Airborne light detection and ranging (LiDAR) bathymetry (ALB) is an effective technique for seamless topobathymetric mapping in shallow water. A green laser beam spreads due to the forward scattering ...effect in the water column, which significantly influences the shape of seafloor reflected waveforms and further introduces bathymetric error. To quantitatively analyze the water column forward scattering effect, this study develops an ALB waveform simulator (ALBWS) based on the semianalytical Monte Carlo numerical simulation (MCNS) and Fournier-Forand (FF) phase function. The ALBWS is first verified by waveforms collected by the Chinese Academy of Sciences Mapper5000 and Optech Aquarius ALB systems around Yuanzhi Island in the South China Sea. Then, based on the ALBWS, the specific bathymetric error and received energy influenced by the forward scattering effect are quantitatively investigated under different system and environmental parameters. Please note that the bathymetric error is obtained by processing noiseless waveforms using the centroiding algorithm. The results indicate that, when the water quality varies from Type I (clear) to Type II (coastal) at a depth of 30 m, the bathymetric error due to the forward scattering effect alone increases from 40 cm to 70 cm, which no longer satisfies the requirements of IHO S44 Level 1a. To achieve more accurate bathymetric results, the ALB collection should be conducted in water areas where the particle size distribution slope is less than 3.91. Moreover, the ALB system can acquire higher bathymetric accuracy and received energy when the instantaneous field of view is approximately 3-11 times greater than the laser divergence angle. This study proposes a robust and flexible model to evaluate the scattering influence on ALB systems, which is not only beneficial for acquiring and processing ALB data but also helpful for optimizing the design of ALB system configurations.
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•A new method to derive very shallow water depth and improve minimum detection depth.•Extracting water surface and bottom positions from mixed peaks by a combined model.•A Mapper5000 ...ALB dataset near South China Sea is applied to validate this method.•Providing a new solution to bridge the bathymetric data gap.
Airborne LiDAR bathymetry (ALB) is an active remote sensing technology for deriving underwater topography by detecting surface and bottom signals with a scanning green channel (532 nm) laser. However, due to the limitations of laser pulse duration and receiver bandwidth, the surface and bottom signal contributions are typically mixed in the green channel waveform in very shallow water (<2 m water depth). To address this issue, this paper proposes an ALB waveform decomposition method based on a signal resolution enhancement model and fractional differentiation mathematical tool in very shallow water. The initial Gaussian decomposition parameters of the surface and bottom are determined first. Then, the accurate surface and bottom positions are discriminated optimally using the Levenberg-Marquardt algorithm. Finally, the proposed method is verified by a green channel waveform dataset, which is obtained by the Mapper5000 ALB system of the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences. The root mean square error (RMSE) of the surface position differences is 0.62 ns (that is, the ranging distance is 7.0 cm), which is less than the sampling frequency of 1 ns. Moreover, the mean correlation coefficient between the waveform processed results and the actual data is 0.9950. The presented method not only shows good accuracy and robustness in estimating the surface and bottom components from such mixed peaks but also contributes to improving the minimum penetration depth of the ALB system.
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•Graphene oxide sheets modulate ultramicroporous region of milk colloid-derived carbon.•Synergy of graphene oxide and metal oxide leads carbon to an advanced pore system.•Milk ...colloid-derived carbon shows excellent capacitance by synergetic modulation.
Biomass-derived carbon has great potential as electrode for supercapacitors or batteries, and the rational design and modulation of the porous structure is the key for advanced electro-chemical property. Herein, graphene oxide (GO) sheets and metal oxide particles templates were introduced for modulating the ultramicropores (less than 1 nm) and supermicropores/mesopores (∼ 2 nm) of porous carbon derived from milk colloid, aiming to exploring the potential of biomass-derived carbon as supercapacitor electrodes. Through the synergetic modulations of GO and metal oxide particles, the proposed supercapacitor materials (G-NP-MPC) exhibit high gravimetric (358.4 F/g)/areal (3.58 F/cm2)/volumetric capacitance (277.5 F/cm3) at mass loadings of 10 mg/cm2 in aqueous electrolyte, which accomplishes remarkable improvement of carbon directly derived from milk colloid (181.1 F/g, 1.81 F/cm2 and 140.3 F/cm3) without pore modulation. Apart from aqueous electrolyte, the symmetric supercapacitor (G-NP-MPC) also exhibits relatively high energy density (43.0 W h/kg at the power density of 300 W/kg) in organic electrolyte with the potential window of 3 V. This work amplifies the function of graphene oxide sheets and metal oxide, which can corporately tune the pore size distribution in a narrow scope for enhancing integrated capacitance of biomass-derived carbon.
Illicium difengpi K.I.B. et K.I.M. is a member of the Illiciaceae family with a yet not fully explored utilization value. To provide references for the systematic understanding of I. difengpi ...(Illiciaceae), the morphological and structural characteristics, wild resource distribution, chemical compounds, pharmacological effects, utilization, and protective measures of this species are reviewed. We conclude that (i) I. difengpi (Illiciaceae) is an endemic and indigenous medicinal species that has been used to treat rheumatoid arthritis and traumatic injury in China; (ii) I. difengpi (Illiciaceae) can endure various abiotic stresses, especially extreme drought, and thus has scientific value for exploring adaptive mechanisms of tolerance to extreme drought and in the ecological restoration of karst rocky desertification areas; and (iii) the beautiful tree shapes of I. difengpi (Illiciaceae) give it potential ornamental value. However, the wild resources of I. difengpi (Illiciaceae) have rapidly decreased, and there is an urgent need to protect this endangered species to maintain its diversity. Protection measures include the protection of wild germplasm resources, the establishment of an I. difengpi (Illiciaceae) germplasm resource bank, and the development of large-scale ecological planting techniques. In further research, the medicinal and scientific value of I. difengpi (Illiciaceae) should be systematically explored to clarify the plant’s effective pharmaceutical value, clinical applications, mechanisms of drought adaptation, and genetic diversity.
A new transesterification method for preparing N, N-dimethylaminoethyl acrylate (DMAEA) from methyl acrylate (MA) and dimethylaminoethanol (DMAE) was carried out in the presence of organotin ...catalyst. Among the catalysts examined, (C8H17)2Sn(OCOC11H23)2(TD) is the most active one for the reaction. The products were characterized by gas chromatography, IR spectroscopy, NMR spectroscopy and Mass spectroscopy. The effects of various reaction conditions such as the different catalysts, the reactants ratio, the amount of catalyst, the reaction time on the DMAE conversion, the selectivity to DMAEA and the DMAEA yield were investigated. Experimental results indicated that the sort of catalyst is vital to improving DMAEA yield. The reactants ratio could effect on the DMAE conversion, the selectivity to DMAEA and the DMAEA yield. The 96.28% conversion of DMAE was obtained over catalyst TD, the yield of DMAEA could reach 94.65%, the selectivity is 98.68%. A possible catalytic mechanism of transesterification of DMAE and MA with organotin catalysts was also presumed.
A series of Na3YSi2O7: Eu3+, Sm3+ samples have been synthesized via solid-state reaction technique. The phase structure and luminescence properties are characterized using powder X-ray diffraction, ...photoluminescence excitation and emission spectra. Effective energy transfer occurs from Sm3+ to Eu3+ and Sm3+/Eu3+-codoped Na3YSi2O7 shows more intense red light compared to that of Eu3+-doped sample under UV light excitation.
To develop the data mining capability of airborne LiDAR bathymetry (ALB) waveform information, the waveform decomposition and feature extraction algorithm of airborne LiDAR bathymetry is proposed in ...this paper. This method uses the "separate" and "combine" two-step optimized waveform decomposition algorithm to decompose the bottom contribution waveform and extract 7 waveform feature parameters. To verify the effectiveness of this algorithm, it is applied to Yuanzhi Island ALB data. The experimental results showed that the average root mean square error (RMSE) of waveform decomposition is 11.75; the average coefficient of determination (R 2 ) is 0.983, and the extraction time for every 500 sets of data is only 0.24 s. After classing coral reefs using the extracted ALB waveform features, the overall accuracy of coral reef information extraction are 2.27%,3.84%, and 4.02% improved with K-Nearest Neighbor (KNN), Support Vector Machine (SVM), and Random Forest (RF) methods, respectively, compared with the previous waveform features.
Nonlinear least square is one of the unconstrained optimization problems. In order to solve the least square trust region sub-problem, a genetic algorithm (GA) of global convergence was applied, and ...the premature convergence of genetic algorithms was also overcome through optimizing the search range of GA with trust region method (TRM), and the convergence rate of genetic algorithm was increased by the randomness of the genetic search. Finally, an example of banana function was established to verify the GA, and the results show the practicability and precision of this algorithm.
Modal analysis of a simply supported beam with elastic support in vertical direction was conducted. Based on Bernoulli-Euler beam model, the first three nature frequency equations and the vibration ...mode function were obtained. And with different stiffness in vertical direction, the nature frequency equations were solved using numerical method, at the same time, curves of the relationship between support stiffness and nature frequency were acquired, and the corresponding functions were fitted with least square method simultaneously. Based on a typical beam structure, the accuracy of the functions was validated using finite element method, and the relative error was less than 3%.
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