Search

BeiDou high-precision power line inspection can improve the efficiency and automation level of inspection operations, reduce labor intensity, and save inspection costs. However, although the satellite-based augmentation technology can solve the problem of large-scale positioning, it will introduce too many parameters into the positioning system through the method of parameter estimation. As a result, the behavior of the equation deteriorates, which makes it difficult to separate some parameters, and the convergence time of ambiguity parameters is too long. Under normal circumstances, the satellite-based augmentation standard positioning service needs at least about 30 min to converge to the centimeter level, and the ground-based augmentation system can provide an accurate model. This paper proposes a fast positioning method for satellite-based augmentation assisted by the BeiDou ground-based augmentation station. The receiver adopts the least square method, combined with the extended Kalman filter positioning, to achieve the improvement of the regional positioning effect of the satellite-based augmentation system. Positioning accuracy error does not exceed 1.6 meters. The error in the three directions of X, Y, and Z can be converged to the centimeter level in about 8 min. It can significantly improve the convergence time of satellite-based augmentation, and maintain continuous, stable and high-precision positioning of unmanned aerial vehicle in power line inspection.

Micro-shocks may happen when the human body is close to high-voltage transmission lines. Experiments near the actual operating ±1100 kV high-voltage direct current (HVDC) lines with a metal human body model (HBM) are conducted. The voltages on the HBM and the micro-shock currents are measured. A micro-shock simulation method in the ion flow field is presented according to the measured results. Based on the simulation method, the variations of current, charge and energy on the HBM during the micro-shock process are investigated. The influences of resistance and capacitance parameters on micro-shock currents are analysed. Furthermore, a simplified simulation method is given to estimate the micro-shock currents for the potential demand of engineering practice.

Many fullerenes and carbon nanotubes have the very large electrophilic regions on their molecular surfaces. The existence of these large electrophilic regions is beyond the scope of the concept of the σ-hole and π-hole which were introduced to describe the formation of the noncovalent bonds. The inner cavities of many fullerenes and carbon nanotubes are the regions of positive electrostatic potential, and are electron-withdrawing in character. Our results clearly show that it is the electron-withdrawing cavity not the curvature of the fullerene or carbon nanotube that plays a dominant role for the formation of the large electrophilic regions on the molecular surface. The important role of the large electrophilic regions of fullerenes has been illustrated by using them to successfully explain some experimental observations in crystal engineering.

When an overhead high voltage direct current (HVDC) line is near a greenhouse, surface charges on the dielectric film distort the electric field nearby. Extensive experimental researches have been conducted regarding charge characteristics, and various algorithms have been proposed to calculate the ion flow field considering the charged film. However, existing studies do not consider the greenhouse support structures. In this paper, based on the ion flow field simulation with charged film, a more complete greenhouse model considering support structures is built. The support structures are treated as grounded conductors. Experimental results agree well with the calculations. Then, the influences of the frames and the wall (two typical types of support structures) are analyzed separately. The analysis considers the frame radius, position, and number, as well as the wall position and width. The total electric field is divided into three parts by charge sources, the effects of which are analyzed separately. The co-effect of the two kinds of support structures is also analyzed. The calculations show that the support structures, which are conductive and grounded, can effectively reduce the ground-level electric field. This research can predict the absolute value and help us understand the characteristics of the actual electric field near a greenhouse built under overhead HVDC lines.

The experimentally isolated Y2C2@C1(1660)-C108 fullerene has been computed using density functional theory method. Optimized structure shows that the incorporation of the Y2C2 cluster in the fullerene IPR (isolated-pentagon-rule) C1(1660)-C108 has little impact on the structure of the carbon cage. The electrostatic potential analysis reveals that C1(1660)-C1084− inside the cage cavity have two potential energy minima. The two Y atoms in Y2C2@C1(1660)-C108 occupy near the minima, which are consistent with the X-ray structure. The electronic structure, ionization potential, electron affinity, 13C NMR chemical shift, UV–vis-NIR and infrared absorption spectra of this endofullerene have been calculated. The simulated UV–vis-NIR spectrum of Y2C2@C1(1660)-C108 agrees well with the experimental results.

Very recently, two novel monometallic cluster fullerenes YCN@C s (6)–C 82 and TbCN@C 2 (5)–C 82 are prepared and characterized, respectively. Inspired by these findings, the possibility of encapsulating MCN (M = Sc, Y) cluster in the C 76 fullerene has been performed using density functional theory. Six isomers of MCN@C 76 are considered based on six lowest energy C 76 2 − isomers. The results show that two non-IPR MCN@C 2 v (19,138)–C 76 and MCN@C 1 (17,459)–C 76 present excellent thermodynamic stability with very small energy differences. Significantly, in both the structures, the entrapped MCN cluster is linear, but not triangular. This is different from the results reported on YCN@C s (6)–C 82 and TbCN@C 2 (5)–C 82 . Furthermore, IR spectra and 13 C NMR spectra have also been explored to assist future experimental characterization.

The adsorption of hydrogen and fluorine atoms on the interior surface of defect-free and Stone–Wales defect armchair (5,5) single-walled carbon nanotubes were investigated using density functional theory. The reaction energy values for the hydrogenation and fluorination at all the possible unique sites were obtained at the UB3LYP/6-31G * level. The calculated reaction energy values were used to corroborate the reactivities of different sites on the interior surface of SWCNTs. The results indicate that for defect-free nanotube, endohedral adsorption is rather unfavorable both for hydrogen and fluorine. The computed exothermicities range from 4.8 to 13.4 kcal/mol for hydrogenation and from 16.6 to 23.2 kcal/mol for fluorination. However, the introduction of a SW defect on the (5,5) SWCNT improves the chemical reactivity of the interior surface of the defected tube. The computed exothermicities for the endohedral hydrogen and fluorine atoms are within the ranges of 7.0–33.4 and 18.5–41.8 kcal/mol, respectively. The most exothermic and reactive site on the interior surface of SW defective (5,5) SWCNT is the C2 site shared by two seven-membered rings and one five-membered ring. This is different from the results reported on the reactivity of the exterior surface of SW defective nanotubes. The electronic and vibrational properties of the (5,5) SWCNTs with adsorption of hydrogen and fluorine atoms on the interior surface were also explored.

Stimulated by recent preparation and characterization of two new endohedral cluster fullerenes Sc 3 NC@C 80 and Sc 3 NC@C 78 , we have performed systematic density functional studies on the geometrical structures and electronic properties of the D 5h isomer of Sc 3 NC@C 80 at the B3LYP/6-31G * level. For the sake of comparison, the geometrical structures and electronic properties of the experimentally available I h Sc 3 NC@C 80 , D 5h and I h Sc 3 N@C 80 have also been investigated at the same level of theory. The results show that the encapsulated Sc 3 NC cluster adopts a planar structure inside the D 5h C 80 cage, similar to the case of I h Sc 3 NC@C 80 . D 5h Sc 3 NC@C 80 is 18.95 kcal/mol higher in energy than I h Sc 3 NC@C 80 , agreeing well with the relative energies of Sc 3 N@C 80 . D 5h Sc 3 NC@C 80 has a large HOMO–LUMO gap of 1.77 eV. More importantly, the predicted binding energy (253.0 kcal/mol) of D 5h Sc 3 NC@C 80 is even larger than that (247.4 kcal/mol) of the synthesized D 5h Sc 3 N@C 80 , suggesting a considerable possibility for experimental realization. The Raman spectrometry of this a new endofullerene has been explored to assist future experimental characterization.

The geometrical structures and electronic properties as well as thermal stabilities of hydrogenated armchair ( n , n ) ( n = 4–8) SWCNTs with Stone–Wales (SW) defect were investigated using density functional theory (DFT-B3LYP) in combination with the 6-31G * basis set. It is found that the chemisorptions of two hydrogen atoms inside and outside the SW defective SWCNTs are exothermic processes. As the nanotube diameter increases, the reaction energy of exohedral addition decreases, whereas that of endohedral addition increases. Exohedral nanotube adsorption is energetically more favorable than endohedral adsorption for smaller diameter (4, 4)-SW, (5, 5)-SW SWCNTs, but not for larger diameter (7, 7)-SW and (8, 8)-SW SWCNTs. The result is different from hydrogen on perfect nanotubes. Significantly, compared with the adsorption on the exterior sidewalls of perfect SWCNTs, the reaction energies of the endo-hydrogenated (7, 7)-SW and (8, 8)-SW SWCNTs are more exothermic, meaning that the central C C bond of SW defect inside the armchair (7, 7)-SW and (8, 8)-SW SWCNT sidewalls is more reactive than that in perfect sites. This is different from the result reported on the sidewall reactivity of SW defects outside the armchair SWCNTs. The calculated energy gaps indicate that the hydrogen-chemisorbed SW defective armchair tubes are always wide energy gap structures. The energy gaps of endohedral hydrogen-chemisorbed tubes are higher than those of the corresponding perfect tubes.

Based on the recently isolated and characterized of the nanotube-like D 5h C 90 fullerene, a theoretical study of the interaction between oxygen atom and C 90 ( D 5h ) has been performed using density functional theory (DFT-B3LYP) in combination with the 6-31G ∗ and 6-31+G ∗ basis sets. The geometrical structures and electronic properties as well as thermal stabilities of the systems considered have been investigated. The results show that the e,e–C 90 O isomer with annulene-like structure is the most stable one, where the oxygen atom is added to the [6,6] bond near the equatorial region of C 90 . Concerning the six isomers of C 90 O 2 considered, it is found that the e,e,e,e–C 90 O 2 (I) isomer with the two annulene-like structures is the most stable one, where two oxygen atoms are all added to the e-e bonds on the same six-membered ring near the equatorial belt of C 90 . The calculated reaction energy per oxygen indicates that the double-adsorption product is more energetically favorable than the monoadsorption one. Further, we consider the structures of the chemisorption of more oxygen atoms and show the high stability of C 90 O 45 which has larger HOMO–LUMO gap, higher adiabatic ionization potential (AIP), and lower adiabatic electron affinity (AEA) than both C 90 O and C 90 O 2 .

Stimulated by recent preparation and characterization of the first C50Cl10 fullerene derivative with five fused pentagons and four novel chlorinated fullerene derivatives, C54Cl8, C56Cl12, C66Cl6 and C66Cl10 with the triple sequentially fused pentagons, 30 exohedral chlorine derivatives of small fullerenes C30–C48 have been reported here. The geometrical structures and electronic properties of them are studied using density functional theory (DFT) at the B3LYP/6-31G∗ level. The HOMO–LUMO gaps, reaction energies, and aromaticities commonly used for chemical viability of chlorinated small fullerenes were compared with these values of the two most stable fullerene derivatives C50Cl10 and C60Cl30. The presented data reveal that many unknown fullerene derivatives are stable molecules, especially for C32Cl20 (3, D3d), C36Cl18 (13, D3h), and C40Cl16 (40, Td). The stable behavior of them resembles the well-known C50Cl10. It is quite possible that they can be synthesized experimentally in the solid after C50.

The geometrical structures and electronic properties of six fullerene isomers of C100 were studied at the HF/6-31G⁎ and B3LYP/6-31G⁎ levels, respectively. The results of the fully optimized calculations show that three C100 isomers 449:D2, 425:C1 and 442:C2 are near isoenergetic isomers. The energies and properties of C100 hexaanions were calculated. The C1006− (450:D5) isomer is predicted to be the most stable isomer at the B3LYP/6-31G⁎ level, and the C1006− (449:D2) isomer is 44.1 kcal/mol higher in energy. The heterofullerenes C96X4 (X=N, P, B, Si) formed from the initial C100 (449:D2) have also been investigated at the B3LYP/6-31G⁎ level. The HOMO–LUMO gaps and aromaticities show that the replacement of fullerene carbon atoms with four heteroatoms can enhance the electronic stabilization of C100 (449:D2).

The structural and electronic properties of hydrogenated armchair and zigzag SWCNTs with carbon ad-dimer (CD) defect were investigated by means of the B3LYP hybrid density functional method using 6-31G∗ basis set. It is found that the chemisorptions of two hydrogen atoms inside and outside the CD defective SWCNTs are exothermic processes. Exohedral nanotube adsorption is energetically more favorable than endohedral adsorption. These results are in agreement with hydrogen on pristine nanotubes. The positional preference for the chemisorption of two hydrogen atoms is the same for the CD defective armchair and zigzag nanotubes. However, the reaction energy of two hydrogen atoms on the exterior sidewalls of CD defective SWCNTs is almost independent of the tube diameter. This is different from the results reported on pristine nanotubes. The calculated energy gaps indicate that the hydrogen-chemisorbed CD defective armchair tubes are always wide energy gap structures, while the hydrogen-chemisorbed CD defective zigzag tubes have significantly lower gaps. The HOMO–LUMO gap and reaction energy for the chemisorption of more hydrogen atoms on the exterior sidewalls of CD defective armchair SWCNTs were also explored.

Ab initio and density functional theory (DFT) methods at the HF/6-31G*, B3LYP/6-31G*, MP2/6-31G*, and MP2/TZVP levels of theory were applied to the investigation of the relative stability of six fullerene isomers of C32. Full geometry optimization of the systems was carried out and electrostatic potential distributions were calculated. The effect of electron correlation on the electrostatic potential distribution of C32 isomers was analyzed.