检索结果-南通市图书馆

Improved thermal stability and infrared emissivity of high-entropy REMgAl_(11)O_(19)and LaMAl_(11)O_(19)(RE=La,Nd,Gd,Sm,Pr,Dy;M=Mg,Fe,Co,ni,Zn)

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2022年第9期104卷 131-144页

作者： Haolin Zhu Ling Liu Huimin xiang Fu-zhi Dai Xiaohui Wang Zhuang Ma Yanbo Liu Yanchun Zhou School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China National Key Laboratory of Science and Technology on Materials under Shock and Impact Beijing 100081China Beijing Institute of Technology Chongqing Innovation Center Chongqing 401120China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China

LaMgAl_(11)O_(19)(LMA),characterized by high melting point,low density and thermal conductivity as well as good infrared emissivity,is regarded as a potential candidate for the thermal protection of hypersonic ***,the unsatisfied phase stability at high temperature results in declining of the emissivity below 6μm,which limits the extensive applications of LaMgAl_(11)O_(19).In order to overcome this obstacle,three dense bulk high-entropy ceramics,(La_(0.2)Nd_(0.2)Gd_(0.2)Sm_(0.2)Pr_(0.2))MgAl_(11)O_(19)(HE LMA-1),(La_(0.2)Nd_(0.2)Gd_(0.2)Sm_(0.2)Dy_(0.2))Mg Al_(11)O_(19)(HE LMA-2)and La(Mg_(0.2)Fe_(0.2)Co_(0.2)ni_(0.2)Zn_(0.2))Al_(11)O_(19)(HE LMA-3),were designed and successfully prepared through solid state reaction at 1700℃for 4 h in one *** analyses show that the phase compositions of HE LMA-1,HE LMA-2 and HE LMA-3 are single-phase solid solutions with the relative density of 95.61%,95.49%and 94.31%,*** treatment experiments demonstrate that the phase composition of HE LMA-1 remains a single phase after high-temperature heating,while second phase appears in other two *** stability of HE LMA-1 is attributed to small average size differenceδ(~4%)of constitute ***,the average emissivity of HE LMA-1 in the range of 3-6μm reaches 0.9,which is significantly higher than that of LMA and other two HE LMA *** emissivity of all samples remains above 0.95 from 6 to 10μ*** the far infrared region(10-14μm),although the emissivity of these specimens decreases slightly,it still exceeds *** UV-Vis absorption spectra indicate that the formation of many discrete impurity energy levels with small intervals in HE LMA-1 promotes the f electrons to transit between adjacent impurity energy levels and conduction band,which enhances the infrared emission of HE LMA-1 below 6μ*** a word,with improved phase stability and thermal emissivity in infrared range,high-entropy REMgAl_(11)O_(19),especially(La_(0.2)Nd_(0.2)

关键词： High-entropy ceramics LaMgAl_(11)O_(19) Thermal stability Infrared emissivity UV-Vis absorption

Enabling highly efficient and broadband electromagnetic wave absorption by tuning impedance match in high-entropy transition metal diborides (HETMB_(2))

在线全文

学校读者我要写书评

暂无评论

Journal of Advanced Ceramics 2021年第6期10卷 1299-1316页

作者： Weiming ZHANG Fu-zhi DAI Huimin xiang Biao ZHAO Xiaohui WANG Na ni Rajamallu KARRE Shijiang WU Yanchun ZHOU Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China Henan Key Laboratory of Aeronautical Materials and Application Technology School of Material Science and EngineeringZhengzhou University of AeronauticsZhengzhou 450046China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Key Lab of Education Ministry for Power Machinery and Engineering School of Mechanical EngineeringShanghai Jiao Tong UniversityShanghai 200240China Zibo Firststar New Material Incorporated Co. Ltd.Zibo 255000China

The advance in communication technology has triggered worldwide concern on electromagnetic wave *** cope with this challenge,exploring high-performance electromagnetic(EM)wave absorbing materials with dielectric and magnetic losses coupling is urgently *** the EM wave absorbers,transition metal diborides(TMB2)possess excellent dielectric loss ***,akin to other single dielectric materials,poor impedance match leads to inferior ***-entropy engineering is expected to be effective in tailoring the balance between dielectric and magnetic losses through compositional ***,three HE TMB2 powders with nominal equimolar TM including HE TMB2-I(TM=Zr,Hf,Nb,Ta),HE TMB2-2(TM=Ti,Zr,Hf,Nb,Ta),and HE TMB2-3(TM=Cr,Zr,Hf,Nb,Ta)have been designed and prepared by one-step boro/carbothermal *** a result of synergistic effects of strong attenuation capability and impedance match,HE TMB2-1 shows much improved performance with the optimal minimum reflection loss(RL_(min))of-59.6 dB(8.48 GHz,2.68 mm)and effective absorption bandwidth(EAB)of 7.6 GHz(2.3 mm).Most impressively,incorporating Cr in HE TMB2-3 greatly improves the impedance match over 1-18 GHz,thus achieving the RLmin of-56.2 dB(8.48 GHz,2.63 mm)and the EAB of 11.0 GHz(2.2 mm),which is superior to most other EM wave absorbing *** work reveals that constructing high-entropy compounds,especially by incorporating magnetic elements,is effectual in tailoring the impedance match for highly conductive compounds,i.e.,tuning electrical conductivity and boosting magnetic loss to realize highly efficient and broadband EM wave absorption with dielectric and magnetic coupling in single-phase materials.

关键词： transition metal diboride(TMB2) high-entropy(HE)ceramics electronic structure microwave absorption dielectric and magnetic losses coupling

Lifetime of Polarized Fermions In Flight

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2002年第10期19卷 1427-1429页

作者： Shi zhi-Qiang ni Guang-Jiong Faculty of Science Xi'an Jiaotong University Xi'an 710049 Department of Physics Fudan University Shanghai 200433 Department of Physics Portland State University Portland OR 97207 USA

Based on the parity violation in the standard model, we study the dependence of the lifetime on the helicity of an initial-state fermion in weak interactions. It is pointed out that if initial fermions in decays are longitudinally polarized, then the lifetime of right-handed polarized fermions is greater than that of left-handed polarized fermions in flight with the same speed in any inertial system.

关键词：

Effects of different orthokeratology lens designs on slowing axial length elongation in children with myopia

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Ophthalmology(English edition) 2024年第10期17卷 1843-1849页

作者： Hai-Long ni xiang Chen Du-Ya Chen Pei-Ke Hu zhi-Yi Wu Eye Center the Second Affiliated Hospital of Zhejiang University School of MedicineHangzhou 310009Zhejiang ProvinceChina

AIM:To elucidate whether differences exist in the impact on retarding the elongation of axial length(AL)among children with myopia when utilizing orthokeratology(ortho-k)lenses employing the corneal refractive therapy(CRT)design versus those employing the vision shaping treatment(VST)***:This retrospective clinical trial aimed to collect and analyze AL data from individuals who wore ortho-k lenses for three years.A total of 654 subjects were enrolled and prescribed one of the three specific brands of ortho-k lenses:CRT,Euclid,and *** study’s primary focus was to compare the rates of AL elongation and myopic progression across these three brands of ortho-k ***:In the 3-year follow-up,the AL elongation exhibited variations of 0.73±0.36 mm in the CRT lens group,0.59±0.37 mm in the Euclid lens group,and 0.63±0.38 mm in the Mouldway lens group.A noteworthy disparity emerged between the CRT and Mouldway groups(Pnificant distinction between the CRT and Euclid groups(Pnificant difference when compared to the Mouldway group(P<0.05).CONCLUSION:Ortho-k lenses represent a pragmatic strategy for mitigating the advancement of *** contradistinction to ortho-k lenses utilizing the CRT design,those employing the VST design exhibited a more favorable impact regarding retarding AL elongation.

关键词： myopia orthokeratology design axial length

Calculations of β-decay half-lives of proton-rich nuclei

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2012年第12期55卷 2397-2406页

作者： ni DongDong REN ZhongZhou zhi QiJun Department of Physics Nanjing UniversityNanjing 210093China Kavli Institute for Theoretical Physics China Beijing 100190China Center of Theoretical Nuclear Physics National Laboratory of Heavy-Ion AcceleratorLanzhou 730000China GSI Helmholtzzentrum für Schwerionenforschung DarmstadtGermany School of Physics and Electronic Science Guizhou Normal UniversityGuiyang 550001China

We investigate the half-lives of β + /EC(electron capture) decay using the proton-neutron quasiparticle random-phase approximation(pnQRPA) with a δ-form Gamow-Teller residual *** particle-hole and particle-particle residual interactions are consistently introduced in dealing with the pnQRPA matrix *** sensitivity of the calculated half-lives to some physical quantities used in the calculations is *** are performed for even-even neutron-deficient isotopes ranging from Z = 10 to Z = *** agreement between experiment and theory is achieved especially for the nuclei far from stability,and the results of our calculations are discussed with comparison with other theoretical *** on the β-decay half-lives of some very neutron-deficient nuclei are also given for reference in future experiments.

关键词： proton-rich nuclei β-decay half-lives quasiparticle random-phase approximation

Electrochemical Behavior of Bulk Amorphous Steel Fe_(55)M_2Cr_(12)Mo_(10)B_6C_(13)Y_2 (M=ni,Cu,Nb)

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2010年第5期17卷 69-73页

作者： GUO Jin-hua GAO Zhen ni Xiao-jun LI De-ren LU zhi-chao Technology Center Advanced Technology and Materials Co Ltd Beijing 100081 China China Iron and Steel Research Institute Group Beijing 100081 China

Fe55 ni2 Cr12 Mo10 B6 C13 Y2 , Fe55 Cu2 Cr12 Mo10 B6 C13 Y2 and Fe55 Nb2 Cr12 Mo10 B6 C13 Y2 alloys with diameter of 4 mm were produced by copper mold casting. The effect of alloying additions （ni, Cu or Nb） on corrosion resistance of Fe55 Nb2 Cr12 Mo10B6 C13 Y2, Fe55 ni2 Cr12 Mo10 B6 C13 Y2 and Fe55 Cu2 Cr12 Mo10 B6 C13 Y2 alloys was studied by polarization curves and electrochemical impedance spectroscopy （EIS）. The results show that Fe55 ni2 Cr12 Mo10 B6C13 Y2 and Fe55 Cu2 Crl2 MOl0 B6 C13 Y2 alloys can be cast to form bulk metallic glasses. Fe55 ni2 Cr12 Mo10 B6 C13 Y2 and Fe55 Cu2 Cr12 Mo10 86 C13 Y2 amorphous alloys with passive potential about 1 500 mV exhibit good corrosion resistance in NaCI solution of 5% and 1 mol/L HC1 solution. The passive current density of the alloy with ni addition is lower than that of other alloys. EIS results only show one impedance element. Amorphous alloy Fe55 ni2 Cr12 Mo10 B6C13 Y2 with larger charge transfer reaction resistance indicates good corrosion resistance.

关键词： amorphous steel polarization curve electrochemical impedance spectroscopy

MODELING AND DYNAMICS ANALYSIS OF SHELLS OF REVOLUTION BY PARTIALLY ACTIVE CONSTRAINED LAYER DAMPING TREATMENT

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2013年第5期26卷 468-479页

作者： Qiao ni Yu xiang Yuying Huang Jing Lu College of Civil Engineering and Mechanics Huazhong University of Science and Technology Department of Automotive Engineering Guangxi University of Technology

A new model for a smart shell of revolution treated with active constrained layer damping （ACLD） is developed, and the damping effects of the ACLD treatment are discussed. The motion and electric analytical formulation of the piezoelectric constrained layer are presented first. Based on the authors~ recent research on shells of revolution treated with passive constrained layer damping （PCLD）, the integrated first-order differential matrix equation of a shell of revolution partially treated with ring ACLD blocks is derived in the frequency domain. By virtue of the extended homogeneous capacity precision integration technology, a stable and simple numerical method is further proposed to solve the above equation. Then, the vibration responses of an ACLD shell of revolution are measured by using the present model and method. The results show that the control performance of the ACLD treatment is complicated and frequency-dependent. In a certain frequency range, the ACLD treatment can achieve better damping characteristics compared with the conventional PCLD treatment.

关键词： active constrained layer damping (ACLD) shell of revolution integrated first-orderdifferential matrix equation control performance damping characteristics

Reconstruction of different scales of pore-fractures network of coal reservoir and its permeability prediction with Monte Carlo method

在线全文

学校读者我要写书评

暂无评论

International Journal of Mining Science and Technology 2017年第4期27卷 693-699页

作者： ni Xiaoming Chen Wenxue Li Zheyuan Gao xiang School of Energy Science and Engineering School of Civil Engineering Henan Polytechnic University Jiaozuo 454000 China Collaborative Innovation Center of Coalbed Methane and Shale Gas for Central Plains Economic Region Jiaozuo 454000 China Opening Project of Key Laboratory of Deep Mine Construction Henan Polytechnic University Jiaozuo 454000 China Department of Building Civil & Environmental Engineering Concordia University Montreal H3G1M8 Canada china Coal Tunnel Engineering Go. LTD Xuzhou 221000 China

There are millimeter, micron and nanometer scales of pores and fractures in coal to describe different scales of coal pores and fissures communicating path and to quantitatively characterize their permeability. Such information provides an important basis for studying coalbed methane output mechanism. The pores and fissures in a large number of coal samples were observed and counted by scanning electron microscopy and optical microscopy. The probability distribution models of pore-fissure network were then established. Different scales of pore-fissures 2D network models were reconstructed by Monte Carlo method. The 2D seepage models were obtained through assignment zero method and using Matlab software. The effect of permeability on different scale pore-fractures network was obtained by two-dimensional seepage equation. Predicted permeability is compared with the measured ones. The results showed that the dominant order of different scale pore-fractures connected path from high to low is millimeter-sized fractures, seepage pores and micron-size fractures. The contribution of coal reservoir permeability from large to small is millimeter-size fractures, micron-size fractures and seepage pores. Different parameters in different scale pore-fractures are of different influence *** of different scale pore-fractures network can clearly display the connectivity of porefractures, which can provide a basis for selecting migration path and studying gas flow pattern.

关键词： Fractures network Different scales Reconstruction Permeability

Reclassification and distribution patterns of discovered oils in theDongying Depression, Bohai Bay Basin, China

在线全文

学校读者我要写书评

暂无评论

Petroleum Science 2023年第1期20卷 114-127页

作者： Bing You Jian-Fa Chen zhi-Yong ni State Key Laboratory of Petroleum Resource and Prospecting China University of PetroleumBeijing102249China School of Geoscience China University of PetroleumBeijing102249China

The Dongying Depression is an important petrolifeous province,with diverse source rocks and complex petroleum distribution patterns.A total of 32 crude oils were analyzed by the gas chromatographyemass spectrometry and isotopic compositions to better understanding the petroleum systems in the study *** oil types were classified by hierarchical cluster *** I and II oils have closely correlation with the discovered source rocks,which have been confirmed to be mainly derived from the lower third and upper forth member of the Eocene Shahejie Formation source rocks(Es3^(L) and Es4^(U)),***,type III oils contain abundant gammacerane,tricyclic terpanes and C_(29) steranes and have lower values of δ13C than type I and II oils,indicating a completely different source rock and biological *** recently,type III oils fail to match any of the discovered source rock,which contains main contribution of aquatic organism or/and bacteria *** addition,the spacial distribution of these three oil types were *** I oils mainly distributed in the Es3 and Es4 reservoirs that closed to the generative *** II oils occurred in the Es4 reservoirs in the sourthern slope of the depression,which probably caused by lateral migration along the horizontal fractures and sandstone layers within the Es4 ***,type III oils in the sourthern slope of the depression were mainly discovered in the Eocene Kongdian or Ordocician reservoirs,which suggests great exploration potential of deep underlying strata.

关键词： Molecular biomarker Oil-oil correlation Oil distribution Kongdian Formation Dongying Depression