How to determine the absolute position of users, such as underwater autonomous vehicles, ships or other long-range vehicles, is a fascinating and challenging issue, especially in global navigation ...satellite system -denied environments. In this article, a bioinspired global autonomous positioning system based on polarized skylight is proposed. By comparing with the related literatures, the system is able to global positioning based on the degree of polarization pattern (DoP) pattern. To be more specific, in an attempt to use the DoP pattern for the geolocalization purposes, a bioinspired polarization compass is designed and in addition, an overall maximum DoP (MDoP) determination algorithm is presented. Moreover, on the basis of the MDoP value, the sun elevation angle can be ultimately measured by using the DoP pattern. The sun elevation angle difference algorithm is used to deduce the absolute position of users. Finally, the bioinspired global autonomous positioning system is developed and validated through experiments. The test results show that the location errors are in range of few kilometers, of which the latitude accuracy is 0.113° (1σ), and the longitude accuracy is 0.082° (1σ).
•Highly-unsaturated and aliphatic compounds accounted a large proportion of DOP.•Phosphate mining in forest land was responsible for the increasing sulfur-containing DOP compounds.•Intense ...anthropogenic activities increased inputs of aliphatic compounds in different reaches.•DOP compounds differed between agricultural runoff and urban runoff under similar precipitation.•Aliphatic DOP compounds in the upper reaches were preferentially used to further promote microbial degradation of biomass.
Land use and precipitation are two major factors affecting phosphorus (P) pollution of watershed runoff. However, molecular characterization of dissolved organic phosphorus (DOP) in runoff under the joint influences of land use and precipitation remains limited. This study used Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) to study the molecular characteristics of DOP in a typical P-polluted watershed with spatially variable land use and precipitation. The results showed that low precipitation and intense human activity, including phosphate mining and associated industries, resulted in the accumulation of aliphatic DOP compounds in the upper reaches, characterized by low aromaticity and low biological stability. Higher precipitation and widespread agriculture in the middle and lower reaches resulted in highly unsaturated DOP compounds with high biological stability constituting a higher proportion, compared to in the upper reaches. While, under similar precipitation, more aliphatic DOP compounds characterized by lower aromaticity and higher saturation were enriched in the lower reaches due to more influence from urban runoff relative to the middle reaches. Photochemical and/or microbial processes did result in changes in the characteristics of DOP compounds during runoff processes due to the prevalence of low molecular weight and low O/C bioavailable aliphatic DOP molecules in the upper reaches, which were increasingly transformed into refractory compounds from the upper to middle reaches. The results of this study can increase the understanding of the joint impacts of land use and precipitation on DOP compounds in watershed runoff.
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•Dispersion compensation technique is the most important issue in the optical communication system to overcome dispersion challenge.•The optimum transmission performance enhancement of optical ...communication system has been realized.•The gain is 126 dB that is recognized within the proposed dispersion compensation model.
Dispersion compensation technique is the most important issue in the optical communication system to overcome dispersion challenges. The current study focuses on a proposed compensation simulation model to handle not only chromatic dispersion (CD) but also polarization mode dispersion (PMD) simultaneously. The present compensation model is designed to analyze and simulate dispersion compensation technique which is based on deploying both fiber Bragg grating and emulator together till 250 km long of optical fiber. Signal to noise ratio (SNR), optical signal to noise ratio (OSNR), gain (G), noise figure (NF) and degree of polarization (DOP) are parameters that simulation depends on.
•Review of environmental redox classifications.•Calibration of commonly used elemental proxies to redox facies.•Analysis of proxies from modern Black Sea, Saanich Inlet, and California Margin.•Use of ...compound covariation of redox proxies to identify key redox thresholds.•No universal proxy values: calibration necessary for each depositional system under study.
Existing redox classifications and the calibrations of elemental proxies to modern environmental redox scales are in need of re-evaluation. Here, we review environmental redox classifications, commonly used elemental redox proxies, and their intercalibration, and we propose a novel approach to improve the calibration of such proxies, using datasets from the modern Black Sea, Saanich Inlet, and California Margin as examples. Our approach is based on recognition of compound covariation patterns among pairs of elemental redox proxies within a redox framework based on three key thresholds: (1) the Re4+/Re3− couple near the suboxidized/subreduced boundary of the suboxic zone, (2) the U6+/U4+ couple in the middle of the subreduced zone, and (3) the SO42−/H2S couple at the suboxic/euxinic boundary. Within this framework, it is possible to determine the relative timing of onset and the degree of enrichment of other elemental redox proxies. Our analysis demonstrates that, even though some elements exhibit limited enrichment within the suboxic zone, the bulk of authigenic enrichment of the redox-sensitive elements considered in this study occurs within the euxinic zone. One important finding of our study is that the threshold value associated with a given elemental proxy can vary considerably between depositional systems. For this reason, it is inadvisable to transfer published threshold values (i.e., from earlier paleoredox studies) to completely different formations, and redox proxies must be internally calibrated for each individual paleodepositional system under investigation.
•Propose a novel FS method, called ISSAFD, which improves Salp Swarm Algorithm (SSA).•ISSAFS enhanced the followers in SSA using SCA and Disrupt operator (DO).•Evaluating the influence of the ...operators of SCA on the behavior of leaders in SSA.•Comparing the performance of ISSAFD with swarm intelligence (SI).•The proposed ISSAFD provided better results in terms of performance measures.
Features Selection (FS) plays an important role in enhancing the performance of machine learning techniques in terms of accuracy and response time. As FS is known to be an NP-hard problem, the aim of this paper is to introduce basically a new variant of Salp Swarm Optimizer (SSA) for FS (called ISSAFD (Improved Followers of Salp swarm Algorithm using Sine Cosine algorithm and Disrupt Operator), that updates the position of followers (F) in SSA using sinusoidal mathematical functions that were inspired from the Sine Cosine Algorithm (SCA). This enhancement helps to improve the exploration phase and to avoid stagnation in a local area. Moreover, the Disruption Operator (Dop) is applied for all solutions, in order to enhance the population diversity and to maintain the balance between exploration and exploitation processes. Two other variants of SSA are developed based on SCA called ISSALD (Improved Leaders of Salp swarm Algorithm using Sine Cosine algorithm and Disrupt Operator) and ISSAF (Improved Followers of Salp swarm Algorithm using Sine Cosine algorithm). The updating process in consists to update the leaders (L) position by SCA and applying (Dop), whereas in ISSAF, the Dop is omitted and the position of followers is updated by SCA. Experimental results are evaluated on twenty datasets where four of them represent high dimensionality with a small number of instances. The obtained results show a good performance of ISSAFD in terms of accuracy, sensitivity, specificity, and the number of selected features in comparison with other metaheuristics (MH).
The influence of slag basicity and CrO content on the viscosity of CaO–SiO2–2%MgO–CrO slags has been experimentally determined. The slag viscosity decreases with increasing basicity, CrO and Cr2O3 ...content. Both MgO and CrO have a basic characteristic and the CrO acts as a network modifier. The activation energy of the CrO content further validates these observations. The degree of polymerization is also found to decrease with the addition of CrO.
Plastic debris is accumulating in agricultural land due to the increased use of plastic mulches, which is causing serious environmental problems, especially for biochemical and physical properties of ...the soil. Dissolved organic matter (DOM) plays a central role in driving soil biogeochemistry, but little information is available on the effects of plastic residues, especially microplastic, on soil DOM. We conducted a soil-incubation experiment in a climate-controlled chamber with three levels of microplastic added to loess soil collected from the Loess Plateau in China: 0% (control, CK), 7% (M1) and 28% (M2) (w/w). We analysed the soil contents of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), NH4+, NO3−, dissolved organic phosphorus (DOP), and PO43− and the activities of fluorescein diacetate hydrolase (FDAse) and phenol oxidase. The higher level of microplastic addition significantly increased the nutrient contents of the DOM solution. The lower level of addition had no significant effect on the DOM solution during the first seven days, but the rate of DOM decomposition decreased in M1 between days 7 and 30, which increased the nutrient contents. The microplastic facilitated the accumulation of high-molecular-weight humic-like material between days 7 and 30. The DOM solutions were mainly comprised of high-molecular-weight humic-like material in CK and M1 and of high-molecular-weight humic-like material and tyrosine-like material in M2. The Microplastic stimulated the activities of both enzymes. Microplastic addition thus stimulated enzymatic activity, activated pools of organic C, N, and P, and was beneficial for the accumulation of dissolved organic C, N and P.
•Microplastic addition stimulated soil activity of fluorescein diacetate hydrolase (FDAse) in soil.•The lower level of microplastic addition had a negligible effect on the nutrient contents in DOM solution at day 30.•The higher level of microplastic addition significantly increased the nutrient contents in DOM solution.
As a typical semiconductor, ZnO is considered as a favorable photocatalyst due to its excellent photoelectrochemical properties. However, low response of visible light and the recombination of ...photoinduced carriers limits its application in photocatalysis. Herein, a novel, robust and recyclable heterogeneous photocatalyst based on flower-like Co doped ZnO microspheres was presented without changing the hierarchical morphology. The crystal structure, light absorption, and electrochemical performance were systematically investigated, and the response of Co doped ZnO to visible light significantly enhanced with the gap band reduced from 3.20 eV to 2.54 eV. Due to the transformation of Co2+ to Co3+, more oxygen vacancies were produced, with more photoinduced electrons transferring to Co3+ which would greatly inhibit the recombination of photoinduced electrons and holes and improve photocatalytic activity. 2-Mercaptobenzothiazole (MBT) which is considered as a long half-life intermediate of antibiotic medicine is chosen as a target. As a result, the 7% Co-ZnO photocatalyst exhibited excellent photocatalytic activity for the degradation of MBT with the rate constant of 0.1498 min−1 and removing ratio of 97.3% in 50 min. The formation of excess oxygen vacancies and the conversion between Co2+ to Co3+ were further identified by XPS analysis. This work provides new sights for doping transition metal with different chemical valence in semiconductors for producing oxygen vacancy and improving the photocatalytic efficiency.
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•A novel and recyclable heterogeneous flower-like Co doped ZnO microspheres is prepared via simple procedure.•Doping of Co species effectively reduces the band gap energy of ZnO with the formation of abundant oxygen vacancies.•Electrons are trapped due to the transformation of Co2+ and Co3+ which hinders the recombination of photo-induced carriers.•The formation of oxygen vacancies and the conversion between Co2+ to Co3+ are further identified by XPS analysis.•The prepared photocatalyst exhibits excellent photocatalytic activity for degradation of 2-mercaptobenzothiazole.
The positioning accuracy of global and regional navigation satellite systems (GNSS/RNSS) depends on a variety of influence factors. For constellation-specific performance analyses it has become ...common practice to separate a geometry-related quality factor (the dilution of precision, DOP) from the measurement and modeling errors of the individual ranging measurements (known as user equivalent range error, UERE). The latter is further divided into user equipment errors and contributions related to the space and control segment. The present study reviews the fundamental concepts and underlying assumptions of signal-in-space range error (SISRE) analyses and presents a harmonized framework for multi-GNSS performance monitoring based on the comparison of broadcast and precise ephemerides. The implications of inconsistent geometric reference points, non-common time systems, and signal-specific range biases are analyzed, and strategies for coping with these issues in the definition and computation of SIS range errors are developed. The presented concepts are, furthermore, applied to current navigation satellite systems, and representative results are presented along with a discussion of constellation-specific problems in their determination. Based on data for the January to December 2017 time frame, representative global average root-mean-square (RMS) SISRE values of 0.2 m, 0.6 m, 1 m, and 2 m are obtained for Galileo, GPS, BeiDou-2, and GLONASS, respectively. Roughly two times larger values apply for the corresponding 95th-percentile values. Overall, the study contributes to a better understanding and harmonization of multi-GNSS SISRE analyses and their use as key performance indicators for the various constellations.
While rules and exemplars are usually viewed as opposites, this paper argues that they form end points of the same distribution. By representing both rules and exemplars as (partial) trees, we can ...take into account the fluid middle ground between the two extremes. This insight is the starting point for a new theory of language learning that is based on the following idea: If a language learner does not know which phrase‐structure trees should be assigned to initial sentences, s/he allows (implicitly) for all possible trees and lets linguistic experience decide which is the “best” tree for each sentence. The best tree is obtained by maximizing “structural analogy” between a sentence and previous sentences, which is formalized by the most probable shortest combination of subtrees from all trees of previous sentences. Corpus‐based experiments with this model on the Penn Treebank and the Childes database indicate that it can learn both exemplar‐based and rule‐based aspects of language, ranging from phrasal verbs to auxiliary fronting. By having learned the syntactic structures of sentences, we have also learned the grammar implicit in these structures, which can in turn be used to produce new sentences. We show that our model mimicks children’s language development from item‐based constructions to constructions, and that the model can simulate some of the errors made by children in producing complex questions.
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