This study evaluated the horizontal variability and diurnal fluctuation of soil respiration to accurately capture changes in carbon flux during agricultural production in Lishu County, Jilin ...Province, China. Corn (Zea mays L.) and soybean (Glycine max L.) were planted with 60-cm row spacing in 2020. The soil respiration rate (SRR) was measured at 2-hour intervals on July 1, August 1, and September 25 using a portable, closed chamber at five positions, P0, P15, P30, P45, and P60, denoting specific distances from the crop rows. The SRR between crop rows was affected both by dates and fields with the coefficient of variation ranging between 7.1 and 37.7%. The SRR at P45 was closest to the mean SRR, with a relative deviation of 0.09-4.85% on July 01 and August 01 in corn and soybean fields. On September 25, the optimal position to measure SRR was between P45 and P60. The sampling dates influenced the optimal time for measuring SRR but were mostly concentrated between 9:00 and 11:00 (24-hour clock) for corn and between 11:00 and 13:00 for soybean. The root biomass of crop rows and diurnal soil temperature were the main factors affecting horizontal variability and diurnal fluctuation of SRR, respectively. We recommend an SRR sampling strategy at P45 between 9:00 and 11:00 for corn and between 11:00 and 13:00 for soybean to decrease the effects of horizontal variability and diurnal fluctuation of SRR.
Audio classification aims to discriminate between different audio signal types, and it has received intensive attention due to its wide applications. In deep learning-based audio classification ...methods, researchers usually transform the raw signal of audios into different feature representations (such as Short Time Fourier Transform and Mel Frequency Cepstral Coefficients) as the inputs of networks. However, selecting the feature representation requires expert knowledge and extensive experimental verification. Besides, using a single type of feature representation may cause suboptimal results as the information implied in different kinds of feature representations may be complementary. Previous works show that ensembling the networks trained on different representations can greatly boost classification performance. However, making inferences using multiple networks is cumbersome and computation expensive. In this paper, we propose a novel end-to-end collaborative training framework for the audio classification task. The framework takes multiple representations as inputs to train the networks jointly with a knowledge distillation method. Consequently, our framework significantly promotes the performance of networks without increasing the computational overhead in the inference stage. Extensive experimental results demonstrate that the proposed approach improves classification performance and achieves competitive results on both acoustic scene classification tasks and general audio tagging tasks.
Aiming at the complex fault signal components and difficulty in identifying the fault features of a hoist spindle device, this study proposes a method based on a filtering algorithm, Hilbert-Huang ...transform (HHT), energy entropy, and support vector machines (SVM). The filtering method is applied to the vibration signal under different fault conditions. Then, the Hilbert-Huang transform is applied to the noise-reduced signal. The empirical mode decomposition (EMD) method decomposes the noise-reduced vibration signal into a set of intrinsic mode functions (IMF). Then, the Hilbert transform (HT) calculates the envelope spectrum of the first few IMFs. Afterward, it evaluates and extracts the fault characteristic frequencies. Finally, the identification of different fault defect types is determined by combining the intrinsic modal energy entropy and SVM. The experimental results show that the method can accurately identify the faults in the rotor bearing system and is an effective fault signal processing method.
Wire rope breakage, as damage easily produced during the service period of wire rope, is an important factor affecting the safe operation of elevators. Especially in the high-speed elevator operation ...process, the problem of magnetization unsaturation caused by speed effects can easily lead to deformation of the magnetic flux leakage detection signal, thereby affecting the accuracy and reliability of wire breakage quantitative detection. Therefore, this article focuses on the problem that existing wire rope detection methods cannot perform non-destructive testing on high-speed elevator wire ropes and conducts design and experimental research on a high-speed running wire rope breakage detection device based on the principle of multi-stage excitation. The main research content includes simulation research on the multistage excitation, structural design, and simulation optimization of open-close copper sheet magnetizers and the building of a detection device for wire rope breakage detection experimental research. The simulation and experimental results show that the multistage magnetization method can effectively solve the problem of magnetization unsaturation caused by the velocity effect. The multistage excitation device has a good wire breakage recognition effect for speeds less than or equal to 3 m/s. It can detect magnetic leakage signals with a minimum of four broken wires and has good detection accuracy. It is a new and effective wire breakage detection device for high-speed elevator wire rope, providing important technical support for the safe and reliable operation of high-speed elevators.
Aiming at predicting what happens in reality inside mills, the contact parameters of iron ore particles for discrete element method (DEM) simulations should be determined accurately. To allow the ...irregular shape to be accurately determined, the sphere clump method was employed in modelling the particle shape. The inter-particle contact parameters were systematically altered whilst the contact parameters between the particle and wall were arbitrarily assumed, in order to purely assess its impact on the angle of repose for the mono-sized iron ore particles. Results show that varying the restitution coefficient over the range considered does not lead to any obvious difference in the angle of repose, but the angle of repose has strong sensitivity to the rolling/static friction coefficient. The impacts of the rolling/static friction coefficient on the angle of repose are interrelated, and increasing the inter-particle rolling/static friction coefficient can evidently increase the angle of repose. However, the impact of the static friction coefficient is more profound than that of the rolling friction coefficient. Finally, a predictive equation is established and a very close agreement between the predicted and simulated angle of repose is attained. This predictive equation can enormously shorten the inter-particle contact parameters calibration time that can help in the implementation of DEM simulations.
A reactive molecular dynamics simulation employing the multistate empirical valence bond (MS-EVB) methodology is reported for the hydration structure of an excess proton in a (6,6) carbon nanotube as ...well as for the mechanism of proton transport (PT) within the nanoconfined environment. The proton is found to be hydrated in a distorted Zundel cation (H5O2 +) form within the one-dimensional, confined water chain. Proton transfer events occur via a “Zundel−Zundel” mechanism through a transient H7O3 + intermediate that differs significantly from the “Eigen−Zundel−Eigen” mechanism found in bulk water.
Infrastructure as a service (IaaS) allows users to rent resources from the Cloud to meet their various computing requirements. The pay-as-you-use model, however, poses a nontrivial technical ...challenge to the IaaS cloud service providers: how to fast provision a large number of virtual machines (VMs) to meet users' dynamic computing requests? We address this challenge with VMThunder, a new VM provisioning tool, which downloads data blockson demandduring the VM booting process and speeds up VM image streaming by strategically integrating peer-to-peer (P2P) streaming techniques with enhanced optimization schemes such as transfer on demand, cache on read, snapshot on local, and relay on cache. In particular, VMThunder stores the original images in a share storage and in the meantime it adopts a tree-based P2P streaming scheme so that common image blocks are cached and reused across the nodes in the cluster. We implement VMThunder in CentOS Linux and thoroughly test its performance. Comprehensive experimental results show that VMThunder outperforms the state-of-the-art VM provisioning methods, with respect to scalability, latency, and VM runtime I/O performance.
A method to prepare magnetic nanoparticles with a covalently bonded polystyrene shell by surface initiated atom transfer radical polymerization (ATRP) was reported. First, the initiator for ATRP was ...covalently bonded onto the surface of magnetic nanoparticles through our novel method, which was the combination of ligand exchange reaction and condensation of triethoxysilane having an ATRP initiating site, 2-bromo-2-methyl-
N-(3-(triethoxysilyl)propyl) propanamide. Then the surface initiated ATRP of styrene mediated by a copper complex was carried out and exhibited the characteristics of a controlled/“living” polymerization. The as-synthesized nanoparticles were coated with well-defined PS of a target molecular weight up to 45
K. These hybrid nanoparticles had an exceptionally good dispersibility in organic solvents and were subjected to detailed characterization using DLS, GPC, FTIR, XPS, UV–vis, TEM and TGA.
Wire rope has different degrees of surface wear under long-distance transmission conditions, which leads to performance degradation and greatly threatens its safety and reliability in service. In ...this paper, friction and wear tests between the transmission wire rope and sheave under different sliding velocities (from 0.8 m/s to 1.6 m/s) were carried out using a homemade test rig. The material of the steel wires was low carbon steel, and pulley material was ASTM A36 steel plate. The sliding friction coefficient (COF), friction temperature rise, wear characteristic parameters and wear mechanisms of the wire rope were analyzed. Additionally, the effect of different wear on the fracture behavior of the wire rope was investigated by a breaking tensile test. The results show that the average COF in the relatively stable stage decreased from approximately 0.58 to 0.51 with the increase of sliding velocity. The temperature rise of the wire rope increased rapidly with an increase of sliding velocity, from approximately 52.7 °C to 116.2 °C. The maximum wear width was the smallest when the sliding velocity was 1.2 m/s (approximately 1.5 mm). The surface wear was characterized by spalling, furrowing and plastic deformation, which are strongly affected by the sliding velocity. The wear mechanisms of the wire rope were mainly adhesive wear and abrasive wear. Surface wear changes the fracture morphology of the wire rope and accelerates its fracture speed.
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