CAS Changchun Observatory
CAS Changchun Observatory
Bi G.,CAS Changchun Institute of Optics and Fine Mechanics and Physics |
Ren J.,CAS Changchun Institute of Optics and Fine Mechanics and Physics |
Fu T.,CAS Changchun Institute of Optics and Fine Mechanics and Physics |
Nie T.,CAS Changchun Institute of Optics and Fine Mechanics and Physics |
And 2 more authors.
IEEE Photonics Journal | Year: 2017
Image dehazing is a challenging and highly desired technology in computer vision applications. The dark channel prior (DCP) has been considered to be an efficient dehazing technique in recent years. However, the invalidation of DCP can induce unreliable estimation of transmission, resulting in inaccurate color information recovery, halo artifacts and block effect. In this paper, a novel brightness map is proposed based on the observation on outdoor haze-free/haze images which can reflect the brightness information and the light reflection ability of the scene, furthermore, the relationship between DCP and the brightness map is given in mathematical model. The proposed algorithm can compensate for the DCP effectively, estimate the transmission map accurately, get the global atmospheric light adaptively and segment the image automatically. Using multi-scale guided filter refine transmission map, the halo artifacts are able to be avoided in the scene depth of a sudden change. A series of experiments are additionally implemented to demonstrate that the proposed algorithm can obtain high-quality haze-free images with abundant distinguished details, low color distortion and little halo artifacts which can outperform or be comparable with four state-of-the-art haze removal algorithms. OAPA
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.
An N.,CAS Changchun Observatory |
Liu C.-Z.,CAS Changchun Observatory |
Fan C.-B.,CAS Changchun Observatory |
Dong X.,CAS Changchun Observatory |
Song Q.-L.,CAS Changchun Observatory
International Journal of Modern Physics B | Year: 2017
In order to meet the design requirements of the high-performance antimonide-based optoelectronic devices, the spin-orbit splitting correction method for bandgaps of Sb-based multi-element alloys is proposed. Based on the analysis of band structure, a correction factor is introduced in the InxGa1-xAsySb1-y bandgaps calculation with taking into account the spin-orbit coupling sufficiently. In addition, the InxGa1-xAsySb1-y films with different compositions are grown on GaSb substrates by molecular beam epitaxy (MBE), and the corresponding bandgaps are obtained by photoluminescence (PL) to test the accuracy and reliability of this new method. The results show that the calculated values agree fairly well with the experimental results. To further verify this new method, the bandgaps of a series of experimental samples reported before are calculated. The error rate analysis reveals that the α of spin-orbit splitting correction method is decreased to 2%, almost one order of magnitude smaller than the common method. It means this new method can calculate the antimonide multi-element more accurately and has the merit of wide applicability. This work can give a reasonable interpretation for the reported results and beneficial to tailor the antimonides properties and optoelectronic devices. © 2017 World Scientific Publishing Company.
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.
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.