平面应力状态下混凝土的热弹塑性积分方案

在高温状态下的屈服函数是温度和塑性应变的函数,塑性应变不仅与应力状态有关,还取决于温度。如果采用常规的计算方法,如径向返回法,需要更多的迭代运算,造成计算效率不高。另外,对于单轴受力情况,每个时间步内的温度路径也是很难确定。采用平面应力状态下混凝土常用的屈服函数Drucker-Prager准则,给出了相应的高温热弹塑性积分方案的初值问题表达式,可采用Runge-Kutta法对其积分,较好地解决了前面两个问题。采用基于S-R分解原理的更新拖带坐标有限元法,通过实际编程计算得出,该积分方案可靠、精度高。

球面上的Riesz位势型积分算子的L^p(Ω_n)和Lipα有界性

对n维球面Ωn定义的Riesz位势型积分算子研究了它的LP（Ωn）和Lipa有界性。

浅析熵的物理意义及两个常见热力学过程中熵增的计算

“熵”这个概念容易让人感觉晦涩难懂,而一些常见热力学过程中熵增 的计算更是让人无从着手．本文从波耳兹曼熵和克劳修斯熵两个角度浅析了熵的定 义及统计意义,还根据熵的可加性计算了两个典型的相变过程和热传导过程热力学 系统的熵增,并对计算结果进行了讨论．对于一些实际的不可逆过程,尤其是热传导 过程,熵增可采用假设一可逆过程求热温比积分的方法,对每一小部分依次与温差非 常小的恒温热源接触,温差无限小的热传导过程可视为可逆过程．

会员积分:拿什么能换你心动

第三方会员积分管理公司擦亮了商家和会员的眼睛,使积分又'动'了起来。2011年,美国商家通过会员卡发行的积分价值达到480亿美元,其中的三分之一,即160亿美元是没有兑换的;美国共有21亿的会员,平均每个家庭拥有18.4个会员卡,

李氏砭法刮痧治疗脾虚湿蕴手足湿疹的应用分析

目的探究分析李氏砭法刮痧治疗脾虚湿蕴手足湿疹的应用。方法设定此次研究的时间在2021年6月至2022年6月,邀请院内的36例脾虚湿蕴手足湿疹患者参与到此次研究的过程中之中,并以随机的分组的方式将患者分为对照组以及观察组。对对照组中的患者采用西药治疗结合针灸治疗的方式进行干预;对观察组中的患者采用李氏砭法刮痧治疗的方式进行干预。在完成治疗之后,对比对照组以及观察组所取得的治疗效果、反复发作情况、血清睾酮指标、治疗前以及治疗后的皮损积分、瘙痒症状、中医湿热证候次症积分以及患者对于最终治疗效果的满意度。结果在患者完成所有治疗之后,通过整理分析治疗前后所得的数据发现,观察组在取得的治疗效果、反复发作情况、血清睾酮指标、皮损积分、瘙痒症状、中医湿热证候次症积分以及患者对于最终治疗效果的满意度方面,相比于对照组,均存在明显的优势(P<0.05),差异具有统计学意义。结论在对脾虚湿蕴手足湿疹患者进行治疗的过程中,采用李氏砭法刮痧的治疗方式对患者进行治疗,能够取得优良的治疗效果,同时能够显著的改善患者的反复发作情况、血清睾酮指标、皮损积分、瘙痒症状、中医湿热证候次症积分以及患者对于最终治疗效果的满意度,在实际应用的过程中具有优良的效果,在今后对脾虚湿蕴手足湿疹类型患者的治疗过程中,可参照本次研究的治疗方式,进而保障最终的治疗效果。

Direct Heat Integration of Independent Processes

The properties of matched streams, the simultaneous operation time, and the distance between integrated processes, are the main factors which determine whether the direct integration is feasible or not. According to whether such synthetic integration is economically better than the separate integration of each process, a mathematical formulation is established. The retrofit of reforming and arene processes in a certain petrochemical factory, which are independent each other, is chosen as a case study. By only considering the simultaneous operation time, two retrofit designs are proposed: one is that each of the two processes is separately integrated by itself, and the other is that the two processes are integrated comprehensively. Under different simultaneous operation hours, the energy-saving effects and the economic profits of the two designs are calculated, and furthermore, the critical simultaneous operation time for direct heat integration of the two processes is obtained. When the actual simultaneous operation time of the two processes is longer than the critical value, the direct heat integration of the two processes is better economically, and otherwise the separate heat integration for each process should be considered.

Microstructures and properties of Al-45%Si alloy prepared by liquid-solid separation process and spray deposition

The microstructures and properties of A1-45%Si alloy prepared by liquid-solid separation （LSS） process and spray deposition （SD） were studied. The results show that the size, shape and distribution of the primary Si phase have different influence on the properties of alloys. Comparing with the Si particles with irregular shape, fine size and continuous distribution in SD alloy, the primary Si phase in LSS alloy is sphere-like, coarse and surrounded by the continuous AI matrix. The microstructure features of LSS alloy are beneficial to the higher thermal conductivity and lower thermal expansion coefficient at room temperature. The fine Si particle in SD alloy is advantageous to improving the mechanical properties. The increasing rates of thermal expansion coefficient with temperature are influenced by the distribution of the Si particles, where a lower rate is obtained in SD alloy with continuous Si particles. The agreement of thermal expansion coefficient with the model in LSS alloy differs from that in the SD alloy because of the different microstructure characteristics.

Cracked elastic substrate strip with functionally graded coating under thermal-mechanical loading

This paper investigates the functionally graded coating bonded to an elastic strip with a crack under thermal- mechanical loading. Considering some new boundary conditions, it is assumed that the temperature drop across the crack surface is the result of the thermal conductivity index which controls heat conduction through the crack region. By the Fourier transforms, the thermal-elastic mixed boundary value problems are reduced to a system of singular integral equations which can be approximately solved by applying the Chebyshev polynomials. The numerical computation methods for the temperature, the displacement field and the thermal stress intensity factors （TSIFs） are presented. The normal temperature distributions （NTD） with different parameters along the crack surface are analyzed by numerical examples. The influence of the crack position and the thermal-elastic non- homogeneous parameters on the TSIFs of modes I and 11 at the crack tip is presented. Results show that the variation of the thickness of the graded coating has a significant effect on the temperature jump across the crack surfaces when keeping the thickness of the substrate constant, and the thickness of functionally graded material （FGM） coating has a significant effect on the crack in the substrate. The results can be expected to be used for the purpose of gaining better understanding of the thermal-mechanical behavior of graded coatings.

Operator Fredholm Integration Equation in Intermediate Coordinate-Momentum Representation and Its Analogue to Thermo Conduction Equation

Using the technique of integration within an ordered product （IWOP） of operators we construct intermediate coordinate-momentum representation, with which we build a type of operator Fredholm integration equation that is an operator generalization of the solution of thermo conduction equation. Then we seach for the solution of operator Fredholm integration equations, which provides us with a new approach for deriving some operator identities.

Integrability of N-Component Bariev Model Under Open Boundary Conditions

N-component Bariev model for correlated hopping under open boundary conditions in one dimension is studied in the framework of Bethe ansatz method. The energy spectrum and the related Bethe ansatz equations are obtained.

Excess Molar Volume, Viscosity and Heat Capacity for the Binary Mixture of p-Xylene and Acetic Acid at Different Temperatures

Experimental densities, viscosities and heat capacities atdifferent temperatures were presented over the entire range of molefraction for the binary mixture of p-xylene and acetic acid. Densityvalues were used in the determination of excess molar volumes, V^E.At the same time, the excess viscosity and excess molar heatcapacities were calculated. The values of V^E, η~E and c^E_p werefitted to the Redlich-Kister equation. Good agreements were observed.The excess molar volumes are positive with a large maximum valuelocated in the central concentration range.

Resolving double-sided inverse heat conduction problem using calibration integral equation method

In this paper, a novel calibration integral equation is derived for resolving double-sided, two-probe inverse heat conduction problem of surface heat flux estimation. In contrast to the conventional inverse heat conduction techniques, this calibration approach does not require explicit input of the probe locations, thermophysical properties of the host material and temperature sensor parameters related to thermal contact resistance, sensor capacitance and conductive lead losses. All those parameters and properties are inherently contained in the calibration framework in terms of Volterra integral equation of the first kind. The Laplace transform technique is applied and the frequency domain manipulations of the heat equation are performed for deriving the calibration integral equation. Due to the ill-posed nature, regularization is required for the inverse heat conduction problem, a future-time method or singular value decomposition (SVD) can be used for stabilizing the ill-posed Volterra integral equation of the first kind.

Use of ANSYS for Thermal Analysis in Mass Concrete

With the increasing development of Brazil in recent years, major engineering construction works have been designed and built, partieutarly those involving large volumes of mass concrete, such as in the case of dams. Mass concrete, due to its large size and volume, presents a considerable temperature rise caused by cement grain hydration. This temperature rise can be sufficient to cause concrete crack and/or cracking, which may lead to serious problems. In this paper, we sought to study heat generation and temperature field in mass concrete through ANSYS software, which uses finite element method to analyze the problem. This program allows temperatures to be checked for different concrete ages. With that, it is possible to evaluate the temperatures obtained and the factors influencing the results in a short period of time at a low cost. With the help of the software, it is possible to check the temperatures for different concrete properties by analyzing them on different concreting days. Therefore, it was possible to establish that the properties of the concrete directly influence the temperature evolution phenomenon.

Heat Transfer Performance of a Multi-heat Pipe Using Graphene Oxide/Water Nanofluid

A multi-heat pipe is a device for heat transmission. It is composed of a heating section, a cooling section and an adiabatic section. The heating and cooling sections are the same and both are connected by four circular parallel tubes. This experimental study is performed to investigate heat transfer performance of a multi-heat pipe in the vertical orientation using pure water and GO （graphene oxide）/water nanofluid. GO/water nanofluids were synthesized by the modified Hummers method with 0.05%, 0.1%, 0.15%, and 0.2% volume concentrations. The thermal performance has been investigated with varying heat flux in the range of 10-30 W and 100% fill charge ratio. Wall temperature, thermal resistance, and heat transfer coefficient of the heat pipe are measured and compared with those for the heat pipe using pure water. The experimental results show that the evaporator wall temperature with GO nanofluid is lower than that of the base fluid. Also, the heat pipe that charged with nanofluids showed lower thermal resistance compared with pure water. Heat transfer enhancement is caused by suspended nanoparticles and is pronounced with the increase in particle volume fraction.

Experimental study on gas explosion suppression based on ferrocene

In order to study the gas explosion suppression performance based on ferrocene, the self-constructed experimental facility was used to accomplish the experiment of gas explosion suppression. By means of thermogravimetric analysis, the thermal characteristics of ferrocene have been gotten and the gas explosion suppression mechanism of ferrocene has been analyzed. The results show that ferrocene had good effects on gas explosion suppression, and the explosion pressure and flame propagation speed declined obviously. When ferrocene concentration is 0.08 g/L and methane volume concentration is 9.5%, the maximum explosion overpressure and maximum flame propagation speed of methane-air respectively decreased by about 59.5% and 19.6%, respectively. TG and DSC curves showed that the mass loss of ferrocene consists of two processes, which are sublimation and lattice fracture. The temperature of mass loss ranged from 128 ℃ to 230 ℃. The results showed profoundly theoretical significance to gas explosion suppression by ferrocene in coal mines.

The First Principle Formula of the Relativistic Heat Conductivity of Coulomb Electronic Plasmas

Making use of the relativistic BBGKY technique,the relativistic generalization of Landau collision integral is obtained.Furthermore,we calculate the relativistic hydrodynamic modes up to the second order in the hydrodynamic wave number.Combining Résibois' method,we present the first principle formula of the relativistic heat conductivity of Coulomb electronic plasmas for low-order corrections.

Numerical simulation on boiling heat transfer of evaporation cooling in a billet reheating furnace

The boiling heat transfer of evaporation cooling in a billet reheating furnace was simulated.The results indicate that the bubbles easily aggregate inside of the elbow and upper side of the horizontal regions in theπshaped support tubes.The circulation velocity increasing helps to improve the uniformity of vapor distribution and decrease the difference of vapor volume fraction between upper and down at end of the horizontal sections.With the increase of circulation velocity,the resistance loss and the circulation ratio both increase,but the former will decrease with the increase of work pressure.

A nonlinear explicit dynamic GBT formulation for modeling impact response of thin-walled steel members

A nonlinear explicit dynamic finite element formulation based on the generalized beam theory(GBT)is proposed and developed to simulate the dynamic responses of prismatic thin-walled steel members under transverse impulsive loads.Considering the rate strengthening and thermal softening effects on member impact behavior,a modified Cowper-Symonds model for constructional steels is utilized.The element displacement field is built upon the superposition of GBT cross-section deformation modes,so arbitrary deformations such as cross-section distortions,local buckling and warping shear can all be involved by the proposed model.The amplitude function of each cross-section deformation mode is approximated by the cubic non-uniform B-spline basis functions.The Kirchhoff s thin-plate assumption is utilized in the construction of the bending related displacements.The Green-Lagrange strain tensor and the second Piola-Kirchhoff(PK2)stress tensor are employed to measure deformations and stresses at any material point,where stresses are assumed to be in plane-stress state.In order to verify the effectiveness of the proposed GBT model,three numerical cases involving impulsive loading of the thin-walled parts are given.The GBT results are compared with those of the Ls-Dyna shell finite element.It is shown that the proposed model and the shell finite element analysis has equivalent accuracy in displacement and stress.Moreover,the proposed model is much more computationally efficient and structurally clearer than the shell finite elements.

针刺治疗绝经过渡期绝经相关症状的临床研究

目的:客观评价针刺对绝经过渡期(MT)绝经相关症状的疗效以及针感得气对疗效的影响。方法:将90例患者随机分配到针刺组(30例)、安慰针组(30例)和穴位浅刺组(30例)。采用平均24h烘热积分、绝经症状评价量表(MRS)作为主要评价指标进行评价。结果:13组患者的平均24h烘热积分、MRS量表得分经多元方差分析,组间差异均有统计学意义(P<0.05)。23组患者平均24h烘热积分各时点两两比较的结果显示,针刺组与穴位浅刺组比较,差异无统计学意义;针刺组、穴位浅刺组分别与安慰针组比较,差异均有统计学意义(P<0.05)。33组患者MRS量表各时点两两比较,治疗第4周,针刺组与安慰针组比较,差异有统计学意义(P<0.05),穴位浅刺组分别与针刺组、安慰针组比较,差异均无统计学意义;其余各时点两两比较均有统计学差异(P<0.05),其中针刺组降分幅度最大,浅刺组次之,安慰针组最小。结论:针刺治疗MT绝经相关症状是一种有效安全的方法;针刺得气与否可影响针刺的疗效。

Analysis of flow and heat transfer characteristics of micro-pin fin heat sink using silver nanofluids

Silver nanofluids with three different volume fractions are prepared by a one-step chemical reduction method(Ultra-sound-assisted Membrane Reaction(UAMR)).The convective heat transfer and friction characteristics of silver nanofluid in micro-pin fin heat sink are investigated experimentally.The results indicate that the pressure drops of nanofluids with different volume fractions have little difference.Compared to the base fluid(polyvinylpyrrolidone(PVP) solution),the pressure drop of nanofluids increases slightly at the same volume flow rate.When the flow rate is small,the increment is not obvious.The in-troduction of surfactant increases the fluid viscosity,so the pressure drops of nanofluids are larger than those of pure water,under the same flow rate.However,the maximum difference is no more than 10%.The volume fraction of silver nanoparticles significantly affects the convection heat transfer coefficient of micro-pin fin heat sink.The presence of nanoparticles improves significantly the heat transfer performance.However,high viscosity of the nanofluids hinders the heat transfer strengthening effect of nanofluids.In the present work,when the volume fraction of silver particles reaches to 0.012%,the thermal resistance of nanofluid gradually becomes lower than that of deionized water,which indicates the integrated heat transfer enhancement of nanofluids.