Equation-of-motion/Linear-response Coupled Cluster Methods with an Approximate Treatment on Triples for Singly-excited States with Pronounced Double Excitation Character

In this work,we investigate the performance of various equation-of-motion/linear-response coupled cluster(EOM/LR-CC)methods with an approximate treatment for triples on excitation energies(EEs)by comparing with EOM-CCSDT(SDT=single,double,triple excitations)results.The focus of this work is on singly-excited states with percentages of the single excitation part(R_(1),%)from CC3 between 50%and 80%,i.e.,excited states with a pronounced double excitation character.CC3 is shown to provide EEs that agree well with EOM-CCSDT results for such excited states.Moreover,reliable EEs can be obtained with EOM-CCSD(T)(a)^(*) and CCSDR(3)for excited states with R1 from CC3 larger than 80%.As for singly-excited states with R1 from CC3 between 80%and 50%,EEs with EOM-CCSD^(*),CCSDR(T)andδ-CR-EOM-CC(2,3)-D agree reasonably well with those of EOM-CCSDT.However,it is too costly to choose a proper method for singly-excited states based on R_(1) of CC3 since CC3 is a rather expensive method.On the other hand,our results show that difference between EEs with EOM-CCSD and EOM-CCSD(T)(a)*[ΔE_((T)(a)*)]correlates well with R1 from CC3 andΔE_((T)(a)*)is about 0.25 eV when R_(1)(CC3)is 80%.Appropriate methods to obtain reasonable EEs for singly-excited state can be chosen based on whetherΔE_((T)(a)*)is larger than 0.25 eV.

Vibration analysis of hard-coated composite beam considering the strain dependent characteristic of coating material

The strain dependent characteristics of hard coatings make the vibration analysis of hard-coated composite structure become a challenging task. In this study, the modeling and the analysis method of a hard-coated composite beam was developed considering the strain dependent characteristics of coating material. Firstly, based on analyzing the properties of hard-coating material, a high order polynomial was adopted to characterize the strain dependent characteristics of coating materials. Then, the analytical model of a hard-coated composite beam was created by the energy method. Next, using the numerical method to solve the vibration response and the resonance frequencies of the composite beam, a specific calculation flow was also proposed. Finally,a cantilever beam coated with Mg O ＋ Al2_O_3 hard coating was chosen as the study case; under different excitation levels, the resonance region responses and the resonance frequencies of the composite beam were calculated using the proposed method. The calculation results were compared with the experiment and the linear calculation, and the correctness of the created model was verified. The study shows that compared with the general linear calculation, the proposed method can still maintain an acceptable precision when the excitation level is larger.

Characterization and analysis of coded excitation ultrasound parameters for rock properties

Coded excitation technology （CET） can effectively enhance the penetration and resolution of ultrasonic testing. To analyze the influence of rock properties on pulse compression performance （PCP） of coded excitation signals （CES）, a numerical simulation, and an ultrasonic experiment on different rock samples are performed; and the detection ability of several CESs are also investigated and compared. The results of experiments showed that the loss of the signal-to-noise ratio （SNR） of Barker coded signal with tapered linear frequency modulated carrier （BTLFM） is always less than Barker coded signal with sine carrier （BS）, while the resolution loss of BTLFM is lower than tapered linear frequency modulated signal （TLFM）. In sum, the results not only verifiy the effectiveness of CET, but also provide a basis for the parameter settings of coded signals used in rock ultrasonic testing.