In this paper, the eigenvalue problem that involves uncertain-but-non-random parameters is discussed. The error of dynamical parameters of a system is unavoidable in the course of manufacture and installation. Eigenvalues of the system are hard to obtain by the traditional dynamical theory. A new method based on matrix inequality theory is developed to evaluate the upper and lower bounds of the eigenvalues. In this method, properties of matrix’s spectral radius and norm are used. The illustrative numerical examples are provided to demonstrate the validity of the method. Compared with the other methods, the calculated results show that the proposed method in this paper is effective in evaluating bounds of the eigenvalues of structures with uncertain-but-bounded parameters.
Soliton microcombs are regarded as an ideal platform for applications such as optical communications, optical sensing, low-noise microwave sources, optical atomic clocks, and frequency synthesizers. Many of these applications require a broad comb spectrum that covers an octave, essential for implementing the f - 2f self-referencing techniques. In this work, we have successfully generated an octave-spanning soliton microcomb based on a z-cut thin-film lithium niobate (TFLN) microresonator. This achievement is realized under on-chip optical pumping at 340 mW and through extensive research into the broadening of dual dispersive waves (DWs). Furthermore, the repetition rate of the octave soliton microcomb is accurately measured using an electro-optic comb generated by an x-cut TFLN racetrack microresonator. Our results represent a crucial step toward the realization of practical, integrated, and fully stabilized soliton microcomb systems based on TFLN.
This paper establishes a simulation model for new type full bridge PWM controller UCC3895 with PSpice library.Furthermore,it incorporates the controller UCC3895 into the FB-ZVS-PWM converter,and simulates the soft-start,OC-protection,closed-loop performance and MOSFET ZVS for the whole switching power supply system,and the simulation results are presented.The simulation method is not only of some guiding significance for the engineering design of SMPS but is a useful supplement for the experimental study.
Abstract Thin‐film lithium niobate (TFLN) enables extremely high‐efficiency second‐order nonlinear optical effects due to large nonlinear coefficient d 33 and strong optical field confinement. Here, a pulley‐waveguide‐coupled microring resonator with an intrinsic quality factor above 9.4 × 10 5 on the reverse‐polarized double‐layer X‐cut TFLN is designed and fabricated. In such a TFLN resonator without fine domain structures, second harmonic generation with a normalized conversion efficiency of 440,000% W −1 with weak pump power, approaching that in periodically poled lithium niobate (PPLN) microring resonators, and an absolute conversion efficiency of 30% is realized with a sub‐milliwatt continuous pump. This work reduces the dependence of high‐efficiency nonlinear frequency conversion on PPLN microcavities that are difficult to prepare.
The rheological dynamics for the formation of clear fracturing fiuids of viscoelastic micelles were investigated. The rheological dynamics model and equations were established firstly, and was applied to simulate the formation of clear viscoelastic micelles fracturing fluids. The results show that, the rheological dynamics equation can be applied to describe the formation of viscoelastic micelle system correctly, the calculated data are in good agreement with the experimental data, and the meanings of the model parameters are clear and reasonable.
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