Robust optimization approach for mixed numerical/experimental identification of elastic properties of orthotropic composite plates

This paper describes a method for determination of elastic parameters (elastic moduli and Poisson’s ratio) of orthotropic composite plate-type structural elements using the results of natural frequency measurements. The identification of parameter values is provided by minimization of weighted squared difference (discrepancy) between physically measured frequencies and natural frequencies calculated by Finite Element Method. The metamodels for the frequency dependence on the elastic parameters and other geometrical and physical parameters of test specimens, including parameters with uncertainty (“noisy constants”) are built using experimental designs optimized according to the Mean Squared Error space filling criterion and third-order polynomial approximations. The minimum of weighted squared difference is found using the multistart random search method. The expressions for standard deviations of identified parameters depending on deviations of “noisy constants” are derived using linearized metamodels. The expressions for identification errors allow the statement of the identification task as a robust minimization problem by simultaneous minimization of the discrepancy function and standard deviations of the identified values by varying the values of unknown elastic parameters and weighting coefficients for different frequencies. The partial scaling of natural frequencies is used for the reduction of the uncertainty impact on the identification error. This allows to reduce the identification error of elastic moduli about two times and Poisson’s ratio about 20 times in comparison with the results obtained by using dimensioned frequencies

Institutional Arrangements: A Gate Towards Sustainable Land Use

Various common problems can be observed of the ongoing land management processes in Central and Eastern European (CEE) countries. The problems appear mainly because of conflicting legislation, performance of procedures, political unwillingness, lack of capacity of the local municipalities and other public administration, insufficiency of information and people participation, lack of skills of the professionals and in public administration. Source of all the mentioned problems is insufficient understanding of the institutional setting of the land management processes. The aim of this contribution is to introduce the reader to the theory of the institutional economics and discuss its importance for systematisation of both the regulatory framework, i.e. institutions – ‘rules of the game’ and the procedures in the fields of territorial planning and real property formation. This theory provides a vocabulary to describe the balance between the regulatory structures (public sector) and the market forces (private sector) that will allow controlled growth and will be perceived as of general economic and social well being to the populace. Thus, the paper is intended to activate and urge politicians, governmental authorities, non-governmental organizations, academic staff and managers of private firms. This contribution also can be seen as a source for further development of concepts for analysis of the observed problems. Hence combining the theory with appropriate methodology may suggest, how to deal with the stated various problems. Monographic descriptive method and logical analysis have been used in this contribution

Shape Optimization of Mechanical Components for Measurement Systems

Manufacturing industrie

Polymorph-Selective Role of Hydrogen Bonding and π-π Stacking in p-Aminobenzoic Acid Solutions

Understanding molecular self-association in solution is vital for uncovering polymorph-selective crystal nucleation pathways. In this paper, we combine solution NMR spectroscopy and molecular dynamics simulations to shed light on the structural and dynamical features of p-aminobenzoic acid (pABA) in solution, and on their role in pABA crystals nucleation. pABA is known to yield different crystal forms (α, and β) depending on solvent choice and supersaturation conditions. NMR reveals that dominant interactions stabilizing pABA oligomers are markedly solvent-dependent: in organic solvents, hydrogen bonds dominate, while water promotes π-πstacking. Despite this clear preference, both types of interactions contribute to the variety of self-associated species in all solvents considered. MD simulations support this observation and show that pABA oligomers are short-lived and display a fluxional character, therefore indicating that the growth unit involved in pABA crystallization is likely to be a single molecule. Nevertheless, we note that the interactions dominating in pABA oligomers are indicative of the polymorph obtained from precipitation. In water, at low pABA concentrations - conditions that are known to yield crystals of the β form - carboxylic-carboxylic hydrogen bonds are exclusively asymmetric. At higher pABA concentration conditions in which the crystallization is known to yield the α form - a small but statistically significant fraction of symmetric carboxylic-carboxylic hydrogen-bonded dimers is present. We interpret the presence of these interactions in solvated pABA oligomers as indicative of the fact that a simultaneous and complete desolvation of two carboxylic groups, necessary to form the symmetric hydrogen-bonded dimer typical of the α crystal form, is accessible, therefore directing the nucleation pathway toward the nucleation of α-pABA

Analysis of the sensitivity of a vibration-based procedure for structural identification

We analyze the accuracy of estimation of structural component material properties (elastic modulus, Poisson’s ratio, density, etc.) using the technique for measuring the eigen frequencies of oscillations. The accuracy of frequency estimation using the Fourier method and its influence on the final result are evaluated. Relationships between the errors in the frequency estimation and those in the identified parameters are derived using the meta-model method. Application of the method is illustrated by the example of a shell element with a stiffening rib.Проаналізовано точність визначення властивостей матеріалів елементів кон­струкцій(модульпружності, коефіцієнт Пуассона ,щільність і ін.)методом вимірювання частот власних коливань. Оцінено точність визначення часто­ти методом Фур’є і вплив її на кінцевий результат.За допомогою методу метамоделей виведено залежності між помилками вимірювання частот та помилками ідентифікованих параметрів.Метод про ілюстровано на прикладі елемента обшивки з ребром жорсткості.Проанализирована точность определения свойств материалов элементов конструкций (модуль упругости, коэффициент Пуассона, плотность и др.) методом измерения частот собственных колебаний. Оценены точность определения частоты методом Фурье и влияние ее на конечный результат. С помощью метода метамоделей выведены зависимости между ошибками измерения частот и ошибками идентифицируемых параметров. Метод проиллюстрирован на примере элемента обшивки с ребром жесткости

Analysis of the sensitivity of a vibration-based procedure for structural identification

We analyze the accuracy of estimation of structural component material properties (elastic modulus, Poisson’s ratio, density, etc.) using the technique for measuring the eigen frequencies of oscillations. The accuracy of frequency estimation using the Fourier method and its influence on the final result are evaluated. Relationships between the errors in the frequency estimation and those in the identified parameters are derived using the meta-model method. Application of the method is illustrated by the example of a shell element with a stiffening rib.Проаналізовано точність визначення властивостей матеріалів елементів кон­струкцій(модульпружності, коефіцієнт Пуассона ,щільність і ін.)методом вимірювання частот власних коливань. Оцінено точність визначення часто­ти методом Фур’є і вплив її на кінцевий результат.За допомогою методу метамоделей виведено залежності між помилками вимірювання частот та помилками ідентифікованих параметрів.Метод про ілюстровано на прикладі елемента обшивки з ребром жорсткості.Проанализирована точность определения свойств материалов элементов конструкций (модуль упругости, коэффициент Пуассона, плотность и др.) методом измерения частот собственных колебаний. Оценены точность определения частоты методом Фурье и влияние ее на конечный результат. С помощью метода метамоделей выведены зависимости между ошибками измерения частот и ошибками идентифицируемых параметров. Метод проиллюстрирован на примере элемента обшивки с ребром жесткости

Production of Phosphorescent Coatings on 6082 Aluminum Using Sr0.95Eu0.02Dy0.03Al2O4-δ Powder and Plasma Electrolytic Oxidation

In this study, a new approach for producing phosphorescent aluminum coatings was studied. Using the plasma electrolytic oxidation (PEO) process, a porous oxide coating was produced on the Al6082 aluminum alloy substrate. Afterwards, activated strontium aluminate (SrAl2O4: Eu2+, Dy3+) powder was filled into the cavities and pores of the PEO coating, which resulted in a surface that exhibits long-lasting luminescence. The structural and optical properties were studied using XRD, SEM, and photoluminescence measurements. It was found that the treatment time affects the morphology of the coating, which influences the amount of strontium aluminate powder that can be incorporated into the coating and the resulting afterglow intensity.This research project was supported financially by ERDF Project No: Nr.1.1.1.1/16/A/182; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Thermostimulated luminescence of plasma electrolytic oxidation coatings on 6082 aluminium surface

Financial support provided by Scientific Research Project for Students and Young Researchers Nr. SJZ/2016/12 realized at the Institute of Solid State Physics, University of Latvia is greatly acknowledged. Authors are grateful to R. Ignatans for measurements and analysis of XRD spectra and ElGoo Tech ltd. for providing PEO equipment.For decades, plasma electrolytic oxidation (PEO) coatings are actively studied and applied to protect the surface of various valve metals from chemical or mechanical damage. However, over the last couple of years intense research is being done to explore additional possibilities of the PEO coatings apart from their classical application. One of the possible additional uses is thermostimulated luminescence dosimetry that is already widely applied for environmental and health monitoring. This research proposes a method to produce a novel functional coating on aluminium surface exhibiting intense thermostimulated luminescence signal that could be used for dosimetry of ionizing radiation. The result was achieved using plasma electrolytic oxidation with modified electrolyte to introduce carbon ions into the oxide thus inducing defects in the crystalline structure of the coating. Al6082 aluminium alloy was used as a substrate, KOH and ethanol mixture as an electrolyte. A bipolar pulsed regime was used for 15 min. The obtained coating combines the desired luminescence properties with a good mechanical stability due to the relatively hard cubic phase of the coating. Scalability of the technology and low production cost makes the coatings prospective for various practical applications.ISSP UL Scientific Research Project for Students and Young Researchers Nr. SJZ/2016/12; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Recombination luminescence of X-ray induced paramagnetic defects in BaY2F8

This research is funded by the Latvian Council of Science , project “Novel transparent nanocomposite oxyfluoride materials for optical applications”, project No. LZP-2018/1–0335 . The crystal growth research was funded by the CNPq (Brazil), project NO 421581/2016–6 .Recombination luminescence (RL) and RL-detected electron paramagnetic resonance (RL-EPR) in BaY2F8 single crystal has been investigated after irradiation with X-rays at low temperature. The recombination process, which lasts for several hours at 4 K, results in several broad bands in the RL spectrum. RL-EPR spectra show pronounced angular dependences on crystal orientation relative to external magnetic field. Based on the determined spin-Hamiltonian parameter values the recombination centres have been proposed to be F-type electron and self-trapped hole (VK) centresLatvian Council of Science LZP-2018/1–0335; CNPq 421581/2016–6; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Land take and value capture : towards more efficient land use

The paper aims to explore the possibilities to enhance the efficiency of land use, considering the evolution of land take (LT), and proposes the use of public value capture (PVC) instruments in selected differently experienced countries. This answers two fundamental questions. How is the concept of LT positioned in relation to the environmental policy of Europe? Which PVC instruments could stimulate more efficient land use? The aim of this article is to identify which tools can guide the transformations of the urban environment by promoting more efficient land use. These tools have been identified in the mechanisms for capturing value as they can pursue the goal of a more attractive net LT. For these reasons, the article initially analyses the spread of the problem of land consumption, at a European level, showing how this phenomenon is very diversified not only between individual states, but also within each nation. In addition, the knowledge system to define the main initiatives and actions aimed at orienting urban development in the direction of reducing land consumption is highlighted. Subsequently, the theoretical framework concerning the issues relating to the capture of public value in urban planning operations is illustrated. The case studies representing the various European contexts are then introduced, and for each case the dynamics of urban development were analysed. It has been done in relation to the evolution of the regulatory apparatus of territorial governance and its transformations. On the basis of this analysis, indicators have been defined. Their goal is to allow comparing the results that emerged from the case study analysis, which would otherwise have been inconsistent. In this way, it is possible to demonstrate how land use is more efficient in countries where PVC tools are used systemically and how these tools make it easier to guide urban transformations in line with the principles of sustainable development.This article is based upon work from COST Action 17125, supported by COST (European Cooperation in Science and Technology).peer-reviewe