Degree Of Imperfections Research Articles

Investigations of initial imperfections of steel scaffold structures

AbstractAnalysis and design of structures sensitive to second order effects require to take into account initial imperfections. Scaffold structures, due to their low rigidity, are very sensitive to second order effects. The accuracy of the design of such structures is based in part on the estimation of initial imperfections affecting the structure. In the 60s, the C.E.C.M., the European Convention of Steel Construction, has launched a test campaign to determine the degree of initial imperfections of each type of cross‐section. Five buckling curves have been established. The European design code for steel structures, Eurocode 3 Part 1‐1, classifies cold‐formed hollow tubular sections among sections with many imperfections, i.e. curve ‘c'. A test campaign has launched to analyse the experimental buckling curve behaviour of cold‐formed hollow sections of scaffold structures. Nineteen buckling tests on simply supported members and nine buckling tests on scaffolding ladders, from various European suppliers, have been carried out. Statistical studies of the experimental results highlight that the estimation of the initial imperfection currently defined for the cold‐formed tubular sections is far too penalizing for the sections used in the field of scaffolds.

Market Imperfections within the European Wheat Value Chain: The Case of France and the United Kingdom

The focus of this paper is on the analysis of market imperfections in the French and U.K. wheat value chains. We used mark-up and mark-down models and stochastic frontier analysis to estimate the degree of market imperfections in two completely different wheat-to-bread chains for two stages/sectors—milling and baking. Our results reveal some degree of market imperfections within the input and output markets for both the milling and baking sectors in France and the United Kingdom. However, the abuse of bargaining power is especially pronounced in the input market for the second stage of wheat processing, particularly in the French baking sector. However, we did not observe the expected positive association between the degree of market imperfections and company size except for a group of middle, large, and very large companies within the millers’ input market. Small companies indicate considerably high values of “Lerner”/Lerner indices, suggesting a benefit from other sources of competitive advantage (such as quality, niche markets, etc.).

Experimental investigations of buckling behaviour of steel scaffolds

The analysis and design of structures sensitive to second order effects require the consideration of initial imperfections. Scaffold structures, due to their low stiffness, are very sensitive to second order effects. The accuracy of the design of these structures relies in part on the estimation of initial imperfections affecting the structure. In the 1960s, the C.E.C.M., the European Convention of Steel Construction, carried out a series of experimental tests to determine the degree of initial imperfections of each type of cross-section. Five buckling curves were established. The European design code for steel structures, Eurocode 3 Part 1-1, classifies hot-rolled hollow tubular sections as profiles with few imperfections, i.e. buckling curve ‘a’, and cold-formed sections as sections with many imperfections, i.e. buckling curve ‘c’. A test campaign was conducted to analyse the experimental buckling behaviour of hot-rolled and cold-formed hollow sections of scaffold structures. Twenty-nine buckling tests on simply supported members and nine buckling tests on scaffolding ladders, from various European suppliers, were carried out. Statistical studies of the experimental results point out that the estimate of the initial imperfection currently defined for the hot-rolled and cold-formed tubular sections is far too penalizing for sections used in scaffolding.

Mathematical analysis of surface wave transference through imperfect interface in FGPM bedded structure

In the present article, a theoretical investigation has been carried out to analyze the propagation of shear horizontal surface waves (SH-waves) in a structure consisting of a functionally graded piezoelectric material (FGPM) layer lying over an FGPM half-space. The material properties of FGPM layer are assumed to have exponential function distribution along the thickness direction whereas those of FGPM half-space are presumed to have quadratic variation. The interface between the FGPM layer and the FGPM half-space has been considered to be imperfect. At the surface, two cases are considered, electrically open case and electrically short case. Moreover two types of imperfections at the interface are taken into account (one as mechanically compliant and dielectrically weakly conducting and other as mechanically compliant and dielectrically highly conducting). Variable separable method is used for the wave solution. In particular, the solutions for mechanical displacement and electric potential function for FGPM half-space has been obtained in the form of modified Bessel function. The dispersion relation for each case is obtained in determinant form using suitable boundary conditions. Numerical example is given and graphs are plotted. The numerical results show that the surface wave velocity is affected by the layer width, gradient coefficient of the two FGPM media, and the degree of mechanical and dielectrical imperfections at the interface between the covering layer and the substrate. This study finds its application in optimization of SAW devices.

Numerical Analysis of Vibration Patterns in Hydropower Units

AbstractEvery manufactured hydropower rotor shows some degree of unbalance and other imperfections that cause vibrations. In this contribution, a non‐linear dynamic model is used to calculate the lateral vibrations of vertical rotors in hydropower units due to generator unbalance and coupling misalignment. The vibrations are analyzed and distinguishing features are identified. Using the identified features, it is possible to diagnose the vibration cause from vibrational data for the described model. This can be done even when some model parameters like bearing properties are not known with high accuracy.

Labor market imperfections, markups and productivity in multinationals and exporters

This paper examines the links between a firm’s internationalization status and the type and degree of market imperfections in product and labor markets. We develop a framework for modelling heterogeneity across firms in terms of (i) product market power (price-cost markups), (ii) labor market imperfections (workers’ bargaining power during worker-firm negotiations or a firm’s degree of wage-setting power) and (iii) revenue productivity. We apply this framework to analyze whether the pricing behavior of firms in product and labor markets differs across firms that engage in different forms of internationalization using an unbalanced panel of 7,458 manufacturing firms over the period 1994-2012 in Japan. Engagement in international activities is found to matter for determining not only the type of imperfections in product and labor markets but also the degree of imperfections. Clear differences in behavior between firms that serve the foreign market either through exporting or through FDI are observed. Exporters are more likely to be characterized by imperfect competition in the product market whereas the opposite holds for multinationals. Exporters are more likely to share rents based on the bargaining power of workers whereas a firm’s wage-setting power seems to generate wage dispersion across firms with foreign subsidiaries.

Performance of carbon nanotubes in mortar using different surfactants

The performance of carbon nanotubes (CNTs) in cement-based composites relies to a great extent on its degree of dispersion. In this work, the performance of two commonly used surfactants; sodium dodecyl sulfate (SDS) and Triton X-100, is being compared. The effect of surfactant-to-CNT ratio on dispersion efficiency is studied using ultraviolet-visible (UV-Vis) spectrometry, to determine the optimum surfactant dosage. For the optimum ultrasonication energy, Raman spectroscopy is used to assess the degree of imperfections on CNTs. CNTs-reinforced mortar specimens prepared using Triton X-100 and SDS are tested for compressive and flexural strength. Triton X-100 is shown to exhibit better dispersion efficiency than SDS, leading to greater improvement in flexural and compressive strength. An ultrasonication time of 60 min (19.4 kJ/mL) is shown to be sufficient to achieve proper dispersion, however notable degradation of CNTs was noted beyond 30 min (9.7 kJ/mL) of dispersion leading to a strength reduction.

Labor Market Imperfections, Markups and Productivity in Multinationals and Exporters

This paper examines the links between the internationalization mode of firms and market imperfections in product and labor markets. We develop a framework for modelling heterogeneity across firms in terms of (i) product market power (price-cost markups), (ii) labor market imperfections (workers' bargaining power during worker-firm negotiations or firm's degree of wage-setting power) and (iii) revenue productivity. We apply this framework to analyze whether the pricing behavior of firms in product and labor markets differs across firms that engage in different forms of internationalization. Engagement in international activities is found to matter for determining not only the type of imperfections in product and labor markets but also the degree of imperfections. Clear differences in behavior between firms that serve the foreign market either through exporting or through FDI are observed. Being an exporter introduces allocative inefficiencies in product as well as labor markets as we find export status to be positively correlated with both product market power (markups) and market power consolidated on the labor supply side (workers' bargaining power). But exporting firms where search frictions are inducing wages to vary with revenue are less able to exploit wage-setting power. Firms with foreign subsidiaries, on the other hand, seem to reduce price distortions in product and labor markets. In addition, we observe heterogeneous returns to being an exporter/MNE within an industry and also discern cross-industry differences.

Labor Market Imperfections, Markups and Productivity in Multinationals and Exporters

This paper examines the links between the internationalization mode of firms and market imperfections in product and labor markets. We develop a framework for modelling heterogeneity across firms in terms of (i) product market power (price-cost markups), (ii) labor market imperfections (workers' bargaining power during worker-firm negotiations or firm's degree of wage-setting power) and (iii) revenue productivity. We apply this framework to analyze whether the pricing behavior of firms in product and labor markets differs across firms that engage in different forms of internationalization. Engagement in international activities is found to matter for determining not only the type of imperfections in product and labor markets but also the degree of imperfections. Clear differences in behavior between firms that serve the foreign market either through exporting or through FDI are observed. Being an exporter introduces allocative inefficiencies in product as well as labor markets as we find export status to be positively correlated with both product market power (markups) and market power consolidated on the labor supply side (workers' bargaining power). But exporting firms where search frictions are inducing wages to vary with revenue are less able to exploit wage-setting power. Firms with foreign subsidiaries, on the other hand, seem to reduce price distortions in product and labor markets. In addition, we observe heterogeneous returns to being an exporter/MNE within an industry and also discern cross-industry differences.

Modelling of an Actuator in the Vacuum Control System of an Autonomous Milking Machine

Abstract Design intents for an actuator of the suction pressure control system in an autonomous milking machine were presented. For determination of its dynamic properties step characteristic was taken. The considered object was described with transmittance and thermodynamic models. Models were identified and their parameters were adjusted. Computer simulation was carried out in MATLAB®-Simulink. Analysis of research results proved that the thermodynamic model allows more detailed reflection of dynamic characteristic of the real object. Its degree of imperfections is 0.99%. For the transmittance model a degree of imperfection with the value of 2.02% was obtained.

On impatience, temptation and Ramsey’s conjecture

This article explores the implications of the introduction of self-control costs and temptation motives in intertemporal preferences in an elementary competitive equilibrium. We let heterogeneous agents differ in both their discount parameters and their temptation motives, and the degree of financial-market imperfections vary, and establish their implications for the long-run value of the capital stock and the underlying long-run distribution of consumption and wealth. The results differ from those obtained in a standard Ramsey benchmark model, in that long-run distributions are commonly non-degenerate.

Effects of nanoporosity and surface imperfections on solid bitumen reflectance (BRo) measurements in unconventional reservoirs

Bitumen reflectance (BRo) is an alternative maturity indicator to vitrinite reflectance (VRo) in Lower Paleozoic and marine rocks where few higher plant macerals can be found. In unconventional petroleum rocks, locally exuded and/or migrated oil are retained in the tight rocks and thermally and diagenetically consolidated into solid bitumen and pyrobitumen. Finding suitable bitumen macerals for BRo measurements pose a challenge in indicating the proper thermal maturity. This study reports the effects of surface imperfections caused by nanoporosity, surface granularities, and impurities on measuring BRo in core samples from the Jurassic Nordegg Shale (shale oil) and the Triassic Montney siltstone (tight gas) in the Western Canada Sedimentary Basin. The degree that bitumen's surface imperfections influence any given reflectance measurement was controlled by changing the probe size area. The larger the measuring probe, the higher the degree of surface imperfections is included in BRo readings. The effect is quantified in this paper, showing up to 27% diminishment of mean BRo values when the probe size increased from 0.31 to 5.85μm2. The mode in which bitumen accumulates within the rock has a strong influence on the degree of surface imperfections. Bitumen which is disseminated within clay matrix introduces a high degree of nanoporosity and mineral interference and hence will result in lowest BRo. In contrast, inclusions of high reflecting micrinite or diagenetic minerals such as pyrite result in higher BRo. These effects can vary at the microscopic scale leading to multiple populations of reflectance readings and difficult interpretations of thermal maturity.

Preparation of magnetite core-titania shell and hollow titania nanoparticles via layer-by-layer (LbL) assembly method

Time-resolved small-angle X-ray scattering (SAXS) analysis was performed on a series of poly(ethyleneco-1,4-cyclohexyldimethylene terephthalate)s (PECT copolymers) containing 1.6, 5.3, and 9.8 mol% 1,4-cyclohexyldimethylene (CHDM) units during isothermal crystallization and subsequent melting processes. The measured SAXS data were quantitatively analyzed to yield detailed information (scattering invariant quantity, Q; long period, Lp; lamellar crystal layer thickness, dc; and amorphous layer thickness, da) about the crystal structure evolution and melting devolution behaviors. The Q value was found to be a very sensitive powerful probe for monitoring the crystallization and crystal melting processes. The structural evolution of the copolymers was dominated by the primary crystallization transition. The secondary crystallization effects contributed little to the structural evolution. The few secondary crystals present most likely formed fringed micelle structures that were very small and included a high degree of imperfections. The poor secondary crystal formation was attributed to the presence of bulky, kinked CHDM units, which introduced a high degree of steric hindrance. The high steric hindrance of the CHDM units resulted in their exclusion from the lamellar crystal layers and secondary crystals, and in their insertion into amorphous regions and layers. Overall, the CHDM comonomer units strongly perturbed the crystallization process and the morphological structure of the PECT copolymer. The effects of CHDM as a chemical modifier of poly(ethylene terephthalate)-based polymers may potentially be optimized in an effort to enhance the properties and processability of the polymer. Open image in new window

Time-resolved synchrotron X-ray scattering studies on crystallization behaviors of poly(ethylene terephthalate) copolymers containing 1,4-cyclohexylenedimethylene units

Time-resolved small-angle X-ray scattering (SAXS) analysis was performed on a series of poly(ethyleneco-1,4-cyclohexyldimethylene terephthalate)s (PECT copolymers) containing 1.6, 5.3, and 9.8 mol% 1,4-cyclohexyldimethylene (CHDM) units during isothermal crystallization and subsequent melting processes. The measured SAXS data were quantitatively analyzed to yield detailed information (scattering invariant quantity, Q; long period, L p ; lamellar crystal layer thickness, d c ; and amorphous layer thickness, d a ) about the crystal structure evolution and melting devolution behaviors. The Q value was found to be a very sensitive powerful probe for monitoring the crystallization and crystal melting processes. The structural evolution of the copolymers was dominated by the primary crystallization transition. The secondary crystallization effects contributed little to the structural evolution. The few secondary crystals present most likely formed fringed micelle structures that were very small and included a high degree of imperfections. The poor secondary crystal formation was attributed to the presence of bulky, kinked CHDM units, which introduced a high degree of steric hindrance. The high steric hindrance of the CHDM units resulted in their exclusion from the lamellar crystal layers and secondary crystals, and in their insertion into amorphous regions and layers. Overall, the CHDM comonomer units strongly perturbed the crystallization process and the morphological structure of the PECT copolymer. The effects of CHDM as a chemical modifier of poly(ethylene terephthalate)-based polymers may potentially be optimized in an effort to enhance the properties and processability of the polymer.

The propagation of compaction bands in porous rocks based on breakage mechanics

We analyze the propagation of compaction bands in high porosity sandstones using a constitutive model based on breakage mechanics theory. This analysis follows the work by Das et al. [] on the initiation of compaction bands employing the same theory. In both studies, the theory exploits the links between the stresses and strains, and the micromechanics of grain crushing and pore collapse, giving the derived constitutive models advantages over previous models. In the current post localization analysis, the bifurcation instability of the continuum model is suppressed by the use of a rate‐dependent regularization. This allows us to perform a series of finite element analyses of drained triaxial tests on porous sandstone specimens. The obtained numerical results compare well with experimental counterparts, in terms of both the initiation and propagation of compaction bands, besides the macroscopic stress‐strain responses. On this basis, a parametric study is carried out to explore the effects of loading rate, degree of structural imperfections, and confining pressure on the propagation of compaction bands.

Inhomogeneity in Hydrogels Synthesized by Thiol–Ene Polymerization

Hydrogels synthesized via thiol–ene polymerization were characterized with respect to their macroscopic properties via elasticity measurements and to their microscopic properties, in particular inhomogeneity, by dynamic light scattering. For comparison, identical studies were made on polyacrylamide (PAAm) hydrogels prepared by free-radical chain-growth cross-linking copolymerization. Mechanical measurements prove that for both types of gels the degree of network imperfections is widely varied by varying concentration, while the macroscopic properties observed at particular concentrations are very similar. However, the fraction of static scattering which is a measure of gel inhomogeneity depends significantly on the type of network studied when the measurement is performed in the state of preparation. The majority of the thiol–ene gels appear homogeneous, contrary to the PAAm gels. The situation is completely different in the equilibrium swollen state, where all gels exhibit extremely high and almost identical fractions of static scattering intensity, irrespective of the type of reaction or the concentration employed in their synthesis. These observations imply that (i) there is no clear correlation between network imperfections and homogeneity and (ii) the type of cross-linking reaction controls the concentration inhomogeneity in the state of preparation but not (iii) the inhomogeneity of network density. The latter is seen when the gels are swollen.

Effect of crystallisation conditions and feedstock morphology on the aerosolization performance of micronised salbutamol sulphate

Salbutamol sulphate (SS) used in dry powder inhalers requires drug particles in the respirable size range of 1–5 μm to achieve a suitable therapeutic effect. The aim of this study was therefore to determine strategies for controlling drug substance characteristics pre and post-crystallisation to facilitate the production of micronised SS with desirable particle attributes for optimal delivery as an inhaled aerosol. SS batches were crystallised using an antisolvent method to produce a range of crystal morphologies. Air jet milling was then used to reduce the size of crystallised SS particles. Starting materials and micronised batches of SS were characterised in the solid state using a range of techniques with subsequent assessment of aerosol properties. Assessment of the aerodynamic characteristics of micronised SS delivered by DPI (without any carrier) indicated that fine particle fraction and emitted dose as a percentage of the total recovered dose were dependent on the quality attributes of the micronised SS, which were directly linked to the degree of imperfections and the morphology of the crystalline feedstock used in micronisation. Aerosolization performance of micronised SS can be optimised by manipulation of feedstock characteristics through crystal engineering and through definition of optimal processing conditions for micronisation.

Modelling of the sulfuric acid leaching of mechanically activated titanite

A titanite CaTiSiO 5 concentrate was mechanically activated in a laboratory centrifugal-planetary mill for up to 10 min at dry and wet conditions. XRD analysis showed the weakening and broadening of diffraction peaks are mainly due to dry mechanical activation (MA) than due to wet MA. Leaching experiments were carried out using 30% H 2SO 4 at 20, 40, and 60 °C. Preliminary MA of titanite concentrate lead to significant increase in the leaching rate. Dry MA of titanite for 10 min resulted in ~ 90% Ti dissolved at 60 °C for 2.5 h. Leaching efficiency of unactivated titanite at similar conditions was about 1% Ti dissolved. Wet MA was found to be less effective than dry MA, despite the former attaining significantly larger surface area. This is due to greater degree of amorphization induced by dry MA in comparison to wet MA. In the suggested kinetic model an attempt was made to take into consideration the influence of BET surface area, amorphization of mineral and decrease in average energy stored by mineral due to MA in the course of leaching on the rate of dissolution. Small size crystallites and regions with large lattice strain which are typical of outer particle layers dissolve at a higher reaction rate. As the leaching time increases, the average degree of structure imperfections of the remaining powder decreases. Consequently, the average energy stored by mineral due to MA decreases and activation energy increases leading to decreasing the dissolution rate. The activation energy derived from the model indicates that the reaction of titanite with sulfuric acid is chemically controlled.

The happiness puzzle: analytical aspects of the Easterlin paradox

We apply an optimizing model with relative comparisons (habit formation) in consumption and labour supply to the economics of happiness, specifically the 'Easterlin paradox'. Studying a generalization of the paradox, which we label the 'happiness puzzle', we analyse ways in which income growth affects happiness. In our model, those factors include agents' risk aversion; whether the economy experiences balanced or unbalanced growth; how non-pecuniary factors affect well-being; and the degree of market imperfections. We also demonstrate that the dynamic specification of habit formation rather than its mere existence matters for whether the happiness puzzle arises on a balanced growth path. Only when habit is modelled in ratio form, does this possibility open up. Our model thus bridges the gap between theory, empirics and social policy. It provides a basis for studying a number of specific policy issues, such as corrective taxes. Copyright 2012 Oxford University Press 2011 All rights reserved, Oxford University Press.

Risk Management and Risk Transfer:Distributive Justice in Finance

Questions of distributive justice in risk management arise with varying intensity in different market settings. This article argues that perfect financial markets provide a context in which questions of distributive justice are seldom salient. In such markets, all traders have access to the same information about the item being traded, and traders are generally anonymous. For the most part, the author argues, these conditions justify ignoring questions of distributive justice. In imperfect markets, managing risk becomes relevant to distributive justice. Differential information between trading parties can quickly lead to a situation in which one party exploits another, particularly when the advantageous information is gained via a privileged position or illegitimate means. As the degree of market imperfections increases, so does the importance of considerations of distributive justice. In nonfinancial markets generally, and in labor markets particularly, a firm’s efforts to manage risk often affect others in ways that may be unjust. Finally, firms’ risk management activities can create risks for parties far beyond those who actually manage the risk or participate in the risk management process. These affected parties can even include the public at large. <b>TOPICS:</b>Financial crises and financial market history, risk management