Simulation of Young's moduli for hexagonal ZnO [0 0 0 1]-oriented nanowires: first principles and molecular mechanical calculations

The authors thank A Gulans, B Polyakov and S Vlassov for stimulating discussions. This study has been supported by the ERA.Net RUS Plus project No. 237 Watersplit. AB, RE and SL acknowledge the financial support by the Russian Foundation for Basic Research (Grant No. 17-03-00130-a) and the assistance of the Saint Petersburg State University Computer Center in the accomplishment of high-performance computations.Morphologically reproducible wurtzite-structured zinc oxide nanowires (ZnO NWs) can be synthesized by different methods. Since ZnO NWs have been found to possess piezoelectricity, a comprehensive study of their mechanical properties, e.g. deformations caused by external compression or stretching, is one of the actual tasks of this paper. We have calculated wurtzite-structured [0 0 0 1]-oriented ZnO NWs whose diameters have been varied within 1–5 nm and 1–20 nm ranges when using either ab initio (hybrid DFT-LCAO) or force-field (molecular mechanical) methods, respectively (the minimum diameter dNW of experimentally synthesized NWs has been estimated on average to be ~20 nm). When using both chosen calculation approaches, the values of Young's moduli determined for the mentioned ranges of NW diameters have been found to be qualitatively compatible (168–169 GPa for 5 nm NW thickness), whereas results of molecular mechanical simulations on YNW for 20 nm-thick NWs (160–162 GPa) have been qualitatively comparable with those experimentally measured along the [0 0 0 1] direction of NW loading. In all the cases, a gradual increase of the NW diameter has resulted in an asymptotic decrease of Young's modulus consequently approaching that (Yb) of wurtzite-structured ZnO bulk along its [0 0 0 1] axis. The novelty of this study is that we combine the computation methods of quantum chemistry and molecular mechanics, while the majority of previous studies with the same aim have focused on the application of different classical molecular dynamical methods.ERA.Net RUS Plus project No. 237 Watersplit; Russian Foundation for Basic Research (Grant No. 17-03-00130-a); Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Improvement of distance protection algorithms based on phasor measurements

Distance protection of overhead lines is widely used and is continually being improved. However, the distance protection cannot work stably and is blocked in several electromechanical transients. Additionally, a non-linear arc can affect the stability of the distance protection in case of a short-circuit. The authors consider ways to improve distance protection during such transients. In particular, this paper proposes the use of synchronized phasor measurement technology to improve the efficiency of distance protection. This paper considers a new approach for the analysis of electromechanical and electromagnetic transients in a power system using process synchrophasors. As examples, cases of a short-circuit in a line with oneway and two-way powers are considered. The authors consider the influence of a non-linear arc at the fault point and consider the possibility of the coincidence of the electromechanical and electromagnetic transients. The result is a new algorithm for operating distance protection, an improvement in the parametric method for determining the location of line damage. The calculations performed and mathematical modeling confirm the effectiveness of the proposed algorithm

Application of synchronized phasor measurements in RPA devices of distribution networks

The paper discusses the efficiency of RPA devices application with support of synchronized phasor measurements (SPM) at the step-down substations and in 6-20 kV distribution networks. The main part of the paper presents a description of the algorithm developed by the authors for determining the damaged cable line during single-phase ground faults (SGF) in 6-20 kV distribution networks with compensated and isolated neutral. The proposed algorithm makes it possible to realize reliable, fast-acting, and selective SGF protection in distribution cable networks acting either on a signal or on a trip. Based on the SGF protection using SPM, an SGF localization system can be created. This makes it easier to find a damaged cable line in the distribution network. The report presents the conditions for the application of this algorithm, which ensure the stability and reliability of its operation under various parameters of the network. The paper authors propose options for improving the SGF protection algorithm, which allows expanding the field of its application. The results of virtual modeling confirm the effectiveness of SGF protection based on the SPM using the developed algorithm. The final part of the paper contains examples demonstrating other areas of SPM application for RPA devices of step-down transformers, substations, cable distribution networks

Digital phenotyping technologies: an emerging tool in genomic selection and animal welfare science?

Farm animals provide about 30% of humanity’s food requirements [1]. The world’s population’s demand for animal products is expected to keep growing. New technologies in animal husbandry can make it possible to meet this demand and to reduce its impact on the environment. Genomic selection plays a key role in this process as a promising and safe method for improving genetic qualities of farm animals. Before the widespread of genomic selection, high cost of genotyping was the main factor holding back an improvement of animal farming. However, today, the bottleneck in genomic selection is a limited amount of high-quality phenotypic data, which is still either difficult or too costly to obtain [2]. New technologies in animal phenotyping become of special attention. The current paper reviews the next-generation technologies in animal phenotyping and revels the main challenges limiting its widespread in the example of dairy cattle

Applications of synchrophasor measurement to improve the reliability and efficiency of power systems

The article deals with the development of software and hardware systems that expand the scope of application of the synchrophasor measurement (SPM) technology. The following tasks are considered as applications: automation of 6-10 kV distribution networks with the possibility of localization a damaged cable line in case of single-phase earth faults, monitoring the state of power transformers, analyzing low-frequency oscillations in the power system

Improving the efficiency and reliability of RPA systems of digital step-down substations and digital grids

The article discusses examples of synchrophasor measurement (SPM) technology application for implementation of inherently selective protection for 35-220 kV step-down substations and 6-20 kV distribution points

Wide area monitoring, protection, automation, and control systems for medium voltage networks

Distribution medium voltage networks have a branched structure, many power centers, longcable and overhead lines. This complicates the process of their automation, since significant capital costs for new equipment are required. New solutions based on modern technologies can help speed up this process and make it more efficient. The authors propose the use of synchronized phasor measurement technology for automating medium voltage networks. This paper considers approaches that describe the possibilities of implementing the WAMPAC principles in such networks, provides several examples where these principles apply

Porogen Concentration Effect on the Pore Structure and Properties Evolution of Polymer Monolith Based on Oligocarbonate Dimethacrylate OCM-2

Porous polymer monolith materials of 2-mm thickness were obtained by visible light-induced radical polymerization of oligocarbonate dimethacrylate (OCM-2) in the presence of 1-butanol (10 to 70 wt %) as a porogenic additive. The pore characteristics and morphology of polymers were studied by mercury intrusion porosimetry and scanning electron microscopy. Monolithic polymers with both open and closed pores up to 100 nm in size are formed when the alcohol content in the initial composition is up to 20 wt %. The pore structure in such materials is a system of holes in the bulk of the polymer (hole-type pores). Open interconnected pores with a specific volume up to 2.22 cm3/g and modal pore size up to 10 microns are formed in the volume of the polymer with 1-butanol content of more than 30 wt %. Such porous monoliths are a structure of covalently bonded polymer globules (interparticle-type pores). The free space between the globules represents a system of open interconnected pores. In the transition region of 1-butanol concentrations (from 20 to 30 wt %), areas with both structures and intermediate frameworks, as well as honeycomb structures of polymer globules connected by bridges, are fixed on the polymer surface. It was found that the transition from one type of pore system to another is accompanied by a sharp change in the strength characteristics of the polymer. Approximation of experimental data using the sigmoid function made it possible to determine the concentration of the porogenic agent in the vicinity of which the percolation threshold is observed