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Designing nonlinear thermal devices and metamaterials under the Fourier law: A route to nonlinear thermotics

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Frontiers of physics 2021年第5期16卷 107-142页

作者： Gao-le Dai School of Sciences Nantong UniversityNantong226019China

Nonlinear heat transfer can be exploited to reveal novel transport phenomena and thus enhance people’s ability to manipulate heat flux at ***,there has not been a mature discipline called nonlinear thermotics like its counterpart in optics or acoustics to make a systematic summary of relevant *** the current review,we focus on recent progress in an important part of nonlinear heat transfer,i.e.,tailoring nonlinear thermal devices and metamaterials under the Fourier law,especially with temperature-dependent thermal *** will present the basic designing techniques including solving the equation directly and the transformation *** nonlinearity coming from multi-physical effects,and how to calculate effective properties of nonlinear conductive composites using the effective medium theory are also *** on these theories,researchers have successfully designed various functional materials and devices such as the thermal diodes,thermal transistors,thermal memory elements,energy-free thermostats,and intelligent thermal materials,and some of them have also been realized in ***,these phenomenological works can provide a feasible route for the development of nonlinear thermotics.

关键词： nonlinear thermotics thermal metamaterials thermal conduction thermal radiation thermal convection thermo-mechanical effects effective medium theory

HANDEL'S FIXED POINT THEOREM:A MORSE THEORETICAL POINT OF VIEW

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Acta Mathematica Scientia 2021年第6期41卷 2149-2172页

作者： Patrice le CALVEZ Institut de Mathématiques de Jussieu-Paris Rive Gauche IMJ-PRGSorbonne UniversitéUniversitéParis-DiderotCNRSF-75005ParisFrance Institut Universitaire de France ParisFrance

Michael Handel has proved in [10] a fixed point theorem for an orientation preserving homeomorphism of the open unit disk, that turned out to be an efficient tool in the study of the dynamics of surface homeomorphisms. The present article fits into a series of articles by the author [13] and by Juliana Xavier [21, 22], where proofs were given, related to the classical Brouwer Theory, instead of the Homotopical Brouwer Theory used in the original article. Like in [13, 21] and [22], we will use “free brick decompositions” but will present a more conceptual Morse theoretical argument. It is based on a new preliminary lemma, that gives a nice “condition at infinity” for our problem.

关键词： brick decomposition Brouwer theory translation arc

Extraction of full energy peak of ^(137)Cs from in situ NaI(Tl)gamma-ray spectrum

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Nuclear Science and Techniques 2016年第4期27卷 53-59页

作者： le-le Zhang Nan-Ping Wang Bao-Chuan Li School of Geophysics and Information Technology China University of Geosciences

A levenberg–Marquardt Gaussian fitting algorithm has been used for analyzing the overlap of three peaks(the 583-ke V peak of^(208)Tl, the 609-ke V peak of214 Bi, and the 662-ke V peak of^(137)Cs) using an in situ Na I(Tl) scintillation spectrometer. The algorithm, in addition,was compared with a genetic algorithm used for multiple deconvolution. The three fitted peak areas(583, 609, and662 ke V) were calculated from the measured gamma-ray spectra obtained from a simulation experiment in which a^(137) Cs source was buried at different soil depths(from 18 to38 cm). The application of the levenberg–Marquardt algorithm yielded similar results compared to the genetic algorithm. A lack-of-fit test showed that the fitting is good when the instrumental noise levels were estimated from replicated analyses. The relative fitting error of the total net area and the residual standard deviation were within 5 %and 0.04, respectively, and the goodness of the fitting was better than 0.98. While the methods used in this paper give high performance, the results may lead to incorrect estimation when the signal-to-noise ratio is smaller than-30 d B. This study is useful for the determination of radioactive specific activity of^(137) Cs by in situ spectrometry.

关键词： 137Cs γ射线谱 Marquardt算法全能峰 Gaussian 拟合算法提取相对拟合误差

Nanosheet-structured B4C with high hardness up to 42 GPa

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Chinese Physics B 2019年第6期28卷 313-316页

作者： Chang-Chun Wang le-le Song College of Science Jilin Institute of Chemical TechnologyJilin 132022China Institute of Atomic and Molecular Physics Jilin UniversityChangchun 130012China

High-quality bulk boron carbide(B4C) is successfully prepared at high pressure and high temperature(HPHT) by using B4C powder as a precursor. The as-synthesized B4C possesses a nanosheet structure with a thickness value of 15 nm and a length of several dozen micrometers. Its Vickers hardness value and fracture toughness value are 42.4 GPa and4.51 MPa·m1/2, respectively, which are superior to those of B4 C obtained from spark plasma sintering due to its high densification and nanosheet structure. Additionally, it shows good property of oxidation resistance. In air, its oxidation resistance temperature is 1100?C which is higher than that of diamond under the same test condition.

关键词： boron carbide hardness fracture toughness oxidation resistance

Protective effect of Tetracera scandens *** extract against CCl_4-induced acute liver injury in rats

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Asian Pacific Journal of Tropical Biomedicine 2015年第3期5卷 221-227页

作者： Tung Bui Thanh Hai Nguyen Thanh Hue Pham Thi minh Huong le-Thi-Thu Huong Duong Thi Ly Loi Vu Duc School of Medicine and Pharmacy Vietnam National University Hanoi University of Pharmacy

Objective:To investigate the protective potential of ethanolic extracts of Tetracera scandens L.(***) against CCl_4 induced oxidative stress in liver ***:Dried leaf powder of *** was extracted with ethanol and concentrated to yield a dry *** were administered with 100 mg/kg of ethanolic extracts orally once daily for one *** were subsequently administered with a single dose of CCl_4(I mL/kg body weight,intraperitoneal injection).Various assays,such as serum levels of alanine aminotransferase,aspartate aminotransferase,lipid peroxidation,protein oxidation(carbonyl protein group),tumor necrosis factor alpha,catalase,superoxide dismutase,and glutathione peroxidase,were used to assess damage caused by CCl_4 and the protective effects of the ethanol extract on liver ***:Hepatotoxicity induced by CCl_4 was evidenced by a significant increase in serum aspartate aminotransferase and alanine aminotransferase level,lipid peroxidation,protein carbonyl group,and tumor necrosis factor alpha,as well as decreased activity of the hepatic antioxidant enzymes(*** *** glutathione peroxidase).Treatment with ethanolic *** extracts prevented all of these typically observed changes in CCl_4-treated ***:Our findings indicate that *** has a significant protective effect against CCl_4 induced hepatotoxicity in *** may be due to its antioxidant properties.

关键词： Tetracera scandens L Antioxidant Carbon tetrachloride Liver toxicity Lipid peroxidation

A possible new family of unconventional high temperature superconductors

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Science Bulletin 2017年第3期62卷 212-217页

作者： Jiangping Hu Congcong le Beijing Notional Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences Beijing 100190 China Collaborative Innovation Center of Quantum Matter Beijing 100871 China School of Physics University of Chinese Academy of Sdences Beijing 100049 China

We suggest a new family of Co[Ni-based materials that may host unconventional high temperature superconductivity （high-To）. These materials carry layered square lattices with each layer being formed by vertex-shared transition metal tetrahedra cation-anion complexes. The electronic physics in these materials is determined by the two dimensional layer and is fully attributed to the three near degenerated t2g d-orbitals close to a d7 filling configuration in the d-shell of CoJNi atoms. The electronic structure meets the necessary criteria for unconventional high Tc materials proposed recently by us to unify the two known high-Tc families, cuprates and iron-based superconductors. We predict that they host superconducting states with a d-wave pairing symmetry with Tc potentially higher than those of iron-based superconductors. These materials, if realized, can be a fertile new ground to study strongly correlated electronic Physics and provide decisive evidence for superconducting pairing mechanism.

关键词： Iron-based superconductors Cuprates d-Wave pairing symmetry Cobalt chalcogenides

A Novel Recognition Method for Low SNR DSSS Signals Based on Four-Order Cumulant and Eigenvalue Analysis

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Chinese Journal of Electronics 2015年第3期24卷 648-653页

作者： GUAN Mingxiang WANG le School of Electronic and Communication Shenzhen Institute of Information Technology

At present it is very difficult to estimate the carrier frequency, spread spectrum code period and spread spectrum code pattern of Direct sequence spread spectrum(DSSS) signals with low Signal-to-noise ratio(SNR) accurately and simultaneously in the condition of Gaussian white noise. A novel method of estimation for carrier frequency and spread spectrum code period of DSSS signals based on four-order cumulant and eigenvalue analysis is presented. Compared with the correlative detection in time domain, square filtering detection and Hebbian rule, the proposal method in this study can realize the estimation for the carrier frequency and period of spread spectrum code of low SNR DSSS signals with a high accuracy simultaneously. In a priori condition of the spread spectrum code period the proposal method can calculate synchronization loss time between spread spectrum code and information symbol. The proposal method this paper has a strong ability to suppress Gaussian noise.

关键词： DSSS Low signal to noise ratio Recognition Four-order cumulant Eigenvalue analysis

A closure model on velocity structure functions in homogeneous isotropic turbulence

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Applied Mathematics and Mechanics(English Edition) 2017年第11期38卷 1627-1634页

作者： le FANG Feng GAO Laboratory of Mathematics and Physics Ecole Centrale de Pekin Beihang University Beijing 100191 China Co-Innovation Center for Advanced Aero-Engine Beihang University Beijing 100191 China Faculty of Engineering and Physical Sciences University of Surrey Guildford GU2 7XH U. K.

Closure models started from Chou＇s work have been developed for more than 70 years, aiming at providing analytical tools to describe turbulent flows in the spectral space. In this study, a preliminary attempt is presented to introduce a closure model in the physical space, using the velocity structure functions as key parameters. The present closure model appears to qualitatively reproduce the asymptotic scaling behav- iors at small and large scales, despite some inappropriate behaviors such as oscillations. Therefore, further improvements of the present model are expected to provide appropriate descriptions of turbulent flows in the physical space.

关键词： homogeneous isotropic turbulence closure model structure function

A Novel Method for the Fabrication of Granular Hydroxyapatite-bentonite Composite Adsorbents for the Removal of Pb2＋ from an Aqueous Solution

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Journal of Environmental Science and Engineering(B) 2016年第7期5卷 371-378页

作者： Thiminh Hieu Do Pham ThanhThao Tran AnhKhoaTon minh Vien le Department of Inorganic Chemical Engineering Ho Chi Minh City University of Technology Ho Chi Minh City 70000 Vietnam

Granular HApB composite adsorbents, with dimensions of 4 mm × 4 mm, were prepared for the removal of lead from an aqueous solution. The effectiveness of the composites for Pb2＋ removal from an aqueous solution with different initial concentrations, adsorbent doses and reaction times were examined. The Langmuir isotherms, Freundlich isotherm models and pseudo-second order kinetic model were used in this analysis. It was found that the Langmuir model fitted the experimental data better than the Freundlich model, with a maximum adsorption capacity of 93.37 mg.g-1. The pseudo-second order kinetic model also fit the experiment data well with an adsorption capacity of 70.73 mg.g-1 after being reused for 3 times. Furthermore, the composites may possibly be used in processes for industrial water treatment.

关键词： Environment afforestation poplar plantations timber marketing.