Dynamic Characterization of Periodic Lattice of Elastically-connected Bi-stable Elements under Seismic Excitation

Metamaterials are engineered materials, typically in periodic arrangements, which exhibit unconventional or extreme properties not found in nature. Understanding the dynamics of metamaterials enables the design of structures with specific functionalities. The dynamics of metamaterials in linear regime has been relatively well studied in recent years, however the unique phenomena arising from nonlinearities in metamaterials are yet to be explored. In this paper, we focus on an array of bi-stable elements connected by elastic springs under various forms of external excitations acting on the entire system. The general equations of motion are derived to handle any degree-of-freedom (DoF) systems of interest. The MATLAB-based code is developed using finite difference method to solve numerically the system of equations and is validated through the correlation studies with the analytical solutions in previously known linear systems. Numerical investigations are performed on 2-DoF and infinitely-long systems under various excitation levels with focuses on nonlinear responses. The predicted behaviors are experimentally verified from the dynamic testing, using 3D-printed lattice samples

PM2.5-GNN: A Domain Knowledge Enhanced Graph Neural Network For PM2.5 Forecasting

When predicting PM2.5 concentrations, it is necessary to consider complex information sources since the concentrations are influenced by various factors within a long period. In this paper, we identify a set of critical domain knowledge for PM2.5 forecasting and develop a novel graph based model, PM2.5-GNN, being capable of capturing long-term dependencies. On a real-world dataset, we validate the effectiveness of the proposed model and examine its abilities of capturing both fine-grained and long-term influences in PM2.5 process. The proposed PM2.5-GNN has also been deployed online to provide free forecasting service.Comment: Pre-print version of a ACM SIGSPATIAL 2020 poster [paper](https://dl.acm.org/doi/10.1145/3397536.3422208). The code is available at [Github](https://github.com/shawnwang-tech/PM2.5-GNN), and the talk is available at [YouTube](https://www.youtube.com/watch?v=VX93vMthkGM

Zwitterionic coating assisted by dopamine with metal-phenolic networks loaded on titanium with improved biocompatibility and antibacterial property for artificial heart

Introduction: Titanium (Ti) and Ti-based alloy materials are commonly used to develop artificial hearts. To prevent bacterial infections and thrombus in patients with implanted artificial hearts, long-term prophylactic antibiotics and anti-thrombotic drugs are required, and this may lead to health complications. Therefore, the development of optimized antibacterial and antifouling surfaces for Ti-based substrate is especially critical when designing artificial heart implants.Methods: In this study, polydopamine and poly-(sulfobetaine methacrylate) polymers were co-deposited to form a coating on the surface of Ti substrate, a process initiated by Cu2+ metal ions. The mechanism for the fabrication of the coating was investigated by coating thickness measurements as well as Ultraviolet–visible and X-ray Photoelectron (XPS) spectroscopy. Characterization of the coating was observed by optical imaging, scanning electron microscope (SEM), XPS, atomic force microscope (AFM), water contact angle and film thickness. In addition, antibacterial property of the coating was tested using Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) as model strains, while the material biocompatibility was assessed by the antiplatelet adhesion test using platelet-rich plasma and in vitro cytotoxicity tests using human umbilical vein endothelial cells and red blood cells.Results and discussion: Optical imaging, SEM, XPS, AFM, water contact angle, and film thickness tests demonstrated that the coating was successfully deposited on the Ti substrate surface. The biocompatibility and antibacterial assays showed that the developed surface holds great potential for improving the antibacterial and antiplatelet adhesion properties of Ti-based heart implants

Effects of sample dimensions and shapes on measuring soil–water characteristic curves using pressure plate

It is well known that soil–water characteristic curve (SWCC) plays an important role in unsaturated soil mechanics, but the measurement of SWCC is inconvenient. In laboratory it requires days of testing time. For fine-grained clays, it may last for a couple of months using pressure plate tests. In this study, the effects of sample dimensions and shapes on the balance time of measuring SWCCs using pressure plate tests and the shape of SWCCs are investigated. It can be found that the sample dimensions and shapes have apparent influence on the balance time. The testing durations for circular samples with smaller diameters and annular samples with larger contact area are significantly shortened. However, there is little effect of sample dimensions and shapes on the shape of SWCCs. Its mechanism is explored and discussed in details through analysing the principle of pressure plate tests and microstructure of the sample. Based on the above findings, it is found that the circular samples with smaller dimensions can accelerate the testing duration of SWCC using the pressure plate

Interaction of Preformed Particle Gel and Sodium Dodecyl Sulfate

The adsorption of anionic surfactant of sodium dodecyl sulfate (SDS) onto preformed particle gel (PPG) and the effects of SDS on the swelling ratio of PPG were combined. The effects of anionic surfactant sodium dodecyl sulfate on the rheology of preformed particle gel were also studied by using steady shear and oscillatory shear rheological experiments. The interaction mechanism of SDS and the rheology of preformed particle gel was discussed. The results show that the adsorption of SDS increases and the swelling ratio of PPG first decreases and then keeps stable with the increase of SDS. The preformed particle gel exhibits shear-thinning property and its viscosity is significantly influenced by SDS at lower shear rate. With the increase of SDS concentration, the yield stress of the preformed particle gel decreases and the storage modulus first decreases and then increases

Factors Influencing HPAM Solution Viscosity Prepared by Produced Water Using Orthogonal Method

The effect of temperature and metal ion components on the viscosity of HPAM solution was studied by means of orthogonal method. Five factors and 4 levels were considered for the orthogonal design. The five factors included temperature, contents of Na+, Mg2+, Ca2+ and S2-, and the four levels mainly considered the level of produced water components in main oilfields in China. The experiment results show that temperature is the most important factor to control HPAM solution viscosity prepared by produced water. The effect of ions was in order of Na+\u3eS2-\u3eMg2+\u3eCa2+. The mechanism of each factor influencing viscosity was also discussed. Based on the actual condition of Nanyang oilfield, the desulfurization was used to improve the solution viscosity, and satisfactory result was obtained

Mechanism of Sulfide Effect on Viscosity of HPAM Polymer Solution

The effect of sulfide on HPAM solution viscosity was studied using BROOKFIELD DV-II viscometer, and the interaction mechanism was discussed. The HPAM solution viscosity was investigated through fully reducing sulfide by the addition of hydrogen peroxide oxidation, and the mechanism of increasing polymer viscosity was investigated. The experimental results also show that there is a critical concentration of 15 mg/L. Below it, the loss rate of HPAM solution viscosity increases more rapidly, but becomes slowly above the critical concentration. A theoretical guidance for oilfields to prepare polymer solution using sewage-water by eliminating sulfide, and it is also importance to prepare polymer solution using sewage-water and save fresh water

PLXNC1 interference alleviates the inflammatory injury, apoptosis and extracellular matrix degradation of IL-1β-exposed chondrocytes via suppressing GRP78 expression

Abstract Background Osteoarthritis (OA) is a frequently encountered debilitating joint disorder. Whether plexin C1 (PLXNC1) is implicated in OA is far from being investigated despite its well-documented pro-inflammatory property in human diseases. The goal of this study is to expound the specific role of PLXNC1 in OA and elaborate the probable action mechanism. Methods Firstly, PLXNC1 expression in the cartilage tissues of patients with OA was examined with GEO database. In interleukin-1beta (IL-1β)-induced OA cell model, RT-qPCR and western blotting tested the expression of PLXNC1, glucose-regulating protein 78 (GRP78) and extracellular matrix (ECM) degradation-related factors. Cell viability and inflammation were respectively judged by CCK-8 assay and RT-qPCR. TUNEL and western blotting estimated cell apoptosis. The potential binding between PLXNC1 and GRP78 was corroborated by Co-IP assay. Western blotting also tested the expression of endoplasmic reticulum stress (ERS)-associated proteins. Results As it turned out, PLXNC1 expression was elevated in the cartilage tissues of patients with OA and IL-1β-treated chondrocytes. When PLXNC1 was depleted, the viability injury, inflammation, apoptosis and ECM degradation of chondrocytes exposed to IL-1β were obstructed. Besides, GRP78 bond to PLXNC1 in IL-1β-treated chondrocytes. The ascending GRP78 expression in the chondrocytes exposed to IL-1β was depleted after PLXNC1 was silenced. Meanwhile, the impacts of PLXNC1 deficiency on the viability, inflammatory response, apoptosis, ECM degradation as well as ERS in IL-1β-exposed chondrocytes were abolished by GRP78 up-regulation. Conclusion In summary, PLXNC1 silencing might interact with and down-regulate GRP78 to mitigate the apoptosis, inflammation, and ECM degradation of IL-1β-insulted chondrocytes in OA

Viscoelastic Rheological Property of Different Types of Polymer Solutions for Enhanced Oil Recovery

The capability of hydrophobic association polymer (HAPAM) to displace oil is different from that of hydrolyzed polyacrylamide (HPAM) because they have different rheological properties. The viscoelasticity of five polymers was measured using Physica MCR301 rheometer and was compared. The five polymers include three HAPAMs with relative molecular mass of 1 248x104 (Type I), 750x104 (Type II), and 571x104 (Type III) separately and two HPAMs with relative molecular mass of 1 200x104 and 3 800x104 respectively. The experiment results indicate that the viscoelasticity of HAPAM is better than that of HPAM. The storage modulus G\u27 and the loss modulus G for HAPAM solutions are also larger than those for HPAM. Comparing the rheological curves of different HAPAM types, it is found that the viscosity of type II and type III is almost same at different shear rates while the viscosity of type I is the lower than that of Types II and III. The storage modulus G\u27 and the loss modulus G for three types of HAPAM were measured in low oscillation frequency range, and the results show that G\u27 is greater than G for all three different types of HAPAM, but their loss modulus is almost same, and the G\u27 is in the order of type II\u3etype III\u3etype I. In addition, the G\u27 and G increase with aging time for all three HAPAM solutions were stayed at different days. The viscoelasticity of type I reaches the highest value when aging time is 9 d at 45 °C, but it is 7 d for type II and type III. The different viscoelasticity properties can be attributed to self-organization supermolecule networks which is formed by hydrophobic association of HAPAM molecular and molecular chain entanglement

Interaction of Preformed Particle Gel and Nonionic Surfactant Triton X-100

The adsorption of nonionic surfactant Triton X-100 onto preformed particle gel (PPG) was studied. It is indicated that the adsorption isotherms of Triton X-100 onto PPG can well be fitted by Langmuir model which is used to describe the monolayer molecule adsorption. The effect of Triton X-100 on the swelling ratio of PPG was discussed using laser size meter and it is found that the size of PPG decreases in the presence of Triton X-100. The steady and dynamic rheological experiments results show that PPG exhibits shear-thinning property and is easily broken under shearing in the presence of Triton X-100. With increase of Triton X-100 concentration, the storage modulus of PPG decreases