食品流变学的进展

本文概述了近年来国内外食品流变学的研究进展，着重讨论了食品物质流变特性测量及分析、食品物质结构与流变特性、食品质构与流变特性的关系等问题，并对食品流变学的发展及国内食品流变学的开展提出了几点浅见。     

电流变学研究进展

电流变学是近年来新兴的一门学科。本文从电流变学的发展概况，电流变流体，电流变效应的机理和电流变体的应用等４个方面对电流变学的概貌做了阐述，力求能准确地反映国际上电流变学的发展现状。     

我国流变学研究最新进展——第2届全国流变学会议(1987年11月15—19日,成都)

会议由中国化学会、中国力学学会流变学委员会召开。出席会议的有各科研单位、高等院校、企业单位、油田、医疗卫生单位、新闻出版部门的代表共232人。共提出报告220篇,按内容分为邀请报告、非牛顿流体力学、粘弹理论和本构方程、固体流变学、流变测量学、工业流变学、高分子加工、多相高分子流变学、高分子流变学、生物流变学10个部分。已于会前编辑出版了第2届全国流变学会议论文详细摘要集《流变学进展》(Ⅱ)(韩式方、吴大诚主编,成都科技大学出版社出版),简要地反映了我国流变学各个方面的最新进展。      

泡沫流动

<正> 1 引言 泡沫是一种有结构的流体。在这种流体中,大大小小的气泡为液体薄膜所分隔,而且连续液相所占的体积分数很小。人们最熟悉的泡沫体系原型,是分散在网络状肥皂泡膜中形状为多面体的空气泡,而浓缩的液-液乳化剂亦呈现出许多与这种泡沫体系相同的特征。在那些能够持久存在的泡沫中,液相总是含有某种表面活化剂。这种活化剂主要聚集在气-液界面上且可使泡膜具有程度不同的稳定性。表面活性,薄膜以及亚稳态泡沫具有的大面积界     

采动岩体的流变与控制技术

指出采矿工程中岩体的稳定性研究焦点是破裂岩体的流变与控制技术,这给固体流变学研究带来严峻挑战和发展良机,本文较为全面地 采矿工程中巷道围岩变形,采场覆岩运动,岩层移动与围岩突出中的流变现象,以及与之相应的传统理论与控制技术,并为岩石流变学研究指出了新的发展方向。     

用小管流变仪对高浓度水煤浆的流变测量

在实验室用自制的小管流变仪对高浓度水煤浆的流变行为进行了实验研究.采用不同长短的管子进行了末端效应修正.采用不同管径的管子进行了滑移效应修正。我们假设高浓度水煤浆是不依赖于时间的流体,根据实验数据得到剪切应力和剪切速率的关系符合 Herschel-Bulkley 模型.     

第1届全国流变学会议

1985年11月11—15日在长沙举行。由中国化学会和中国力学学会联合召开。出席的180名代表来自102个单位,其中大专院校45个,中央和地方研究单位33个(包括中国科学院的7个研究所),工厂、医疗、出版部门单位24个。共提出报告129篇。8篇大会邀请报告总结了国内外流变学的发展及应用现状:流变学的历史和展望;流变学在断裂、冶      

流体测量技术应用于废水处理

流体测量技术是废水处理工程项目设计和技术改进的一个重要手段。本文着重报告了氧化沟现场实测取得的数据和性能分析,如流场中的速度分布,转刷驱动功率以及能耗估算等,提出了改进设计的建议。文中还对相关流量测量方法的工程应用进行了讨论。     

弹塑性流变模型在弹流脂润滑特性分析中的应用

采用自行研制的高速润滑脂拖动力试验装置测量了7007国产润滑脂的拖动力;以7007润滑脂为例,建立了该类高速润滑脂的平均剪切弹性模量和平均极限剪切应力的计算公式,基于Tevaarwerk-Johnson弹塑模型给出了拖动力的计算方法,并分析了其流变特性.结果表明:该润滑脂在本文试验条件下表现出弹塑性,其拖动力的理论预测值与试验测量值具有很好的一致性;所建立的拖动力计算公式可用于指导润滑分析领域的工程计算.     

大型结构变形及形貌摄像测量技术研究进展

船体、机翼、工程建筑等大型结构的变形与形貌的精确测量是实验力学的基本任务之一。摄像测量具有测量精度高、范围大、非接触、可动态测量等优点,是结构形貌与运动测量的重要手段。本文介绍了作者及其所在科研团队近年来利用摄像测量技术在大型结构变形、形貌测量等方面的研究成果和典型应用范例,主要包括：提出折线光路像机链摄像测量方法与技术,用于船体等大型结构,不稳定平台的静态基准转换,以及地下工程、边坡等的多点变形长期动态监测;采用多摄像机联合组网,用于机翼、风电叶片等大型结构形貌与变形的高精度测量;在投影轮廓线辅助下进行多部像机组网,用于对大型堆场三维形貌、料堆体积和高程等的高精度测量等。     

Asymptotic behavior of Toeplitz matrices and determinants

We consider the inverse X _N and determinant D_N(c) of an N×N Toeplitz matrix C_N=[c_i?j] ₀ ^N?1 as N ar∞. Under the condition that there exists a monotonic decreasing summable bound b _n ≧|c _n |+|c _?n |, and that the generating function \(c(\theta ) = \sum\limits_{n = - \infty }^\infty {c_n e^{i{\text{ }}n{\text{ }}\theta } }\) does not vanish, we construct a matrix iterative process which yields (i) explicit asymptotic formulae for the elements of X_N when v(c) = (2π)^?1 [arg{c(2π)}?arg{c(0)}] is zero. Thence we obtain (ii) expressions for the constants, and bounds on the remainder, in the asymptotic formula $$\ln D_N (c) = N{\text{ }}k_0 (c) + E_0 (c) + E_{1,N} (c) + \mathcal{R}_N (c),$$ and (iii) the extension of this formula to the case of general integral v(c). Under certain further conditions the monotonicity of E_1,N+?_N is proved. We discuss various identities for D_N which apply when c(θ) is a rational function of e^iθ and mention a conjecture for D _N when c(θ) has zeros, and is discontinuous with arbitrary v(c).     

GENERALIZED MULTIVARIATE RIDGE REGRESSION ESTIMATE AND CRITERIA Q(e)FOR CHOOSING MATRIX K

When multicollinearity is present in a set of the regression variables,the leastsquare estimate of the regression coefficient tends to be unstable and it may lead toerroneous inference.In this paper,generalized ridge estimateβ(K)of the regression coefficientβ=vec(B)is considered in multivaiate linear regression model.The MSE of the aboveestimate is less than the MSE of the least square estimate by choosing the ridgeparameter matrix K.Moreover,it is pointed out that the Criterion MSE for choosingmatrix K of generalized ridge estimate has several weaknesses.In order to overcomethese weaknesses,a new family of criteria Q(c)is adpoted which includes the criterionMSE and criterion LS as its special case.The good properties of the criteria Q(c)areproved and discussed from theoretical point of view.The statistical meaning of thescale c is explained and the methods of determining c are also given.     

基于新型蠕变仪下的泥岩力学参数时效性研究

岩石在蠕变的过程中其基本力学参数变形模量E、内聚力c和内摩擦角是随时间和应力逐渐弱化的。本文对现行蠕变设备特点进行分析,研制了一套新型的五联单轴蠕变仪,此仪器能够在相同的应力条件下同时进行5个试件的蠕变试验。并且使用该仪器对宝鸡市秦源煤矿泥岩的力学参数E、c、在蠕变试验中的弱化规律进行了研究。提出了把粘塑性应变作为泥岩力学参数弱化的指标,得出了泥岩E、c、随粘塑性应变呈指数衰减的函数关系,并计算了该泥岩破坏时的E、c、。对该泥岩E、c、和粘塑性应变的函数关系式进行了分析,得到了岩石E、c、和应力(σ)以及时间(t)的耦合函数方程,为后续岩石非定常本构模型的研究奠定了基础。
力学参数〓时效性〓蠕变仪〓蠕变试验          
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ON THE CHANGES OF MEANING OF “LI” AND “LIXUE” (“FORCE” AND “MECHANICS” IN CHINESE)1)

在古代中国,“力”字和“力学”一词早就出现了。“力”的含义最初是对“人的力量”的直观描述,后来发展到对一般物体的重力的描述,再到对运动状态原因的描述。本文对“力”字含义的变迁进行了辨析。中国现代“力学”是西学东渐的结果,学科名字的确定过程也有不小的 曲折。通过分析确定“力学”为学科名字的过程,揭示了中国古人对“力学”学科理解的变迁。     

Weakly nonlocal envelope solitary waves: numerical calculations for the Klein-Gordon (φ) equation

“Weakly nonlocal” solitary waves differ from ordinary solitary waves by possessing small amplitude, oscillatory “wings” that extend indefinitely from the large amplitude “core”. Such generalized solitary waves have been discovered in capillarygravity water waves, particle physics models, and geophysical Rossby waves. In this work, we present explicit calculations of weakly nonlocal envelope solitary waves. Each is a sine wave modulated by a slowly-varying “envelope” that itself propagates at the group velocity. Our example is the cubically nonlinear Klein-Gordon equation, which is a model in particle physics (φ⁴ theory) and in electrical engineering (with a different sign). Both cases have weakly nonlocal“breather” solitons. Via the Lorentz invariance, each breather generates a one-parameter family of nonlocal envelope solitary waves. The φ⁴ breather was described and calculated in earlier work. This generates envelope solitons which have “wings” that are (mostly) proportional to the second harmonic of the sinusoidal factor. In this article, we calculate breathers and envelope solitary waves for the second, electrical engineering case. Since these, unlike the φ⁴ waves, contain only odd harmonics, the envelope solitary waves are nonlocal only via the third harmonic.     

Generalized multivariate ridge regression estimate and criteria q(c) for choosing matrixK

When multicollinearity is present in a set of the regression variables, the least square estimate of the regression coefficient tends to be unstable and it may lead to erroneous inference. In this paper, generalized ridge estimate β(K) of the regression coefficient β =vec(B) is considered in multivaiate linear regression model. The MSE of the above estimate is less than the MSE of the least square estimate by choosing the ridge parameter matrix K. Moreover, it is pointed out that the Criterion MSE for choosing matrix K of generalized ridge estimate has several weaknesses. In order to overcome these weaknesses, a new family of criteria Q(c) is adpoted which includes the criterion MSE and criterion LS as its special case. The good properties of the criteria Q(c) are proved and discussed from theoretical point of view. The statistical meaning of the scale c is explained and the methods of determining c are also given. The projects Supported by Natural Science Foundation of Fujian Province     

Experimental and numerical determinations of the initial surface of phase transformation under biaxial loading in some polycrystalline shape-memory alloys

Biaxial proportional loading such as tension (compression)–internal pressure and bi-compression tests are performed on a Cu-Zn-Al and Cu-Al-Be shape memory polycrystals. These tests lead to the experimental determination of the initial surface of phase transformation (austenite→martensite) in the principal stress space (σ₁,σ₂). A first “micro–macro” modeling is performed as follows. Lattice measurements of the cubic austenite and the monoclinic martensite cells are used to determine the “nature” of the phase transformation, i.e. an exact interface between the parent phase and an untwinned martensite variant. The yield surface is obtained by a simple (Sachs constant stress) averaging procedure assuming random texture. A second modeling, performed in the context of the thermodynamics of irreversible processes, consists of a phenomenological approach at the scale of the polycrystal. These two models fit the experimental phase transformation surface well.     

Comparisons of crystal hardening laws in multiple slip

This paper brings together and concisely reviews results from recent analytical investigations on single crystals (variously done alone or with students) in which predictions from different theoretical hardening laws are contrasted and compared with experimental studies. Finitely deforming f.c.c. crystals in both constrained and unconstrained multiple-slip configurations are considered. Four crystal hardening laws are given prominence. Two of these belong to a class of theories in which the physical hardening moduli relating rates-of-change of critical strengths (in the 24 crystallographically equivalent slip systems) to slip-rates are taken as symmetric. These are G.I. Taylor's classic isotropic hardening rule (proposed in 1923), which is almost universally adopted in the metallurgical literature for various approximate analyses of single and poly-crystal deformation, and a 2-parameter modification of Taylor's rule that has an empirical basis in the qualitative features of experimentally determined latent hardening in single slip. The other two hardening laws featured here belong to a class of theories that were introduced in 1977 by this author. This class requires the above moduli to be nonsymmetric and explicity dependent upon the current stress state in such a manner that the following consequences are assured. (1) The deformation-dependent hardening of latent slip systems necessarily develops anisotropically if there is relative rotation of gross material and underlying crystal lattice. (2) The theories admit self-adjoint boundary value problems for crystalline aggregates, hence a variational formulation. (The fact that symmetric physical hardening moduli do not permit variational formulations of polycrystalline problems was shown at the 1972 Warsaw Symposium.) The two members of this class considered here are the original (and simplest p possible) theory of rotation-dependent anisotropy, which was proposed by this author in 1977 and commonly has been referred to as the “simple theory,” and a modification of this theory introduced in 1982 by Peirce, Asaro and Needleman that lies between Taylor's rule and the simple theory in its predictions for finitely deforming f.c.c. crystals. (In a series of five papers during 1977–1979, the simple theory was shown to universally account for the experimental phenomenon of “overshooting” in single slip in both f.c.c. and b.c.c. crystals.) Theoretical results from the various hardening rules are contrasted and compared with finite strain experiments in the metallurgical literature. Both tensile-loaded crystals in 4, 6 and 8-fold symmetry orientations and compressively loaded crystals under conditions of channel die constraint are treated. A postulate of minimum plastic work introduced in 1981 plays a prominent role in the theoretical analyses, in many cases providing a unique solution to the slip system inequalities and deformation constraints (where applicable). The rather remarkable ability of the simple theory to reconcile diverse qualitative features of both constrained and unconstrained finited deformation of f.c.c. crystals is demonstrated. Finally, conditions for total loading (all systems active) in 6-fold symmetry are investigated, and certain concepts regarding the selection of active systems under prescribed straining are critically assessed.     

Fatigue crack growth in high and low strength steel under torsional loading

During loading of a crack in mode III the crack surfaces in contact slide against each other giving rise to friction, abrasion and mutual support, thereby reducing the effective stress at the crack tip (“sliding mode crack closure”). This phenomenon was investigated in a high strength steel (AISI 4340) and in a low strength steel (AISI C1018) in circumferentially notched specimens under pure cyclic torsion and combined loading (cyclic torsion plus static axial load). The influence of sliding mode crack closure on fatigue crack propagation is shown and “true” crack growth values (without the sliding mode crack closure influence) are determined on the basis of an extrapolation procedure. Explanations are given for causes of the various fracture modes observed, such as “factory roof” fracture, macroscopically flat mode III fracture and “lamella” fracture. Finally the scientific and technical importance of sliding mode crack closure is demonstrated.     

A general correlation for the local loss coefficient in Newtonian axisymmetric sudden expansions

Results from numerical simulations and guidance from an approximated corrected-theory, developed by Oliveira and Pinho (1997), (Oliveira, P.J. and Pinho, F.T. 1997. Pressure drop coefficient of laminar Newtonian flow in axisymmetric sudden expansions. Int. J. Heat and Fluid flow 18, 518–529) have been used to arrive at a correlation expressing the irreversible loss coefficient for laminar Newtonian flow in axisymmetric sudden expansions. The correlation is valid for the ranges 1.5 < D₂/D₁ < 4 and 0.5 < Re < 200 with errors of less than 5%, except for 25 < Re < 100 where the error could be as much as 7%. The recirculation bubble length is also presented for the same range of conditions and the pressure recovery coefficient was calculated for Reynolds numbers above 15.