琼东南盆地华光凹陷天然气水合物稳定带厚度的影响因素

为了探讨琼东南盆地华光凹陷海底天然气水合物稳定带的分布规律,定量研究了静水压力、底水温度、地温梯度和气源组分对水合物稳定带的影响程度。在此基础上,分析了华光凹陷现今甲烷水合物稳定带的厚度分布。最后,综合各因素的历史演化过程,初步探讨了华光凹陷1.05 Ma BP以来天然气水合物稳定带的演化。结果表明:(1)气源组分和海底温度的变化对研究区内水合物稳定带的影响较大;水合物稳定带厚度与海底温度呈良好的线性负相关性。(2)水深超过600 m的海域具备形成天然气水合物的温压条件;超过600 m水深的海域水合物稳定带厚度大部分超过 100 m,其中西北部稳定带的最大厚度超过300 m,是有利的水合物勘探区。(3)华光凹陷1.05 Ma BP以来天然气水合物稳定带厚度经历了快速增厚–窄幅变化–快速减薄和恢复的过程。麻坑群与水合物稳定变化敏感区在空间上具有较好的叠合关系。结合前人的研究成果,推测其形成与天然气水合物的分解释放有关。     

低周反复荷载下Q460钢材框架柱抗震性能分析

为了进一步完善Q460钢材在抗震设计规范中相关限值的要求,本文利用有限元软件ABAQUS,以轴压比、翼缘宽厚比、腹板高厚比和壁板宽厚比为变量,建立了共48根“工”字型框架柱和“箱”型框架柱,分析了其抗震性能。结果表明:翼缘宽厚比对框架柱的能量耗散系数影响较小;能量耗散系数随轴压比、腹板高厚比（“工”字型）和壁板宽厚比（“箱”型）增大而明显减小;框架柱的极限承载力随轴压比的减小及壁板宽厚比和翼缘宽厚比的增大而逐渐增大,当腹板高厚比接近规范限值时,承载力下降趋势明显增大。与采用Q235钢材的框架柱相比,Q460钢材框架柱的延性较小,仅为2左右;当采用Q460钢材时,“工”字型框架柱的极限位移角限值建议取为0.03,“箱”型框架柱的极限位移角限值建议取为0.032。规范中对翼缘宽厚比限值的规定偏于保守,其值最大可取至9。无论是“工”字型框架柱还是“箱”型框架柱,其腹板高厚比均不宜过大。Q460钢材框架柱的刚度退化率随轴压比的增大而增强,且翼缘宽厚比越大,腹板高厚比越小,柱的初始刚度越大,刚度退化程度越明显。     

热力强迫对台风次级环流的作用

本文利用无量纲的台风次级环流方程,用西太平洋地区11年的综合台风资料,计算了热力因子强迫的次级环流。通过计算,得到主要结论如下: 1.非绝热加热和积云热量垂直混合是主要的热力强迫因子,二者的作用具有同样量级。 2.热量的湍流涡旋通量及积云的热量水平输送作用都比较小。 3.Ekman抽吸与积云热量垂直混合是相互促进,共同发展的。有利于次级环流的增强。     

An Improved Approach for Parameterizing Surface-Layer Turbulent Transfer Coefficients in Numerical Models

Based on classic iterative computation results, new equations to calculate the surface turbulent transfer coefficients are proposed, which allow for large ratios of the momentum and heat roughness lengths. Compared to the Launiainen scheme, our proposed scheme generates results closer to classical iterative computations. Under unstable stratification, the relative error in the Launiainen scheme increases linearly with increasing instability, even exceeding 15%, while the relative error of the present scheme is always less than 8.5%. Under stable stratification, the Launiainen scheme uses two equations, one for 0 < Ri _B ≤ 0.08 and another for 0.08 < Ri _B ≤ 0.2, and does not consider the condition that Ri _B > 0.2, while its relative errors in the region 0 < Ri _B ≤ 0.2 exceed 31 and 24% for momentum and heat transfer coefficients, respectively. In contrast, the present scheme uses only one equation for 0 < Ri _B ≤ 0.2 and another equation for Ri _B > 0.2, and the relative error of the present scheme is always less than 14%.     

Observational estimation of heat budgets on drifting ice and open water over the Arctic Ocean

It is of major scientific interests to determine the parameters of momentum, heat and vapor exchange in the planetary boundary layer in order to study the effects of ocean-ice-atmosphere interactions and their feedback mechanisms on global climate[1]. Lin…     

快速射电暴的数据统计

快速射电暴于2007年首次在脉冲星巡天的历史数据中被发现,是一种在射电波段观测到的具有色散量的单个强脉冲,其特征为持续时间仅为若干毫秒,峰值流量密度可达到央斯基量级。类似于射电脉冲星的单个脉冲,但其色散显著超过同一视线方向上银河系内星际介质的预期最大值。对截止2018年6月帕克斯望远镜、绿岸望远镜、阿雷西博射电望远镜、UTMOST望远镜和ASKAP望远镜已探测到的52例快速射电暴进行了观测量统计分析,根据模型扣除银河系星际介质导致的色散量后,快速射电暴平均色散量为584.5 pc·cm^-3,暗示着快速射电暴来自河外。通过最佳拟合估算红移幂律分布谱dN/dF_obs=4.14±1.30×F■sky^-1·day^-1。根据分析结果预计,FAST望远镜使用19波束接收机后,其多科学目标同时巡天在经过一年时间内能发现大约10个快速射电暴,将有效地扩大样本数量,为快速射电暴研究提供重要信息。     

Late Quaternary clay minerals off Middle Vietnam in the western South China Sea: Implications for source analysis and East Asian monsoon evolution

High-resolution clay mineral records combined with oxygen isotopic stratigraphy over the past 450 ka during late Quaternary from Core MD05-2901 off Middle Vietnam in the western South China Sea are re-ported to reconstruct a history of East Asian monsoon evolution. Variations in Illite, chlorite, and kaolinite contents indicate a strong glacial-interglacial cyclicity, while changes in smectite content present a higher frequency cyclicity. The provenance analysis indicates a mixture of individual clay minerals from various sources surrounding the South China Sea. Smectite derived mainly from the Sunda shelf and its major source area of the Indonesian islands. Illite and chlorite originated mainly from the Mekong and Red rivers. Kaolinite was provided mainly by the Pearl River. Spectral analysis of the kaolin-ite/(illite chlorite) ratio displays a strong eccentricity period of 100 ka, implying the ice sheet-forced win-ter monsoon evolution; whereas higher frequency changes in the smectite content show an ice sheet-forced obliquity period of 41 ka, and precession periods of 23 and 19 ka and a semi-precession period of 13 ka as well, implying the tropical-forced summer monsoon evolution. The winter monsoon evolution is generally in coherence with the glacial-interglacial cyclicity, with intensified winter monsoon winds during glacials and weakened winter monsoon winds during interglacials; whereas the summer monsoon evolution provides an almost linear response to the summer insolation of low latitude in the Northern Hemisphere, with strengthened summer monsoon during higher insolation and weakened summer monsoon during lower insolation. The result suggests that the high-latitude ice sheet and low-latitude tropical factor could drive the late Quaternary evolution of East Asian winter and summer monsoons, respectively, implying their diplex and self-contained forcing mechanism.     

淮南煤田朱集井田岩浆侵入特征研究

在对淮南煤田朱集井田钻孔资料分析的基础上,结合侵入岩化学成分测试、X-射线衍射分析以及薄片显微镜下鉴定等结果,得出研究区侵入岩主要以岩床的形式侵入煤系地层,岩性以闪长岩、花岗岩为主,岩床层数多为单层;受NWW—NW向断裂构造带控制,侵入岩体的分布范围呈现从西向东逐渐扩大,在垂向上,从上部煤层到下部煤层,受岩浆影响的程度有明显加大的态势。由于岩浆侵入煤层,严重破坏了煤层的结构和稳定性,同时,降低了煤的工业利用价值,加大了开采难度。     

Models of rapidly rotating neutron stars: remnants of accretion-induced collapse

Equilibrium models of differentially rotating nascent neutron stars are constructed, which represent the result of the accretion-induced collapse of rapidly rotating white dwarfs. The models are built in a two-step procedure: (1) a rapidly rotating pre-collapse white dwarf model is constructed; (2) a stationary axisymmetric neutron star having the same total mass and angular momentum distribution as the white dwarf is constructed. The resulting collapsed objects consist of a high-density central core of size roughly 20 km, surrounded by a massive accretion torus extending over 1000 km from the rotation axis. The ratio of the rotational kinetic energy to the gravitational potential energy of these neutron stars ranges from 0.13 to 0.26, suggesting that some of these objects may have a non-axisymmetric dynamical instability that could emit a significant amount of gravitational radiation.     

气候序列的层次结构

一个气候时间序列含有多个时间尺度 ,形成不同尺度的气候层次。气候是冷还是暖是随着尺度而变化的。文中用北半球地表月平均气温气候资料的子波变换分析表明 :气候突变点既随尺度有规律的变化 ,也具有随尺度变化而不变的性质 ,即标度不变性。不论什么尺度 ,气候总是有冷暖之分 ,这种自相似性可以帮助笔者从气候资料的子波变换中建立一个一维映射动力系统 ,它反映出气候突变时间的演变规律和气候的层次结构。