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Closed-Form Solutions of Stress Intensity Factors for Semi-elliptical Surface Cracks in a Cylindrical Bar Under Pure Tension

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Acta Mechanica Solida Sinica 2022年第2期35卷 344-356页

作者： M.K.ramezani S.ramesh J.Purbolaksono r.das Centre of Advanced Manufacturing and Materials Processing Department of Mechanical EngineeringFaculty of EngineeringUniversity of MalayaKuala Lumpur 50603Malaysia Department of Mechanical Engineering University of PertaminaJakarta 12220Indonesia Sir Lawrence Wackett Aerospace research Centre School of EngineeringRMIT UniversityMelbourneVI 3000Australia

In this work,the stress intensity factors(SIFs)for a wide range of semi-elliptical surface cracks with different inclination angles in a cylindrical bar subjected to pure tension were investigated *** main parameters considered to evaluate the SIFs were the crack size ratio(a/d),the crack aspect ratio(a/c),and the crack inclination angle(0).The dual-boundary element met hod implemented in software BEASY was used to compute the SIF values for *** her more,the general closed-form solutions were proposed to evaluate the corresponding SIFs for Mode I,Mode II and Mode III types of fracture through curve fitting *** solutions can provide accurate and reliable values of stress intensity factors for a crack on a cylindrical bar under pure tension in a rapid way compared to those obtained using computational *** addition,these results can be used as inputs for failure studies and life evaluations of cracked cylinder under working conditions.

关键词： Stress intensity factor Surface crack Solid cylinder Closed-form solution Dual-boundary element method

Electrical properties of Na_(2)Pb_(2)r_(2)W_(2)Ti_(4)V_(4)O_(30)(r=Dy,Pr)ceramics

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Journal of Advanced Ceramics 2013年第2期2卷 112-118页

作者： Piyush r.das B.N.PArIDA r.PADHEE r.N.P.CHOUDHArY Department of Physics Institute of Technical Education&ResearchSiksha‘O’Anusandahan UniversityKhandagiriBhubaneswar 751030OdishaIndia

The polycrystalline samples of complex tungsten bronze(TB)Na_(2)Pb_(2)r_(2)W_(2)Ti_(4)V_(4)O_(30)(r=Dy,Pr)compounds were prepared by solid-state reaction ***-temperature preliminary structural studies confirm the formation of the compounds in the orthorhombic crystal *** studies of electrical properties of the materials using complex impedance spectroscopy technique exhibit that the impedance and related parameters are strongly dependent upon temperature and microstructure(bulk,grain boundary,etc).An observation of negative temperature coefficient of resistance(NTCr)suggests the materials have semiconducting *** variation of AC conductivity with temperature shows a typical Arrhenius behavior of the *** the samples obey Jonscher’s universal power *** existence of hopping mechanism in the electrical transport processes in the system with non-exponential type of conductivity relaxation is confirmed by electrical modulus analysis.

关键词： ceramics impedance spectroscopy electrical properties ferroelectricity microstructure

Synthesis of rNA-Amphiphiles via Atom Transfer radical Polymerization in the Organic Phase

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Precision Chemistry 2023年第5期1卷 326-331页

作者： Jaepil Jeong Grzegorz Szczepaniak Subha r.das Krzysztof Matyjaszewski Department of Chemistry Carnegie Mellon UniversityPittsburghPennsylvania 15213United States Center for Nucleic Acids Science&Technology Carnegie Mellon UniversityPittsburghPennsylvania 15213United States University of Warsaw Faculty of Chemistry02-093 WarsawPoland

The combination of hydrophobic polymers with nucleic acids is a fascinating way to engineer the self-assembly behavior of nucleic acids into diverse nanostructures such as micelles,vesicles,nanosheets,and *** we developed a robust route to synthesize a rNA macroinitiator with protecting groups on the 2′-hydroxyl groups in the solid phase using an oligonucleotide *** protecting groups successfully solubilized the rNA macroinitiator,enabling atom transfer radical polymerization(ATrP)of hydrophobic *** a result,the rNA−polymer hybrids obtained by ATrP exhibited enhanced chemical stability by suppressing *** addition,we demonstrated evidence of controlled polymerization behavior as well as control over the molecular weight of the hydrophobic polymers grown from *** envision that this methodology will expand the field of rNA−polymer conjugates while vastly enhancing the possibility to alter and engineer the properties of rNA-based polymeric materials.

关键词： ATrP rNA rNA-amphiphiles nucleic acid block copolymer rNA−polymer conjugate TBDMS SBiB phosphoramidite solid-phase rNA synthesis

Ultralight,ductile metal mechanical metamaterials with super elastic admissible strain(0.1)

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Journal of Materials Science & Technology 2023年第31期162卷 227-233页

作者： H.Z.Zhong T.Song r.das C.W.Li J.F.Gu M.Qian Institute of Materials Modification and Modelling Shanghai Jiao Tong UniversityShanghai 200240China Centre for Additive Manufacturing School of EngineeringRMIT UniversityMelbourneVIC 3000Australia Sir Lawrence Wackett Aerospace research Centre School of EngineeringRMIT UniversityMelbourneVIC 3000Australia

Mechanical metamaterials are architectured cellular materials with unusual *** we report another type of metal mechanical metamaterials-their elastic admissible strain(EAS)is on the order of 0.1,compared to about 0.01 for common metallic *** conditions are required for a metal mechanical metamaterial to achieve this super EAS:(i)bending-dominated deformation;(ii)low density;(iii)an appropriate lattice topology,and(iv)an intrinsically high EAS for the lattice strut constituent *** findings of this work extend perspectives on metal mechanical metamaterials.

关键词： Metamaterials Lattice Superelasticity Elastic admissible strain Ti-6Al-4V Titanium

Dielectric response and pyroelectric properties of lead-free ferroelectric Ba_(3)(VO_(4))_(2)

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Journal of Advanced Dielectrics 2015年第1期5卷 43-49页

作者： Biswajit Pati r.N.P.Choudhary Piyush r.das B.C.Sutar Department of Physics J.K.B.K.Government CollegeCuttack 753004India Department of Physics Institute of Technical Education and Research Siksha O Anusandhan UniversityBhubaneswar 751030India Department of Physics Veer Surendra Sai University of Technology BurlaSambalpur 768018India Department of Physics Hi-Tech College Engineering Bhubaneswar 751025India

The current paper presents results of dielectric response,pyroelectric behavior and conductivity study of lead-free ferroelectric barium orthovanadate(Ba_(3)(VO_(4))_(2)or Ba_(3)V_(2)O_(8))ceramic,for a wide range of temperature and *** X-ray diffraction study suggests the formation of a single-phase compound in trigonal crystal *** SEM micrograph of gold-coated pellet sample shows well-defined and homogeneous *** studies of dielectric parameters(ε_(r)and tanδ)of the compound as a function of temperature and frequency reveal their independence over a wide range of temperature and *** nature of Polarization versus electric field(P-E)hysteresis loop of Ba_(3)V_(2)O_(8)at room temperature suggests its ferroelectric *** temperature dependence of pyroelectric coefficient and figure of merits of the sample support its dielectric *** nature of variation of dc conductivity with temperature confirms the Arrhenius and negative temperature coefficient of resistance(NTCr)behavior of the material.

关键词： X-ray diffraction Palmierite structure dielectric properties pyroelectric properties

Studies of electrical conductivity and magnetic properties of Bi_(1-x)Gd_(x)FeO_(3) multiferroics

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Journal of Advanced Dielectrics 2014年第2期4卷 35-40页

作者： Samita Pattanayak r.N.P.Choudhary Piyush r.das Multifunctional Material research Laboratory Siksha‘O'Anusandhan UniversityBhubaneswar 751030India

The polycrystalline samples of Bi_(1-x)Gd_(x)FeO_(3)(x=0,0.1,and 0.2)muliferroic oxides have been synthesized by a solid-state reaction/mixed oxide *** preliminary X-ray structural analysis with room temperature diffraction data confirmed the formation of single-phase *** of room temperature scanning electron micrograph(SEM)of the surface of the above samples exhibits a uniform distribution of plate-and rod shaped grains throughout the sample surface with less *** dielectric behavior of the materials was studied in a wide range of frequency(1 kHz-1 MHz)and temperature(30-400℃).The nature of temperature dependence of de conductivity confirms the Arrhenius behavior of the *** frequency-temperature dependence of ac conductivity suggests that the material obeys Jonscher's universal power *** increase in Gd-content results in the enhancement of spontaneous magnetization BiFeO_(3)(BFO)due to the collapse of spin cycloid *** magnetoelectric coupling coefficient of BFO has been enhanced on Gd-substitution.

关键词： Multiferroics dielectric properties electrical conductivity magnetic properties

SYNTHESIS AND CHArACTErIZATION OF COMPLEX FErrOELECTrIC OXIDE

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Journal of Advanced Dielectrics 2012年第4期2卷 79-88页

作者： PIYUSH r.das B.N.PArIDA r.PADHEE r.N.P.CHOUDHArY Department of Physics Institute of Technical Education and research Siksha'O'Anusandhan University Khandagiri Bhubaneswar 751030OdishaIndia

The polycrystalline sample of Li_(2)Pb_(2)Pr_(2)W_(2)Ti_(4)V_(4)O_(30) was prepared by a solid-state reaction *** preparation conditions of the compound have been optimized using thermal analysis(DTA and TGA)*** temperature structural analysis confirms the formation of single phase compound in orthorhombic crystal *** surface morphology of the sample,recorded by scanning electron microscope,shows uniform grain distribution on the surface of the *** observation of hysteresis loop confirmed that the material has ferroelectric properties at room *** properties of the material were studied by complex impedance spectroscopic *** dependence of electrical parameters(impedance,modulus,etc.)is strongly correlated to the micro-structural characteristics(bulk,grain boundary,etc.)of the sample.A typical temperature-dependent resistive characteristic of the sample(i.e.,negative temperature coe±cient of resistance(NTCr))exhibits its semiconducting *** temperature dependence of dc conductivity shows a typical Arrhenius behavior.A signature of ionic conductivity in the system was observed in ac conductivity *** sample obeys Jonscher's universal power *** hopping mechanism for electrical transport properties of the system with nonexponential-type conductivity relaxation was suggested from the electrical modulus analysis.

关键词： Solid-state reaction vanadates ferroelectric properties impedance electrical conductivity

铁和硫用量对煤液化的影响——模型建立与最佳条件选择

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煤化工 1992年第4期20卷 55-60页

作者： r.das Gupta 李雷中国矿业大学煤综合利用系

在温度为450℃、H_2压强稳定在24.5±0.2MPa的间歇式高压釜里,用Samla,Kottadih煤与低温煤焦油(230～330℃)在不同铁、硫浓度下进行了加氢反应试验。非线性参数估计和统计分析显示出,通过一种简单的二次回归模型,可以相当满意地解释随... 详细信息

在温度为450℃、H_2压强稳定在24.5±0.2MPa的间歇式高压釜里,用Samla,Kottadih煤与低温煤焦油(230～330℃)在不同铁、硫浓度下进行了加氢反应试验。非线性参数估计和统计分析显示出,通过一种简单的二次回归模型,可以相当满意地解释随铁和硫用量的不同,总量、煤、苯可溶性产物(BSP)和沥青烯转化率的变化情况。此外,在各种不同的非线性约束集下,多变量的、非线性目标函数的最优化表明,在铁和硫的特定用量下,油的产率随非需要产物的产率降至最小而变得最大。

关键词：铁硫煤液化

抵御“杀手小行星” 可能让地球更安全的科技

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空中英语教室（高级版．彭蒙惠英语） 2023年第4期 8-9,38,39页

作者： Saswato r.das 不详

美国宇航局(以下简称NASA)的科学家们成功地让一颗小行星偏离其运行轨道,让我们的星球又安全了一点儿。2022年9月26日,烘干机大小的“双小行星重定向测试”任务飞船(以下简称DArT),撞上了一个没有威胁性的小行星Dimorphos。此举证明:万... 详细信息

美国宇航局(以下简称NASA)的科学家们成功地让一颗小行星偏离其运行轨道,让我们的星球又安全了一点儿。2022年9月26日,烘干机大小的“双小行星重定向测试”任务飞船(以下简称DArT),撞上了一个没有威胁性的小行星Dimorphos。此举证明:万一有朝一日有“杀手小行星”朝我们而来,人类或许在地球就能组织开展保卫战。

关键词：小行星美国宇航局运行轨道重定向烘干机保卫战威胁性