Let D be a 2-strong n-partite （n 〉 6） tournament that is not a tournament. Let C be a 3-cycle of D and D ／ V（C） be nonstrong. For the unique acyclic sequence D1, D2,..., Da of D ／ V（C）, where a 〉 2, let Dc = {Di｜Di contains cycles, i = 1,2,...,a}, Dc = {D1,D2,...,Da} ／ De. If Dc≠ 0, then D contains a pair of componentwise complementary cycles.