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The rapid development of modern completely artificial light-controlled plant growth requires the light source increasingly stringent. Blue-violet phosphor with high luminous intensity and good thermal stability is the key material for plant growth. Herein, narrow-band blue-violet Zn3B2O6 : xBi3+ (0 ≤x ≤0. 03) phosphor with excellent thermal stability was synthesized by solid-state reaction. The results of XRD and energy spectra analysis show that Bi3+ successfully entered Zn3B2O6 lattice. The fluorescence spectrum of Zn3B2O6 : Bi3+ phosphor shows narrow-band blue-violet light at 430 nm (³P1~¹S0), and the full width at half maximum is only 56 nm. The optimal Bi3+ doping concentration is 0.02. According to the excitation spectrum shape and the lifetime decay behavior, it is proved that Bi3+ only occupies Zn sites in Zn3B2O6 . The emission peak intensity and integrated area of Zn3B2O6: 0.02Bi3+ phosphor at 423 K are both 85% of those at room temperature, indicating that the sample has excellent thermal stability and may have potential application in high-temperature devices. The emission spectrum of Zn3B2O6 :0.02Bi3+ phosphor accounts for 70.4% and 84.6% of the absorption spectra (370~525 nm) of chlorophyll a/ b, respectively, indicating the potential application of as-prepared blue-violet phosphors in the field of plant growth. [ABSTRACT FROM AUTHOR]

Objectives: Length of day variation (ΔLOD) predictions play an important role in tracking and navigation of deep-space detector, precise determination of artificial satellite orbit and climate forecasting. In full consideration of the time-varying characteristics of ΔLOD, we present the application of a hybrid technique for predicting ΔLOD. Methods: The ΔLOD predictions are generated by means of the combination of singular spectrum analysis (SSA) extrapolation for the linear trend, annual and semiannual oscillations in ΔLOD based on an iterative interpolation strategy, and autoregressive integrated moving average (ARIMA) stochastic prediction of SSA remaining residuals, referred to as SSA+ARIMA. In order to evaluate the effectiveness of this approach, the ΔLOD predictions up to 365 d into the future are calculated year-by-year for the 2-year period from Jan. 1,2000 to Dec. 31, 2001 using the data covering the previous 10 years from International Earth Rotation and Reference Systems Service C04 series. The prediction results are analyzed and compared with those obtained by machine learning methods such as back propagation neural network (BPNN), general regression neural network (GRNN) and Gaussian process (GP). Results: It is shown that the accuracy of the predictions are better than that by machine learning methods in terms of the mean absolute error (MAE) of predictions, especially for medium and long-term predictions. Compared with the predictions obtained by the BPNN, GRNN and GP, the MAE of the proposed SSA+ARIMA predictions up to 30 d and 365 d in future is reduced by 39% and 61%, respectively. Conclusions: The proposed method provides a new solution for ΔLOD prediction. [ABSTRACT FROM AUTHOR]

First, polyacrylonitrile/polyvinyl pyrrolidone (PAN/PVP) fibrous membrane was prepared by electrospinning, and then porous polyacrylonitrile (PPAN) fibrous membrane was obtained by water impregnation. Fourier transform infrared (FTIR) spectra and thermogravimetric analysis (TGA) were used to explore the mechanism of fiber pore-forming, and X-ray photoelectron spectroscopy (XPS) was used to study the interaction between PAN and PVP molecules in the porous fibrous membrane. At the same time, the effects of mass ratio of PAN to PVP on the morphology, surface area, wettability, mechanical properties, and oil/water separation performance of fibrous membrane were investigated, and the optimal mass ratio was determined. Results showed that when m(PAN)/m(PVP) was 1∶2, PPAN fibrous membrane showed higher mechanical properties. The separation flux of the n-hexane/water mixture was (46 318 ± 3 879) L/(m2·h·bar) (1 bar=0.1 MPa), and the efficiency was (96.01 ± 0.38)%. It also realized the efficient separation of different kinds of oil/water mixtures. In addition, PPAN fibrous membrane showed excellent cyclic separation performance, and the flux loss rate was only 8.9% after ten cycles of separation. [ABSTRACT FROM AUTHOR]

BACKGROUND: Chameleon diamond is a kind of color diamond with photochromic and thermochromic phenomenon. If the chameleon diamond is placed in a dark room or heated for a long time, it can change from greenish yellow to fancy yellow, and return to its original color when the diamond cools. Previous studies on chameleon diamond mainly focus on spectral characteristics. Through testing a large number of samples, the gemological and spectral characteristics of chameleon diamond are summarized. The characteristics of chameleon diamond, including persistent yellow phosphorescence, 480nm absorption band, mainly the A-aggregate of nitrogen, and proposed a model to explain the thermochromic and photochromic phenomenon of chameleon diamond.The characteristics of chameleon diamond discovered by previous studies are also found in a few yellow diamonds. Diamonds colored by the 480nm band shows yellow fluorescence and phosphorescence under short wave ultraviolet light, low nitrogen content, high concentrations of defects related to hydrogen and nickel, but no obvious thermochromic and photochromic phenomena. Previous studies of the chameleon diamond and similar yellow diamonds were separated and did not compare the two similar diamonds. OBJECTIVES: To ascertain the difference of spectral characteristics and defect types between chameleon diamonds and similar yellow diamonds and then analyze the causes of thermochromic phenomenon of chameleon diamond, and have a deeper comprehend of the possible structure of the center responsible of the chameleon effect. METHODS: Firstly, two chameleon diamond samples and four similar yellow diamond samples were collected to observe the color changes of the diamonds before and after heating. Top illumination and scattering illumination were used to observe the internal characteristics and color distribution of the samples. The fluorescence and phosphorescence characteristics of diamonds at long wave （365nm） and short wave （254nm） were observed by ordinary fluorescent lamp. The fluorescence and phosphorescent characteristics and growth structure of the samples under ultra-violet light were observed by Diamond View MT. Secondly, in order to investigate the causes of thermochromism in chameleon diamond, the absorption characteristics of diamond samples in the range of ultraviolet visible light were collected before and after heating, and compared with those of similar yellow diamonds. Analyze the differences in absorption spectra between chameleon diamond and similar yellow diamond, explore the causes of thermochromic phenomena. Finally, infrared spectrometer was used to collect the infrared spectrum of diamond samples and analysis of the types and impurity elements of diamond samples. Through the comparative analysis of the infrared spectrum of samples, the differences in the types and contents of nitrogen and hydrogen impurities between chameleon diamond and similar yellow diamond were obtained.The laser Raman spectrometer was used to collected PL spectra of the samples at liquid nitrogen temperature by using 473nm,532nm and 830nm lasers. By comparing the PL characteristics of chameleon diamond and similar yellow diamond, the differences between the two defects were obtained. RESULTS: The color distribution of the 6 diamond samples was uniform. After heating, the chameleon diamond samples changed color from yellow-green to yellow, similar yellow diamonds had no obvious color change. Under long and short wavelength UV light, the samples were yellow fluorescence without phosphorescence. The performance of the samples in this study is consistent under long and short wavelength ultraviolet light, but it is different from the previous study results that the chameleon diamond has persistent yellow phosphorescence, which further indicates that the chameleon effect is not directly related to the phosphorescence. Under ultra-violet light, the samples were all green fluorescence with irregular patterns which were markedly similar to diamonds colored by the480nm band. Chameleon diamonds showed moderate green phosphorescence. All the samples have C defect absorption continuum combines with of 480nm absorption band. The specific wide absorption band of 650-800nm is obvious in chameleon diamond. After being heated, the 480nm and 650-800nm absorption band of chameleon diamond completely disappeared. However, the 480nm absorption band of similar yellow diamonds is weakened or has no obvious change. Therefore, the poor thermal stability of 480nm and 650-800nm absorption band is responsible for the thermochromic phenomenon of chameleon diamonds. The infrared absorption characteristics of chameleon diamond mainly show A-center absorption, isolated nitrogen and hydrogen-related features can be seen. In addition to the characteristic 1430cm-1 wide absorption which has a different origin than the platelet-related1430cm-1 feature in Cape diamond. The similar yellow diamond has higher nitrogen content, and the degree of nitrogen aggregation is higher, and does not show any type Ib character. The broadband emission of all samples occurred mainly as one band centered at 700nm, this band consists of a dozen of peaks from 595nm to 725nm in steps of about 10nm.Additionally sharp peaks at 753,771,799,818,838,845nm present in the chameleon diamond samples. This spectrum is virtually identical to that reported previously for diamonds containing the 480nm absorption band. Chameleon diamonds and similar yellow diamonds all contain nitrogen-vacancy, nickel-nitrogen related defects, but the amount of defects are different. Chameleon diamonds cannot be effectively distinguished based on the PL spectral. The PL spectrum analysis showed that the nickel impurity was responsible for the green fluorescence of the samples under ultra-violet light. CONCLUSIONS: This study focuses on the comparative analysis of gemology, UV-visible absorption, infrared absorption and photoluminescence characteristics of chameleon diamond and its similar yellow diamond. Chameleon diamond is Ia diamond, the total nitrogen, as well as the A-center concentration, is relatively low, and show some type Ib character, such as 1240cm-1 absorption. Chameleon diamond has 480nm and 650-800nm absorption bands, that were responsible for chameleon effect. The characteristics of chameleon diamond in this study are roughly same as those in previous studies. Absorption bands of 650-800nm and absorption peaks of1430cm-1 （unrelated to platelet） are the main differences between the chameleon diamond and similar yellow diamond sample. It is inferred that the absorption band of 650-800nm and the absorption peak of 1430cm-1 are related to the center causing the thermochromic phenomenon. Although similar yellow diamond samples also have 480nm center, their thermal stability is different from that of chameleon diamonds. The reason for this phenomenon is unknown, therefor further studies are needed. [ABSTRACT FROM AUTHOR]

Objectives: Backscatter coefficient (σ 0) is one of observations of satellite radar altimetry, which is widely used in the processes of surface state monitoring, snow thickness inversion, data calibration and verification of satellite altimeters, and other fields. The geophysical data record data of Jason-2 is used to extract and isolate the Ku-band σ 0 data of the Tibetan Plateau (TP). Methods: Taking the GlobeLand30 2020 version data as the basis for surface classification, σ 0 is given surface attributes by latitude and longi‑ tude data. And we obtain the time-varying sequences of σ 0 under different types of surface features from De‑ cember 2008 to September 2016. The singular spectrum analysis principle is used to extract the σ 0 time change trend and period information, and the period results are analyzed by fast Fourier transform. Results: The results show that the σ 0 is higher in waters and wetland areas, and is lower in permanent snow and ice areas. There are multiple period signals of σ 0 in the TP. Conclusions: The surface properties of the artificial surfaces, bare land, and shrubland area are stable, and the annual σ 0 change is not significant. The other re‑ gions have significant annual and semi-annual cycles of σ 0 variability, and the amplitude of variability is not consistent across regions, with different regions corresponding to different changes in σ 0 trends. [ABSTRACT FROM AUTHOR]

Global navigation satellite system reflectometry(GNSS-R)has shown great potential in surface and marine environment parameters monitoring, with the advantages of extensive data sources, low cost, high spatial and temporal resolution, and has become an important approach for sea surface height(SSH)inversion. The existing research mainly focuses on the short-term GPS sea surface inversion within 3-6 months, which is difficult to reflect the seasonal variation and interannual characteristics of SSH. Meanwhile, only the influence of vertical velocity is considered in the dynamic sea surface correction, and the vertical acceleration of sea surface fluctuation is ignored, resulting in the poor estimation accuracy of low and high tide levels. For the above issues, a shore-based tracking station BRST in France was taken as an example, and the reflected signals of 3 consecutive years from BDS/GPS/GLONASS/Galileo system were used to estimate SSH. Based on Lomb-Scargle spectrum analysis and second-order dynamic tide level correction model, a robust regression strategy was adopted. The estimation results were compared with tide gauge records to analyze the trend of sea level change. The results show that the inversion results of GNSS-R technology are in good agreement with tide gauge records, and the inversion accuracy has a tendency to improve year by year, with a root mean square error(RMSE)of 7.57 cm and a correlation coefficient of 0.935 for the three-year daily average; the seasonal variation of SSH is obvious, the average SSH is high in autumn and winter, and low in summer, and the seasonal variation of SSH is opposite to that of temperature; the differences of amplitude for nine tidal constituents including M2, S2, K1, O1, N2, K2, P1, Q1 and M4, range from 0.06 cm to 6.76 cm with the mean absolute error(MAE)of 1.60 cm, and the differences of phase range from 0.03° to 6.96° with the MAE of 2.45°. It is further verified that the reliability of GNSS-R technology in monitoring SSH change in the frequency domain. [ABSTRACT FROM AUTHOR]

This paper considered the Schrödinger equation with different types of nonlocal integral term coefficients. By using the algebraic analysis method and the spectrum theory of differential equations, the existence of solutions was transformed into the existence of roots for some algebraic equations, the shape of the corresponding curve for the solution of the one-dimensional case. Compared with the results on the existence of solutions in the references, improved results were derived with the help of simpler methods. In order to promote the combination of theory and practice, as the auxiliaries, some curves of solutions were set in the progress of proving main results. [ABSTRACT FROM AUTHOR]

Single-view 3D reconstruction based on deep learning is a research hot spot at present. In order to discover more high-frequency details, SDF-SRN algorithm introduces positional encoding, but neural network is easy to overfit without accurate supervision, and reconstructs uneven surface. To solve the problem, this paper proposed the network model based on sparse feature. The model enabled the network that preferred to overfitting to predict high-frequency residual by residual learning. The feature extraction network extracted sparse features and the global features. Then one hypernetwork took the sparse features as input and generated prediction shallow head. This shallow head predicted low-frequency part of signed distance function. Another hypernetwork took global features as input and generated another shallow head. This shallow head predicted high-frequency residual. It fused two predictions of shallow heads into final signed distance function. Spectrum analysis shows that the design purpose of network is achieved. Compared with other smooth surface reconstruction schemes, the network can achieve smoother surface reconstruction with enough details. It overcomes the overfitting of SDF-SRN. The qualitative and quantitative comparison with other advanced single-view reconstruction approaches show the superiority of the proposed approach. [ABSTRACT FROM AUTHOR]

Gear fault detection based on vibration analysis has been proven to be effective in fault identification. However， the extraction and identification of vibration signals characterizing early wear have not been solved well. This paper proposes a method for early wear diagnosis of gears， combining variational mode decomposition (VMD) based on spectrum correlation analysis with kernel support vector machine (SVM). For weak gear vibration signals that can characterize early wear， the modal numbers are initialized by an approximate complete reconstruction criterion. Meanwhile， the frequency corresponding to the maximum value of the signal power spectral density is used to initialize the center frequency of the VMD method. It is used to effectively extract gear wear information from gear vibration signals and then be combined with kernel support vector machines for early wear diagnosis of gears. The experimental results show that the proposed method can effectively overcome the problem that the modal numbers cannot be preset with large background noise， be with better robustness to noisy situations， and achieve a diagnostic accuracy of 94.4%， which provides a solution for early wear detection of gears. [ABSTRACT FROM AUTHOR]

Aiming at the urgent demands of intelligent fault diagnosis for the key components of helicopter main reducers， the dynamic response characteristics of the system under the typical fault state are analyzed from the perspective of dynamic modeling， which is conducive to deepening the understanding of fault mechanism and advanced diagnosis algorithm. The fault dynamic models considering multi-nonlinear factors are developed for the typical components of a helicopter main reducer using the lumped-parameter method， and the multi-body software is applied for simulation modeling and verification. The results show that the modulation phenomenon between meshing frequency and local fault characteristic frequency is clear and the circumferential responses of the planet gear are obviously greater than the translational responses. these models can effectively reveal the vibration characteristics under typical faults and provide guidance for fault diagnosis of the helicopter transmission system. [ABSTRACT FROM AUTHOR]

Based on water stage prediction-correction method, an 1D-3D coupled method is proposed to accurately simulate the surge wave caused by the transient process of hydropower stations in open channel, overcoming the inability of low-dimensional models to fully resolve the horizontal and vertical fluctuation of the surge wave, and low computational efficiency of high-dimensional models. Typical verification cases, including the tidal wave motion, the partial dam break flow and the open channel transient flow are simulated to analyze the accuracy of the proposed method. The simulated results are in good agreement with asymptotic theoretical solution and those yielded by commercial software. To futher demonstrate its capability in practical cases, the surge wave triggered by the transient process of the Gezhouba hydropower station is simulated. The maximum and minimum surge wave heights including its attenuation characteristics are analyzed. The results are in good agreement with those yielded by spectrum analysis, showing that the proposed method is capable of simulating practical transient flows in open channel. [ABSTRACT FROM AUTHOR]

This paperanalyzed the relationship between the frequency phase difference of the ultrasonic transducer and the offset value.Considering the fact thatthe classic controller constructed bythe time domain model has not high applicability, this research proposed a frequency tracking system of ultrasonic power supply based on the fuzzy PI control.Also, a time-domain model for molding the current and voltage at both ends of the transducer was presented.The phase difference between the two can be obtained by spectrum analysis methodandthe simulation analysis of ultrasonic power frequency trackingcan bemade.The ultrasonic power frequency tracking system was constructed and analyzed.The initial resonance frequency wasmeasured under normal working voltage.Simulation analysis and experimental data showed the effectiveness of the method.This study found that compared with the traditional control method, the fuzzy PI method can improve the control accuracy of the system, and consequently it can improve the service life and operating efficiency of the ultrasonic transducer. [ABSTRACT FROM AUTHOR]

Aiming at the problem of phosphorus emission pollution caused by the widespread use of phosphorus-based corrosion and scale inhibitors in industrial production circulating cooling systems, maleic anhydride is used as the main raw material, calcium hydroxide is used as the initiator, and a “one-step” synthesis process is used to synthesize a phosphorus-free corrosion and scale inhibitor, through infrared spectrum analysis and nuclear magnetic resonance spectrum analysis, which shows that the synthesized phosphorus-free corrosion and scale inhibitor is polyepoxysuccinic acid(PESA). Through infrared spectrum analysis and nuclear magnetic resonance spectrum analysis, it is shown that the synthesized product is PESA. The corrosion and scale inhibition performance of PESA under different conditions was studied by rotating coupon method and calcium carbonate deposition method. The results show that the dosage of PESA is 110 mg/L, the circulating water temperature is lower than 45 ℃, and the pH is neutral or alkaline. Under normal conditions, when the water flow speed is less than 85 r/min, the corrosion rate of PESA to A3 carbon steel is less than 0.248 mm/a, the maximum corrosion inhibition rate can reach 60.9%, and the maximum scale inhibition rate is nearly 100%. At the same time, the corrosion and scale inhibition mechanism of PESA was analyzed by means of conductivity meter, infrared spectroscopy, scanning electron microscope, etc. The results show that PESA achieves scale inhibition performance through dispersion, chelation and lattice distortion. A protective film is formed on the surface to prevent the transfer of corroded electrons, thereby preventing metal corrosion. [ABSTRACT FROM AUTHOR]

The surface modification of cordierite was carried out with mullite whiskers grown by the molten salt method. Using cordierite/mullite whiskers composite material as the matrix, LaCoO3 monolithic cDPF (C/M/LC) and LaCo0.9Mn0.1O3 monolithic cDPF (C/M/LCM) was prepared by the sol-gel impregnation method. The monolithic catalysts were characterized by means of microscopy (SEM),energy spectrum analysis (EDS),X-ray diffraction (XRD),H2 temperature programmed reduction (H2-TPR) and other means. The results showed that the catalyst was uniformly distributed on the support, and the introduction of Mn can significantly improve the catalytic activity of the catalyst without changing the structure of the perovskite itself. The ultrasonic vibration treatment showed that the catalyst layer and the carrier were firmly bonded, and after 60 min of ultrasonic treatment, the weight loss was 4.6%.The performance test results show that among the prepared catalysts, LaCo0.9Mn0.1O3 monolithic cDPF has higher catalytic activity for soot, and its T10,T50 and T90 are 329,417,516 ℃ respectively. [ABSTRACT FROM AUTHOR]

BACKGROUND: Through visiting the jadeite market, the existence of inorganic material-filled jadeite is known, but there is a lack of identification basis due to rare references. OBJECTIVES: To understand the identification characteristics of inorganic material-filled jadeite. METHODS: Two types of inorganic materials, water glass and silica sol, were used to fill low-grade jadeite in the simulation experiment. Conventional gemological tests, fluorescence image observation with DiamondViewTM, Fourier transform infrared (FTIR) spectroscopy, and laser-induced breakdown spectroscopy (LIBS) were used to test the inorganic filled jadeite samples. RESULTS: The transparency, color, density and structure of jadeite were improved after filling. Under the DiamondViewTM, the jadeite particles in the sample showed green fluorescence, and the filling around the cracks and between the particles displayed blue fluorescence with non-uniform distribution. Mid-infrared reflectance spectrum analysis showed that the spectra of silica sol and water-glass were slightly different from each other. The absorption peaks of the samples filled with inorganic materials at 1162 cm-1, 1070 cm-1, 949 cm-1, 579 cm-1, 529 cm-1 and 470 cm-1 gradually weakened, and the peak shape gradually became smooth or disappeared. In addition, the differences between the jadeite and inorganic filled jadeite can be determined by the near-infrared spectral morphology and the shape of the absorption peak changed in the range of 7062 cm-1, 5204 cm-1 and 4537 cm-1. The laser-induced breakdown spectroscopy demonstrated that the content of the silicon in the jadeite filled with silicon sol or sodium and potassium water-glass was higher. The high potassium content was an important feature for the jadeite filled by sodium and potassium water-glass. CONCLUSIONS: The samples effect of the simulation experiment needs to be improved, but the identification characteristics of the filled jadeite with inorganic materials are recognized, which has caused a further breakthrough in the enhancement and treatment of jadeite identification. [ABSTRACT FROM AUTHOR]

Many existing arrhythmia researches focus on the separation of different frequency characteristic components in the ECG signal. However, the contribution of different subsequences to the final target decision-making is lack of research and analysis. In order to enhance the impact of high-contribution subsequences on the classifier, a recognition method combining variable weight singular spectrum analysis and deep learning is proposed. Multiple subsequences are obtained through singular spectrum analysis. The Gini coefficient under the random forest is calculated by the singular value of each sequence and used as the weight. The sequence samples with variable weights are used to train the neural network model, which can mine useful information more efficiently and further improve the recognition accuracy. The accuracy rate of final arrhythmia recognition is 98. 35%, and Macro-Fl is 97. 95%. Compared with the traditional fixed weight, the proposed recognition method of variable weight has a significant improvement in various performance indicators. [ABSTRACT FROM AUTHOR]

In order to study the influence of different delay times on underground shallow hole blasting, numerical simulation software LS-DYNA was used to study the operation mode of underground shallow hole blasting with precise delay and hole-by-hole initiation. Based on the research status at home and abroad, five kinds of continuous uncoupled charged with different delay times of 15,20,25,30 and 35 ms were used for shallow-hole blasting. The field fine delay by hole initiation test was carried out. The blasting vibration velocity was collected by blasting vibration tester, and the velocity waveform was explored and analyzed. It was found that the vibration velocity peak at 25 ms with delay time decreased by 27%,8%,29% and 52% respectively, compared with the peak velocity at 15,20,30 and 35 ms. The research shows that the delay time is 25 ms, and the vibration reduction is the most pronounced. Reasonable delay time can effectively reduce the blasting vibration intensity and ensure the safety of surrounding rock masses. [ABSTRACT FROM AUTHOR]

Objectives: There are obvious seasonal variations in the GPS height time series, which affect the improvement of precision and can be corrected by both mathematical modelling and geophysical mechanisms. Compared to least square fitting, singular spectrum analysis (SSA) can extract random seasonal signals effectively through signal reconstruction, which is unaffected by the assumed sinusoidal waves. According to the elastic loading theory, the gravity recovery and climate experiment (GRACE) can be used to calculate the vertical surface displacement caused by changes in terrestrial water storage. Methods: This paper mainly studies the feasibility of correcting the seasonal variations in GPS heights using SSA and GRACE inversion results. The height time series of 27 GPS stations in Australia with a time span of from 5 to 10 years were chosen and combined with GRACE simultaneous inversions. Results: Because the spatial resolutions of GRACE are coarse and the loading displacement is much more sensitive to near‑field mass changes than far‑field ones, the amplitudes of GRACE ‑inferred hydrological loading deformations are significantly smaller than GPS. The weighted root mean square (WRMS) are reduced at 22 stations after GRACE ‑inferred displacement corrections, and the correlation coefficients between deformations estimated by GPS and GRACE range from 0.12 to 0.78 with a mean value of 0.43, indicating that GPS and GRACE results have good consistency and correlation. SSA is used to extract the annual signals of vertical displacements derived from GPS and GRACE, and contribution rates of singular spectral variance of annual signals are 21.60% and 34.48%, respectively, expressing that annual signals are the main components of GRACE inferred results. Geographical climatic conditions have a significant impact on the consistency of annual signals derived from GPS and GRACE. Compared with the arid areas in central and western Australia, the amplitude and phase of annual signals derived from GPS and GRACE are more consistent in the northern region with seasonal rainfall. Furthermore, cross wavelet transform (XWT) finds that the vertical displacement series derived from GPS and GRACE of each station have a significant resonance period of one year. The circular average phase angles of GPS/GRACE at the period closet to 1 cycle per year (cpy) outside the cone of influence range from − 74.03° to 67.23° . The mean XWT ‑ based semblances range from 0.28 to 0.99 with an average value of 0.79, showing that there is a significant positive correlation between the annual variations derived from GPS and GRACE. Conclusions: Overall, GRACE‑inferred deformations can explain the annual variations of GPS‑derived displacements, particularly in areas with high hydrological loading. It is possible to correct the annual signals of GPS heights by GRACE inversions, but the effect is not as good as the SSA‑filtered annual signals. [ABSTRACT FROM AUTHOR]

Unmanned Aerial Vehicle (UAV) remote sensing can be widely used to capture large-scale high overlapping and high spatial resolution images from the ground in a low-cost way. However, the UAV Red-Green-Blue (RGB) images are usually obtained, because the UAV sensors can only contain the wavebands with the visible light range, such as the red, green, and blue. It is difficult to extract the feature information from the UAV RGB images because of the fewer wavebands. Taking the UAV RGB orthophoto image as the research object, an image extraction was proposed to integrate the point cloud matching with the Hue-Saturation-Intensity (HSI) color component. Firstly, the high overlapping ground images were acquired by UAV, thereby constructing the point cloud matching using dense matching, where a digital surface model was generated. Then, the ground points and non-ground points in the study area were obtained by a cloth simulation filtering. Specifically, the ground points were interpolated to generate the digital elevation model. As such, a normalized digital surface model was obtained via the difference between the digital surface model and digital elevation model. Secondly, a saturation-red ratio index was established to extract the bare land using the color components of HSI color space and visible light bands. A bare land extraction was then carried out to verify the model. Thirdly, the expansion index was constructed by multiplying the formula of saturation-red ratio index by the standard deviation of the red band to extract the water with the sediment. Finally, two models and three indexes were achieved to classify the UAV RGB orthophoto images in the study area, including the digital elevation model, the normalized digital surface model, the visible-band difference vegetation index, the saturation-red ratio index, and the expansion index. Afterwards, an experiment was then carried out to verify the extraction model. The results showed that the saturation-red ratio index presented a higher accuracy in the bare land extraction from the UAV RGB images. The normalized digital surface model performed better to obtain the key feature that distinguished from the trees and grasslands using the matching of point cloud interpolation. Furthermore, the river and bare land were successfully extracted, using the saturation-red ratio and the expansion index under the HSI color components, while the digital elevation model features that obtained from the point cloud matching. The overall accuracy of the rule-based classification was 91.11%, where the Kappa coefficient was 0.895. In the classification, the highest producer’s accuracy and user’s accuracy were the buildings and rivers, which reached 96.25% and 99.15%, respectively. Moreover, there was an outstanding elevation difference in the high-precision digital elevation model, digital surface model, and normalized digital surface model. Additionally, the saturation-red ratio and expansion indexes were composed of the visible light band and the color component of saturation, particularly for the extraction of bare land and sand water. Consequently, it can be feasible to combine the point cloud matching and the color components of the HSI color space in the extraction of UAV RGB orthophoto image information. [ABSTRACT FROM AUTHOR]

CdZnTe detectors play an important role in international astronomy research. In this paper, the spectra response of CdZnTe planar detector for γ-ray was numerically simulated using GEANT4 Monte-Carlo simulation toolkit, and the influence of the factors, such as transport properties of electrons and holes, applied bias voltage, thickness of detector and other factors were studied. The calculated results show that when the charge collection efficiency ( CCE) of electron is high, the dependence of energy resolution on the ratio of electron and hole mobility-lifetime product ((μτ)e/ (μτ)h) is strong, and the resolution increases with the decrease of the ratio. The energy resolution and CCE of carrier can be improved by raising up the bias. When the CCE of electron is high, increasing thickness can weaken the hole signal contribution to the total induced charge, and improve the energy resolution. The value of (μτ)eE /d can be used to evaluate CCE of planar CdZnTe detectors for rays of low energy, and the corresponding relationship was calculated. [ABSTRACT FROM AUTHOR]

BACKGROUND: Niobium is a strategic metal with wide applications and plays a very important role in modern steel technology. The average content of Nb2O5 in a niobium-rare earth ore is 0.0855%, and the content of total rare earth (REO) is 1.03%, which is close to the minimum industrial grade requirement of niobium ore. Niobium minerals and rare earth minerals have the characteristics of small particles and complex intergrowths, which makes them difficult to find under a polarized microscope. OBJECTIVES: To investigate the forms of niobium and rare earth elements. METHODS: Electron probe backscatter image, energy spectrum analysis and electron probe spectrum quantitative analysis were used to analyze niobium and rare-earth ore. RESULTS: Niobium mainly existed in the form of niobite and niobium-bearing rutile. The average content of Nb2O5 in niobite was 78.26% and that in niobium-bearing rutile was 5.26%. Rare earth elements mainly existed in the form of monazite, bastnaite and bastnaesite. The average content of rare earth elements (REO) in monazite, bastnaite and bastnaesite was 64.84%, 57.52% and 70.61%, respectively. Niobium and rare-earth minerals were distributed and dispersed. They were mostly trapped in the gangue minerals such as potassium feldspar, calcite and biotite. CONCLUSIONS: The types and characteristics of the main niobium and rare earth minerals in the ore deposit were identified. This study has important guiding significance for the comprehensive utilization of niobium and rare earth deposits in the future. [ABSTRACT FROM AUTHOR]

As an important economic tree species in China, tea trees play a critical role in promoting economic development. However, the expanding area of tea plantations in China over the recent years has reduced the biodiversity of the ecosystem and accelerated ecological problems. Identifying the spatial distribution of the tea plantation accurately is important for the monitoring of the tea plantation as well as the development of the tea industry. In this study, Wangzhai Town, located in the central of Wuyi County in Zhejiang Province, was chosen as the study area, and Gaofen-1 (GF-1) data on December 28, 2017, and all available Sentinel-2 data in 2017 were downloaded to study the tea plantations extraction method. The spectral and texture features of tea plantations are similar with crops on the high spatial resolution remote sensing image which results in the mixture of the tea plantations and crops. The Normalized Difference Vegetation Index (NDVI) time series data can reflect the phenological changes of the tea trees and crops, which can be used to improve the separability of tea plantations and crops. In this study, a phenology-based approach was applied to the NDVI time series to distinguish tea plantations from crops by comparing the similarity of the seasonal changes of NDVI time series. Due to the influence of cloud and fog on the satellite image, the complete Sentinel-2 time series data is difficult to be obtained. Therefore, the high temporal resolution Moderate-resolution Imaging Spectroradiometer (MODIS) reflection product (MCD43A4) in 2017 was used to reconstruct the complete Sentinel-2 NDVI time series data (5 m spatial resolution, 5 d temporal resolution) based on Bayesian Maximum Entropy (BME) spatial-temporal fusion algorithm. Then, the Dynamic Time Wraping (DTW) distance was calculated based on the DTW algorithm to characterize the similarity of NDVI time series between the tea plantation samples and other pixels to be classified. Combining the advantages of GF-1 in spatial details and the high temporal resolution of reconstructed Sentinel-2 NDVI time series in capturing the difference of growth process of tea trees, the tea plantation was identified based on random forest algorithm. Two identification schemes: 1) spectral and texture features based on GF-1; 2) spectral, texture features based on GF-1 and DTW distance were set up to investigate the impact of NDVI time series on the tea plantation identification. The results showed that: 1) the reconstructed NDVI time series data derived from MODIS and Sentinel-2 based on spatio-temporal fusion algorithm is able to capture the seasonal dynamics of different objects, and the DTW distance can capture the difference of NDVI time series data between crops and tea plantations and can be used for tea plantations extraction; 2) the accuracy、 error rate、precision、recall and F1score were 96.91%、3.09%、89.00%、83.09% and 0.86 respectively combining texture and spectral information of GF-1 and Sentinel-2 NDVI time series information, which were 94.72%、5.28%、73.09%、84.61% and 0.78 respectively without Sentinel-2 NDVI time series information. Overall, the results of combining GF-1 and Sentinel-2 time series data performed better than that only based on the spectral and texture features of GF-1. These results confirmed that combining high spatial resolution with high temporal resolution time series remote sensing data is an effective method to improve the identification accuracy of tea plantations. [ABSTRACT FROM AUTHOR]

The Jianzha Basin is located in the northeastern margin of Tibetan Plateau, and contains a thick sequence of Cenozoic sediments, which is composed of the sequence of eolian red clay with a bit part fluviolacustrine deposits. The Jiarang section in Jianzha Basin is an ideal section for cyclostratigraphy, because of its high resolution on magnetostratigraphy and environmental magnetism. Based on the systematic cyclostratigraphy of 3 - 361 m sedimentary strata of Late Miocene in Jiarang section, the absolute astronomical time scale of Jiarang section was established, and the dominant period of earth orbital parameters affecting the paleoclimate evolution in Jianzha Basin was extracted, in order to provide basic data for the further comparison between land and sea, and the paleoclimatic and environmental evolution. The result of spectrum analyses of frequency-dependent magnetic susceptibility (Xfd) in depth domain shows that there is a stable 26 m sedimentary cycle representing long eccentricity period in the 3 - 361 m interval, and the sedimentary cycles representing other astronomical orbital periods are also present, but not stable. Based on the identified sedimentary cycles, the long eccentricity period was used to tune frequency-dependent magnetic susceptibility data series in depth domain of 3 - 361 m. Combined with the magnetostratigraphic chronological framework of Jiarang section, the absolute astronomical time scale of 11. 758 - 5. 890 Ma was established. The astronomical tuning for frequency-dependent magnetic susceptibility data series in time domain is consistent with the paleomagnetic age, which indicates that the astronomical time scale is reliable. The spectrum analyses for frequency-dependent magnetic susceptibility and marine oxygen isotope records show that there are obvious periodic shifts in about 7. 2 Ma. This record reveals that the East Asian summer monsoon (EASM) is dominated by 41 ka obliquity period before 7. 2 Ma, and controlled by 100 ka short eccentricity period after 7. 2 Ma. [ABSTRACT FROM AUTHOR]

Uncaria rhynchophylla contains large amount of alkaloids and abounds in natural resources, and has the function of heat-clearing for calming liver and wind-calming for calming frightened. In order to make clear the material basis of stems and leaves of U. rhynchophlla, in this paper, the chemical constituents of stems and leaves from U. rhynchophylla and their antitumor activities were studied. The extracts were isolated and purified by using silical gel, Sephadex LH-20, semi-HPLC, and the structures of the compounds were identified by physicochemical property and spectrum analysis. The antitumor activities of chemical constituents against K562, HEL cell lines were assessed by MTT method. Seven compounds were isolated and identified from stems of U. rhynchophylla as 3, 4, 5-trimethoxyphenol(1),scutellarin(2), isohydrohydrogenine(3), dehydroramine(4), Vallesiachotamine(5), isorhynchophylline(6), rhynchophylline(7). Twelve compounds were isolated and identified from leaves of U. rhynchophylla as octadecanol(8), β-sitosterol(9), tridecanoicacid(10), 2-methyl-5,7-dihydroxy-chroone-7-O-β-D-glucopyranoside(11), oleanolic acid(12), quercetin(13), ivy aglycone(14), kaempferol(15),(6R, 9R )-9-hydroxymegastigman-4-en-3-one(16), ursolic(17), epicatechin(18), emodin methylether(19). The results of antitumor activities were as follows:(1)Compounds 3 and 5 inhibited the activities of HEL cell lines, and IC50 values were 17.96 and 73.01 μg·mL-1; Compound 5 inhibited the activities of K562 cell lines, and IC50 values were 16.45 μg·mL-1, which indicate that some compounds from stems of U. rhynchophylla have certain antitumor activities.(2)Compounds 1, 8,10 and 16 were isolated from this plant for the first time. This study shed the scientific light on reasonable utilization and sustainable development of plant resources. [ABSTRACT FROM AUTHOR]

Aiming at the serious problem of tubing corrosion in huff and puff well, the corrosion. products of carbon dioxide stimulation wells were analyzed. The corrosion type of huff and puff oil well are determined as carbon dioxide corrosion. by using methods of microscopic morphology analysis. energy spectrum analysis. metallographic analysis and X-ray diffraction analysis. Basing on the study of corrosion law. a comprehensive corrosion prevention and control technology thought was put forward, which includes liquid corrosion inhibitor. solid corrosion inhibitor and other chemical corrosion protection technology as primary. deepening liner protection technology. sacrificial anode protection technology and tubing coating protection technology as auxiliary. The reasonable dosage concentration and dosage method of corrosion inhibitors were determined through experiments. Field tests were carried out in 69 wells, and the oil well lifetime has been extended from 260 days to 400 days, which verifies the effectiveness of the comprehensive corrosion prevention and control technology. [ABSTRACT FROM AUTHOR]