Consideration Of Imperfections Research Articles

Regulatory framework for the assessment of the impacts of plant protection products on biodiversity: review of strengths and limits.

The placing of plant protection products (PPPs) on the market in the European Union is governed by numerous regulations. These regulations are among the most stringent in the world, however they have been the subject of criticisms especially because of the decline in biodiversity. The objectives of this work were to review (1) the functioning and actors involved in the PPP framework processes, (2) the construction of the environmental risk assessment focused on biodiversity, and (3) the suggested ways to respond to the identified limits. Both literature from social sciences and ecotoxicology were examined. Despite the protective nature of the European regulation on PPPs, the very imperfect consideration of biodiversity in the evaluation process was underlined. The main limits are the multiplicity of applicable rules, the routinization of the evaluation procedures, the lack of consideration of social data, and the lack of independence of the evaluation. Strengths of the regulation are the decision to integrate a systemic approach in the evaluation of PPPs, the development of modeling tools, and the phytopharmacovigilance systems. The avenues for improvement concern the realism of the risk assessment (species used, cocktail effects…), a greater transparency and independence in the conduct of evaluations, and the opening of the evaluation and decision-making processes to actors such as beekeepers or NGOs. Truly interdisciplinary reflections crossing the functioning of the living world, its alteration by PPPs, and how these elements question the users of PPPs would allow to specify social actions, public policies, and their regulation to better protect biodiversity.

Experimental and numerical investigations on slender panels with holes under symmetrical localised loads

Perforated steel girders under a single or combined in plane loading have been largely studied in the literature. However, such investigations were trusted on the numerical modelling and FEM analysis and due to the lack of experimental results in most cases, the accuracy of the numerical model and the consideration of imperfections in the FEM analyses are open to reflexion. In this paper, a series of experimental tests are performed to study the post-critical behaviour of perforated steel girders. Ten full scales steel girders were tested under uniaxial compressive force. Amongst them, four were used as control specimens whereas a circular hole was located in the center of the other six. The parameters such as the geometry of the web plate, the position of the hole and the plate slenderness are found as those most influencing the post-critical behaviour. Finally, the experimental results were used to validate the intensive numerical analyses. The results obtained showed the strong influence of combined geometrical imperfections and residual stresses on the mid-plane Von Mises stresses.

Consideration of imperfections and support effects in the fatigue assessment of welded cruciform joints

Abstract The strain-life approach appears to be a powerful tool to design components against fatigue failure. Given its general theoretical background, it may be applied to a wide range of cases. In the contribution at hand, its application to welded components, and especially the incorporation of size effects in the concept has been investigated. For this purpose, eight welded cruciform joints were tested for fatigue at two different load amplitudes, accompanied by supplementary investigations such as hardness measurements and tensile tests. The observed fatigue lives were compared to numerically estimated ones. Special attention was paid to the consideration of imperfections in the calculations. The weld geometries were modeled once using an idealized shape and once with a realistic representation obtained by 3D-laser scanning. Additionally, different methods to approximate cyclic material parameters were investigated. The results show an improvement in prediction accuracy if the real weld geometry is used. However, by doing so, the incorporation of size effects via a highly stressed area is open for discussion. Due to the high local stress and its steep gradients, as a result of the scanned weld surface, the calculated areas are very small, which raises the question whether this is still within the limits of its application. Regarding prediction accuracy, the fatigue lives of either one or the other load amplitudes were properly estimated. This issue may be addressed by modifying the slope of the strain-life curve for welded components, which can be achieved by a parameter fitting procedure through a large set of experiments.

Further study of linear PMSM driven ropeless lifts with consideration of imperfections by simulation

To provide a satisfactory lift service to super high-rise buildings (while maintaining a small footprint for the lift hoistways), ropeless multi-car per hoistway system may be the trend. In our previous paper, a simplified machine model and two primitive controllers were adopted and various features of such a ropeless lift car driven by a linear permanent magnet synchronous motor were illustrated by simulation. In this paper, imperfections including pole saliency, various types of friction such as Coulomb, viscous and Stribeck friction, cogging force and end-effect, etc. were considered. The controllers, control interval and simulation interval were improved in both quantity and quality to arrive at a controllably stable operation. For safety during a genuine power failure, the free-falling terminal speed was estimated both by analytical calculation and computer simulation with consideration of such imperfections. It was confirmed that a desirable operation could be achieved by having smaller and practical winding resistance and inductances, larger and practical permanent magnet magnetic flux, and an optimal pole pitch. This paper could be considered an enhanced version of the pervious paper in that the illustration is more realistic when imperfections are considered. It is hoped that experimenters would further verify the findings in this paper so that such technology could become popularly employed in the future lift industry. Practical application: Multi-dimensional multi-car in a hoistway configuration involving linear permanent magnet synchronous machines would become popular in the near future. This paper introduces a more comprehensive mathematical framework by taking into account of the imperfections in the design and evaluation of controllers as well as the drive performance for a multi-car lift system. The results may give lift designers and researchers a hint on how to design the machines and the controllers with the consideration of imperfections in terms of winding design with variation in resistance, inductance, magnetic field strength, pole pitch, saliency and different types of friction. The paper is aimed at providing lift designers and researchers with a more realistic picture to welcome the new age of multi-car multi-dimensional lift technology.

Influence of Transformational Leadership Style on Global Competitive Advantage through Innovation and Knowledge

Today's business organizations necessitate a new leader who can easily confront a new business approach that mainly based on knowledge and innovation to simplify the organization's path toward global marketing trend. Still; organizations sometimes flop to reach sustainable global competitive advantage due to their imperfect consideration of the relationships between these strategic variables.
 
 In fact, and up to our knowledge, few researches has consider and examine the direct and indirect associations linking these variables. Our study tries to fill this gap by investigating, theoretically and empirically, how the leader's discernment of diverse intermediary strategic variables related to innovation and knowledge (knowledge slake, absorptive capacity, tacitness) and innovation impact the relation between transformational leadership and organizational global competitive advantage. Based on recently published researchers, we developed a theoretical model that demonstrate the actual connection linking these variables.
 
 Most of the data has been collected through secondary resources including journals, books and related research papers. While a questionnaire was used to collect data samples from 50 respondents from Telecommunication Regulatory Authority leaders and employees in UAE, model testing also conscious the findings and deliver some conclusion from business leaders to confirm the relations tested among this research.

04.16: Rethinking imperfections in tanks and silos

ABSTRACTA careful consideration of imperfections is critical to the design of shell structures to ensure that they are both adequately safe and economically built. Following the development of the Eurocode for shell structures EN 1993‐1‐6, the situation has considerably improved: the extensive literature on the imperfection sensitivity of shells has been introduced into practical designs; fabrication tolerance classes have been defined, which allow the designer to adjust his design to the professional efforts of the fabricator; and numerical and experimental results have been matched by defining an axisymmetrical weld depression as a substitute imperfection in the recent amendment. These advances seem to have established a very good position, and it might be thought that little more needs to be done. However, a closer look at some of the above items reveals the need to reconsider the management of imperfections, especially from the designers point of view. In this paper the authors attempt to make a first step to resolve the role of imperfections from different points of view. In addition, some unpublished results from researches at KIT are presented.

Imperfection of Domain Knowledge and Its Formalization in Context of Design of Robust Software Systems

In this paper, it is emphasized that taking into consideration of imperfection of knowledge, of the team of the designers/developers, about the problem domains and environments is essential in order to develop robust software metrics and systems. In this respect, first various possible types of imperfections in knowledge are discussed and then various available formal/mathematical models for representing and handling these imperfections are discussed. The discussion of knowledge classification & representation is from computational perspective and that also within the context of software development enterprise, and not necessarily from organizational management, from library & information science, or from psychological perspectives.

Low Cycle Fatigue of Seam Welds – Numerical Simulation under Consideration of Material Inhomogeneities

Austenitic stainless steel of type X6CrNiNb18-10 is a commonly used material for pipelines of power plants. The fatigue behavior of these components is often operationally determined by thermo-mechanical stresses. Welded joints are subjected to various geometries and micro structural inhomogeneities, which lead to complex stresses in the component. This is the reason for a reduced fatigue life, in contrast to material's life itself, is observed.A parametric finite element model is developed, to investigate the influence parameters. In order to take into account the non- uniform hardness distribution in the region of the weld seam, hardness measurements are the base for the consideration of a material mismatch in plastic behavior. The material parameters for the used Chaboche material model must be modified individually, depending on the mismatch. In addition, the consideration of imperfections of the welding geometry is an important factor, too. Using a local approach by using measured geometry-parameters of the weld seam, acceptable accordance between experimentally and numerically calculated fatigue lives can be gained. The observed phenomena in experimental investigations that fatigue failure occurs either at the base metal or at the weld toe (depending on the loading conditions) can be reproduced by numerical simulations. This knowledge is used to develop an approach for lifetime estimation.

Revisiting the failure mode of a RC hyperbolic cooling tower, considering changes of material and geometric properties

The failure mode of a previously analyzed reinforced concrete (RC) hyperbolic cooling tower is re-investigated by means of the Finite Element Method (FEM), however, with another computer program. Furthermore, the original design of this cooling tower is changed. The changes include use of ultra-high-strength-fiber concrete (UHSF-concrete), reduction of the thickness of the shell, and consideration of imperfections of the original geometry of the structure. The main conclusion drawn from the numerical results is that the cooling tower would still fail by loss of strength, characterized by the existence of an ultimate load and of yielding of the reinforcement.

Experimental and Numerical Analysis of Composite Folded Sandwich Core Structures Under Compression

The characterisation of the mechanical behaviour of folded core structures for advanced sandwich composites under flatwise compression load using a virtual testing approach is presented. In this context dynamic compression test simulations with the explicit solvers PAM-CRASH and LS-DYNA are compared to experimental data of two different folded core structures made of aramid paper and carbon fibre-reinforced plastic (CFRP). The focus of the investigations is the constitutive modelling of the cell wall material, the consideration of imperfections and the representation of cell wall buckling, folding or crushing phenomena. The consistency of the numerical results shows that this can be a promising and efficient approach for the determination of the effective mechanical properties and a cell geometry optimisation of folded core structures.

Finite element limit load analysis of thin-walled structures by ANSYS (implicit), LS-DYNA (explicit) and in combination

After discussing general properties of implicit FE analysis using ANSYS and explicit analysis using LS-DYNA it is shown when and how quasi-static limit load analyses can be performed by a transient analysis using explicit time integration. Then we focus on the remaining benefits of implicit analysis and how a proper combination of ANSYS and LS-DYNA can be used to prepare the transient analysis by common preprocessing and static analysis steps. Aspects of discretization, solution control, consideration of imperfections and methods of checking the results are outlined.