In this paper, a robust recurrent neural network is presented in a Bayesian framework based on echo state mechanisms. Since the new model is capable of handling outliers in the training data set, it ...is termed as a robust echo state network (RESN). The RESN inherits the basic idea of ESN learning in a Bayesian framework, but replaces the commonly used Gaussian distribution with a Laplace one, which is more robust to outliers, as the likelihood function of the model output. Moreover, the training of the RESN is facilitated by employing a bound optimization algorithm, based on which, a proper surrogate function is derived and the Laplace likelihood function is approximated by a Gaussian one, while remaining robust to outliers. It leads to an efficient method for estimating model parameters, which can be solved by using a Bayesian evidence procedure in a fully autonomous way. Experimental results show that the proposed method is robust in the presence of outliers and is superior to existing methods.
Plasticized poly (lactic acid) (PPLA) was prepared by melt blending poly (lactic acid) (PLA) with 10 wt% of poly (ethylene glycol) (PEG), with varied molecular weights range from 400 to 4000. The ...structure, thermal property, morphology, and surface free energy of the PPLA were investigated by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and contact angles (CA). The resulting PPLA results indicated that the introduction of PEG to the blend systems resulted in a ductile fracture, a decrease in the melt temperature (Tm) and glass transfer temperature (Tg), and an increase in the degree of crystallization (χc), which indicated an improved flexibility. In addition, the polarity of the PPLA increased and the surface free energy decreased. The resulting PPLA was subsequently used as matrix to blend with wood flour to prepare composites. The mechanical strength, melting behavior, thermal stability, and microscopy of the PPLA/wood flour composites were also evaluated. These results illustrated that the plasticized PPLA matrix was beneficial to the interfacial compatibility between the polar filler and the substrate.
Rheological properties are the theoretical basis and the key to common problems in ferrofluid applications, therefore they are expected to be adjustable to satisfy different technical requirements ...through altering the microstructure of ferrofluid during the process of preparation. In this paper, Four ferrofluid samples with different magnetic particle size were prepared by controlling the concentration of precursor solution during co-precipitation process and the rheological properties of these samples were investigated. These samples exhibited field-controlled rheological properties. Eternal magnetic field would enhance the formation of microstructures, resulting in an increase of viscosity. While with the increase of shear rate, microstructures tended to be destroyed, causing viscosity to decrease. There were two opposing mechanisms of the influence of precursor solution concentration. On one hand, the reduction of the precursor solution concentration would produce primary magnetic particles of smaller size. But on the other hand, the surfactant became insufficient to completely coat the magnetic particles because of an increased specific surface area, causing the magnetic particles to aggregate and form secondary clustering structures which strongly enhanced the magnetoviscous effect and weakened the viscoelastic effect.
Photo‐crosslinkable and amine‐containing block copolymer nanoparticles are synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization‐induced self‐assembly of a ...multifunctional core‐forming monomer, 2‐((3‐(4‐(diethylamino)phenyl)acryloyl)oxy)ethyl methacrylate (DEMA), using poly(2‐hydroxypropyl methacrylate) macromolecular chain transfer agent as a steric stabilizer in methanol at 65 °C. By tuning the chain length of PDEMA, a range of nanoparticle morphologies (sphere, worm, and vesicle) can be obtained. Since cinnamate groups can easily undergo a 2 + 2 cycloaddition of the carbon–carbon double bonds upon UV irradiation, the as‐prepared block copolymer nanoparticles are readily stabilized by photo‐crosslinking to produce anisotropic nanoparticles. The crosslinked block copolymer nanoparticles can be used as templates for in situ formation polymer/gold hybrid nanoparticles.
Photo‐crosslinkable and amine‐containing block copolymer nanoparticles are synthesized via RAFT‐polymerization‐induced self‐assembly and stabilized by photo‐crosslinking. The crosslinked block copolymer nanoparticles can be used as stable templates for in situ formation of polymer/gold hybrid nanoparticles.
Although unmanned surface vehicles (USVs) have been extensively researched and applied to many typical scenarios, high-performance autonomous control is still an open problem. One of their major ...problem stems from the difficulty in constructing a sufficient accurate and sufficient simple control-oriented dynamics model. Owing to the highly complicated physical mechanisms of hydrodynamics, USV systems possess strong nonlinearities and coupling, which make it exceptionally difficult to develop an accurate model structure. In real applications, extensively existing uncertainties, such as external disturbances due to wind, wave, current, and measurement noise in the onboard sensor, will unavoidably influence identification precision with respect to the parameters in the USV's model. Thus, in this paper, a new kind of nonlinear modeling scheme-the active modeling enhanced quasi-linear parameter-varying (qLPV) model-is proposed for a water-jet propulsion USV system. First, a qLPV-structured model is derived by simplifying the real dynamics model, which has a simple quasi-linear structure and can approximate the nonlinearities of the hydrodynamics. Subsequently, a nonlinear version of the Kalman filter-based active modeling method is proposed to provide online estimates of the unstructured model to eliminate the errors due to the structure inaccuracy between the qLPV-structured model and the real system. Finally, the newly proposed modeling scheme is tested on a real USV system and its superiority is shown through comparisons to some other traditional modeling methods.
Magnetic seals as a class of non-contact sealing technology have been a research focus. In these seals, magnetic materials, usually ferrofluids or magnetorheological fluids are attracted in sealing ...gaps as sealing medium. Recently, a novel sealing method using nano-micron sized magnetic powders has been raised up as well. However, the working performance of these magnetic seals has not been studied thoroughly and comparatively yet. Here, we provide a comparative study of magnetic seals by ferrofluid, magnetorheological fluid and magnetic powder theoretically and experimentally. The formulas of pressure capability are derived based on their different properties. A modified empirical formula of magnetic powder seals is proposed, taking the frictional effect into consideration. The magnetic field distribution is calculated by the finite element method. Finally, a test bench for static magnetic seals is established. The pressure capability and leakage rate of three materials are measured by sealing experiments. The differences in mechanism of pressure transfer and the ability of self-recovery are discussed. This research summarizes the characteristics of different magnetic seals, and provides a guidance for sealing medium selection and structure design.
Magnetic fluid is a new type of functional materials. The seal of reciprocating shaft is a typical application of the magnetic fluid. However, there is little research on the magnetic fluid ...reciprocating seals, thus improving the sealing life and seal capacity is the key problem of studying the reciprocating seals. This paper presents a structure of the seal to test the sealing life and other characteristics. The magnetic field of the seal is estimated using the finite-element method. The thickness of the magnetic fluid on the surface of reciprocating shaft and the flow rate of magnetic fluid are obtained theoretically. The experimental result shows that the static seal capacity is related to the fluid volume. The static seal capacity obtained by experiment is approximately equal to the value through the simulation with sufficient magnetic fluid. The relationship between sealing life and the motion of the reciprocating shaft is obtained experimentally. The sealing life decreases rapidly with the increase of the stroke and velocity.
As a common and frequently occurring disease, heart failure has been paid more and more attention, but the mechanism of its occurrence and development is still unclear. This study investigated that ...PGAM5 expression levels in heart failure and its underlying mechanisms in vivo and in vitro.
The inhibition of PGAM5 mRNA expression levels in patients with heart failure was compared with the normal group.
The serum of PGAM5 mRNA expression was negative correlation with collagen I and collagen III in patients with heart failure. PGAM5 mRNA and protein expression in the heart tissue of mice with heart failure were down-regulated at a time-dependent rate. The inhibition of PGAM5 presented heart failure in the model. PGAM5 reduced inflammation and inhibited ROS-induced oxidative stress in models of heart failure. PGAM5 reduced Ferroptosis in models of heart failure. PGAM5 regulated Keap1/Nrf2 signaling pathway. IP also showed that PGAM5 protein combined with the Keap1 protein. PGAM5 could increase Keap1 protein ubiquitination. Keap1 inhibition affected the effects of PGAM5 in model of heart failure.
We conclude that the protection of PGAM5 reduced ROS-induced oxidative stress and ferroptosis by the Keap1/Nrf2 signaling pathway in heart failure, suggesting that targeting this mechanism of PGAM5 may be a feasible strategy to treat heart failure.
This paper concerns the nature of the peculiar second-order buoyancy experienced by a magnet in magnetic fluid acceleration sensor. The equilibrium differential equation of magnetic fluid under the ...action of magnetic field and gravity field is established and the expression for calculating the second-order buoyancy is derived. Three practical and effective methods to calculate the second-order buoyancy called surface integral method, magnetic force method, and equivalent magnetic force method are proposed. Besides, the second-order buoyancy is calculated by the three methods mentioned above and measured experimentally. The calculation results are in very good agreement with the experimental results, for all the three methods, the calculation error is less than 7% compared with the numerical range of second-order buoyancy. Both calculation and experimental results show that the second-order buoyancy increases rapidly with the decrease of the axial distance between the bottom of the magnet and the container, and the trend can be fitted well by an exponential function.
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