检索结果-南通市图书馆

Y_5Si_3C and Y_3Si_2C_2: Theoretically predicted MAX phase like damage tolerant ceramics and promising interphase materials for SiC_f/SiC composites

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2019年第3期35卷 313-322页

作者： Yanchun Zhou Huimin Xiang Fu-zhi dai Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials & Processing Technology

Researching for interphase materials that can protect SiC fibers from oxygen and water vapor attacks has become one of the most important issues for the applications of SiC_f/SiC composites in high-temperature combustion environment. However, such kinds of interphase materials are not available yet. Herein,we report theoretically predicted properties of two promising interphase materials Y_5Si_3 C and Y_3Si_2C_*** crystallizing in different structures, they share the common features of layered structure,anisotropic chemical bonding, anisotropic electrical and mechanical properties, and low shear deformation resistance. The bulk moduli for Y_5Si_3C and Y_3Si_2C_2 are 78 and 93 GPa, respectively; while their shear moduli are 52 and 50GPa, respectively. The maximum to minimum Young's modulus ratios are1.44 for Y_5Si_3C and 3.27 for Y_3Si_2C_2. Based on the low shear deformation resistance and low Pugh's ratios(G/B = 0.666 forY_5Si_3C and 0.537 for Y_3Si_2C_2; G: shear modulus; B: bulk modulus), they are predicted as damage tolerant and soft ceramics with predicted Vickers hardness of 9.6 and 6.9 GPa, *** cleavage plane and possible slip systems are(000 l) and(0001)[1120] and(1010)[0001] forY_5Si_3C,and those for Y_3Si_2C_2 are {h00} and(010)[101]. Since the oxidation products are water-vapor resistant Y2 Si2 O7, Y2 SiO5 and/or Y_2 O_3 upon oxidation, and the volume expansions are ca 140% and ca 26% for Y_5Si_3C and Y_3Si_2C_2, they are expected to seal the interfacial cracks in SiC_f/SiC composites. The unique combination of easy cleavage, low shear deformation resistance, volume expansions upon oxidation, and the resistance of the oxidation products to water vapor attack warrant them promising as interphase materials of SiC_f/SiC composites for water-vapor laden environment applications.

关键词： Y5Si3C Y3Si2C2 Interphase material Damage tolerant ceramics Electronic structure

A multithreaded parallel upwind sweep algorithm for the S_(N) transport equations discretized with discontinuous finite elements

在线全文

学校读者我要写书评

暂无评论

Nuclear Science and Techniques 2023年第12期34卷 229-241页

作者： zhi‑Wei Zong Mao‑Song Cheng Ying‑Chi Yu zhi‑Min dai Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China University of Chinese Academy of Sciences Beijing 100049China

The complex structure and strong heterogeneity of advanced nuclear reactor systems pose challenges for high-fidelity neutron-shielding calculations. Unstructured meshes exhibit strong geometric adaptability and can overcome the deficiencies of conventionally structured meshes in complex geometry modeling. A multithreaded parallel upwind sweep algorithm for S_(N) transport was proposed to achieve a more accurate geometric description and improve the computational efficiency. The spatial variables were discretized using the standard discontinuous Galerkin finite-element method. The angular flux transmission between neighboring meshes was handled using an upwind scheme. In addition, a combination of a mesh transport sweep and angular iterations was realized using a multithreaded parallel technique. The algorithm was implemented in the 2D/3D S_(N) transport code ThorSNIPE, and numerical evaluations were conducted using three typical benchmark problems:IAEA, Kobayashi-3i, and VENUS-3. These numerical results indicate that the multithreaded parallel upwind sweep algorithm can achieve high computational efficiency. ThorSNIPE, with a multithreaded parallel upwind sweep algorithm, has good reliability, stability, and high efficiency, making it suitable for complex shielding calculations.

关键词： Shielding calculation Discrete ordinates method Discontinuous Galerkin finite element method Unstructured meshes

Structures and energetics of semicoherent interfaces of precipitates in hcp/bcc systems:A molecular dynamics study

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2021年第8期67卷 50-60页

作者： Jin-Yu Zhang Fu-zhi dai zhi-Peng Sun Wen-Zheng Zhang Key Laboratory of Advanced Materials(MOE) School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China Science and Technology of Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of ChinaChengdu 610041China

α/β(hcp/bcc)interfaces are of great importance in the microstructure development and the mechanical properties of titanium and zirconium *** work contributes to the study of interface energetics and interfacial structures of the precipitate in the hcp/bcc system based on a simulation study using molecular statics(MS)and molecular dynamics(MD).The input orientation relationship(OR)was calculated based on the O-line *** on the energy of the interfaces containing the invariant line(IL),two preferred facets were determined by the Wulff construction,which explained the observed orientations of the habit plane(HP)and the side facet(SF).The deviation of the observed precipitate morphology from the equilibrium shape was discussed in terms of interface *** structures of the interfaces surrounding a three-dimensional(3 D)precipitate,including the preferred facets and the end face,were obtained at the atomic *** simulated dislocation structures and atomic structures in these interfaces are in good agreement with those of the experimental observations for Ti-Cr alloys.A method was suggested for modifying the O-cell structure with the guidance of the relaxed structure,yielding consistency between the calculated dislocation structure based on the generalized O-element approach and the simulation results.

关键词： Interface Misfit dislocation Precipitate

Full-frame Data Reduction Method:A Data Mining Tool to Detect the Potential Variations in Optical Photometry

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2023年第5期23卷 110-141页

作者： zhi-Bin dai Hao Zhou Jin Cao Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 101408China School of Information Science and Engineering of Yunnan University Kunming 650500China

A Synchronous Photometry Data Extraction(SPDE)program,performing indiscriminate monitoring of all stars appearing in the same field of view of an astronomical image,is developed by integrating several Astropy affiliated packages to make full use of time series observed by traditional small/medium aperture ground-based *** complete full-frame stellar photometry data reductions implemented for the two time series of cataclysmic variables:RX J2102.0+3359 and Paloma J0524+4244 produce 363 and 641 optimal light curves,respectively.A cross-identification with SIMBAD finds 23 known stars,of which 16 are red giant-/horizontal-branch stars,2 W UMa-type eclipsing variables,2 program stars,an X-ray source and 2 Asteroid Terrestrial-impact Last Alert System *** on the data products from the SPDE program,a follow-up light curve analysis program identifies 32 potential variable light curves,of which 18 are from the time series of RX J2102.0+3359,and 14 are from that of Paloma J0524+*** are preliminarily separated into periodic,transient,and peculiar *** querying for the 58 VizieR online data catalogs,their physical parameters and multi-band brightness spanning X-ray to radio are compiled for future analysis.

关键词： catalogs-stars fundamental parameters-stars variables general-methods data analysis-techniques photometric

Theoretical investigation on the stability, mechanical and thermal properties of the newly discovered MAB phase Cr4AlB4

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2020年第4期39卷 161-166页

作者： Fu-zhi dai Haiming Zhang Huimin Xiang Yanchun Zhou Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing100076China School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing100044China

The nanolaminated MAB phases have attracted great research interests in recent years due to their similarities to MAX phases,which display both metallic and ceramic-like *** the present work,a newly discovered MAB phase Cr4AlB4 was investigated by first principles *** evaluations indicate that Cr4AlB4 can be synthetized in Al lean condition,which can further transform to Cr2AlB2 in Al rich *** full set of elastic properties and their dependences on temperature,ideal strengths under different tensile and shear deformations,and thermal expansions of Cr4AlB4 were *** results reveal that the properties of Cr4AlB4 are dominated by the layered crystal structure and weak bonding nature between Al and Cr2B2 layers,including low elastic stiffness and large thermal expansion along[010]direction(the stacking direction of Al and Cr2B2 layers),low shear resistances in(010)plane,and preferentially cleavage along and/or shear in(010)***,it suggests that Cr4AlB4 displays similar mechanical properties to MAX phases,including readily machinable,thermal shock resistant,and damage *** combination with the fact that Cr,Al and B all can form dense oxides to protect the material from further oxidation,Cr4AlB4 is regarded as a promising high temperature ceramic.

关键词： MAB phase Cr4AlB4 First-principles Mechanical properties Thermal properties

New Metrics of the Tropospheric Biennial Oscillation in the East Asian Summer Monsoon and Its Interdecadal Shift

在线全文

学校读者我要写书评

暂无评论

Atmospheric and Oceanic Science Letters 2013年第6期6卷 440-444页

作者： dai zhi-Xiu State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institution of Atmospheric Physics Chinese Academy of Sciences

This study designed a simple index for measuring irregular tropospheric biennial oscillation(TBO) activities, which was used to determine that the TBO in the East Asian Summer Monsoon(EASM), the most important summer precipitation system for China, has strengthened rather than weakened since the late 1970s. The lead/lag correlations between the EASM and tropical Indian-Pacific sea surface temperature(SST) suggest a relationship between interbasin SST and EASM coupling processes and that this alternative correlation pattern is likely related to TBO. Significant correlation occurred only in recent decades, which implies a reinforcement of TBO in the EASM. From records of representative points in the Indian-Pacific, the interdecadal intrinsic SST modes of the areas can be obtained with ensemble empirical mode decomposition owing to its good temporal locality. Statistical results show Indian-Pacific SST interdecadal trends that include out-of-phase and in-phase warming before and after the late 1970s, respectively, which may be responsible for the TBO interdecadal augmentation present since the late 1970s.

关键词： TBO interdecadal shift EASM Indian-Pacific SST

M2M’AlB4（M = Mn, Fe, Co, M’ = Cr, Mo, W）: Theoretical predicted ordered MAB phases with Cr3AlB4 crystal structure

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2019年第7期35卷 1432-1438页

作者： Fu-zhi dai Huimin Xiang Yinjie Sun Yanchun Zhou Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials & Processing Technology

The nanolaminated MAB phases have attracted great research interests due to their unusual combination of metal-like and ceramic-like properties, which is similar to MAX phases. Recently, ordered quaternary MAX phases have been discovered, which enriches the family of MAX phases, and opens a new window to tailor the properties of MAX phases and to develop new MXenes. In the present work, we explored possible ordered quaternary MAB phases with Cr3AlB4 structure(space group: Pmmm) by first-principles calculations. The predictions show that M2M’AlB4 phases with M = Mn, Fe, Co and M’ = Cr, Mo, W exhibit strong tendency of ordering, where M locates at 2t site(0.5, 0.5, z2t) and M’ locates at 1 g site(0, 0.5,0.5). The main driving force of ordering may be the differences in bonding strengths between Al and M elements. Analyses on chemical bonds reveal that bonding strengths increase following the order:Al-Mn < Al-Fe < Al-Co, which is consistent with the prediction that ordering tendency increases when M changes from Mn to Co, as derived from enthalpy differences. The ordered M2M’AlB4 phases with M =Mn or Fe are predicted ferromagnetic and ordered M2M’AlB4 phases display lower shear resistance and possibly better ductility in comparison to Cr3AlB4.

关键词： MAB phase Ordered structure First-principle calculations Cr3AlB4 Chemical bonds Ultrahigh temperature ceramics

Feasibility of an innovative long-life molten chloride-cooled reactor

在线全文

学校读者我要写书评

暂无评论

Nuclear Science and Techniques 2020年第4期31卷 1-15页

作者： Ming Lin Mao-Song Cheng zhi-Min dai Shanghai Institute of Applied Physics Chinese Academy of SciencesJiading CampusShanghai 201800China University of Chinese Academy of Sciences Beijing 100049China

Molten salt-cooled reactor is one of the six GenIV reactors with promising characteristics including safety,reliability,proliferation resistance,physical protection,economics,and *** this paper,a small innovative molten chloride-cooled fast reactor(MCCFR)with 30-year core and a target 120-MWt thermal power was *** its feasible study,neutronics,thermal-hydraulics,and radiation damage analysis were *** key design properties including kinetics parameters,reactivity swing,reactivity feedback coefficients,maximum accumulated displacement per atom(DPA)of reactor pressure vessel(RPV)and fuel cladding,and maximum coolant,cladding,and fuel temperatures were *** results showed the MCCFR could operate without refueling for 30 years with overall negative reactivity feedback coefficients up the end of its *** its 30-year life,the excess reactivity was well managed by constantly pulling out the control *** maximum accumulated DPA on RPV and fuel cladding were 8.92 dpa and 197.03 dpa,respectively,which are both below the design ***,the maximum coolant,cladding and fuel center temperatures were all below the design limits during its entire *** to these results,the MCCFR core design with long life is feasible.

关键词： Molten salt-cooled reactor Neutronics Radiation damage Thermal-hydraulics

Cr5Si3B and Hf5Si3B:New MAB phases with anisotropic electrical,mechanical properties and damage tolerance

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2018年第8期34卷 1441-1448页

作者： Yanchun Zhou Huimin Xiang Fu-zhi dai zhihai Feng Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyNo.1 South Dahongmen RoadBeijing 100076China

Through a combination of electronic structure, chemical bonding and mechanical property investigations, anisotropic electrical and mechanical properties, and damage tolerant ability of MAB phases CrsSi3 B and HfsSi3B are predicted. The anisotropic electrical conductivity is due to the anisotropic distribution of Cr in CrsSiaB and Hf in HfsSi3B, which mainly contribute to the electrical conductivity. The anisotropic mechanical properties are underpinned by the anisotropic chemical bonding within the crystal structures of CrsSi3B and HfsSi3B. The high stiffness is determined by the strong covalent-ionic Crl--B--Crl and Crl--Si bonds in CrsSi3B and the ionic-covalent Hfl--B--Hfl and Si--B bonds in HfsSi3B; while the low shear deformation resistance is attributed to the presence of metallic Cr--Cr, Hf--Hf and Si--Si bond. Based on the low Pugh＇s ratio, CrsSi3B and Hfs Si3B are predicted tolerant to damage. The possible cleavage plane is （0001） and the possible slip systems are 〈1 100〉1{11 20} and 〈11 20〉1{0001} for both CrsSi3B and HfsSi3B.

关键词： MAB phases CrsSi3B and HfsSi3 BFirst-principles calculations Mechanical properties Chemical bonding