Soil moisture is an important variable in ecological, hydrological, and meteorological studies. An effective method for improving the accuracy of soil retrieval mutual supplementation multi-source data. The sensor configuration band settings different optical sensors lead to differences reflectivity inter-data, further resulting between vegetation indices. combination synthetic aperture radar (SAR) data with has been widely used retrieval. However, influence indices derived from sources on...

Highly selective assembly of 2,3-fused indolizines was achieved via a cascade allylation/Friedel–Crafts type reaction with Cu/Ir catalysis. This protocol furnishes stereodivergent synthesis chiral bearing three stereogenic centers excellent results.

Global navigation satellite system reflectometry (GNSS-R) is a new remote sensing technique, which can be used to measure wide range of geophysical parameters. GNSS-R makes use the simultaneous reception direct transmission and coherent surface reflections GNSS signal with either single antenna or multiple separate antennas. This paper presents snow depth estimation method using combination pseudorange carrier phase dual-frequency signals. The proposed geometry-free not affected by...

<title>Abstract</title> As the probability and intensity of global drought events continue to increase, soil moisture is an important basis for monitoring assessment, need accurately obtain distribution information with high spatial-temporal resolution becoming extremely important. CYGNSS data based on spaceborne GNSS-R has advantage temporal resolution, while SAR can provide surface features spatial combination two provides favourable conditions obtaining resolution. This paper proposes a...

ABSTRACT We observed the blazar 2200 + 420 in I, R, and V bands using 1.0 m telescope at Weihai Observatory of Shandong University on eight nights October 2022 obtained over 3800 data points. Using F-test ANOVA test, we analysed light curves found intra-day (IDV) variability every night. that all amplitudes (Amp) are 10 per cent, except for 22, with four having above 20 cent maximum amplitude reaching 42 cent. Additionally, discovered a minimal time-scale 24.6 min bluer-when-brighter (BWB)...

We carried out a high time-resolution, multicolour optical observing campaign for eight $\gamma$-ray detected blazars during 2010-2020. analyze flux variations, correlations between magnitudes and colours on different timescales. Intraday variability (IDV) is in all sources of our sample. A bluer-when-brighter (BWB) chromatic trend dominant intraday On the short timescales, BWB only shows up ON 231, 3C 279, BL Lacertae 1E 1458.8+2249. There 279 long timescale. estimate upper limits black...

Snow depth and snow water equivalent (SWE) are two parameters for measuring snowfall. By exploiting the Global Navigation Satellite System reflectometry (GNSS-R) technique thousands of existing GNSS Continuous Operating Reference Stations (CORS) deployed in cryosphere, it is possible to improve temporal spatial resolutions SWE measurement. In this paper, a fusion model combining multi-satellite SNR (Signal Noise Ratio) estimations proposed, which uses peak spectral powers associated with...

The European Union Water Framework Directive (2000/60/EC; WFD) aims to achieve a good ecological and chemical status of all bodies surface water by 2027. development integrated guidance on monitoring (e.g., WFD Guidance Document No. 7/19) has been transferred into national German law (Ordinance for the Protection Surface Waters, OGewV). For majority compounds, this act requires monthly sampling assess quality body water. To evaluate representativeness strategy under OGewV, high-frequency...

Global navigation satellite system (GNSS) multipath signals received by a geodetic-quality GNSS receiver can be used to estimate the water content of soil around antenna. The direct from antenna are most valuable in geodetic measurement, such as positioning, navigation, control network, deformation monitoring, and so on. However, also captures reflected ground, which contain information surrounding environment, that useful about reflection surface inferred analyzing signal. This technique is...

In the last 20 years, reflected signal of Global Navigation Satellite System (GNSS) has been used for remotely sensing a series geophysical parameters, resulting in two GNSS based techniques: reflectometry (GNSS-R) and interferometric (GNSS-IR). this letter, refracted is first proposed to estimate near-surface soil moisture (SM). Amplitude will attenuate when penetrated into due refraction propagation soil. attenuation degree quantified as amplitude ratio (AR) direct signal. Two low-cost...

We systematically search for quasiperiodic oscillatory (QPO) signals on the month timescale among 1525 sources given in Fermi Large Area Telescope Light Curve Repository. find a transient QPO of 31.3$\pm$1.8 days gamma-ray band light curve TeV blazar S5 0716+714, which has seven cycles (MJD 55918-56137) first time by weighted wavelet Z-transform and Lomb-Scargle periodogram methods. Monte Carlo simulations based power spectral density probability distribution function were used to evaluate...

Electroencephalogram signals are time-varying complex electrophysiological signals. Existing studies show that approximate entropy, which is a nonlinear dynamics index, not an ideal method for electroencephalogram analysis. Clinical measurements usually contain electrical interference signals, creating additional challenges in terms of maintaining robustness the analytic methods. There urgent need novel dynamical analysis can characterize seizure-related changes cerebral dynamics. The aim...

Purpose Nowadays, WiFi indoor positioning based on received signal strength (RSS) becomes a research hotspot due to its low cost and ease of deployment characteristics. To further improve the performance RSS, this paper aims propose novel position estimation strategy which is called radius-based domain clustering (RDC). This technology avoid issue access point (AP) selection. Design/methodology/approach The proposed approach uses each individual AP all available APs estimate target point....

Two estimation methods using a dual GNSS (Global Navigation Satellite System) receiver system are proposed. The dual-frequency combination method combines the carrier phase observations of signals, whereas single-frequency pseudorange and signal, both which geometry-free strictly free effect ionospheric delay. Theoretical models established in offline to describe relationship between spectral peak frequency combined sequence antenna height. A field experiment was conducted recently data...

The European Union Water Framework Directive (2000/60/EC; WFD) aims to achieve a good ecological and chemical status of all bodies surface water by 2027. development an integrated guidance on monitoring (e.g. WFD Guidance Document No. 7/19) has been transferred into national German law (Ordinance for the Protection Surface Waters, OGewV). For majority compounds, this act requires monthly sampling frequency assess quality body. To evaluate representativeness strategy under OGewV,...

Comparisons between different global navigation satellite system (GNSS) signals and GNSS-reflectometry (GNSS-R) systems can provide valuable suggestions for future development of the GNSS-R instrument signal processing method. This article evaluates ocean altimetry performance multiple GNSS constellation using raw intermediate frequency data collected by Cyclone (CYGNSS) TechDemoSat-1 (TDS-1) satellites. Data used evaluation include observations GPS L1, Galileo E1, BDS B1 band signal. The...

Spaceborne GNSS-R technology is a new remote sensing method for soil moisture monitoring. Focusing on the significant influence of water surface reflectivity CYGNSS, this paper improved removal according to spatial resolution CYGNSS data. Due disturbance effect incident angle, microwave frequency and type Fresnel reflection coefficient in reflectivity, normalization was proposed after analyzing data characteristics variables coefficient. Finally, combined with retrieval linear equation,...

Abstract We select 48 multiflare gamma-ray bursts (GRBs) (including 137 flares) from the Swift/XRT database and estimate spectral lag with discrete correlation function. It is found that 89.8% of flares have positive lags only 9.5% show negative when fluctuations are taken into account. The median multiflares (2.75 s) much greater than GRB pulses (0.18 s), which can be explained by fact we confirm GRBs multipulse similar lag–duration correlations. investigate origin checking E peak evolution...

Global Navigation Satellite System interferometric reflectometry is an emerging remote sensing technique that can be used to measure a wide range of geophysical parameters. In this letter, low-cost navigational GNSS chip and RHCP antenna were receive process the interference signal in winter wheat farmland. By simplifying crop as multi-layer equivalent mediums (EMs), characteristics SNR observations recorded by instrument analyzed. The confidence level Lomb-Scargle spectral analysis result...

Abstract As an indispensable surface parameter, soil moisture is of great significance for analyzing global water cycle, establishing the hydrological model and assessing drought. Due to differences in capability vegetation content (VWC) models based on different indices, influence VWC retrieval accuracy has not been effectively assessed. Therefore, suitability parameters obtained from established by indices accurate requires further investigation. In this study, were derived Sentinel‐2 data...

The surrounding environment of a GNSS observation station is changed during flood, and this results in more serious multipath than normal environment. Considering that the error largely related to pseudo-range CNR (Carrier-to-noise ratio) signal, influence floods on analyzed theory through experiment. To ensure accuracy analysis results, ground track repeat period GPS, GLONASS, BDS satellites investigated from perspective skyplots. Two real cases study collected Zhengzhou Xinxiang, China,...

The CNR (Carrier-to-Noise Ratio) of GPS (Global Positioning System) satellites is highly relevant to the multipath error. error more serious in flood environment since reflection and diffraction coefficients water are much higher compared dry soil. Thus, amplitude will decrease environment. In this study, relationship between error, flooding, introduced theory. Then, by using characteristic orbital repetition period, stability 2 adjacent days a static observation demonstrated 32 MGEX...