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Accepted: 2021-05-12, 資料番号: PA2210018000

The near field of the probe beam after passing through the gain module is measured. The “streamer effect” is first discovered in the experiment, which is characterized as continuity in the flow direction and non-uniformity in the lateral direction with high spatial frequency. To explain the “streamer effect”, a fluid–solid coupling model and an unstable resonator oscillation model of the direct-liquid-cooled thin-disk laser are established. The simulation results show that the non-uniformity of the coolant along the width of the flow channel gives rise to the streamer effect. A feasible cooling channel to achieve a high uniformity coolant is proposed and experimentally verified. At CW pumping of 9.6 kW, the influence of coolant on the output beam quality can be controlled at β

This paper presents a new Synch-Rel machine designed with a super-inductive electric steel, and compare with the baseline IPM machine for HEV/EV traction application. The comparisons cover the torque-speed capability, machine size, rotor stress, torque ripple and machine efficiency. The impact of the BH property of electric steel on the Synch-Rel machine performance is also presented.

With the rapid development of the traditional inorganic semiconductor industry, the improvement of its electrical performance is gradually approaching to the limit. It is difficult to continue to improve the performance, lessen the size, and reduce the cost. Therefore, organic semiconductor materials and devices with simple process and low cost have been found and gradually become a new research hotspot. Although organic semiconductor materials and devices are developing rapidly, their electrical properties, such as carrier mobility, are considerably inferior to those of inorganic semiconductors, and their research direction and application prospect are relatively fixed and single. They are developed only in display, sensing, photoelectric conversion and other fields, but the researches on switching power devices, integrated circuits and other fields are still relatively blank. At the same time, power devices are used only in the field of inorganic semiconductors. Therefore, in order to expand the research direction of organic semiconductors and power devices at the same time, a novelsilicon on insulator lateral double-diffused metal oxide semiconductor (SOI LDMOS)power device is reported in this paper. Unlike the SOI LDMOS power devices in traditional inorganic semiconductors, this novel device can be used in the field of organic semiconductors by combining with insulated flexible substrates, which provides a new possibility for the research direction of organic semiconductors. In this paper, both simulation and experiment verify that specific on-resistance (RON,sp) and threshold voltage (VTH) do not change significantly when the conventional SOI LDMOS lacks the substrate electrode, but the breakdown voltage decreases by about 15% due to the absence of the substrate electrode or the longitudinal electric field. In response to this phenomenon, in this paper proposed is a novel SOI LDMOS power device that possesses surface substrate electrodes and drift zone oxide trenches. This novel device can provide electrodes for the substrate again, optimize the horizontal and vertical electric field, and significantly change neither of the RON,sp and the VTH. At the same time, the breakdown voltage (BV) of conventional SOI LDMOS is increased by 57.54%, which alleviates the adverse effects caused by the application in the field of organic semiconductors. This novel SOI LDMOS power device provides the possibility of applying traditional power semiconductors to the research of organic semiconductors, and has innovative significance for expanding the organic semiconductor research.

As the economy grows and the environment deteriorates, the renewable energy is urgently needed. The advanced energy storage technology in electronic equipment, electric vehicle, smart grid, etc. becomes more significant. For example, the rechargeable batteries, hydrogen storage media, supercapacitors, the new energy storage devices have received much attention today. The anodes of the lithium ion battery (LIB), as the main body of charging and discharging, should be most important. The ideal anode material for LIBs is required to possess a higher Li capacity and a lower volume expansion. Good reversibility and high Li capacity are balanced necessarily in the electrode material. The poor cycling performance of LIB is usually due to the severe volume expansion of anode in lithiation/delithiation process. In this paper, the Li storage performance of B and N doped graphyne is explored by using the density functional theory method. The Perdew-Burke-Ernzerhof functional of the generalized gradient approximation is chosen. The calculations indicate that the doping of B atoms can enhance the adsorption strength between the Li atom and the graphyne, which can greatly increase the Li storage capacity. The Li storage capacity of B doped graphyne can reach as high as 2061.62 mAh/g, which is 2.77 times that of pristine monolayer graphyne. Meanwhile, the B doping reduces the out-plane diffusion energy barrier of Li, but increases the in-plane diffusion energy barrier slightly by 0.1 eV. On the other hand, the doping of N atoms reduces the interaction between Li and graphyne, however, the Li capacity also increases to 1652.12 mAh/g because the number of the available Li adsorption sites increases. Moreover, the doping of N atoms greatly improves the diffusion performance of Li on graphyne. The in-plane diffusion energy barrier drops to 0.37 eV, and thus the charge-discharge performance of the N doping graphyne is well improved. Therefore, the doping of B and N atoms can remarkably improve the performance of graphyne as the LIB anodes. The remarkable performance of B and N doped graphdiyne shows that it will become a promising LIB anode in the future. The present research can provide a good theoretical basis and thus conduce to guiding the developing of good Li storage materials, and can also supply strong background for experimental researches.

A direct-liquid-cooled Nd:YLF thin disk laser resonator is presented, which features the use of refractive index matching liquid (RIML) as coolant. Highly uniform pump intensity distribution with rectangular shape is realized by using metallic planar waveguides. Much attention has been paid on the design of the gain module, including how to achieve excellent cooling ability with multi-channel coolers and how to choose the doping levels of the crystals for realizing well-distributed pump absorption. The flow velocity of the coolant is found to be a key parameter for laser performance and optimized to keep it in laminar flow status for dissipating unwanted heat load. A single channel device is used to measure the convective heat transfer coefficient (CHTC) at different flow velocities. Accordingly, the thermal stress in the disk is analyzed numerically and the maximum permissible thermal load is estimated. Experimentally, with ten pieces of a-cut Nd:YLF thin disks of different doping levels, a linear polarized laser with an average output power of 1120 W is achieved at the pump power of 5202 W, corresponding to an optical-optical efficiency of 21.5%, and a slope efficiency of 30.8%. Furthermore, the wavefront aberration of the gain module is measured to be quite weak, with a peak to valley (PV) value of 4.0 μm when it is pumped at 5202 W, which enables the feasibility of its application in an unstable resonator. To the best of our knowledge, this is the first demonstration of kilowatt-level direct-‘refractive index matching liquid’-cooled Nd:YLF thin disk laser resonator.

The fiber coupled system based on mini-bars is an effective way of avoiding complex beam shaping to reduce costs and improve brightness. Forty mini-bars mounted on copper microchannel heatsink are arranged in two stacks to collimate the output beam of the stacks with the aspherical cylindrical lens and cylindrical lens array in fast and slow axis directions in this paper. For increasing the fill factor of the beams of the stacks, the beams are combined spatially in the fast axis direction. The combined beam could be coupled into the fiber of 800 m core diameter and 0.22 numerical aperture. The opto-optical efficiency of the fiber coupled module is about 58% and the maximum output power is 1360 W with the power density of 1.73105 W/cm2 at fiber output facet.

A large aperture tapered fused silica fiber phase conjugate mirror with a maximum 50.7% stimulated Brillouin scattering (SBS) reflectivity is presented, which is operated with 400 Hz pulse repetition rate and 36.5 mJ input pulse energy. To the best of our knowledge, it is the first time that over 50% SBS reflectivity is achieved by using solid-state phase conjugate mirror under such high pulse repetition rate and high pulse energy. With much higher pulse repetition rate of 500 and 1000 Hz, the maximum SBS reflectivity is 41.2% and 33.3%, respectively. A single-longitudinal-mode Nd:YAG laser is experimentally studied with master oscillator power amplifier (MOPA) scheme using such a tapered fiber as a phase conjugate mirror. A 101 mJ pulse energy is achieved at 400 Hz repetition rate, with a pulse width of 6 ns and a M 2 factor of less than 2. The corresponding peak power reaches 16.8 MW.

As a critical issue for the pavement’s quality service life, surface cracking of the pavement structure is an ongoing research topic which attracts many researchers. This paper presents a numerical study of the periodic cracks in surface layer of pavement structures based on the FEM method. The formation mechanism of the periodic cracks is analyzed and the evolving process is simulated. A parametric study, including effects of the layer thickness, tensile strength of surface layer and layer elastic modulus on the crack spacing is carried out. The numerical results indicate that the horizontal stress between two adjacent cracks decreases gradually as the crack spacing decreases. The horizontal stress transits from tensile to compressive when the crack spacing decreases to a certain value. Such a stress state transition leads to the periodic array of the surface cracks. The evolving process of the periodic cracks indicates that new cracks infill in sequence between two earlier formed adjacent cracks and the crack spacing decreases in half simultaneously. No more new crack can infill when the crack spacing reaches to a certain value even with the increasing of external load. Numerical simulations also show that the crack spacing is strongly dependent on the surface layer thickness, tensile strength of the surface layer and elastic modulus of the surface layer.

The relation between macro-properties and micro-quantities of the large-grained polycrystalline chemical vapour deposited diamond films was investigated.Considering the growth non-uniformity,the micro-Raman spectra measured on the top growth surface show large variation from spot to spot.Whereas,the micro-Raman spectra taken on the fine-grained smooth interface of the diamond films show that small deviation and generally can represent the overall quality of the large-grained polycrystaline diamond films,and correlate well with hydrogen content of the film measured by Fourier-transform infrared spectroscopy.It can be concluded that a diamond film with darker color or lower transparency has lower quality and lower phase purity characterized by the larger full width at half maximum(FWHM) and lower intensity of the diamond Raman peak around 1 332 cm-1.

A continuous-wave-operation laser amplifier chain consisting of three multi-concentration-doped Yb:YAG slab gain modules (GMs) at room temperature is presented. The output power of 22.3 kW with the beam quality of 3.3 times the diffraction limit is achieved from this chain. To the best of our knowledge, based on a Yb:YAG slab at room temperature, the highest power to date while maintaining excellent beam quality laser output. An extraction efficiency of 36% from the single slab GM is obtained and can be further enhanced to 46% by optimizing the parameters of GM. These results have confirmed that the Yb:YAG slab has an excellent scaling performance and is suitable for the development of high-average-power lasers.

We demonstrate a master oscillator power amplifier (MOPA) architecture based on Yb:YAG amplifiers and adaptive optics (AO) systems with a high power and high beam quality laser output. With two conduction cooled, dual-end-pumped Yb:YAG zigzag-slab amplifiers at room temperature, the fiber laser of 300 W was scaled to 11.9 kW. Moreover, AO system positioned downstream was utilized to correct wavefront of amplified laser. The beam quality β at maximum output power was 2.8 times diffraction limited with closed-loop AO system.

In this work, the coupled effect of nitrogen addition into CH4/H2 mixtures and surface temperature on diamond growth ranging from large grained polycrystalline to fine-grained nanocrystalline were investigated. Moreover a new growth parameter window for simultaneous growth of nanocrystalline diamond (NCD) and {100} textured large-grained diamond films was developed by using a high power high pressure 5 kW microwave plasma assisted chemical vapor deposition (MPCVD) reactor. Scanning electron microscope (SEM), Raman spectroscopy, and X-ray diffraction (XRD) are employed to characterize the morphology, crystalline quality and texture of the diamond samples. Our results can be grouped by two catalogs: First, deposition run without and with 0.24% N2 addition, while keeping all the other parameters constant, resulted in a high quality transparent large-grained polycrystalline diamond film and a NCD film, respectively. This result clearly evidences nitrogen induced nanocrystallinity. Then, two different substrate surface temperatures were obtained by overlapping a small silicon slice on the top centre of a large silicon wafer of 5.08 cm in diameter in only one deposition run using 0.24% N2 addition and the same set of parameters as the previous runs. From this growth run, a NCD film of growth rate around 2.3 microm/h was obtained at low temperature, while a {100} textured large-grained diamond film of much higher growth rate about 10.4 microm/h was grown at high temperature. These results not only confirm the reproducibility of NCD by N2 addition, but also indicate that distinct growth modes were involved at different substrate temperatures with 0.24% nitrogen addition, or coupled effect of nitrogen addition and temperature on the growth of CVD diamond films happened. Finite element method (FEM) analysis was employed to simulate the temperature gradient and distribution on these two samples, and based on this simulation and other simulation results in the literature, the growth mechanism is briefly discussed.

In the paper, under 5.6 GPa and 1200-1400℃, the type Ib diamond single crystals on defect-free[111] -oriented seed crystals are synthesized in a cubic anvil under high pressure and high temperature when the crack problem of diamond single crystal appears frequently. Highpurity Fe-Ni-Co solvents are chosen as the catalysts. Highpurity graphite powder (99.99%, purity) is selected as a carbon source. The effects of cooling process on the qualities of Gem-diamond single crystals are studied carefully. First, in order to study the common crack defects of diamond single crystals, using scanning electron microscope (SEM), the surface morphologies of high quality diamond single crystals and crack crystals are obtained respectively. Our SEM test results show that the surfaces of the crack crystals and the high quality crystals are all very smooth. Therefore, the crack crystal problem is not directly caused by the unordered accumulation of carbon. Second, the concentrations of nitrogen in the high quality diamonds and crack crystals are measured by Fourier transform infrared. In our studies, the nitrogen content of the diamond single crystal with crack is similar to the nitrogen content of high quality single crystal, so the appearance of crystal crack is not caused by high impurity content. According to the test results and the regularity of the occurrence of crack crystals, the reasons for the occurrence of crack crystals are analyzed seriously. When the weather conditions such as seasonal change, wind, rain or snowfall are not very stable, the probability of crack crystal problem to appear will increase greatly. In our opinion, the decrease of diamond crystal quality caused by the fluctuation of external growth conditions is the internal cause of crack crystal problem appearing. After growing diamond crystals, choosing the traditional power failure mode and slowing cooling process respectively, the effect of cooling process on the quality of diamond single crystal is investigated. In the season of the crack problem occurring frequently, choosing power failure cooling process, cracks appear in both diamond crystals with 1.3 mm or 6.0 mm in diameter. With the slow cooling process, the synthetic diamond crystals with 1.2 mm or 5.8 mm in diameter are all high-quality single crystals with no cracks inside. The research results show that the slow cooling process can effectively restrain the occurrence of crack crystal problems. In addition, the mechanism problems of crack crystals and the mechanisms of the effects of slow cooling process on diamond crystal qualities are discussed in detail. We believe that the slow cooling process is effective in solving the crack crystal problem, which is mainly attributed to the following two aspects:on the one hand, the slow cooling makes the internal stress of diamond single crystal growing effectively released, which improves the compressive strength of the crystal and the crystal quality as well; on the other hand, the slow cooling makes the solidification process of the catalyst melt slowly, which provides enough time for the crystal to balance the external stress of the catalyst and the equipment, so that the crystals, which are not affected by the unbalanced external stress, are not cracked.

A spectral beam combination(SBC) system with dual Multi-Layer Dielectric(MLD) grating dispersion compensation configuration, which can combine multiple fiber lasers into a common aperture beam with high beam quality and relax the linewidth requirement of the individual fiber laser, has become gradually one of the most important technique route of fiber laser beam combining. The basic principle and the key technologies of the SBC system with dual-MLD-grating configuration were introduced and analyzed briefly. The recent progress of the main key technologies about high power beam combinable narrow linewidth fiber laser, high power high efficiency short wavelength narrow linewidth fiber laser, large dispersion high efficiency MLD grating and high integration dense beam combining were reviewed. The recent progress on the key technologies of SBC with dual-MLD-configuration in Institute of Applied Electronics, China Academy of Engineering Physics, were also presented. The potential of the SBC with dual-MLD-configuration was prospected.

Based on the model of multi-layer beam and the assumption of micro-inhomogeneity of material, the 3D fractural characteristics of laminated ceramic composites have been studied with numerical simulation. Under three-point bending load, crack initiation, coalescence, propagation, tuning off in the weak interface and final rupture have been simulated. The spatial distribution and evolution process of acoustic emission are also presented in the paper. The simulation verifies the primary mechanism of the weak interface inducing the crack to expand along there and absorbing the fractural energy. The disciplinary significance of the effect of strength and properties of material on the toughness and strength of laminated ceramic composites is, therefore, discussed in this paper.

In this paper, based on the self-reproduction condition of laser wavefront curvature, the influences of disk defocus on laser parameters can be calculated. The laser-pumping overlapping efficiency will decrease by 9%; the magnification will rise to 2.3, and the intra-cavity loss will be high to 30% due to a laser beam size mismatch when each disk has focal length of -100 m in a positive-branch confocal unstable resonator containing four disks with magnification of 1.8. Therefore, the optical conversion efficiency and stability will be reduced significantly. Several methods defocus compensation of are compared, it can be found that inserting variable-focus lens in resonant is useful in large dynamic range. In experiment, the defocus values are measured in different pumping power. A lens group, used for compensate components according to the single pass probe, is carefully designed. Under this compensation, the pulse energy can be maintained in 10 J from 1 Hz to 100 Hz. The output power can be improved 2.33 times compared to non-compensation condition.

In this paper, we investigated the performance of the single fuel cell with four gas diffusion electrodes with differently structured Pt–Ru electro-catalyst layers, as deposited by sputtering. The effects of the structural design of the Pt–Ru catalyst are discussed with reference to I–V polarization curves. Experimental results indicate that the performance of the fuel cell was affected by the microstructure of the sputter-deposited Pt–Ru layers on the E-TEK carbon clothes electrodes, the gas pressure, the operating temperature and the internally humidified temperatures. In the study range, the performance of the fuel cell is improved as the gas pressure, operating temperatures and the internal temperature increased. The measured I–V polarization curves reveal that the best performance of the designed layer electrodes was exhibited by model II with Pt/Ru multilayers, at a gas pressure of 200 KPa, a fuel cell operating temperature of 70 °C and an internally humidified temperature of 60 °C. The efficiencies of single cells with various structural designs follow the descending order model II, model III, model IV and model I.

Hybrid density functional theory (DFT) calculations are performed to study MC2 (M= V, Cr, Fe and Co) clusters in the neutral and anionic charge states. We find that the equilibrium geometries of MC2 and their anions are all cyclic structures with C2v symmetry, which agrees well with the previous theoretical studies. The Mulliken charge and spin populations of MC2 clusters and their anions are also calculated, and it is found that the electron charge transformations from anions to neutral molecules mainly take place on the M atoms. Time-dependent DFT is used to calculate the excited states, and a theoretical assignment for the features in the experimental photoelectron spectrum is given, which are in good agreement with the available experimental data.

Based on an essential assumption of meso-heterogeneity of material, the macro characteristic of composite reinforced with particles, the crack initiation, propagation and the failure process in composite were studied by using a numerical code. The composite is subjected to a uniaxial tension, and stiff or soft particles are distributed at random manner but without overlapping or contacting. The effect of reinforcement particle properties on the fracture process and mechanism of composite with brittle matrix, furthermore, the influence of the particle volumetric fraction is also investigated. Numerical results present the different failure mode and re-produce the crack initiation, propagation and coalescence in brittle and heterogeneous matrix. The mechanism of such failure was also elucidated.

In this work, the combinations of TiAl-doped DLC (Diamond-like Carbon) and TiAlN/TiN double-layered films were designed to deposit on the tool steels using cathodic arc evaporation in a single process. The economic advantage in depositing the combined coating in one production scale PVD coating system is of practical importance. The TiAl-doped DLC as lubricant coatings were synthesized with TiAl-target arc sources to emit ion plasma to activate acetylene reactive gases. Scanning electron microscopy (SEM), Auger electron spectroscopy (AES), micro-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) techniques were employed to analysis the microstructure properties of TiAl-doped DLC coatings. Vicker's and tribometer tester were used to measure the mechanical properties of TiAl-doped DLC coatings. The results show that the TiAl-doped DLC coatings retained lower friction coefficient at approximately 0.15 during the steady state sliding. The lubricity and wear resistance of TiAl-doped DLC coatings is then demonstrated to potentially be applied to the cutting tools with no lubricants.

The impermeability mechanism of water-proof self-compacting concrete (WPSCC) was studied. The mechanism and influential factors, such as water-cement ratio (w/c), dosage of powder, superplasticizer, sand content, aggregate content, fly ash, UEA, PP fiber, on compactibility and crack resistance of WPSCC were analyzed. A type of WPSCC successfully applied in tunnel liner with its validities, conveniences and economies by mockup test was developed and optimized. Experimental results show that the WPSCC has good workability, mechanical properties and impermeability when reasonable requirements are fulfilled.

This paper examines the modelling of a 1.6 kW, 3,000 rpm surface permanent magnet machine which was constructed using soft magnetic composites (SMC) stator tooth segments and a bonded rare-earth magnet ring. It was designed for high torque density and efficiency, and low cogging torque. Both 2D and 3D finite-element model results are provided and compared to the experimental measurements of the flux densities, back-EMF, cogging torque, inductance and power losses. Challenges were found in modelling the magnetization of the bonded-ring magnet. The rated efficiency and field-weakening performance are examined by using both measured and finite-element calculated parameters.

A high power multi-pass diode-pumped solid-state MOPA system with large core diameter tapered quartz fiber as phase conjugator is experimentally investigated. The results of the effects of laser longitudinal mode characteristic, laser pulse width and fiber surface optical quality on SBS reflectivity are presented. Maximum SBS reflectivity of 69.7% is obtained with the repetition rate of 1000 Hz, input pulse energy of 38mJ and pulse width of 24 ns. The phase conjugator is made from a taper shaped quartz fiber with the diameter of 1mm at the input end and 0.4mm at the other end. It has good application prospects in improving the beam quality and compressing the pulse width for high power laser system with high repetition rate.