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Analysis of the applicability of collision probability algorithms for nonlinear relative motion

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Science China(Physics,Mechanics & Astronomy) 2013年第5期56卷 1041-1046页

作者： xu XiaoLi xiong YongQing Purple Mountain Observatory Chinese Academy of Sciences Key Laboratory of Space Object and Debris Observatory Purple Mountain ObservatoryChinese Academy of Sciences

In the calculation of the collision probability between space objects, the assumption of linear relative motion is generally adopted to simplify the problem because most encounters are at high relative velocity. Nevertheless, the assumption is no longer valid for encounters at extremely low velocities, and a new algorithm is urgently needed for computing collision probability for space objects having nonlinear relative motion. In this particular case, the direction associated with relative velocity is reintroduced for integration. The different integral limits would lead to the variations of probability and integral time. Moreover, the application scope of this new algorithm is also presented. Since the nonlinear effect is only significant in some certain situations, the new algorithm needs to be considered only in such certain situations. More specifically, when space objects in circular orbits encounter with a tiny inclined angle (the extreme situation), the new algorithm can derive much more accurate collision probability than the linear method, that is to say, the linearity assumption involved in general collision probability formulation is not adequate anymore. In addition, the deviation of the probability derived by the linear method (linear collision probability) from that derived by the nonlinear method (nonlinear collision probability) also weakly depends on the relative distance and combined covariance, and essentially depends on their ratio.

关键词： space debris collision probability nonlinear relative motion integral limits

Layered space time codes and capacity analysis in correlated fading channels with distributed antenna system

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The Journal of China Universities of Posts and Telecommunications 2011年第1期18卷 28-35页

作者： xiong fei ZHANG Jian-hua ZHANG Ping Wireless Technology Innovation Institute Key Laboratory of Universal Wireless Communication Ministry of Education 13eijing University of Posts and Telecommunications Beijing 100876 China

In this paper we have investigated the performance of downlink generalized distributed antenna system （GDAS）. Under the assumption of spatial correlated fading conditions, we have derived the numeric expression of correlated coefficients according to series of Bessel function, and have lifted the range restriction of the mean angle of incident. Moreover, the architecture of distributed generalized layered space time codes （GLST） has been considered in order to achieve both multiplexing gain and diversity gain while we have used basis vector from null space instead of orthogonal set to obtain the same system performance but with lower complexity. Furthermore, in order to maximize the capacity, Gerschgorin circles based fast antenna selection algorithms have been evaluated including a discussion of those simulation results.

关键词： GDAS GLST capacity correlated fading channel

Harnessing Interactional Sensory Genes for Rationally Reprogramming Chaotic Metabolism

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Research 2023年第3期2022卷 295-308页

作者： Chunlin Tan Ping xu fei Tao State Key Laboratory of Microbial Metabolism Joint International Research Laboratory of Metabolic and Developmental Sciencesand School of Life Sciences and BiotechnologyShanghai Jiao Tong UniversityShanghaiChina

Rationally controlling cellular metabolism is of great importance but challenging owing to its highly complex and chaotic *** existing sensory proteins like histidine kinases(HKs)are understood as“sensitive nodes”of biological networks that can trigger disruptive metabolic reprogramming(MRP)upon perceiving environmental ***,the“sensitive node”genes were adopted to devise a global MRP platform consisting of a CRISPR interference-mediated dual-gene combinational knockdown toolbox and survivorship-based metabolic interaction decoding *** platform allows users to decode the interfering effects of n×n gene pairs while only requiring the synthesis of n pairs of primers.A total of 35 HK genes and 24 glycine metabolic genes were selected as the targets to determine the effectiveness of our platform in a Vibrio *** platform was applied to decode the interfering impact of HKs on antibiotic resistance in strain FA2.A pattern of combined knockdown of HK genes(sasA_8 and 04288)was demonstrated to be capable of reducing antibiotic resistance of Vibrio by *** of combined knockdown of glycine pathway genes(e.g.,gcvT and ltaE)and several HK genes(e.g.,cpxA and btsS)were also revealed to increase glycine *** platform may enable an efficient and rational approach for global MRP based on the elucidation of high-order gene interactions.A web-based 1-stop service(https://***)is also provided to simplify the implementation of this smart strategy in a broad range of cells.

关键词： metabolism Rational programming

Control of Austenite Characteristics and Ferrite Formation Mechanism by Multiple-Cyclic Annealing in Quenching and Partitioning Steel

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Acta Metallurgica Sinica(English Letters) 2022年第7期35卷 1143-1156页

作者： fei Peng Yunbo xu Xingli Gu College of Materials Science and Engineering Hunan UniversityChangsha 410082China State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China Technology Center of Angang Steel Co. Ltd.Anshan 114009China

Quenching and partitioning(Q&P)treatment is a novel method to produce advanced high strength steel with excellent mechanical *** this study,combination of multiple-cyclic annealing and Q&P process was compared with traditional cold-rolled Q&P steel to investigate the microstructural characteristics and austenite *** results showed that retained austenite in traditional Q&P sample was principally located in the exterior of austenite transformation products,while those in multiple-cyclic annealing samples were mainly distributed inside the transformation *** the increase in cyclic annealing number,both of austenite fraction and austenite carbon content increased,attributing to higher initial austenite carbon content and larger number of austenite/neighbored phase interface to act as carbon partitioning *** traditional Q&P sample,the deformed ferrite was recrystallized by sub-grain coalescence,while the austenite was newly nucleated and grew up during annealing *** a comparison,the ferrite in multiple-cycle annealing samples was formed by means of three routes:tempered martensite that completely recovered with retention of interior martensite variant,epitaxial ferrite that formed on basis of tempered martensite,ferrite that newly nucleated and grew up during the final annealing *** of lath martensite and twin martensite were formed as initial martensite and then tempered during partitioning process to precipitateεcarbide with C enrichment,Mn enrichment and homogeneous Si *** with the traditional cold-rolled Q&P steel,the Q&P specimens after multiple-cyclic annealing show smaller strength and much larger elongation,ascribing to the coarser microstructure and more efficient transformation induced plasticity(TRIP)effect deriving from retained austenite with high carbon content and larger volume *** application of double annealing treatment can optimize the mechanical properties of Q&P steel to

关键词： Quenching and partitioning Cyclic annealing Ferrite formation Retained austenite

Analytical Solution for Predicting In-plane Elastic Shear Properties of 2D Orthogonal PWF Composites

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Chinese Journal of Aeronautics 2012年第4期25卷 575-583页

作者： CHENG xu xiong Junjiang BAI Jiangbo School of Transportation Science and Engineering Beihang UniversityBeijing 100191China

This paper proposes a new analytical solution to predict the shear modulus of a two-dimensional（2D） plain weave fabric（PWF） composite accounting for the interaction of orthogonal interlacing strands with coupled shear deformation modes including not only relative bending but also torsion,*** two orthogonal yarns in a micromechanical unit cell are idealized as curved beams with a path depicted by using sinusoidal shape *** internal forces and macroscopic deformations carried by the yarn families,together with macroscopic shear modulus of PWFs are derived by means of a strain energy approach founded on *** sets of experimental data pertinent to three kinds of 2D orthogonal PWF composites have been implemented to validate the new *** calculations from the new model are also compared with those by using two models in the earlier *** is shown that the experimental results correlate well with predictions from the new model.

关键词： textile composites mechanical properties shear modulus properties plain weave fabric

Reduction of entropy uncertainty for qutrit system under non-Markov noisy environment

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Chinese Physics B 2020年第4期29卷 165-171页

作者： xiong xu Mao-Fa Fang Synergetic Innovation Center for Quantum Effects and Applications Key Laboratory of Low-dimensional Quantum Structures and Quantum Control of Ministry of EducationSchool of Physics and ElectronicsHunan Normal UniversityChangsha 410081China

We explore the entropy uncertainty for qutrit system under non-Markov noisy environment and discuss the effects of the quantum memory system and the spontaneously generated interference(SGI)on the entropy uncertainty in *** results show that,the entropy uncertainty can be reduced by using the methods of quantum memory system and adjusting of ***,the entropy uncertainty can be decreased obviously when both the quantum memory system and the SGI are simultaneously applied.

关键词： entropy uncertainty relation non-Markov noisy qutrit and spontaneously generated interference

GENERALIZED CONFIDENCE REGIONS OF FIXED EFFECTS IN THE TWO-WAY ANOVA

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Journal of Systems Science & Complexity 2008年第2期21卷 276-282页

作者： Weiyan MU Shifeng xiong Xingzhong xu Department of Mathematics Beijing Institute of Technology Beijing 100081 China Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100190 China

The authors discuss the unbalanced two-way ANOVA model under heteroscedasticity. By taking the generalized approach, the authors derive the generalized p-values for testing the equality of fixed effects and the generalized confidence regions for these effects. The authors also provide their frequentist properties in large-sample cases. Simulation studies show that the generalized confidence regions have good coverage probabilities.

关键词： ANOVA generalized confidence region generalized p-value heteroscedasticity unbalanced.

Copper release and ROS in antibacterial activity of Ti-Cu alloys against implant-associated infection

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Rare Metals 2023年第6期42卷 2007-2019页

作者： Hai-Lin Yang Ling Zou Akram Nasser Juaim Chen-xu Ma Meng-Zhen Zhu fei xu Xiao-Na Chen Yin-Zhou Wang xiong-Wen Zhou State Key Laboratory of Powder Metallurgy Central South UniversityChangsha410083China National Clinical Research Center for Geriatric Disorders Xiangya HospitalCentral South UniversityChangsha410008China Department of Prosthodontics Center of StomatologyXiangya HospitalCentral South UniversityChangsha410008China Department of Oral Implantology Xiangya Stomatological Hospital and Xiangya School of StomatologyCentral South UniversityChangsha410008China Department of Prosthodontics Faculty of DentistryThamar UniversityDhamarYM999101Yemen Center of Stomatology Xiangya HospitalCentral South UniversityChangsha410008China

Enhancing the antibacterial properties of the currently used implant materials is a major concern of healthcare providers to minimize the impact of peri-implant infection and improve implant survival *** this study,titanium-copper sintered alloys(3 wt% and 5 wt%Cu) were developed for medical implant *** phase identification,microstructure,copper ions release,and wettability of these alloys were evaluated using X-ray diffraction(XRD),optical microscope(OM),scanning electron microscope(SEM),transmission electron microscope(TEM),energy-dispersive X-ray spectroscope(EDS),inductively coupled plasma spectroscope(ICP) and drop shape *** antibacterial activities of Ti-Cu alloys against Porphyromonas gingivalis and Streptococcus mutans were evaluated using inhibition zone assay,plate counting assay,live/dead fluorescent staining,SEM and reactive oxygen species(ROS) staining *** results demonstrated that Ti-Cu alloys are composed of α-Ti and Ti_(2)Cu phases that increased with increased Cu content of the ***-Cu alloys exhibited antibacterial activity against both bacteria species in a time-dependent *** antibacterial rates of Ti-3Cu and Ti-5Cu after72 h were 57% and 70% against Porphyromonas gingivalis and 63% and 78% against Streptococcus mutans,*** highest amount of Cu^(2+) released from these alloys was 0.3 mg·L^(-1) during the first 24 h,within the safe *** copper ions release and ROS production were suggested as the main antibacterial ***,Ti-Cu sintered alloys are promising materials for dental and orthopedic implants.

关键词： Titanium-copper alloy Antibacterial Dental implant Ti_(2)Cu Copper release

Hydrothermal Synthesis and Crystal Structure of Iron Molybdophosphate Fe[Mo_6O_(12)(OH)_3(H_2PO_4)(HPO_4)_2(PO_4)]_2- [Fe(2,2′-bipy)(H_2O)_2]_2[Fe(2,2′-bipy)_3]_2·6H_2O

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Chinese Journal of Structural Chemistry 2005年第10期24卷 1117-1122页

作者： GUO Hong-xu LIU Shi-xiong Department of Chemistry Fuzhou University Fuzhou 350002 China Department of Chemistry Zhangzhou Teachers College Zhangzhou 363000 China State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of Matter The Chinese Academy of Sciences Fuzhou Fujian 350002 China

A molybdenum（V） phosphate supported by iron coordination complexes, Fe[Mo6O12（OH）3（H2PO4）（HPO4）2（PO4）]2[Fe（2,2′-bipy）（H2O）2]2[Fe（2,2′-bipy）3]2·6H2O （bipy = 2,2′-bipyridine） 1, has been synthesized by hydrothermal synthesis and characterized. The title complex crystallizes in the monoclinic system, space group P21/c with a = 14.0005（8）, b = 25.5229（12）, c = 17.9956（9） A, β = 103.470（2）°, V= 6253.5（6） A^3, Z= 2, Mr = 4114.03, Dc = 2.185 g/cm^3, F（000） = 4040, μ = 1.931 mm^-1, R = 0.0438 and wR = 0. 1168. The structure of the title polyoxometalate anion is based on a centrosymmetrical cluster Fe[Mo6O2（OH）3（H2PO4）（HPO4）2（PO4）]2 supported by two [Fe（2,2′-bipy）（H2O）2] subunits. The 2D network is formed through intermolecular hydrogen bonds.

关键词： molybdophosphate iron complex hydrothermal synthesis crystal structure