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In this work, an all-fiberized and narrow-linewidth fiber amplifier with record output power and near-diffraction-limited beam quality is presented. Up to 6.12 kW fiber laser with the conversion efficiency of approximately 78.8% is achieved through the fiber amplifier based on a conventional step-index active fiber. At the maximum output power, the 3 dB spectral linewidth is approximately 0.86 nm and the beam quality factor is Mx2 = 1.43, My2 = 1.36. We have also measured and compared the output properties of the fiber amplifier employing different pumping schemes. Notably, the practical power limit of the fiber amplifier could be estimated through the maximum output powers of the fiber amplifier employing unidirectional pumping schemes. Overall, this work could provide a good reference for the optimal design and potential exploration of high-power narrow-linewidth fiber laser systems.
In this article, the development course and current research status of physiological information monitoring equipment are briefly reviewed and analyzed. The research progress of cardiopulmonary resuscitation (CPR) equipment at home and abroad, as well as the advantages and disadvantages of existing CPR equipment, are the main points of discussion. This article discusses the design feasibility and technical points of the portable integrated basic life support machine, based on existing equipment and technology, and summarizes possible interesting future research directions.
This paper investigates the electromechanical behavior of functionally graded piezoelectric composite beams containing axially functionally graded (AFG) beam and piezoelectric actuators subjected to electrical load. The mechanical properties of the AFG beam are assumed to be graded along the axial direction. Employing the electromechanical coupling theory and load simulation method, the expression for the simulation load of the piezoelectric actuators is obtained. Based on Euler-Bernoulli beam theory and the obtained simulation load, the differential governing equation of the piezoelectric composite beams subjected to electrical load is derived. The integration-by-parts approach is utilized to solve the differential governing equation, and the expression for the deflection of the piezoelectric composite beams is obtained. The accuracy of the proposed method is validated by the finite element method. The bending response of the functionally graded piezoelectric composite beams is investigated through the proposed method. In the numerical examples, the effects of electrical load, actuator thickness, AFG beam thickness and AFG beam length on the electromechanical behavior of the functionally graded piezoelectric composite beams are studied.
Molecules such as dithiols are of significant interest for potential molecular electronics applications. To investigate their properties, an efficient method for measuring their electrical conductance is crucial. This research focuses on the time domain measurement, a novel technique capable of measuring hundreds of molecules within a matter of seconds. Measurements were conducted using STM with the tip positioned within tunneling distance over a SAM of 1,8-octanedithiol on Au(111)-mica substrate submerged in toluene. Bonding/debonding events between the tops of molecules and the tip were observed through jumps in the time domain current waveform. A new time-spent histogram data analysis technique was developed to extract conductance values from complex waveforms. Conductance of 2.6 nS was obtained for a single 1,8-octanedithiol molecule, consistent with results obtained from wellestablished but time consuming break junction technique, validating the new STM based time domain technique for fast measurement of molecular conductance.
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