检索结果-南通市图书馆

Populations of Bright X-ray Sources in the Starburst Galaxies NGC 4038/4039

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Astronomy and Astrophysics 2007年第3期7卷 389-396页

作者： Xi-Wei liu xiang-Dong li Department of Astronomy Nanjing University Nanjing 210093

Assuming a naive star formation history, we construct synthetic X-ray source populations, using a population synthesis code, for comparison with the observed X-ray luminosity function （XLF） of the interacting galaxies NGC 4038/4039. We have included highand intermediate-mass X-ray binaries, young rotation-powered pulsars and fallback disk-fed black holes in modeling the bright X-ray sources detected. We find that the majority of the X-ray sources are likely to be intermediate-mass X-ray binaries, but for typical binary evolu- tion parameters, the predicted XLF seems to be steeper than observed. We note that the shape of the XLFs depends critically on the existence of XLF break for young populations, and suggest super-Eddington accretion luminosities or the existence of intermediate-mass black holes to account for the high luminosity end and the slope of the XLF in NGC 4038/4039.

关键词： binaries close - galaxies individual (NGC 4038/4039) - stars evolution -X-ray binaries

Thermodynamic Research on Precipitates in Low Carbon Nb-Microalloyed Steels Produced by Compact Strip Production

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2007年第2期23卷 267-272页

作者： Song xiang Guoquan liu Yang li Changrong li Andong WANG School of Material Science and Engineering University of Science and Technology Beijing Beijing 100083 China

Microalloying element Nb in low carbon steels produced by compact strip production （CSP） process plays an important role in inhibiting recrystallization, decreasing the transformation temperature and grain *** decreasing the rolling temperature, dislocations can be pinned by carbonitrides and the strength is increased. Based on the two sublattice model, with metal atom sublattice and interstitial atom sublattice,a thermodynamic model for carbonitride was established to calculate the equilibrium between matrix and carbonitride. In the steel produced by CSP, the calculation results showed that the starting temperature of precipitation of Ti and Nb are 1340℃ and 1040℃, respectively. In the range of 890-950℃, Nb rapidly precipitated. And the maximum of the atomic fraction of Nb in carbonitride was about 0.68. The morphologies and energy spectrum of the precipitates showed that （NbTi）（CN） precipitated near the dislocations. The experiment results show that Nb rapidly precipitated when the temperature was lower than 970℃, and the atomic fraction of Nb in carbonitride was about 60%-80%. The calculation results are in agreement with the experiment data. Therefore the thermodynamic model can be a useful assistant tool in the research on the precipitates in the low carbon steels produced by CSP.

关键词： Compact strip production Niobium Low carbon microalloyed steels Precipitation Thermodynamic model

Effect of herbicide acetochlor on cytochrome P450 monooxygenases and GST of earthworms Eisenia fetida

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2006年第1期18卷 135-140页

作者： XIAO Neng-wen liu xiang-hui li Wei GE Feng State Key Lab of Integrated Management of Pest Insects and Rodents Institute of Zoology Chinese Academy of Sciences Beijing 100080 China

To assess the sublethal toxicity of the herbicide acetochlor to earthworms and to find out biomarkers possible inducted under acetochlor exposure, Eiseniafetida was exposed to artificial soils supplemented with different concentrations of acetochlor（5, 10, 20, 40 and 80 mg/kg soil）. Effects of the acetochlor on cytochrome P450 monooxygenases p-nitroanisole O-demethylase（ODM）, aldrin epoxidase（AE） and glutathione-S-transferases （GSTs） activities were determined. The results revealed cytochrome P450 monooxygenases were elevated with increasing concentrations of acetochlor, and the AE activity increased significantly compared with control at the concentration of 80 mg/kg （P〈0.05）. However, ODM activity from E. fetida was not induced significantly by acetochlor at all treatments（P〉0.05）. Sodium dodecyl sulfate-polyacryamide gel electrophoresis（SDS-PAGE） showed that one protein band was visualized and no evident differences were found in protein profiles between treatments and control. The GST activity increased significantly with longer duration（P〈0.05） and increasing concentrations of acetochlor exposure（P〈0.05）. This study showed that the monooxygenases and GSTs activities in E. fetida could be induced by acetochlor, and thus, the AE and GST could be used in sublethal assays for soil contamination surveys and GST could be used as biomarkers of acetochlor exposure in E. fetida.

关键词： acetochlor Eiseniafetida p-nitroanisole O-demethylase aldrin epoxidase GST

Localization−delocalization transitions in non-Hermitian Aharonov−Bohm cages

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

Frontiers of physics 2024年第3期19卷 39-50页

作者： xiang li Jin liu Tao liu School of Physics and Optoelectronics South China University of TechnologyGuangzhou 510640China

A unique feature of non-Hermitian systems is the extreme sensitivity of the eigenspectrum to boundary conditions with the emergence of the non-Hermitian skin effect (NHSE). A NHSE originates from the point-gap topology of complex eigenspectrum, where an extensive number of eigenstates are anomalously localized at the boundary driven by nonreciprocal dissipation. Two different approaches to create localization are disorder and flat-band spectrum, and their interplay can lead to the anomalous inverse Anderson localization, where the Bernoulli anti-symmetric disorder induces mobility in a full-flat band system in the presence of Aharonov−Bohm (AB) Cage. In this work, we study the localization−delocalization transitions due to the interplay of the point-gap topology, flat band and correlated disorder in the one-dimensional rhombic lattice, where both its Hermitian and non-Hermitian structures show AB cage in the presence of magnetic flux. Although it remains the coexistence of localization and delocalization for the Hermitian rhombic lattice in the presence of the random anti-symmetric disorder, it surprisingly becomes complete delocalization, accompanied by the emergence of NHSE. To further study the effects from the Bernoulli anti-symmetric disorder, we found the similar NHSE due to the interplay of the point-gap topology, correlated disorder and flat bands. Our anomalous localization−delocalization property can be experimentally tested in the classical physical platform, such as electrical circuit.

关键词： non-Hermitian skin effects disorder flat band localization−delocalization transition

Removal of Cr(Ⅵ)by glutaraldehyde-crosslinked chitosan encapsulating microscale zero-valent iron:Synthesis,mechanism,and longevity

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 Environmental Sciences 2024年第8期142卷 115-128页

作者： Yijun Duan Fang liu xiang liu Miao li School of Environment Tsinghua UniversityBeijing 100084China Transportation Institute of Inner Mongolia University Hohhot 010070China

Microscale zero-valent iron(mZVI)has shown great potential for groundwater Cr(Ⅵ)***,low Cr(Ⅵ)removal capacity caused by passivation restricted the wide use of *** prepared mZVI/GCS by encapsulating mZVI in a porous glutaraldehydecrosslinked chitosan matrix,and the formation of the passivation layer was alleviated by reducing the contact between zero-valent iron *** average pore diameter of mZVI/GCS was 8.775 nm,which confirmed the mesoporous characteristic of this *** of batch experiments demonstrated that mZVI/GCS exhibited high Cr(Ⅵ)removal efficiency in a wide range of pH(2-10)and temperature(5-35℃).Common groundwater coexisting ions slightly affected m ZVI/*** material showed great reusability,and the average Cr(Ⅵ)removal efficiency was 90.41%during eight *** this study,we also conducted kinetics and isotherms ***-second-order model was the most matched kinetics *** Cr(Ⅵ)adsorption process was fitted by both Langmuir and Freundlich isotherms models,and the maximum Langmuir adsorption capacity of m ZVI/GCS reached243.63 mg/g,which is higher than the adsorption capacities of materials reported in most of the previous ***,the column capacity for Cr(Ⅵ)removal of a mZVI/GCS-packed column was 6.4 times higher than that of a mZVI-packed column in a 50-day ***,mZVI/GCS with a porous structure effectively relieved passivation problems of mZVI and showed practical application prospects as groundwater Cr(Ⅵ)remediation material with practical application prospects.

关键词： Chitosan Glutaraldehyde mZVI Cr(Ⅵ) Groundwater

Thermal fatigue and wear of compacted graphite iron brake discs with various thermomechanical properties

在线全文

学校读者我要写书评

暂无评论

China Foundry 2024年第3期21卷 248-256页

作者： Gui-quan Wang Zhuo Xu Zhong-li liu xiang Chen Yan-xiang li School of Nuclear Equipment and Nuclear Engineering Yantai UniversityYantai 264005ShandongChina School of Materials Science and Engineering Tsinghua UniversityBeijing 100084China Key Laboratory for Advanced Materials Processing Technology Ministry of EducationBeijing 100084China

The increase in payload capacity of trucks has heightened the demand for cost-effective yet high performance brake *** this work,the thermal fatigue and wear of compacted graphite iron brake discs were investigated,aiming to provide an experimental foundation for achieving a balance between their thermal and mechanical *** graphite iron brake discs with different tensile strengths,macrohardnesses,specific heat capacities and thermal diffusion coefficients were produced by changing the proportion and strength of *** peak temperature,pressure load and friction coefficient of compacted graphite iron brake discs were analyzed through inertia friction *** morphology of thermal cracks and 3D profiles of the worn surfaces were also *** is found that the thermal fatigue of compacted graphite iron discs is determined by their thermal properties.A compacted graphite iron with the highest specific heat capacity and thermal diffusion coefficient exhibits optimal thermal fatigue *** of the matrix at low temperatures significantly weakens the function of alloy strengthening in hindering the propagation of thermal *** the reduced hardness,increasing the ferrite proportion can mitigate wear loss resulting from low disc temperatures and the absence of abrasive wear.

关键词： compacted graphite iron brake disc thermomechanical properties thermal fatigue wear

Enhancement of ionic conductivity and fracture toughness by infiltrating porous li_(0.33)La_(0.56)TiO_(3) pellets

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2024年第2期42卷 392-398,I0006页

作者： Xiaojuan Lu Mingyang Duan Jingyu xiang Yuning liang Songtao liu Hebei Key Lab of Power Plant Flue Gas Multi-Pollutants Control Department of Environmental Science and EngineeringNorth China Electric Power UniversityBaoding071003China

Although solid-state lithium electrolytes have the potential to reduce the safety issues associated with organic liquid electrolytes,disadvantages such as low total conductivity,large interface impedance,and delamination of the interface due to cyclic stress still need to be *** solid-state lithium-ion conductor li_(0.33)La_(0.56)TiO_(3)(LLTO) was prepared via a hydrothermal route by using CTAB as templates in this *** LLTO with micro-porous channels was obtained and the total conductivity is comparable to the non-porous *** LLTO pellets are infiltrated with the non-porous LLTO precursor solution,and the total conductivities of the infiltrated porous LLTO are all higher than those without *** infiltration,the porous LLTO calcined at 600℃ achieves the highest total conductivity,7.88×10^(-5) S/*** fracture toughness of the infiltrated LLTO is higher than that of the non-porous *** results demonstrate a new way to prepare solid-state lithium-ion conductors with high ionic conductivity and great tolerance to cyclic stress.

关键词： Perovskite Porous material Infiltration Ionic conductors Fracture toughness Rare earths

在线全文

学校读者我要写书评

暂无评论

苯酚选择性氧化还原合成对苯二酚研究

广州化工 2024年第2期52卷 137-139页

作者：王芳黄杰军徐林刘相李扬州工业职业技术学院江苏扬州225127 江苏扬农化工集团有限公司江苏扬州225002

苯酚选择性氧化还原制备对苯二酚反应具有潜在的工业应用价值。本文使用复合型催化剂有机硒醚/CNTs将苯酚选择性地定向氧化为对苯醌,对苯醌在Pt/C催化剂的作用下还原为对苯二酚。为了提高对苯醌的收率,本文将硒催化组分固定在中空多孔... 详细信息

苯酚选择性氧化还原制备对苯二酚反应具有潜在的工业应用价值。本文使用复合型催化剂有机硒醚/CNTs将苯酚选择性地定向氧化为对苯醌,对苯醌在Pt/C催化剂的作用下还原为对苯二酚。为了提高对苯醌的收率,本文将硒催化组分固定在中空多孔的碳纳米管上以增大催化剂的比表面积,苯酚氧化制备对苯醌选择性高达92.5%,具有催化剂制备简单、原料转化率和产物选择性高和废水排放量少等优势。

关键词：苯酚氧化还原对苯醌对苯二酚

Influence of Dog-Bone Apex on Shape During Slab Horizontal Rolling Process

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2007年第3期14卷 37-41页

作者： YU Hai-liang liu xiang-hua li Chang-sheng WANG Guo-dong State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110004 Liaoning China

The deformation of slab with dog-bone shape during the horizontal rolling process was simulated using FEM, and the influences of apical dislocation of dog-bone on the slab spread as well as the minimum crop end loss and the lost width at slab head and tail were analyzed. The results show that with the increase in the apical dislocation of dog-bone （LA）, the slab spread and the minimum crop end loss at slab head and tail decrease, while the lost width at slab head and tail increases. Meanwhile, the relationships of S/LA-LA, LH/LA-LA, WH/LA-LA, L T/LA- LA, and W T/LA-LA were obtained.

关键词： dog-bone apical dislocation horizontal rolling FEM