Calculation of parameters of elementary nanocrystals of liquid metals at melting temperature

Method of calculation and calculated values of parameters of elementary nanocrystals of liquid metals at melting temperature are given. It has been shown that radii of elementary nanocrystals are from 2 nm to 12 nm, and the number of atoms in each elementary nanocrystal varies from 2000 to 100000. This provides liquid metals with a high solidification rate and explains the abnormally high diffusion coefficient in liquid metals compared to solid metals.

Germs, Social Networks and Growth

Does the pattern of social connections between individuals matter for macroeconomic outcomes? If so, where do differences in these patterns come from and how large are their effects? Using network analysis tools, we explore how different social network structures affect technology diffusion and thereby a country’s rate of growth. The correlation between high-diffusion networks and income is strongly positive. But when we use a model to isolate the effect of a change in social networks on growth, the effect can be positive, negative, or zero. The reason is that networks diffuse both ideas and disease. Low-diffusion networks have evolved in countries where disease is prevalent because limited connectivity protects residents from epidemics. But a low-diffusion network in a low-disease environment compromises the diffusion of good ideas. In general, social networks have evolved to fit their economic and epidemiological environment. Trying to change networks in one country to mimic those in a higher-income country may well be counterproductive.

Fan Aerodynamics With a Short Intake at High Angle of Attack

Fans that are designed to maintain thrust at the high angle of attack (AOA) flight condition could exploit the cruise fuel burn benefit of a shorter intake design. This article considers how the fan rotor radial pressure ratio distribution and tip velocity triangle can be designed to improve thrust when coupled to a short intake operating at high AOA. Two AOA values are investigated using unsteady computational fluid dynamics: 20 deg (attached flow) and 35 deg (separated flow). Thrust at high AOA is governed by three key loss and work input mechanisms. (i) Rotor choking loss: flow is accelerated around the intake bottom lip and enters the rotor with high Mach numbers. Fans designed with a tip-high radial pressure ratio distribution reduced choking loss with a separated intake compared to a mid-high design, particularly when the tip velocity triangle was designed with high diffusion instead of high camber. (ii) Rotor–separation interaction loss: the rotor ingests low mass flow when operating inside the separation and the casing boundary layer separates. High diffusion tip designs strengthened the casing separation, but this penalty did not outweigh improved choking loss. (iii) Work input in radial flows: high AOA generates strong radial flows through the rotor, which alter both the amount and the way work is imparted on the flow. Fans designed with a mid-high radial pressure ratio distribution imparted high work on streamlines migrating toward the hub. Consolidating these findings, we propose two design philosophies for improved thrust at high AOA: high work (mid-high radial pressure ratio distribution) or low loss (tip-high radial pressure ratio distribution with high diffusion tip velocity triangle).

Intergenerational contacts and Covid-19 spread: Omnipresent grannies or bowling together?

Many scientists are currently contributing research on SARS-CoV2, with social scientists focusing on demographic and behavioral aspects when it comes to the diffusion of the virus. Recent publications include valid contributions about the importance of population’s demographic composition to understand country-differences in fatalities, and some speculations about the origins of different pace and patterns of diffusion. Among them the idea that intergenerational contacts would contribute to explain the fast spread and high fatality among the elderly population in some countries. We argument that in order to contribute to the scientific knowledge speculation is not enough and acknowledge that in the absence of solid, comparable data it is difficult to bring these ideas to an empirical test. Further, we present a simulation experiment shedding serious doubts on the importance of intergenerational contacts to spread the virus on the elderly population but underlining, instead, the importance of the high connectedness within the elderly population. That southern Europeans are not bowling alone seems to be more relevant to explain high diffusion among elderly than their contact to their (grand-)children.

Multihoming with Dynamic Mobile Network Selection

This article describes how mobile operators occasionally fail to provide adequate service quality due to network overload, blackouts, or coverage white spots. Customers can increase the quality of connections by multihoming, i.e. using subscriptions of several operators. Multihoming is facilitated by an innovative reprogrammable embedded SIM (eSIM) that can enable dynamic switching between networks. Although eSIM multihoming is advantageous, its future is not definite, as it is affected by multiple factors and actors with conflicting business interests. This paper defines scenarios for the evolution of eSIM multihoming and its possible impact on competition by constructing qualitative system dynamics models based on expert interviews. The results show that depending on market conditions and actions of stakeholders, multihoming may reach high diffusion, find application in special use cases, or fail to take off. With high diffusion, competition between operators will become more dynamic, and market share will be defined by the number of served sessions.