钢绞线丝间变形与感应加热效果数学模型的研究

根据Hertz(赫兹)接触理论结合钢绞线的结构特性推导了丝间变形的计算方法,采用该方法计算钢绞线感应加热过程中丝间接触面宽度的大小,为建立精确的钢绞线感应加热有限元模型提供了一种新方法.利用有限元分析法计算钢绞线感应加热温度值,得到不同电流密度和频率下的温度数据.通过对温度数据进行回归分析,采用平均相对误差来评价多个回归模型拟合程度的优劣,建立了感应加热效果的最优数学模型.该模型为应用经典控制理论实现钢绞线感应加热温度控制提供了理论依据.     

高速激光作用下薄膜的瞬态温升过程及其非平衡热物理性质

本文报道了薄膜非平衡热物性实验研究工作的最新进展,建立了0.1μs脉冲二氧化碳激光高速加热系统、高速光电测长系统及高速红外辐射测温系统,测量系统响应时间可达0.1μs.应用此系统测量了室温范围微秒量级的温度变化过程,在此基础上测量了50μm薄膜的热扩散率,并且观测到瞬态激光加热后薄膜试样的瞬态温升与膨胀的不同步变化.     

煤粒热解通用模型(Fu-Zhang模型)

本文提出了与现在其它模型不同的煤粒热解的通用模型。其挥发份析出的反应动力学参数E和K不随煤种变化,仅是煤粒终温T_∞和加热速率的函数,并找到了E(或K)与T_∞之间的通用关系。该模型得到了16种煤种的实验数据的验证。结果表明,该模型较为准确地预报了在各种加热条件下,各种煤粒直径的不同煤种挥发份析出的过程。     

青藏高原加热作用对夏季东亚大气环流影响的初步模拟实验

青藏高原夏季的加热作用对东亚大气环流有很大影响,过去从天气学角度对这问题有过不少研究,本文主要用流体力学模拟试验的方法进行了初步研究。 从模拟三种不同基本流场的试验中初步看出:青藏高压的形成主要在于耸立在对流层中部的高原加热作用,这种加热作用使中、下层产生巨大的辐合,高空产生巨大的辐散,高原上空西风带的北撤、高原南面东风带的建立、高原上空高压和高原上热低压的建立以及季风经圈环流的形成等现象,都有内在的联系,其关键在于高原的加热作用。西南季风的形成和活动也与高原加热有密切联系,随着高原加热量的增强,在实验中还可以看到高原东侧的切变线北移,因此青藏高原的加热作用对我国夏季雨带北移也有一定的影响。高原表面上的热量主要通过中、小尺度的对流性系统输送给大气,并维持高原大型环流的运转。     

热毛细振荡对流的实验研究

本文用实验的方法研究了半浮区液桥中由定常流向振荡流转捩的过程。发展了两种不接触诊断方法,测量了液桥自由面发生振动时的临界Marangoni数的分布。对于上壁加热和下壁加热两种情况,分别得到了实验结果,这些结果与Rayleigh不稳定性的理论预计相符。本文还讨论了液桥胖瘦程度对产生振荡流的敏感关系,从而表明自由面附近压力分布的重要性。本文的实验是在小液桥中进行的,其Bond数远小于1,因此可模拟微重力环境中的实验情况。     

家用储水式电热水器的温度设定问题研究

针对家用储水式电热水器洗澡用水的温度设定问题,首先讨论了在非出水和出水两种模式下,热水器温度和加热功率变化与水温、加热时间、加热能耗及出水量的关系,在合理假设下,基于热平衡原理获得能量变化的微分方程模型;其次,基于模型,以某城市为例,分析在不同环境温度、两种模式下的电量消耗情况,进一步,考虑在不同季节电源一直开启时,构建了以积分形式的耗电量为目标函数的优化模型,通过算法求解得到既满足一个人随时洗澡又使电量消耗最小的温度;最后研究了在冬季,实现既能使电量消耗较少,同时使第二个洗澡人等待加热时间也较小的双目标优化问题,求解获得热水器最佳设定温度和最优加热等待时间.     

盛夏青藏高原低涡发生发展的初步研究

本文应用斜压适应和高原加热作用的原理,研究了高原北侧低涡发展东移时高层辐散的形成和维持机制.认为高原西南部大的地气温差通过湍流和对流加热对流层大气后,经西南气流输向高原东北部,促使高原上200毫巴暖脊发展,脊顶西风急流增强,在强西风中心东南侧形成超地转风.当下层为准或次地转风时,则在该区产生超热成风,通过温度场向流场热成风调整适应后,出现暖平流.高空冷槽东移又不断破坏适应过程,使超热成风区及其派生的暖平流东移增强,凝结加热促使暖脊进一步发展,高层位势增高,变压风使高空辐散区东移加强.文中还定性地讨论了高原低涡发展的能源和能量转换方式.据此,我们认为高原低涡的预报方案既要考虑高原近地面生涡高频区的局地热力条件,又要根据长波位置预报外来影响系统的移动和发展.     

微波合成BaTiO3加热机制及反应产物的显微结构研究

采用2450MHz微波源、TE₁₀₃单模腔的加热方式合成电子工业广泛应用的BaTiO_3,探讨微波合成的加热机制,其主要影响因素包括合成体系的介电性质和保温结构,研究合成体系的介电性质及它们对材料加热的影响。在低温阶段,TiO₂和BaCO₃对合成体系的升温速率的贡献相接近;在高温阶段,TiO₂的贡献大,同时产物对升温有较大的影响。微波加热与常规合成加热方式有明显的不同。采用微波合成在1 100℃保温3min即可使合成反应完全,且产物的颗粒细小,粒度分布窄,结晶度好,对微波合成工艺对产物相结构,显微结构的影响进行详细研究。     

抛物型方程未知边界问题

在研究传热或扩散问题时,我们通常假定在整个过程中物体的物理和化学性质是不变的,例如在研究金属杆的传热问题时,我们假定在整个热量迁移的过程中既不发生晶体结构的变化,也不产生熔解凝固等现象。因此所有出现在微分方程中的一些物理量,我们都至少要求它们是时间和空间变量的连续函数。但是事实上纯铁在加热到910℃以后就会吸收一部分所谓再结晶潜热而引起晶体结构的转变,件随着这样的转变,物体的传热系     

壁面加热湍流耗散率标度指数测量的实验研究

对中等雷诺数下壁面常温和壁面加热的平板湍流边界层中速度和温度粗粒化的耗散率结构函数标度指数进行了实验测量.用热线风速仪测量了风洞中壁面常温和加热的平板湍流边界层中不同法向位置的流向速度分量和温度的时间序列信号,研究了由于湍流边界层近壁区域相干结构的存在而导致的非各向同性、非均匀性对湍流耗散率结构函数标度指数的影响,研究发现,中等雷诺数下壁面加热的边界条件和剪切湍流的平均速度梯度对速度和温度耗散率结构函数的标度指数没有影响,均匀各向同性湍流的耗散率结构函数标度指数的层次结构模型对壁面加热平板湍流边界层的速度和温度耗散率结构函数的标度指数也是适用的.     

Thermal deformation of oriented irradiated polyethylene and ethylene-propylene copolymer under uniaxial tensile load

The deformation of preoriented irradiated polyethylene and ethylenepropylene copolymer has been investigated under conditions of multiple heating above the melting point of the crystals and subsequent cooling with application of a constant uniaxial tensile load. The specimens are found to shorten during heating and to lengthen during cooling. However, this process is not reversible and irreversible elongation of the specimen occurs during each temperature cycle (heating and cooling).Mekhanika Polimerov. Vol. 3, No. 3, pp. 392–394, 1967     

Real-time nonlinear global state observer design for solar heating systems

Nowadays it is important to investigate and develop solar water heating systems as an environmentally friendly technology. For this reason we introduce a physically-based nonlinear mathematical model that applies to a wide range of solar heating systems. In commercial solar heating systems not all state variables are monitored by direct measurements, since some of them may be technically difficult or expensive to measure. For a better monitoring and more efficient control of the system it may be useful to estimate the unmeasured state variables.As a novelty, we apply a global nonlinear state observer to a solar domestic water heating system. The state observer has been established relatively recently in the field of control theory. The state observer we worked out enables us to estimate the unmeasured state variables in real-time. This observer is global in the sense that it works starting from any initial state. A further contribution of this work is a rather general algorithm for the practical application of the real-time estimation process, and we also give bounds of the estimation error and a practical method to decrease this error.Comparing calculated and measured values for a real particular solar heating system, we justify the usability of the state observer and the estimation process.On the basis of measured data, we show that the nonlinear mathematical model corresponding to the applied nonlinear observer is more accurate than the linear model corresponding to the classical linear Luenberger-type observer, so it is reasonable to apply the nonlinear observer.     

Multiple crane scheduling in a batch annealing process with no-delay constraints for machine unloading

In this work, we focus on the scheduling of multi-crane operations in an iron and steel enterprise for a two-stage batch annealing process. The first stage is the heating process, and the second stage is the cooling process. To start the heating (cooling) stage, a special machine called a furnace (cooler) must be loaded. The real constraints of no-delay machine unloading are defined as follows: once the heating (cooling) is completed, the furnace (cooler) must be unloaded by crane immediately. The goal is to schedule limited machines (furnaces and coolers) operated by multiple cranes to minimize the completion time of the last annealed coil (makespan). We formulate a mixed-integer linear programming model to address this problem. Certain feasible properties are identified to avoid crane conflicts and ensure that the machine unloading no-delay constraints are met. Based on these necessary conditions, we then present a heuristic algorithm with running time in connection with the number of cranes, coils and machines. A lower bound to the problem is also developed. Through theoretical analysis, we show the worst-case bound of our heuristic algorithm. The average performances of the solution approaches are computationally evaluated. The computational results show that the proposed heuristic algorithm is capable of generating good quality solutions.     

Waer of composite thin-walled structural elements with consideration of thermal effects

The contact problem on interaction of rigid stamps with anisotropic plates with regard to wear and the corresponding frictional heating is considered. The procedure developed is based on the reduction of the governing equation to a system of Volterra integral equations of the second kind. The numerical analysis allows us to study the effects of both the anisotropic thermoelastic characteristics of materials and the nature of the interaction of the contact-pair elements on the wear process.Pidstryhach Institute of Applied Problems of Mechanics and Mathematics, National Academy of Sciences of Ukraine, Lviv, Ukraine. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 3, pp. 309–318, May–June, 1999.     

Microwave heating of carbon-coated ceramic fibres: A mathematical model

The microwave heating of a thinly carbon-coated ceramic fibreis modelled and analysed in the small Biot number regime. Theelectric field is assumed known and uniform throughout the cross-section,and constant along the axis of the cylinder. The mathematicalmodel consists of a nonlinear heat equation with an idealizedsource term that models the thin carbon coating and simplifiedreaction kinetics. The analysis yields an asymptotic approximationof the heating process on two time scales. The first capturesthe initial heating of the carbon coating and the ceramic, andthe carbon reaction, while the second determines the long timebehaviour of the sample. The results show a qualitative relationshipbetween the coating thickness and the final temperature of thefibre. If the coating thickness is not uniform along the fibreaxis, then the model explains the mechanism for the formationand propagation of hot-spots.     

The heating of the solar corona by the resonant absorption of alfven waves

In this paper, upward propagating Magnetoacoustic waves in an ideal atmosphere are considered. It is shown that the magnetic field creates a nonabsorbing reflecting layer. An equation for the resonance is derived, which shows that resonance may occur for many values of the magnetic field and of the frequency if the wavelength is matched to the strength of the magnetic field. At the resonance frequencies the values of the magnetic and kinetic energies will increase to very large values, and this may account for the heating process. Consequently, for large β-plasma the mechanism for coronal heating will be acoustic.     

Calculation of the residual stresses and strains in wound reinforced-plastic products

A method is proposed for determining the residual stresses and strains in wound glass-reinforced plastic products. The fabrication process is divided into five stages: winding, heating polymerization, cooling, and removal from the mandrel. The initial stresses that develop during winding and the subsequent stress increment associated with heating are taken into account. Polymerization is treated as a process during which the mechanical and thermophysical properties of the material change. Chemical shrinkage of the resin and its filtration through the fiberglass are disregarded. Equations are derived for the residual radial and peripheral stresses in the finished product, for the residual change in inside diameter, and for the temperature at which the product is released from the mandrel during the cooling process. The experimental data relating to two types of wound products are discussed. The results of a computation of the residual stresses and the residual changes in inside diameter are compared with the experimental data.Moscow Power Engineering Institute. Translated from Mekhanika Polimerov, Vol. 5, No. 1, pp. 134–139, January–February, 1969.     

Determining the Thermal Mode Setting Parameters Based on Output Data

Differential Equations - We consider a mathematical model of the process of heating a cylindrical domain by embedded heat sources under the assumption that heat exchange with the environment occurs...     

Pattern formation in microwave heated ceramics: cylinders and slabs

Analyses of microwave heating of a thin ceramic cylinder and a thin ceramic slab in a single mode, highly resonant cavityare presented. Realistic assumptions regarding the effectiveelectrical conductivity, thermal parameters, and physical dimensionsare adhered to throughout. Consequently, the models developedherein incorporate most of the features of actual experiments.They incorporate both the effects of cavity detuning and alocal electric field perturbation on the heating process. The models presented take the form of one- and two-dimensionalreaction–diffusion equations which contain a functionaland an inhomogeneous source term for the cylinder and slab,respectively. The development of these equations is the product of a systematic modelling process that involves S-matrix theory,a small Biot number asymptotic analysis, and a matched asymptotic analysis of a non-standard electromagnetic scattering problem.The one-dimensional equation for the cylinder reveals boththe mathematical structure and physical mechanism for the formationof hot-spots. The two-dimensional equation supports a hot stripe pattern, due to preferential electromagnetic heating, whichbecomes unstable and evolves into an oval-like spot. Accuratenumerical methods which approximate the solutions of theseequations and their stability are presented and these agreequalitatively with experiments and predict observed trends. Received 1 June, 1999. ⁺ antoine@mip.ups-tlse.fr