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Lithium supply shortages have prompted the search for alternatives to widespread grid system applications. Potassium-ion batteries (PIBs) have emerged to promising candidates for this purpose. Nonetheless, the large radius of K+ (1.38 Å) impedes the march of satisfactory cathode materials. Here, we used solid-phase synthesis to prepare a layered K0.37MnO2·0.25H2O (KMO) cathode, comprising alternately connected MnO6 octahedra with a large interlayer spacing (0.71 nm) to accommodate the migration and transport of K+ ions. The cathode material achieved initial specific capacities of 102.3 and 88.1 mA h g−1 at current densities of 60 mA g−1 and 1 A g−1, respectively. The storage mechanism of K+ ions in PIBs was demonstrated ex situ using x-ray diffraction, x-ray photoelectron spectroscopy, and Raman spectroscopy measurements. Overall, our proposed KMO was confirmed as an auspicious cathode material for potential use in PIBs.

As an important parameter for quenching and simulation, the interfacial heat transfer coefficient (IHTC) is hard to be directly measured through experiments. Researchers have come up with different methods to solve the problem. Currently, the numerical method, the heat balance method (HBM), the Beck’s non-linear estimation method (BEM), and the lumped heat capacity method (LCM) are the main methods of calculating the IHTC. In this paper, the direct heat conduction problem and the solution are firstly analysed, then the solutions and applications of different methods for calculating IHTC are summarized and reviewed. The different methods are compared at the end of the paper.

The HT-6M tokamak at the Thailand Institute of Nuclear Technology has been restarted. In order to ensure the smooth breakdown of plasma and obtain plasma discharge parameters, optimization of the poloidal field coils and upgrade of the magnetic diagnostics are described in this article. A perfect null field (stray field in the main chamber < 10 G) is obtained using an ohmic heating field. To obtain important information about the plasma, an external magnetic diagnostics system is designed and calibrated, including a Rogowski coil (measuring plasma current), a magnetic probe (measuring external field), diamagnetic loops (measuring β p) and so on. In order to realize high-frequency signal measurement and transmission, a series of frequency responses with the magnetic probe and transmission line are tested. Later, to verify the null field, a fitting code is developed to reconstruct the stray field in the vacuum chamber based on magnetic probe measurements and flux loops. The results show that the error is within 1.5%. This indicates the accuracy of the magnetic measurement system and ensures the preparation for the breakdown of plasma.

Owing to the influence of sampling loss, cavity difference and detecting source, the multi-optical parameter measurement of atmospheric aerosol cannot be detected simultaneously in the same reference environment. In order to solve this problem, a new method of simultaneously detecting the aerosol optical parameters by coupling cavity ring-down spectrometer with photoacoustic spectroscopy is proposed. Firstly, the coupled photoacoustic cavity is formed by the organic fusion of the photoacoustic cavity and the ring-down cavity. Secondly, the integrated design of the coupling spectroscopy system is carried out. Finally, the extinction coefficient and absorption coefficient of aerosol are measured simultaneously by the system, and then the aerosol scattering coefficient and single albedo are calculated indirectly. The accuracy of the system is verified by comparing with the data from the environmental quality monitoring station, which provides a new idea for the detection of multi-optical characteristics of atmospheric aerosol.

The indirect boundary element method (IBEM) is adopted to solve the 2D scattering problem of circular underground lining tunnels near canyons and slopes to the P-wave. The numerical results show that the canyon and slope topography near the underground lining tunnel has an evident influence on the surface displacement. The horizontal displacement amplification reaches nearly two times. The presence of slopes has a shielding effect on the nearby underground tunnels. The stress concentration exists at the top and bottom of the arch of the lining tunnel. The dynamic interaction between the slope and the tunnel should be considered when building a tunnel close to the slope.

In this paper, based on the finite element software, the residual stress of the structure weld is obtained through simulation analysis. The influence of stress concentration is considered by using the mean square stress concentration factor; and the S-N curve equation of the structure is derived. then, the stress power spectrum density of dangerous parts is obtained by random response analysis; Then, the vibration mode of the welded structure is obtained by random response analysis, and the acceleration power spectral density of the structure is input, and then the stress power spectrum density of the dangerous part is obtained Finally, the appropriate stress probability density distribution model is selected to predict the fatigue life with S-N curve equation and Miner damage accumulation theory. The results show that the fatigue life predicted by this method is very close to that of rain flow counting method.

Under the influence of equipment and environment, gaussian white noise will be accompanied in the process of obtaining the measured vibration mode of the structure, thus masking the effective features of signal and disturbing the effect of damage identification. To avoid this problem, this paper presented a new denoising method. Firstly, the multi-index evaluation function constructed by analytic hierarchy process is used to select the optimal wavelet base and the decomposition layers’s number. Secondly, we use the newly constructed wavelet threshold function to research the wavelet coefficients in the high frequency part of the signal to remove the noise coefficients. Simulation results show: the new denoising method is contributing in improving the SNR of vibration signals and reducing the RMS error. The experimental results testified that the new method can effectively increase the accuracy of structural damage identification.

Based on the density functional theory, the energy band and electronic structure of β-CuGaO2 are calculated by the modified Becke-Johnson plus an on-site Coulomb U (MBJ + U) approach in this paper. The calculated results show that the band gap value of β-CuGaO2 obtained by the MBJ + U approach is close to the experimental value. The calculated results of electronic structure indicate that the main properties of the material are determined by the bond between Cu-3d and O-2p energy levels near the valence band of β-CuGaO2, while a weak anti-bond combination is formed mainly by the O-2p energy level and Ga-4s energy level near the bottom of the conduction band of β-CuGaO2. The β-CuGaO2 thin film is predicted to hold excellent photovoltaic performance by analysis of the spectroscopic limited maximum efficiency (SLME) method. At the same time, the calculated maximum photoelectric conversion efficiency of the ideal CuGaO2 solar cell is 32.4%. Relevant conclusions can expand β-CuGaO2 photovoltaic applications.

The generation and propagation characteristics of bright spatial bound-soliton pairs (BSPs) are investigated under the diffusion effect in photovoltaic photorefractive crystals by numerical simulation. The results show that two coherent solitons, one as the signal light and the other as the control light, can form a BSP when the peak intensity of the control light is appropriately selected. Moreover, under the diffusion effect, the BSP experiences a self-bending process during propagating and the center of the BSP moves on a parabolic trajectory. Furthermore, the lateral shift of the BSP at the output face of the crystal can be manipulated by adjusting the peak intensity of the control light. The research results provide a method for the design of all-optical switching and routing based on the manipulation of the lateral position of BSPs.

In order to get high yield of nano-Graphite oxide through raw materials of nature graphite, the preparation process of oxidation, expansion, and ultrasound smash were studied. It is found that the more intense of oxidation reaction is, the more crack the expanded graphite is, and more completely the expansion of the nano-Graphite oxide will be. The Large expansion volume of the nano-Graphite oxide can be more easily crushed into nano-Graphite oxide at the same ultrasonic time. And the longer the ultrasonic time is, the more the yield of nano particle size of expanded nano-Graphite oxide is. And the less ultrasonic time can get the smaller nano particle size. The result shows that the best process conditions of nano-Graphite oxide are as follows: Vsulfate acid: VNitrate acid = 5:1, m (fine graphite): m (Potassium permanganate) = 1:0.18. The expansion temperature is 950-1000°C, and ultrasonic time is 10h.

A spatio-temporal mode-locked (STML) fiber laser is reported based on a semiconductor saturable absorber mirror. The laser has an all-fiber structure and the mode-locking threshold is as low as 200 mW. Single and multiple pulses with switchable central wavelengths are obtained. In particular, pump hysteresis is observed during the generation and disappearance of multiple pulses. The experimental results help to further understand the dynamic characteristics of STML fiber lasers and to explore how they are connected with conventional mode-locked fiber lasers in terms of soliton nonlinear phenomena, which may stimulate new applications in optical communications and nonlinear science.

The dark channel prior defogging algorithm is a method for rough estimation of transmittance. The dark channel prior method is not obvious enough for the sky. The paper uses a rough estimation model based on the relationship between depth of field and transmittance. A dehazing method that makes the transmittance more refined is proposed on a priori basis. The atmospheric light value is calculated from the atmospheric scattering model, and the image is converted from the RGB color space to the HSV color space and the S (saturation) component is extracted as a supplement to the transmittance. The final transmittance is obtained by the method of transmittance fusion, and a clear image is restored according to the atmospheric scattering model. The experimental results show that the method can effectively eliminate the fog, and the restored image better preserves the image details.

Highly active Al–Ga–In–SnCl2 composites for hydrogen production were prepared by mechanical ball milling. X-ray diffraction, scanning electron microscopy, and x-ray photoelectron spectroscopy analyses were used to characterize the composition and morphology of the composites. Moreover, the hydrogen production performance of the composites was systematically investigated at room temperature. The experiment results indicated that the addition of SnCl2 significantly enhanced the hydrolysis properties of Al–Ga–In ternary alloys. The Al-3%Ga-3%In-5%SnCl2 composite exhibited the optimal hydrogen production performance with a maximum hydrogen production of 1190 ml g−1 and a maximum generation rate of 1110 ml min−1 g−1 at 25 °C. Furthermore, we studied the effect of milling time, initial water temperature, and water quality on the final hydrogen production performance.

We demonstrate a tunable and switchable dual-wavelength passively mode-locked Bi-doped all-fiber ring laser by using nonlinear polarization rotation (NPR) technique. Exploiting the spectral filtering effect caused by the combination of the polarizer and intracavity birefringence, the wavelength separation of dual-wavelength mode-locked pulses can be flexibly tuned between 2.38 and 20.45 nm. Taking the advantage of NPR-induced intensity-dependent loss to suppress the mode competition, the stable dual-wavelength pulses output is obtained at room temperature. Moreover, the dual-wavelength switchable operation is achieved by simply rotating the polarization controllers (PCs).

Cartilage viscoelasticity changes with cartilage degeneration. Therefore, measurement of cartilage viscoelasticity could offer an alternative to traditional imaging methods for early diagnosis of osteoarthritis. In previous studies, we confirmed the feasibility of using the Lamb wave method (LWM) to assess the elasticity within a simulated cartilage-bone structures. The objective of the present study was to test the suitability of the LWM for measuring viscoelastic properties of ex vivo bovine tibial plateau cartilage. Theoretical and numerical analyses were performed to understand the viscoelastic Lamb wave propagation in cartilage and a suitable measurement range and loading frequency for the LWM were determined. The viscoelasticity of bovine cartilage was experimentally estimated to be 32.8 ± 0.50, 30.9 ± 0.50, and 31.9 ± 1.85 Pa · s for cartilage samples with thicknesses of 2.84 ± 0.02, 2.32 ± 0.03, and 2.01 ± 0.08 mm, respectively, which showed good repeatability during LWM measurements. However, cartilage elasticity was not sensitive to the viscoelastic Lamb wave speed. Indentation tests were also performed and cartilage elasticities were 0.88 ± 0.09, 1.03 ± 0.12, and 0.93 ± 0.09 MPa, respectively. This study validates the use of the LWM for measuring the viscoelasticity of ex vivo cartilage and provides a critical step toward the ultimate goal of measuring the viscoelasticity of cartilage in vivo.

Ultrafast fiber lasers have been demonstrated to be great platforms for the investigation of soliton dynamics. The soliton molecules, as one of the most fascinating nonlinear phenomena, have been a hot topic in the field of nonlinear optics in recent years. Herein, we experimentally observed the real-time evolving behavior of soliton molecule in an ultrafast fiber laser by using the dispersive Fourier transformation technology. Several types of evolving soliton molecules were obtained in our experiments, such as soliton molecules with monotonically or chaotically evolving phase, flipping and hopping phase. These results would be helpful to the communities interested in soliton nonlinear dynamics as well as ultrafast laser technologies.

A tunable multiwavelength fiber laser based on an optically tunable Mach–Zehnder comb filter incorporating Yb-doped fibers is proposed and demonstrated. By selectively pumping the Yb-doped fibers, the lasing lines can be continuously tuned towards longer or shorter wavelengths. Up to 20 stable lasing lines with channel spacings of 0.76 nm in a 3-dB bandwidth were achieved at room temperature. Moreover, the laser tuning operation could easily cover the whole channel spacing by simply shifting the half-channel spacing separately in two opposite directions. The proposed multiwavelength fiber laser provides a simple and flexible optical tuning operation, which would be beneficial for its applications in fields requiring accurate tuning optical sources.

A channel-spacing switchable multi-wavelength fiber ring laser by using one segment of polarization-maintain fiber (PMF) is experimentally demonstrated. By adjusting the polarization controllers, the wavelength spacing could be efficiently switched between 0.2 nm and 0.4 nm. Compared with the multi-wavelength fiber laser using the PMF filter previously reported, the channel-spacing switchable operation can be realized by using only one segment of PMF without changing the length of PMF. Meanwhile, the lasing output, including the lasing locations and the number of the lasing lines, can also be flexibly adjusted through the wavelength-dependent polarization rotation mechanism.

A sideband controllable erbium-doped fiber ring laser passively mode-locked by using the nonlinear polarization rotation technique is reported. In our fiber laser, spectral sideband generation or suppression can be easily achieved by properly rotating the polarization controllers. When the sideband suppression achieved, the 3 dB bandwidth of 19.68 nm and the pulse duration of 132 fs were obtained. It is evident that the limitation of pulse duration resulting from the sideband was eliminated in our experiment. Based on the experimental results, we believed that the sideband control in the fiber laser is a result of the dispersive waves filtered by the passive polarizer in the laser cavity.

We presented a bound-state operation in a fiber laser with near-zero anomalous dispersion based on a silica-coated gold nanorods (GNRs@SiO2) saturable absorber (SA). Using a balanced twin detector measurement technique, the modulation depth and nonsaturable loss of the GNRs@SiO2 SA were measured to be approximately 3.5% and 39.3%, respectively. By virtue of the highly nonlinear effect of the GNRs@SiO2 SA, the bound-state pulses could be easily observed. Besides the lower-order bound-state pulses with two, three, and four solitons, the higher-order bound states with up to 12 solitons were also obtained in the laser cavity. The pulse profiles of the higher-order bound states were further reconstructed theoretically. The experimental results would give further insight towards understanding the complex nonlinear dynamics of bound-state pulses in fiber lasers.

The 4-at.% Tm:Sc2SiO5 (Tm:SSO) crystal is successfully obtained by the Czochralski method. The optical properties and thermal conductivity of the crystal are investigated. The broad continuous wave (CW) laser output of (100)-cut Tm:SSO with the dimensions of 3 mm× 3 mm× 3 mm under laser diode (LD)-pumping is realized. The full width at half maximum (FWHM) of the laser emitting reaches up to 21 nm. The laser threshold of Tm:SSO is measured to be 0.43 W. Efficient diode-pumped CW laser performance of Tm:SSO is demonstrated with a slope efficiency of 25.9% and maximum output power of 934 mW.

We present a new tool for colour-magnitude diagram (CMD) studies, $Powerful~CMD$. This tool is built on the basis of the advanced stellar population synthesis (ASPS) model, in which single stars, binary stars, rotating stars, and star formation history have been taken into account. Via $Powerful~CMD$, the distance modulus, colour excess, metallicity, age, binary fraction, rotating star fraction, and star formation history of star clusters can be determined simultaneously from observed CMDs. The new tool is tested via both simulated and real star clusters. Five parameters of clusters NGC6362, NGC6652, NGC6838 and M67 are determined and compared to other works. It is shown that this tool is useful for CMD studies, in particular for those with the data of the Hubble Space Telescope (HST). Moreover, we find that the inclusion of binaries in theoretical stellar population models may lead to smaller colour excess compared to the case of single star population models., Accepted to publish in RAA

We report on the generation of various multi-soliton patterns in a fiber laser using a microfiber-based gold nanorod saturable absorber (GNR SA). By depositing GNRs onto a microfiber, the nonlinear effect and photo-thermal stability of the GNR SA are both enhanced due to the evanescent field interacting with the nonlinear material GNRs for a relatively long interaction time. Benefiting from a high third-order nonlinear coefficient and the excellent saturable absorption of GNRs, versatile multi-soliton patterns such as random distribution multi-solitons, soliton clusters, soliton molecules, multiple solitons occupying the whole cavity, and soliton flow can be easily obtained by properly adjusting the laser cavity parameter settings. The experimental results contribute to further understanding the physical mechanisms of multi-soliton dynamics, and demonstrate that the microfiber-based GNR SA is an excellent candidate for investigating the nonlinear phenomena in ultrafast fiber lasers.

A wavelength-switchable femtosecond pulse fiber laser is demonstrated by using a saturable absorber (SA) of silica-encased gold nanorods (GNRs@SiO2). The GNRs@SiO2 SA presents a modulation depth of 4.5% and nonsaturable loss of 32.1%. By properly adjusting the cavity parameters, femtosecond mode-locked pulses centered at 1535.6 nm and 1560.5 nm could be achieved alternately. The durations of pulses at the two wavelengths are measured to be ~403 fs and ~426 fs, respectively. The achieved results indicated that the GNRs@SiO2 could indeed be a promising nonlinear material with excellent photothermal stability and saturable absorption, which could satisfy the requirements for different photonic devices and applications.

The influence of an optically induced waveguide lattice with a defect on the coherent interaction of one-dimensional lattice solitons (LSs) formed via the photovoltaic photorefractive effect is investigated by employing numerical simulations. The results show that the uniform lattice can keep the neighboring LSs propagating with constant spacing and can affect the energy transfer between them. Further research has shown that the energy transfer can be effectively controlled by adjusting the relative phase difference between neighboring LSs and by introducing a defect in the waveguide lattice.

We report on the generation of a noiselike soliton molecule induced by a comb filter in a figure-eight fiber laser. Despite the noiselike mode-locked operation, there were always several peaks riding on a wide shoulder when the mode-locked operation was obtained; this phenomenon was called the noiselike soliton molecule. It was found that the formation of the noiselike soliton molecule is induced by the intracavity comb filter. The observed results would give further insight towards understanding both the fundamental physics of soliton molecules and the noiselike pulses in passively mode-locked fiber lasers.

A passively Q-switched thulium-doped fiber (TDF) laser based on the nonlinear polarization evolution technique was demonstrated with the central wavelength of 1898.4 nm. With the increasing pump power, the pulse repetition frequency of the Q-switched TDF laser from 87.6 to 110.1 kHz was achieved, while the corresponding pulse duration was changed from 1171 to 785.7 ns. The power instability of the TDF laser was measured to be about ±1.5% during 8 h. In addition, the mode-locked phenomenon was also observed in our all-fiber TDF laser by carefully adjusting the polarization controllers.

The generation of high-energy dual-wavelength domain wall pulse with a low repetition rate is demonstrated in a highly nonlinear fiber (HNLF)-based fiber ring laser. By introducing the intracavity birefringence-induced spectral filtering effect, the dual-wavelength lasing operation can be achieved. In order to enhance the cross coupling effect between the two lasing beams for domain wall pulse formation, a 215-m HNLF is incorporated into the laser cavity. Experimentally, it is found that the dual-wavelength domain wall pulse with a repetition rate of 77.67 kHz could be efficiently obtained through simply rotating the polarization controller (PC). At a maximum pump power of 322 mW, the 655-nJ single pulse energy in cavity is obtained. The proposed configuration provides a simpler and more efficient way to generate high energy pulse with a low repetition rate.

We report on the generation of a high-energy noiselike rectangular pulse in a mode-locked figure-eight fiber laser. The noiselike pulse appeared to have a rectangular shape on the oscilloscope. The pulse duration increased with increasing pump power, while the peak amplitude remained constant, which is very similar to the pulse evolution of dissipative soliton resonance. However, the pulse type is confirmed as a noiselike pulse using an autocorrelator. With the maximum pump power of 350 mW, the 135 nJ noiselike rectangular pulse with 76 ns duration was achieved. The results provide a new guideline for clarifying an alternative formation mechanism of the high-energy rectangular pulses in fiber lasers.

We report on the generation of high-energy noiselike pulse in a passively mode-locked thulium-doped fiber ring laser based on the nonlinear polarization evolution technique. A newly developed heavily thulium-doped germanate glass fiber was used as the gain medium. By properly rotating the polarization controllers, the 17.3 nJ noiselike pulse with 60.2 nm spectral bandwidth was obtained at the fundamental pulse repetition frequency of 6.37 MHz. Correspondingly, the maximum average output power was 110 mW. The direct output of high-energy noiselike pulse from the thulium-doped fiber laser provides a good candidate of pulse source for some important applications such as the supercontinuum generation at mid-infrared wavelength range and optical metrology.

Passive harmonic mode-locking (HML) in a fiber laser with a microfiber-based graphene saturable absorber (SA) is presented. The microfiber-based graphene SA is employed to enhance the nonlinear effect of the laser cavity, which is beneficial to achieving high-order HML operation. Depending on the pump power level, up to 101st HML (555 MHz) was obtained. The results demonstrate that the microfiber-based graphene SA could be used as highly nonlinear photonic devices in fiber lasers for effectively realizing high-order passive HML operation.

A compact, intracavity optical deposition of graphene saturable absorber (SA) for low-threshold passively mode-locked fiber laser is proposed and demonstrated. The optical deposition is implemented in the laser cavity by using a slot collimator. Utilizing the fabricated graphene SA, the fiber laser achieves self-starting, passively mode-locked operation at a low threshold of 32 mW pump power, delivering a 13.1-MHz 2.36-ps pulse train.

A wide-band tunable femtosecond pulse fiber laser was demonstrated by using the intracavity-birefringence induced spectral filtering effect. The nonlinear polarization rotation (NPR) technique is used to achieve passive mode-locking femtosecond pulses. Taking advantage of the intracavity-birefringence induced spectral filtering effect, the center wavelength of the mode-locked femtosecond pulse can be continuously tuned from 1532 to 1570 nm by properly rotating the polarization controller (PC). The mechanism of the wavelength tuning operation is discussed. Furthermore, the experimental observation was confirmed by the numerical simulations.

A compact and efficient intracavity optical deposition of graphene saturable absorber (SA) for a passively mode-locked fiber laser is proposed and demonstrated. The setup for optical deposition is integrated in a fiber ring laser through a slot collimator. By dripping the dimethylformamide (DMF) solution of graphene into the gap of the slot collimator between two fiber ferrules, graphene can be well deposited onto the fiber end to form an SA. The transmission loss of graphene SA is measured. As for application, the fiber ring laser is passively mode-locked with the prepared graphene SA and generates a 1 ps, 13.6 MHz soliton pulse train.

The dark soliton pulse with spectral sideband is experimentally observed in a dispersion-managed all-fiber ring laser with net negative cavity group velocity dispersion. We find that, for single or multiple dark solitons, the spectral sidebands always appear and exhibit asymmetric characteristics which are similar to bright solitons. The experimental measurements of spectral sideband positions are carried out and the results are in good agreement with the calculated values. Our results show that spectral sideband effect is also an intrinsic feature of a dark soliton fiber laser.