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This study firstly applies ant colony algorithm to optimize the classification index formulas and comprehensive index formulas related to the environmental benefits of ecological mining areas and builds an environmental benefits evaluation model. Then taking the ecological mining area of China Pingmei Shenma Energy Chemical Group as an example, the simulation software MATLAB is used to evaluate the environmental benefits from four aspects: system structure, resource utilization, environmental effects and economic results, thus the environmental benefits grades of the mining area before and after ecological construction are confirmed. With this research, the author’s endeavor is to provide a new objective evaluation method to check if the construction of ecological mining areas can realize the goal of coordinated development of economy, society and environment of coal industry.

A NO2 sensor based on novel SnO2/graphene nanocomposite materials was proposed. Monolayer graphene was decorated with tin oxide via drop-casting and vacuum annealing, and the monolayer graphene was prepared using the chemical vapor deposition (CVD) method. The nanocomposites were characterized by Raman spectroscopy and a scanning electron microscope (SEM). The gas sensing capabilities of the SnO2/graphene nanocomposites for NO2 gas were investigated. Compared with the pure graphene sensor, the sensitivity of the SnO2/graphene sensor is higher and the recovery time is shorter. Moreover, the recovery time of the sensor is clearly further shortened using transient UV light irradiation. The SnO2/graphene sensor augmented with transient UV irradiation can achieve fast response/recovery with NO2. The sensor was demonstrated to have huge potential for real-time detection of NO2 at room temperature (25 °C).

Using a YVO4/Nd:YVO4/YVO4 composite crystal end pumped by laser diode, we demonstrate the simultaneously Q-switched and mode-locked self-Raman laser at the firststokes wavelength of 1176.07 nm. Its corresponding linewidth was measured to approximately be 0.14 nm. At the pump power of 38 W and the pulse repetition frequency of 50 kHz, the maximum average output power at 1176 nm was obtained to be 1.34 W with the corresponding optical conversion efficiency of 3.6%. The highest pulse energy and the highest peak power were obtained to be 35 μJ and 10.5 kW, respectively. The shortest mode-locked pulse width of the laser was obtained to be ~300 ps with the corresponding repetition rate of mode-locked laser pulse is ~ 1.11 GHz

Hemodynamic patterns play key roles in progression of carotid vulnerable plaques. However, most of previous studies utilized maximum or averaged value of hemodynamic measurements which is not an ideal representative of hemodynamic patterns. This study aimed to investigate the association of slice-based and time-specific hemodynamic measurements with carotid vulnerable plaque using magnetic resonance (MR) vessel wall imaging and histology.Thirty-two patients (mean age: 63.9±8.1 years; 25 males) with carotid atherosclerotic stenosis (≥50% stenosis) referred to carotid endarterectomy were recruited and underwent MR vessel wall imaging. Carotid plaque burden was evaluated on MR images and vulnerable plaque features including calcification, lipid-rich necrotic core, and intra-plaque hemorrhage (IPH) were identified by histology. The slice-based and time-specific hemodynamic measurements were extracted from computational fluid dynamics simulation of 3D carotid arterial model. Correlation coefficients between hemodynamic measurements and carotid plaque features were calculated and the logistic regressions with generalized estimating equation (GEE) were conducted. The value in discriminating carotid vulnerable plaque features was determined by receiver-operating-characteristic analysis.Of 102 MR-histology matched slices from 32 patients, time-averaged wall shear stress (TAWSS) (r=0.263, p=0.008), oscillatory shear index (OSI) (r=-0.374, p0.001), and peakWSS (r=0.232, p=0.019) were significantly associated with carotid IPH. The logistic regression with GEE revealed that peakWSS (OR, 1.206; 95% CI, 1.026-1.418; p, 0.023) and TAWSS (OR, 0.364, 95% CI, 0.138-0.959; p, 0.041) were significantly associated with presence of IPH after adjusting for age and BMI. In discriminating carotid IPH, the AUC of TAWSS, OSI, combined TAWSS with maximum wall thickness (MWT) and combined OSI with MWT was 0.656, 0.722, 0.761, and 0.764, respectively.Slice-based and time-specific hemodynamic characteristics could effectively discriminate carotid IPH. Combination of hemodynamic measurements with carotid plaque burden might be a stronger indicator for carotid vulnerable plaque features than each measurement alone.

This study aims to identify numerical analysis methods for the reliability prediction of rotating mirror(RM) strength at the early-stage design. A mathematical model for the strength reliability analysis of RM is established based on the Monte Carlo method, small-sample theory, and reliability principle. Numerical analysis on the strength reliability of RM is conducted, and the results are experimentally verified according to small-sample theory. The spearman rank order correlation coefficients between structure parameters and the maximum stress is the circumradius of mirror body, and that of the material variable is the elastic modulus of high-strength aluminum alloy(Al). The skewness and kurtosis values of maximum stress and strain are all positive. Calculated statistical results obey normal distribution and are right skewed. At 95% confidence level, the strength reliability of the RM with a design speed of 70,000 rpm is 0.999. This finding shows that the strength reliability of the RM meets the required design in ideal state. No failure of RMs occurs among strength reliability experiment, proving the validity of the numerical model. This model provides an economic, feasible, and effective method for estimating the strength reliability of RM.

We theoretically and numerically investigated the modal properties of three different kinds of cross-section rotating mirrors. At the same facet size, the fundamental frequency of equilateral-triangle cross-section rotating mirror (ET-RM) was 8725.4 Hz, which was 1.81 times and 4.60 times higher than that of equilateral-square and equilateral-hexagonal rotating mirrors. The displacement response curves of the three kinds rotating mirrors show that the amplitude of the first peak is further larger than the second one. The first bending modal of rotating mirror is the main reason of the damage for rotating mirrors. The maximum working speed of ET-RM with face size of 17.32 mm × 36 mm is 44,400 rpm. That of the other two kinds of rotating mirror are 37,800 rpm and 27,000 rpm respectively. The equilateral-triangle cross-section as an ideal structure of rotating mirror for ultra-high-speed cameras based on the dynamic properties.

A 45° fiber cantilever beam for high temperature measurement was fabricated by femtosecond laser in single mode fiber. The temperature sensitivity is obtained to be about 17 pm/℃ at 800 ℃ and 1560 nm. The 45° fiber cantilever beam possesses good repeatability and stability in high temperature. The sensor is small in size, cheap and good stability.

Wireless power transfer (WPT) is a biocompatible and flexible, convenient and stable energy transmission technology, has a huge application market in consumer electronics and implantable medical aspects. With regard to WPT, improving the transmission efficiency has always been a great challenge. In this paper, a novel four coil wireless energy transmission system based on magnetic resonances analyzed, the formula of quality factor, transmission distance and transmission efficiency is derived. A new coil structure parameter design is proposed. Through the model simulation of the number of turns, the number of strands and the pitch of the turns, the quality factor and inductance of the coil are analyzed by the electromagnetic simulation software HFSS, and the optimal structural parameter values are obtained. The coil with the optimal structural parameters can reach 102 at 13.56 MHz frequency. These structural parameters provide effective reference and guidance for obtaining high quality factor coils and efficient wireless energy systems.

This study aims to examine the influence law of polyhedron structure on the spatial mechanical properties of ultra-high-speed rotating mirrors. To this end, polyhedral beryllium alloy rotating mirrors are investigated on the basis of elastoplastic theory and finite element method. The maximum stress is located at the end position of the contact between the shaft and the mirror body. Stress increases with the number of mirror faces. The different structures have a negative stress gradient. The structural strength of rotating mirror is affected by the strength of the mirror body material in high-speed rotation of the tensile force of centrifugal force. The lateral deformation of the mirror surface is caused by the combined effect of compression of centrifugal force generated by the material of sharp-corner and the tretching of tensile force caused by the material at the centre of the mirror at high-speed rotation. The amount of mirror surface deformation is not proportional to the number of faces. The rotating mirror with iso-quadrangular structure has the best lateral deformation effect. This research provides a theoretical basis for the research and design of rotating mirrors with high potential value.

This paper demonstrate an intracavity Raman laser at 2291 nm by using YVO4 crystal as Raman crystal to achieve efficient Raman conversion in a compact diode-end-pumped actively Q-switched Tm:YLF (Tm3+-doped lithium yttrium fluoride) laser with an L-shaped cavity. With a pump source of fiber-coupled continuous-wave diode laser operating at 793 nm, the Tm:YLF crystal served as gain material in the Raman laser. We made experimental research on the characteristics of first-Stokes Raman laser output the different pulse repetition rates (PRFs). The maximum average output power, pulse width and the corresponding peak power were 175.2 mW, 21.41 ns and 1.63 kW respectively at a pluse repetition frequency of 5 kHz and an incident pump power of 21W.

A simple Mach–Zehnder interferometer (MZI) was presented for high temperature measurement. The device was composed of a short segment of suspended-core fiber (SCF) sandwiched between two standard single mode fibers (SMFs) with a misaligned splicing joint. Lower temperature measurements were firstly carried out from room temperature to 190 °C, and the obtained sensitivity at the wavelength of 1465 nm was 25.82 pm/°C. However, a nonlinear response was further achieved for high-temperature sensing up to 1000 °C. Between 20 and 200 °C, the sensitivity was just 24.24 pm/°C at the wavelength of 1457 nm, whereas a higher sensitivity of 53.87 pm/°C was acquired in the range of 200–1000 °C. In addition, the strain cross-sensitivity was extremely low. As a result, the device can be developed as a strain-independent temperature sensor and become an excellent candidate for high temperature measurement.

Rotating mirror is not only as an imaging element in optical path of ultra-high speed camera, where imaging quality is affected by surface quality and plane deformation of the rotating mirror, but also as an element to implement ultra-high speed, because performances of the ultra-high-speed camera system are mainly dependent on the static and dynamic mechanical properties of the rotating mirror. In this paper, the static and dynamic properties of magnesium alloy rotating mirror with equilateral-triangle cross-sections were investigated by theoretically and numerically method. At the speed of 2×105 rpm, the maximum lateral deformations of the mirror facet with width 17.32 mm and length 40 mm is 2.476 μm. The maximum von Mises stress is 35.1 MPa. The deformation and stress are less than that of aluminum alloy rotating mirror, which has been successfully applied in many types of RM for ultra-high speed cameras. The first three frequencies of magnesium alloy rotating mirror are 9,539.9 Hz, 9,540.9 Hz and 12,726.0 Hz, respectively. While the first three frequencies of aluminium alloy rotating-mirror are 9,683.9 Hz, 9,685.2 Hz and 11,016.0 Hz. From which it is preliminarily shown that a magnesium alloy rotating mirror can be used as replacement for an aluminium alloy rotating mirror in ultra-high-speed camera.

We demonstrate a novel and compact fiber-probe pressure sensor based on a micro-Fabry–Perot interferometer (FPI). The device is fabricated by splicing both ends of a short-section simplified hollow-core photonic crystal fiber (SHC-PCF) with single-mode fibers. Then, a microchannel is drilled by a femtosecond laser micromachining in the SHC-PCF to allow air to diffuse in. The pressure sensing mechanism is based on the dependence of the air refractive index on pressure. We use both theory and experiment to investigate the sensing characteristics. A micro-FPI with a length of 272 μm demonstrates a pressure sensitivity of 4.071 nm/MPa at 1580 nm and a low-temperature sensitivity of 1.1 pm/°C at atmospheric pressure. We further study the temperature cross sensitivity of the sensor under different pressures. The sensor also shows strong stability and good reversibility, and may be potentially used in pressure sensing applications.

In this letter, we reported long period fiber gratings (LPFGs) fabricated by femtosecond laser pulses direct writing in grapefruit microstructured fiber. The mode field distribution and dispersion property of this fiber was analyzed by finite-element method. Two LPFGs were fabricated with different periods of 230 and $250~\mu \text{m}$ , the resonant dips appeared at the wavelengths of 1325.8 and 1449.4 nm, respectively. In addition, sensing characteristics of the LPFG with the period of $250~\mu \text{m}$ were investigated in theory and experiment. The experimental results show that the strain and temperature sensitivities are 1.88 pm/ $\mu \varepsilon $ and 0.267 pm/°C, respectively. It indicates that the temperature cross sensitivity is as low as $0.142~\mu \varepsilon $ /°C.

A novel and simple sensor based on fiber-optic modal interferometer fabricated by a segment of low elliptical hollow-core photonic bandgap fiber for simultaneous temperature and twist measurements is demonstrated. Meanwhile the sensor can also measure the twist angle and determine the twist direction simultaneously. The mode distribution of EHC-PBGF is demonstrated both in theory and experiments. There is an obvious difference of two transmission dips on the temperature and twist. The twist sensitivities of Dip 1 and Dip 2 are obtained to be −31.95 and −585.8 pm/(rad/m), respectively. The temperature sensitivities are 12.99 pm/°C for Dip 1 and 5.09 pm/°C for Dip 2, respectively. Two parameters of twist and temperature can be distinguished and measured simultaneously by using a sensing matrix. Meanwhile the structure is found to be weakly sensitive to the axial strain. It has the advantage of avoiding the crosstalk of strain in the applications.

A high power diode-pumped continuous-wave Tm:YAP laser with a piece of silicon chip as the output coupler (Si-OC) is demonstrated. A maximum output power of 13 W with a beam quality of M2 ≤ 1.45 at 1931 nm was obtained, corresponding to an optical-to-optical efficiency of 31%, and a slope efficiency of 33%. To our best knowledge, this is the first report of utilizing silicon as a output coupler on solid Tm:YAP laser system. The mechanism of silicon output coupler on Tm:YAP laser is also discussed in this letter. Because of the intriguing characteristics of silicon, such as high damage threshold, low cost and long-pass filter property, double-sided polishing single crystal silicon chip can perform as a good output coupler in high power laser system near 2 μm region.

Eye-safe pulse lasers have attracted increasing attention due to their potential wide application in many fields. However, optical modulators with excellent nonlinear optical absorption properties in the range of 1.4-2.1 μm are still very scarce. In this study, tin diselenide (SnSe2), a newly-developed 2D layered semiconductor material with facile processability and low cost, was investigated. The nonlinear optical response of SnSe2 was investigated using the open aperture Z-scan method at 1500 and 1800 nm. Using SnSe2 as the saturable absorber, a passive Q-switched solid-state laser was realized at 1.3 and 1.9 μm for the first time. This study proved SnSe2 to be an effective optical modulating material for the eye-safe waveband.

A diode-end-pumped composite YVO4/Nd:YVO4/YVO4 crystal self-Raman laser at the second-Stokes wavelength of 1,764 nm is demonstrated. The maximum average output power of second-Stokes radiation was up to 0.99 W at a pump power of 34 W and a pulse repetition frequency of 20 kHz, corresponding to an optical conversion efficiency of 2.9 %. The highest peak power and the shortest pulse duration were 21.5 kW and 1.92 ns, respectively.

Mach–Zehnder interferometer strain sensors made from pieces of photonic crystal fiber spliced to standard single mode fibers are fabricated with different lengths. High strain sensitivity of 2.1 pm/μe at 1550 nm is achieved with the length of 45 mm. The interference is induced by the core mode and the high order core mode due to the special air hole structure of PCF, which is independent of the surrounding refractive index. The temperature sensitivity (∼13.24 pm/°C) is relatively low. This structure is good in avoiding cross sensitivity in strain measurement and is fabricated with a simple process and low cost.

We report a diode-end-pumped acousto–optically Q-switched composite YVO4/Nd:YVO4/YVO4 crystal self-Raman yellow–green laser, based on the intracavity sum-frequency generation of the fundamental and first-Stokes fields in LiB3O5 crystal. Maximum average output power at 559 nm is 3.55 W at the incident pump power of 32 W and pulse repetition frequency (PRF) of 30 kHz, with an optical conversion efficiency of 11%. The highest pulse energy and peak power are 129 μJ and 10.5 kW at 20 kHz PRF, respectively. The power stability of yellow–green radiation is better than 2% for 40 min at an average output power around 3 W.

Gesture detection is an important aspect of intelligent human-computer interactive systems. Recently, device-free gesture detection in wireless local area networks (WLANs) has been proposed to reduce the detection cost and complexity, whether using (1) the Received Signal Strength Indicator (RSSI), or (2) the more reliable Channel Side Information (CSI) . In this paper, we use CSI information extracted from packet transmissions to detect certain gestures and further distinguish between detected gestures by their strength. Experimental results establish the efficacy of the proposed techniques.

We reported the generation of visible red light through degenerate four wave mixing (FWM) in an all solid photonic bandgap fiber (PBGF), which was achieved by pumping the fiber with a 800 nm Ti:sapphire-based femtosecond pulse laser. At a fiber length of 30 m, a broadband anti-Stokes spectrum range from 620 nm to 740 nm was obtained at the highest pump power, the spectrum evolution as a function of pump power and propagation distance had been measured. Furthermore, the intensity-dependent parametric gain characteristic is also calculated, which accords well with the experimental results.

A method to characterize the thermal lens in a Nd:GdVO4 self-Raman laser is presented. The thermal focal length was measured to be as short as 180 mm with a self-Raman laser output power of 0.95 W. For comparison, the thermal focal lengths in the cases of fundamental operation and first-Stokes operation were measured experimentally, indicating that the heat generated in the SRS process exacerbated the thermal loading of the Nd:GdVO4 crystal.

We report a laser-diode-end-pumped acousto-optical Q-switched double-end diffusion-bonded Nd : YVO4 self-Raman laser at 1176 nm. The maximum average output power at the first-Stokes wavelength of 1176 nm was obtained to be 3.1 W at the incident pump power of 25 W and the repetition rate of 90 kHz, with the corresponding optical conversion efficiency of 12.4%. The shortest pulse width, the maximum pulse energy and the highest peak power were measured to be 5 ns, 42 μJ and 7.5 kW, respectively.

A laser diode pumped actively Q-switched Nd:GdVO4 self-Raman laser operating at 1173 nm is presented. The maximum output power was 2.26 W at an incident pump power of 18 W, with the corresponding optical conversion efficiency of 12.6%. Two different resonator configurations were investigated in order to achieve high output power and efficiency.

Supercontinuum generation (SC) of more than one octave spectrum spanning covering from 400 nm to 820 nm was achieved by pumping a piece of aluminum nitride (AIN) single crystal using a nanosecond 355 nm ultraviolet laser. The AlN with a thickness of ∼0.8 mm was grown by an optimized physical vapor transport technique and polished with solidification technology. Compared to previously reported ones, the achieved visible SC exhibited the broadest spectrum spanning from bulk materials pumped by a nanosecond pulse laser. The visible supercontinuum in AlN presents new opportunities for bulk material-based white light SC and may find more potential applications beyond typical applications in integrated semiconductive photoelectronic devices.

Femtosecond laser pulses with ultrashort time duration and ultrahigh peak power can cause the refractive index change in transparent materials and micron scale machining precision. Long period fiber gratings (LPFGs) with different periods and different grating lengths in the standard single mode fiber were fabricated, using laser direct writing method, by femtosecond laser pulses with pulse width of 200 fs at a center wavelength of 800 nm in air. The transmission spectra were studied in the range of 1510 nm to 1610 nm. Two LPFGs with period of 400 μm, and 550 μm, respectively fabricated with same irradiation power of 275 mW, were shown. The loss peak of 1552 nm, the transmission loss of 16 dB and the FWHM of 20 nm were obtained when the period of LPFG was 400 μm, while the loss peak of 1588 nm, the transmission loss of 20 dB and the FWHM of 25 nm were achieved when the period of LPFG was 550 μm. According to the theory of mode field coupling for long period grating, it was indicated that the modulation of refractive index Δn was in the level of 10-2.

A high-power continuous-wave (CW) all-solid-state Nd:GdVO4 laser operating at 1.34 μm is reported here. The laser consists of a low doped level Nd:GdVO4 crystal double-end-pumped by two high-power fiber-coupled diode lasers and a simple plane-parallel cavity. At an incident pump power of 88.8 W, a maximum CW output of 26.3 W at 1.34 μm is obtained with a slope efficiency of 33.7%. To the best of our knowledge, this is the highest output at 1.34 μm ever generated by diode-end-pumped all-solid-state lasers.

A novel and compact fiber-probe pressure sensor was demonstrated based on micro Fabry-Perot interferometer (FPI). The device was fabricated by splicing both ends of a short section simplified hollow-core photonic crystal fiber (SHCPCF) with single mode fibers (SMFs), and then a micro channel was drilled by femtosecond laser micromachining in the SHC-PCF to significantly enhance the pressure sensitivity. The pressure sensing characteristics based on micro-FPI have been investigated by measuring the signals through the demodulation of phase since the external signal imposing on the interferometer will induce the phase change of interference signal. Then a FBG was cascaded to demodulate the signal. A micro FPI demonstrates a maximum pressure sensitivity of 32 dB/MPa, while a low temperature cross-sensitivity of 0.27 KPa/°C. Hence it may have potential for pressure applications in harsh environment.

A long-period fiber grating (LPFG) was inscribed in suspended-core fiber by femtosecond laser. The LPFG was insensitive to surrounding refractive index, and the sensitivities to temperature and strain were 4.8 pm/°C and -1.65 pm/μϵ, respectively.

Low Nd-doped 0.3 at% Nd:GdVO 4 crystal with excellent crystal quality was grown by the Czochralski method. The maximum CW output power of 8.23 W was obtained when the 0.3 at% Nd:GdVO 4 crystal was pumped by a laser diode with power 27.9 W, giving the corresponding optical conversion efficiency of 29.5% and the average slope efficiency of 30.2%. The fracture-limited pump powers of different Nd-doped crystals were estimated.

We report a high-power laser-diode-array end-pumped 0.3 at. % Nd:GdVO4 continuous-wave laser operating at 1.34 μm. The maximum output power of 13.3 W was obtained at the incident pump power of 49.2 W, giving the corresponding optical conversion efficiency of 27% and the average slope efficiency of 28.5%. The thermal focal length of the Nd:GdVO4 crystal under the pump power from 15.3 to 50 W was measured experimentally.