Changchun, China
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Ma S.,CAS Changchun Observatory | Wang Q.,Institute of Meteorological Science of Jilin Province | Yu H.,Agrometeorological Observatory of Yushu County | Xu L.,Agrometeorological Observatory of Yushu County | Zhang T.,Agrometeorological Observatory of Yushu County
Journal of Natural Disasters | Year: 2012

This paper studies the influence of spring drought on maize yield based on the combination tests of soil water stress test and field test of seeding trials. Results show that during the corn planting and emerging periods, the relationship between soil water content and corn yield follows a quadratic function. Spring water stress of soil on maize yield is very obvious. In field water capacity, soil humidity declied by 1 percentage points each, maize yield will be reduced by about 7% ; soil effective water reduction for every 10 mm,per unit area yield will drop about 14%. The article also identified maize drought index of soil moisture. The influence of soil moisture decrease on the corn yield was quantitatively studied. The indicator and mode of soil moisture influence on maise yield can be used for developing the assessment and prediction of maize spring drought, and can also be used to determine drought-resistant irrigation content.

Sui N.,Jilin University | Li M.,CAS Changchun Observatory | He P.,Jilin University | He P.,Peking University | He P.,CAS Institute of Theoretical Physics
Monthly Notices of the Royal Astronomical Society | Year: 2014

In this work, we investigate the statistical computation of the Boltzmann entropy of statistical samples. For this purpose, we use both histogram and kernel function to estimate the probability density function of statistical samples. We find that, due to coarse-graining, the entropy is a monotonic increasing function of the bin width for histogram or bandwidth for kernel estimation, which seems to be difficult to select an optimal bin width/bandwidth for computing the entropy. Fortunately, we notice that there exists a minimum of the first derivative of entropy for both histogram and kernel estimation, and this minimum point of the first derivative asymptotically points to the optimal bin width or bandwidth. We have verified these findings by large amounts of numerical experiments. Hence, we suggest that the minimum of the first derivative of entropy be used as a selector for the optimal bin width or bandwidth of density estimation. Moreover, the optimal bandwidth selected by the minimum of the first derivative of entropy is purely data-based, independent of the unknown underlying probability density distribution, which is obviously superior to the existing estimators. Our results are not restricted to one-dimensional, but can also be extended to multivariate cases. It should be emphasized, however, that we do not provide a robust mathematical proof of these findings, and we leave these issues with those who are interested in them.

Zhang Z.,Changchun University of Science and Technology | Zhang Z.,CAS Changchun Observatory | Wang Z.,Changchun University of Science and Technology | Wang Z.,University of Bedfordshire | And 4 more authors.
Journal of Laser Applications | Year: 2014

Silicon surface structures with excellent antireflection property arouse wide interest. Chemical and physical methods such as femtosecond, nanosecond, and picosecond laser processing, wet-chemical etching, electrochemical etching, and reactive ion etching have been developed to fabricate them. However, the methods can only produce a quasi-ordered array of sharp conical microspikes on silicon surface. In this paper, we present a method to fabricate periodic silicon antireflection surface structures using direct four-beam laser interference lithography (LIL). With 1 atm ambient atmosphere of SF6 and the laser fluence of the four beams irradiated on the silicon surface at 0.64 J cm-2, the periodical conical spikes were generated. Changing the polarization directions of the opposite incident beam pairs in a four-beam LIL system could convert conical spikes structure into an array of holes. Antireflection in a wide spectral range was measured by a spectrophotometer from ultraviolet to near-infrared. The average reflectance of this periodic black silicon surface is less than 3.5%. © 2014 Laser Institute of America.

Xu Y.,CAS Changchun Observatory | Liu G.-Z.,Jilin University | Wang H.-Y.,Jilin University | Ding W.-B.,Bohai University | Zhao E.-G.,CAS Institute of Theoretical Physics
Chinese Physics Letters | Year: 2012

Within the framework of the relativistic mean field theory, we investigate the 1S 0 superfluidity (SF) of Λ hyperons in neutron star (NS) matter including σ* and mesons. The energy gap of Λ hyperons is calculated with the Nijmegen one-boson-exchange potentials for a ΛΛ pair. The parameter set we use is in line with the recent experimental data ΔB ΛΛ∼1.01±0.20 +0.18 -0.11MeV. It is found that with σ* and mesons the pairing energy gap Δ F of Λ hyperons and the corresponding SF critical temperature T CΛ; are suppressed. In addition the NS mass range of Λ hyperon SF is enlarged obviously. © 2012 Chinese Physical Society and IOP Publishing Ltd.

Jin W.,Xidian University | Wu J.,China Research Institute of Radiowave Propagation | Wu Z.,Xidian University | Liu Y.,China Research Institute of Radiowave Propagation | Sun M.,CAS Changchun Observatory
Dianbo Kexue Xuebao/Chinese Journal of Radio Science | Year: 2012

This paper proposes that space debris could be observated by using the Europe Incoherent Scatter (EISCAT-UHF) radrar. A special observation model for the space debris was developed to measure the radar cross section(RCS). Recorded raw sample data used the standard EISCAT radar receiver, and the transmission sample signal with match function(MF) analysis is needed from the simulation based on the constant experiment code. The debris RCS diversity using the location of a debris object in radar beam is analyzed. According to the forecast debris model of National Astronomical Observatories Chinese Academy of Sciences and the theoretical antenna pattern, the revised RCS measurements are found to have some extents with the debris value from U S Space Surveillance Network(SSN). The result of the present work confirms that ionosphere observation raw data could provide debris parameter and the revised RCS could provide high precision RCS value.

Li Z.-W.,CAS Changchun Observatory | Yang W.-B.,CAS Changchun Observatory | Zhang N.,CAS Changchun Observatory
Chinese Optics | Year: 2015

In order to improve the static pointing accuracy of level mounting optoelectronic telescope, the static pointing models are presented after theoretical analysis and experimental research, and modified model for level mounting optoelectronic telescope is established. First, spherical harmonic function model and modified model for level mounting optoelectronic telescope are introduced. Then 70 stars from Tycho-2 scattered uniformly in the sky were selected to be measured, and the discrete values of the 70 stars' pointing errors were gained in longitude and latitude dimensions, respectively. Finally, the coefficients in the total pointing error model were obtained by least square fitting method. Experimental results indicate that pointing precision of level mounting optoelectronic telescope can be improved from 152.10″ (without modified model) to 4.76″ (with modified model). The modified model for level mounting optoelectronic telescope can satisfy the requirements in general design, which can be widely applied in science and engineering field. © 2015, Editorial Office of Chinese Optics. All right reserved.

Ma S.,CAS Changchun Observatory | Wang Q.,Institute of Meteorological Science of Jilin Province | Lu H.,National Meteorological Center | Xu L.,Agrometeorological Observatory of Yushu County of Jilin Province | And 2 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2012

Maize emergence speed and the emergence rate relate to soil moisture and air temperature, and they largely determine the corn growth and yield. In order to obtain the relationships between seedling emergence speed, seedling rate of spring maize (Zea mays) and soil moisture and air temperature respectively, the experiments of water stress and by-stage sowing for spring maize were conducted at an agro-meteorological experiment station in the central part of Northeastern China. In an artificial rain-proof cover, 4 water treatments (not drought, light drought, drought and severity drought) and 3 sowing treatments (early, middle and late) were set to create soil moisture variation and air temperature difference during the period from sowing to germination. And soil moisture, water amount for irrigation, rainfall, air temperature, the seedling stage and emergence rate were observed. The results showed that the relationships between soil moisture and emergence rate, period of emergence both were significantly quadratic function during the periods of sowing and emerging. Below field capacity, the greater soil moisture was, the faster the corn came out and the higher the emergence rate was. Soildrought delayed the period of emergence and decreased emergence rate. Low temperature slowed down the emergence, but had little effect on emergence rate. The equation of relationship between days from sowing to emerging (D), soil moisture (S) at a depth of 0 to 20 cm and average air temperature (T) was D = 63. 450-1. 194S -1. 442T. The equation of relationship between emergence rate (P), S and T was P =5. 107 S +1. 857 T-56. 5. Combinational influence indexes of average soil moisture, effective soil water (H) and air temperature on maize emergence speed were that corn emerged quickly when 25% >S>21%, 70 mm>H>45 mm and T>18°C; it would emerge normally when 21% >S>18%, 45 mm>H> 35 mm and 18°C >T>16. 5°C; and it would emerge slowly when 18% >S>16%, 35 mm>H> 25 mm and 16. 5 °C >T>15. 5 °C; and the emergence was postponed remarkably when S<16%, H<25 mm and T<15. 5 °C. Germination rate depended mainly on soil moisture in this study. The highest germination rate (more than 95%) occurred when S >85% and H > 50mm; the higher one (about 90%) when relative humidity was about 80% and 50 mm>H>40 mm; and the lower one when relative humidity was less than 70% and 50 mm>H>40 mm; and the one was less than 65% when relative humidity was less than 60% and H<30 mm, and the serious drought happened.

Huang X.-L.,CAS Changchun Observatory | Huang X.-L.,Jilin University | Xu Y.,CAS Changchun Observatory | Liu C.-Z.,CAS Changchun Observatory | Liu G.-Z.,Jilin University
International Journal of Modern Physics D | Year: 2016

The 1S 0 nucleon superfluidity in neutron star matter was investigated in the framework of relativistic σ-ω-π-ρ model with the tensor couplings of ω and ρ mesons using the relativistic Hartree-Fock (RHF) approximation. It was found that the tensor couplings of ω and ρ mesons lead to a clear growth of the 1S 0 neutron pairing gap in the density range where there exists 1S 0 neutron superfluidity. The 1S 0 pairing gap of proton with the tensor couplings of ω and ρ mesons in the density range of ρB = 0.0-0.079fm-3 is lower and then in the density range of ρB = 0.079-0.383fm-3 higher than the corresponding value without the tensor couplings of ω and ρ mesons. Our results provide a basic to understand the influence of the tensor couplings of ω and ρ mesons on the cooling properties of neutron star. © 2016 World Scientific Publishing Company.

Ma L.,CAS Changchun Observatory | Cao D.,CAS Changchun Institute of Optics and Fine Mechanics and Physics | Liu C.,CAS Changchun Observatory
Guangdian Gongcheng/Opto-Electronic Engineering | Year: 2015

The surface-profile precision of lens is a main factor which influences the performance of the optical system. There are three main reasons which influence the lens surface-profile most, and they are the supporting structure, gravity and thermal load. In order to achieve the goal of getting high surface-profile precision of the lens (Φ>200 mm), a new multi-points flexible supporting structure is designed. Then, the influence of gravity and thermal load with the designed structure is analyzed. The results are as follows: for the deformation caused by gravity, the surface root-mean-square (RMS) value is 6.78 nm and 3.46 nm for the upper and lower surface respectively; for the deformation caused by thermal load, the surface (RMS) value is 8.30 nm and 5.57 nm for the upper and lower surface respectively. The designed structure with multi-point flexible support can effectively reduce the influence of precision loss which is caused by gravity and thermal load, and meet the requirements of high surface-profile precision of large-aperture lens for transmission-type optical system(RMS<λ/50, λ=632.8 nm). ©, 2015, Chinese Academy of Sciences. All right reserved.

Li Z.-W.,CAS Changchun Observatory | Zhang T.,CAS Changchun Institute of Optics and Fine Mechanics and Physics | Zhang N.,CAS Changchun Observatory | Sun M.-G.,CAS Changchun Observatory
Guangxue Jingmi Gongcheng/Optics and Precision Engineering | Year: 2015

A high precision orientation method for faint space objects was presented to improve the positioning accuracy of this kind of space objects in photoelectric reconnaissance. Several relevant algorithms were investigated, such as star centroid computing, star pattern matching, correction models for static pointing of optoelectronic telescope, and the astronomical orientation of space objects. The star centroid computing method and star identification using triangle algorithm were firstly analyzed. Then, the Tycho-2 catalog and basic parameter pointing model were used to correct the static pointing error of the optoelectronic telescope. Finally, by considering lower orientation precision of faint space objects, the high precision orientation algorithm of faint space objects was presented based on the improved traditional astronomical orientation method to realize the high precision orientation of space objects. Experimental results indicate that the measuring precision of the high precision orientation method for faint space objects is superior to 4″, which satisfies the system requirements of faint space object surveillance for the precision and stabilization. ©, 2015, Chinese Academy of Sciences. All right reserved.

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