[en] Our practice proved that when the selected mutagenic doses were suitable, for example, 0.10 ∼ 0.20 kGy for high energy electron and 1 ∼ 8 x 10¹² neutrons/cm² for fast neutron, there were more high mutagenic effects. Besides the suitable mutagenic doses, the mutagenic effects were in connection with strain sensitivity, irradiation method, selection condition etc.. By electron irradiation mutagenic treatment of kanamycin strain, a new kind strain was obtained. Its potency of shake bottle has been increased 10.34 ∼ 30.8% and the production yield has been increased 4.07 ∼ 5.23%

[en] Slow light technology will play a key role in future all-optical communication. The slow-light technology based on stimulated Brillouin scattering has become a research highlight because of its additional advantages, such as compatibility of the devices with existing telecommunication systems, room-temperature operation, and tunable at arbitrary wavelengths. According to the propagation of a cw pulse through a Brillouin fiber amplifier, whose frequency is near the Stokes resonance, via three-wave coupling equations, both pump depletion and fiber losses taken into consideration, the principle of how slow-light effect based on stimulated Brillouin scattering produced and the mathematical expression of time delay are strictly deduced. A delay of 8 ns is obtained when the input Stokes pulse is 200ns and the SBS (stimulated Brillouin scattering) gain G is ∼18 in our designed experiment of SBS slow-light system. Then the extent of transformation from pump waves to Stokes waves is measured using MATLAB numerical simulation according to the experiment dates, based on the relation between output pump light power and input pump light power and also the relation between output Stokes light power and input pump light power. And the relation between the input light power and propagation distance is discussed as well. Finally the relation between slow light pulse delay and SBS gain is also obtained.

[en] Ti6Al4V alloy has broad application prospects in the aircraft industry. However, when it is served as frictional motion components, the poor friction and wear properties may greatly influence the reliability and working life of the entire mechanical system. Therefore, this paper mainly investigates the tribological performance and self-repairing functionality of Ti6Al4V-multilayer graphene (MLG)-Ag composites (TMAC) from 25 to 600 °C. The results show that TMAC obtains better tribological behavior in comparison with Ti6Al4V alloy (TC4), Ti6Al4V-MLG composites (TMC) and Ti6Al4V-Ag composites (TAC). It should be ascribed to the synergistic action of the reinforcement MLG and lubricant Ag, which are crushed and spread out by mechanical and thermal stress in the friction process, leading to the formation of a lubricating film on the wear scar. Along with the spreading of lubricating film, Ag and MLG can precipitate onto the microdefective areas, thus playing an important role in repairing the wear scar of TMAC.

[en] M50 steel is widely used in aero-engine bearings and other high-temperature bearings. However, the poor wear of M50 steel resistance restrains its further applications. In this paper, the sliding tribological behaviors of M50 steel, M50-Ag composites (MAC) and M50-Ag-TiC composites (MATC) against Si₃N₄ ball were investigated from 150 to 600 °C at 15 N-0.2 m/s. MATC showed better tribological properties in comparison with M50 and MAC. Especially at 450 °C, MATC obtained the lowest friction coefficient of 0.15 and smallest wear rate of 1.3 × 10⁻⁵ mm³ N⁻¹ m⁻¹. The excellent tribological performance of MATC during the friction test was attributed to the continuous lubricating film containing lubricant Ag and reinforcement TiC, as well as the subsurface compacted layer that could well support the lubricating film to prevent it from being destroyed. At 600 °C, because of the tribo-chemical reaction between Ag and Mo oxide during sliding process, the newly formed Ag₂MoO₄ lubricating film was well spread out on the friction surface, which could continuously improve the tribological behavior of MATC. This investigation was meaningful to improve the anti-friction and wear resistance of M50 matrix bearing over a wide temperature range.

[en] In this paper, the comparison of main performance of calibrating apparatus for emanometer is carried out between Jiangxi, Guangdong and Hubei Province for the first time. By comparing and analyzing the radon measurement value, the repeatability of measurement standard, the balance control ability of radon supplement and the stability control ability of temperature and humidity in each laboratory, the measurement level and performance level of calibrating apparatus for emanometer are scientifically and objectively understood, which provides a foundation for the development of emanometer verification and application. (authors)

[en] An experimental research was performed to study the wear characteristics, as well as the friction-induced vibration and noise behaviors of Ni₃Al alloys (NA) and Ni₃Al metal matrix composites containing lubricant grephene nanoplatelets (NA-GNPs). Results showed that compared with NA, NA-GNPs exhibited the better tribological performance, as well as the lower amplitudes of friction-induced vibration and noise. The noise signals were closely correlated to the vibration acceleration signals. The occurrence of friction-induced vibration and noise was attributed to friction interface factors, such as asperity deformation, plowing and adhesion. The worn surface of NA with the appearances of peeling and obvious micro-cracks showed high-frequency vibration and noise characteristics. However, the finer GNPs could be filled into the edge of micro-cracks and gaps to repair the worn surface with the sliding of counterpart ball, NA-GNPs exhibited low-frequency vibration and noise behaviors. Moreover, due to the migration and diffusion of GNPs, the friction layer structure was formed easily beneath worn surface of NA-GNPs, which could improve the lubricating effect. GNPs exhibited the excellent potential lubricant for improvement of tribological performance and reduction of vibration and noise. (paper)

[en] We report the discovery of Balmer broad absorption lines (BALs) in the quasar LBQS 1206+1052 and present a detailed analysis of the peculiar absorption line spectrum. Besides the Mg II λλ2796, 2803 doublet, BALs are also detected in the He I* multiplet at λλ2946, 3189, 3889 Å arising from the metastable helium 2³S level, and in Hα and Hβ from the excited hydrogen H I* n = 2 level, which are rarely seen in quasar spectra. We identify two components in the BAL troughs of Δυ ∼2000 km s⁻¹ width: One component shows an identical profile in H I*, He I* and Mg II with its centroid blueshifted by −υ_c ≈ 726 km s⁻¹. The other component is detected in He I* and Mg II with − υ_c ≈ 1412 km s⁻¹. We estimate the column densities of H I*, He I*, and Mg II, and compare them with possible level population mechanisms. Our results favor the scenario that the Balmer BALs originate in a partially ionized region with a column density of N_H ∼ 10²¹ − 10²² cm^-2 for an electron density of n_e ∼ 10⁶ − 10⁸ cm^-3 via Lyα resonant scattering pumping. The harsh conditions needed may help to explain the rarity of Balmer absorption line systems in quasar spectra. With an i-band PSF magnitude of 16.50, LBQS 1206+1052 is the brightest Balmer-BAL quasar ever reported. Its high brightness and unique spectral properties make LBQS 1206+1052 a promising candidate for follow-up high-resolution spectroscopy, multi-band observations, and long-term monitoring.

[en] In order to improve the tribological perofrmance of Ni₃Al metal matrix composites, the effects of preparation process on the friction and wear behaviors are investigated. Ni₃Al self-lubrication metal composites (NMCs) containing 2.0 wt% graphene nanoplatelets (GNPs) were prepared by laser melting deposition (NA-LMD) and sparking plasma sintering (NA-SPS). Rotating sliding tests under different applied loads are conducted to study the friction and wear behaviors. The results show that, compared with NA-SPS, GNPs can be well integrated with NA-LMD substrate whose microstructure is more compact, which is attributed to the sufficient alloying reaction, as well as the layer and layer deposition principle of laser technology. Due to the excellent toughness and strength, the worn surfaces of NA-LMD after tests exhibit smooth and flat morphologies and have no significant pits and microholes. The more dense and thick tribo-layer without significant material deformation is formed beneath the worn surface of NA-LMD to improve the wear resistance performance. Whereas the mechanical properties of NA-SPS become poor due to the uncompacted microstructure and the existence of microholes caused by insufficient alloying reaction. Therefore, the friction coefficients and wear rates of NA-LMD are lower than those of NA-SPS when under the role of heavy and repeated sliding contact loads. (paper)

[en] Friction noise is a common problem in the industrial field. It not only affects the accuracy and service life of system, but also damages the environmental comfort. In this paper, Ti₃SiC₂ is added to M50 matrix composites for reducing friction noise. The characteristics of friction noise signal, worn surface and cross-section morphology of wear scar are analyzed. The cause of friction noise is explored, and the influence of Ti₃SiC₂ on friction noise is revealed. The results show that the addition of Ti₃SiC₂ significantly improves the wear condition of contact surface, decreases the noise intensity level and suppresses the high frequency components. Especially when the Ti₃SiC₂ content is 10 wt%, the effect is more pronounced. The generation of friction noise is due to energy dissipation caused by surface roughness. Ti₃SiC₂ is conducive to forming a good friction interface layer on the worn surface, which reduces surface roughness and decreases friction noise. (paper)

[en] We report that the ferromagnetic resonance (FMR) response of the CoFeB/HfO₂ heterostructures is stabilized and reversibly manipulated by ionic gel. Ionic gel with excellent flexibility is used as a medium to form an electric field. When a 4 V gate voltage is applied, the resonance field H _r and peak-to-peak linewidth ΔH _pp at different angles are regulated. When θ = 20°, the H _r is regulated up to 82 Oe. When θ = 70°, ΔH _pp is tuned up to 75 Oe. When the gate voltage is repeatedly applied, the FMR spectra can be freely switched between the initial state and the gated state. Our study provides an effective method to manipulate the damping of the magnetic film stably and reversibly. (paper)