Abstract The 1/3 subharmonic resonance response of Duffing oscillator with Coulomb dry friction under foundation excitation is investigated, and the approximate analytical solution of the subharmonic resonance of the system is obtained by using the incremental averaging method. Based on the approximate analytical solution of the primary resonance obtained by the averaging method, the approximate analytical solution of subharmonic resonance is solved by the averaging method according to the incremental equation, and the amplitude–frequency response equation of subharmonic resonance is obtained. It is found that the Coulomb friction affects the amplitude–frequency response of both the primary resonance and subharmonic resonance of the nonlinear dry friction system in the form of equivalent damping. The comparison between the approximate analytical solution and the numerical solution shows that the approximate analytical solutions of the primary resonance and subharmonic resonance are both in very good agreement with the numerical solution. The existence condition of the 1/3 subharmonic resonance for the nonlinear dry friction system is presented, and the stability of the steady-state solution of subharmonic resonance is also judged. Based on the approximate analytical solution, the effects of the nonlinear stiffness and the Coulomb friction on the amplitude–frequency response of resonance and critical frequency of 1/3 subharmonic resonance of the nonlinear dry friction system are analyzed in detail. The analysis results show that the incremental averaging method can effectively obtain the approximate analytical solution in unified form for the subharmonic resonance of nonlinear system with Coulomb friction.
The main cause of the low prediction accuracy in non-invasive blood glucose monitoring with near-infrared (NIR) spectroscopy is that the variations induced by the changes of the measuring system in the prediction data set are inconsistent with those in the calibration data set.In this paper, a method to improve the robustness of the calibration models is proposed, in which the information of the matrix background is introduced as a variable into the calibration data and the three-way tensor is used to build the regression model.The idea of constructing regression models based on the hybrid algorithms consists of two steps.The first is to build a parallel factor (PARAFAC) model with its second-order advantage and calculate the scores and loadings.Then a multivariate linear regression (MLR) calibration model is built from the PARAFAC sample scores combined with the reference concentration values for quantification purposes.For the validation and prediction, the PARAFAC loadings are used to calculate the predicted scores with the validation and prediction data sets, and then the predicted concentration values can be deduced from the MLR model.The proposed method has been successfully applied to two NIR spectroscopy experiments.One is a Monte-Carlo simulation experiment of skin.The changes of the absorption coefficients and scattering coefficients of dermis are considered as the variations of the matrix background.The other is an in vitro experiment including glucose, haemoglobin and albumin solutions and the mixed composition solutions.The determination coefficients and root mean square error of prediction (RMSEP) values obtained from the PARAFAC-MLR models are compared with those obtained from traditional chemometrics tools such as partial least squares (PLS).The results show that the PLS model cannot handle uncalibrated variations whereas the way of introducing the matrix background to generate tensor data and the regression method based on the combination of PARAFAC and MLR perform better in model robustness and prediction precision.
Distance protection is a common line protection. The protection range and sensitivity of protection are less affected by the operation mode of the system. At the same time, distance I protection has the advantages of stable protection range and identifying the direction of short-circuit points. However, by side close to the converter station in HVDC transmission distance protection, likely because of commutation failure in DC measurement impedance add-ons with DC fault current equivalent change and change, the different fault cases caused by the additional impedance value, may is inductive or capacitive, leading to refuse or delay action distance protection. This paper builds a DC transmission model based on PSCAD /EMTDC as a simulation tool, and the simulation verification shows that when the metal-grounded transmission line in the near area of dc inverter occurs, the phase-changing failure on the inverter may cause the distance protection rejection.
One of the most important components in electrochemical storage devices (batteries and supercapacitors) is undoubtedly the electrolyte. The basic function of any electrolyte in these systems is the transport of ions between the positive and negative electrodes. In addition, electrochemical reactions occurring at each electrode/electrolyte interface are the origin of the current generated by storage devices. In other words, performances (capacity, power, efficiency and energy) of electrochemical storage devices are strongly related to the electrolyte properties, as well as, to the affinity for the electrolyte to selected electrode materials. Indeed, the formulation of electrolyte presenting good properties, such as high ionic conductivity and low viscosity, is then required to enhance the charge transfer reaction at electrode/electrolyte interface ( e.g. charge accumulation in the case of Electrochemical Double Layer Capacitor, EDLC). For practical and safety considerations, the formulation of novel electrolytes presenting a low vapor pressure, a large liquid range temperature, a good thermal and chemical stabilities is also required. This lecture will be focused on the effect of the electrolyte formulation on the performances of electrochemical storage devices (Li-ion batteries and supercapacitors). During which, a summary of the physical, thermal and electrochemical data obtained by our group, recently, on the formulation of novel electrolyte-based on the mixture of an ionic liquid (such as EmimNTf 2 and Pyr 14 NTf 2 ) and carbonate or dinitrile solvents will be presented and commented. The impact of the electrolyte formulation on the storage performances of EDLC and Li-ion batteries will be also discussed to further understand the relationship between electrolyte formulation and electrochemical performances. This talk will also be an opportunity to further discuss around the effects of additives (SEI builder: fluoroethylene carbonate and vinylene carbonate), ionic liquids, structure and nature of lithium salt (LiTFSI vs LiPF 6 ) on the cyclability of negative electrode to then enhance the electrolyte formulation. For that, our recent results on TiSnSb and graphite negative electrodes will be presented and discussed, for example 1,2 . 1-C. Marino, A. Darwiche1, N. Dupré, H.A. Wilhelm, B. Lestriez, H. Martinez, R. Dedryvère, W. Zhang, F. Ghamouss, D. Lemordant, L. Monconduit “ Study of the Electrode/Electrolyte Interface on Cycling of a Conversion Type Electrode Material in Li Batteries” J. Phys.chem. C, 2013, 117, 19302-19313 2- Mouad Dahbi, Fouad Ghamouss, Mérièm Anouti, Daniel Lemordant, François Tran-Van “Electrochemical lithiation and compatibility of graphite anode using glutaronitrile/dimethyl carbonate mixtures containing LiTFSI as electrolyte” 2013, 43, 4, 375-385.
A hydrate bed critical velocity model is developed, including a hydrate bed limit deposition velocity model and a hydrate bed suspension velocity model. The innovation of this paper is to consider the hydrate bed pressure and liquid bridge force on hydrate particles when building the limit deposition velocity model and to modify Dai's model by using hydrate experimental and simulation data when building the suspension velocity model. The hydrate bed critical velocity model is negatively correlated with the particle size and positively correlated with the pipe diameter, particle density, and particle volume fraction. The accuracy of the model is demonstrated by validation. The hydrate bed critical velocity model can be used to calculate the hydrate fixed-bed and moving-bed height under different conditions, based on which the flow pattern map of hydrate particles and the hydrate blockage risk classification method are established, which is a certain guidance to ensure the safety of hydrate flow in the pipeline.
Zirconium‐based metal‐organic frameworks (Zr‐MOFs) represent an important class of MOFs with high stability and outstanding properties, the green preparation and shaping of which are still challengeable works to hinder their real‐world applications. In this presentation, UiO‐66‐NH2 MOFs were in‐situ grown accompanied by alginate (Alg) hydrogelation under aqueous conditions, achieving UiO‐66‐NH2/Alg composite hydrogels. Relevant characterizations demonstrate the in‐situ generated UiO‐66‐NH2 MOFs were evenly distributed in hydrogel networks by attaching on Alg fiber surfaces. The network structure became denser, but both specific surface area and pore volume were augmented due to the presence of MOFs, which in turn increased active sites to interact with adsorbates. Thus, the adsorption capacity to methylene blue (MB) of composite hydrogels became higher with more dosage of MOF ligand, and the pH sensitivity of Alg adsorption to MB in the pH range of 4 to 10 was eliminated. Furthermore, the study of adsorption kinetics and isotherm reveals MB adsorption on the obtained hydrogels belong to rate controlling chemisorption mechanism. In summary, this manuscript presents a facile approach to realizing the green synthesis and shaping of Zr‐MOFs by one‐step compositing of UiO‐66‐NH2 with Alg‐based hydrogels in aqueous system, achieving MOFs‐based composite hydrogels with enhanced dye adsorption.
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