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Buckling and Post-buckling of Sandwich Plate with Functionally Graded Graphene Origami Reinforced Core Layer in Hygrothermal Environment 带功能分级石墨烯折纸增强芯层的三明治板在湿热环境下的屈曲和后屈曲
Pub Date : 2023-12-23 DOI: 10.25073/2588-1124/vnumap.4866
Vu Minh Anh, Ngo Dinh Dat, Nguyen Dinh Duc
The buckling and post-buckling of magneto-electric-elastic (MEE) sandwich plate are presented. The core layer consists of epoxy matrix reinforced with graphene origami auxetic metal-material in which the volume fraction of graphene origami is assumed to vary the thickness direction in three different distributions. For MEE face sheets, the proportions of ferroelectric and ferromagnetic components are chosen equally. The Reddy's higher order shear deformation plate theory forms the basis for establishing the governing equations. The axial compressive loading- deflection amplitude relation and the expression of critical buckling loading are obtained through the application of Galerkin method. The method's accuracy is validated by comparing its results with those published by other authors. The influences of various parameters on the buckling and post-buckling of the sandwich plate are investigated in details.
本文介绍了磁电弹性(MEE)夹层板的屈曲和后屈曲。核心层由环氧基体和石墨烯折纸辅助金属材料组成,其中石墨烯折纸的体积分数假定随厚度方向变化,有三种不同的分布。对于 MEE 面片,铁电和铁磁成分的比例选择相同。雷迪高阶剪切变形板理论是建立控制方程的基础。应用 Galerkin 方法得到了轴向压缩载荷-挠度振幅关系和临界屈曲载荷表达式。通过将该方法的结果与其他作者发表的结果进行比较,验证了该方法的准确性。详细研究了各种参数对夹层板屈曲和后屈曲的影响。
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引用次数: 0
Nonlinear Vibration of Function Graded Magneto-electro-elastic Microplates using Nonlocal Stress Theory 利用非局部应力理论研究功能分级磁电弹性微板的非线性振动
Pub Date : 2023-12-23 DOI: 10.25073/2588-1124/vnumap.4858
Ngo Dinh Dat, Nguyen Dinh Duc
This work presents an analysis of nonlinear vibration in Function Graded Magneto-Electro-Elastic (FG-MEE) plates subjected to mechanical, electrical, and magnetic loads using the nonlocal stress theory approach. In this study two types of MEE plates, namely BaTiO3 and CoFe2O4 were considered. The basic equations are derived using classical plate theory with nonlocal stress theory and are solved using the Galerkin method and Runge-Kutta method. We investigated the effects of nonlocal parameters, materials, and geometrical characteristics on the natural frequencies and nonlinear vibration of the FG-MEE microplates.
本研究采用非局部应力理论方法,对承受机械、电和磁载荷的功能分级磁电弹性(FG-MEE)板的非线性振动进行了分析。本研究考虑了两种类型的 MEE 板,即 BaTiO3 和 CoFe2O4。利用经典板理论和非局部应力理论推导出基本方程,并使用 Galerkin 方法和 Runge-Kutta 方法进行求解。我们研究了非局部参数、材料和几何特性对 FG-MEE 微板固有频率和非线性振动的影响。
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引用次数: 0
Numerical Investigation of Optical Properties in Carbon Tetrachloride-Filled Photonic Crystal Fibers 四氯化碳填充光子晶体光纤中光学特性的数值研究
Pub Date : 2023-12-23 DOI: 10.25073/2588-1124/vnumap.4850
Nguyen Thi Thuy, Nguyen Thi Oanh
In this work, we design circular lattice photonic crystal fibers using Lumerical Mode Solution software, its hollow core filled with carbon tetrachloride. Optical properties including effective refractive index, chromatic dispersion, nonlinearity, and fiber loss were investigated numerically in detail based on solving Maxwell's wave equations. The small effective mode areas of only a few µm2, and confinement loss as low as 14.799 dB/m at specific pump wavelengths were obtained. It was found that near-zero ultra-flattened chromatic dispersion with fluctuations of ±0.44 ps/nm.km spans from 1300 to 1830 nm. Three photonic crystal fibers with optimal structure and features were suggested for broadband supercontinuum generation orientation.
在这项工作中,我们使用 Lumerical Mode Solution 软件设计了圆晶格光子晶体光纤,其空心内芯填充了四氯化碳。在求解麦克斯韦波方程的基础上,对包括有效折射率、色散、非线性和光纤损耗在内的光学特性进行了详细的数值研究。结果表明,在特定的泵浦波长下,光纤的有效模式面积很小,仅为几微米2 ,禁锢损耗低至 14.799 dB/m。研究发现,1300 至 1830 nm 波长范围内的超扁平色度色散接近零,波动范围为 ±0.44 ps/nm.km。为宽带超连续发生定向提出了三种具有最佳结构和特性的光子晶体光纤。
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引用次数: 0
Interface of Two-component Bose-Einstein Condensates in Double-parabola Approximation 双抛物线近似中的双组分玻色-爱因斯坦凝结物界面
Pub Date : 2023-12-23 DOI: 10.25073/2588-1124/vnumap.4856
Nguyen Van Thu
In this work we proposed a simple method to determine the coordinate of interface of two-component Bose-Einstein condensates (BECs) in double parabola approximation (DPA). Based on this idea, the static properties of BECs have been investigated totally in DPA
在这项工作中,我们提出了一种在双抛物线近似(DPA)中确定双组分玻色-爱因斯坦凝聚体(BECs)界面坐标的简单方法。基于这一想法,我们在 DPA 中完全研究了 BEC 的静态特性。
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引用次数: 0
Characterizations of Cr3+- doped SnO2 Powders Via a Hydrolysis Method 通过水解法分析掺杂 Cr3+- 的二氧化锡粉末的特性
Pub Date : 2023-12-23 DOI: 10.25073/2588-1124/vnumap.4845
Trinh Thi Loan, Vu Hoang Huong
In this work, the effect of annealing temperature and Cr3+ concentration on the structural and optical properties of the SnO2 host crystals has been investigated. The Cr-doped SnO2 samples were synthesized by a simple hydrolysis method, using SnCl4.5H2O as the host precursor and CrCl3.6H2O as the source of dopant. X-ray diffraction and Raman scattering spectra analysis revealed a tetragonal rutile structure of Cr3+-doped SnO2 samples. The Cr3+ concentration and annealing temperature have no influence on the lattice parameters of the SnO2 crystals, whereas affected the appearance and intensity of the Raman modes. The optical properties of the synthesized samples were explored by photoluminescence (PL) and photoluminescence excitation (PLE) analysis. Interestingly, besides the emission peaks related to the SnO2, emission transitions within Cr3+ ions in the octahedral field of SnO2 were observed.
本文研究了退火温度和 Cr3+ 浓度对 SnO2 主晶结构和光学性质的影响。以 SnCl4.5H2O 为宿主前驱体,CrCl3.6H2O 为掺杂源,通过简单的水解法合成了掺杂 Cr 的 SnO2 样品。X 射线衍射和拉曼散射光谱分析显示,掺杂了 Cr3+ 的 SnO2 样品具有四方金红石结构。Cr3+ 浓度和退火温度对 SnO2 晶体的晶格参数没有影响,但影响了拉曼模式的出现和强度。光致发光(PL)和光致发光激发(PLE)分析探讨了合成样品的光学特性。有趣的是,除了与二氧化锡有关的发射峰外,还观察到二氧化锡八面体场中 Cr3+ 离子的发射跃迁。
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引用次数: 0
Application of Stable Random Vector with Gaussian Copula 稳定随机向量与高斯 Copula 的应用
Pub Date : 2023-12-23 DOI: 10.25073/2588-1124/vnumap.4819
Vo Thi Truc Giang, Ho Dang Phuc
More and more real-world datasets have heavy-tailed distribution, while the calculations for these distributions in multi-dimensional cases are complex. This work shows a method to investigate data of multivariate heavy-tailed distributions. The sufficient condition for every a-stable random vector is that it has α-stable marginals and Gaussian copula. From that results, we have a procedure testing stable distribution of multi-dimensional data and a formula representing density functions of multivariate stable distribution. Adopted a new tool, datasets about daily returns of 4 stocks on HoSE and 3 grains were analyzed.
现实世界中越来越多的数据集具有重尾分布,而这些分布在多维情况下的计算非常复杂。这项工作展示了一种研究多元重尾分布数据的方法。每个 a 稳定随机向量的充分条件是它具有 α 稳定边际和高斯协程。从这些结果中,我们得到了测试多维数据稳定分布的程序和表示多元稳定分布密度函数的公式。利用新工具,我们分析了 4 只荷证股票和 3 种谷物的日收益数据集。
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引用次数: 0
Analysis of the Structure and Luminescence Properties of Sr3Y2Ge3O12:0.05Eu3+ (SYGO:Eu3+) According to Judd–ofelt Theory 根据judd - felt理论分析Sr3Y2Ge3O12:0.05Eu3+ (SYGO:Eu3+)的结构和发光性能
Pub Date : 2023-08-08 DOI: 10.25073/2588-1124/vnumap.4800
N. M. C. H. P. Lan, N. Kien, C. X. Thang, N. Tung
In this report, SYGO:Eu3+ red phosphor have been successfully synthesized by sol-gel method. The X-ray diffraction results show that the sample has a cubic crystal structure, belonging to the space group Ia3d (230) without any doping. Scanning electron microscopy (FE-SEM) combined with EDS was performed to determine the microstructure and elemental composition of the fabricated phosphor. The particles are significantly agglomerated and are about ∼200 nm in size. The results of fluorescence property investigation (PLE-PL) show that, the maximum emission spectrum at 612 nm under ultraviolet light close to 395 nm for excitation. Calculating the J-O intensity parameters, the result is that Ω2 is larger than Ω4 which proves that the surrounding local structure of the doped ion is asymmetric. In addition, the luminescence efficiency approximately calculation is 70%. Phosphor SYGO:Eu3+ has been fabricated which can be used as a solid lighting material for WLED.
本文采用溶胶-凝胶法制备了SYGO:Eu3+红色荧光粉。x射线衍射结果表明,样品具有立方晶体结构,属于空间群Ia3d(230),未掺杂任何杂质。利用扫描电镜(FE-SEM)结合能谱仪(EDS)对制备的荧光粉的微观结构和元素组成进行了测定。颗粒明显团聚,尺寸约为~ 200nm。荧光特性研究(PLE-PL)结果表明,612 nm处的最大发射光谱在紫外光激发下接近395 nm。通过对J-O强度参数的计算,发现Ω2大于Ω4,证明掺杂离子的周围局部结构是不对称的。另外,其发光效率近似计算为70%。制备了可作为WLED固体照明材料的SYGO:Eu3+荧光粉。
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引用次数: 0
Strong Laws of Large Numbers for Weighted Sums of Hilbert-valued Coordinatewise PNQD Random Variables with Applications hilbert值坐标型PNQD随机变量加权和的强大数定律及其应用
Pub Date : 2023-07-06 DOI: 10.25073/2588-1124/vnumap.4829
Ta Van Chien, Bui Khanh Hang, Bui Thi Thuy Lien
The aim of this paper is to investigate results on almost sure convergence of weighted sums of coordinatewise pairwise negatively quadrant dependent random variables taking values in Hilbert spaces. As an application, the almost sure convergence of degenerate von Mises-statistics is investigated. Keywords: Negative quadrant dependence, Hilbert spaces, Weighted sums, Strong laws of large numbers.     
本文的目的是研究希尔伯特空间中坐标两两负象限相关随机变量加权和的几乎肯定收敛性的结果。作为应用,研究了退化von mises统计量的几乎肯定收敛性。关键词:负象限依赖,希尔伯特空间,加权和,大数强定律。
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引用次数: 0
Study of the Mixture of Rapeseed Oil and Waste Cooking Oil used for Insulation in Transformers 菜籽油与废食用油混合用于变压器绝缘的研究
Pub Date : 2023-06-20 DOI: 10.25073/2588-1124/vnumap.4778
Nguyen Van Dung, Nguyen Thi Tuyet Nhung, Le Vinh Truong
The blend of waste cooking oil and rapeseed oil was studied as an alternative to mineral oil in transformers. Waste cooking oil after filtering, neutralizing and drying was mixed with refined rapeseed oil. The ratio between waste cooking oil and rapeseed oil was determined based on the pour point. Physico-chemical parameters of the oil mixtures were measured according to the ASTM D6871, and the oil mixture was examined in both new and aged conditions. For ageing, the oil mixture was heated at 120 oC for 164 h with an air flow of 5.5 L/h. In addition, the influence of antioxidants on the breakdown voltage and ageing of the oil mixture was also studied. Experimental results showed that the mixture consisting of 15 vol.% of waste cooking oil and 85 vol.% of rapeseed oil met the standards of ASTM D6871. Tert-butylhydroquinone and propyl gallate significantly increased the oxidation stability index, breakdown voltage and ageing resistance of the the oil mixture.     
研究了废食用油与菜籽油的共混物作为变压器中矿物油的替代品。将过滤、中和、干燥后的废食用油与精制菜籽油混合。根据倾点确定了废食用油与菜籽油的配比。根据ASTM D6871测试了混合油的理化参数,并在新工况和旧工况下对混合油进行了检测。为了老化,将油混合物在120℃下加热164 h,空气流量为5.5 L/h。此外,还研究了抗氧化剂对混合油击穿电压和老化的影响。实验结果表明,废食用油添加量为15%,菜籽油添加量为85%的混合物符合ASTM D6871标准。叔丁基对苯二酚和没食子酸丙酯显著提高了混合油的氧化稳定性指数、击穿电压和耐老化性能。
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引用次数: 0
Enhancement of Methylene Blue Adsorption from ZnO/Activated Carbon Nanocompossites Prepared by Pyrolysis of Molten ZnCl2 with Rice Husks 稻壳热解制备氧化锌/活性炭纳米复合材料对亚甲基蓝的吸附
Pub Date : 2023-06-20 DOI: 10.25073/2588-1124/vnumap.4779
Nguyen Thi Luyen
In this work, we synthesized a facile step pyrolysis of ZnO/activated carbon nanocomposites by using molten ZnCl2 and rice husks in oxygen-limited environment. The mass ratio of molten ZnCl2 and rice husks was chosen from 0 to 5 wt.%, the pyrolysis temperature range from 400 to 800 oC. When the mass ratio of molten ZnCl2 and rice husks was equal to 1.0 and the pyrolysis temperature was at 800 oC, the size of ZnO nanoparticles in diameter was found to be of 10-20 nm. The ZnO/activated carbon nanocomposites exhibited a porous structure with the BET surface area, average pore diameter and pore volume of 643.9 m2/g, 4,76 nm and 0.255 cm3/g, respectively. To investigate the adsorption behavior of methylene blue, batch experiments were performed on all samples. The ZnO/activated carbon sample manufactured at a mass ratio of 1.0 and a pyrolysis temperature of 800 oC has the best methylene blue adsorption capability. The Langmuir isotherm was used to calculate the maximum adsorption capacity of methylene blue, which was 814.9 mg/g. Based on the obtained results, one can suggest that ZnO/activated carbon nanocomposites prepared by the facile pyrolysis route from molten ZnCl2 and rice husks possessing eco-friendly behaviour and low productioncost can be used as a potential adsorbent for wastewater treatment.
在这项工作中,我们在氧气限制的环境下,以熔融的ZnCl2和稻壳为原料,合成了一种快速热解ZnO/活性炭纳米复合材料。选择ZnCl2与稻壳的质量比为0 ~ 5wt .%,热解温度为400 ~ 800℃。当ZnCl2与稻壳的质量比为1.0,热解温度为800℃时,ZnO纳米颗粒的粒径为10 ~ 20 nm。ZnO/活性炭纳米复合材料的比表面积、平均孔径和孔体积分别为643.9 m2/g、4、76 nm和0.255 cm3/g。为了研究亚甲基蓝的吸附行为,对所有样品进行了批量实验。在质量比为1.0、热解温度为800℃时制备的ZnO/活性炭样品对亚甲基蓝的吸附性能最好。Langmuir等温线计算出亚甲基蓝的最大吸附量为814.9 mg/g。综上所述,以熔融ZnCl2和稻壳为原料,通过快速热解制备的ZnO/活性炭纳米复合材料具有环保性能和低生产成本,可作为一种潜在的废水处理吸附剂。
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引用次数: 0
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VNU Journal of Science: Mathematics - Physics
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