A novel MR device with variable stiffness and damping capability

This paper proposes a novel device based on the Magnetorheological (MR) fluid which has the capability to change stiffness and damping under control. MR fluid is a type of smart material whose properties could be controlled by the external magnetic field. Most of MR devices are MR dampers, which normally are used as variable damping devices. The presented device consists of two hydro-cylinder-spring structures and one MR valve linking these two structures. The rheological characteristics of MR fluid in the fluid flow channels of MR valve are controlled by the strength of magnetic fields, which directly affect the link conditions. The equivalent stiffness and damping coefficients of the device thus varies with the rheological characteristics of MR fluid simultaneously. A mathematical model is established to describe the properties of the proposed device based on the Bouc-wen model. The mathematical model the simulation results indicate that the proposed device can control both the stiffness and damping which has potential to be applied for restrain vibration mitigation efficiently

Entropy regulation in LaNbO4-based fergusonite to implement high-temperature phase transition and promising dielectric properties

High-entropy effect is a novel design strategy to optimize properties and explore novel materials. In this work, (La1/5Nd1/5Sm1/5Ho1/5Y1/5)NbO4 (5RNO) high-entropy microwave dielectric ceramics were successfully prepared in the sintering temperature (S.T.) range of 1210–1290 ℃ via a solid-phase reaction route, and medium-entropy (La1/3Nd1/3Sm1/3)NbO4 and (La1/4Nd1/4Sm1/4Ho1/4)NbO4 (3RNO and 4RNO) ceramics were compared. The effects of the entropy (S) on crystal structure, phase transition, and dielectric performance were evaluated. The entropy increase yields a significant increase in a phase transition temperature (from monoclinic fergusonite to tetragonal scheelite structure). Optimal microwave dielectric properties were achieved in the high-entropy ceramics (5RNO) at the sintering temperature of 1270 ℃ for 4 h with a relative density of 98.2% and microwave dielectric properties of dielectric permittirity (εr) = 19.48, quality factor (Q×f) = 47,770 GHz, and resonant frequency temperature coefficient (τf) = –13.50 ppm/℃. This work opens an avenue for the exploration of novel microwave dielectric material and property optimization via entropy engineering

The Modulatory Properties of Astragalus membranaceus Treatment on Triple-Negative Breast Cancer: An Integrated Pharmacological Method.

Background: Studies have shown that the natural products of Astragalus membranaceus (AM) can effectively interfere with a variety of cancers, but their mechanism of action on breast cancer remains unclear. Triple-negative breast cancer (TNBC) is associated with a severely poor prognosis due to its invasive phenotype and lack of biomarker-driven-targeted therapies. In this study, the potential mechanism of the target composition acting on TNBC was explored by integrated pharmacological models and in vitro experiments. Materials and Methods: Based on the Gene Expression Omnibus (GEO) database and the relational database of Traditional Chinese Medicines (TCMs), the drug and target components were initially screened to construct a common network module, and multiattribute analysis was then used to characterize the network and obtain key drug-target information. Furthermore, network topology analysis was used to characterize the betweenness and closeness of key hubs in the network. Molecular docking was used to evaluate the affinity between compounds and targets and obtain accurate combination models. Finally, in vitro experiments verified the key component targets. The cell counting kit-8 (CCK-8) assay, invasion assay, and flow cytometric analysis were used to assess cell viability, invasiveness, and apoptosis, respectively, after Astragalus polysaccharides (APS) intervention. We also performed western blot analysis of key proteins to probe the mechanisms of correlated signaling pathways. Results: We constructed "compound-target" (339 nodes and 695 edges) and "compound-disease" (414 nodes and 6458 edges) networks using interaction data. Topology analysis and molecular docking were used as secondary screens to identify key hubs of the network. Finally, the key component APS and biomarkers PIK3CG, AKT, and BCL2 were identified. The in vitro experimental results confirmed that APS can effectively inhibit TNBC cell activity, reduce invasion, promote apoptosis, and then counteract TNBC symptoms in a dose-dependent manner, most likely by inhibiting the PIK3CG/AKT/BCL2 pathway. Conclusion: This study provides a rational approach to discovering compounds with a polypharmacology-based therapeutic value. Our data established that APS intervenes with TNBC cell invasion, proliferation, and apoptosis via the PIK3CG/AKT/BCL2 pathway and could thus offer a promising therapeutic strategy for TNBC

A VSG-Based Coordinated DC Voltage Control for VSC-HVDC to Participate in Frequency Regulation

In this paper, a coordinated DC voltage control strategy is proposed based on the VSG (virtual synchronous generator) method for the VSC-HVDC transmission system to participate in the frequency regulation of the connected weak grid. The voltage and power control capability of the VSC-HVDC is explored to attenuate the rate of change of frequency and to diminish the deviation of frequency. This is realized by the coordinated control of DC voltages at both the sending and the receiving ends with the VSG method. A small-signal model is established to investigate the dynamics of the control system. A tuning method for the selection of control parameters is also discussed in detail. The validity and superiority of the proposed control strategy are tested in the scenarios of sudden load changes and short circuit faults

Research on the Shear Behaviour of Composite Shear Connectors

In order to make full use of the advantages of welded stud and perfobond rib shear connectors, a new type of composite shear connector is proposed. Studs are welded to the perforated steel plate of the PBL connectors. Six specimens were designed and tested to investigate the shear behaviour of the composite connectors. The effects of the hole number, welded stud number, and end-bearing modes on the shear behaviour of the composite connectors were discussed. In addition, the composite connectors were compared with the conventional welded stud and perfobond rib connectors to analyse the difference in shear performance. The composite connectors’ shear behaviours are significantly better than those of welded stud connectors and PBL connectors. The experimental results show that increasing the number of welded studs and perforated holes and end-bearing concrete can significantly improve the shear performance of composite connectors. Secondly, a finite element model was established considering the nonlinearity of the structure and was validated based on the experimental results. Finally, the effects of reinforcement diameter, welded stud diameter, and concrete strength on the shear performance of composite connectors were analysed. The shear resistance increases as the penetrating rebar diameter, welded stud diameter, and concrete strength increase. Moreover, the overall damage level of the concrete can be significantly affected

Research on the Shear Behaviour of Composite Shear Connectors

In order to make full use of the advantages of welded stud and perfobond rib shear connectors, a new type of composite shear connector is proposed. Studs are welded to the perforated steel plate of the PBL connectors. Six specimens were designed and tested to investigate the shear behaviour of the composite connectors. The effects of the hole number, welded stud number, and end-bearing modes on the shear behaviour of the composite connectors were discussed. In addition, the composite connectors were compared with the conventional welded stud and perfobond rib connectors to analyse the difference in shear performance. The composite connectors’ shear behaviours are significantly better than those of welded stud connectors and PBL connectors. The experimental results show that increasing the number of welded studs and perforated holes and end-bearing concrete can significantly improve the shear performance of composite connectors. Secondly, a finite element model was established considering the nonlinearity of the structure and was validated based on the experimental results. Finally, the effects of reinforcement diameter, welded stud diameter, and concrete strength on the shear performance of composite connectors were analysed. The shear resistance increases as the penetrating rebar diameter, welded stud diameter, and concrete strength increase. Moreover, the overall damage level of the concrete can be significantly affected

The origin of weak coupling between polar clusters in Ta

Ta2O5-doped 0.94Bi0.5Na0.5 TiO3-0.06BaTiO3 [($1-{x}$ )(0.94BNT-0.06BT)-xTa (${x} = 0.00\text{--}0.02$ )] ceramics were prepared by a solid-state reaction technique. The single perovskite structure with space group R3c of the ceramics was identified by X-ray diffraction (XRD). Raman spectroscopy revealed the evolution of the local structure with Ta2O5 concentration. The temperature dependence of dielectric permittivity of the ceramics were deconvoluted by three Gaussian distribution functions which suggests that three dielectric anomalies exist in this system. The low-temperature dielectric anomaly exhibits a typical relaxor behavior with strong frequency dispersion (reentrant relaxor behavior). The activation energy derived from the V-F law is 0.298 eV, 0.338 eV, 0.412 eV and 0.449 eV, for ${x} = 0.00$ , 0.005, 0.01 and 0.02, respectively. The mid-temperature and high-temperature anomalies are attributed to two structure phase transitions. The increase of the activation energies suggests that the coupling between polar clusters or polar nanoregions (PNRs) becomes weaker. The origin of the interaction between PNRs and phase transition behavior has been proposed according to the average structure, local structure and defect compensation mechanism of the system