Accurate assignment of double resonant Raman bands in Janus MoSSe monolayer from first-principles calculations

Janus transition metal dichalcogenides(TMDs)structures,as a new type of two-dimensional layered materials,have drawn increasing research efforts mostly by the Raman characterization technique since their successful synthesis.First-and second-order resonant Raman spectra(RRS)have been reported by experiments.But,unlike much interest paid to the first-order RRS,there has been so far no much discussion dedicated to the second-order double resonant Raman(DRR)bands and band assignments of Janus TMDs,which nevertheless is indispensable but hampered by the difficulty of calculations.In this work,we calculate the DRR spectra of Janus Mo SSe monolayer within the first-principles framework and succeed in achieving accurate assignments of the DRR bands.The assignments are in agreement with our group theoretical analysis.Moreover,taking advantage of its strain-sensitive feature,we calculate the DRR spectra under biaxial strain,and further verify the rationality of our assignments by analyzing strain-induced shift of the DRR bands.Our present study supplies an efficient strategy for quantitative understanding on the electron-phonon coupling in the Janus structures.

Performance characteristics of an energy selective electron refrigerator with double resonances

This paper establishes the energy selective electron （ESE） engine with double resonances as a refrigerator in one dimensional （1D） system. It consists of two infinitely large electron reservoirs with different temperatures and chemical potentials, and they are perfectly thermally insulated from each other and interaction only via a double ＇idealized energy filter＇ whose widths are all finite. Taking advantage of the density of state and Fermi distribution in the 1D system, the heat flux into each reservoir may then be calculated. Moreover, the coefficient of performance may be derived from the expressions for the heat flux into the hot and cold reservoirs. The performance characteristic curves are plotted by numerical analysis. The influences of the resonances widths, the energy position of resonance and the space of two resonances on performance of the ESE refrigerator are discussed. The results obtained here have theoretical significance for the understanding of thermodynamic performance of the micro-nano devices.

Quantum fluctuations of mesoscopic damped double resonance RLC circuit with mutual capacitance-inductance coupling

Based on the scheme of damped harmonic oscillator quantization and thermo-field dynamics （TFD）, the quantization of mesoscopic damped double resonance RLC circuit with mutual capacitance-inductance coupling is proposed. The quantum fluctuations of charge and current of each loop in a squeezed vacuum state are studied in the thermal excitation case. It is shown that the fluctuations not only depend on circuit inherent parameters, but also rely on excitation quantum number and squeezing parameter. Moreover, due to the finite environmental temperature and damped resistance, the fluctuations increase with the temperature rising, and decay with time.

Entropic noise induced stability and double entropic stochastic resonance induced by correlated noises

For the activated dynamics of a Brownian particle moving in a confined system with the presence of entropic barriers, this paper investigates a periodic driving and correlations between two noises. Within the two-state approximation, the explicit expressions of the mean first passage time （MFPT） and the spectral power amplification （SPA） axe obtained, respectively. Based on the numerical computations, it is found that： （i） The MFPT as a function of the noise intensity exhibits a maximum with the positive correlations between two noises （λ〉0）, this maximum for MFPT shows the characteristic of the entropic noise induced stability （ENIS） effect. The intensity A of correlations between two noises can enhance the ENIS effect. （ii） The SPA as a function of the noise intensity exhibits a double-peak by tuning the noise correlation intensity λ, i.e., the existence of a double-peak behaviour is the identifying characteristic of the double entropic stochastic resonance phenomenon.

THE DOUBLE RESONANCES OF MAGNETISM AND SOLID COUPLING OF HYDROELECTRIC-GENERATOR STATOR SYSTEM

A double-shell model of hydroelectric-generator stator system was established. Applying the theory of mechano-electric analytical dynamics theory, the nonlinear vibration equation of magnetism and solid coupling of hydroelectric-generator stator system, under steadily balanced three-phases operating condition, was obtained. According to the method of multiple scales for nonlinear oscillations, the double resonances of magnetism and solid coupling of hydroelectric-generator stater system, were investigated. It is pointed out that the system has abundant dynamics phenomenon including the attendant jumps and coexistence of multiple stable motions.

Experimental Study on Double Resonance Optical Pumping Spectroscopy in a Ladder-Type System of ^(87)Rb Atoms

Double resonance optical pumping spectroscopy has an outstanding advantage of high signal-to-noise ratio, thus having potential applications in precision measurement. With the counter propagated 780nm and 776nm laser beams acting on a rubidium vapor cell, the high resolution spectrum of 5S1/2 - 5P3/2 - 5D5/2 ladder-type transition of ST Rb atoms is obtained by monitoring the population of the 5S1/2 ground state. The dependence of the spectroscopy lineshape on the probe and coupling fields are comprehensively studied in theory and experiment. This research is helpful for measurement of fundamental physical constants by high resolution spectroscopy.

Endovascular Application of Magnetic Resonance Double Mismatch Technique for Acute Anterior Circulation Large Vessel Occlusion with Cerebral Infarction in an Unknown Time Window

Objective:To investigate the clinical effects of applying the magnetic resonance double mismatch technique to endovascular treatment of acute anterior circulation,large vessel occlusion with cerebral infarction in an unknown time window.Methods:The research work was carried out in our hospital,the work was carried out from November 2018 to November 2019,the patients with acute anterior circulation large vessel occlusion with cerebral infarction who were treated in our hospital during this period,100 patients,50 patients with an unknown time window and 50 patients with definite time window were selected,and they were named as the experimental and control groups,given different examination methods,were given to investigate the clinical treatment effect.Results:Patients’data on HIHSS score before treatment,the incidence of intracranial hemorrhage and rate of Mrs≤2 rating after 90 days of treatment were not significantly different(P>0.05),which was not meaningful.The differences in data between the two groups concerning HIHSS scores were relatively significant before,and after treatment(P<0.05).Conclusion:The magnetic resonance double mismatch technique will be applied in the endovascular treatment of acute anterior circulation large vessel occlusion with cerebral infarction of unknown time window.

Interpretation method of nuclear magnetic resonance dual-TW logging in oil-wet tight sandstone reservoirs

Fluid typing from nuclear magnetic resonance(NMR)logging in oil-wet tight sandstone reservoirs is proving to be diffi cult;thus,research into the NMR logging response mechanism and analysis methods is critical.The NMR response mechanism and theoretical method were investigated based on the oil-water distribution in the pores under oil-wet conditions.The data processing method is studied based on NMR dual-TW activation principle,and the equations of macroscopic magnetization vector,fl uid volume,and relaxation parameters are derived,which is a nonlinear inversion problem.The simulated annealing algorithm is used,and the fl uid relaxation parameters,oil volume,and water volume of the fl ushing zone are calculated.An ideal reservoir model is set up,and simulation results indicate that the above-mentioned NMR relaxation theory and algorithms are valid.A case study is conducted in Huanjiang Oilfi eld in the Ordos Basin,China.The calculated oil saturation of the fl ushing zone is consistent with the oil saturation calculated using the Archie formula,and the test results indicated that the new method is applicable.Moreover,the fl uid-typing cross-plot combined with oil test data is constructed on the basis of the saturation of the fl ushing zone,improving the accuracy of fl uid identifi cation.

Single-Mode Fabry-Pérot Quantum Cascade Lasers at λ ~10.5 μm

In this paper, we report a single-mode Fabry-Pérot long wave infrared quantum cascade lasers based on the double phonon resonance active region design. For room temperature CW operation, the wafer with 35 stages was processed into buried heterostructure lasers. For a 4 mm long and 13 μm wide laser with high-reflectivity (HR) coating on the rear facet, continuous wave output power of 43 mW at 288 K and 5 mW at 303 K is obtained with threshold current densities of 2.17 and 2.7 kA/cm2. The lasing wavelength is around 10.5 μm. Single mode emission was observed for this particular device over the whole investigated current and temperature range.

EPR and DFT Study of the Polycyclic Aromatic Radical Cations from Friedel-Crafts Alkylation Reactions

Electron paramagnetic resonance and electron-nuclear double resonance methods were used to study the polycyclic aromatic radical cations produced in a Friedel-Crafts alkylating sys- tem, with m-xylene, or p-xylene and alkyl chloride. The results indicate that the observed electron paramagnetic resonance spectra are due to polycyclic aromatic radicals formed from the parent hydrocarbons. It is suggested that benzyl halides produced in the Friedel-Crafts alkylation reactions undergo Scholl self-condensation to give polycyclic aromatic hydrocar- bons, which are converted into corresponding polycyclic aromatic radical cations in the presence of AlCl3. The identification of observed two radicals 2,6-dimethylanthracene and 1,4,5,8-tetramethylanthraeene were supported by density functional theory calculations using the B3LYP/6-31G（d,p）//B3LYP/6-31G（d） approach. The theoretical coupling constants support the experimental assignment of the observed radicals.

2.32W anti-misaligned Er:LuAG single-longitudinal-mode laser in the double corner-cube-retroreflector resonator and MOPA system

We demonstrate a high power,Er:Lu AG single-longitudinal-mode laser in an anti-misaligned resonator.Based on the Faraday effect,a 1.61 W single-longitudinal-mode(SLM)laser is obtained with the double corner-cube-retroreflector(CCR)structure,and the tunable wavelength is 1649.2-1650.3 nm.Additionally,we investigate the anti-misalignment characteristics when the CCR moves and rotates along the optical axis.Furthermore,by utilizing the Er:Lu AG amplifier,the maximum 2.32 W single-longitudinal-mode laser at 1649.6 nm is achieved.The beam quality factors M^(2) of the 2.32 W Er:Lu AG single-longitudinal-mode laser are 1.23 and 1.25 along the horizontal(x)and vertical(y)directions,respectively.

Collisional broadening of some 2~1Δ_g←B^1Π_u lines in Na_2 molecules by optical-optical double resonance spectroscopy

Using the optical-optical double resonance （OODR） technique, we have studied the collisional broadening of some 21△g←B1πu lines in Na2 molecules. A single line Ar＋ laser is used to pump the sodium dimers from thermally populated ground state X^1∑^＋g level to the intermediate B1πu state. Then, a single-mode diode laser is used to probe the doubly excited 21△g state. The broadening rate coefficient is determined from the slope of the total linewidth versus Ne density curve. We obtain the average value kbr = （1.1 ± 0.5）×10^-8 cm^3 8^-1. The collisional excitation transfer between rotational levels of the B1πu state （i.e.,B1πu（2,83/84） ←B1Ⅱu （2,82）） is also investigated. The rates can be determined from the relative intensities of the main peak and satellite lines, combined with a rate equation model. The rates of 1.25 × 106 and 1.07 × 106 s^-1 are obtained, respectively.

Electromagnetic Properties of a New Microwave Plasma Torch with Double Resonance Configuration

In order to obtain a stable plasma and improve the performance of the torch for atomic emission spectroscopy（AES）, the structure of microwave plasma torch（MPT） was analyzed. The transmission and distribution characteristics of the electromagnetic field of the torch configuration with two or three concentric tubes, as well as the metal spacer between inner and intermediate tubes with different depths were simulated with electromagnetic simula- tion software and verified by experiments. The results indicate that the inner tube of MPT plays an important role in strengthening the electric field intensity at the opening end of the MPT and redistributing the electromagnetic field in the whole torch by forming a double resonance configuration, and contributes to enhancing the macroscopic stability and the self-sustainment of the plasma. The stability of the plasma is proved to be excellent when the metal spacer between the inner and intermediate tubes is located at a place 20-30 mm away from the top opening of the torch. A proper location of the spacer can also avoid the formation of a static filament plasma or a rotating plasma rooted from the outer wall of the inner tube. With the help of morphological analysis, the underlying reason why MPT possesses a great tolerance to wet aerosols and air introduction was clearly made, that is, the formation region of the plasma formed with MPT is apparently separated from the reaction zone of it.

A Semilinear Elliptic Equation with Double Resonance

In this paper, the existence and multiplicity of a class of double resonant semilineax elliptic equations with the Dirichlet boundary value axe studied.

Fano profile in a novel double cavity optomechanical system with harmonically bound mirrors

We investigate a double cavity optomechanical system generating single and double Fano resonance(multi-Fano). By altering a single parameter, the tunnelling rate g of the middle mirror, we are able to switch between single and double Fano line shapes. The first spectral line shape is stronger in the case of multi-Fano than in the case of single Fano. Also the behaviour of the steady state value of the displacement of the middle mirror, with respect to g, heavily influences the behaviour of double Fano lines in our scheme. This tunability along with using a single pump and signal/probe laser has an added advantage in situations where only low power consumption is available.

Doubly resonant second-harmonic generation in a fiber-based tunable open microcavity

Microcavities constructed from materials with a second-order nonlinear coefficient have enabled efficient second-harmonic(SH)generation at a low power level.However,it is still technically challenging to realize double resonance with large nonlinear modal overlap in a microcavity.Here,we propose a design for a robust,tunable,and easy coupling double-resonance SH generation based on the combination of a newly developed fiber-based Fabry-Perot microcavity and a sandwich structure,whose numerical SH conversion efficiency is up to 3000%W^(-1).This proposal provides a feasible way to construct ultra-efficient nonlinear devices for generation of classical and quantum light sources.

Influencing factors of the dynamic hysteresis in varying compliance vibrations of a ball bearing

We focus on the hysteretic characteristics of the varying compliance(VC) principal resonance in a ball bearing. The branches of the periodic VC response are traced by the harmonic balance method and the alternating frequency/time domain technique(HB-AFT) embedding Arc-length continuation, and the stability of these solutions is investigated by using Floquet theory. We find that the resonant response displays a swallow-tail structure due to the coupling nonlinearities between the Hertzian contact and the bearing clearance, which differs from the soft hysteresis of the non-loss Hertzian contact resonances. Furthermore, we find that period-1 VC branch cannot completely characterize the response of the system for a large bearing clearance, because multiple instability regions may occur from the cyclic fold, the secondary Hopf bifurcations, supercritical and subcritical period doubling bifurcations, in which case co-existences of period-1, period-2, and even quasi-periodic VC motions emerge in the hysteretic resonant range.

33 W continuous-wave single-frequency green laser by frequency doubling of a single-mode YDFA

A high power continuous-wave single-frequency green fiber laser by second-harmonic generation of a Yb-doped fiber amplifier（YDFA）is developed.A linearly polarized single-mode fiber amplifier produces a 60 W infrared laser at 1064 nm with a 103 W incident diode pump laser at 976 nm,corresponding to an optical conversion efficiency of 58%.An external bow-tie enhancement cavity incorporating a noncritically phase-matched lithium triborate crystal is employed for second-harmonic generation.A 33.2 W laser at 532 nm is obtained with a 45 W incident 1064 nm fundamental laser,corresponding to a conversion efficiency of 74%.