Influence of Defect Number, Distribution Continuity and Orientation on Tensile Strengths of the CNT-Based Networks: A Molecular Dynamics Study

Networks based on carbon nanotube (CNT) have been widely utilized to fabricate flexible electronic devices, but defects inevitably exist in these structures. In this study, we investigate the influence of the CNT-unit defects on the mechanical properties of a honeycomb CNT-based network, super carbon nanotube (SCNT), through molecular dynamics simulations. Results show that tensile strengths of the defective SCNTs are affected by the defect number, distribution continuity and orientation. Single-defect brings 0 ~ 25% reduction of the tensile strength with the dependency on defect position and the reduction is over 50% when the defect number increases to three. The distribution continuity induces up to 20% differences of tensile strengths for SCNTs with the same defect number. A smaller arranging angle of defects to the tensile direction leads to a higher tensile strength. Defective SCNTs possess various modes of stress concentration with different concentration degrees under the combined effect of defect number, arranging direction and continuity, for which the underlying mechanism can be explained by the effective crack length of the fracture mechanics. Fundamentally, the force transmission mode of the SCNT controls the influence of defects and the cases that breaking more force transmission paths cause larger decreases of tensile strengths. Defects are non-negligible factors of the mechanical properties of CNT-based networks and understanding the influence of defects on CNT-based networks is valuable to achieve the proper design of CNT-based electronic devices with better performances. Graphical Abstract

"Challenges of using educational platforms and suggestions to address them from the perspective of first-field students at Al Sharqiyah University, Sultanate of Oman"

The study aimed to explore the challenges of using educational platforms and proposals to address them from the point of view of the third-year students at Al-Sharqiya University. The descriptive approach was used on a sample of the third-year students at Al-Sharqiya University in the specialization of the first field, consisting of (100) students. The study tool consisted of a two-axis questionnaire to identify the challenges of Use of educational platforms and proposals to address them. The study concluded that among the main challenges of students' use of educational platforms are weak Internet networks and their lack of coverage in some places, some students not having their own computers, and the lack of technical support when needed. The results showed that among the proposals to address the challenges are the following: Strengthening internet networks in some areas and making them available for free for educational purposes, and providing personal computers for students who need them at subsidized prices and an easy payment method, in addition to providing the necessary technical support through the establishment of a special platform that includes answering questions directly, as well as educating students about the harms of staying long hours in front of electronic devices. The results of this study were discussed in the light of latest reviewed literature followed by recommendations and suggestions for future studies and investigations.

Study on Black Phosphorus Characteristics Using a Two-Step Thinning Method

A mild two-step method of black phosphorus (BP) flake thinning was demonstrated in this article. Slight ultraviolet–ozone (UVO) radiation followed by an argon plasma treatment was employed to oxidize mechanically exfoliated BP flakes and remove the surface remains of previous ozone treatment. The annealing process introduced aims to reduce impurities and defects. Low damage and efficient electronic devices were fabricated in terms of controlling the thickness of BP flakes through this method. These results lead to an important step toward the fabrication of high-performance devices based on two-dimensioned materials.

Mortality of people over working age in the context of COVID-19 pandemic

Проанализирована смертность лиц старше трудоспособного возраста (женщины 55+ и мужчины 60+) в условиях пандемии COVID-19 для определения потенциальной возможности её предотвращения. Использовали информацию базы данных РФС-ЕМИАС Москвы за 2019, 2020 и 2021 гг. (за периоды до 15 июня). Сделано заключение, что на фоне более корректного учета причин смерти в 2021 г., связанных с инфицированием вирусом SARS-CoV-2, вклад психических расстройств и болезней эндокринной системы в структуру причин смерти лиц старше трудоспособного возраста без учета случаев смерти от COVID-19 превышает показатели 2019 г. Рост смертности от заболеваний этих классов в значительной степени является следствием экзогенного стресса, связанного с пандемией, изоляцией лиц 65 лет и старше в начале пандемии, снижением эффективности их медико-социальной поддержки. Недостатки в организации социальной помощи лицам старших возрастных групп, слабое внедрение новых информационных технологий и носимых электронных устройств в практическую работу здравоохранения, малые масштабы общественных инициатив в области социальной помощи привели к потерям населения, которые могли бы быть предотвращены в период пандемии. The mortality of people over working age (women 55+ and men 60+) was analyzed in the context of COVID-19 pandemic in order to determine the potential for its prevention. The information from the Moscow mortality database for 2019, 2020 and 2021 (up to June 15) was used. Against the background of more correct accounting of death causes associated with SARS-CoV-2 virus infection in 2021, the contributions of mental disorders and endocrine diseases to the structure of death causes (excluding deaths from COVID-19) for people over working age are more than in 2019. The increase in mortality from diseases of these classes is largely a consequence of exogenous stress associated with a pandemic, isolation of people older 64 years and a decrease in the effectiveness of medical care. It was concluded that indirect losses from COVID-19 include avoidable mortality of elderly caused by shortcomings in organization of social assistance for them, the weak introduction of new information technologies and wearable electronic devices into the practical work of health care, small scale of public initiatives in the field of social assistance.

Advances in Selective Flotation and Leaching Process in Metallurgy

Metals are a finite resource that are necessary to maintain living standards in modern society, due to their countless applications, such as transportation vehicles, building and construction, household appliances, electronic devices, etc. [...]

The fourth fundamental circuit element: principle and applications

The relationships between four basic circuit variables - voltage (v), current (i), charge (q), and magnetic flux (ϕ) - have defined three fundamental circuit elements: resistor, capacitor, and inductor. From a symmetry view, there is a fourth fundamental circuit element defined from the relationship between charge and magnetic flux. Historically, a device called memristor was considered to be the fourth element, but it has caused intense controversy because the memristor is conceived based on a nonlinear i-v relationship rather than a direct q-ϕ relationship. Alternatively, a direct correlation between trapped charge (q) and magnetic flux (ϕ) can be built up by employing the magnetoelectric (ME) effects, i.e., magnetic field control of electric polarization and electric field control of magnetization. In this review, we summarize recent progress on the principle and applications of the fourth circuit element based on the ME effects. Both the fourth linear element and nonlinear memelement, termed transtor and memtranstor, respectively, have been proposed and experimentally demonstrated. A complete relational diagram of fundamental circuit elements has been constructed. The transtor with a linear ME effect can be used in a variety of applications such as the energy harvester, tunable inductor, magnetic sensor, gyrator, and transformer etc. The memtranstor showing a pinched hysteresis loop has a great potential in developing low-power nonvolatile electronic devices. The principle is to utilize the states of the ME coefficient αE=dE/dH, instead of resistance, magnetization or electric polarization to store information. Both nonvolatile memories and logic functions can be implemented using the memtranstors, which provides a candidate route toward the logic-in-memory computing system. In addition, artificial synaptic devices that are able to mimic synaptic behaviors have also been realized using the memtranstor. The fourth circuit element and memelement based on the ME effects provide extra degrees of freedom to broaden circuit functionalities and develop advanced electronic devices.