Fabrication and abrasive wear properties of metal matrix composites reinforced with three-dimensional network structure

Reticulated polyurethane was chosen as the preceramic material for preparing the porous preform using the replication process. The immersing and sintering processes were each performed twice for fabricating a high-porosity and super-strong skeleton. The aluminum magnesium matrix composites reinforced with three-dimensional network structure were prepared using the infiltration technique by pressure assisting and vacuum driving. Light interfacial reactions have played a profitable role in most of the ceramic-metal systems. The metal matrix composites interpenetrated with the ceramic phase have a higher wear resistance than the metal matrix phase. The volume fraction of ceramic reinforcement has a significant effect on the abrasive wear, and the wear rate can be decreased with the increase of the volume fraction of reinforcement.

LOW-DIMENSIONAL STRUCTURES:SP ARSE CODING FOR NEURONAL ACTIVITY

Neuronal ensemble activity codes working memory.In this work,we developed a neuronal ensemble sparse coding method,which can effectively reduce the dimension of the neuronal activity and express neural coding.Multichannel spike trains were recorded in rat prefrontal cortex during a work memory task in Y-maze.As discretesignals,spikes were transferred into cont inuous signals by estinating entropy.Then the normalized continuous signals were decomposed via non-negative sparse met hod.The non-negative components were extracted to reconstruct a low-dimensional ensemble,while none of the feature components were missed.The results showed that,for well-trained rats,neuronal ensemble activities in the prefrontal cortex changed dynamically during the.working memory task.And the neuronal ensemble is more explicit via using non-negative sparse coding.Our results indicate that the neuronal ensemblesparse coding method can effectively reduce the dimnension of neuronal activity and it is a useful tool to express neural coding.

SYNTHESIS AND CRYSTAL STRUCTURE OF THE FIRST THREE DIMENSIONAL NETWORK CU(Ⅱ) COMPLEX BRIDGED BY BOTH OXAMIDE AND AZIDE

A novel three dimensional network complex polymer [Cu_4(oxen)_2(N_3)_3]_n(ClO_4)_n·2nH_2O, where oxen is N,N' -bis(2-aminoethyl)oxamide dianion, has been synthesized. It crystallizes in triclinic system, space group P, with a=11.486(2), b=11.706(3), c=12.291(3) , α=77.42(2), β=67.59(2), γ=77.96(2)°, and z=2. The least-square refinements converged at R=0.047, with 3416 observed unique reflections. The complex has a pronounced three-dimensional character and can be viewed as the tetranuclear asymmetric repeating units through inversion and translation operations to extend a three-dimensional network. The structure of Cu_4 asymmetric unit consists of two square planar and two square pyramidal Cu central atoms linked by both azide ligands in end-on and end-to-end bonding modes, and oxamidate bridge in trans conformation.

Effect of Steel Slag and Granulated Blast-furnace Slag on the Mechanical Strength and Pore Structure of Cement Composites

Reuse of solid industrial wastes is an effective approach to develop low-carbon construction materials. This paper examines how two materials, steel slag（ST） and granulated blast-furnace slag（SL） impact the mechanical performance and pore structure of cement-based systems. Analysis was done on the variations of the porosity, pore size, and pore volume distribution with the curing age and replacement content, and the fractal dimensions of pore surfaces. The results suggested that systems with both supplementary materials had lower early strengths than pure cement, but could generally surpass pure cement paste after 90 d; higher SL content was particularly helpful for boosting the late strengths. The addition of ST increased the porosities and mean pore sizes at each age, and both increased with ST content; SL was helpful for decreasing the system＇s late porosity（especially harmless pores below 20 nm）; The lowest porosity and mean pore size were obtained with 20% SL. Both systems had notably fractal characteristics on pore surfaces, with ST systems showing the highest dimensions at 10% ST, and SL systems at 20% SL. Compressive strength displayed a significant linear increase with fractal dimension.

Numerical study on three-dimensional flow field of continuously rotating detonation in a toroidal chamber

Gaseous detonation propagating in a toroidal chamber was numerically studied for hydrogen/oxygen/nitrogen mixtures. The numerical method used is based on the three-dimensional Euler equations with detailed finiterate chemistry. The results show that the calculated streak picture is in qualitative agreement with the picture recorded by a high speed streak camera from published literature. The three-dimensional flow field induced by a continuously rotating detonation was visualized and distinctive features of the rotating detonations were clearly depicted. Owing to the unconfined character of detonation wavelet, a deficit of detonation parameters was observed. Due to the effects of wall geometries, the strength of the outside detonation front is stronger than that of the inside portion. The detonation thus propagates with a constant circular velocity. Numerical simulation also shows three-dimensional rotating detonation structures, which display specific feature of the detonation- shock combined wave. Discrete burning gas pockets are formed due to instability of the discontinuity. It is believed that the present study could give an insight into the interest- ing properties of the continuously rotating detonation, and is thus beneficial to the design of continuous detonation propulsion systems.

Separate Analysis of Remote Sensing Information of Structures of Different Geological Periods and Quantitative Study of Corresponding Tectonic Stress Fields

The structural feature shown on a remote sensing image is a synthetic result ofcombination of the deformations produced during the entire geological history of an area.Therefore, the respective tectonic stress field of each of the different stages in the complexdeformation of an area can be reconstructed in three steps: (1) geological structures formed atdifferent times are distinguished in remote sensing image interpretation; (2) structuraldeformation fields at different stages are determined by analyzing relationships betweenmicrostructures (joints and fractures) and the related structures (folds and faults); and (3)tectonic stress fields at different stages are respectively recovered through a study of the featuresof structural deformation fields in different periods. Circular structures and related circlular and radial joints are correlated in space to con-cealed structural rises. The authors propose a new method for establishing a natural model ofthe concealed structural rises and calculating the tectonic stress field by using quantitative dataof the remote sensing information of circular structures and related linear structures.

A research on the geothermal structure in Yanqing-Huailai Basin and its neighbouring region

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Stability and structural dimension of access mechanized panel

To acquire a knowledge of the stress-strain state in the process of mining beforehand, a numerical method was used to simulate the stoping process of access mechanized panel mining in No. 3 ore-body of Tonglushan mine; and for the sake of obtaining better stability, the optimal panel dimension and access stoping sequence were researched. The results show that the integral stability of the mechanized panel of No. 3 ore-body is passable in the process of winning at full level height; the stability of panel tends to be worse gradually with continuous increasing of panel width; and the better width of access panel in No.3 ore-body is less than 52 m. It is indicated that 3D elasto-plastic finite element method can make a satisfactory study of numerical simulation on the panel stability and its structural dimension in the test for the upward access mechanized-panel mining. The results of the theoretical calculation and analysis accord with the actual situation from the field ground pressure monitoring.

Structural Dimensions Analysis of Service Employees' Innovation Behavior Based on Structural Equation Model

In order to know about the essence of service employees' innovation behavior, the service employees' innovation behavior scale based on their unique characteristics is designed. Data were collected from high-star hospitalities. Through the issuance and the collection of questionnaires, the scale is verified to have good reliability and validity by SPSS software analysis. Meanwhile,the structural equation model( SEM) is suited for testing structural dimensions of service employees' innovation behavior. The results showed that service employees' innovation behavior could be decomposed into a four-dimensional structure,namely innovation orientation, ideas generation, innovation implementation and innovation practice. In addition,there are significant differences in service employees' innovation behavior about subjects' gender,position,education background and years of working.

Quality Management Model Embodying Circular Economy and Sustainable Manufacture - Quality Concept Models Based on a Chinese Traditional Cultural Principle

Based on circular economy and sustainable manufacture theories, the drawbacks in the existing quality management models are analyzed. The requests that satisfy the big system 'environment-society-economy' are summarized to build up a model. A Chinese traditional cultural principle is applied and the relevant contents are sublimated as the platform to set up the model. The new quality management concept models are put forward: 'T-D-R' three dimension structures and 'ecological quality loop' model, from which the new quality concepts are formed. The paper elaborates the contents and the process of setting up the models. The big system quality problems can be handled by the new quality concept and model that are validated in practice.

Dimensionality Reducing from Three-dimensional RbLu5Te8 to Two-dimensional CsMnGdTe3:Syntheses,Crystal and Electronic Structures

Two new rare-earth metal chalcogenides,namely RbLu5Te8 and CsMnGdTe3,have been successfully synthesized under high-temperature solid-state reaction conditions and structurally characterized by single-crystal X-ray diffraction analysis.RbLu5Te8 belongs to the monoclinic space group C2/m(no.12)with two formula units in a unit cell:a=22.075(5),b=4.2987(8),c=10.588(2)A,β=103.89(2)°,V=975.4(4)A3,whereas CsMnGdTe3 crystallizes in the orthorhombic space group Cmcm(no.63)with four formula units in a unit cell:a=4.4872(8),b=16.769(3),c=11.807(2)A and V=888.4(3)A3.In the structure of RbLu5Te8,face-,edgeand vertex-sharing[LuTe6]octahedra are interconnected to produce a three-dimensional(3D)framework with Rb^+lying in the tunnels.The crystal structure of CsMnGdTe3 consists of two-dimensional(2D)[MnGdTe3]^–layers of edge-and vertex-sharing[GdTe6]octahedra with Mn atoms filling the tetrahedral interstices,which stack along the b-axis.The Cs atoms are located between the[MnGdTe3]^–layers and surrounded by eight Te atoms to form a[CsTe8]bicapped trigonal prism.Moreover,theoretical studies have aided the understanding of their electronic structures.

An ultrasound-triggered cation chelation and reassembly route to one-dimensional Ni-rich cathode material enabling fast charging and stable cycling of Li-ion batteries

Ni-rich oxides,LiNixMnyCozO2(NMC),are among leading candidates for cathode materials in Li-ion batteries.However,they are mostly fabricated by coprecipitation approach under complex conditions,which usually produces large secondary particles composed of aggregated primary particles.Undesirable cation mixing and crack propagation upon cycling block ion and electron transport,result in fast capacity fading and poor rate capability.Herein,we present an ultrasound-triggered cation chelation and reassembly route for synthesizing one-dimensional precursor with homogeneous element distribution at the atomic level.This process is accomplished by the synergistic combination of ultrasound and surfactant,which can disperse reactants and remove hydration shells surrounding cations so as to accelerate chelating reaction,and then separate and assemble chelates into one dimensional structure.The whole synthesis time is only 20 min(8.9 min of ultrasonic working time)in an open vessel under natural ambient conditions.One-dimensional LiNi0.6Mn0.2Co0.2O2 has a high reversible capacity(184 mAh·g^−1 at 0.1 C)and long cycling stability(95.1%and 82.4%capacity retention for 100 and 1000 cycles,respectively).The short charging time of 76 s is realized at super high current rate of 20 C,which is very important to improve the competitiveness of electric vehicles relative to fuel vehicles.Our synthetic approach can provide a general strategy for the growth of mixed-metal-EDTA chelate precursors by changing the feeding ratio of Ni2+,Mn2+and Co2+cations in reaction for fabricating NMC cathode materials with other compositions.

Overlapped groupwise dimension reduction

Existing groupwise dimension reduction requires given group structure to be non-overlapped. This confines its application scope. We aim at groupwise dimension reduction with overlapped group structure or even unknown group structure. To this end, existing groupwise dimension reduction concept is extended to be compatible with overlapped group structure. Then, the envelope method is ameliorated to deal with overlapped groupwise dimension reduction. As an application, Gaussian graphic model is employed to estimate the structure between predictors when the group structure is not given, and the amended envelope method is used for groupwise dimension reduction with graphic structure. Furthermore, the rationale of the proposed estimation procedure is explained at the population level and the estimation consistency is proved at the sample level. Finally, the finite sample performance of the proposed methods is examined via numerical simulations and a body fat data analysis.

Advances of graphene application in electrode materials for lithium ion batteries

The demands for better energy storage devices due to fast development of electric vehicles(EVs) have raised increasing attention on lithium ion batteries(LIBs) with high power and energy densities. In this paper, we provide an overview of recent progress in graphene-based electrode materials. Graphene with its great electrical conductivity and mechanical properties have apparently improved the performance of traditional electrode materials. The methods and electrochemical properties of advanced graphene composite as cathode and anode for LIBs are reviewed. Two novel kinds of graphene hybrid materials are specially highlighted: three-dimensional porous and flexible binder-free graphene-based materials. Challenges for LIBs and future research trend in the development of high-performance electrode materials are further discussed.

Morphology design of microporous organic polymers and their potential applications:an overview

Microporous organic polymers(MOPs) have attracted considerable research interest because of their well-defined porosity,high surface area, lightweight nature, and tunable surface chemistry. The morphology of MOPs are demonstrated to play a significant role in various applications although limited examples manifesting the importance of the MOP morphology in numerous applications have been reported. This review summarizes the recent progress in the design of MOPs using different techniques, including hard and soft template and direct synthesis methods. In addition, their applications, which possibly attribute to their shape, are discussed. Furthermore, the advantages and disadvantages of different methods are discussed, as well as their development and future challenges.

Growing CoNi nanoalloy@N-doped carbon nanotubes on MXene sheets for excellent microwave absorption

Recently,two-dimensional MXene materials have attracted numerous attention in electromagnetic wave shielding/absorption.Hybridizing magnetic materials and constructing multi-dimensional structures in MXene is highly beneficial to improve electromagnetic wave absorption properties.Herein,we demonstrate a strategy for in situ growing 0 D CoNi nanoalloy-encapsulated 1 D N-doped carbon nanotubes on a2 D Ti_(3)C_(2)T_(x)MXene sheet through an electrostatic assembly process followed by a high-temperature pyrolysis process.The resultant 201-structured MXene-CoNi@N-doped carbon nanotube(MXene-CoNi@NCNT)composites displayed high surface areas(55.6-103.7 m^(2)/g),moderate magnetism(19.8-24.6 emu/g),and excellent thermal oxidation stabilities(≥ 307℃).In addition,the unique 2 D/0 D/1 D architectures entrusted the composites with abundant interfaces,various defects,and numerous nitrogen dopants.Taking advantage of the special 201 structure and the existence of both magnetic and dielectric loss,the MXeneCoNi@NCNT composite showed great impedance matching and strong attenuation performance.A strong reflection loss of-55.3 dB was achieved when the coating thickness was 2.1 mm,and a wide effective absorption bandwidth of 4.3 GHz was achieved at a thickness of 1.5 mm,much superior to that of similar absorbers.This work demonstrates a novel strategy for designing electromagnetic wave absorbers with magnetic and dielectric losses accompanied by multiple dimensional structures.

On spline approximation of sliced inverse regression

The dimension reduction is helpful and often necessary in exploring the nonparametric regression structure.In this area,Sliced inverse regression (SIR) is a promising tool to estimate the central dimension reduction (CDR) space.To estimate the kernel matrix of the SIR,we herein suggest the spline approximation using the least squares regression.The heteroscedasticity can be incorporated well by introducing an appropriate weight function.The root-n asymptotic normality can be achieved for a wide range choice of knots.This is essentially analogous to the kernel estimation.Moreover, we also propose a modified Bayes information criterion (BIC) based on the eigenvalues of the SIR matrix.This modified BIC can be applied to any form of the SIR and other related methods.The methodology and some of the practical issues are illustrated through the horse mussel data.Empirical studies evidence the performance of our proposed spline approximation by comparison of the existing estimators.

Examining factors affect supply chain collaboration in Jordanian organizations

This research examines the dimensions of a supply chain collaboration(SCC)process in Jordanian partners and measures the effectiveness of its implementation using two structural models.The first model examines the relationship between the SCC process and relevant structural and social dimensions,including:governance(GO),administrative structure(AD),organization autonomy(OA),norms(NO),and mutuality(MU).The second model studies the effectiveness of SCC implementation via five dimensions,involving:information sharing(IS),resource sharing(RS),goal congruence(GC),decision synchronization(DS),and joint knowledge(JK)creation.A total of 95 organizations are surveyed and then the collected data are analyzed.Results reveal that GO,AD,OA,NO,and MU significantly affect SSC,while AD and MU have the largest effects.On the other hand,SCC implementation is significantly affected by DS and IS,while partially affected by RS.Finally,JK and GC show no significant effects on SCC implementation.In conclusion,although Jordanian collaborative partners successfully established SCC relations,still more efforts should directed to strengthen SCC implementation.