基于地质–工程条件约束的可控冲击波煤层致裂行为数值分析

可控冲击波（CSW）岩层致裂技术作为岩层改造领域的一项变革性技术,已在煤层改造等方面取得显著应用效果,并在煤炭安全开采领域开展应用探索。然而,受实验及现场监测条件限制,前期对地质-工程因素约束下的CWS岩层致裂基本规律理解不足,制约了对致裂机理的探索及现场作业参数的优化。鉴于此,在阐述CSW煤层改造及其面临的工程科学问题基础上,采用基于连续介质力学的离散元方法（CDEM）开展数值模拟,以进一步揭示地应力、煤岩力学性质、冲击波加载条件约束下的CSW煤层致裂行为及其基本规律。结果显示,CSW加载条件对致裂效果的影响存在最优范围,过度加载会导致近井地带煤体崩解,煤粉产出率增加,造成煤储层伤害;同时,煤体破碎导致波阻抗及冲击波衰减速度增大,限制有效改造半径扩展;地应力增大,破裂半径、破裂度存在临界值,水平主应力差对CSW冲击裂隙形态、扩展方位及缝网连通程度存在显著影响。研究揭示,CSW煤岩致裂效果对力学性质的响应存在选择性:弹性模量与破裂半径、破裂度之间存在拐点临界值;黏聚力增大,煤岩脆性变小,致裂效果变差;抗拉强度似乎对CSW致裂效果没有明显影响。研究成果可为CSW作业煤层优选及参数优化措施提供参考。      

The possibility of emersion of the outer layers in a massive star simultaneously with iron-core collapse: A hydrodynamic model

We analyze the behavior of the outer envelope in a massive star during and after the collapse of its iron core into a protoneutron star (PNS) in terms of the equations of one-dimensional spherically symmetric ideal hydrodynamics. The profiles obtained in the studies of the evolution of massive stars up to the final stages of their existence, immediately before a supernova explosion (Boyes et al. 1999), are used as the initial data for the distribution of thermodynamic quantities in the envelope. We use a complex equation of state for matter with allowances made for arbitrary electron degeneracy and relativity, the appearance of electron-positron pairs, the presence of radiation, and the possibility of iron nuclei dissociating into free nucleons and helium nuclei. We performed calculations with the help of a numerical scheme based on Godunov's method. These calculations allowed us to ascertain whether the emersion of the outer envelope in a massive star is possible through the following two mechanisms: first, the decrease in the gravitational mass of the central PNS through neutrino-signal emission and, second, the effect of hot nucleon bubbles, which are most likely formed in the PNS corona, on the envelope emersion. We show that the second mechanism is highly efficient in the range of acceptable masses of the nucleon bubbles (≤0.01M _⊙) simulated in our hydrodynamic calculations in a rough, spherically symmetric approximation.     

地基观测的夜侧极光对行星际激波的响应

行星际激波与地球磁层相互作用通常会导致日侧极光活动增强,随后沿着极光卵的晨昏两侧向夜侧扩展的激波极光.行星际激波也可能直接导致夜侧扇区极光活动增强,甚至沉降粒子能通量的数量级可以与典型亚暴相比拟.本文首次利用我国南极中山站和北极黄河站连续多年积累的极光观测数据,对行星际激波与地球磁层相互作用期间地面台站在夜侧扇区(18—06MLT)观测的极光响应进行了分析.对18个极光观测事件的分析结果表明:行星际激波与磁层相互作用可以在夜侧触发极光爆发和极光微弱增强或静态无变化事件;太阳风-磁层能量耦合的效率以及磁层空间的稳定性决定着行星际激波能否触发极光爆发.     

浅析爆炸效应在人工增雨作业中的作用

文章分析了冲击波、声波、扰动气流场和超声气流等爆炸产物对环境气流场和云、降水质粒的影响及效应,结果表明:在人工播云中,含有爆炸效应的催化作业要比单纯的静力催化有更广泛的应用前景。     

Foreshock cavities and internal foreshock boundaries

We present two case studies of cluster encounters with foreshock cavities. For one event, we are able, for the first time, to accurately relate the observation of a foreshock cavity to the measured position of the bow shock. This allows us to compute the shock angle, a vital parameter in models of foreshock cavity formation, with greater confidence than any previous study. This cavity appears to be elongated along the magnetic field and we use the multispacecraft nature of the Cluster mission to constrain its field-parallel and -perpendicular extent. We show that this event is embedded within a region of field-aligned ion beams. This is the first time a foreshock cavity has been shown to be surrounded by foreshock ion beams. A second foreshock cavity is associated with a small rotation in the interplanetary magnetic field (IMF). We show that this event appears on the boundary between an interval when the spacecraft were inside the ion foreshock, and an excursion upstream. This is the first report of a foreshock cavity observed during the traversal of the global foreshock. This second event has some features expected from the new Sibeck et al. (2008) model of cavities as brief encounters with a spatial boundary in the global foreshock.     

超高压矿物研究进展

我国超高压矿物研究近十年来取得了重要进展.参与发现了5个超高压新矿物及若干待命名高压相,被国际矿物协会新矿物、命名与分类委员会批准和命名的超高压矿物包括涂氏磷钙石、塞石英、玲根石、谢氏超晶石、阿考寨石等.在冲击变质陨石中发现了后尖晶石结构的超高压相,即谢氏超晶石和CF相,引起了高压地质学及大地构造学界的关注.揭示了从冲击成因二氧化硅熔体中结晶的柯石英,合理地限定了冲击变质成因柯石英的形成压力温度条件,为我国首个地外天体撞击构造——岫岩陨石坑的证实提供了关键的矿物物理证据.     

Woodleigh,Southern Carnarvon Basin,Western Australia: history of discovery,Late Devonian age,and geophysical and morphometric evidence for a 120 km-diameter impact structure

The discovery of the Woodleigh impact structure, first identified by R. P. Iasky, bears a number of parallels with that of the Chicxulub impact structure of K?–?T boundary age, underpinning complications inherent in the study of buried impact structures by geophysical techniques and drilling. Questions raised in connection with the diameter of the Woodleigh impact structure reflect uncertainties in criteria used to define original crater sizes in eroded and buried impact structures as well as limits on the geological controls at Woodleigh. The truncation of the regional Ajana?–?Wandagee gravity ridges by the outer aureole of the Woodleigh structure, a superposed arcuate magnetic anomaly along the eastern part of the structure, seismic-reflection data indicating a central >?37 km-diameter dome, correlation of fault patterns between Woodleigh and less-deeply eroded impact structures (Ries crater, Chesapeake Bay), and morphometric estimates all indicate a final diameter of 120 km. At Woodleigh, pre-hydrothermal shock-induced melting and diaplectic transformations are heavily masked by pervasive alteration of the shocked gneisses to montmorillonite-dominated clays, accounting for the high MgO and low K₂O of cryptocrystalline components. The possible contamination of sub-crater levels of the Woodleigh impact structure by meteoritic components, suggested by high Ni, Co, Cr, Ni/Co and Ni/Cr ratios, requires further siderophile element analyses of vein materials. Although stratigraphic age constraints on the impact event are broad (post-Middle Devonian to pre-Early Jurassic) high-temperature (200?–?250°C) pervasive hydrothermal activity dated by K?–?Ar isotopes of illite?–?smectite indicates an age of 359?±?4 Ma. To date neither Late Devonian crater fill, nor impact ejecta fallout units have been identified, although metallic meteoritic ablation spherules of a similar age have been found in the Canning Basin.     

Phenotypic plasticity in Bacillus cereus strains isolated from various Antarctic habitats

We studied five strains of psychrotolerant Bacillus cereus （B. cereus） isolated from Antarctic snow （BCsn）, ice （BCic）, lake water （BCwt）, sediment （BCsd）, and soil （BCsl） samples in terms of their growth, biochemical properties, and heat shock re- sponses. Analyses of growth kinetics at 4℃ showed that BCsn had the fastest generation time （16.1 h）, whereas BCWT had the slowest （30.8 h）. Strain BCsd formed the largest zone of lipid hydrolysis （18 mm） whereas BCsn formed the smallest zone （3 mm）.Only BCsd produced gelatinase. These physiological differences illustrate adaptations of B. cereus isolates to different niches. Strains BCsl and BCwr were resistant to all 12 of the antibiotics tested. Strains BCsn, BCio, and BCsd were resistant to cell wall synthesis inhibitors （penicillin and ampicillin） and susceptible to protein synthesis inhibitors （tetracycline and streptomycin）. A carbon-substrate utilization assay revealed that BCsn, BCic and BCwr could specifically utilize D-glucose-6-phosphate, salicin, and 2＇-deoxyadenosine, respectively, indicating a degree of metabolic diversity among these Antarctic B. cereus strains. An analy- sis of heat shock proteins （HSPs） produced in response to a 60℃ heat treatment revealed significant variations in the amounts of HSP33 （p = 0.01, df= 4）, HSP44 （p = 0.003, dr= 4）, and HSP60 （p = 0.04, df= 4） among the strains. This emphasizes the impor- tance of HSPs in bacterial taxonomy. These results show that there are considerable adaptive variations among B. cereus strains from extremophilie environments. This could be significant in evaluating the taxonomy and evolution of this species.