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A good knowledge of the reduction mechanism of visibility is fundamental to developing preventive strategies in coal mines. In this work, the Mie theory was selected for investigating the absorption and scattering of coal dust. A prediction model for evaluating the visibility was developed based on the extinction characteristics of coal dust. The optical properties have been discussed to simplify the model and clarify the relationships among the different wavelengths and diameters. Additionally, the variety of extinction coefficients can be reasonably used in guiding the calculated visibility under different conditions. The experimental results demonstrated that the reduction of visibility was attributed to the synergistic effect of the extinction of coal dust and droplet. For the field application of this prediction model, the relative errors of the calculated and measured visibility were 9.8 and 7.1% from models I and II, which reflected the small deviation between the two methods. The prediction model can accurately describe the visibility in mines due to coal dust pollution. The exploration results provide a significant reference for the development and application of air cleaning technology for increased visibility.

This paper is a research related to finite-time stability. Different from traditional fixed-time, predefined-time, and prescribed time stability that more or less have some conservativeness, we manage to stabilize system states onto the equilibrium at an arbitrarily selected time instant irrespective of initial system states and parameters. In another word, the conservativeness of convergence time in our proposed control method is proved to be zero. Moreover, the control is bounded and also gradually goes to zero at the selected instant. It is obviously an improvement compared with the existing finite-time stabilization (FNTS), such as fixed-time stabilization (FTS), predefined-time stabilization (PDTS), and prescribed-time stabilization (PSTS).The FNTS property is of great interest for scenarios where real-time constraints need to be satisfied, e.g., in missile guidance, the impact time control guidance laws require stabilization in a desired time. Our proposed PSIS can deal with the FNTS problems. For other tasks with more accurate requirement on time, the FTS, the PDTS, and the PSTS are insufficient. For instant, two robot arms playing the piano. Music has its’ rhythm, each note is expected to appear at a specific time instant, or the music will sounds terrible. There are many other tasks that are easy for human beings but difficult for robots, e.g.. dancing and sports. The author think it is because human have rhythm feeling, while robots have not. Hence, it is important to develop such control methodologies.

In this paper, a high-order nonlinear disturbance observer-based fractional-order sliding mode control (FOSMC) strategy is proposed for DC/DC buck converters in the presence of mismatched disturbances, ensuring the properties of both stability and dynamic performance. Traditional sliding mode control can deal with matched disturbances while achieving desired closed-loop performance, unfortunately it is particularly sensitive to mismatched disturbances. In the proposed control structure, two nonlinear disturbance observers are constructed to estimate both matched and mismatched disturbances in finite time. Then, the estimated variables are used for the fractional-order sliding mode surface design, where a super twisting sliding mode controller is designed to drive the states of the system to track their desired values. Comparing with the traditional SMC, the proposed method not only reduces the sensitivity of the system to mismatched disturbance, but also improves the transient performance of the system. Simulation and experimental results have comprehensively illustrated the feasibility and effectiveness of the proposed strategy.

Water jet technology is an effective measure by which to improve the efficiency of deep coalbed methane mining. Nevertheless, the effect of a water jet impinging on coal rock remains unclear. In this study, numerical simulation is used to analyze a water jet impingement drill test block, after which experimental verification is carried out. Next, on the basis of the experimental verification that the simulation method is feasible, the influence factors of the water jet impingement in the drill hole are analyzed. It is concluded that the phase-field variables based on the fracture change method can effectively characterize the damage and destruction of coal rock. The water jet impact in the borehole has a central damage failure zone and two-side damage failure zone, and the damage failure ratio n is used to characterize the degree of damage to the coal rock. When the jet target distance is 70 mm, the damage ratio n is closest to 1, and the effect of water jet impact on coal-rock is the best. When the wall roughness is less than 10 mm, the blocking effect on the jet is dominant, resulting in a negative correlation between the damage size and the roughness. When the wall roughness exceeds 10 mm, the development of cracks and the connection effect exceed the blocking effect, resulting in larger damage. Therefore, it can be seen that the effect of a water jet impacting on coal rock is positively related to jet pressure. When the jet target distance is 70 mm, the damage range of 30 MPa jet pressure to the center and both sides of the coal rock reaches about 1.1 m, thus signifying a good coal rock breaking effect. The wall roughness has a significant effect on the coal rock breaking effect of the water jet.

Coal spontaneous combustion in underground mine goaf has a great impact on coal mining. The temperature-programmed experiment is a commonly used and effective method for studying the characteristics of coal spontaneous combustion. Aiming at the problem that the numerical simulation of coal spontaneous combustion characteristics under the condition of external air supply and temperature control in a temperature-programmed experiment is insufficient, a multi-physical field coupling numerical model of coal spontaneous combustion in the temperature-programmed experiment is established. The variation characteristics of coal temperature, oxygen, and oxidation products under external air supply and temperature control were studied. The results show that the numerical simulation results are consistent with the experimental results. With the increase in temperature, the volume fractions of oxygen and carbon dioxide decrease and increase, respectively. As the air supply volume increases, the oxygen volume fraction at the outlet increases, and the peak value of the oxygen volume fraction change rate exhibits a “hysteresis” feature, and the time corresponding to the peak value increases. Moreover, the temperature change rate increases. With the increase in the heating rate, the peak value of the oxygen volume fraction change rate increases and shows an “early appearance” characteristic, at the same time, the maximum coal temperature displays a linear increase trend.

Owing to the destructiveness of the coal–gas outburst (CGO) two-phase flow, a custom-made large-scale test system was used to perform CGO experiments under different gas pressures in this study. The effects of the gas pressure on the migration, the CGO intensity, and the impact characteristics of the CGO two-phase flow were examined. Finally, a physical model containing three key structures was established. The results revealed that a higher initial gas pressure resulted in a higher solid–gas ratio of the coal–gas two-phase flow, a higher initial motion speed of the CGO coal, and a higher CGO intensity. Considerable choking of the two-phase flow occurred in the roadway, and it became more severe with the increasing gas pressure. During the attenuation of the impact force, strong and weak disturbances occurred intermittently. During the CGO process, a strong-disturbance zone developed in the middle of the roadway.

This study is concerned with the event-triggered finite-time control of periodic systems via a piecewise method. The continuous-time periodic system is formulated by finite-number linear time-invariant subsystems, of which the system parameters are determined by the piecewise approximation method. In consideration of the mitigation of network communication in networked control loops, some event-triggering mechanisms are designed in terms of the networks between the sensor (or controller) and the controller (or actuator). Three different event-triggered control schemes are designed for the networked periodic system. The finite-time stability of the resulting closed-loop system is analysed by using a Lyapunov function approach with a well-defined matrix-valued function. The controller gains depending on the piecewise parameters are thus designed with several matrix inequalities that can be solved by off-line procedures. Finally, a numerical example is provided to illustrate the effectiveness of the proposed design scheme.

Introduction Diabetic kidney disease (DKD) is a major microvascular complication of diabetes mellitus (DM) and the primary cause of end-stage renal disease. Routine medication might result in adverse effects which limit their usage. Laboratory studies have shown that Xiao Zheng San Jie (XZSJ) granules is effective in reducing the levels of urinary protein and blood creatinine in rats with DKD. Hence, we aim to conduct a clinical trial to determine the efficacy and safety of XZSJ granules among patients with DKD Stage IV, who present with the syndromes of qi deficiency and blood stasis. The purpose of this paper is to report the methodology of this trial.Methods and analysisThis is a randomised, double-blind, placebo-controlled, multi-centre clinical trial. A total of 72 patients with DKD Stage IV who have the syndromes of qi deficiency and blood stasis will be randomly assigned to either intervention or placebo group. In addition to routine medication, the intervention group will be given XZSJ formula (in granules) and the control group will be given placebo for 12-weeks. Data collected at baseline as well as weeks 4, 8 and 12 will be recorded in case report forms and subsequently entered into EpiData 3.1 electronic database. Adverse events will also be documented. Primary outcomes – estimated glomerular filtration rate, urinary albumin-to-creatinine ratio, and serum creatinine – will be assessed after 12 weeks. Ethics and disseminationThis trial has been approved by the Research Ethics Committee of Dongzhimen Hospital (DZMEC-KY-2018-60). Informed consent will be obtained from all participants. Results of this study will be disseminated to the public through academic conferences and peer-reviewed journals.DiscussionThis trial might provide information on an effective method for the treatment of DKD, especially for patients who present with the syndromes of qi deficiency and blood stasis. We hope that this trial will serve as a reference for the conception of high-quality Traditional Chinese Medicine trials in the future, which incorporate syndrome diagnosis into the study design.Trial registration Chinese Clinical Trial Registry, ChiCTR1900021391. Registered 18 February 2018, http://www.chictr.org.cn/showproj.aspx?proj=36106.

In this paper, a model-based robust control is proposed for the polymer electrolyte membrane fuel cell air-feed system, based on the second-order sliding mode algorithm. The control objective is to maximize the fuel cell net power and avoid the oxygen starvation by regulating the oxygen excess ratio to its desired value during fast load variations. The oxygen excess ratio is estimated via an extended state observer (ESO) from the measurements of the compressor flow rate, the load current, and the supply manifold pressure. A hardware-in-loop test bench, which consists of a commercial twin screw air compressor and a real-time fuel cell emulation system, is used to validate the performance of the proposed ESO-based controller. The experimental results show that the controller is robust and has a good transient performance in the presence of load variations and parametric uncertainties.

In this paper, a distributed filtering scheme is presented to deal with the fault detection problem of nonlinear stochastic systems with wireless sensor networks (WSNs). The nonlinear stochastic systems, which are of discrete-time form, are represented by interval type-2 (IT2) Takagi–Sugeno (T–S) fuzzy models. Each sensor of the WSN can receive measurements from itself and its neighboring sensors subject to a deterministic interconnection topology. Independent random variables obeying the Bernoulli distribution are formulated to characterize the randomly occurred packet losses between the WSN and the filter unit. To generate residual signals for evaluation functions of the fault detection mechanism, a novel type of IT2 T–S fuzzy distributed fault detection filter is proposed corresponding to each sensor node. Additionally, a fault reference model is adopted for improving the performance of the fault detection system. A new overall fault detection system is formulated in an IT2 T–S fuzzy model framework. Applying Lyapunov functional approach, we concentrate on the analysis of stability and performance of the resulting fault detection system. New techniques are utilized to handle the decoupling problem in design procedure. The desired parametric matrices of the fuzzy filters are designed subject to a developed criterion, which is a sufficient condition of the robust mean-square asymptotic stability for the overall fault detection system with a disturbance attenuation performance. Finally, a truck-trailer system with a four-node WSN is established for simulation validation. In simulations, the mincx function of the MatLab 2017a in Windows 10 OS is used to optimize the level of the disturbance attenuation performance, and to obtain the filter gains for the established system. By comparing the different time instants when the residual evaluation functions exceed their respective thresholds, simulation results successfully validate the effectiveness and applicability of the presented distributed fault detection scheme.

This paper presents a tracking control scheme with quantization mechanism for hypersonic flight vehicles (HFVs) with prescribed performance using an interval type-2 fuzzy neural network (IT2FNN). A parameterized tracking error model of the HFV is derived with some considered uncertainties, which are approximated by an IT2FNN. The tracking control of the velocity and altitude of the HFV is designed by using a prescribed performance control technique. It allows that transient characteristics of the tracking errors can be improved and adjusted by some prescribed performance functions. According to an adaptive backstepping control design procedure, novel continuous control laws of the fuel equivalency ratio, canard deflection, and elevator deflection are designed with logarithmic quantization mechanism, for the sake of avoiding inadvertently increasing the effective gains of continuous controllers as well as reducing loads of the communication from controller unit to actuator unit. Besides, the limited tracking errors of the flight path angle and angle-of-attack can be achieved by applying the designed controllers. Finally, the presented tracking controllers with quantization mechanism are validated by comparative simulations.

This paper is concerned with the problems of observer-based sliding mode control and fault estimation for Lipschitz nonlinear systems. The concerned plants are characterized with an actuator fault deviation existing in state dynamics and measured outputs. It represents a more general faulty plant case than those considered in the existing literature. Comparing with existing results on the sliding mode control procedure design, we propose new techniques to overcome the difficulty caused by parametric perturbation and measured noise existing in system output. For precisely estimating the plant states and the faults simultaneously, a novel estimation technique is developed to tackle the influence from the fault deviation. Based on the state estimation, an integral-type sliding mode control scheme by the utilization of an augmented sliding mode observer is presented for the stabilization of the faulty plants. Finally, an electromechanical system is applied to validate the availability and applicability of the presented control methods.

Aconitine, a CThe present paper reviews research progress relating to the pharmacokinetics, physiological and pathological processes of aconitine, while some promising research direction and the detoxification of aconitine are also discussed.The accessible literature on aconitine, from 1990 to 2020, obtained from published materials of electronic databases, such as SCI finder, PubMed, Web of Science, Science Direct, Springer and Google Scholar was systematically analyzed.In this review, we address the pharmacokinetics of aconitine, as well as its pharmacological effects including anti-cancer, anti-inflammatory, anti-virus, immunoregulation, analgesic, insecticide and inhibition of androgen synthesis. Further, we summarize the toxicity of aconitine such as cardiotoxicity and neurotoxicity, on which we strikingly focus on the ways to reduce the toxicity of aconitine based.Aconitine plays an vital role in a wide range of physiological and pathological processes and we can reduce the toxicity of aconitine by compatibility and hydrolysis. Although some issues still exist, such as the correlative relationship between the dose and toxicity of aconitine not being clear, our review may provide new ideas for the application of aconitine in the treatment of related diseases.

Obesity and related metabolic disorders are associated with intestinal microbiota dysbiosis, disrupted intestinal barrier and chronic inflammation. Shen-Yan-Fang-Shuai formula (SYFSF) is a traditional Chinese herbal formula composed of Astragali Radix, Radix Angelicae Sinensis, Rheum Officinale Baill, and four other herbs. In this study, we identified that SYFSF treatment prevented weight gain, low-grade inflammation and insulin resistance in high-fat diet (HFD)-fed mice. SYFSF also substantially improved gut barrier function, reduced metabolic endotoxemia, as well as systemic inflammation. Sequencing of 16S rRNA genes obtained from fecal samples demonstrated that SYFSF attenuated HFD-induced gut dysbiosis, seen an decreased Firmicutes to Bacteroidetes ratios. Microbial richness and diversity were also higher in the SYFSF-treated HFD group. Furthermore, similar therapeutic effects and changes in gut microbiota profile caused by SYFSF could be replicated by fecal microbiota transfer (FMT). Taken together, our study highlights the efficacy of SYFSF in preventing obesity and related metabolic disorders. Its therapeutic effect is associated with the modulation of gut microbiota, as a prebiotic.

In this chapter, we focus on output feedback control and observer design for two types of commonly used microgrid power converters, that is, three-phase two-level AC/DC power converters and DC/DC converters. As is well known, the sliding mode control (SMC) is naturally well suited for the control of variable structure systems. Since power converters inherently include switching devices, making them belong to variable structure systems; therefore, it is straightforward to apply SMC that yields a discontinuous control law. Moreover, given that power converters are usually modeled using the state space averaging method, SMC forms an efficient analysis and design tool for the control of switched mode power converters, because it offers excellent large-signal handling capability. Conventional linear control is small signal based; it only allows one to optimally operate the converters for a specific range of operating conditions and often fails to achieve satisfactory performance under large parameter/load variations, that is, large signal operating condition. SMC as a kind of nonlinear control method is suitable for controlling the power converters, which is able to achieve better regulation and dynamical performance for a wider range of operating conditions. The main reason is that there is no need to have a linear model of the power converter for nonlinear controller design. However, the main obstacle associated with the application of SMC is its variable frequency nature, which makes the design of output filter difficult. Nonetheless, if this problem is properly handled, SMC is a powerful control design method for power converters and has huge potential in industrial applications. The three-phase two-level ACDC power converter acts as a rectifier or voltage source inverter (VSI). When acting as a rectifier, it is the primary interface for a wind turbine (WT) generator, converting the WT source AC voltage to a varying output DC voltage following the maximum power point tracking (MPPT) control. As a microgrid is normally an AC microgrid, the VSI is the most important module of the converters, which works as a DC/AC converter. VSI interfaces among the renewable energy source (RES) DC-link output, energy storage system (ESS) DC-link output, and the microgrid. It converts DC voltage to AC voltage with the microgrid voltage magnitude and frequency, in order to inject the active and reactive power to the microgrid. The control objectives of AC/DC converter are: (1) DC-link voltage regulation; and (2) AC current tracking with the possible lowest harmonic distortion. The DC/DC converter converts a source of direct current from one voltage level to the fixed or adjustable one. In a microgrid, a DC/DC converter is used in the following scenarios: (1) working as a primary interface for photovoltaic panels, which converts the PV source DC voltage to an adjustable output DC voltage based on the MPPT control; (2) for a DC microgrid, the DC/DC converter acts as an interface among the microgrid, DC loads, RES DC-link output, and the ESS, such as batteries and flywheels. In this scenario, the DC/DC output voltage is a fixed one. To control the DC/DC converter, great control effort should be made to regulate the output voltage to the desired value, due to input voltage disturbances and abrupt load variation. From a control point of view, the control design for boost converters is more difficult than the buck type, because its standard model is a nonminimum phase system. Traditionally, the control problems of the DC/DC converters are solved by using pulse width modulation (PWM) techniques, in which an external high-frequency signal is used to modulate a low-frequency desired function to be tracked. In view of practical implementation, SMC is much easier than a PWM control, since the maximum frequency of commercially available switching elements increases higher and higher. In this chapter, a novel observer-based control is proposed for both three-phase two-level grid-connected power converters and DC/DC buck converters. The proposed control technique forces the input currents to track the desired values, which can indirectly regulate the output voltage while achieving a user-defined power factor. The presented approach has two control loops. A current control loop based on the sliding mode technique and a DC-link voltage regulation loop which consists of an extended state observer (ESO) plus SMC are adopted. The load connected to the DC-link capacitors is considered as an external disturbance. An ESO is used to reject asymptotically this external disturbance. Therefore, its design is considered in the control law derivation to achieve a high performance. SMC is known for the low sensitivity to disturbances and parameter variations, making it an effective method to deal with the nonlinear behavior of complex systems. It has been demonstrated to be a highly promising solution for power electronic systems, such as switching DC/DC power converters, grid-connected power converters, and motor drives. The sliding mode approach is expected to become increasingly popular in the field of power converter control. This chapter will be organized as follows. Section 1 begins with an introduction to the fundamental theory and methodology of SMC to familiarize readers with the main principle and background of SMC. Section 2 will discuss the mathematical models of three-phase grid-connected AC/DC power converters and DC/DC buck converters. Next, in Section 3 , the design of the SMC and output feedback control for aforementioned power converters will be presented, and the simulation results comparing the performance of the proposed control with the conventional proportional-integral controller will be discussed. Finally, some conclusions are drawn in Section 4 .

This paper presents a new sliding mode control (SMC) design methodology for fuzzy singularly perturbed systems (SPSs) subject to matched/unmatched uncertainties. To fully accommodate the model characteristics of the systems, a novel integral-type fuzzy switching surface function is put forward, which contains singular perturbation matrix and state-dependent input matrix simultaneously. Its corresponding sliding mode dynamics is a transformed fuzzy SPSs such that the matched uncertainty/perturbation is completely compensated without amplifying the unmatched one. By adopting a $\boldsymbol \varepsilon $ -dependent Lyapunov function, sufficient conditions are presented to guarantee the asymptotic stability of sliding mode dynamics, and a simple search algorithm is provided to find the stability bound. Then, a fuzzy SMC law is synthesized to ensure the reaching condition despite matched/unmatched uncertainties. A modified adaptive fuzzy SMC law is further constructed for adapting the unknown upper bound of the matched uncertainty. The applicability and superiority of obtained fuzzy SMC methodology are verified by a controller design for an electric circuit system.