Dynamic Performance Analysis of Interfacial Cracks Near an Eccentric Elliptical Hole in Piezoelectric Bi-Materials Under Incident SH-Waves

2020 ◽  
Author(s):  
Ni An ◽  
Tian-shu Song ◽  
Ming Zhao ◽  
Yu Liu ◽  
Gangling Hou
Keyword(s):  
Piezoelectric Materials ◽  
Dynamic Stress Intensity Factor ◽  
Modern Science ◽  
Elliptical Hole ◽  
Mapping Method ◽  
Wave Number ◽  
Mechanical Coupling ◽  
Interfacial Cracks ◽  
The Impact ◽  
Dynamic Performance Analysis

Abstract Piezoelectric materials have been widely used in modern science and technology due to their electro-mechanical coupling response. Sometimes, because of the stiff and brittle nature of some piezoelectric materials, the piezoelectric devices with defects may face fracture or failure during their service procedures. Therefore, it has become important to investigate the failure behaviors caused by defects, such as cracks and holes. Based on the study of the dynamic anti-plane characteristics for radial crack emanating from a circular cavity in piezoelectric bi-materials, this paper aims to analyzes the dynamic incident anti-plane shearing (SH-wave) in piezoelectric bi-materials, which contains two interfacial cracks, near an eccentric elliptical hole. Green’s function method, the conformal mapping method, the interface conjunction techniques and the crack-deviation techniques are utilized to obtain a series of first kind Fredholm’s equations, based on which the dynamic stress intensity factor (DSIF) at the outer and the inner cracks’ tips are theoretically expressed. Numerical examples were graphically presented to illustrate the effects of the piezoelectric parameter, the effective piezoelectric elastic modulus, the dimensionless incident wave number and geometric parameters on the DSIF at both of the tips. Previous studies are not comprehensive, especially when the center of the hole deviates from the interface. Therefore, the impact of eccentric distance on DSIF is considered in this paper. The solution of this problem provides a more accurate and efficient method for the investigation of dynamic fracture properties of piezoelectric materials and has an important theoretical significance in engineering design.

Dynamic performance for piezoelectric bi-materials with an interfacial crack near an eccentric elliptical hole under anti-plane shearing

2021 ◽  
pp. 108128652110149
Author(s):  
Ni An ◽  
Tianshu Song ◽  
Gangling Hou
Keyword(s):  
Stress Concentration ◽  
Dynamic Performance ◽  
Crack Problem ◽  
Interfacial Crack ◽  
Elliptical Hole ◽  
Mapping Method ◽  
Dynamic Stress Intensity Factors ◽  
Interfacial Cracks ◽  
Conformal Mapping Method ◽  
Plane Shearing

The purpose of this paper is to evaluate the stress concentration at the tip of a permeable interfacial crack near an eccentric elliptical hole in piezoelectric bi-materials under anti-plane shearing. Fracture analysis is performed by Green’s function method and the conformal mapping method, which are used to solve the boundary conditions problem. The mechanical model of the interfacial crack is constructed by interface-conjunction and crack-deviation techniques so that the crack problem is simplified as solving a series of the first kind of Fredholm’s integral equations, from which the dynamic stress intensity factors (DSIFs) at the inner and the outer crack-tips can be derived. The validity of the present method is verified by comparing with a crack emerging from the edge of a circular hole as a reference. Numerical cases reveal parametric dependence of DSIFs on the geometry of eccentric elliptical holes and interfacial cracks, the characteristics of the incident wave, the equivalent piezoelectric elastic modulus and piezoelectric parameters. The results illustrate that the eccentric distance has a great effect on the stress concentration at the crack tip, which may be harmful to the normal service of piezoelectric devices and materials. In addition, the method proposed in this paper can also deal with non-eccentric problems and has wider applicability.

New directional wave observations from CFOSAT : impact on ocean/wave coupling in the Southern Ocean

2021 ◽  
Author(s):  
Lotfi Aouf ◽  
Daniele Hauser ◽  
Stephane Law-Chune ◽  
Bertrand chapron ◽  
Alice Dalphinet ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Surface Wind ◽  
Bias Reduction ◽  
Ocean Wave ◽  
Wave Number ◽  
Geophysical Research ◽  
Wave Coupling ◽  
Ocean Region ◽  
Directional Wave ◽  
The Impact

<p>The Southern ocean is a complex ocean region with uncertainties related to surface wind forcing and fluxes exchanges at the air/sea interface. The improvement of wind wave generation in this ocean region is crucial for climate studies. With CFOSAT satellite mission, the SWIM instrument provides directional wave spectra for wavelengths from 70 to 500 m, which shed light on the role of correcting the wave direction and peak wave number of dominant wave trains in the wind-waves growth phase. This consequently induced a better energy transfer between waves and a significant bias reduction of wave height in the Southern Ocean (Aouf et al. 2020). The objective of this work is to extend the analysis of the impact of the assimilation of wave number components from SWIM wave partitions on the ocean/wave coupling. To this end, coupled simulations of the wave model MFWAM and the ocean model NEMO are performed during the southern winter period of 2019 (May-July). We have examined the MFWAM/NEMO coupling with and without the assimilation of the SWIM mean wave number components. Several coupling processes related to Stokes drift, momentum flux stress and wave breaking inducing turbulence in the ocean mixing layer have been analyzed. We also compared the coupled runs with a control run without wave forcing in order to evaluate the impact of the assimilation. The results of coupled simulations have been validated with satellite Sea Surface Temperature and available surface currents data over the southern ocean. We also investigated the impact of the assimilation during severe storms with unlimited fetch conditions.</p><p>Further discussions and conclusions will be commented in the final paper.</p><p>Aouf L., New directional wave satellite observations : Towards improved wave forecasting and climate description in Southern Ocean, Geophysical Research Letters, DOI: 10.1029/2020GL091187 (in production).</p><p> </p><div> <div> <div></div> <div>What do you want to do ?</div> New mail</div> </div><div><img></div>

scholarly journals FORMATION OF RESEARCH MOTIVATION AND SKILLS AT STUDENTS IN MULTILEVEL EDUCATIONAL SYSTEM

2020 ◽  
pp. 219-225
Author(s):  
Наталья Александровна Храмова ◽  
Надежда Георгиевна Пфаненштиль
Keyword(s):  
Educational Research ◽  
Professional Training ◽  
Scientific Information ◽  
Modern Science ◽  
Educational Process ◽  
Research Activity ◽  
Student Activities ◽  
Research Activities ◽  
New Research ◽  
The Impact

В данной статье проанализировано основное различие понятий учебно-исследовательской и научно-исследовательской деятельности. Основной проблемой является развитие мотивации к учебной научно-исследовательской деятельности учащихся. Выявлено, что на мотивационную готовность студентов к научно-исследовательской деятельности могут оказывать влияние многие факторы, рассмотрено их воздействие. В статье приведены различные студенческие мероприятия, которые могут способствовать повышению мотивации учащихся к исследовательской деятельности. Выявлены, проанализированы научно-исследовательские умения и их компоненты (операционный, содержательный, мотивационный). Реализация в профессиональной подготовке традиционных форм обучения (лекции, лабораторные, практические, семинарские занятия, коллоквиумы, курсовые и дипломные работы, консультации, индивидуальные занятия) помогает овладению учащимися научной информацией, но не всегда способствует формированию необходимых умений и навыков. Очевидно, что внедрение новых теоретических обобщений в учебный процесс (чтение преподавателями проблемных лекций, введение новых теоретических разделов по наиболее актуальным проблемам современной науки, расширение перечня учебной литературы и интернет-источников, освоение новых методик исследования, подготовка мультимедийных презентаций) повысит интерес студентов к исследовательской деятельности. Образовательный процесс будет проходить более успешно, если в вузе сформирована эффективная образовательная и научно-исследовательская среда, направленная на развитие личности студента. This article analyzes the main difference between the concepts of educational research activity and research activity. The main problem is the development of motivation for educational research activities at students. The authors revealed that many factors can influence students’ motivation readiness for research activities; considered the impact of those factors. The article presents various student activities that can help to increase students’ motivation for research activities; identifies and analyzes the research skills and their components (operational, content, motivation). The implementation of traditional forms of education in professional training (lectures, laboratory, practical, seminars, colloquiums, term papers and theses, consultations, individual classes) helps students master scientific information, but does not always contribute to the formation of the necessary skills. It is obvious that the introduction of new theoretical generalizations in the educational process (delivering of problem lectures, introduction of new theoretical units on the most relevant problems of modern science, expanding the list of educational literature and Internet sources, development of new research methods, multimedia presentations) will increase the interest of students in research activities. The educational process will be more successful if the University has an effective educational and research environment aimed at the development of the student’s personality.

scholarly journals The ‘Vero Cell’ COVID-19 vaccine rollout in Nepal: What we know about the Chinese vaccine development and access?

2021 ◽  
Vol 8 (1) ◽  
pp. 1-8
Author(s):  
Jay Narayan Shah
Keyword(s):  
Clinical Trial ◽  
United Arab Emirates ◽  
Science And Technology ◽  
Modern Science ◽  
Phase Iii ◽  
Phase 3 ◽  
Pharmaceutical Group ◽  
Fda Approval ◽  
The Usa ◽  
The Impact

The world has changed dramatically from the impact of the COVID-19. It has impacted the normality of daily life, highlighting the failure of rich and poor nations alike, which is evident from the high number of human lives lost in rich and powerful countries like the USA with total deaths of 32,735,704 and Europe with 43,708,958 until April 24, 2021, as per Worldometer. The COVID-19 pandemic has shown that all of us ‘have and have-not’, no one can escape from the effects of the lockdowns, disruption of normal life including education, businesses, etc. reminding all of us that equitable access to vaccines is the best possible choice not to further exacerbate the challenges because ‘no country is safe until every country is safe’. It is a remarkable scientific achievement that within a year of the identification of the virus, we have COVID-19 vaccines, albeit available mostly in rich countries. The benefit of research is possible only with solidarity, by sharing the available resources, vaccine included, for the control of the ongoing COVID-19 pandemic. Modern science and technology, including the development and marketing of COVID-19 vaccines, have been focused in the USA and Europe. China joined this club of elites of science following the Chinese FDA approval of Sinopharm (the subsidiary of state-owned China National Pharmaceutical Group- CNPG), first COVID-19 vaccine (inactivated Sars-Cov-2) based on the results of the phase-3 clinical trial in UAE and Bahrain showing up to 86% efficacy of the vaccine in preventing COVID-19. Detail of trials of Sinopharm inactivated COVID-19 vaccines (Vero Cells) available on two early trials in China (Phase I/II ChiCTR2000031809, enrollment 1,456) and later 4 trials outside China (phase III, NCT04510207 Bahrain, Egypt, Jordan, United Arab Emirates- enrollment of 45,000; ChiCTR2000034780 United Arab Emirates, enrollment of 15,000; NCT04612972 Peru, enrollment of 6,000) show the progress of research and approval in China and UAE. Modern science and technology, including the development and marketing of COVID-19 vaccines, have been focused in the USA and Europe. China joined this club of elites of science following the Chinese FDA approval of Sinopharm (the subsidiary of state-owned China National Pharmaceutical Group- CNPG) first COVID-19 vaccine (inactivated Sars-Cov-2) based on the results of the phase-3 clinical trial in UAE and Bahrain showing up to 86% efficacy of the vaccine in preventing COVID-19.3

Thermal–Mechanical Coupling Evaluation of the Panel Performance of a Prefabricated Cabin-Type Substation Based on Machine Learning

Fire ◽  
2021 ◽  
Vol 4 (4) ◽  
pp. 93
Author(s):  
Xiangsheng Lei ◽  
Jinwu Ouyang ◽  
Yanfeng Wang ◽  
Xinghua Wang ◽  
Xiaofeng Zhang ◽  
...  
Keyword(s):  
Neural Network ◽  
Machine Learning ◽  
Numerical Simulation ◽  
Fire Resistance ◽  
Bp Neural Network ◽  
Stress Test ◽  
Normal Operation ◽  
Model Parameters ◽  
Mechanical Coupling ◽  
The Impact

The panel performance of a prefabricated cabin-type substation under the impact of fires plays a vital role in the normal operation of the substation. However, current evaluations of the panel performance of substations under fire still focus on fire resistance tests, which seldom consider the relationship between fire behavior and the mechanical load of the panel under the impact of fires. Aiming at the complex and uncertain relationship between the thermal and mechanical performance of the substation panel under impact of fires, this paper proposes a machine learning method based on a BP neural network. First, the fire resistance test and the stress test of the panel is carried out, then a machine learning model is established based on the BP neural network. According to the collected data, the model parameters are obtained through a series of training and verification processes. Meanwhile, the correlation between the panel performance and fire resistance was obtained. Finally, related parameters are input into the thermal–mechanical coupling evaluation model for the substation panel performance to evaluate the fire resistance performance of the substation panel. To verify the correctness of the established model, numerical simulation of the fire test and stress test of the panel is conducted, and numerical simulation samples are predicted by the trained model. The results show that the prediction curve of neural network is closer to the real results compared with the numerical simulation, and the established model can accurately evaluate the thermal–mechanical coupling performance of the substation panel under fire.

METEOROLOGICAL VOCABULARY IN UKRAINIAN AND CHINESE LANGUAGES: SYSTEMATIC TRANSLATION

2020 ◽  
Vol 2020 (31) ◽  
pp. 36-50
Author(s):  
Natalia Gavrilyuk
Keyword(s):  
Human Life ◽  
Modern Science ◽  
Weather Conditions ◽  
Well Being ◽  
Natural Phenomena ◽  
Important Place ◽  
Close Link ◽  
Ancient People ◽  
The World ◽  
The Impact

Within the anthropocentric paradigm of modern linguistics there is a steady interest in the human factor in language, which, among other things, is realized through the close attention of researchers to the theory of linguistic pictures of the world, which fully reflects the uniqueness of peoples Human life and activity are inseparable from nature. Nature is one, but manifests itself in various forms. In the process of learning about nature, man tries to realize both its unity and diversity. A special place in the perception of the world by man is occupied by climatic and weather phenomena that affect human behavior in the world, various aspects of his life, including economic, as well as well-being. In the IV century. BC became aware of the impact of fluctuations in weather conditions on human health. For example, Hippocrates established a close link between human disease and the weather conditions in which he lives. Over the centuries, people have gathered a variety of knowledge about nature: from misunderstanding of natural phenomena, fear of them, inherent in ancient people, to today’s scientific knowledge of nature, from the first folk signs of weather to the formation of modern science — meteorology. Nature as a source of everything necessary for man has an impact on both the material and spiritual culture of society. Therefore, knowledge of meteorological phenomena occupies an important place in the awareness of reality. The article considers the peculiarities of meteorological vocabulary in Chinese and Ukrainian languages, as well as the peculiarities of meteorological vocabulary translation in two languages.

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