Effect of particle characteristics on deformation of particle reinforced metal matrix composites

The particle characteristics of 15%SiC particles reinforced metal matrix composites(MMC)made by powder metallurgy route were studied by using a statistical method.In the analysis,the approach for estimation of the characteristics of particles was presented.The study was carried out by using the mathematic software MATLAB to calculate the area and perimeter of each particle, in which the image processing technique was employed.Based on the calculations,the sizes and shape factors of each particle were investigated respectively.Additionally,the finite element model(FEM)was established on the basis of the actual microstructure.The contour plots of von Mises effective stress and strain in matrix and particles were presented in calculations for considering the influence of microstructure on the deformation behavior of MMC.Moreover,the contour maps of the maximum stress of particles and the maximum plastic strain of matrix in the vicinity of particles were introduced respectively.

Transfer matrix method for determination of the natural vibration characteristics of elastically coupled launch vehicle boosters

The analysis of natural vibration characteristics has become one of important steps of the manufacture and dynamic design in the aerospace industry. This paper presents a new scenario called virtual cutting in the context of the transfer matrix method of linear multibody systems closed- loop topology for computing the free vibration characteristics of elastically coupled flexible launch vehicle boosters. In this approach, the coupled system is idealized as a triple-beam system-like structure coupled by linear translational springs, where a non-uniform free-free Euler-Bemoulli beam is used. A large thrust-to-weight ratio leads to large axial accelera- tions that result in an axial inertia load distribution from nose to tail. Consequently, it causes the development of significant compressive forces along the length of the launch vehicle. Therefore, it is important to take into account this effect in the transverse vibration model. This scenario does not need the global dynamics equations of a system, and it has high computational efficiency and low memory requirements. The validity of the presented scenario is achieved through com- parison to other approaches published in the literature.

Influence of matrix physical properties on flow characteristics in dual network model

The tight oil formation develops with microfractures and matrix pores,it is important to study the influence of matrix physical properties on flow characteristics.At first,the representative fracture and matrix samples are selected respectively in the dual media,the fracture and matrix digital rocks are constructed with micro-CT scanning at different resolutions,and the corresponding fracture and matrix pore networks are extracted,respectively.Then,the modified integration method is proposed to build the dual network model containing both fracture and matrix pore-throat elements,while the geometric-topological structure equivalent matrix pores are generated to fill in the skeleton domain of fracture network,the constructed dual network could describe the geometric-topological structure characteristics of fracture and matrix pore-throat simultaneously.At last,by adjusting the matrix pore density and the matrix filling domain factor,a series of dual network models are obtained to analyze the influence of matrix physical properties on flow characteristics in dual-media.It can be seen that the matrix system contributes more to the porosity of the dual media and less to the permeability.With the decrease in matrix pore density,the porosity/permeability contributions of matrix system to dual media keep decreasing,but the decrease is not significant,the oil-water co-flow zone decreases and the irreducible water saturation increases,and the saturation interval dominated by the fluid flow in the fracture keeps increasing.With the decrease in matrix filling domain factor,the porosity/permeability contributions of matrix system to dual media decreases,the oil-water co-flow zone increases and the irreducible water saturation decreases,and the saturation interval dominated by the fluid flow in the fracture keeps increasing.The results can be used to explain the dual-media flow pattern under different matrix types and different fracture control volumes during tight oil production.

Effect of thermal processing and fermentation with Chinese traditional starters on characteristics and allergenicity of wheat matrix

Wheat allergy has become a serious health threat worldwide and its prevalence has increased alarmingly in the past few years.Factors such as food matrix and food processing may alter the structure of wheat proteins,and hence affect its allergenic properties.However,few reports have focused on the influence of Chinese traditional starter fermentation on wheat allergy.In this study,5 starters from different regions of China were used for fermentation,and protein characteristics were monitored by sodium dodecyl sulfate polyacrylamide gel electropheresis,and immunoreactivity analyzed by immunoassay with allergenic serum was obtained from New Zealand white rabbits.The allergenicity of steamed and baked matrices was also evaluated.The results showed that the allergenicity of wheat dough was basically increased at the beginning and then decreased during fermentation,but specific trends depend on different starters.With the progress of fermentation,especially as pH value decreased to 3.0-4.0,the allergenicity decreased significantly.Baking and steaming can reduce the allergenicity of wheat matrix,but fermentation is not a key factor affecting the allergenic activity of proteins.Our results can provide a theoretical basis for controlling wheat allergenicity in food proces sing or producing hypoallergenic food.

Dynamic characteristics of a WPC-comparison of transfer matrix method and FE method

To find the difference in dynamic characteristics between conventional monohull ship and wave penetrating catamaran (WPC), a WPC was taken as an object; its dynamic characteristics were computed by transfer matrix method and finite element method respectively. According to the comparison of the nature frequency results and mode shape results, the fact that FEM method is more suitable to dynamic characteristics analysis of a WPC was pointed out, special features on dynamic characteristics of WPC were given, and some beneficial suggestions are proposed to optimize the strength of a WPC in design period.

THE CHARACTERISTIC POLYNOMIAL ANDEIGENVALUES OF FINILE RIODAN MATRIXTHE CHARACTERISTIC POLYNOMIAL ANDEIGENVALUES OF FINILE RIODAN MATRIX

In this paper we deal with the characteristic polynomial of finite Riodan matix. We giveseveral forms of its explicit expressions. Its applications to combinatorial identities, specially to F-Lidentities, are stated.

Effect of Metal Contact and Rapid Thermal Annealing on Electrical Characteristics of Graphene Matrix

Development of graphene field effect transistors （GFETs） faces a serious challenge of graphene interface to the dielectric material. A single layer of intrinsic graphene has an average sheet resistance of the order of 1-5 kΩ/□. The intrinsic nature of graphene leads to higher contact resistance yielding into the outstanding properties of the material. We design a graphene matrix with minimized sheet resistance of 0.185 kΩ/□ with Ag contacts. The developed matrices on silicon substrates provide a variety of transistor design options for subsequent fabrication. The graphene layer is developed over 400 nm nickel in such a way as to analyze hypersensitive electrical properties of the interface for exfoliation. This work identifies potential of the design in the applicability of few-layer GFETs with less process steps with the help of analyzing the effect of metal contact and post-process anneMing on its electrical fabrication.

An Efficient Algorithm for Calculating Aircraft RCS Based on the Geometrical Characteristics

Taking into account the influences of scatterer geometrical shapes on induced currents, an algorithm, termed the sparse-matrix method （SMM）, is proposed to calculate radar cross section （RCS） of aircraft configuration. Based on the geometrical characteristics and the method of moment （MOM）, the SMM points out that the strong current coupling zone could be predefined according to the shape of scatterers. Two geometrical parameters, the surface curvature and the electrical space between the field position and source position, are deducted to distinguish the dominant current coupling. Then the strong current coupling is computed to construct an impedance matrix having sparse nature, which is solved to compute RCS. The efficiency and feasibility of the SMM are demonstrated by computing electromagnetic scattering of some kinds of shapes such as a cone-sphere with a gap, a bi-arc column and a stealth aircraft configuration. The numerical results show that： （1） the accuracy of SMM is satisfied, as compared with MOM, and the computational time it spends is only about 8% of the MOM; （2） with the electrical space considered, making another allowance for the surface curvature can reduce the computation time by 9.5%.

Pre-stack-texture-based reservoir characteristics and seismic facies analysis

Seismic texture attributes are closely related to seismic facies and reservoir characteristics and are thus widely used in seismic data interpretation.However,information is mislaid in the stacking process when traditional texture attributes are extracted from poststack data,which is detrimental to complex reservoir description.In this study,pre-stack texture attributes are introduced,these attributes can not only capable of precisely depicting the lateral continuity of waveforms between different reflection points but also reflect amplitude versus offset,anisotropy,and heterogeneity in the medium.Due to its strong ability to represent stratigraphies,a pre-stack-data-based seismic facies analysis method is proposed using the selforganizing map algorithm.This method is tested on wide azimuth seismic data from China,and the advantages of pre-stack texture attributes in the description of stratum lateral changes are verified,in addition to the method＇s ability to reveal anisotropy and heterogeneity characteristics.The pre-stack texture classification results effectively distinguish different seismic reflection patterns,thereby providing reliable evidence for use in seismic facies analysis.

Research on the Structural Rigidity Characteristics of a Reconfigurable TBM Thrust Mechanism

To improve the adaptability of TBMs in diverse geological environments,this paper proposes a reconfigurable Type-V thrust mechanism(V-TM)with rearrangeable working states,in which structural stiffness can be automatically altered during operation.Therefore,millions of configurations can be obtained,and thousands of instances of working status per configuration can be set respectively.Nonetheless,the complexity of configurations and diversity of working states contributes to further complications for the structural stiffness algorithm.This results in challenges such as difficulty calculating the payload compliance index and the environment adaptability index.To solve this problem,we use the configuration matrix to describe the relationship between propelling jacks under reconfiguration and adopt pattern vectors to describe the working state of each hydraulic cylinder.Then,both the dynamic compatible equation between propeller forces of the hydraulic cylinders and driving forces,and the kinematic harmonizing equation between the hydraulic cylinder displacements and their deformations are established.Next,we derive the stiffness analytical equation using Hooke’s law and the Jacobian Matrix.The proposed approach provides an effective algorithm to support structural rigidity analysis,and lays a solid theoretical foundation for calculating the performance indexes of the V-TM.We then analyze the rigidity characteristics of typical configurations under different working states,and obtain the main factors affecting structural stiffness of the V-TM.The results show the deviation degree of structural parameters in hydraulic cylinders within the same group,and the working status of propelling jacks.Finally,our constructive conclusions contribute valuable information for matching and optimization by drawing on the factors that affect the structural rigidity of the V-TM.

Alzheimer's disease with sleep insufficiency:a cross-sectional study on correlations among clinical characteristics,orexin,its receptors,and the bloodbrain barrier

Previous studies have shown that reduced sleep duration,sleep fragmentation,and decreased sleep quality in patients with Alzheimer's disease are related to dysfunction in orexin signaling.At the same time,blood-brain barrier disruption is considered an early biomarker of Alzheimer's disease.However,currently no report has examined how changes in orexin signaling relate to changes in the blood-brain barrier of patients who have Alzheimer's disease with sleep insufficiency.This cross-sectional study included 50 patients with Alzheimer's disease who received treatment in 2019 at Beijing Tiantan Hospital.Patients were divided into two groups:those with insufficient sleep(sleep duration≤6 hours,n=19,age 61.58±8.54 years,10 men)and those with normal sleep durations(sleep duration>6 hours,n=31,age 63.19±10.09 years,18 men).Demographic variables were collected to evaluate cognitive function,neuropsychiatric symptoms,and activities of daily living.The levels of orexin,its receptor proteins,and several blood-brain barrier factors were measured in cerebrospinal fluid.Sleep insufficiency was associated with impaired overall cognitive function that spanned multiple cognitive domains.Furthermore,levels of orexin and its receptors were upregulated in the cerebrospinal fluid,and the blood–brain barrier was destroyed.Both these events precipitated each other and accelerated the progression of Alzheimer's disease.These findings describe the clinical characteristics and potential mechanism underlying Alzheimer's disease accompanied by sleep deprivation.Inhibiting the upregulation of elements within the orexin system or preventing the breakdown of the blood-brain barrier could thus be targets for treating Alzheimer's disease.

Computation of Jordan Chains by Generalized Characteristic Matrices

In this paper, we introduce a method to define generalized characteristic matrices of a defective matrix by the common form of Jordan chains. The generalized characteristic matrices can be obtained by solving a system of linear equations and they can be used to compute Jordan basis.

Influence of Axial Loads to Propagation Characteristics of the Elastic Wave in a Non-Uniform Shaft

The vibration propagates through the shaft in the form of elastic waves. The propagation characteristics of the elastic waves are a ected by the axial loads. The influence of the axial loads to the propagation characteristics of the elastic waves is studied in this paper. Firstly, the transfer matrix of the elastic waves for the non-uniform shaft with axial loads is deduced by combining the transfer matrix without axial load and the additional equation caused by the axial load. And then, a numerical method is used to study the influence of the axial load, non-uniformity and the rotating speed to the propagation characteristics of the elastic waves. It’s found that a new Stop Band will appear due to the axial force, and the central frequency of which will decrease as the increase of the force, while the band width of which remains the same. The central frequency of the new Stop Band will also increase as the increase of the cross-section area ratio;however, the rotating speed of the shaft doesn’t a ect the propagation characteristics of the elastic waves obviously. Finally, an experimental rig is built up for further study, even though there are some small local errors, the results of experiments match well with the numerical ones, which indicates the validation of the theoretical results. The result can help to study the influence of the axial load to the dynamics of a non-uniform shaft and help to reveal the vibration propagating mechanism in such a shaft.

THE FRACTURE CHARACTERISTICS OF δ-Al_2O_3/AlALLOY COMPOSITES

The initial location of the crack and the controlling factor of the fracture in the squeeze casting composites δ-Al2 O3/Al-5.5Zn, δ-Al2 O3/Al-5.5Mg and δ-Al2 O3/Al-cSi were studied by microscopic observation and finite element analysis(FEA). The in situ failure processes were obseroed bU the scanning electronic microscope mp. The distributions of stress components along the fiber length in matta, and the tnean axial stresses of fiber and matrix were calculated by three-dimensional elasto-plastic FEA.It is found that the failure modes of short fiber reiwtreed metal matrix composites change with the variations of the micro-structurnl characteristics of composites, such as fiber orientation, matrix strength and intedecial bonding, etc.

Admissible model noise upper bound with constraint of stochastic passage characteristics

In some object tracking systems, the moving object future position is an area （i.e., target area）. It is a successful estimation strategy if the predicted points fall in the target area. If the object makes a sudden maneuvering, the prediction may get out of the target area easily which may make the tracking system lose the object. The aim is to investigate the admissible maximum object maneuvering intensity, which is characterized as model noise variance, for such kind of tracking system. Firstly, the concept of stochastic passage characteristics over the boundary of target area and their relationship with prediction error variance are described. Secondly, the consistency among the indices of regional pole, prediction error variance and stochastic passage characteristics is analyzed. Thirdly, the multi-indices constraints are characterized by a set of bi-linear matrix inequalities （BMIs）. Then, the admissible maximum model noise variance and the satisfactory estimation strategy are presented by iteratively solving linear matrix inequalities （LMIs） to approximate BMIs. Finally, a numerical example is proposed to demonstrate the obtained resuits.

Analysis on Stochastic Passage Characteristics for Gun Barrel in Shooting Domain

Aiming at some weapon systems with shooting domain,the stochastic passage characteristics of the barrel were studied.On the basis of the exact definition of the stochastic passage characteristics,its opportunity-awaiting time,residence time and stochastic passage period were given by using the transition probability matrix,and they all obeyed the geometry distributions.Their means and variances were also derived,and the relations between the time indexes and the structure and parameters of weapon control system were established.Finally,the creditability of the conclusions was verified by the test data of weapon system in proving ground.

Friction and Wear Characteristics of Brush Plating Ni/nano-Al2O3 Composite Coating under Sand-Containing Oil

Ni-matrix composite coating containing AI2O3 nano-particles is prepared by brush plating. The effects of the nano-particles on the microstructure, microhardness and tribological properties of the composite coating under the lubrication of a diesel oil containing sand are investigated. The results show that the microstructure of the composite coating is finer than that of the pure nickel coating due to the codeposition of the nano-particles. When the nano-particle concentration in the electroplating bath reaches 20 g/L, the microhardness, and wear resistance of the composite coating is as much as 1.6 times and 1.3-2.5 times of those of the pure nickel coating respectively. The main hardening mechanism of the composite coating is superfine crystal grain strengthening and dispersion strengthening. The composite coating is characterized by scuffing as it slides against Si3N4 under the present test conditions.

DYNAMIC CHARACTERISTICS ON PRECISION NC LATHE BASED ON MULTI-BODY SYSTEM THEORY

Based on multi-body system theory and the mainshafl system of precision NC lathe as object investigated, it is treated as a coupled rigid-flexible multi-body system which is made up of some rigid and elastic bodies in an especial linking mode. And a dynamic model is established, The problems of computing vibration characteristics are resolved by using multi-body system transfer matrix method, Resutts show that the mainshaft system of NC lathe is in the stable and reliable working area all the time. The method is simple and easy, the idea is clear. In addition, the method can be easily used and popularized in the other multi-body system.

Experimental and Numerical Investigations on Vibration Characteristics of a Loaded Ship Model

In this paper, the vibration characteristics of the structure in the finite fluid domain are analyzed using a coupled finite element method. The added mass matrix is calculated with finite element method （FEM） by 8-node acoustic fluid elements. The vibration characteristics of the structure in the finite fluid domain are calculated combining structure FEM mass matrix. By writing relevant programs, the numerical analysis on vibration characteristics of a submerged cantilever rectangular plate in finite fluid domain and loaded ship model is performed. A modal identification experiment for the loaded ship model in air and in water is conducted and the experiment results verify the reliability of the numerical analysis. The numerical method can be used for further research on vibration characteristics and acoustic radiation problems of the structure in the finite fluid domain.

基于An Soff Matrix分析体育小镇发展策略

An Soff Matrix是企业长期发展营销战略模型,主要基于产品和市场的关系对企业发展策略进行定位。对体育特色小镇发展以模型嵌入的方式即从产品和市场组合的四个战略路径进行探究,体育特色小镇作为产品以消费者需求为基点、特色为要点、融合为创新点进行开发。投资者和消费者都是体育特色小镇的市场,以特色资源引领投资者、带动消费者才能避免产业同质化。体育特色小镇初期以主导性多角化打好基础,紧抓产业聚集要点,中期和后期进行环绕式产业链建设。