Do Leonardo Da Vinci’s Drawings, Room Acoustics And Radio Astronomy Have Anything In Common?

After introducing Leonardo da Vinci’s (LdV) predecessors in the field of light propagation research, his drawings on the topic of focussing light through a spherical mirror are analysed. The discovery of LdV is presented, according to which, at an infinitely distant source of rays, a small fragment of the canopy is enough to generate a focus, while the rest of the mirror forms caustics for which LdV did not indicate an application. An analytical description of the energy concentration in the focus and on the caustics is given, together with its reference to the geometric representation of the acoustic field in rooms. Using symmetry in the description of energy relations in acoustics and electromagnetism, the interference that occurs on the caustics produced by the acoustic and electromagnetic wave is discussed. It is explained why in the sound field in existing halls, instead of a whole caustic only its cusp is observed, which is perceived as a point-like sound focus. The size of the mirror aperture, shown graphically by LdV, is determined. How the development of receiving techniques increased the mirror aperture compared to the LdV estimate is also shown. The implementation of these improvements is presented via the example of the Arecibo and FAST radio telescopes.

CHINA'S ENERGY DIPLOMACY TOWARDS RUSSIA IN THE EASTERN SIBERIA PIPELINE DEVELOPMENT DURING PRESIDENT XI JINPING PERIOD

China is a very active country in building energy diplomacy relations towards Russia. Since the end of the Cold War, the intensity of energy relations between the two countries has been increasing, one of which is related to the Eastern Siberian pipeline project. The Eastern Siberian pipeline project is a strategic project for China to maintain the stability of their energy security in the future. This is what makes China under the leadership of Xi Jinping, increasingly seeking to improve their energy diplomacy relations towards Russia in an effort to develop the Eastern Siberian pipeline project which includes two major projects, specifically oil pipeline through the Eastern Siberian Pasific Ocean (ESPO) and the natural gas pipeline through the Power of Siberia. Using qualitative research methods and literature reviews, the authors sought to provide an in-depth analysis of China's implementation of energy diplomacy against Russia in the development of the Eastern Siberian pipeline. China's energy diplomacy towards Russia is part of efforts to diversify China's energy imports many involving actors of China's national energy companies. This research also proves that energy cooperation relationships are not only built within bilateral frameworks but also in multilateral frameworks as part of China-Russia efforts to accelerate the development of the Eastern Siberian pipeline.

The Green Deal and the Resilience of EU-Russian Energy Relations

In this article, the influence of the European Union’s (EU) Green Deal on its energy relations with Russia is analyzed. Two models of resilience are identified in the EU’s discourse. One aims at achieving resilience at the level of the EU’s energy sector (the “microsystem” for the purpose of this study) while destroying the system of EU-Russia relations (the “macrosystem”). The other aims at achieving resilience in the micro- and macrosystem at the same time. Empirically, the study relies on EU documents and speeches by its national and supranational representatives. Three cases are studied. The first covers competition of two models of resilience in the principles that the EU defined for its relations with Russia. The second case involves investments that slow down the development of renewable sources of energy in favour of natural gas. This case demonstrates how resilience can be achieved as a return to the previous pattern (bouncing back). Although it can be achieved both at the EU-only level and at the level of the EU and its relations with Russia, it clearly favours the latter. The third case involves the import of hydrogen, which creates possibilities for resilience both at the microsystem alone and at the micro- and macrosystems at the same time. This latter option is achieved through adaptation to new challenges (bouncing forward). The author concludes by comparing the two models of resilience. The model that prioritizes the microsystem’s resilience and challenges the macrosystem is based on the synthesis of environmental and geopolitical logics. The other model is based on economic and market logics, but the EU’s normative leadership is a prerequisite. The EU’s discourse demonstrates the viability of both models and related governance practices. Most likely, the two models will co-exist, but their relative importance will vary over time. This variation will be primarily determined by the EU’s internal constraints. However, Russia’s policy can facilitate the model of resilience, achieved in both the micro- and macrosystem.

Strongly direction-dependent magnetoplasmons in mixed Faraday–Voigt configurations

The electrostatic theory of surface magnetoplasmons on a semi-infinite magnetized electron gas is generalized to mixed Faraday–Voigt configurations. We analyze a mixed Faraday–Voigt type of electrostatic surface waves that is strongly direction-dependent, and may be realized on narrow-gap semiconductors in the THz regime. A general expression for the dispersion relation is presented, with its dependence on the magnitude and orientation of the applied magnetic field. Remarkably, the group velocity is always perpendicular to the phase velocity. Both velocity and energy relations of the found magnetoplasmons are discussed in detail. In the appropriate limits the known surface magnetoplasmons in the higher-symmetry Faraday and Voigt configurations are recovered.