Direct numerical simulation of an iron rain in the magma ocean

International audienceCore formation in terrestrial planets is a complex process, possibly involving several mechanisms. This paper presents a direct numerical simulation of one of these, the separation of an emulsion of metal in a magma ocean. The model, using a fully Lagrangian approach called the moving particle semi-implicit method, solves the equations of fluid dynamics, including a proper treatment of surface tension. It allows investigation of the balances controlling the distribution of drop size and velocity, in both two- and three-dimensional situations. A scaling analysis where buoyancy is balanced by both surface tension and inertia correctly predicts the average values in these quantities. The full calculation gives an average drop radius of 1.5 cm falling at a velocity of about 30 cm s^-1. Analysis of the full distribution remains interesting and shows that a significant part of the smallest droplets is entrained upward by the return flow in molten silicate and might be entrained by succeeding thermal convection. In addition, we investigate the conversion of gravitational energy into viscous heating and the thermal equilibration between both phases. We find that viscous heating is essentially produced at the surface of iron drops and that thermal equilibration is dominated by advection. Scaling thermal diffusion to chemical diffusion leads to the estimation that the latter would happen in less than 100 m in the magma ocean

自脱コンバインロボットのための自動排出システム

京都大学0048新制・課程博士博士(農学)甲第17832号農博第2017号新制||農||1016(附属図書館)学位論文||H25||N4789(農学部図書室)30647京都大学大学院農学研究科地域環境科学専攻(主査)教授 飯田 訓久, 教授 近藤 直, 教授 清水 浩学位規則第4条第1項該当Doctor of Agricultural ScienceKyoto UniversityDFA

Efficient Enumeration of Dominating Sets for Sparse Graphs

A dominating set D of a graph G is a set of vertices such that any vertex in G is in D or its neighbor is in D. Enumeration of minimal dominating sets in a graph is one of central problems in enumeration study since enumeration of minimal dominating sets corresponds to enumeration of minimal hypergraph transversal. However, enumeration of dominating sets including non-minimal ones has not been received much attention. In this paper, we address enumeration problems for dominating sets from sparse graphs which are degenerate graphs and graphs with large girth, and we propose two algorithms for solving the problems. The first algorithm enumerates all the dominating sets for a k-degenerate graph in O(k) time per solution using O(n + m) space, where n and m are respectively the number of vertices and edges in an input graph. That is, the algorithm is optimal for graphs with constant degeneracy such as trees, planar graphs, H-minor free graphs with some fixed H. The second algorithm enumerates all the dominating sets in constant time per solution for input graphs with girth at least nine

Efficient Enumeration Algorithm for Dominating Sets in Bounded Degenerate Graphs (Foundations and Applications of Algorithms and Computation)

Dominating sets are fundamental graph structures. However, enumeration of dominating sets has not received much attention. This study aims to propose an efficient enumeration algorithms for bounded degenerate graphs. The algorithm enumerates all the dominating sets for k-degenerate graphs in O(k) time per solution using O(n+m) space. Since planar graphs have a constant degeneracy, this algorithm can enumerate all such sets for planar graphs in constant time per solution

Cheek-splitting technique for marginal mandibulectomy : a novel approach

When performing marginal mandibulectomy, ensuring complete tumor removal and preventing postoperative iatrogenic mandibular fracture are essential. Pathological fracture can result due to stress concentration at the site requiring acute angle resection. To perform marginal mandibulectomy without making acute angles in patients with a lesion in the molar or more posterior region, a submandibular or transbuccal approach is necessary. Compared to the submandibular approach, the transbuccal approach is considered useful as it reduces operative time and prevents injury to the facial and mental nerves. Additionally, this approach does not leave a scar in the surgical field, which is beneficial in subsequent neck dissection for late neck metastasis. Here, we report 2 cases of lower gingival carcinoma in which satisfactory aesthetic outcomes were achieved with an improved cheek-splitting technique for marginal mandibulectomy using a transbuccal approach, taking into consideration the angle of the mouth, design of the triangular flap, and modiolus

Development and fabrication of electro-magnetic shock tube with high resolution spectrometer for stopping power measurement in atomic hydrogen gas

Stopping power measurement in matter is very important for heavy-ion fusion and heavyion- driven high-energy density physics [1]. The database of the stopping power has been developed for many elements and compounds under a normal temperature and pressure [2, 3]. However, the stopping cross section can change due to a change of electronic state in the target such as excitation and ionization [4, 5]. Especially, there is few experimental results for the energy loss of charged particles in a dissociated target. Hydrogen is a suitable element to investigate the dissociation effect because it has only one valence electron..

Development and fabrication of electro-magnetic shock tube with high resolution spectrometer for stopping power measurement in atomic hydrogen gas

Stopping power measurement in matter is very important for heavy-ion fusion and heavyion- driven high-energy density physics [1]. The database of the stopping power has been developed for many elements and compounds under a normal temperature and pressure [2, 3]. However, the stopping cross section can change due to a change of electronic state in the target such as excitation and ionization [4, 5]. Especially, there is few experimental results for the energy loss of charged particles in a dissociated target. Hydrogen is a suitable element to investigate the dissociation effect because it has only one valence electron..