Distance Between Two Arbitrary Unperturbed Orbits     

Roman V. Baluyev  Konstantin V. Kholshevnikov 《Celestial Mechanics and Dynamical Astronomy》2005,91(3-4):287-300

In the paper by Kholshevnikov and Vassilie, 1999, (see also references therein) the problem of finding critical points of the distance function between two confocal Keplerian elliptic orbits (hence finding the distance between them in the sense of set theory) is reduced to the determination of all real roots of a trigonometric polynomial of degree eight. In non-degenerate cases a polynomial of lower degree with such properties does not exist. Here we extend the results to all possible cases of ordered pairs of orbits in the Two–Body–Problem. There are nine main cases corresponding to three main types of orbits: ellipse, hyperbola, and parabola. Note that the ellipse–hyperbola and hyperbola–ellipse cases are not equivalent as we exclude the variable marking the position on the second curve. For our purposes rectilinear trajectories can be treated as particular (not limiting) cases of elliptic or hyperbolic orbits.  相似文献   

Testing supply-side climate policies for the global steam coal market—can they curb coal consumption?     

Roman Mendelevitch 《Climatic change》2018,150(1-2):57-72

The achieved international consensus on the 1.5–2 °C target entails that most of current fossil fuel reserves must remain unburned. A major contribution has to come from coal as both the most abundant and the most emission-intensive fuel. Currently, a majority of climate policies aiming at reducing coal consumption are directed towards the demand side. In the absence of a global carbon-pricing regime, these policies are prone to carbon leakage and other adverse effects. Supply-side climate policies present an alternative and increasingly discussed approach to reduce the consumption of fossil fuels. In this article, I employ a numerical model of the international steam coal market to examine two supply-side policies that are currently discussed in academic literature and by policy-makers, alike: (1) a production subsidy reform introduced in major coal-producing countries and (2) a globally implemented moratorium on new coal mines. The model simulates global patterns of coal supply, demand, and international trade, with endogenous investment in coal production and transportation capacities. I find that mere production subsidy removal, while associated with a small positive total welfare effect, leads to a minor reduction of global emissions. By contrast, a mine moratorium induces a much more pronounced reduction in global coal consumption by effectively limiting coal availability and strongly increasing prices. Depending on the specification of reserves, the moratorium can induce a coal consumption path consistent with the 1.5–2 °C target.  相似文献   

Interpreting complex fluvial channel and barform architecture: Carboniferous Central Pennine Province,northern England          下载免费PDF全文

Roman Soltan  Nigel P. Mountney 《Sedimentology》2016,63(1):207-252

The Bashkirian Lower Brimham Grit of North Yorkshire, England, is a fluvio‐deltaic sandstone succession that crops out as a complex series of pinnacles, the three‐dimensional arrangement of which allows high‐resolution architectural analysis of genetically‐related lithofacies assemblages. Combined analysis of sedimentary graphic log profiles, architectural panels and palaeocurrent data have enabled three‐dimensional geometrical relationships to be established for a suite of architectural elements so as to develop a comprehensive depositional model. Small‐scale observations of facies have been related to larger‐scale architectural elements to facilitate interpretation of the palaeoenvironment of deposition to a level of detail that has rarely been attempted previously, thereby allowing interpretation of formative processes. Detailed architectural panels form the basis of a semi‐quantitative technique for recording the variety and complexity of the sedimentary lithofacies present, their association within recognizable architectural elements and, thus, the inferred spatio‐temporal relationship of neighbouring elements. Fluvial channel‐fill elements bounded by erosional surfaces are characterized internally by a hierarchy of sets and cosets with subtly varying compositions, textures and structures. Simple, cross‐bedded sets represent in‐channel migration of isolated mesoforms (dunes); cosets of both trough and planar‐tabular cross‐bedded facies represent lateral‐accreting and downstream‐accreting macroforms (bars) characterized by highly variable, yet predictable, patterns of palaeocurrent indicators. Relationships between sandstone‐dominated strata bounded by third‐order and fifth‐order surfaces, which represent in‐channel bar deposits and incised channel bases, respectively, chronicle the origin of the preserved succession in response to autocyclic barform development and abandonment, major episodes of incision probably influenced by episodic tectonic subsidence, differential tilting and fluvial incision associated with slip on the nearby North Craven Fault system. Overall, the succession represents the preserved product of an upper‐delta plain system that was traversed by a migratory fluvial braid‐belt system comprising a poorly‐confined network of fluvial channels developed between major sandy barforms that evolved via combined lateral‐accretion and downstream‐accretion.  相似文献