Lubrication in strip cold rolling process

A lubrication model was developed for explaining how to form an oil film in the deformation zone, predicting the film thickness and determining the characteristics of lubrication in the strip rolling process, combined with the knowledge of hydrodynamic lubrication and rolling theorievS. Various mineral oils with viscosities from 0.032 to 1.6 Pa·s were used to obtain different film thicknesses in the strip cold rolling. Results from the experiment and calculation show that the oil film forming in hydrodynamic lubrication is up to the bit angle and a higher rolling speed or a higher rolling oil viscosity. The mechanism of mechanical entrainment always affects ihe film thickness lhat increases with the rolling oil viscosity increasing or the reduction rate decreasing in rolling.     

Analysis on performance and test of a new type of ultra-high pressure pipe joint

Analysis as well as application of ultra-high pressure hydraulic system and elements has become a trend. The structure and operation principle of a new type of ultra-high pressure pipe joint is introduced. The structure of the new type of ultra-high pressure pipe joint is simple and is easy to be produced. The finite element model on two working conditions( preload condition with 30 N·m torque and static-loading condition with 70 MPa pressure) is built and computed. The width of contact area,the equivalent stress status,as well as the contact pressure status are plotted and analyzed. According to the national standard,test on air-tightness,blasting,and cyclic endurance is conducted and the results show that the new type of ultra-high pressure pipe joint has the sealability for ultra-high pressure up to 70 MPa,and the DN6 ultra-high pressure pipe joint can provide effective seal under70 MPa fluid pressure. The research can provide a thinking and method on designing ultra-high pressure pipe joint and push forward the development of ultra-high pressure hydraulic system.     

Experimental and LES investigation of flame propagation in a hydrogen/air mixture in a combustion vessel

This work presents an experimental and numerical investigation of premixed flame propagation in a hydrogen/air mixture in a closed combustion vessel. In the experiment, high-speed schlieren video photography and pressure sensor are used to examine the flame dynamics and pressure transient. In the numerical study, a large eddy simulation （LES） based on a RNG sub-grid approach and a LES combustion model is applied to reproduce experi- mental observations. The effects of four physical phenomena on the burning velocity are considered in the combustion model, and the impact of grid type on the combustion dynamics is examined in the LES calculations. The flame experiences four stages both in experiment and LES calculations with structured and unstructured grids, i.e., spherical flame, finger-shaped flame, flame with its skirt in contact with the sidewalls, and tulip-shaped flame. The flame speed and pressure in the vessel develop with periodical oscillations in both the experiment and LES simulations due to the interaction of flame front with pressure wave. The numerical simulations compare well with the detailed experimental measurements, especially in term of the flame shape and position, pressure build-up, and periodical oscillation behaviors. The LES combustion model is successfully validated against the bench-scale experiment. It is put into evidence that mesh type has an impact to a certain extent on the numerical combustion dynamics, and the LES calculation on structured grid canpredict the flame dynamics and pressure rise more accu- rately than that on unstructured grid with the same mesh resolution. The flame shape is more asymmetrical in the LES on an unstructured grid than that on a structured grid, and both the flame speed and the pressure rise at the later flame stage are underestimated in the LES on the unstructured grid.     

Structural Optimization of Damping Groove Based on Valve Plate Dynamic Cavitation Response Model

To reduce cavitation occurring on valve plate of piston pump,an optimization design method was introduced to quantitively analyze the accurate relationship between structural jet groove parameters and cavitation. Using the computational fluid dynamics（ CFD） method,the absorbing and discharging processes in piston pump were simulated dynamically. The damping groove＇s structure effects on both jet angle and pressure shock were analyzed visually with a series of different parametrical grooves. By establishing parametrical damping groove model,the piston pumps＇ dynamic analysis was integrated with CFD analysis,experimental design and approximation model, etc. The mathematical model of plunger pressure during oil back period,jet angle and structural parameters of damping groove were established in the form of second-order response surface method（ RSM） model. The damping groove structure of valve plate was optimized on the basis of the RSM model. Test data shows that the anti-cavitation performance of optimized valve plate was obviously improved. And this method provides theoretical foundation for the structure design of damping groove.     

Numerical Computation in Airflow Field of Compact Spinning with Pneumatic Groove

In compact spinning with pneumatic groove,the computational fluid dynamic model,computed with parallel technologies Fluent 6.3,is developed to simulate the flow field in condensing zone with 3D computational fluid dynamic (CFD) technology.Flowing state,distribution rules of static pressure,and velocity in condensing zone are characterized and analyzed.The results show that the fiber bundle in compact spinning with pneumatic groove is compacted by airflow and the shape of the pneumatic groove,and the static pressure in condensing zone is negative,as well as the velocity of airflow in condensing zone is not zero.The fluctuation frequencies of the static pressure and velocity near the bottom of the pneumatic groove are relatively higher,and the number of the fluctuation is equal to that of the round holes in condensing zone.     

Mixed Lubrication Analysis and Experiment Validation of Internal Combustion Piston Skirt

A mixed lubrication model was established for piston skirt lubrication. The mathematical model developed in this paper incorporates governing equations of motion with average Reynolds equation. This model considers the surface roughness and profile, The corresponding computer program can be used to calculate oscillatory motion of piston during the entire trajectory, which has the excellent convergence.In addition, a set of equipment, which adopt the laser induced fluorescent method, was developed to measure the oil film thickness between the piston and the bore.     

A Theoretical Analysis of Torque and Superlubric Motion in Bilayer Graphene Disks

To identify the relation between torque and superlubric motion, we investigate the interlayer sliding behavior of two graphene disks with numerical computation methods. The potential energy, lateral force and torque between the top and bottom graphene disks, which are associated with misfit angle, translational displacement and interlayer distance, are analyzed. The results show that the rotation of the top disk is feeble for commensurate state, but it is difficult to realize superlubricity due to the lateral force fluctuating remarkably. For incommensurate state, the flake exhibits vanishing torque approaching to zero only for partial sliding directions. The superlubricity between the top and bottom disks will be eliminated due to torque-induced reorientation along other sliding directions. Whether for commensurate or incommensurate contact, the amplitudes of the lateral force(516 p N and 13 p N, respectively) are in qualitative agreement with experimental observation(typically 250 p N and 50 p N, respectively). It shows that the interlayer torque is insensitive to the top disk size with incommensurate contact. The results suggest that the superlubric motion of graphene disk can be controlled by adjusting the torque.     

Analysis of contact melting around a horizontal elliptical cylinder heat source

The process of △T-driven contact melting of the solid phase change material (PCM) around an horizontal elliptical cylinder heat source is analyzed. Aiming at the problem existed in the published literature, namely the thickness of boundary layer tends to be infinite at = 90o, and considering the difference of normal angle between the horizontal elliptical cylinder surface and the solid-liquid interface of PCM, a new mathematic model is proposed, and the fundamental equations for the melting process are derived with the film theory. The new pressure distribution inside the boundary layer, the variation law of normal angle of the solid-liquid interface, the thickness of the boundary layer and the relationship between the melting velocity and resultant force are obtained. The solutions of the fundamental equations under different elliptical compression coefficients are analyzed and discussed. It is found that the thickness of the boundary layer obtained by the new model is a finite value and accords with the experimental result at = 90o.     

Wet Transfer Model of Woven Fabric

To investigate wet permeability of woven fabric, a wet transfer model of woven fabric is built up and by means of the model, the main factors which have significant influences on its wet permeability function, including liquid/ material contact angle, fiber diameter, fiber cross-section configuration, the number of fibers, yarn＇s twisting angle and woven density, are discussed. Finally it is derived from the argument that optimal design of wet transfer function of woven fabric can be obtained.     

Analysis of contact melting around a horizontal elliptical cylinder heat source

The process of AT-driven contact melting of the solid phase change material （PCM） around a horizontal elliptical cylinder heat source is analyzed. Aiming at the problem existed in the published literature, namely the thickness of boundary layer tends to be infinite at φ = 90°, and considering the difference of normal angle between the horizontal elliptical cylinder surface and the solid-liquid interface of PCM, a new mathematic model is proposed, and the fundamental equations for the melting process are derived with the film theory. The new pressure distribution inside the boundary layer, the variation law of normal angle of the solid-liquid interface, the thickness of the boundary layer and the relationship between the melting velocity and resultant force are obtained. The solutions of the fundamental equations under different elliptical compression coefficients are analyzed and discussed. It is found that the thickness of the boundary layer obtained by the new model is a finite value and accords with the experimental result at φ = 90°.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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