Operating charts for continuous sedimentation IV: limitations for control of dynamic behaviour

The nonlinear behaviour of a one-dimensional idealized model of continuous sedimentation has been investigated in this series of papers. The model is a scalar hyperbolic conservation law with a space-discontinuous flux function and a point source. Parameters in the equation are the two input variables (concentration and flux) and the control variable (a volume flow). The most desired type of solution contains a large concentration discontinuity and is referred to as ‘optimal operation’. Operating charts (concentration-flux diagrams) have proved to be a means for classifying the nonlinear behaviour. In this paper, some fundamental results on the dynamic behaviour are presented, which give information on the limitations of the range of the control variable. When this is used together with the previously introduced optimal control strategies for step inputs, the process can be controlled.     

Re-examine the relationship between patents and Tobin’s q

Since the relationship between patents and Tobin’s q is confusing, this paper utilizes panel threshold regression model to re-examine the relationship between patent counts/sales and Tobin’s q. This study finds out patent citations/sales has a single threshold effect on the relationship between patent counts/sales and Tobin’s q in the US pharmaceutical industry. The single threshold value of patent citations/sales is 328.81, and it divides the value of patent citations/sales into two regimes: the first regime (patent citations/sale ≦ 328.81) and the second regime (patent citations/sale > 328.81). The results indicate that patent counts/sales positively affect Tobin’s q in the two regimes. In addition, this study demonstrates that the extent of the positive effect of patent counts/sales on Tobin’s q is different. This study verifies that patent citations/sales moderates the relationship between patent counts/sales and Tobin’s q. Once patent citations/sales is below the threshold value, the extent of the positive relationship between patent counts/sales and Tobin’s q is the most. Therefore, this study finds out that the first regime is optimal.     

Indeterminate systems under cyclic alternating loading

Summary In the analysis of structures under static or dynamic loading on understanding of the behaviour of indeterminate systems is often most important. The authors, in their previous papers [1, 2], have attempted to develop a method for the study of simple structural components under cyclic loading consisting of controlled alternating displacements of equal amplitude producing plasticity. In this paper two and three hinge beam systems are analysed theoretically under similar ambient conditions and compared with experiments (after Royles [3]). Cyclic moment-curvature models, developed from pure bending tests, are applied to predict the behaviour of indeterminate systems. Static analyses of these systems are also carried out to compare the responses with cyclic behaviour.

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Résumé Dans l’analyse des structures soumises à des efforts statiques ou dynamiques, il est souvent très important de comprendre le comportement des systèmes indéterminés. Dans des articles antérieurs [1, 2], les auteurs avaient essayéde développer une méthode pour l’étude de simples éléments de structure soumis à des efforts cycliques consistant en déplacements alternés d’égale amplitude qui déterminent des déformations plastiques. On étudie ici théoriquement des systèmes de poutres à deux et trois articulations dans des conditions semblables d’ambiance et qu’on compare avec d’autres résultats d’expériences (Royles [3]). Pour prédire le comportement des systèmes indéterminés, on se sert de modèles présentant un moment de flexion cyclique, et mis au point d’après des essais en flexion pure. A des fins de comparaison avec le comportement sous sollicitation cyclique, on a aussi effectué l’étude statique de ces systèmes.

     

High field electrical behaviour in lithium-phospho-vanadate glass system

The high field electrical switching behaviour of lithium-phospho-vanadate glasses has been studied by determining the current-voltage characteristics. The investigated glasses exhibit temperature, thickness and composition dependent trends. At low current, the I–V characteristics obey Ohm’s law followed by a negative resistance region where the bulk behaviour dominates and at higher values of current the sample goes to a low resistance state. The studied glasses exhibit memory type switching. It is suggested that electrical switching is due to the formation of conducting channels that are due to electronic origin while thermal effects dominate once the channels are formed resulting in crystallization.     

DC magnetization studies of (Pr x Y1−x )Ba2Cu3O7−y

Magnetization was measured on Pr-doped YBa₂Cu₃O_7−y for fields up to 5·5T. The paramagnetic behaviour is correlated to the free ion values of Pr³⁺ and Pr⁴⁺. Hysteresis experiments were done for superconducting composition for fields up to 1100 Gauss. The intragrain critical current density is calculated using Bena’s formula.     

A regulator for continuous sedimentation in ideal clarifier–thickener units

The purpose of this paper is to present a regulator for control of the continuous-sedimentation process in a clarifier–thickener unit when this is modelled in one space dimension and when the settling properties of the solids obey Kynch’s assumption. The model is a scalar hyperbolic conservation law with space-discontinuous flux function and point source. The most desired type of solution contains a large discontinuity. A common objective is to control the movement of this discontinuity subject to the requirement that the effluent of the process have zero concentration of particles. In addition, there may be a requirement that the underflow concentration of the thickened suspension lie above a predefined value. Based on previous results on the nonlinear behaviour of the process, a nonlinear regulator is presented. It controls the location of the large discontinuity indirectly by controlling the total mass. The process is stabilized significantly and large input oscillations can be handled.     

Fatigue crack growth behaviour of gamma base titanium aluminides under different loading conditions

Static and cyclic fatigue crack growth behaviour of gamma base titanium aluminides with three different microstructures were investigated. Influence of cyclic test frequency on fatigue crack growth behaviour was also studied at room temperature under a controlled humidity condition. The crack growth behaviour both under static and cyclic loading was strongly influenced by the microstructure. The threshold stress intensity and crack growth behaviour under cyclic loading were much inferior than that under static loading indicating the ‘true-cyclic fatigue’ effect exhibited in gamma base titanium aluminides. No significant effect of test frequency on the crack growth behaviour was observed for the equiaxed and duplex microstructure materials.     

The gelation behaviors of the reactive blends of nylon1212 and functional elastomer

Studies on the gelation behaviors of the reactive blends of nylon1212 and functional elastomer were carried out. The results show that the curves of the storage modulus(G′)–frequency (ω) exhibit a gel plateau in the low ω region, and the transition from liquid-like to solid-like viscoelastic behaviors emerges with the concentration of SEBS-g-MA increasing. There exist the gelation behaviors in the blending process similar to those of crosslinking polymer. Based on Winter’s method, the gel point of blends is determined to be, φ_g = 17.45 wt%, and the corresponding value of tanδ is 1.44. The gel index n calculated is 0.61 and the gel strength S _g is 1.08 × 10⁴ Pa s^0.61. However, the non-reactive blends of nylon1212 and elastomer have no emergence of gelation behaviors. The morphology analysis shows that the gel point for the reactive blends is a threshold of cocontinuous morphology, and morphology analysis can also be a method to determine the gel point.     

The cubic autocatalator: The influence of degenerate singularities in a closed system

The appearance of apparently chaotic behaviour in this two-dimensional system is examined from an analytical point of view. The original two-parameter model exhibiting numerical solutions resembling chaos is unfolded to a three-parameter model. This enlarged model is shown to have a codimension-two degenerate Hopf bifurcation the unfolding of which contains phase portraits showing three concentric limit cycles. In some regions these limit cycles are so close to each other that numerical integration causes transitions across the unstable limit cycle, giving the appearance of chaotic behaviour. The region in parameter space of the ‘chaotic’ behaviour agrees well with the degenerate behaviour of the enlarged model.     

How do latecomers catch up with forerunners? Analysis of patents and patent citations in the field of flat panel display technologies

This paper sets out to explore the patterns of technological change and knowledge spillover in the field of flat panel display (FPD) technology, along with the catching-up behavior of latecomers, through the analysis of US patents and patent citations between 1976 and 2005. Our results show that: (i) the catching-up by FPD technology latecomers began at the transition stage (1987-1996) when the dominant design became established in areas with high ‘revealed technology advantage’ (RTA); (ii) there is no apparent localization of knowledge spillover amongst FPD technology latecomers; instead, higher citation frequencies of forerunners’ patents were found in latecomers’ FPD patents during the transition (1987–1996) and post-dominant design (1997–2005) stages and; and (iii) a few extraordinary peaks were found in the citation frequency of forerunners’ patents at long citation lags in latecomers’ FPD patents, particularly during the transition stage (1987–1996), indicative of the knowledge threshold which latecomers need to cross in order to catch up with forerunners.     

Tensile and creep behaviour of polyethylene terephthalate and polyethylene naphthalate fibres

Ropes made of twisted polyester (PET) yarns have been replacing traditional steel ropes and chains as mooring lines for offshore platforms in deep-sea environments. In order to optimise rope manufacture and the design of mooring systems, a thorough understanding of the material’s mechanical behaviour is necessary. Besides PET, other materials can also be considered such as PEN, as it also a polyester similar to PET but stiffer. This paper presents a study and comparison of PET and PEN fibres’ mechanical behaviour, based on experiments carried out on single filaments. Both fibres show similar non-linear tensile behaviour, with an evolution of modulus in four steps. The same microstructural model is proposed for both fibres, based on microfibrils aligned along the fibre axis and composed of an alternation of amorphous, mesamorphous and crystalline phases. The shape of the tensile loading curve is explained by the successive loading of these phases. Creep behaviour is also evaluated by considering the evolution of creep rate with applied load. This evolution is again similar for PET and PEN, both from a qualitative and quantitative point of view. The similarity in creep rate values for both fibres indicates that the microstructural mechanisms involved in creep may differ from those involved in short term tension loading.     

The hygrometric behaviour of some artificial stone materials used as elements of masonry walls

The hygrometric behaviour of four artificial stone materials utilised in the building industry for thermal insulation has been investigated utilising analytical methods typical of the applied petrography. The experimental data on the water absorption both in the liquid and in the vapour phase are in agreement with the data obtained from the natural stone materials and point out the existence in each material of a strong correlation between the absorption mechanisms and the porosimetric characteristics.

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Résumé On a étudié, à l’aide de méthodes analytiques utilisées en pétrographie appliquée, le comportement hygrométrique de quatre matériaux pierreux artificiels utilisés dans l’industrie du batiment pour leurs propriétés d’isolants thermiques. Les données expérimentales sur l’absorption d’eau aussi bien à l’état liquide qu’à l’état de vapeur, sont en accord avec les données obtenues sur les matériaux pierreux naturels, c’est-à-dire que dans chaque matériel il y a de fortes corrélations entre les mécanismes d’absorption d’eau et les caractéristiques porosimétriques.

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Editorial Note The CNR (Consiglio Nazionale delle Ricerche) is a RILEM Titular Member. The University of Florence is a RILEM Associate Member.     

Determination of Safe Operating Conditions for Non-gasketed Flange Joint under Combined Internal Pressure and Temperature

Performance of a flange joint is characterised mainly due to its ‘strength’ and ‘sealing capability’. A number of analytical and experimental studies have been conducted to study these characteristics only under internal pressure loading. However, with the advent of new technological trends for high temperature and pressure applications, an increased demand for analysis is recognised. The effect of steady state thermal loading is a well recognised problem and makes the problem more complex under combined application of internal pressure and temperature. The present design codes do not address the effects of temperature on the structural integrity and sealing ability. To investigate, joint strength and sealing capability under combined internal pressure and different steady state thermal loading, a 3D non-linear finite element analysis of non-gasketed flange joint is carried out and its behaviour is discussed. To determine the safe operating conditions or actual joint load capacity, the joint is further analyzed for different internal pressures and temperatures. In addition, effect of coefficient of thermal expansion of different flange joint component material is discussed and importance is highlighted.     

Research on the semantic-based co-word analysis

Through analysis of problems of keywords and indexes used in co-word analysis, we find that the key to solving these problems is to integrate experts’ knowledge into co-word analysis. Therefore, this paper proposes a new co-word analysis: semantic-based co-word analysis which can integrate experts’ knowledge into co-word analysis effectively. The performance of this method has been proved to be very good. It can solve problems on keywords and indexes used in co-word analysis effectively and can improve the veracity of co-word analysis. Using this method, the research filed of “human intelligence network” in China has been analyzed. According to the analysis result, we point out that there are four research focuses on it in China now. They are “methods and theories of human intelligence network”, “human intelligence network”, “competitive intelligence system (CIS for short)”, “the construction and visualization of human intelligence network”. The findings of this study not only advance the state of co-word analysis research but also shed light on future research directions.     

Unstable interstitial-vacancy pairs and paradoxes of high temperature properties of metals

There are some quite general and quite unexpected features of the high temperature behaviour of metals being reviewed by Ya. Kraftmakher. These are the discrepancy between the estimated number of point defects, determined by equilibrium and quenching experiments, the discrepancy between a number of point defects, estimated by high temperature dilatometric measurements and heat capacity ones, as well as the peculiarities in changing the self-diffusivity mechanisms at high temperatures. The mechanisms of these phenomena had been analysed, but some new qualitative and semi-quantitative approaches are here suggested for explaining the named paradoxes as the basis of a model of unstable pairs vacancy-atom at interstice, being the third type of equilibrium point defects in solids, in addition to Frenkel’s and Shottky’s defects. Received: 11 March 1999 / Reviewed and accepted: 7 April 1999     

Mechanical behaviour of corroded reinforced concrete beams—Part 2: Bond and notch effects

This paper deals with the effect of steel cross-section and bond strength reduction on the mechanical behaviour of corroded RC-beams. In the case of corroded reinforced concrete members, those effects are always coupled and a previous study (part one) has shown that it is not realistic to forecast the behaviour of corroded beams merely in terms of steel cross-section reduction. The object of the study is thus to understand the separated and coupled effects of the reduction in bond strength and steel cross-section. These investigations are carried out in order to be able to model the behaviour of corroded structural members and to predict how and when repairing is necessary. Different experimental simulations of corrosion were made. The results show the significant impact of coupling between reduction of bond strength and steel cross-section.

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Résumé Cet article traite de l’influence de la réduction de section d’acier et de l’adhérence acier béton en partie tendue sur le comportement mécanique des poutres corrodées. L’étude précédente (partie 1) semble montrer qu’il n’est pas réaliste de vouloir prédire le comportement mécanique des éléments de structures corrodées en ne tenant compte que de la réduction de section des aciers tendus. Par conséquent, l’objectif de ce travail est de mieux comprendre et quantifier les effets couplés et découplés de ces deux paramètres. Pour cela, plusieurs simulations expérimentales des effets de la corrosion ont été réalisées sur poutres ou sur échantillons d’armature non corrodés. Les expérimentations mécaniques sont réalisées en service et à rupture. Les résultats obtenus confirment largement qu’une prédiction réaliste du comportement mécanique résiduel en service des poutres corrodées, ne sera obtenue qu’en prenant en compte de l’effet couplé de la réduction de section d’acier et de l’adhérence acier béton en partie tendue.

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Editorial Note Prof. Ginette Arliguie is a RILEM Senior Member. She works at LMDC (Laboratoire Matériaux et Durabilité des Constructions), a RILEM Titular Member.     

World-wide university rankings: A Scandinavian approach

Although universities’ world rankings are popular, their design and methods still request considerable elaborations. The paper demonstrates some shortcomings in the Academic World Ranking of Universities (ARWU, Shanghai Jiao Tong University) ranking methods. One deficiency is that universities’ scale differences are neglected due to omitting the whole input side. By resampling and reanalyzing the ARWU data, the paper proposes an input-output analysis for measuring universities’ scientific productivity with special emphasis on those universities which meet the productivity threshold (i.e. share of output exceeds share of input) in a certain group of universities. The productivity analysis on Scandinavian universities evaluates multidisciplinary and specialized universities on their own terms; consequently the ranking based on scientific productivity deviates significantly from the ARWU.     

Dynamics and ‘normal stress’ evaluation of dilute suspensions of periodically forced prolate spheroids in a quiescent Newtonian fluid at low Reynolds numbers

The problem of determining the force acting on a particle in a fluid where the motion of the fluid and the particle is given has been considered in some detail in the literature. In this work, we propose an example of a new class of problems where, the fluid is quiescent and the effect of an external periodic force on the motion of the particle is determined at low non-zero Reynolds numbers. We present an analysis of the dynamics of dilute suspensions of periodically forced prolate spheroids in a quiescent Newtonian fluid at low Reynolds numbers including the effects of both convective and unsteady inertia. The inclusion of both forms of inertia leads to a nonlinear integro — differential equation which is solved numerically for the velocity and displacement of the individual particle. We show that a ‘normal stress’ like parameter can be evaluated using standard techniques of Batchelor. Hence this system allows for an experimentally accessible measurable macroscopic parameter, analogous to the ‘normal stress’, which can be related to the dynamics of individual particles. We note that this ‘normal stress’ arises from the internal fluctuations induced by the periodic force. In addition, a preliminary analysis leading to a possible application of separating particles by shape is presented. We feel that our results show possibilities of being technologically important since the ‘normal stress’ depends strongly on the controllable parameters and our results may lead to insights in the development of active dampeners and smart fluids. Since we see complex behaviour even in this simple system, it is expected that the macroscopic behaviour of such suspensions may be much more complex in more complex flows.     

An algorithm for detecting drift in the value of the comparison standard when analyzing the data of key comparisons of national standards

An algorithm for revealing the piecewise-linear drift of the value of the comparison standard when making international comparisons is proposed. The probabilities of errors of the 1st and 2nd kinds are estimated and recommendations are made on choosing the parameters of the algorithm. A comparative analysis of different algorithms for identifying a point of discontinuity of the piecewise-linear drift model is carried out. __________ Translated from Izmeritel’naya Tekhnika, No. 2, pp. 68–72, February, 2008.     

Elastic and anelastic behaviour of icosahedral quasicrystals

A theory is developed, based on theoretical-group analysis, to describe the linear, reversible, time-dependent response of an icosahedral quasicrystal, containing point defects, to a stress field and known as anelastic relaxation. We obtain also anelastic relaxation relationships for the practical Young’s, shear and Poisson’s moduli.