The crop types and agricultural characteristic are reconstructed using the archaeobiological proxies of pollen, seed and phytolith at Xishanping site in Gansu Province between 5250 and 4300 cal a BP. The agricultural ...The crop types and agricultural characteristic are reconstructed using the archaeobiological proxies of pollen, seed and phytolith at Xishanping site in Gansu Province between 5250 and 4300 cal a BP. The agricultural activity strengthened in Xishanping from 5100 cal a BP. It appeared the earliest cultivation of prehistoric rice in the most northwest China at 5070 cal a BP. The sudden disappearance of conifers and expansion of chestnut trees is likely to be the result of selective hewing of conifers and cultivation of chestnuts at about 4600 cal a BP. There existed 8 crop types of foxtail millet, broomcorn millet, rice, wheat, barley, oats, soybean and buckwheat at Xishanping between 4650 and 4300 cal a BP, which cover the main crop types of the two origin centers of East and West Asia. Not only has the wheat and barley been approved to spread to northwestern China, but the earliest complexity agriculture in Neo-lithic China appeared in Tianshui, Gansu Province.展开更多
Pulse echo accumulation is commonly employed in coherent Doppler wind LiDAR(light detection and ranging)under the assumption of steady wind.Here,the measured spectral data are analyzed in the time dimension and freque...Pulse echo accumulation is commonly employed in coherent Doppler wind LiDAR(light detection and ranging)under the assumption of steady wind.Here,the measured spectral data are analyzed in the time dimension and frequency dimension to cope with the temporal wind shear and achieve the optimal accumulation time.A hardware-efficient algorithm combining the interpolation and cross-correlation is used to enhance the wind retrieval accuracy by reducing the frequency sampling interval and then reduce the spectral width calculation error.Moreover,the temporal broadening effect and spatial broadening effect are decoupled according to the strategy we developed.展开更多
A tightly linked dual ring antenna is designed,and it is specifically tailored for uniformly coupling the microwave magnetic field to the nitrogen-vacancy(NV)center.The designed antenna operates at a center frequency ...A tightly linked dual ring antenna is designed,and it is specifically tailored for uniformly coupling the microwave magnetic field to the nitrogen-vacancy(NV)center.The designed antenna operates at a center frequency of about 2.87 GHz,with a bandwidth of around 200 MHz,allowing it to address multiple resonance peaks in the optically detected magnetic resonance(ODMR)spectrum in an external magnetic field.Moreover,the antenna generates a fairly uniform magnetic field in a range with a radius of 0.75 mm.High resolution imaging of the magnetic field distribution on the surface of the antenna is conducted by using a fiber diamond probe.We also investigate the effect of magnetic field uniformity on the linewidth of ODMR,so as to provide insights into reducing the inhomogeneous broadening of ODMR.展开更多
Our study shows that for the copropagating probing and driving fields, the gain without inversion doesn't monotonously decrease or increase with the increasement of Doppler width. When the driving field is resonan...Our study shows that for the copropagating probing and driving fields, the gain without inversion doesn't monotonously decrease or increase with the increasement of Doppler width. When the driving field is resonant, at a suitable Doppler width, we can get a maximum value of the gain without inversion, which is much larger than that obtained when Doppler broadening is absent.展开更多
High-performance 86μJ,11.2 fs pulses with a spectrum range of 800-1050 nm are generated based on 1030 nm,190 fs Yb femtosecond pulses by using multi-plate-based spectral broadening and filtering.Taking advantage of s...High-performance 86μJ,11.2 fs pulses with a spectrum range of 800-1050 nm are generated based on 1030 nm,190 fs Yb femtosecond pulses by using multi-plate-based spectral broadening and filtering.Taking advantage of single beam configuration,the obtained pulses have excellent power and spectral stabilities.Since the output spectrum is obtained by spectrally filtering the broadened components,the temporal contrast of the output pulses is enhanced by at least four orders of magnitude.Together with the robust and simple setup,the proposed method is expected to be a competitive option for the generation of seed pulses for 10s-100s petawatt lasers.展开更多
We have studied the effect of the spontaneously generated coherence （SGC） on gain of lasing without inversion （LWI） in a closed three-level A-type atomic system with Doppler broadening. It is shown that, regardles...We have studied the effect of the spontaneously generated coherence （SGC） on gain of lasing without inversion （LWI） in a closed three-level A-type atomic system with Doppler broadening. It is shown that, regardless of the driving and probe fields being co- or counter-propagating, at a suitable value of the Doppler width, we can obtain a much larger LWI gain with SGC than that without SGC; and the region of the LWI gain spectrum with SGC is obviously larger than that without SGC. When the Doppler width takes a constant value, the gain does not monotonically decrease or increase with increasing strength of SGC, the largest LWI gain can be obtained by adjusting strength of SGC. Generally speaking, the co-propagating probe and driving fields is favourable to obtain a larger LWI gain.展开更多
The broadening effect of stacking disorder in hexagonal graphite is found experimentally by XRD to be identical to that of stacking faults in hexagonal-closed-packing(HCP) structure,which has obvious selective broaden...The broadening effect of stacking disorder in hexagonal graphite is found experimentally by XRD to be identical to that of stacking faults in hexagonal-closed-packing(HCP) structure,which has obvious selective broadening effect.The Langford's method for dealing with the twofold broadening effects of the crystallite-faults in hexagonal ZnO has been extended in this paper,and then applied to the deter-mination of stacking disorder in 2H-graphite,which indicates that our extension method is convenient to both the experiments and data process,and may be generalized further.Two stacking disorder model in 2H-graphite and data processing method have been proposed in this study.The two disorder degrees of PAB and PABC can be computed when the two reliable FWHMs of 101 and 102 diffraction peaks were obtained.展开更多
The inhomogeneous broadening parameter and the internal loss of green LDs are determined by experiments and theoretical fitting. It is found that the inhomogeneous broadening plays an important role on the threshold c...The inhomogeneous broadening parameter and the internal loss of green LDs are determined by experiments and theoretical fitting. It is found that the inhomogeneous broadening plays an important role on the threshold current density of green LDs. The green LD with large inhomogeneous broadening even cannot lase. Therefore, reducing inhomogeneous broadening is a key issue to improve the performance of green LDs.展开更多
A semi-gas kinetics (SGK) model for performance analyses of flowing chemical oxygen-iodine laser (COIL) is presented. In this model, the oxygen-iodine reaction gas flow is treated as a continuous medium, and the effec...A semi-gas kinetics (SGK) model for performance analyses of flowing chemical oxygen-iodine laser (COIL) is presented. In this model, the oxygen-iodine reaction gas flow is treated as a continuous medium, and the effect of thermal motions of particles of different laser energy levels on the performances of the COIL is included and the velocity distribution function equations are solved by using the double-parameter perturbational method. For a premixed flow, effects of different chemical reaction systems, different gain saturation models and temperature, pressure, yield of excited oxygen, iodine concentration and frequency-shift on the performances of the COIL are computed, and the calculated output power agrees well with the experimental data. The results indicate that the power extraction of the SGK model considering 21 reactions is close to those when only the reversible pumping reaction is considered, while different gain saturation models and adjustable parameters greatly affect the output power, the optimal threshold gain range, and the length of power extraction.展开更多
基金Supported by the Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX3-SW-146)the National Natural Science Foundation of China (Grant Nos. 40572108, 40599423 and 40372077)the West Light Foundation of the Chinese Academy of Sciences
文摘The crop types and agricultural characteristic are reconstructed using the archaeobiological proxies of pollen, seed and phytolith at Xishanping site in Gansu Province between 5250 and 4300 cal a BP. The agricultural activity strengthened in Xishanping from 5100 cal a BP. It appeared the earliest cultivation of prehistoric rice in the most northwest China at 5070 cal a BP. The sudden disappearance of conifers and expansion of chestnut trees is likely to be the result of selective hewing of conifers and cultivation of chestnuts at about 4600 cal a BP. There existed 8 crop types of foxtail millet, broomcorn millet, rice, wheat, barley, oats, soybean and buckwheat at Xishanping between 4650 and 4300 cal a BP, which cover the main crop types of the two origin centers of East and West Asia. Not only has the wheat and barley been approved to spread to northwestern China, but the earliest complexity agriculture in Neo-lithic China appeared in Tianshui, Gansu Province.
基金Project supported by the Shanghai Science and Technology Innovation Action(Grant No.22dz1208700).
文摘Pulse echo accumulation is commonly employed in coherent Doppler wind LiDAR(light detection and ranging)under the assumption of steady wind.Here,the measured spectral data are analyzed in the time dimension and frequency dimension to cope with the temporal wind shear and achieve the optimal accumulation time.A hardware-efficient algorithm combining the interpolation and cross-correlation is used to enhance the wind retrieval accuracy by reducing the frequency sampling interval and then reduce the spectral width calculation error.Moreover,the temporal broadening effect and spatial broadening effect are decoupled according to the strategy we developed.
基金Project supported by the National Key Research and Development Program of China(Grant No.2021YFB2012600)the Shanghai Aerospace Science and Technology Innovation Fund(Grant No.SAST-2022-102).
文摘A tightly linked dual ring antenna is designed,and it is specifically tailored for uniformly coupling the microwave magnetic field to the nitrogen-vacancy(NV)center.The designed antenna operates at a center frequency of about 2.87 GHz,with a bandwidth of around 200 MHz,allowing it to address multiple resonance peaks in the optically detected magnetic resonance(ODMR)spectrum in an external magnetic field.Moreover,the antenna generates a fairly uniform magnetic field in a range with a radius of 0.75 mm.High resolution imaging of the magnetic field distribution on the surface of the antenna is conducted by using a fiber diamond probe.We also investigate the effect of magnetic field uniformity on the linewidth of ODMR,so as to provide insights into reducing the inhomogeneous broadening of ODMR.
基金This work wass,IPPorted by theN战ional Natural Science foundation of China under Grant No.69978011 and the Natural Science Foundation of Shandong Province under Grant No.Y2001A07.
文摘Our study shows that for the copropagating probing and driving fields, the gain without inversion doesn't monotonously decrease or increase with the increasement of Doppler width. When the driving field is resonant, at a suitable Doppler width, we can get a maximum value of the gain without inversion, which is much larger than that obtained when Doppler broadening is absent.
基金supported by the Shanghai Municipal Natural Science Foundation(No.20ZR1464500)the National Natural Science Foundation of China(NSFC)(Nos.61905257 and U1930115)the Shanghai Municipal Science and Technology Major Project(No.2017SHZDZX02)
文摘High-performance 86μJ,11.2 fs pulses with a spectrum range of 800-1050 nm are generated based on 1030 nm,190 fs Yb femtosecond pulses by using multi-plate-based spectral broadening and filtering.Taking advantage of single beam configuration,the obtained pulses have excellent power and spectral stabilities.Since the output spectrum is obtained by spectrally filtering the broadened components,the temporal contrast of the output pulses is enhanced by at least four orders of magnitude.Together with the robust and simple setup,the proposed method is expected to be a competitive option for the generation of seed pulses for 10s-100s petawatt lasers.
基金Project supported by the National Natural Science Foundation of China （Grant No 10675076）, the Natural Science Foundation of Shandong Province, China （Grant No Y2006A21） and the State Key Laboratory of High Field Laser Physics, Shanghai Institute of 0ptics and Fine Mechanics, Chinese Academy of Sciences.
文摘We have studied the effect of the spontaneously generated coherence （SGC） on gain of lasing without inversion （LWI） in a closed three-level A-type atomic system with Doppler broadening. It is shown that, regardless of the driving and probe fields being co- or counter-propagating, at a suitable value of the Doppler width, we can obtain a much larger LWI gain with SGC than that without SGC; and the region of the LWI gain spectrum with SGC is obviously larger than that without SGC. When the Doppler width takes a constant value, the gain does not monotonically decrease or increase with increasing strength of SGC, the largest LWI gain can be obtained by adjusting strength of SGC. Generally speaking, the co-propagating probe and driving fields is favourable to obtain a larger LWI gain.
基金Supported by the National Natural Science Foundation of China (Grant No. 20773157)
文摘The broadening effect of stacking disorder in hexagonal graphite is found experimentally by XRD to be identical to that of stacking faults in hexagonal-closed-packing(HCP) structure,which has obvious selective broadening effect.The Langford's method for dealing with the twofold broadening effects of the crystallite-faults in hexagonal ZnO has been extended in this paper,and then applied to the deter-mination of stacking disorder in 2H-graphite,which indicates that our extension method is convenient to both the experiments and data process,and may be generalized further.Two stacking disorder model in 2H-graphite and data processing method have been proposed in this study.The two disorder degrees of PAB and PABC can be computed when the two reliable FWHMs of 101 and 102 diffraction peaks were obtained.
基金supported by the National Key Research and Development Program of China(Grant Nos.2017YFB0405000,2016YFB0401803)the National Natural Science Foundation of China(Grant Nos.61834008,61574160,and 61704184)support of the Chinese Academy of Science Visiting Professorship for Senior International Scientists (Grant No.2013T2J0048)
文摘The inhomogeneous broadening parameter and the internal loss of green LDs are determined by experiments and theoretical fitting. It is found that the inhomogeneous broadening plays an important role on the threshold current density of green LDs. The green LD with large inhomogeneous broadening even cannot lase. Therefore, reducing inhomogeneous broadening is a key issue to improve the performance of green LDs.
基金supported by the National Natural Science Foundation of China(Grant No.10032050).
文摘A semi-gas kinetics (SGK) model for performance analyses of flowing chemical oxygen-iodine laser (COIL) is presented. In this model, the oxygen-iodine reaction gas flow is treated as a continuous medium, and the effect of thermal motions of particles of different laser energy levels on the performances of the COIL is included and the velocity distribution function equations are solved by using the double-parameter perturbational method. For a premixed flow, effects of different chemical reaction systems, different gain saturation models and temperature, pressure, yield of excited oxygen, iodine concentration and frequency-shift on the performances of the COIL are computed, and the calculated output power agrees well with the experimental data. The results indicate that the power extraction of the SGK model considering 21 reactions is close to those when only the reversible pumping reaction is considered, while different gain saturation models and adjustable parameters greatly affect the output power, the optimal threshold gain range, and the length of power extraction.
