Payload Symbol-Based Nonlinear RF Fingerprint for Wireless QPSK-OFDM Devices

Radio Frequency(RF) fingerprinting is one physical-layer authentication method for wireless communication, which uses the unique hardware characteristic of the transmitter to identify its true identity.To improve the performance of RF Fingerprint(RFF)based on preamble with fixed duration, a nonlinear RF fingerprinting method based on payload symbols is proposed for the wireless OFDM communication with the bit mapping scheme of QPSK. The wireless communication system is modeled as a Hammerstein system containing the nonlinear transmitter and multipath fading channel. A parameter separation technique based on orthogonal polynomial is presented for the estimation of the parameters of the Hammerstein system. The Hammerstein system parameter separation technique is firstly used to estimate the linear parameter with the training signal, which is used to compensate the adverse effect of the linear channel for the demodulation of the successive payload symbols. The demodulated payload symbols are further used to estimate the nonlinear coefficients of the transmitter with the Hammerstein system parameter separation technique again, which is used as the novel RFF for the authentication of the QPSK-OFDM device. Numerical simulations have verified the proposed method, which can also be extended to the OFDM signals with other bit mapping schemes.

Quantifying the carbon source of pedogenic calcite veins in weathered limestone: implications for the terrestrial carbon cycle

The continent is the second largest carbon sink on Earth’s surface.With the diversification of vascular land plants in the late Paleozoic,terrestrial organic carbon burial is represented by massive coal formation,while the development of soil profiles would account for both organic and inorganic carbon burial.As compared with soil organic carbon,inorganic carbon burial,collectively known as the soil carbonate,would have a greater impact on the long-term carbon cycle.Soil carbonate would have multiple carbon sources,including dissolution of host calcareous rocks,dissolved inorganic carbon from freshwater,and oxidation of organic matter,but the host calcareous rock dissolution would not cause atmospheric CO2drawdown.Thus,to evaluate the potential effect of soil carbonate formation on the atmospheric p CO2level,different carbon sources of soil carbonate should be quantitatively differentiated.In this study,we analyzed the carbon and magnesium isotopes of pedogenic calcite veins developed in a heavily weathered outcrop,consisting of limestone of the early Paleogene Guanzhuang Group in North China.Based on the C and Mg isotope data,we developed a numerical model to quantify the carbon source of calcite veins.The modeling results indicate that4–37 wt%of carbon in these calcite veins was derived from atmospheric CO2.The low contribution from atmospheric CO2might be attributed to the host limestone that might have diluted the atmospheric CO2sink.Nevertheless,taking this value into consideration,it is estimated that soil carbonate formation would lower 1 ppm atmospheric CO2within 2000 years,i.e.,soil carbonate alone would sequester all atmospheric CO2within 1 million years.Finally,our study suggests the C–Mg isotope system might be a better tool in quantifying the carbon source of soil carbonate.

Determination of Hf–Sr–Nd isotopic ratios by MC-ICP-MS using rapid acid digestion after flux-free fusion in geological materials

In this study, we established a rapid acid digestion for determining Hf-Sr-Nd isotopic ratios of geological samples by using MC-ICP-MS. Conditions of 1600 ℃ for 1 min and 1400 ℃ for 1 min were adopted for fusing intrusive rocks and extrusive rocks, respectively. The rapid acid digestion technique is superior in digestion time compared with high-pressure PTFE bomb method. The procedural blanks of the method were also lower than that flux fusion. Replicate analyses of international certified reference materials （CRMs） indicate that isotopic ratios of ^176Hf/^177Hf, ^87Sr/^86Sr and 143Nd/144Nd agree well with previously published data. The external reproducibility （2SD, n = 5） of ten CRMs are ±0.000030 for ^87Sr/^86Sr, ± 0.000030 for ^143Nd/^144Nd, and ±0.000018 for ^176Hf/^177Hf.

Standard-sample bracketing calibration method combined with Mg as an internal standard for silicon isotopic compositions using multi-collector inductively coupled plasma mass spectrometry

Silicon isotope analysis traditionally uses a standard-sample bracketing （SSB） method that relies upon greater instrument stability than can be consistently expected. The following proposed method reduces the level of instrumental stability required for the analysis process and provides a valid solution for high-precision and accurate studies of Si isotopic compositions. Rock samples were dissolved by using alkali fusion and acidification. Silicon isotopes were purified with an ion exchange resin. Interfering peaks for isotopes were separated by using a Nu Plasma 1700 multi-collector inductively coupled plasma mass spectrometry （MS） system in high-resolution mode （M/AM 〉 8000 RP）. Two magnesium isotopes （25Mg and 26Mg） and three silicon isotopes （28Si, 29Si, and 3;Si） were analyzed in the same data collection cycle. Mg isotopes were used as an internal standard to calibrate the mass discrimination effects in MS analysis of Si isotopes in combination with the SSB method in order to reduce the effects of MS interference and instrumental mass dis- crimination on the accuracy of measurements. The conventional SSB method without the Mg internal standard and the proposed SSB method with Mg calibration delivered consistent results within two standard deviations. When Mg was used as an internal standard for calibration, the analysis precision was better than 0.05 %0 amu.

Simultaneous Measurement of Major, Trace Elements and Pb Isotopes in Silicate Glasses by Laser Ablation Quadrupole and Multi-Collector Inductively Coupled Plasma Mass Spectrometry

A method was developed for the rapid in situ analysis of major and trace elements and Pb isotopes in silicate glass samples that combines laser ablation quadrupole and multi-collector inductively coupled plasma mass spectrometry（LA-Q-ICP-MS/MC-ICP-MS）. Major, trace elements, and Pb isotope ratio compositions were clearly affected by laser conditions. Using a laser spot size of 160 μm, a laser ablation frequency of 15 Hz, an energy density 18 J/cm^2, and a 1 ： 9 ratio of laser ablation aerosol to the corresponding makeup gas, we obtained accurate major and trace element contents and Pb isotope ratios. Using Ca as the internal standard element, and GSE-1G and NIST 610 as the external standards for calibration, element contents generally matched the preferred values within 15%. Higher relative errors for some elements（e.g., Cr, Ga, Ge） may have been caused by lower than recommended values in some standards. The exponential law correction method for Tl normalization, with optimum adjusted Tl ratio, was utilized to obtain Pb isotopic data with good precision and accuracy. Pb isotopic ratios of the glass reference materials were in good agreement with the reference or published values to within 2 s measurement uncertainties, and the analytical precision was better than 0.17%（e.g., ^（208）Pb/^（206）Pb）. The developed method is a simple, reliable, and accurate technique for determining major, trace elements, and Pb isotope compositions of silicate glasses and minerals within a single ablation event.

A Fast Separation Method for Isotope Analysis Based on Compressed Nitrogen Gas and Ion-Exchange Chromatography Technique--A Case Study of Sr-Nd Isotope Measurement

High-purity N2 was used to increase the mobile phase flow rate during ion purification of ion-exchange resin. This was performed to improve the efficiency of isotope separation and puri- fication, and to meet the efficiency requirements of rapid multiple-collector-inductively coupled plasma mass spectrometry （MC-ICPMS） analysis. For Cu isotope separation, our results indicated that at a gas flow rate 〉60 mL/min, the separation chromatographic peaks broadened and the re-covery rate decreased to 〈99.2%. On the other hand, no significant change in the Cu peaks was ob- served at a gas flow rate of 20 mL/min and the recovery rate was determined to be 〉99.9%. The Cu isotope ratio, measured by the standard-sample bracketing method, agreed with reference data within a±2 SD error range. The separation time was reduced from the traditional 10 h （without N2） to 4 h （with N2）, indicating that the efficiency was more than doubled. Moreover, Sr and Nd isotope separation in AGV-2 （US Geological Survey andesite standard sample） accelerated with a 20 mL/min gas flow, demonstrating that with the passage of N2, the purified liquid comprised Rb/Sr and Sm/Nd ratios of 〈0.000 049 and 〈0.000 001 5, respectively. This indicated an effective separation of Rb from Sr and Sm from Nd. MC-ICPMS could therefore be applied to accurately determine Sr and Nd isotope ratios. The results afforded were consistent with the reference data within a±2 SD error range and the total separation time was shortened from 2 d to 〈10 h.

Pay special attention to the transformation products of PPCPs in environment

Pharmaceuticals and personal care products(PPCPs)have received increasing attention.However,their transformation products(TPs)and metabolites,sometimes even with environmental concentration and/or toxicity higher than their parent compounds,received attention far from enough.This study gives useful insight on the occurrence,fate and toxicity of PPCP TPs or metabolites in WWTPs,surface water and even drinking water,highlighting the necessity of studying the PPCP TPs formation,occurrence,toxicity and environment risk,and further evaluating the environmental risk caused by PPCPs comprehensively.

Accurate analysis of Cu isotopes by fs-LA-MC-ICP-MS with non-matrix-matched calibration

The copper isotopic compositions of 12 copper-rich minerals(including native copper,sulfides,carbonates,oxides,and copper chloride)have been determined using a 206 nm ultraviolet femtosecond laser ablation multi-collector inductively coupled plasma mass spectrometry(UV-fs-LA-MC-ICP-MS).A pure copper wire NWU-Cu-B and a natural chalcopyrite TC1725 were used as bracketing standards for calibration.Reliable and precise(2SD<0.07‰)δ^(65) Cu values can be obtained using matrix-matched standards under dry plasma condition and calibrated by the standard-sample bracketing method(SSB).However,theδ^(65) Cu values calibrated by non-matrix-matched standards were seriously affected by matrix effect,with a deviation of up to 1.42‰.Therefore,matrix-matched standards are necessary for reliable in situ Cu isotope ratio measurement.Although the analytical precision(2SD)is slightly improved,the use of Ga as an internal standard combined with the SSB correction does not reduce the deviation caused by the matrix effect.However,the matrix effect can be significantly suppressed by adding 8.6μL min^(–1) water into the carrier gas.The matrix-inducedδ^(65) Cu deviation of the TC1725 calibrated against the pure copper NWU-Cu-B was reduced from 0.99‰in dry plasma mode to 0.03‰in wet plasma mode and achieved a long-term reproducibility of 0.10‰(2SD).For the Cu isotopic compositions of 12 natural copper-rich minerals determined under wet plasma mode,the deviation ofδ^(65) Cu was less than 0.13‰if the mineral is homogeneous.These results indicate that the non-matrixmatched standardization can be achieved by fs-LA-MC-ICP-MS under wet plasma condition,whether using chalcopyrite or pure copper as the external bracketing standards.

Discharge inventory of pharmaceuticals and personal care products in Beijing,China

Pharmaceuticals and personal care products(PPCPs)are emerging environmental contaminants,whose potential risk for the ecological environment has caused wide attention in recent years.In China,quite a large amount of PPCPs were annually emitted into the environment.Their existence in different matrix has been reported frequently,including river water,sediment and soil.However,the contribution from different sources was seldom reported and still unclear in China.Wastewater treatment plant(WWTP)was usually considered to be the main source to the urban river,but livestock and aquaculture farms were also reported as significant pollution sources of PPCPs due to poor environmental management in China.This study summarized environmental discharges of different PPCPs from various sources and obtained the discharge data through different environment media in Beijing,the statistical source of PPCPs was analyzed in detail.The sources comprised WWTPs,excess sludge,hospital wastewater,municipal untreated wastewater,aquaculture wastewater and landfill leachate.This article helps understand the general situation and the potential risk of PPCPs in Beijing.

Magnesium Isotopic Homogeneity of GSR-1 and RGM-2: Two Potential Standards for Mg Isotope Analysis of Low MgO Felsic Rocks

In sample preparation and mass spectrometry analysis,sample dissolution,column chemistry,concentration mismatches,and matrix effects have significant potential for introducing analytical artifacts during Mg isotope analysis.Based on the low MgO content and undesirable matrix elements in felsic rocks,the development of well-characterized felsic standards is essential to reduce inter-laboratory mass bias,enable the assessment of data accuracy,and facilitate the comparison of chemical separation procedures in different laboratories.In this work,the homogeneity and long-term stability of two felsic rock standards,GSR-1 and RGM-2,were evaluated due to their low MgO contents.Furthermore,synthetic solutions with doped matrix elements were used to evaluate potential Mg isotope analytical artifacts using multi-collector inductively coupled plasma mass spectrometry.The accuracy and precision of Mg isotopic compositions in GSR-1 and RGM-2 were assessed by repeated measurements over twelve months.The long-term tests show that the Mg isotopic compositions of the two low MgO felsic rocks(GSR-1 and RGM-2)are homogenous among batches and can be used as low MgO reference materials for accuracy assessments of Mg isotopic analyses.The Mg isotopic compositions(δ26Mg)of GSR-1 and RGM-2 were marked as-0.223‰±0.053‰(2s,n=50)and-0.184‰±0.058‰(2s,n=50)respectively.