A study on resonance characteristics of hydraulic structures and buildings conducted using small-size models

Introduction. The study focuses on resonance characteristics of a hydraulic engineering structure, such as a groin, land retention works on an artificial island, and a school building. Any structure, exposed to dynamic effects of natural or man-induced origin, can be validly simulated as a mechanical resonator. Models are made of materials that have electro-elastic properties allowing to measure responses to induced oscillations, or changes in an alternating electric field, and reevaluate the physical characteristics later. Materials and methods. Small-size physical models of structures are made of electro-elastic materials, such as organic glass and ABS plastic, used for 3D printing. A laboratory test bench, composed of an oscillator and a personal computer, used as an oscillograph, was applied to conduct the testing. Mathematical modeling was performed using SolidWorks software packages. Oscillation modes and structural responses, featuring different response amplitudes, were identified. Models of structures were studied in different contexts, including restraint and free bearing. Results. It has been found that frequencies of the first mode of oscillations in a restrained model correspond to the fourth mode of a model in case of free bearing. Mutual correlation of eigenfrequencies of oscillations in small-size models, made of ABS plastic and organic glass, is demonstrated. Conclusions. The applicability of ABS plastic as the material of small-size physical models of buildings and structures has been proven for the purpose of identifying resonance frequencies of the prototypes. The co-authors have developed an integrated physical and mathematical modeling method that entails the use of SolidWorks software packages. This method allows to identify resonance frequencies, which are most dangerous for structures. Different structure support patterns allow to apply the geometric scale to obtain resonance frequencies when translating small-size model results to natural values and, hence, identify the vulnerability of structures to dynamic effects.

DEVELOPMENT OF MACHINE FOR HOT FORMING OF AVIATION GLAZING FROM ORGANIC GLASS USING ADDITIVE TECHNOLOGIES

This article discusses the issues of improving hot forming technology of aviation glazing parts from organic glass using modern methods of additive technologies, relevance of development and implementation of this technology in production.

Vitrification of octonary perylene mixtures with ultralow fragility

Strong glass formers with a low fragility are highly sought-after because of the technological importance of vitrification. In the case of organic molecules and polymers, the lowest fragility values have been reported for single-component materials. Here, we establish that mixing of organic molecules can result in a marked reduction in fragility. Individual bay-substituted perylene derivatives display a high fragility of more than 70. Instead, slowly cooled perylene mixtures with more than three components undergo a liquid-liquid transition and turn into a strong glass former. Octonary perylene mixtures display a fragility of 13 ± 2, which not only is a record low value for organic molecules but also lies below values reported for the strongest known inorganic glass formers. Our work opens an avenue for the design of ultrastrong organic glass formers, which can be anticipated to find use in pharmaceutical science and organic electronics.

Estimation of chemical safety of environmental protection technologies for atmosphere pollution reduction (a case study of processess of laser treatment of polymer materials)

Introduction. One way to protect atmospheric air from industrial pollution is the use of environmental protection technologies aimed at emissions purification. As a result of the man-induced impact, the industrial emissions can change the composition of air medium, while the resulting products of physical and chemical transformations with other, sometimes more toxic properties, can influence on the quality and chemical safety of atmospheric air in comparison with the initial substances entering it as part of industrial emissions. Materials and methods. Studies of the impact of various technologies of treatment the industrial atmospheric emissions of organic glass and polymer materials processing plants with laser systems were carried out using a chromato-mass spectrometric system Focus GC with DSQ II (USA). Results. We have established the change in the qualitative-quantitative composition of emissions from organic glass laser treatment processes using various cleaning devices. Estimation of electrostatic purification technology efficiency based on plasma-catalytic oxidation with atomic oxygen revealed an increase in the transformation products - aldehydes. The cleaning devices seems ineffective and chemically unsafe concerning one of the primary pollutants included in the emissions of organic glass and polymer materials processing plants with laser systems - methyl methacrylate. Conclusion. The use of new environmental protection technologies for emissions purification can cause a change in their qualitative-quantitative composition, which requires chemical-analytical control. It is advisable to use chromatography-mass spectrometry to identify and quantify up to 100 substances simultaneously in the air with an unknown composition of pollutants to assess the efficiency and chemical safety of new technologies for emissions purification adequately. It will certainly reduce and minimize health risks and allow considering the possibility of man-induced formation of transformation by-products.

On the Mutual Relationships between Molecular Probe Mobility and Free Volume and Polymer Dynamics in Organic Glass Formers: cis-1,4-poly(isoprene)

We report on the reorientation dynamics of small spin probe 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) in cis-1,4-poly(isoprene) (cis-1,4-PIP10k) from electron spin resonance (ESR) and the free volume of cis-1,4-PIP10k from positron annihilation lifetime spectroscopy (PALS) in relation to the high-frequency relaxations of cis-1,4-PIP10k using light scattering (LS) as well as to the slow and fast processes from broadband dielectric spectroscopy (BDS) and neutron scattering (NS). The hyperfine coupling constant, 2Azz′(T), and the correlation times, τc(T), of cis-1,4-PIP10k/TEMPO system as a function of temperature exhibit several regions of the distinct spin probe TEMPO dynamics over a wide temperature range from 100 K up to 350 K. The characteristic ESR temperatures of changes in the spin probe dynamics in cis-1,4-PIP10k/TEMPO system are closely related to the characteristic PALS ones reflecting changes in the free volume expansion from PALS measurement. Finally, the time scales of the slow and fast dynamics of TEMPO in cis-1,4-PIP10k are compared with all of the six known slow and fast relaxation modes from BDS, LS and NS techniques with the aim to discuss the controlling factors of the spin probe reorientation mobility in polymer, oligomer and small molecular organic glass-formers.