Patterns and structures of land use change in the three rivers headwaters region of China

10.1371/journal.pone.0119121PLoS ONE103e011912

High photo-excited carrier multiplication by charged InAs dots in AlAs/GaAs/AlAs resonant tunneling diode

We present an approach for the highly sensitive photon detection based on the quantum dots (QDs) operating at temperature of 77K. The detection structure is based on an AlAs/GaAs/AlAs double barrier resonant tunneling diode combined with a layer of self-assembled InAs QDs (QD-RTD). A photon rate of 115 photons per second had induced 10nA photocurrent in this structure, corresponding to the photo-excited carrier multiplication factor of 10^7. This high multiplication factor is achieved by the quantum dot induced memory effect and the resonant tunneling tuning effect of QD-RTD structure.Comment: 10 pages,5 figures. Submitted to Applied Physics Letter

Influence of moisture absorption on electrical properties and charge dynamics of polyethylene silica-based nanocomposites

The use of nanocomposites as dielectric materials is expected to lead to improved electrical performance. However, recent research has shown that moisture absorption can cause a deterioration in the electrical performance of nanocomposites. Although it is generally accepted that hydroxyl groups attached to nanoparticle surfaces are the main cause of moisture absorption, the impact of this absorption on the electrical properties of nanocomposites is still not fully understood. In this paper, a series of measurements, including thermogravimetric analysis, DC breakdown, surface potential decay and space charge, are conducted with the aim of determining the impact of moisture absorption on the electrical properties of polyethylene/silica nanocomposites. The results show that the loading ratio of nanosilica and the humidity of the conditioning environment determine the amount of absorbed moisture. According to the Zhuravlev model, the main contribution to the deterioration in electrical properties of nanocomposites comes from the large amount of moisture absorbed in multilayer form. It is found that the loading ratio of nanosilica is the most significant factor in reducing DC breakdown strength

Editorial Note

We are pleased to publish this special issue of Ethnographic Encounters on digital research methods. The idea of this theme arose as we noted how the Covid-19 pandemic shifted many aspects of our lives to online contexts, and we reflected upon what this shift has meant for research practices. For the first time in the history of the journal, we have opened our submissions to all the departments of the University of St Andrews and to both undergraduate and postgraduate students

Study on Quantification Method for Dispersion and Distribution of Sphere/-like Particles and Relationship with AC/DC Breakdown Strength in Polymer Nanocomposites

Polymer nanocomposites are more and more researched and employed as dielectrics in electrical power equipment. However, the bad dispersion and distribution of particles are often reported to deteriorate the dielectric properties of polymer nanocomposites. In most cases, researchers tend to use SEM/TEM images with imprecise descriptions to describe these two factors, and there was still no clear relationship between their quantified particle dispersion characteristics and dielectric properties of polymer nanocomposites. This work is to, first, propose a combined quantification method to estimate the dispersion and distribution of spherical/ellipsoidal particles/aggregates in polymer nanocomposites based on SEM images of epoxy SiO2 nanocomposites. Based on the proposed quantification method, epoxy nanocomposite with surface treated SiO2 shows overall better dispersion and distribution of particles/aggregates than those with untreated ones. The presence of agglomerations would lead to the enhancement of mobility of charge carriers and thus reduction of breakdown strength, which become more obvious with the growth of filler loadings. It is found that, in AC breakdown tests, dispersion and distribution of particles/aggregates show little influence on the reduction of AC breakdown strength. However, those should be the main factor which influences the DC breakdown strength in epoxy nanocomposites with a variation of filler loading concentrations

How Chief Executive Officers’ first-hand experience of the Great Chinese Famine affects risk-taking?

Abstract To understand the influence of Chief Executive Officers’ (CEOs) early life experiences on their firms’ strategic decision-making, here we explore the impacts of CEOs’ experience of the Great Chinese Famine (1959–1961) on their cognitions and firm risk-taking. Using longitudinal data from publicly listed companies in China from 2006 to 2017, we found that CEOs who experienced the 3-year-long famine are more risk-averse, but that this relationship only exists among CEOs who experienced the famine during their formative years (between 6 and 18 years old). In addition, we found that the negative relationship between CEOs’ early experiences of famine and firms’ risk-taking is weaker when the firm is state-owned and stronger when the firm is facing fiercely competitive markets. We also take a step further to explore the impact of the severity of the famine on individuals, and we find that there is a positive relationship between the severity of the famine and firm risk-taking only within a moderate level. When the severity exceeds a certain level, CEOs are reluctant to take risks with the increase in the severity of the famine. Our findings provide a new theoretical and practical perspective in studying the relationship between CEOs’ early experiences with disaster and firm risk-taking