Conservation laws can be derived from field equations?

Charge conservation law ($\partial_{\beta} J^\beta =0$) usually is considered as a corollary of Maxwell's equations. A circular reasoning, however, is found in the derivation. A similar fallacy exists in the matter source's conservation law ($\nabla^{\mu}T_{\mu\nu}=0$) and Einstein's field equations. Therefore, the source's conservation laws are NOT consequence of field equations.Comment: 2 page

Supervision Timing Simulation Analysis of Community E-commerce Platform Supply Chain Based on Tripartite Game Model

With the development of network and the popularity of e-commerce, the network service industry has shown strong development potential, and many community e-commerce platforms have emerged as the times require. In order to ensure the profit of the supply chain of community e-commerce platform and supervise whether the suppliers of enterprises and grid station service providers try their best to participate in value co-creation, this paper introduces the delay parameter a of community e-commerce platform, constructs a three-party evolutionary game model of "community e-commerce platform-grid station service provider-supplier", simulates the strategies of each agent with matlab, studies the behaviours of community e-commerce platform under different delay parameters, and concludes that the delay parameter a of community e-commerce platform has a great influence on the timing of community e-commerce platform supervision. Finally, three suggestions are put forward for the supervision of the supply chain of community e-commerce platform: (1) encourage consumers to report; (2) formulate the reward and punishment system for the settled enterprises; (3) formulating a reasonable supervision system

Finite Element Modelling Of Tensile Test For Micro-Alloyed Low Carbon Steel At High Temperature

International audienceIn view of the numerical inverse identification of constitutive models, a forward numerical modelling of Gleeble tension tests is conducted. A coupled electrical--thermal--mechanical model is proposed for the resolution of electrical, energy and momentum conservation equations by means of finite element method. In momentum equation, the mixed rheological model in multi--phase region (e.g. δ--ferrite and γ austenite (δ+γ mixture)) is developed to consider the δ/γ phase transformation phenomenon for micro--alloyed low carbon steel at high temperature. Experimental and numerical results reveal that significant thermal gradients exist in specimen along longitudinal and radial directions. Such thermal gradients will lead to phase fraction gradient in specimen at high temperature, such as δ fraction gradient or liquid fraction gradient. All these gradients will contribute to the heterogeneous deformation of specimen and severe stress non--uniform distribution, which is the major difficulty for the identification of constitutive models, especially for the simple identification method based on nominal stress--strain. The proposed model can be viewed as an important achievement for further inverse identification methods, which should be used to identify constitutive parameters for steel at high temperature in the presence of thermal gradients

Inverse finite element modelling and identification of constitutive parameters of UHS steel based on Gleeble tensile tests at high temperature

The authors are grateful to the publisher, Taylor & Francis, for letting the manuscript being archived in this Open Access repository. This is an electronic version of an article that was published in Inverse Problems in Science and Engineering© 2011 Copyright: Taylor & Francis. Inverse Problems in Science and Engineering is available online at: http://www.tandfonline.com/doi/abs/10.1080/17415977.2010.518288International audienceThe rheological behaviour of an ultra high strength (UHS) steel is investigated by Gleeble tensile tests at low-deformation rates and high temperature, from 1200°C to solidus temperature. Results show that large thermal gradients exist in specimens, resulting in heterogeneous deformation, which makes the identification of constitutive parameters difficult from the directly deduced nominal stress-strain curves. The advantages of an inverse identification method - associating a direct finite element model of Gleeble tests and an optimization module - are demonstrated in such conditions. The constitutive parameters identified by this technique have been successfully applied to additional tests, more complex in nature than those used for the identification of parameters. However, such tests combining successive loading and relaxation stages have revealed some limitations of the considered constitutive model

Simultaneous Determination of Copper, Lead, and Cadmium at Hexagonal Mesoporous Silica Immobilized Quercetin Modified Carbon Paste Electrode

A new method was developed for simultaneous determination of copper, lead, and cadmium, based on their voltammetric response at a carbon paste electrode modified with hexagonal mesoporous silica (HMS) immobilized quercetin (HMS-Qu/CPE). Compared with quercetin modified carbon paste electrode (Qu/CPE) and quercetin ionic liquid modified carbon paste electrode (Qu-IL/CPE), the HMS-Qu/CPE exhibited improved selectivity and high sensitivity toward the detection of copper, lead, and cadmium. The properties of the HMS-Qu/CPE in 0.1 M HCOONa-HCl buffer solution (pH4.7) were investigated by adsorptive stripping voltammetry (ASV) and electrochemical impedance spectroscopy (EIS). The electrochemical behavior of copper, lead, and cadmium at the modified electrodes and factors affecting the preconcentration procedures were also investigated. Detection limits of 5.0, 0.8, 1.0 nM for copper, lead, and cadmium were obtained, respectively. The method is simple, fast, sensitive, and selective, and is successfully applied to soil sample