Effect of boundary conditions on shakedown analysis of heterogeneous materials

The determination of the ultimate load-bearing capacity of structures made of elastoplastic heterogeneous materials under varying loads is of great importance for engineering analysis and design. Therefore, it is necessary to accurately predict the shakedown domains of these materials. The static shakedown theorem, also known as Melan's theorem, is a fundamental method used to predict the shakedown domains of structures and materials. Within this method, a key aspect lies in the construction and application of an appropriate self-equilibrium stress field(SSF). In the structural shakedown analysis, the SSF is typically constructed by governing equations that satisfy no external force(NEF) boundary conditions. However, we discover that directly applying these governing equations is not suitable for the shakedown analysis of heterogeneous materials. Researchers must consider the requirements imposed by the Hill-Mandel condition for boundary conditions and the physical significance of representative volume elements(RVEs). This paper addresses this issue and demonstrates that the sizes of SSFs vary under different boundary conditions, such as uniform displacement boundary conditions(DBCs), uniform traction boundary conditions(TBCs), and periodic boundary conditions(PBCs). As a result, significant discrepancies arise in the predicted shakedown domain sizes of heterogeneous materials. Built on the demonstrated relationship between SSFs under different boundary conditions, this study explores the conservative relationships among different shakedown domains, and provides proof of the relationship between the elastic limit(EL) factors and the shakedown loading factors under the loading domain of two load vertices. By utilizing numerical examples, we highlight the conservatism present in certain results reported in the existing literature. Among the investigated boundary conditions, the obtained shakedown domain is the most conservative under TBCs.Conversely, utilizing PBCs to construct an SSF for the shakedown analysis leads to less conservative lower bounds, indicating that PBCs should be employed as the preferred boundary conditions for the shakedown analysis of heterogeneous materials.

Evaluations and Suggestions about Effect of Weather in Guangxi on Rice Production

[Objective] The paper aims to study the effect of weather on rice production in Guangxi. [Method] The authors evaluated the effect of weather and weather disasters in Guangxi on rice production by comparison and analysis in terms of temperature,rain and sunlight in 2009. [Result] The study summarized the main favorable and unfavorable weather conditions of rice growth,and proposed the measures and suggestions to tend to interest and avoid harm on rice production in Guangxi. [Conclusion] This study provides references to the evaluations about effect of weather in Guangxi on rice production and suggestions on how to reduce weather disasters influence and ensure rice production security.

Mixed convective heat and mass transfer analysis for peristaltic transport in an asymmetric channel with Soret and Dufour effects

The present investigation addresses the simultaneous effects of heat and mass transfer in the mixed convection peristaltic flow of viscous fluid in an asymmetric channel. The channel walls exhibit the convective boundary conditions. In addition, the effects due to Soret and Dufour are taken into consideration. Resulting problems are solved for the series solutions. Numerical values of heat and mass transfer rates are displayed and studied. Results indicate that the concentration and temperature of the fluid increase whereas the mass transfer rate at the wall decreases with increase of the mass transfer Biot number. Furthermore, it is observed that the temperature decreases with the increase of the heat transfer Biot number.

The effects of process conditions on the plasma characteristic in radio-frequency capacitively coupled SiH_4/NH_3/N_2 plasmas: Two-dimensional simulations

A two-dimensional （2D） fluid model is presented to study the behavior of silicon plasma mixed with SiH4 , N2 , and NH3 in a radio-frequency capacitively coupled plasma （CCP） reactor. The plasma–wall interaction （including the deposition） is modeled by using surface reaction coefficients. In the present paper we try to identify, by numerical simulations, the effect of variations of the process parameters on the plasma properties. It is found from our simulations that by increasing the gas pressure and the discharge gap, the electron density profile shape changes continuously from an edge-high to a center-high, thus the thin films become more uniform. Moreover, as the N2 /NH3 ratio increases from 6/13 to 10/9, the hydrogen content can be significantly decreased, without decreasing the electron density significantly.

Effective Boundary Conditions for the Heat Equation with Interior Inclusion

Of concern is the scenario of a heat equation on a domain that contains a thin layer,on which the thermal conductivity is drastically different from that in the bulk.The multi-scales in the spatial variable and the thermal conductivity lead to computational difficulties,so we may think of the thin layer as a thickless surface,on which we impose"effective boundary conditions"(EBCs).These boundary conditions not only ease the computational burden,but also reveal the effect of the inclusion.In this paper,by considering the asymptotic behavior of the heat equation with interior inclusion subject to Dirichlet boundary condition,as the thickness of the thin layer shrinks,we derive,on a closed curve inside a two-dimensional domain,EBCs which include a Poisson equation on the curve,and a non-local one.It turns out that the EBCs depend on the magnitude of the thermal conductivity in the thin layer,compared to the reciprocal of its thickness.

EFFECTS OF PREPARATOIN CONDITIONS ON THE KINETIC PROPERTIES OF COMPLEX-RESINS

The effects of the reaction temperature, the crosslinking degree of the matrix, the pore-forming agent and the initial concentration of PVA on the kinetic properties of the complex-resins were investigated. The ion-exchange rate of the complex-resin for L-lysine chlorate was three-fold that of 001×8 resin and two-fold that of D61 resin.

Effect of Deformation Condition on Axial Compressive Precision Forming Process of Tube with Curling Die

The effect of the deformation condition on the axial compressive precision forming process of tube with curling die was investigated by using a rigid-plastic FEM. The results show that the forming accuracy depends mainly on geometric condition rp/d0, little on tube material properties and friction condition; the relative gap △/2rp of double-walled tubes obtained decreases with Increasing rp/d0, and there is a parameter k for a given to/do or rp/t0, when rp/d0 >k, △/2rp< 1, otherwise △/2rp>1.

Study on Restrike Phenomena for 40.5-kV Vacuum Circuit Breakers

When interrupting short circuit fault by 40.5-kV vacuum circuit breakers, it is significant to eliminate multiple restrike phenomena, which occur frequently and result in high overvoltage and even interruption failure. A synthetic circuit that can supply a DC recovery voltage after current zero was used to study multiple restrike phenomena in switching. Some key factors including breaking current, clearance between open contacts, electrode structure and contact material, which may affect restrike characteristics, were studied. Under various clearances, the statistical probability of restrike was obtained. As a result, the best scope of clearance between open contacts was found. The performance of CuCr50/50 and CuCr75/25 material were compared. Two kinds of electrode structures, namely 1/2 coil structure and cup-shaped axial magnetic structure, were tested. After a high-current interruption, conditioning effoct was realized and the probability of restrike decreased.

Effective condition numbers and small sample statistical condition estimation for the generalized Sylvester equation

Abstract In this paper, we investigate the effective condition numbers for the generalized Sylvester equation （AX - YB, DX - YE） = （C,F）, where A,D ∈ Rm×m B,E ∈ Rn×n and C,F ∈ Rm×n. We apply the small sample statistical method for the fast condition estimation of the generalized Sylvester equation, which requires （9（m2n ＋ mn2） flops, comparing with （-O（m3 ＋ n3） flops for the generalized Schur and generalized Hessenberg- Schur methods for solving the generalized Sylvester equation. Numerical examples illustrate the sharpness of our perturbation bounds.

The effects of bonding conditions on the propagation of acoustic waves along a cased borehole

Based on the wave equations in cylindrically layered structures and boundary conditions, the frequency equation for axisymmetric guided waves and the expression for sound fields in a cased borehole excited by a monopole or multipole source have been derived. The synthetic full waveforms excited by the monopole and dipole source are simulated using a real axis integration and FFT method. According to the axisymmetric guided wave modes, the synthetic full waveforms and the effects of the interface conditions on the sound field in a cased borehole have been analyzed and studied respectively. Numerical results indicate that it may be difficult to distinguish well bonded, poorly bonded or unbonded intermediate layer between the steel pipe and formation if only using a monopole source or dipole source. To properly estimate the case boundary conditions, a combination of monopole source logging with dipole source logging is suggested.

EFFECTS OF HYPOXIC ENDOTHELIAL CELL CONDITIONED MEDIUM ON PROLIFERATION AND COLLAGEN SYNTHESIS OF SMOOTH MUSCLE CELLS AND INHIBITORY EFFECTS OF RADIX SALVIAE MILTIORRHIZAE

The effects of hypoxic endothelial cell conditioned medium (HECCM) on proliferation and collagen synthesis of cultured porcine pulmonary arterial smooth muscle cells (PASMCs) were studied by 3H-thymidine (3H-TdR) and 3H-proline incorporations, image analysis for determination of DNA content and colorimetric assay using MTT, and the inhibitory effects of radix salviae miltiorrhizae (RSM) on them were also investigated. The results showed that HECCM could induce enhancement of the enzymatic activity of mitochondria, increase of the nucleic DNA content and increases of the 3H-TdR and 3H-proline incorporations in PASMCs. The 3H-proline incorporation in PASMCs cultured in HECCM was 1.83 times as much as that cultured in normoxic endothelial cell conditioned medium (NECCM). Compared with the control, Chinese herb medicine RSM could inhibit the proliferation of PASMCs cultured in HECCM and decrease the 3H-prolinc incorporation in PASMCs cultured in both HECCM and NECCM (P< 0.001). However, RSM had no ef fects on the nucleic DNA content and 3H-TdR incorporation into DNA of PASMCs cultured in NECCM. It suggests that hypoxia may stimulate the endothelia to synthesize and secrete some cytokines which can stimulate the proliferation and the synthesis of collagen of PASMCs and RSM can inhibit this process.

Conditions for magnetic and electronic properties of ultrathin Ni–Fe hydroxide nanosheets as catalysts:a DFT+U study

The effects of cation ordering and surface compensating anions on the magnetic structure and catalytic properties of unilamellar Ni-Fe hydroxide nanosheets are studied by using the density functional theory （DFT） plus U method. Fe-segregation in the nanosheets yields magnetic domains with different spin alignments, while the surface compensating anions affect the local moments and valence states of the Fe atoms. The two conditions do not radically change the super-exchange nature of interactions between the paramagnetic metal centers, hut facilitate the formation of various magnetic superlattices in the nanosheets. The calculated free energy change of the intermediates shows that the most stable magnetic structure of Ni-Fe hydrox- ide nanosheets exhibits superior catalytic activity towards oxygen reduction/evolution reactions, which is indicative of magnetic catalyst. This is due to the cycle transition between Fe2＋ and Fe~~ ions in the reactions, which determines the sequence of cleavage of the O-H bond and the release of the OH group, controlling the rate-limiting steps of the reaction. The relationship of magnetism and catalytic activity of Ni-Fe hydroxide nanosheets is established by the valence state change of the Fe ions, which will be helpful to open the way for the design of hydroxide/layered double hydroxides （LDHs）-based magnetic catalysts.

Weather-based interruption prediction in the smart grid utilizing chronological data

This unique study will demonstrate a combined effect of weather parameters on the total number of power distribution interruptions in a region.Based on common weather conditions,a theoretical model can predict interruptions and risk assessment with immediate weather conditions.Using daily and hourly weather data,the created models will predict the number of daily or by-shift interruptions.The weather and environmental conditions to be addressed will include rain,wind,temperature,lightning density,humidity,barometric pressure,snow and ice.Models will be developed to allow broad applications.Statistical and deterministic simulations of the models using the data collected will be conducted by employing existing software,and the results will be used to refine the models.Models developed in this study will be used to predict power interruptions in areas that can be readily monitored,thus validating the models.The application has resulted in defining the predicted number of interruptions in a region with a specific confidence level.Reliability is major concern for every utility.Prediction and timely action to minimize the outage duration improves reliability.Use of this predictor model with existing smart grid self-healing technology is proposed.

Radiation efects on MHD stagnation point flow of nano fluid towards a stretching surface with convective boundary condition

The aim of the present paper is to study the numerical solutions of the steady MHD two dimensional stagnation point flow of an incompressible nano fluid towards a stretching cylinder.The effects of radiation and convective boundary condition are also taken into account.The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis.The resulting nonlinear momentum,energy and nano particle equations are simplifed using similarity transformations.Numerical solutions have been obtained for the velocity,temperature and nanoparticle fraction profles.The influence of physical parameters on the velocity,temperature,nanoparticle fraction,rates of heat transfer and nanoparticle fraction are shown graphically.

Can Nano-Particle Melt below the Melting Temperature of Its Free Surface Partner?

The phonon thermal contribution to the melting temperature of nano-particles is inspected. The discrete summation of phonon states and its corresponding integration form as an approximation for a nano-particle or for a bulk system have been analyzed. The discrete phonon energy levels of pure size effect and the wave-vector shifts of boundary conditions are investigated in detail. Unlike in macroscopic thermodynamics, the integration volume of zero-mode of phonon for a nano-particle is not zero, and it plays an important role in pure size effect and boundary condition effect. We find that a nano-particle will have a rising melting temperature due to purely finite size effect; a lower melting temperature bound exists for a nano-particle in various environments, and the melting temperature of a nano-particle with free boundary condition reaches this lower bound. We suggest an easy procedure to estimation the melting temperature, in which the zero-mode contribution will be excluded, and only several bulk quantities will be used as input. We would like to emphasize that the quantum effect of discrete energy levels in nano-particles, which is not present in early thermodynamic studies on finite size corrections to melting temperature in small systems, should be included in future researches.

Restricted Additive Schwarz Preconditioner for Elliptic Equations with Jump Coefficients

This paper provides a proof of robustness of the restricted additive Schwarz preconditioner with harmonic overlap(RASHO)for the second order elliptic problems with jump coefficients.By analyzing the eigenvalue distribution of the RASHO preconditioner,we prove that the convergence rate of preconditioned conjugate gradient method with RASHO preconditioner is uniform with respect to the large jump and meshsize.