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Invariant Einstein metrics on generalized Wallach spaces
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作者 Zhiqi Chen Yurii Gennadievich Nikonorov 《中国科学:数学英文版》 SCIE CSCD 2019年第3期569-584,共16页
Invariant Einstein metrics on generalized Wallach spaces have been classified except SO(k + l+ m)/SO(k) × SO(l) × SO(m). In this paper, we first give a survey on the study of invariant Einstein metrics on ge... Invariant Einstein metrics on generalized Wallach spaces have been classified except SO(k + l+ m)/SO(k) × SO(l) × SO(m). In this paper, we first give a survey on the study of invariant Einstein metrics on generalized Wallach spaces, and prove that there are infinitely many spaces of the type SO(k + l + m)/SO(k)× SO(l) × SO(m) admitting exactly two, three, or four invariant Einstein metrics up to a homothety. 展开更多
关键词 compact HOMOGENEOUS SPACE generalized Wallach SPACE symmetric SPACE HOMOGENEOUS RIEMANNIAN METRIC EINSTEIN METRIC RICCI flow
酸催化山梨醇脱水制异山梨醇的研究进展
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作者 邓洁 袁静 +5 位作者 童琴 代卫国 赵昆峰 王耀锋 徐宝华 何丹农 《过程工程学报》 CAS CSCD 北大核心 2019年第1期25-34,共10页
异山梨醇是一种生物基功能性二元醇,近年来因其在聚合物工业中的潜在应用价值而备受关注。山梨醇脱水反应是生物质转化合成异山梨醇的关键步骤,目前普遍采用酸催化体系,且在酸性催化剂开发及工艺研究方面均取得了良好进展。本工作主要... 异山梨醇是一种生物基功能性二元醇,近年来因其在聚合物工业中的潜在应用价值而备受关注。山梨醇脱水反应是生物质转化合成异山梨醇的关键步骤,目前普遍采用酸催化体系,且在酸性催化剂开发及工艺研究方面均取得了良好进展。本工作主要介绍了已报道的酸性催化剂结构与性质对催化活性及选择性的影响,指出强酸性均相催化剂具有高催化活性,但腐蚀性强,且不易循环利用;多相催化剂催化活性与酸性位点、酸度、酸容量、孔结构、表面性质和结构等都有关系,且这些性质随催化剂组成和结构改变而相互影响。针对目前山梨醇脱水反应催化剂均相催化腐蚀性强、催化剂循环性差,多相催化剂催化活性不高的现状,高催化活性可循环使用的离子液体催化剂是一种具有发展潜力的均相催化剂,对多相催化剂构效关系还应进行更多的研究以指导新型催化剂的开发。 展开更多
关键词 异山梨醇 山梨醇 脱水 均相催化 多相催化 构效关系
Spacelike Mobius Hypersurfaces in Four Dimensional Lorentzian Space Form
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作者 Yan Bin LIN Ying LU Chang Ping WANG 《数学学报:英文版》 SCIE CSCD 2019年第4期519-536,共18页
In this paper, we first set up an alternative fundamental theory of Mobius geometry for any umbilic-free spacelike hypersurfaces in four dimensional Lorentzian space form, and prove the hypersurfaces can be determined... In this paper, we first set up an alternative fundamental theory of Mobius geometry for any umbilic-free spacelike hypersurfaces in four dimensional Lorentzian space form, and prove the hypersurfaces can be determined completely by a system consisting of a function W and a tangent frame {Ei}. Then we give a complete classification for spacelike Mobius homogeneous hypersurfaces in four dimensional Lorentzian space form. They are either M?bius equivalent to spacelike Dupin hypersurfaces or to some cylinders constructed from logarithmic curves and hyperbolic logarithmic spirals. Some of them have parallel para-Blaschke tensors with non-vanishing Mobius form. 展开更多
关键词 MOBIUS metric para-Blaschke tensor MOBIUS homogeneous HYPERSURFACE HYPERBOLIC logarithmic spiral Dupin HYPERSURFACE
氟硼二吡咯类共轭聚合物均相检测miRNA研究 预览
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作者 张江艳 赵丽坤 +2 位作者 李亚茹 张璇歌 成永强 《河北大学学报:自然科学版》 CAS 北大核心 2019年第3期247-253,共7页
基于水溶性氟硼二吡咯类共轭聚合物PBF可与长波长区(>600nm)荧光染料产生荧光共振能量转移(FRET),结合引物延伸反应,发展了一种均相检测miRNA的新方法.方法首先通过引物延伸反应在目标miRNA分子上引入荧光染料Cy5,形成miRNA-Cy5.然后... 基于水溶性氟硼二吡咯类共轭聚合物PBF可与长波长区(>600nm)荧光染料产生荧光共振能量转移(FRET),结合引物延伸反应,发展了一种均相检测miRNA的新方法.方法首先通过引物延伸反应在目标miRNA分子上引入荧光染料Cy5,形成miRNA-Cy5.然后,PBF与miRNA-Cy5/DNA杂合体通过静电力结合并发生从PBF到Cy5的有效FRET,实现了基于阳离子共轭聚合物(CCP)的长波长区miRNA的均相检测,方法灵敏度高、特异性好,测定miR-221的线性为15~6000pmol/L,检出限(3σ)为8.4pmol/L.方法拓展了CCP的应用,为基于CCP的生物传感和生化分析提供了新的均相检测平台. 展开更多
关键词 共轭聚合物 氟硼二吡咯 均相 miRNA
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CLASSFICATION OF HOMOGENEOUS TWO-SPHERES IN G(2, 5;C) 预览
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作者 张文娟 费杰 焦晓祥 《数学物理学报:B辑英文版》 SCIE CSCD 2019年第1期312-328,共17页
In this article, we determine all homogeneous two-spheres in the complex Grassmann manifold G(2, 5;C) by theory of unitary representations of the 3-dimensional special unitary group SU(2).
关键词 HOMOGENEOUS IMMERSION GAUSS CURVATURE K¨ahler angle RIGIDITY
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“一体”与“主从”:王阳明对体用关系的理解与运用 预览
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作者 龚开喻 《赣南师范大学学报》 2019年第4期108-113,共6页
从王阳明对《大学》的理解开始,逐步拓展到阳明对儒家经典、三教异同、万物一体的理解,来考察王阳明对体用关系的理解与运用,指出王阳明有两种不同的体用结构:一个是体用一源、圆融一体的同质同层的体用结构,另一个则为异质异层、既分... 从王阳明对《大学》的理解开始,逐步拓展到阳明对儒家经典、三教异同、万物一体的理解,来考察王阳明对体用关系的理解与运用,指出王阳明有两种不同的体用结构:一个是体用一源、圆融一体的同质同层的体用结构,另一个则为异质异层、既分又合、有主有从的“主——从”式的体用关系。这两种体用结构既互相相关,又存在着张力。 展开更多
关键词 王阳明 体用观 同质同层 异质异层
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Synthesis of Agomelatine by One-pot Catalytic Hydrogenation and Acetylation with NiO
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作者 YU Zhijun CHENG Zhengzai +8 位作者 XIE Cong ZENG Sheng DENG Haiying LIU Panpan HU Hai LI Guangyao DING Ling Mario Gauthier LI Shiqian 《武汉理工大学学报:材料科学英文版》 SCIE EI CAS 2019年第2期453-458,共6页
Nano-NiO and bulk NiO were prepared from Ni(AC)2·4 H2O by coordination precipitation using aqueous ammonia and by a solid state reaction, respectively. The nickel oxide particles were characterized by X-ray Diffr... Nano-NiO and bulk NiO were prepared from Ni(AC)2·4 H2O by coordination precipitation using aqueous ammonia and by a solid state reaction, respectively. The nickel oxide particles were characterized by X-ray Diffraction(XRD) and scanning electron microscopy(SEM). The results indicate that nano-sized NiO has a crystal phase with a standard face-centered cubic lattice structure, with a mean particle diameter of about 10 nm. The evaluation of the activity of nickel oxide nanoparticles in the catalytic hydrogenation of 7-methoxy-1-naphthylacetonitrile was carried out. The results demonstrate the efficient synthesis of the title compound by a one-pot catalytic hydrogenation and acetylation with NiO. The NiO nanoparticles displayed superior catalytic activity in the synthesis of agomelatine in the one-pot reaction.The total yield of agomelatine is over 81.8% with a purity of 99.2%, as determined by HPLC. The structure of agomelatine was confirmed by IR, MS, and 1 H NMR analysis. 展开更多
关键词 nano-NiO homogeneous precipitation method catalytic HYDROGENATION AGOMELATINE N-[2-(7-Methoxy-1-naphthyl)ethyl]acetamide 7-Methoxy-1-naphthylacetonitrile
中国传统文化与伊斯兰文明 预览
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作者 朱光亚 《东方论坛:青岛大学学报》 2019年第2期121-128,共8页
中国传统文化是一种入世与出世相结合的文化:儒家入世,其基本特征是拯救;道家出世,其基本特征是逍遥。出世与入世,构成了中国人的精神世界;拯救与逍遥,则凝结成中国传统文化的基本特征。作为宗教文明的伊斯兰文化,其基本属性应该是出世... 中国传统文化是一种入世与出世相结合的文化:儒家入世,其基本特征是拯救;道家出世,其基本特征是逍遥。出世与入世,构成了中国人的精神世界;拯救与逍遥,则凝结成中国传统文化的基本特征。作为宗教文明的伊斯兰文化,其基本属性应该是出世的,然其独特处在于,从产生之日起,它便是一种世俗化的体系。这种集世俗化与非世俗化于一体的伊斯兰文化,自传入中国后,就与中国传统文化天然同构,并发展成为中国传统文化的一部分。在这个意义上,中国的伊斯兰文化是“中国的”文化,而非“世界的”文化。 展开更多
关键词 传统文化 伊斯兰文化 传播 融合 同构
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Time-crystal ground state and production of gravitational waves from QCD phase transition
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作者 Andrea Addazi Antonino Marcianò Roman Pasechnik 《中国物理C:英文版》 SCIE CAS CSCD 2019年第6期115-125,共11页
We propose a novel mechanism for the production of gravitational waves in the early Universe that originates from the relaxation processes induced by the QCD phase transition. While the energy density of the quark-glu... We propose a novel mechanism for the production of gravitational waves in the early Universe that originates from the relaxation processes induced by the QCD phase transition. While the energy density of the quark-gluon mean-field is monotonously decaying in real time, its pressure undergoes a series of violent oscillations at the characteristic QCD time scales that generate a primordial multi-peaked gravitational waves signal in the radio frequencies’ domain. The signal is an echo of the QCD phase transition that is accessible by planned measurements at the FAST and SKA telescopes. 展开更多
关键词 primordial GRAVITATIONAL waves HOMOGENEOUS GLUON CONDENSATE effective YANG-MILLS theory QCD phase tran sition
High-Effi ciency Preparation of 2,5-Diformylfuran with a Keto-ABNO Catalyst Under Mild Conditions 预览
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作者 Le Li Yuefei Wang +2 位作者 Wei Qi Rongxin Su Zhimin He 《天津大学学报:英文版》 EI CAS 2019年第2期118-123,共6页
In this paper, we report a new catalytic system for realizing the rapid and effi cient oxidation of 5-hydroxymethylfurfural (HMF). First, we used 9-azabicyclo [3.3.1]nonan-3-one-N-oxyl (keto-ABNO) as a catalyst for th... In this paper, we report a new catalytic system for realizing the rapid and effi cient oxidation of 5-hydroxymethylfurfural (HMF). First, we used 9-azabicyclo [3.3.1]nonan-3-one-N-oxyl (keto-ABNO) as a catalyst for the aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) in acetic acid. Then, we systematically studied the important reaction parameters, including the solvent, co-catalyst, and temperature. The results demonstrate that the acidic solvent used is crucial for the effi cient oxidation of HMF to DFF. Under optimal conditions, we achieved a 93.4% yield of DFF within half an hour at room temperature. We also proposed the possible mechanism for this system. 展开更多
关键词 BIOMASS 5-HYDROXYMETHYLFURFURAL 2 5-Diformylfuran 9-Azabicyclo[3.3.1]nonan-3-one-N-oxyl HOMOGENEOUS CATALYSIS
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On the thixotropic effect of turbulence 预览
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作者 Yu-Ning Huang 《力学快报:英文版》 CAS CSCD 2019年第2期113-119,共7页
As a follow-up research of the work on the natural viscosity of turbulence of Huang et al.[Journal of Turbulence (2003)], here we investigate the thixotropic effect of a turbulent Newtonian fluid on the basis of the e... As a follow-up research of the work on the natural viscosity of turbulence of Huang et al.[Journal of Turbulence (2003)], here we investigate the thixotropic effect of a turbulent Newtonian fluid on the basis of the ensemble-averaged Navier–Stokes equation. In view of the natural viscosity, we show that in homogeneous isotropic turbulence the turbulent Newtonian fluid behaves like a thixotropic fluid, exhibiting the thixotropic effect with its natural viscosity decreasing with time. 展开更多
关键词 SECOND-ORDER CLOSURE Natural viscosity of TURBULENCE Launder Reece and Rodi model Homogeneous ISOTROPIC TURBULENCE THIXOTROPY
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Numerical simulation of particle formation and evolution in a vehicle exhaust plume using the bimodal Taylor expansion method of moments
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作者 Shuyuan Liu Tat Leung Chan Huijie Liu 《中国颗粒学报:英文版》 SCIE EI CAS CSCD 2019年第2期46-55,共10页
The bimodal Taylor expa nsion method of moments (B-TEMOM) model scheme was developed to simulate the formation and evolution of vehicle exhaust particles. Two independent types of log-normal particle size distribution... The bimodal Taylor expa nsion method of moments (B-TEMOM) model scheme was developed to simulate the formation and evolution of vehicle exhaust particles. Two independent types of log-normal particle size distributions were selected in the B-TEMOM model scheme, comprising large and small particles to represent background (i.e., the surrounding environment) and vehicle exhaust particles, respectively. Concentration distributions of exhaust and background particles derived using this model scheme were verified against results from a moving secti onal method and the bimodal quadrature method of moments, showing excellent agreement. The effects of vehicle tailpipe ex 让 cond 让 ions (e.g., exhaust particle concentrations and velocity), sulfurcontent, and relative humidity on the evoluti on of particles were investigated numerically. Both two-dimensional and three-dimensional numerical simulations showed that tailpipe exit velocity and relative humid让y did not greatly affect the steady-state concentrations or the diameters of particles in urban atmospheres. Although an increase in sulfur content had little effect on the particle concentration, it led to background particles with larger geometric average diameter entering the environment. This coupled CFD-B-TEMOM numerical model provides a simple but accurate and efficient method for studying bimodal aerosol dynamics. 展开更多
关键词 VEHICLE exhaust particles BIMODAL Taylor expansi on method of MOMENTS Homogeneous NUCLEATION COAGULATION Tailpipe EXIT velocity Sulfur content and ambient relative humidity
Degradation of benzothiophene in diesel oil by LaZnAl layered double hydroxide: photocatalytic performance and mechanism
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作者 Li-Guo Gao Huan-Xiang Li +2 位作者 Xiao-Li Song Wan-Lu Li Xiang-Rong Ma 《石油科学:英文版》 SCIE CAS CSCD 2019年第1期173-179,共7页
A new type of photocatalytic La^3+-Zn^2+-Al^3+-MoO4^2- layered double hydroxide (LDH) material (molar ratio, La/Zn/ Al = 1:7:2) was prepared by a complexing agent-assisted homogeneous precipitation technique. The stru... A new type of photocatalytic La^3+-Zn^2+-Al^3+-MoO4^2- layered double hydroxide (LDH) material (molar ratio, La/Zn/ Al = 1:7:2) was prepared by a complexing agent-assisted homogeneous precipitation technique. The structure of the prepared LDH material was systematically studied. Under UV irradiation, the desulfurization efficiency of the LDH material was 87% in 2 h. For La^3+-Zn^2+-A1^3+-MoO4^2- LDH material, the introduction of MoO42_ increased the interlayer space for promoting the adsorption of benzothiophene (BT), and MoO4^2- might provide active sites for the oxidation of BT, resulting in the high desulfurization efficiency. 展开更多
关键词 LDH HOMOGENEOUS precipitation PHOTOCATALYTIC activities CATALYTIC OXIDATION MECHANISM
Boundedness and continuity of Marcinkiewicz integrals associated to homogeneous mappings on Triebel-Lizorkin spaces
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作者 Feng LIU Zunwei FU Seong Tae JHANG 《中国数学前沿:英文版》 SCIE CSCD 2019年第1期95-122,共28页
We establish the boundedness and continuity of parametric Marcinkiewicz integrals associated to homogeneous compound mappings on Triebel-Lizorkin spaces and Besov spaces. Here the integral kernels are provided with so... We establish the boundedness and continuity of parametric Marcinkiewicz integrals associated to homogeneous compound mappings on Triebel-Lizorkin spaces and Besov spaces. Here the integral kernels are provided with some rather weak size conditions on the unit sphere and in the radial direction. Some known results are naturally improved and extended to the rough case. 展开更多
关键词 Parametric MARCINKIEWICZ integral HOMOGENEOUS mapping Triebel- Lizorkin SPACE BESOV SPACE
Preparation, morphology and luminescence properties of Gd2O2S:Tb with different Gd2O3 raw materials
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作者 Yu-Jie Ding Peng-De Han +1 位作者 Li-Xi Wang Qi-Tu Zhang 《稀有金属:英文版》 SCIE EI CAS CSCD 2019年第3期221-226,共6页
The sulfide fusion method was used to synthesize Gd2 O2 S:Tb phosphors using commercial Gd2 O3 and freshly prepared Gd2 O3, respectively. The freshly prepared Gd2 O3 was synthesized from Gd2 O(GO3)2·H2 O precurso... The sulfide fusion method was used to synthesize Gd2 O2 S:Tb phosphors using commercial Gd2 O3 and freshly prepared Gd2 O3, respectively. The freshly prepared Gd2 O3 was synthesized from Gd2 O(GO3)2·H2 O precursor prepared by homogeneous precipitation method.The structure and morphology of the composites were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS). The result shows that the Gd2 O2 S:Tb phosphor prepared by commercial Gd2 O3(GOST-A) presents agglomerated particles with average particle size of2.1 μm;however, Gd2 O2 S:Tb produced from as-prepared Gd2 O3(GOST-B) tends to form regular hexagon particles with the average particle size of 1 μm. Furthermore, Gd3+and Tb3+ contents in GOST-B are higher than that in GOST-A. In addition, fluorescent properties were analyzed by fluorescent spectrophotometer. It is indicated that similar excitation and emission spectra can be obtained from the two phosphors, but the luminescence intensity of GOST-B is higher than that of GOST-A. 展开更多
关键词 PRECURSOR PHOSPHOR LUMINESCENCE Homogeneous precipitation SULFIDE fusion
New Calderón reproducing formulae with exponential decay on spaces of homogeneous type
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作者 Ziyi He Liguang Liu +1 位作者 Dachun Yang Wen Yuan 《中国科学:数学英文版》 SCIE CSCD 2019年第2期283-350,共68页
Assume that(X,d,μ) is a space of homogeneous type in the sense of Coifman and Weiss(1971,1977). In this article, motivated by the breakthrough work of Auscher and Hyt(o|¨)nen(2013) on orthonormal bases of regula... Assume that(X,d,μ) is a space of homogeneous type in the sense of Coifman and Weiss(1971,1977). In this article, motivated by the breakthrough work of Auscher and Hyt(o|¨)nen(2013) on orthonormal bases of regular wavelets on spaces of homogeneous type, we introduce a new kind of approximations of the identity with exponential decay(for short, exp-ATI). Via such an exp-ATI, motivated by another creative idea of Han et al.(2018) to merge the aforementioned orthonormal bases of regular wavelets into the frame of the existed distributional theory on spaces of homogeneous type, we establish the homogeneous continuous/discrete Calderón reproducing formulae on(X, d,μ), as well as their inhomogeneous counterparts. The novelty of this article exists in that d is only assumed to be a quasi-metric and the underlying measure μ a doubling measure,not necessary to satisfy the reverse doubling condition. It is well known that Calderón reproducing formulae are the cornerstone to develop analysis and, especially, harmonic analysis on spaces of homogeneous type. 展开更多
关键词 SPACE of HOMOGENEOUS type Calderón reproducing formula APPROXIMATION of the IDENTITY wavelet SPACE of test functions distribution
Applying resolved-scale linearly forced isotropic turbulence in rational subgrid-scale modeling 预览
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作者 Chuhan Wang Mingwei Ge 《力学学报:英文版》 SCIE EI CAS CSCD 2019年第3期486-494,共9页
In previous attempts of rational subgrid-scale (SGS) modeling by employing the Kolmogorov equation of filtered (KEF) quantities, it was necessary to assume that the resolved-scale second-order structure function is st... In previous attempts of rational subgrid-scale (SGS) modeling by employing the Kolmogorov equation of filtered (KEF) quantities, it was necessary to assume that the resolved-scale second-order structure function is stationary. Forced isotropic turbulence is often used as a framework for establishing and validating such SGS models based on stationary restrictions, for it generates statistical stationary samples. However, traditional forcing method at low wavenumbers cannot provide an analytic form of forcing term for a complete KEF in physical space, which has been illustrated to be essential in the modeling of such SGS models. Thus, an alternative forcing method giving an analytic forcing term in physical space is needed for rational SGS modeling. Giving an analytic linear driving term in physical space, linearly forced isotropic turbulence should be considered an ideal theoretical framework for rational SGS modeling. In this paper, we demonstrate the feasibility of establishing a rational SGS model with stationary restriction based on linearly forced isotropic turbulence. The performance of this rational SGS model is validated. We, therefore, propose the use of linearly forced isotropic turbulence as a complement to free-decaying isotropic turbulence and low-wavenumber forced isotropic turbulence for SGS model validations. 展开更多
关键词 Homogeneous isotropic TURBULENCE Large-eddy simulation SUBGRID-SCALE model FORCED TURBULENCE
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“追求卓越”的教育隐忧及理性化解 预览
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作者 曹永国 《河南师范大学学报:哲学社会科学版》 CSSCI 北大核心 2019年第3期149-156,共8页
追求卓越需要思考何为卓越,卓越意味着什么,认真面对思想家对于教育追求卓越的反思与批判。追求卓越的教育隐忧在于容易按照某种标准将学生划分等级,从而加剧同质化的恶性竞争。其现实后果可能会增强培养中的功利主义和工具主义取向,并... 追求卓越需要思考何为卓越,卓越意味着什么,认真面对思想家对于教育追求卓越的反思与批判。追求卓越的教育隐忧在于容易按照某种标准将学生划分等级,从而加剧同质化的恶性竞争。其现实后果可能会增强培养中的功利主义和工具主义取向,并容易形成心灵的一种偏见和骄傲。基于一种理性的考虑,追求卓越的教育需要以发展多元化教育为前提,以培养心灵的谦卑为基础,以尊重人为原则,承认并接受个人之不足,自觉培养勇于担当之社会责任感。 展开更多
关键词 卓越 隐忧 同质化 功利主义 复杂性
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箱型截面齐次广义屈服函数的数值拟合及极限承载力分析 预览 被引量:1
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作者 张逸 欧伟 +1 位作者 周强 张伟 《钢结构》 2018年第3期44-49,103共7页
推导了箱型截面全截面屈服时轴力和弯矩之间的隐式相关关系,揭示了影响相关关系的2个考虑厚度的无量纲几何参数及其影响规律,据此通过数值拟合建立了箱形截面的齐次广义屈服函数,给出了常用箱型截面齐次广义屈服函数待定系数表,进而结... 推导了箱型截面全截面屈服时轴力和弯矩之间的隐式相关关系,揭示了影响相关关系的2个考虑厚度的无量纲几何参数及其影响规律,据此通过数值拟合建立了箱形截面的齐次广义屈服函数,给出了常用箱型截面齐次广义屈服函数待定系数表,进而结合数值齐次广义屈服函数和弹性模量缩减法,提出了箱型结构的极限承载力分析方法,克服了原广义屈服函数参数选取不合理、齐次广义屈服函数式通用性差、结构极限承载力计算精度欠佳等问题。算例分析表明,采用此方法求解结构极限承载力具有良好的计算精度、计算效率和迭代稳定性。 展开更多
关键词 箱型截面 广义屈服函数 齐次化 数值拟合 无量纲几何参数 极限承载力
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Preparation and characterization of high softening point and homogeneous isotropic pitches produced from distilled ethylene tar by a novel bromination method 预览
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《新型炭材料》 CSCD 北大核心 2018年第1期97-100,共4页
关键词 high SOFTENING point and HOMOGENEOUS ISOTROPIC pitches PRODUCED from distilled ethylene tar romination METHOD
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