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The gait phase of dairy cows is an important indicator to reflect the severity of lameness. IThe accuracy of available gait segmentation methods was not enough for lameness detection. In this study, a gait phase recognition method based on Gaussian mixture model (GMM) and hidden Markov model (HMM) was proposed and tested. Firstly, wearable inertial sensors LPMS-B2 were used to collect the acceleration and angular velocity signals of cow hind limbs. In order to remove the noise of the system and restore the real dynamic data, Kalman filter was used for data preprocessing. The first-order difference of the angular velocity of the coronal axis was selected as the eigenvalue. Secondly, to analyze the long-term continuous recorded gait sequences of dairy cows, the processed data was clustered by GMM in the unsupervised way. The clustering results were taken as the input of the HMM, and the gait phase recognition of dairy cows was realized by decoding the observed data. Finally, the cow gait was segmented into 3 phases, including the stationary phase, standing phase and swing phase. At the same time, gait segmentation was achieved according to the standing phase and swing phase. The accuracy, recall rate and F1 of the stationary phase were 89.28%, 90.95% and 90.91%, respectively. The accuracy, recall rate and F1 of the standing phase recognition in continuous gait were 91.55%, 86.71% and 89.06%, respectively. The accuracy, recall rate and F1 of the swing phase recognition in continuous gait were 86.67%, 91.51% and 89.03%, respectively. The accuracy of cow gait segmentation was 91.67%, which was 4.23% and 1.1 % higher than that of the event-based peak detection method and dynamic time warping algorithm, respectively. The experimental results showed that the proposed method could overcome the influence of the cow's walking speed on gait phase recognition results, and recognize the gait phase accurately. This experiment provides a new method for the adaptive recognition of the cow gait phase in unconstrained environments. The degree of lameness of dairy cows can be judged by the gait features.

Permafrost degradation varies spatially; however, the underlying mechanism remains partially unclear. In this study, we predicted permafrost variation under the influence of climate change to investigate the sensitivity of permafrost degradation to geological and climatic conditions. The results revealed that geological strata can strongly impact the permafrost degradation process. Mainly due to the greater thermal conductivity of sandy gravel in the Arctic, the complete thaw of permafrost will be greatly delayed by more than 160 years compared with that on the Qinghai–Tibet Plateau (QTP). Climatic conditions, such as snow depth, can also greatly affect the degradation process of permafrost: The thaw of permafrost will be delayed by more than 140 years when the snow depth decreases from 0.7 to 0.1 m. Peat soil thickness at ground surface can also affect permafrost degradation. The permafrost temperature increases as peat soil thickens when the thickness is less than 1.0 m, whereas there is a critical peat soil thickness (approximately 0.2 and 0.5 m on the QTP and in the Arctic, respectively) under which permafrost will thaw at the fastest rate. The findings highlight the influence of geology and climate over permafrost degradation. [ABSTRACT FROM AUTHOR]

When the mine long-distance belt conveyor adopts multi-point driving mode, the multi-motor synchronous control is adopted between the driving points at a long distance. Moreover, the multi-motor synchronous control strategy based on the traditional relative coupling control can not meet the synchronous requirements in the starting process when the rotational inertia of each motor is different, and the synchronous precision is not high when the steady state is disturbed. In order to solve the above problems, an improved relative coupling control method is proposed. A simple structured and easily implemented torque compensator is added on the basis of the traditional relative coupling control, the deviation between the actual rotating speed of each motor and the average rotating speed of all the motors is sent to a proportional controller for adjustment, and then the output result of the proportional controller is taken as a required torque compensation signal. In order to ensure the safe operation of the multi-motor drive system, the output torque of each motor after compensation is subjected to the same amplitude limiting. The simulation and experimental results show that the improved relative coupling control with torque compensator can realize the speed synchronization of multi-motors in the starting phase under different moments of inertia without affecting the dynamic response speed of the system. The proposed method ensures the system to have good anti-disturbance performance in steady state operation and high synchronization precision after disturbance.

BackgroundThe extraction of uranium (U) and its alternative resources, such as thorium (Th) and plutonium (Pu), from seawater is essential to address the scarcity of terrestrial U resources. The development of a separation material with high adsorption properties is the key to solving this problem.PurposeThis study aims to reveal the adsorption behavior of actinides (U, Th, and Pu) on the surface of a two-dimensional metal material, antimonene.MethodsThe Hubbard U values, Ueff, were determined for the on-site Coulomb interactions of 5f electrons of U and Pu atoms using the linear response method. Furthermore, the adsorption energy, adsorption configuration, electronic structures, charge transfer, and highest occupied molecular orbital wavefunction of a U, Th, or Pu atom adsorbed on the surface of monolayer antimonene were analyzed using the DFT+U approximation. The variation of the adsorption rate with temperature was further calculated by the equilibrium adsorption rate equation.ResultsThe calculated Ueff values of U and Pu atoms are 2.24 eV and 2.84 eV, respectively. The Pu atom is energetically unfavorable to be adsorbed on antimonene (with a negative adsorption energy for each adsorption site), whereas the U and Th atoms exhibit strong chemical adsorption on its surface. Antimonene also offers abundant surficial stable adsorption sites for the U and Th adatoms. The most energetically stable sites for the U and Th adatoms are the B (Bridge)-H (Hollow) site and H (Hollow) site, with adsorption energies of 4.40 eV and 3.62 eV, respectively. The impurity states are generated in the band gap of antimonene upon the adsorption of the U or Th atom, and the strong p-d coupling between the U or Th adatom and antimonene in the impurity states contributes to the strong adsorption of the adatoms. The desorption temperatures of U and Th on the surface of antimonene reach 837 K and 660 K, respectively.ConclusionsThe results indicate that antimonene is an excellent two-dimensional adsorbent material for U and Th and has potential for several applications such as in the extraction of actinides from seawater.

Lameness in dairy cattle could cause significant economic losses to the dairy industry. Detection of lameness in a timely manner is critical to the high-quality development of dairy industry. The traditional method is visual locomotion scoring by dairy farmers, which is low efficiency, high cost and subjective. The demand for automated lameness detection is increasing. The review was conducted to find out the current state and challenges of automatic lameness detection technology development and to learn from the latest findings. The current automatic lameness detection systems were reviewed in this paper mainly rely on five technologies or combinations thereof, including machine vision, pressure distribution measuring system, wearable sensor system, behavior analysis and classification; the principle, function and features of these technologies were analyzed. Machine vision technique is to extract feature variables (e.g. back arch, head bob, abduction, stride length, walking speed, temperature, etc.) from video recordings of cattle movement by image processing. Pressure distribution measuring system contains an array of load cells to sense gait variables, when dairy cattle are walking by. By using accelerometer with high frequency data collection, the gait cycle parameters can be extracted and used for lameness detection. By using wearable devices, the number of lying/standing bouts and their duration, the total time spent lying, standing and ruminating per day can be recorded for individual cattle. The lameness can also be detected by behavior analysis. Currently, most of these studies were in the stage of sensor development or validation of algorithm. A few studies were in the stage of validation of performance and decision support with early warning system. The challenges to apply automatic lameness detection system in dairy farm includes the difficulties of acquiring high quality data of lameness features, lack of techniques to detect early lameness, identification errors caused by individual gait differences among dairy cattle, difficulties to function well in unstructured environment and difficulties to evaluate the benefits. To accelerate the development of automatic lameness detection systems, recommendations are proposed as follows: ①promoting lameness data sharing and data exchange among dairy farms; ②developing individual-based lameness classification model; ③developing multifunctional smart station which can detect lameness, measure body condition score, weighing, etc; ④evaluating the significance of automatic lameness detection to the dairy industry from the perspective of animal welfare, environment and food safety.

A proven and promising method to improve the catalytic performance of single-atom catalysts through the interaction between bimetallic atoms to change the active surface sites or adjust the catalytic sites of reactants is reported. In this work, we used an iron–platinum bimetallic reagent as the metal source to precisely synthesise covalent organic framework-derived diatomic catalysts (FePt-DAC/NC). Benefiting from the coordination between the two metal atoms, the presence of Pt single atoms can successfully regulate Fe–N3 activity. FePt-DAC/NC exhibited a stronger ability to catalyze H2O2 to produce toxic hydroxyl radicals than Fe single-atom catalysts (Fe-SA/NC) to achieve chemodynamic therapy of tumors (the catalytic efficiency improved by 186.4%). At the same time, under the irradiation of an 808 nm laser, FePt-DAC/NC exhibited efficient photothermal conversion efficiency to achieve photothermal therapy of tumors. Both in vitro and in vivo results indicate that FePt-DAC/NC can efficiently suppress tumor cell growth by a synergistic therapeutic effect with photothermally augmented nanocatalytic therapy. This novel bimetallic dual active-site monodisperse catalyst provides an important example for the application of single-atom catalysts in the biomedical field, highlighting its promising clinical potential. [ABSTRACT FROM AUTHOR]

In view of problems of technical difficulties, high cost and high voltage requirements for power electronic components in current high voltage wound-rotor motor using stator-side high voltage inverter for frequency conversion speed regulation, a rotor-side frequency conversion speed regulation technology for high voltage wound-rotor motor was proposed. The technology transfered power transformation from stator side to rotor side taking advantage of low voltage level on rotor side, frequency conversion speed regulation of high voltage wound-rotor motor was realized through general frequency converter. Mathematical model of vector control system for rotor-side frequency conversion was deduced, and adaptive full-order state stator flux linkage observer was designed. Speed identification was realized according to stator flux linkage observation. Matlab simulation and experimental results verify the correctness and feasibility of rotor-side frequency conversion speed regulation technology.