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Crankshaft is one of the most important parts in modern diesel engine. Usually, the strength of this part is improved by the electromagnetic induction quenching approach. In this paper, the high cycle bending fatigue property of the steel crankshaft after this treatment was selected as the object of study. First, a simplified 2D finite element model was built based on the structural features of the crankshaft to simulate the electromagnetic induction quenching process of a given type of steel crankshaft. In this way, the temperature and residual stress distribution property of the crankshaft can be determined at any time node during the process. Then the fatigue limit load of this crankshaft was predicted based on the results obtained in the previous chapter and the selected mean stress models. Finally, corresponding experimental verifications were conducted to check the accuracy of the predictions. Validations between the experimental results and the prediction showed that this that the combination of the simulation results and the Gerber mean stress model can obtain the fatigue property of this type of crankshaft accurately, thus was suitable for actual engineering applications.

In recent years, 1.3 μm lasers have been widely used in laser medical treatment, optical fiber communication and optoelectronic countermeasures, etc. In this paper, the unstable cavity structure with double pump cavity connected in series and the method to optimize the thermal lens effect are used to obtain a maximum 41 W average power of continuous-wave laser. Meanwhile, the pulsed laser is realized through an acousto-optic Q switch and the repetition rate can be adjusted in the range of 1~10 kHz. The maximum single pulse energy can reach 8.44 mJ with the repetition frequency of 1 kHz, corresponding to 65 kW peak power. In the future, the output power will be further improved by optimizing the laser, which will be beneficial to expand the applications in related fields.

Two dimensional materials have been regarded as promising candidates for photocatalytic water splitting. Herein, we systematically investigated the potential of a novel two dimensional penta-X2C (X = P, As, Sb) family for photocatalytic water splitting by means of density functional theory. The penta-X2C family consists of semiconductors with indirect band gaps of 2.64 eV, 2.09 eV and 1.35 eV for X = P, As and Sb, respectively. Notably, the band edge positions of penta-P2C and penta-As2C can perfectly satisfy the redox potentials of photocatalytic water splitting via strain engineering, whereas penta-Sb2C only meets the reduction potential. The ultrahigh (up to 103–105 cm2 V−1 s−1) and anisotropic carrier mobilities are crucial to suppressing the photogenerated electron-hole pair recombination. Meanwhile, the penta-X2C family exhibits excellent light absorption in the visible-ultraviolet region, favorable for the utilization of sunlight. In addition, compared with other common 2D materials such as graphene and h-BN, the penta-X2C family possesses a relatively smaller Young's modulus and larger critical strain, while penta-X2C have large negative Poisson's ratios of −0.103, −0.079 and −0.077, respectively. These results testify that the penta-X2C family has potential applications not only in photocatalytic water splitting but also in designing 2D electromechanical and optoelectronic devices.

Based on an all-fiber master oscillator power amplifier (MOPA) structure, a 1950-nm narrow-linewidth, single-mode, high peak power nanosecond pulsed fiber laser was developed. The seed source is a distributed feedback (DFB) semiconductor laser with a linewidth of 0.5 MHz. A precise and stable closed-loop temperature control technology is used to design the driving circuit of the seed laser, which ensures the stability of the laser wavelength and power, and greatly reduces the frequency and intensity noise of the laser. The continuous seed laser is modulated by an acousto-optic modulator (AOM). At the same time, the high-frequency control technology of acousto-optic modulator and cascade amplification technology are used to realize the continuous adjustable of laser pulse shape (Gaussian pulse or square wave pulse), repetition rate (1 kHz ~ 300 kHz) and pulse width (50 ns ~ 500 ns) of 2.0 μm band single frequency laser. This laser is very suitable for coherent lidar applications

We report a high-energy narrow-linewidth SBS-free high-efficiency polarization-maintaining fiber laser based on MOPA at 1572 nm for CO2 coherent remote sensing. The Lorentz linewidth of the seed laser is 150 μJ, with tunable repetition rate of 1 k~1 MHz and tunable pulse width of 100~500 ns.

The groundbreaking works in graphene and graphene nanoribbons (GNRs) over the past decade, and the recent discovery of borophene draw immediate attention to the underexplored borophene nanoribbons (BNRs). We herein report a density functional theory (DFT) study of the geometric, electronic and magnetic properties of BNRs as a function of orientation (denoted as BxNRs and ByNRs with the orientation along x- and y-axis, respectively), ribbon width (Nx, Ny = 4 to 15), and hydrogenation effects. We found that the anisotropic quasi-planar geometric structure of BNRand its edge states profoundly govern the electronic and magnetic properties. Pristine ByNRs adopt a magnetic ground state, anti-ferromagnetic (AFM) or ferromagnetic (FM) depending on the ribbon width, while pristine BxNRs are non-magnetic (NM). Upon hydrogenation, all BNRs become NM. Interestingly, both pristine and hydrogenated ByNRs undergo a metal-semiconductor-metal transition at Ny = 7, while BxNRs remain metallic., Comment: 33 pages, 9 figures

Linewidth measurement of single-frequency laser using self-heterodyne method is studied. 1/f noise and the noise caused by double Rayleigh scattering in delayed fiber can affect the shape of linewidth, which introduces inaccuracy in linewidth measurement.

A dual-wavelength, all-fiber, passively Q-switched Erbium laser based on a SWNT saturable absorber is demonstrated, which can simultaneously generate ~μs pulses with ~kHz repetition rate at 1532 nm and 1558 nm wavelength.

Several important characteristics of the magnetic-field-enhanced terahertz radiation from InAs and InSb emitters pumped at 1550?nm wavelength are experimentally investigated. The emission efficiency, pump saturation power and emission spectrum from these two different materials are compared side by side. With the external magnetic field, while the InSb crystal shows a higher THz emission efficiency, it has a lower saturation pump power (0.42??J?cm?2) than that of InAs (0.86??J?cm?2). They are shown to be much easier to saturate compared to the InAs emitter pumped at 800?nm reported previously. The THz spectrum from InAs has a broader bandwidth than that of InSb, and its shape also varies significantly under higher pump powers with an interesting increase at frequencies above 1?THz. The results could be very helpful in designing and implementing compact, high-efficiency THz sources using low-cost, high-power fiber ultrafast lasers.