On Electromechanical Coupling in Elastomers

Permittivity of electroactive elastomers alters during deformation. The influence of the permittivity alterations on the electrostriction of elastomers is studied in the present work. Particularly, acrylic elastomer VHB 4910 is considered. A polarization-electric field constitutive theory is introduced accounting for the influence of mechanical deformations. The theory is used to analyze a free electrostriction of a thin elastomer plate. The elastic stress in the plate is described by various constitutive models including neo-Hookean, Yeoh, Arruda-Boyce, and Ogden. Results show that the permittivity alterations during mechanical deformation practically do not affect the process of electrostriction

Spherical void expansion in rubber-like materials: The stabilizing effects of viscosity and inertia

Dynamic cavitation is known to be a typical failure mechanism in rubber-like solids. While the mechanical behaviour of these materials is generally rate-dependent, the number of theoretical and numerical works addressing the problem of cavitation using nonlinear viscoelastic constitutive models is scarce. It has been only in recent years when some authors have suggested that cavitation in rubber-like materials is a dynamic fracture process strongly affected by the rate-dependent behaviour of the material because of the large strains and strain rates that develop near the cavity. In the present work we further investigate previous idea and perform finite element simulations to model the dynamic expansion of a spherical cavity embedded into a rubber-like ball and subjected to internal pressure. To describe the mechanical behaviour of the rubber-like material we have used an experimentally calibrated constitutive model which includes rate-dependent effects and material failure. The numerical results demonstrate that inertia and viscosity play a fundamental role in the cavitation process since they stabilize the material behaviour and thus delay failure

Modeling deformation and failure of elastomers at high strain rates

In this paper we develop a new constitutive model to describe the viscoelastic response of elastomers subjected to high strain rates. The key and original feature of the model is that it takes into account the failure of the material using an energy limiter. We calibrate the constitutive model for various strain rates using the experimental data reported by Hoo Fatt and Ouyang (2008) and show the capacity of the proposed formulation to describe the rate-dependent behavior of styrene butadiene rubber. In addition, we implement the model into ABAQUS/Explicit using a simple scheme for the temporal integration of the constitutive equations. Finally, we show sample numerical simulations to illustrate the joint performance of the constitutive model and the integration algorithm.DAI, GV and JARM are indebted to the Spanish Ministry of Economy and Competitiveness (Projects EUIN2015-62556 and DPI2014-57989-P) for the financial support received which allowed conducting part of this work. KYV acknowledges support from the Israel Science Foundation, grant No. ISF-198/15.Publicad

Free Expression in America Post-2020 A Landmark Survey of Americans Views on Speech Rights

Free expression and the freedom of speech are cornerstones of American democracy. Yet the interpretation of the First Amendment continues to be a flashpoint in the 21st century as the nation debates how to apply these rights to our society. For the 2021 "Free Expression in America Post-2020" report, Knight Foundation commissioned Ipsos to conduct a survey with a nationally representative sample of more than 4,000 American adults, including an additional sample of 1,000 undergraduate college students. The Knight Foundation-Ipsos study provides a comprehensive look at American attitudes toward freedom of speech in a post-2020 environment, building on Knight Foundation's long-standing work studying free speech views among students since 2004. The findings described in this report cover many but not all of the rich insights possible from this complex dataset. We invite the public and researchers to explore this publicly available resource in further detail. This study finds that all Americans hold to the ideal of free speech, but putting free expression into practice reveals significant differences in experiences and attitude. It examines how Americans view free expression issues, events and the application of our First Amendment rights in an increasingly digital, diverse, and politically driven society.

Wildlife population changes across eastern europe after the collapse of socialism

When political regimes fall, economic conditions change and wildlife protection can be undermined. Eastern European countries experienced turmoil following the collapse of socialism in the early 1990s, raising the question of how wildlife was affected. We show that the aftermath of the collapse changed the population growth rates of various wildlife taxa. We analyzed populations of moose (Alces alces), wild boar (Sus scrofa), red deer (Cervus elaphus), roe deer (Capreolus capreolus), brown bear (Ursus arctos), Eurasian lynx (Lynx lynx), and gray wolf (Canis lupus) in nine countries. Population growth rates changed in 32 out of 49 time series. In the countries that reformed slowly, many species exhibited rapid population declines, and population growth rates changed in 83% of the time series. In contrast, in countries with fast post- socialism reforms, many populations increased rapidly, and growth rates changed in only 48% of time series. Our results suggest that the direction and frequency of the changes were associated with socioeconomic conditions, and that wildlife populations can be greatly affected by socioeconomic upheavals

The study of bats by ultrasound detector in the zone of influence of wind farms in Ukrainian Azov region

UK: За останнє десятиріччя вітрові електростанції (ВЕС) набули значної популярності у Європі. Саме з ними пов'язують розвиток майбутньої енергетики та скорочення темпів зростання парникового ефекту. Одна кВт/година вітрової енергії скорочує виділення діоксиду вуглецю приблизно на 600 т порівняно з електростанціями, що спалюють кам'яне вугілля або нафту. Так, наприклад, у Німеччині використання поновлюваних джерел енергії дало змогу уникнути викиду в атмосферу 35 млн. тон різних газів (Deutschland, 2002). Великий інтерес до виробництва електроенергії за допомогою вітру є і в Україні, де вже створено кілька парків ВЕС

LIQUID NUTRIENT MEDIUM FOR SUBMERGED CULTIVATION OF TULAREMIA MICROBE

The paper describes an effective liquid nutrient medium, utilization of which in the process of submerged cultivation of the vaccine tularemia microbe strain allows for the production of high concentrations of viable biomass with low rates of dissociation, which is essential in manufacturing of live vaccines. Dry enzymatic hydrolysate of fibrin, by-product of anti-rabies immunoglobulin production is used as a nutrient-rich base of the new nutrient medium