Three-dimensional calculations of high- and low-mass planets embedded in protoplanetary discs

We analyse the non-linear, three-dimensional response of a gaseous, viscous protoplanetary disc to the presence of a planet of mass ranging from 1 Earth mass (1 M_⊕) to 1 Jupiter mass (1 M_J) by using the zeus hydrodynamics code. We determine the gas flow pattern, and the accretion and migration rates of the planet. The planet is assumed to be in a fixed circular orbit about the central star. It is also assumed to be able to accrete gas without expansion on the scale of its Roche radius. Only planets with masses   M _p≳ 0.1 M_J  produce significant perturbations in the surface density of the disc. The flow within the Roche lobe of the planet is fully three-dimensional. Gas streams generally enter the Roche lobe close to the disc mid-plane, but produce much weaker shocks than the streams in two-dimensional models. The streams supply material to a circumplanetary disc that rotates in the same sense as the orbit of the planet. Much of the mass supply to the circumplanetary disc comes from non-coplanar flow. The accretion rate peaks with a planet mass of approximately 0.1 M_J and is highly efficient, occurring at the local viscous rate. The migration time-scales for planets of mass less than 0.1 M_J, based on torques from disc material outside the Roche lobes of the planets, are in excellent agreement with the linear theory of type I (non-gap) migration for three-dimensional discs. The transition from type I to type II (gap) migration is smooth, with changes in migration times of about a factor of 2. Starting with a core which can undergo runaway growth, a planet can gain up to a few M_J with little migration. Planets with final masses of the order of 10 M_J would undergo large migration, which makes formation and survival difficult.     

驱动重联过程中等离子体团的聚合

本文对驱动重联过程作了二维可压缩磁流体动力学模拟．对于长的计算域（１：４），在持续入流的作用下形成了双重磁岛结构，这些磁岛在向外运动的过程中不断靠近，逐渐聚合成为一个大的等离子体团，并继续向外运动．这说明在地球磁层顶和磁尾所观测到的大尺度磁结构，很可能是在驱动重联过程中，由较小的等离子体团聚合后形成的．并初步揭示了在空间等离子体中，磁岛的聚合过程难以直接观测的动力学原因．     

Planetary migration to large radii

There is evidence for the existence of massive planets at orbital radii of several hundred au from their parent stars where the time-scale for planet formation by core accretion is longer than the disc lifetime. These planets could have formed close to their star and then migrated outwards. We consider how the transfer of angular momentum by viscous disc interactions from a massive inner planet could cause significant outward migration of a smaller outer planet. We find that it is in principle possible for planets to migrate to large radii. We note, however, a number of effects which may render the process somewhat problematic.     

Delay time optimization in blasting operations for mitigating the vibration-effects on final pit walls' stability

Blasting induced vibration is one of the fundamental problems in the open-pit mines and intense vibration can cause critical damage to structures and plants nearby the open-pit mines, especially to the final pit wall's stability. It is very important to study how to control vibration induced by blasting in the mitigation of negative effects of blasting in open-pit mines. This study aims to examine the propagation of blasting induced ground vibrations and find the feasible approaches to reduce the harmful effects of vibrations induced by blasting on the final pit wall's stability. For this purpose, a series of field experiments were conducted in XinQiao Mining Co. Ltd. Sixty-six events and the blasting parameters of these shots were carefully recorded. During the statistical analysis of the collected data, the predictor equation proposed by the United States Bureau of Mines (USBM) was used to establish a relationship between the Peak Particle Velocity (PPV) and the Scaled Distance (SD) factor. The relationship between PPV and SD was determined and proposed to be used in this open-pit mine. Control of maximum charge amount per delay and the selection optimum interval time to reduce the intensity of vibration by waveform interference were applied in practice. Based on the field experiments, we can determine the maximum charge amount per delay and 15 ms delay were proposed to be used in this site, and a decrease in vibration of 24.5% was obtained.     

Spatial and seasonal variations in the water quality of Jinhae Bay,Korea

The chemical and biological characteristics of surface waters in Jinhae Bay were investigated over four seasons to understand water quality in light of the growing industrialisation occurring within this area. Jinhae Bay includes four smaller bays: Masan; Hangam; Jindong; and Gohyun. The water quality in Jinhae Bay varied spatially and seasonally. The water quality of both Hangam Bay and Masan Bay was highly degraded, demonstrating high concentrations of ammonia, nitrate, chlorophyll a and particulate organic carbon. Contamination from sewage was the dominant cause of the water quality deterioration in these bays. Conversely, the water quality in Jindong Bay and Gohyun Bay was not as severely affected as that of the above two bays. Water quality in Jinhae Bay was particularly poor in summer when nutrient loading was highest due to the run-off associated with high precipitation. Principal component analysis indicated that nitrogen contamination was a major factor influencing the water quality of Jinhae Bay. The effective reduction in high-nitrogen discharges is essential to improve water quality in Jinghae Bay.     

0518号台风"达维"风暴潮分析

2005年9月26日凌晨4时,32年来最强的台风“达维”在海南省万宁市山根镇沿海地区登陆。“达维”一路横扫,肆虐全省18市县,重创海南,直接经济总损失达116.47亿元。本文对这次台风的风暴潮特点及其成因进行了较深入的分析,初步探讨灾情分布,为今后该类台风风暴潮预报积累经验及防灾减灾提供基础资料依据。     

新疆包古图斑岩铜矿床成矿流体及成矿物质来源——来自硫、氢和氧同位素证据

包古图大型斑岩铜矿位于准噶尔盆地西缘。铜矿化主要呈浸染状、细脉浸染状分布于似斑状(石英)闪长岩、闪长玢岩、隐爆角砾岩和少量花岗闪长岩中。依据矿脉的穿插关系和矿物组合,成矿过程经历了黑云母-钾长石-钠长石阶段、石英-硫化物阶段和石英碳酸盐阶段。矿脉中石英的δDSMOW值介于-107‰～-86‰,δ18OSMOW值变化于11.3‰～16.2‰,δ18OH2O值为4.4‰～9.3‰,表明成矿流体来源为深源的岩浆水。硫化物的δ34S值介于-5.1‰～0.7‰,平均为-1.8‰,表明硫来源于深部岩浆或地幔。结合Ⅱ、Ⅲ和Ⅴ号含矿岩体锆石LA-ICP-MSU-Pb年龄及辉钼矿Re-Os年龄,推断包古图铜矿床成矿作用发生在晚石炭世,与中酸性斑岩体的侵入有密切成因关系。