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PurposeThis paper aims to present a dynamic reliability model of scraper chains based on the fretting wear process and propose a reasonable structural optimization method.Design/methodology/approachFirst, the dynamic tension of the scraper chain is modeled by considering the polygon effect of the scraper conveyor. Then, the numerical wear model of the scraper chain is established based on the tangential and radial fretting wear modes. The scraper chain wear process is introduced based on the diameter wear rate. Furthermore, the time-dependent reliability of scraper chains based on the fretting wear process is addressed by the third-moment saddlepoint approximation (TMSA) method. Finally, the scraper chain is optimized based on the reliability optimization design theory.FindingsThere is a correlation between the wear and the dynamic tension of the scraper conveyor. The unit sliding distance of fretting wear is affected by the dynamic tension of the scraper conveyor. The reliability estimation of the scraper chain with incomplete probability information is achieved by using the TMSA for the method needs only the first three statistical moments of the state variable. From the perspective of the chain drive system, the reliability-based optimal design of the scraper chain can effectively extend its service life and reduce its linear density.Originality/valueThe innovation of the work is that the physical model of the scraper chain wear is established based on the dynamic analysis of the scraper conveyor. And based on the physical model of wear, the time-dependent reliability and optimal design of scraper chains are carried out.

A winding hoist is a key equipment for ultra-deep mine hoisting. The inter-circle transition in the winding process of the hoisting wire rope causes vibration, impact, extrusion, wear, and other negative phenomena, which seriously affect the service life of the rope. In order to explore the effect of inter-circle transition on the friction and wear performance of wire ropes, the present study adopts the principle of equal ratio scaling to build a test rig for an inter-circle transition of wire ropes, and the evolutions of coefficient of friction and maximum friction temperature with increasing the tensioning force and rope speed under dry friction were investigated by the test rig, and the major wear mechanisms under different working conditions were investigated in combination with the wear morphologies. The results show that the coefficient of friction decreases first and then increases with an increase in the tensioning force, and decreases linearly with increasing the rope speed. The evolution of maximum temperature over time under different tensioning forces and rope speeds are all mainly divided into three stages: The rapid growth phase, the slow growth phase, and the stable phase. The influence of the rope speed on the temperature of the wire rope is greater than that of the tensioning force. Moreover, in the process of inter-circle transition, the major wear mechanism is abrasive wear. Furthermore, larger tensioning force and rope speed may cause the steel wires on the contact surface of the wire rope to break.

Satellite-based quantum key distribution is the key to develop the intercontinental quantum network. After the demonstrations by Chinese satellite Micius, the prospect of global-scale quantum internet is no more out of reach. However, the research efforts on modeling of constellation of quantum satellite is still insufficient so far. In this paper, we study the algorithm to select quantum key distribution access, the key size re-distribution optimization model and corresponding key size consumption along inter-satellite links. Besides, we present the brief discussion of how the constellation configuration interferes quantum key distribution performance.

Friction and wear are the primary factors for the failure of liners, which affects the lifting capacity and milling cost in ball mills. However, there are no effective methods to measure and evalua...

The wear characteristics and related mechanisms of the ring chain of a scraper chain were investigated. Multiple sets of wear tests were performed to simulate the working environment of a heavy-loa...

Hoisting equipment is core to many industrial systems and, therefore, their state of health significantly affects production lines and personnel safety; this is especially important in environments such as coal mines. The health of the hoisting system can be estimated by deploying energy harvesting wireless sensor nodes that monitor the drum surface stress. In this network of sensor devices, it is very costly to send highly sampled data as it causes radio congestion and consumes energy. However, from our experience of sensing hoist systems, we note that the data observed at the upper surface of the hoist are significantly more indicative of the state of health of the whole system, compared with data sensed at the lower surface. Therefore, we need to take advantage of this to optimize the communications of sensor nodes. However, scarce energy can be collected for these devices from the hoist itself, along with the prioritized Quality of Service (QoS) requirements (throughput, delay) of monitoring signals, raises important challenges for energy management. In this article, we use Lyapunov optimization techniques and propose an energy-neutral and QoS-aware protocol (EQP), including duty cycling and network scheduling to solve it. Extensive simulations show that the EQP helps sensor nodes realize consecutive monitoring, and achieve more than 38% utility gain compared with existing strategies.

Moment-based methods use only statistical moments of random variables for reliability analysis. The cumulative distribution function (CDF) or probability density function (PDF) of a performance function can be constructed from the perspective of the first few statistical moments, and the failure probability can be evaluated accordingly. However, existing moment-based methods may lead to large errors or instability. As such, the present paper focuses on the high order moment method for higher accuracy of reliability estimation by combining the common saddlepoint approximation technique, and an improved high order moment-based saddlepoint approximation (SPA) method for reliability analysis is presented. The approximated cumulant generating function (CGF) and the CDF of the performance function in terms of its first four statistical-moments are constructed. The developed method can be used for reliability evaluation of uncertain structures follow any types of distribution. Several numerical examples are given to demonstrate the efficacy and accuracy of the proposed method. Comparisons of the new method and several existing high order moment methods are also made on the reliability assessment.

A time-varying sensor delay is inevitable in a mining cable elevator operating at a maximum distance which is more than 2000-m underground, when the sensor signals are transmitted from a cage at the bottom of the cable to a control center on the ground through a set of wireless devices, including emitters and receivers. This sensor delay may degrade the estimation precision of the state observer or even destroy the stability of the closed-loop system. In this brief, we design an observer which can compensate the sensor delay with a time-varying and arbitrary length to estimate the vibration states of the mining cable elevator, including the time-varying-length mining cable and the cage. The vibration dynamics of the mining cable elevator is described by a wave partial differential equation (PDE)-ordinary differential equation (ODE) coupled system on a time-varying domain, and the sensor delay dynamics is represented by a transport PDE on a time-varying domain. A full-order infinite dimensional observer is constructed to estimate the states of such a wave PDE-ODE-transport PDE coupled system where PDEs are on time-varying domains, only using available boundary values without measurements at the connection points of the PDEs and ODE. The exponential stability of the observer error system is proved via Lyapunov analysis. The effectiveness of the proposed observer is verified via numerical simulation.

Fe-Ni matrix composites with varied amounts of graphite (Gr) were fabricated by spark plasma sintering system (SPS), and the microstructure and properties of composites were investigated in details. The results implied that Fe-Ni matrix composites were mainly composed of Fe, NiWCr, FeNi, FeCr, Fe3C, Fe3W3C, (Cr, Fe)7C3, cored-eutectic structure (pearlite/Fe3C) and Gr. The variation of the average microhardness of Fe-Ni matrix composites depended on the content of Gr. It initially increased, followed by a decreasing trend with the increasing Gr content. When the Gr addition was 3 wt.%, the average microhardness reached a maximum value of about 355.3HV0.5, which was about twice higher than that of 16Mn steel. Besides, the lowest wear rate of Fe-Ni matrix composites was also achieved with increasing Gr content to 3 wt.% under identical conditions due to the high hardness and the formation of a continuously low shear strength composite layer for the worn surface. Keywords: The middle chute, The scraper conveyor, Fe-Ni matrix composites

In this paper, a modified double-rope winding hoisting system (MDWHS) is proposed for ultra-deep mines. Nevertheless, the MDWHS has wire rope tension imbalance issues due to lift inconsistency of two wire ropes. A combined control algorithm is designed for wire rope tension active control considering the nonlinear uncertainties subjected to the MDWHS, where a low gain state observer (LGSO) and a robust nonlinear adaptive controller are employed via backstepping theory. Firstly, to investigate the wire rope tension active control method, the dynamics model of the MDWHS is established. Then, the LGSO is employed to estimate unmeasured system state variables and to optimize perturbed system state variables. Finally, a robust nonlinear control method is employed to acquire prospective control input. The combined control algorithm can ensure the desired transient and final tracking accuracy, which is essential for tracking control of wire rope tension active adjustment. The stability of the overall closed-loop system with the presented control algorithm can be verified referring to the Lyapunov theory. Experimental results conducted on the established double-rope winding hoisting simulation experimental system demonstrate that the proposed active control method exhibit more advantageous performance on wire rope tension balance control compared with the conventional Proportion Integration (PI) and adaptive backstepping controller (ABC).

This article focuses on a novel robust adaptive sliding mode control strategy of an electro-hydraulic force loading system with consideration of external disturbances and parameter uncertainties. To obtain the proposed controller, the nonlinear dynamic model of the electro-hydraulic force loading system is firstly provided, where external disturbances and system’s uncertain parameters are merged. Then, with consideration of external disturbances and parameter uncertainties, a robust adaptive sliding mode controller for the force control system is proposed and designed according to Lyapunov stability theory. The proposed controller has the merit of suppressing chattering phenomenon in traditional adaptive backstepping controllers when designing sign functions. In order to verify effectiveness and feasibility of the proposed controller, experimental studies are implemented on an electro-hydraulic force loading system by xPC rapid prototyping technology. Experimental results demonstrate that the proposed controller exhibits more excellent performance on force tracking control in comparison of a traditional proportional-integral controller and an adaptive backstepping controller.

Modelling and control vibration is studied for the flexible guided lifting system in the presence of output constraints, input hysteresis, guided rope fault, etc. Flexible guided lifting system, subjected to external disturbances from the boundary disturbance or fluid interaction, is an inherent distributed parameter system with time-varying length and infinite dimensions. According to extended Hamilton’s principle, the governing equation in the form of hybrid partial differential equations and ordinary differential equations is derived to reflect the dynamic response of such multiple ropes under the boundary disturbances and multiple constraints. Adaptive neural network control combining with backstepping technique is subsequently designed to suppress undesirable vibration and stabilise the system, where the neural network is provided as a feedforward compensator for the unknown hysteresis nonlinearities in the control input. Asymptotic stability and uniform boundedness of the system are guaranteed through the Lyapunov theorem, which indicates that all states are uniformly convergent by LaSalle’s invariance principle. The original governing equation is solved numerically by using the finite difference method, where simulation results are illustrated to validate the efficiency of the hybrid partial differential equation and ordinary differential equation model and the adaptive stabilisation design.

In the ball mill, the motion of charge is a complex system, especially under wet grinding. It is difficult to measure the charge physical quantities and hard to validate the correctness of charge motion simulation. To this end, an instrumented ball which is capable of measuring the charge physical quantities was designed. The laboratory ball mill was lined with 12 pieces of trapezium lifters and filled with Jb = 25% grinding balls. An iron ore was used to prepare the slurry at 50% solid concentration by mass. A series of tests were carried out to investigate the charge dynamics at different mill speeds and slurry filling. The average rotational kinetic energy, average applied force and mill power were measured and analyzed. The results showed that the average rotational kinetic energy increases with mill speed, whereas the average applied force first increases and then decreases. The average rotational kinetic energy and applied force first increases and then decreases by the increase in slurry filling. Furthermore, there exists a slurry filling U = U* that the mill power has a maximum value.

An innovative wind-induced energy harvester utilizing a piezoelectric bimorph with a pulling strip was designed based on Karman vortex street theory to collect wind energy from a rotating machinery for powering some devices. A mathematical model was initially established for the model force analysis, and the voltage generated by the piezoelectric bimorph were calculated. The stress distribution on the piezoelectric bimorph was also examined to prevent the piezoelectric material from cracking. A series of experiments were conducted according to the results of the numerical analysis. Both the numerical analysis and the experiments demonstrate that: first, rotation speed is the most important factor that affects the power generation capacity of the piezoelectric bimorph, and with a suitable installing angle, an output power of 1 mW can be easily acquired when the rotation speed exceeds 140 r/min; and, second, choosing an appropriate installing angle can increase the power generation capacity more effectively than rectifying the diameter of the cylindrical obstacle.

Estimating system reliability has been recognized as a critical step in reliability-based design optimization for structural systems. The estimation of system reliability entails multi-dime...

The development of simple, flexible, cost-effective and sensitive electrochemical biosensing strategies is highly desirable to advance their applications in disease diagnostics and clinical biomedicine. Herein, we fabricated a new enzyme-based electrochemical aptasensor with the use of adenosine triphosphate (ATP) and thrombin as model targets on the basis of a responsive surface bioaffinity binding strategy. It took full advantage of an immobilized complex duplex probe (hybrids of a hairpin-like aptamer probe with a digoxigenin (Dig)-labeled immobilization strand) to effectively inhibit the approach of the bulky horseradish peroxidase linked-anti-Dig antibody (anti-Dig-HRP) to the Dig on the electrode due to the steric effect. The target recognition dissociated the aptamer strand from the duplex probe and exposed the Dig for its effective binding with anti-Dig-HRP. The successive electrocatalysis offered a significantly amplified electrochemical signal correlated with the target recognition event. Sensitive detection toward ATP and thrombin was achieved with detection limits of 0.87 nM and 6.3 pM, respectively. The proposed strategy is simple and sensitive without any complex operations that hinder many amplified aptasensors. Also, the target recognition and signal reporting units are relatively isolated, making the biosensor fabrication more flexible. It thus provided a new and versatile pathway for sensitive biosensor fabrication.

Surface wear is the main reason for the breaking failure of the wire rope in service, particularly in the multi-layer winding hoist system of a coal mine. Understanding the effect of wear scars on the failure and mechanical properties of the rope is the effective way to ensure the safety of multi-layer winding hoist. In this paper, the breaking failure characteristics of hoist ropes with different wear scars were investigated by the breaking tensile test. The temperature rise in the wear scar regions was obtained and analyzed. Additionally, the finite element method was used to simulate the mechanical properties of the wear-out strands subjected to tensile load. Results show that the severe plastic deformation and obvious temperature rise occur in the wear scar region. The temperature rise curves during the breaking tensile test can reflect the number and the order of the fractured strands. The wear-out outer wires fracture earlier than the internal wires, and the wires with irregular wear scar always fracture along the sliding wear direction at the location with the maximum wear depth. Additionally, the wear scar caused by left cross contact will cause stress concentration and uneven distribution, and the wear depth makes it more obvious.

In practical applications, the signal measured from a complex mechanical system is usually disturbed by various noises due to the compounded effect of interferences of other machine elements and background noises, especially under varying speed conditions. Resonance-based approaches have been proven to be effective methods to address this problem. However, even if the optimal resonance band is accurately determined, the in-band noise with frequency content in the range covered by the band-pass filter is not eliminated. To avoid missed diagnosis and misdiagnosis of faults in bearings, an iterated SVD (ISVD)-based in-band noise reduction method combined with envelope order spectrum analysis is proposed in this paper. First, the optimal frequency band of a vibrational signal is determined with the help of an enhanced wavelet packet transform kurtogram, in which the kurtosis of each node is calculated based on the envelope spectrum of a signal be reconstructed using the wavelet packet coefficients. The node with the maximum kurtosis value is used to reconstruct the signal. Second, the envelope of a reconstructed signal is calculated by Hilbert transform and the ISVD method is applied to it to reduce the in-band noise. To avoid the destruction of useful information caused by excessive iteration, a threshold is set to determine the number of iterations. After iterative processing, a de-noised signal is reconstructed based on the relationship between the singular value and a frequency component. Finally, the reconstructed signal is resampled and transformed into the fault characteristic order domain where the bearing fault type can be identified from the envelope order spectra. The simulations and experiments were used to validate the efficacy of the proposed method. Compared with the spectral subtraction method, the ISVD method can suppress in-band noise efficiently and beneficial to extract the fault characteristic order under variable speed conditions.

Double-rope winding mine hoist (DRWMH) is a vital coal mining equipment whose performance directly impacts the safe and efficient exploitation of the deep earth resources. Unfortunately, the actuator faults and disturbances can greatly affect the effect of the DRWMH. This paper deals with the problem of tension coordination control against actuator faults and disturbances for a DRWMH driven by multiple permanent magnet synchronous motors (PMSMs) using the neural-based adaptive method and iterative learning scheme. To improve the control performance and to maintain the stability of the DRWMH under faulty conditions, in this approach, a novel neural-based adaptive control strategy is developed to implement the input control assignment of the actuators. An iterative learning controller is used to achieve the compensation of the faults and uncertainties. The stability of both control subsystems has been proven. A series of experimental results are illustrated to demonstrate the validity of the proposed fault tolerant control for the DRWMH, which also reveal that a superior control effect is achieved in contrast with traditional controllers. Furthermore, the strategy proposed in this paper can be applied to other mechanical systems driven by multiple PMSMs that require high safety.

Overwinding protection devices are used to brake hoisting containers before these containers reach a limited height, thereby preventing the hoisting containers from impacting the hoisting system. However, in ultra-deep shafts (depth > 1000 m), traditional overwinding protection methods fail to protect the hoisting system, because this type of hoisting system has a greater mass, kinetic energy, and inertia than the traditional hoisting system, and also the environment of ultra-deep shafts is more complex. This paper presents a novel overwinding protection method that applies a linear permanent magnet eddy current brake (LPMECB) to the hoisting system in ultra-deep shafts. This paper also finds the optimum setting parameter of permanent magnets (PMs). First, an analytical model of the LPMECB is built, and the time-domain signals of the braking force are processed via fast Fourier transform, confirming the mechanism of the optimum setting parameter. Subsequently, the simulations are conducted by establishing a finite-element model of the LPMECB; the simulations prove the existence of the optimum setting parameter of PMs and demonstrate the influence of the air gap, velocity, and conductivity on this parameter. Finally, the experimental studies are carried out on a test bench of the LPMECB to validate the analytical model and the simulation results. The results show the existence of the optimum setting parameter of PMs and prove that the air gap has an effect on this parameter.

Aiming at the task planning and scheduling problem of space object detection LEO constellation (SODLC) for detecting space objects in deep space background, a method of SODLC task satellite selection based on observation window projection analysis is proposed. This method projects the spatial relative relationships of the SODLC observation blind zone, observation range, and the initial spatial position of the objects onto the surface of the earth for detectable analysis of satellites and targets and binds the dynamic observation conditions to the satellite trajectory after projection calculation of the visible relationship between target changes. On this basis, combined with the features of SODLC with high orbital symmetry, the task satellite selection is divided into two steps: orbit plane selection and task satellite selection. The orbit planes are selected based on the longitude range of the ascending node with the geographic location of the targets, and the task satellites are selected according to the relative motion relationship between the satellites and the targets together with the constraints of observable conditions. The selection method simplifies the calculation process of scheduling and selecting task satellites. Simulation analysis prove the method has better task satellite selection efficiency. The method has high practical value for task planning and scheduling for event-driven SODLC.

When the double-rope winding hoisting system (DWHS) is in operation, tensions of two wire ropes of the DWHS will not be symmetrical because of some factors such as different manufacturing deviation between the twin winding drum and two wire ropes, different winding groove depths, the winding asynchronism of two wire ropes, and elastic modulus difference of two wire ropes and so on. Therefore, an electro-hydraulic servo system (EHSS) is employed to actively control two wire ropes tensions to guarantee operation security of the DWHS. Dynamic models of the hoisting system and the EHSS are introduced, of which dynamic model of the DWHS is expressed with state representation. The flatness-based controller (FBC) is designed for the hoisting system. A disturbance observer is utilized to deal with the external disturbance and unmodeled characteristics of the EHSS. Hence, a disturbance observer based integral backstepping controller (DO-BIBC) is designed for the EHSS. The stability of the overall control system is proved by de-fining an overall Lyapunov function. To investigate the property of the proposed controller, an experimental setup of the DWHS is established. As well, comparative experimental results indicate that the proposed controller exhibits a better performance on leveling control of the conveyance and tension coordination control on the two wire ropes than a conventional PI controller.

The enhanced X-ray Timing and Polarimetry (eXTP) is an international cooperation flagship mission, equipped with four kinds of instruments, including 9 SFA (Spectroscopic Focusing Array) telescopes, 4 PFA (Polarimetry Focusing Array) telescopes, 6 WFM (Wide Field Monitor) cameras, and 40 LAD (Large Area Detector) modules. These payloads overall require about 11.5m2 for mounting on the same side of the satellite, with high alignment requirement between lines of sight of each instrument to guarantee the effective area and response performance of scientific payload, which is the most important driver for the satellite mechanical design. At the same time, the mirror assemblies and cameras of SFA and PFA telescopes are installed separately on the satellite, relying on the satellite structure to ensure the relative position accuracy. There are also factors such as payload field-of-view, sun shield, antenna accommodation, mechanical property to be taken care of in the satellite configuration design. According to the characteristics of payloads, an integrated configuration and structure design of eXTP satellite is proposed, with a high-rigid optical module providing large area for payload optics accommodation, a central cylinder as the primary force-taking structure of the satellite, a service module for platform equipment accommodation, and a detector module equipped with cameras of SFA and PFA. This paper introduces the mechanical design and analysis of eXTP satellite. The feasibility and performance of configuration and structure design are verified by simulation analysis.

Neural network is a key part of image recognition and classification. It is also one of the hotspots in recent years. Deep belief network, as a method of machine learning, has strong generalization and gets more and more attention from experts and scholars at home and abroad. Aiming at these two research hotspots, a method of road marking image recognition based on deep belief network (DBN) is proposed in this paper. Four experiments below show that it has high accuracy and practicability, which provides an important theoretical basis for highway’s construction and maintenance in special areas.

Fretting wear among steel wires is one of the important factors for the wire rope fracture. The influence of the wire diameter and crossing angle on the fretting fatigue behaviors of steel wires under tensile-torsional coupling force was explored in the present study. The test principles and analysis methods were introduced. Result shows that the variation laws of the coefficient of friction (CoF) between steel wires with increasing crossing angle under different wire diameter contacts are the same. For the same crossing angle, the CoF under different test conditions increases in the following sequence: both with the diameter of 0.8 mm

Event: Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray, 114442E (13 December 2020)., The enhanced X-ray Timing and Polarimetry Observatory (eXTP) is a flagship international collaboration mission led by Chinese Academy of Sciences, with a large contribution from more than 20 European institutes. eXTP mission is designed to study the equation of state of ultra-dense matter under extreme conditions of strong density, gravity and magnetic field. The satellite carries four main instruments, including the Spectroscopy Focusing Array (SFA), the Large Area Detector (LAD), the Polarimetry Focusing array (PFA) and the Wide Field Monitor (WFM), enabling simultaneous spectral-timing-polarimetry studies of celestial sources in the energy range from 0.5-30 keV. The satellite will fly at a near-zero-inclination Low Earth Orbit, and is featured with long-time steady high-precision coaxial pointing, near realtime burst alert distribution, and follow-up maneuver capabilities. This paper describes the primary mission requirements and constraints, and presents an overall mission analysis including orbit analysis, pointing strategy, and board-ground communications, etc. The preliminary design of eXTP satellite is also introduced, including satellite overall configuration, observation modes, avionics architecture and development plan., The mission is led by China, currently supported by Chinese Academy of Sciences and executed under the management of the National Space Science Center of CAS. The project has officially kicked off Phase B in November 2019. After Phase C1, official mission adoption is expected. With Phase C2 and Phase D planned in 2023-2027, the eXTP satellite is targeted to be launched in 2027.

Corrosion, friction and wear of wire ropes always exist in multi-layer winding systems. They lead to the lubrication failure and service performance degradation of wire rope. To reveal the tribological properties of wire rope in service, the coefficient of friction (COF), friction temperature rise and surface wear characteristics of wire rope with different lubrication and corrosion conditions were investigated. The experimental results show that friction parameters of the lubricated wire ropes are relatively small, which are obviously affected by the sliding stroke and velocity. The COF fluctuates between approximately 0.15 and 0.28, and the friction temperature rise is reduced to below 7 °C. Additionally, the corrosion solutions degenerate the anti-friction and anti-wear properties of the lubricating grease and oil. The COF and friction temperature rise of the oil lubricated wire rope increase greatly when the rope sample is corroded by sea-water and dilute sulfuric acid solution. The sliding wear mechanism and lubrication stage of the lubricated wire ropes is adhesive wear and boundary lubrication, respectively. Furthermore, dilute sulfuric acid solution is the most harmful to the friction-reduction and wear-resistance of the lubricating grease and oil used for wire rope, followed by sea-water solution and fresh water solution.

Electro-hydraulic shake table (EHST), also known as earthquake simulator, is of considerable significance in civil engineering for evaluating structures or infrastructures subjected to earthquake ground motions. However, reproduction of prescribed accelerations at table for EHST systems remains to be imperfect as the whole systems are confronted with hydraulic nonlinearity, varying dynamics, unexpected disturbance, etc. For enhancing the acceleration tracking performance of EHST systems, an acceleration waveform reproduction strategy using offline designed parametric feedforward compensator (PFC) and online functional link adaptive controller (FLAC) is proposed in this paper. The PFC controller is established on the basis of classical three variable controller (TVC) as an inner compensation loop, in which multi-innovation forgetting gradient (MIFG) algorithm together with zero magnitude error tracking (ZMET) technique are utilized during the design process. The FLAC controller is combined to the PFC controller as an outer loop for further acceleration enhancement purpose, and the controller’s nonlinear mapping ability is achieved with trigonometric expansion implementation. Following theoretical analysis of the proposed controller, comparative experiments are performed on an established unidirectional EHST test bench with both random and real-time recorded earthquake input waveforms. The experimental results validate the feasibility and superiority of the proposed acceleration reproduction strategy.

Protein kinase activity analysis is essential and important for elucidation of many fundamental biological processes, disease diagnosis, and drug discovery. Herein, a novel electrochemical biosensing method for protein kinase (PKA) activity was demonstrated by the use of a reduced graphene oxide-zirconium dioxide–thionine (rGO-ZrO2–Thi) nanocomposite, which interestingly served as an integral phosphopeptide-recognizing, signal amplifying and reporting platform. The ZrO2 nanoparticle-decorated reduced graphene oxide (rGO-ZrO2) was first prepared by a hydrothermal reaction route, and then the thionine was conjugated onto the rGO surface via π–π stacking as an excellent electrochemical probe. The prepared rGO-ZrO2–Thi nanocomposites were well-characterized by various techniques. With the full advantage of specific recognition of ZrO2 nanoparticles for the phosphate group, signal amplification, and transduction of abundant thionines onto the rGO surface, and excellent conductivity of rGO, the rGO-ZrO2–Thi nan...

Investigation of the free vibration of stepped shafts with and without transition area is presented in this paper. The refined one-dimensional beam theories are chosen to be used based on the Carrera Unified Formulation (CUF) in the present work. According to CUF, Taylor-type expansion is employed to describe the displacement field over cross section of shafts. With the implementation of Hamilton’s principle, the governing differential equations and the related mass matrix, the stiffness matrix and the load vector are obtained. To obtain the numerical solutions, the finite method is adopted in this paper. The accuracy and reliability of the present model are demonstrated by comparing with classical beam model (Timoshenko beam model) and a solid model generated in the commercial software ANSYS. Meanwhile, the influences of step ratio, step location, boundary conditions and the slope of generatrix attached to the transition area on vibration characteristics are studied.

Feature extraction is one of the most difficult aspects of mechanical fault diagnosis, and it is directly related to the accuracy of bearing fault diagnosis. In this study, improved permutation entropy (IPE) is defined as the feature for bearing fault diagnosis. In this method, ensemble empirical mode decomposition (EEMD), a self-adaptive time-frequency analysis method, is used to process the vibration signals, and a set of intrinsic mode functions (IMFs) can thus be obtained. A feature extraction strategy based on statistical analysis is then presented for IPE, where the so-called optimal number of permutation entropy (PE) values used for an IPE is adaptively selected. The obtained IPE-based samples are then input to a support vector machine (SVM) model. Subsequently, a trained SVM can be constructed as the classifier for bearing fault diagnosis. Finally, experimental vibration signals are applied to validate the effectiveness of the proposed method, and the results show that the proposed method can effectively and accurately diagnose bearing faults, such as inner race faults, outer race faults, and ball faults.

As a key component of a mine hoist system, the main-shaft device bears most of the bending moment and torque. Thus, it is important to quantify the performance of the main-shaft device and ensure the reliability of the device. The paper aims to investigate the impact of uncertain structural parameters on the reliability of the main-shaft device. The probabilistic optimal design is performed based on the parameter sensitivity results. First, the design of experiments is adopted to realize the stochastic response analysis of the main-shaft device. Second, the moment-based saddlepoint approximation method is used to evaluate the strength reliability of the device considering uncertain parameters. Next, the reliability-based sensitivity is derived to investigate the parametric significance of random input variables. Finally, the probabilistic optimal design involving the reliability sensitivity is conducted. The results of the sensitivity indicate that the torque and the contact length of left bearing have relatively greater impact on the structural reliability than other variables of the main-shaft device.

To deal with the dynamic and imbalanced traffic requirements in Low Earth Orbit satellite networks, several distributed load balancing routing schemes have been proposed. However, because of the lack of global view, these schemes may lead to cascading congestion in regions with high volume of traffic. To solve this problem, a Hybrid-Traffic-Detour based Load Balancing Routing (HLBR) scheme is proposed, where a Long-Distance Traffic Detour (LTD) method is devised and coordinates with distributed traffic detour method to perform self-adaptive load balancing. The forwarding path of LTD is acquired by the Circuitous Multipath Calculation (CMC) based on prior geographical information, and activated by the LTD-Shift-Trigger (LST) through real-time congestion perception. Simulation results show that the HLBR can mitigate cascading congestion and achieve efficient traffic distribution.

Ultradeep shafts are the only means available to extract solid mineral resources from deep within the earth, and the conditions of these shafts directly affect the working safety of the lifting system. Chain-type wireless sensor networks (CWSNs), which are mobile and self-supporting, provide a new option for mobile collaborative monitoring of ultradeep shafts by sampling panoramic images. In this paper, a topological control method for CWSNs in an ultradeep shaft based on mobile sensor nodes is proposed. First, a video sensor node that can vertically climb a rope and automatically generate power is designed. Then, a uniform chain-type deployment strategy is proposed to accommodate the actual conditions of an ultradeep shaft. Ultimately, the network repair strategies based on mobile nodes are designed to address node movement and communication failures. The research results indicate that a uniform hierarchical deployment algorithm with a scheduling strategy can achieve overall monitoring of the ultradeep shaft in a monitoring cycle and that the collaborative repair strategy can effectively maintain the linear-domain coverage of the network.

Friction and impact between steel wire rope always exist in multi-layer winding hoist during the winding-in process, in particular for an ultra-deep coal mine. To understand the friction and wear mechanisms of wire rope among the layers in the winding hoist, a series of sliding friction experiments were carried out using a self-made friction test rig. The results show that the coefficient of friction (COF) of the wire rope changes little with increasing load and stabilizes at approximately 0.73, but decreases with the sliding velocity under dry-friction condition. However, under lubrication condition, there is almost no effect of the contact load and sliding velocity on the COF, which stabilizes at approximately 0.35. Additionally, the temperature rise is concentrated at the contact area, and it increases with the load and the sliding velocity. The maximum temperature rise with the lubrication is much lower, approximately 10 °C, than that under the condition of dry-friction, which is approximately 103 °C. Furthermore, the maximum of the COF under the impact load is significantly lower than that for the stable contact friction. With the impact and sliding velocities increase, the maximum COF under the impact load experiences a slight increase and reaches a maximum value of approximately 0.36. As the impact load increases, the COF changes little, but the impact process occurs more than once.

Wear is one of the primary factors for the degradation of the wire rope used for multi-layer winding hoist. It decreases the carrying capacity and service life of the hoisting rope, which will affect the mine safety directly. In this paper, the effects of the wear scars caused by sliding friction under different crossing angles and cross directions on the mechanical response of the wire rope were investigated through the breaking tensile test. Additionally, the fracture failure mechanism of the rope samples was discussed. Results show that the surface wear decreases the breaking force of the wire rope. The distribution of wear region and the maximum wear depth of the wear scar are the major influence factors on the mechanical properties of the rope. The variation range of the breaking force is larger for the rope with the wear scar under the sliding condition of right cross contact and the damage is more serious for that in the condition of left cross contact. There is obvious plastic deformation and temperature rise near the wear scar before the rope breaks. The fracture failure mechanism is ductile fracture with necking and dimples on the surface.

This paper concerns wire rope tension control of a double-rope winding hoisting system (DRWHS), which consists of a hoisting system employed to realize a transportation function and an electro-hydraulic servo system utilized to adjust wire rope tensions. A dynamic model of the DRWHS is developed in which parameter uncertainties and external disturbances are considered. A comparison between simulation results using the dynamic model and experimental results using a double-rope winding hoisting experimental system is given in order to demonstrate accuracy of the dynamic model. In order to improve the wire rope tension coordination control performance of the DRWHS, a robust nonlinear adaptive backstepping controller (RNABC) combined with a nonlinear disturbance observer (NDO) is proposed. Main features of the proposed combined controller are: (1) using the RNABC to adjust wire rope tensions with consideration of parameter uncertainties, whose parameters are designed online by adaptive laws derived from Lyapunov stability theory to guarantee the control performance and stability of the closed-loop system; and (2) introducing the NDO to deal with uncertain external disturbances. In order to demonstrate feasibility and effectiveness of the proposed controller, experimental studies have been conducted on the DRWHS controlled by an xPC rapid prototyping system. Experimental results verify that the proposed controller exhibits excellent performance on wire rope tension coordination control compared with a conventional proportional-integral (PI) controller and adaptive backstepping controller.