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Traditional iterative closest point (ICP) registration algorithms are sensitive to initial positions and easily fall into the trap of locally optimal solutions. To address this problem, a point cloud registration algorithm is put forward in this study based on adaptive neighborhood eigenvalue loading ratios. In the algorithm, the resolution of the point cloud is first calculated and used as an adaptive basis to determine the raster widths and radii of spherical neighborhoods in the raster filtering; then, the adaptive raster filtering is implemented to the point cloud for denoising, while the eigenvalue loading ratios of point neighborhoods are calculated to extract and match the contour feature points; subsequently, sample consensus initial alignment (SAC-IA) is used to carry out coarse registration; and finally, a fine registration is delivered with KD-tree-accelerated ICP. The experimental results of this study demonstrate that the feature points extracted with this method are highly representative while consuming only 35.6% of the time consumed by other feature point extraction algorithms. Additionally, in noisy and low-overlap scenarios, the registration error of this method can be controlled at a level of 0.1 mm, with the registration speed improved by 56% on average over that of other algorithms. Taken together, the method in this study cannot only ensure strong robustness in registration but can also deliver high registration accuracy and efficiency. [ABSTRACT FROM AUTHOR]

In order to ensure safe lane change and avoid traffic accidents, an effective lane change assist system is required. In a lane change assist system, it is very important to obtain the following elements in time, such as actual distance between vehicles, minimum safety distance, and warning signal. To this end, this paper analyzed four kinds of lane change angle collision scenes. Initial position, initial velocity, acceleration, heading angle, and kinematics of vehicles were used to calculate the position of potential angle collision points between lane change vehicle and obstacle vehicles. Then, actual distance model was constructed based on potential angular collision points. The minimum safety distance model was also established under the two most unfavorable conditions. In order to achieve the lane change warning, three early warning rules were formulated. We verified the validity of models and early warning rules using vehicle driving video data of Interstate 80 in California. Models and early warning rules constructed in our research can be applied to the advanced active safety systems of vehicle, such as vehicle lane change assist system and active collision early warning system, which can improve the active safety and reduce traffic accidents., 1. Introduction Lane change is a relatively complicated process for driving vehicles. Drivers' improper operation during lane change may cause traffic delays and accidents. According to incomplete statistics, lane change [...]

Current transformer (CT) saturation is one of the dominant causes of relay protection devices’ malfunctions, which pose a threat to the safe operation of the power system. To address this problem, we propose a hybrid physical model- and data-driven method. The method firstly detects the CT saturation and then compensates it to reproduce the real waveform. Considering the multi-factor and strong nonlinearity of CT saturation, a data-driven model, namely the Fully Convolutional Network (FCN), is built to detect the operation status of CT. As for the compensation, a physical model of short-circuit current is used for its conciseness and universality. Through tactfully integrating the data model and the physical model, the proposed method is endowed with two major merits: the arduous adjustment of universal thresholds and parameters in existing methods is avoided, and the deficiency in generalization and interpretability of the data-driven method is assuaged. Simulation and experimental results verify the effectiveness of the proposed method. Furthermore, its application potential to future protection is explored. [ABSTRACT FROM AUTHOR]

In recent years, the sub‐/super‐synchronous oscillation (SSO) caused by grid integration of direct‐drive permanent magnet synchronous generators (D‐PMSG) has attracted wide attention. However, most of the existing stability analysis methods are either complex or cannot quantitatively analyze the influence of parameter changes on system stability. To address the problems, this paper proposes a novel stability analysis method for SSO in the D‐PMSG integrated power system based on closed‐loop transfer function poles. Firstly, the impedance modeling method was introduced to analyze the stability of the D‐PMSG power system. Then, a stability criterion was proposed based on the poles of the closed‐loop function. The proposed criterion is simple and has a clear physical background. The real part of the poles represents the damping while the imaginary part of the pole reflects the oscillation frequency. Finally, simulation results verify the accuracy and effectiveness of the proposed method. Moreover, its application in influence factors for quantitative analysis was also validated. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Purpose : Soil organic carbon (SOC) dynamics strongly affect the terrestrial carbon balance, and stable isotopic measurements provide detailed information about SOC cycling. However, the response of δ13C and SOC to climatic factors is still not well known in high alpine regions. Methods: In this study, soil δ13C and SOC in vertical soil profiles were analysed at alpine grassland sites along four precipitation gradients (350–400, 450–500, 550–600, and 650–700 mm) on the eastern Qinghai–Tibetan Plateau. The β value is defined by the slope of the linear regression relating soil δ13C to the logarithm of SOC, and the higher β values represent slower SOC turnover. Results: The SOC concentration tended to decline with increasing soil depth from 0 to 40 cm, while δ13C was enriched in alpine grassland on the eastern Qinghai–Tibetan Plateau. The δ13C values in the 650–700-mm class were relatively depleted compared with other precipitation classes. Redundancy analysis (RDA) showed that altitude was the most important factor—explaining 20.9% of the variation in 13C in surface soil (0–10 cm), followed by mean annual air temperature (MAT) (17.1%) and mean annual precipitation (MAP) (16.9%). MAT and altitude were the main factors controlling δ13C and β values. MAP did not significantly affect SOC distribution, but lower δ13C and β values occurred with higher precipitation. Correlations between SOC content and MAT increased significantly after removing relationships with MAP. Conclusions: The results indicate that faster SOC decomposition may not necessarily lead to SOC losses on the eastern Tibetan Plateau given current conditions. Future research should consider the effects of interactions between warmer and wetter conditions (predicted under climate change) on SOC content and turnover. [ABSTRACT FROM AUTHOR]

Soil enzyme activities in different plantation types and land use patterns could indicate changes in soil quality. This research was aimed at exploring the dynamics of soil enzyme activities involved in carbon, nitrogen and phosphorus cycling, and their responses to changes in soil physicochemical properties resulting from natural vegetation restorations and plantation schemes. Knowing about the effects of soil physicochemical properties on soil enzyme patterns is crucial for understanding ecosystem functions and processes. The study selected four main land-use types (natural forestland, natural grassland, artificial forestland, and artificial grassland) and one control plot (bare land) in the West Qinling Mountains, China, which is a typical landslide region. We collected the soil samples from each land use type and tested their physicochemical properties and enzyme activities compared with control land. The results showed that both natural vegetation restoration and artificial plantation schemes have significant effects on enzyme activities. Soil physicochemical properties explained 92.2% of the variation in soil enzyme activities for natural vegetation restoration, while it only explained 77.8% of the variation in soil enzyme activities for plantation schemes. Furthermore, natural vegetation had a greater effect than the plantation schemes on soil enzyme activities. [ABSTRACT FROM AUTHOR]

In this paper, the holomorphic embedding power flow method (HELM) is designed to solve the AC/DC hybrid power flow equations. According to the power flow model of the high voltage direct current systems (HVDC), an appropriate embedding technique with three recursive algorithms is developed for three different control modes, which is compatible with existing achievements of HELM for AC systems. In this method, the advantages of HELM, such as non-iterative, deterministic and non-ambiguous, are fully retained. In addition, a new calculation strategy based on Bauer's Eta algorithm is designed for the implementation of Padé approximations and the recursive process to avoid redundant calculations without reducing accuracy. In order to verify the reliability and effectiveness of the proposed extended HELM, several power flow cases with different scale are studied by HELM and traditional iterative method. [ABSTRACT FROM AUTHOR]

We have used three-wavelength UV-spectrophotometry to study the reaction of the alkaline fading of phenolphthalein in the critical solution of 2-butoxyethanol + water. It was found that when the temperature was far away from the critical point, the values of the natural logarithm of the rate constant k and the natural logarithm of the chemical equilibrium K determined in our experiments had good linear relationships with the reciprocal of temperature, which served as the backgrounds and were used for correcting k and K in the critical region. The critical slowing down of the reaction and the critical anomaly of the chemical equilibrium were detected near the critical point. The value of the critical exponent characterizing the slowing down effect of the reaction rate was obtained to be 0.156, which was close to the value 0.11 associated with the heat capacity divergence and agreed with the theoretical prediction. The experimental result also confirmed the theoretical prediction of 0.11 for the critical exponent characterizing the weak divergence of the singularity of the chemical equilibrium. [ABSTRACT FROM AUTHOR]

With the development of PMUs in power systems, the response-based real-time emergency control becomes a promising way to prevent power outages when power systems are subjected to large disturbances. The first step in the emergency control is to start up accurately and fast when needed. To this end, this paper proposes a well-qualified start-up scheme for the power system real-time emergency control. Three key technologies are proposed to ensure the effectiveness of the scheme. They are, an instability index, a Critical Machines (CMs) identification algorithm, and a two-layer single machine infinite bus (SMIB) equivalence framework. The concave–convex-area-based instability index shows good accuracy and high reliability, which is used to identify the transient instability of the system. The CMs identification algorithm can track the changes of CMs and form the proper SMIB system at each moment. The new two-layer SMIB equivalence framework, compared with conventional ones, can significantly reduce the communication burden and improve the computation efficiency. The simulations in two test power systems show that the scheme can identify the transient instability accurately and fast to restore the system to stability after the emergency control. Besides, the proposed method is robust to measurement errors, which enhances its practicality. [ABSTRACT FROM AUTHOR]

Subsynchronous oscillation (SSO) is a critical issue for the direct-drive permanent magnet synchronous generator (D-PMSG) based wind farm integrated to a weak onshore AC grid. To analyze the mechanism of the SSO phenomenon of D-PMSG based wind farm, widely used impedance-based stability analysis method is utilized in this paper. First, the impedance model based on the harmonic linearization theory of grid-connected D-PMSG is proposed, and the mechanism of sub/supsynchronous currents coupling is analyzed quantitatively for the first time. Then, based on the impedance model and relative stability criterion, the influence of wind farm operating parameters and grid impedance on stability is discussed. Simulations are carried out to verify the correctness of theoretical analysis. [ABSTRACT FROM AUTHOR]

When rectifier station of line-commutated converter based high-voltage direct transmission current has power fluctuations running at large load, reactive power compensator controlled in groups at rectifying station are switched frequently. That problem potentially has impact on service life of corresponding circuit breaker and threatens the safe operation of the DC system. In this study, in view of the characteristic of close connection between rectifier station and AC system, combined with the existing reactive power control scheme, in order to reduce the number of switching times of reactive power compensator, an optimal reactive power control scheme is proposed when rectifier station running at large load. When the converter station absorbs reactive power, the presented strategy takes converter bus voltage as the main control quantity with the starting point of taking full account of the reactive power support capacity of available generators near the station. When the converter station produces excess reactive power, the strategy takes the reactive power exchange of AC and DC system as the main control quantity, with the starting point of taking full account of reactive power absorption capacity of low-voltage reactor. The simulation results in power system analysis and synthesis program show the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

When an unloaded converter transformer is being energised, large inrush current may flow in the voltage jump side depending upon the residual flux in the core and the closing voltage angle of the power grid due to the hysteresis characteristics of the core, causing false operation of protective relays and bringing many adverse effects to the grid and primary electrical devices. Based on the analysis of the elimination of inrush current using controlled switching, the phase-to-phase electromagnetic coupling relationship which would be influenced by the core structure and winding connection mode was taken into account when considering the controlled switching strategy of three-phase transformer. With the analysis of core residual flux after de-energisation and the dynamic magnetisation of core during the energisation, a controlled switching strategy for inrush current restraining when energising converter transformer is presented in this study. Only the current arc quenching sequence during circuit breaker opening and the voltage extinguishing phase angle are asked for this strategy, and the simulation by electromagnetic transients programme and the experiment results indicate that this strategy could restrain the inrush transient efficiently. [ABSTRACT FROM AUTHOR]

In the modern power system, current source converted high‐voltage direct current (CSC‐HVDC) system is playing an increasingly important role due to the advantages such as flexible control, asynchronous interconnection, and long distance transmission. However, the conventional differential current protection has exposed the shortages in operation speed and fault identification. This study proposes a novel differential current protection scheme, which is composed of the differential current unit and blocking unit. Both of them are designed based on the differences in the newly defined differential current between the internal fault and external fault. A ± 800 kV UHVDC simulation system is established to verify the performance of the proposed protection. Simulation test results show that the proposed protection can accurately distinguish the internal fault from external fault in the whole fault period. The identification performance is not influenced by the fault location or fault resistance. Besides, the requirement of sampling rate is low and the calculation amount can be negligible, providing a favourable condition for the proposed protection scheme to be implemented into the real HVDC control and protection system. [ABSTRACT FROM AUTHOR]

This paper proposes a unified power flow algorithm based on the Newton–Raphson (NR) method to obtain a feasible solution for hybrid AC/DC grids incorporating voltage source converters (VSCs). The power flow model of hybrid AC/DC grids is composed of an AC grid model, a VSC station model, and a DC grid model. Detailed converter losses are involved in VSC station modeling. In the DC grid model, a unified dc control expression is applied to adapt to different control methods. To obtain sparse Jacobian matrix, the mismatch equations and unknown variables are classified into three categories corresponding to AC, VSC, and DC models. Then the proposed algorithm achieved quadratic convergence with the NR method. Once the solution is infeasible (variable out-of-limit) or diverging, the constrained load flow (CLF) method is applied automatically to achieve a feasible solution by revising the references of ac/dc grids. Simulations were carried out for the hybrid AC/DC test system composed of two AC grids and two DC grids. The results under different DC voltage control modes show that the proposed algorithm is able to obtain a feasible solution with high accuracy and convergence speed. [ABSTRACT FROM PUBLISHER]

The UHVDC transmission system has been increasingly used because of the advantages in long distance and large capacity transmission. However, the existing traveling-wave-based protection for UHVDC transmission lines is not sensitive enough to properly detect the internal fault with high fault resistance. A novel traveling-wave-based protection scheme for bipolar UHVDC lines is proposed in this paper. The discriminative characteristic between the internal and external fault, embodied in the backward traveling wave, is extracted to formulate the main protection criterion. The faulty line is identified by the polarity of the voltage fault component. In addition, only the single-pole voltage and current of rectifier side are required for the proposed protection scheme. The simulation and field data tests show that the proposed protection scheme can make a correct identification of the fault section and selection of the faulty line in the $\pm $ 800 kV UHVDC system and $\pm $500 kV HVDC system. Besides, the proposed protection can correctly detect the grounding fault with fault resistance up to 500 $\Omega $. [ABSTRACT FROM PUBLISHER]

In this paper, a simplified method for channel capacity estimation has been derived based on the transmission-line theory under the condition of high-bandwidth utilization. This method decouples the channel capacity into several independent components which may help to investigate the effects of backbone and branch, respectively. Analysis of backbone effects with respect to the available bandwidth reveals the applicable condition for the simplified method. Single branch effects are investigated considering branch length together with the loads. Besides, coupling effects caused by branch interactions are studied in a statistical way. The simulation results show great consistencies by using the proposed method and the conventional one and reveal the way that branches affect the channel capacity in different power networks. [ABSTRACT FROM AUTHOR]

Power transformer rupture and fire resulting from an arcing fault inside the tank usually leads to significant security risks and serious economic loss. In order to reveal the essence of tank deformation or explosion, this paper presents a 3-D numerical computational tool to simulate the structural dynamic behavior due to overpressure inside transformer tank. To illustrate the effectiveness of the proposed method, a 17.3MJ and a 6.3MJ arcing fault were simulated on a real full-scale 360MVA/220kV oil-immersed transformer model, respectively. By employing the finite element method, the transformer internal overpressure distribution, wave propagation and von-Mises stress were solved. The numerical results indicate that the increase of pressure and mechanical stress distribution are non-uniform and the stress tends to concentrate on connecting parts of the tank as the fault time evolves. Given this feature, it becomes possible to reduce the risk of transformer tank rupture through limiting the fault energy and enhancing the mechanical strength of the local stress concentrative areas. The theoretical model and numerical simulation method proposed in this paper can be used as a substitute for risky and costly field tests in fault overpressure analysis and tank mitigation design of transformers. [ABSTRACT FROM AUTHOR]

This paper presents an ultra-high-speed (UHS) pilot protection of transmission lines based on directional comparison of the transient energy (TE). The proposed method can easily determine the fault direction by calculating the TE during a very short period. The obtained fault directions at both ends of the protected line will be compared to discriminate the internal faults. In contrast to the conventional UHS protection using initial traveling waves, this method is able to correctly operate even when the fault inception angle is at zero crossing. In order to correctly indicate the fault direction and improve its sensitivity, the data-processing window has been reasonably chosen to obtain TE by analyzing the polarity variation of the transient power. A large number of various fault scenarios have been simulated on the 750-kV system using PSCAD/EMTDC, and the results show that the proposed method is able to discriminate the internal fault very rapidly and reliably. [ABSTRACT FROM AUTHOR]

The liquid–liquid coexistence curves for the binary solutions of the room temperature ionic liquid (RTIL) 1-methyl-3-octylimidazolium tetrafluoroborate ([C 8 mim][BF 4 ]) in 1-pentanol and 1-hexanol were measured in the critical region. The critical exponent β and the critical amplitude B were deduced and the former was found to be consistent with the 3D-Ising value. The complete scaling theory was applied to describe the asymmetry of the diameters of the coexistence curves. Moreover, the dependences of the critical temperature, the critical mole fraction, the reduced critical temperature and the reduced critical density on the permittivity of alcohol for a series of binary solutions of RTIL in alcohols were discussed. [ABSTRACT FROM AUTHOR]

The rehabilitation of disaster-prone areas can enhance the stability of soil structure and is a common way to increase organic carbon storage. The response of soil carbon sequestration pathways to different recovery modes is not clear, especially in mountain soils. After 11 years of recovery, we evaluated soil organic carbon (SOC) sequestration pathways in plantations (dominated by Olea europaea 'Leccino'), croplands [ Zea mays (L.) ] natural shrublands (Lycium chinense Mill), and natural grasslands [ Setaria viridis (L.) Beauv ]. The physical and chemical properties of the soil and the 13C natural abundance of each aggregate and its density components were studied. The results showed that, during the restoration process, the soil organic carbon content of natural grassland increased the most, while the δ13C value of soil of natural shrubs was the highest. The natural abundance of 13C was used to reveal the pathway of C flow in soil organic matter (SOM), as follows: free light fractions (ρ < 1.6 g cm−3)→mineral fractions (ρ > 2.0 g cm−3)→dense occluded fractions (ρ from 1.6 to 2.0 g cm−3) (in plantation, natural shrubland, and grassland). However, in cropland soil, C flowed as follows: mineral fractions→free light fractions→dense occluded fractions. Specifically, the SOC content decreased with aggregate particle size, and after entering the soil, plant litter was first stored in large aggregates and then decomposed into the free light fraction. The study revealed the mechanism of organic carbon sequestration in the restoration area, emphasizing that artificial restoration treatment can change the carbon conversion pathway, and reduced the sequestration of organic carbon. • The pathways of organic carbon turnover had been clearly determined by 13C natural abundance. • Natural grasslands have the highest soil organic carbon content under the same years of restoration. • δ13C was more enriched in micro-aggregates than in large and small macro-aggregates. • Artificial restoration altered the carbon flow pathway of transformation and reduced the sequestration of organic carbon. [ABSTRACT FROM AUTHOR]

Rates of SN1 hydrolysis reactions for 2-chloro-2-methylbutane in the critical solution of isobutyric acid + water and for 2-bromo-2-methylpropane in the critical solution of triethylamine + water in the one-phase region and at various temperatures have been determined respectively by conductance measurements. It was found that the reaction rates at different temperatures for those two SN1 reactions were well described by the Arrhenius equation in the noncritical region, whereas near the critical points the critical slowing down was clearly detected. These results are inconsistent with a previous report in the literature (J. Phys. Chem. A 2003, 107, 8435 - 8443). Reanalyzing the literature data, we found that if an Arrhenius equation appropriate to either the one-phase region or the two-phase region being examined was used as the background, a critical slowing down rather than a speeding up was detected for the reaction in both the one-phase region and the two-phase region. The experimental data from different sources were fitted with a simplified crossover formalism characterizing the critical effect on the reactions to determine the critical slowing down exponents, which were found to be about 0.04, showing that only a dynamic critical slowing down could be detected for these reaction systems. This phenomenon was attributed to the fact that the SN1 hydrolysis reaction is neither a first-order nor a pseudo-first-order reaction in the reverse direction and the kinetic measurements were carried out in a region quite far from the equilibrium of the reactions.

Mixed surfactant solutions are studied to understand their synergistic effects. Here we report the micellization properties of mixed surfactant solutions of the gemini surfactant N,N'-bis(dimethyldodecyl)-1,2-ethanediammoniumdibromide (12-2-12) with the imidazolium ionic liquid 1-dodecyl-3-methylimidazolium bromide (C12mimBr) investigated by isothermal titration calorimetry (ITC), conductometry, fluorimetry, and dynamic light scattering (DLS). A two-parameter Margules model was successfully used to correlate the cmc values and calculate the compositions and activity coefficients of the two components in the mixed micelle phase for 12-2-12/C12mimBr aqueous solutions with different overall surfactant compositions. The dissociation degree of counterion, the thermodynamic quantities of micellization, and the excess thermodynamic quantities for the mixed micelle were calculated and discussed. The ITC experiment in the low overall surfactant composition region showed a second phase transition. A thermodynamic model was proposed to explore phase behaviors of two different types of micelle and their solution, which was further confirmed by fluorescence and DLS studies.