Short term variability of Particle fluxes and its relation to variability in sea surface temperature and chlorophylla field detected by Ocean Color and Temperature Scanner (OCTS) off Sanriku, northwestern North Pacific in the spring of 1997

A sediment trap experiment was carried out in conjunction with an over flight of Ocean Color Temperature Scanner (OCTS) on board Advanced Earth Observing Satellite (ADEOS) at 40°N, 143°E off Sanriku in April to May 1997. Short term variability of particle fluxes was examined at depths of 450 m and 600 m from April 6 to May 1 with a sampling interval of two days, and at 450 m with one day interval from 2nd to 10th May. Daily averaged mass flux at 450 m and 600 m was 815 mg m⁻²d⁻¹ and 862 mg m⁻²d⁻¹, respectively. A sharp increase in mass flux was observed during the period from April 26 to April 29 with the highest mass flux of 8 g m⁻²d⁻¹. About 85% of the total mass flux for the entire duration (26 days) was collected within these 4 days. Trapped material during the peak flux period was mainly composed of diatoms dominated byThalassiosira spp. and resting spores ofChaetoceros spp. This suggested that the peak flux was the result of (a) diatom bloom(s) in the euphotic column. Current meter records at 420 m showed that on April 26 and 27, the period when the peak flux was observed, the southwestward current had diminished in strength and changed its direction northwestward. Low current speeds appeared to have enhanced trap efficiency to help form the peak flux. A time series of OCTS Intensive-LAC (Local Area Coverage: Region B) images from mid-March to early May was examined todetect phytoplankton bloom(s). In the March 26th Chl image, high concentration region was restricted to the southwest off Cape Erimo, but spread around the warm core ring (WCR) 93A by April 10. East of the WCR93A, high Chl concentration remained steady until May, but to the west of the WCR93A, Chl decreased rapidly before the 19th of April. From this observation we suspect that the peak flux observed at the end of April originated from a bloom, which ceased on the 17th or 18th of April, in the region north of 40°N and west of 143°E. Taking the current meter records into account, the source region for the trapped material is most likely around southwest of the Cape Erimo.     

The effects of in-cloud mass production on atmospheric light scatter

Direct physical measurements of particle mass and number concentration indicate an increase in overall aerosol mass resulting from cloud processing, most likely through aqueous-phase chemistry (e.g., SO₂ oxidation). Measurements conducted in the Pennines of Northern England reveal an average increase of 14 to 20% in dry aerosol mass (0.003<particle diameter<0.9 μm) after aerosol passage through an orographic cloud. The rate of in-cloud mass production is most sensitive to changes in upwind particle size distributions, SO₂ concentration, and cloud water acidity. Newly-formed mass appears in size range between 200 and 600 nm and enhances the bimodality of the particle number distribution after cloud processing. Furthermore, the cloud-produced mass is estimated to increase total light scattering, b_sp, by 18 to 24%. The scattering efficiency of the dry, cloud-generated aerosol is 5.0±0.3 m² g⁻¹ and increases to 7.4±0.7 m² g⁻¹ when adjusted to 90% relative humidity by incorporating particle hygroscopicity data.     

Turbulent structure in uniform inclined open channel flow over different rough porous beds

In this study the effects of the different rough porous beds in an open inclined channel are studied experimentally for impermeable and permeable porous bed.For the simulation of porous bed two different types of permeable bed with the same thickness(s' = 3 cm) and the same porosity ε=0.70 are used:(a) porous filters and(b) gravel bed.Laboratory experiments were used for the calculation of turbulent velocity profiles.Measurements of velocity were taken for inclined channel for three different slopes(S=-0.002,S=-0.004 and S=-0.006) and for five different flow depths(h=5 cm,7 cm,9 cm,11 cm and 13 cm).The total discharge Q varies from 0.78 to 1.31 1/s.The measurements were obtained using a two-dimensional(2D) Particle Image Velocimetry(PIV).The total discharge was estimated using a calibrated venture apparatus.Results showed that the presence of rough porous bed in inclined open channels influence significantly the turbulent characteristics of the flow in comparison with impermeable open channels with the same slopes.     

基于萤火虫和蝙蝠群智能算法的瑞雷波频散曲线反演

反演瑞雷波频散曲线能有效获取地层横波速度和厚度.但由于其高度的非线性、多参数、多极值等特点,传统的全局搜索方法易出现收敛速度慢、早熟收敛及搜索精度低的问题.鉴于此,本文提出并测试了基于萤火虫优化算法（FA）和带惯性权重的蝙蝠优化算法（WBA）的新的瑞雷波频散曲线反演策略.在瑞雷波频散曲线反演中,FA全局搜索能力强,但后期搜索精度低,而WBA局部搜索能力强,搜索精度高,但易出现早熟收敛.故本文将二者结合,提出了一种新的优化策略,称其为WFBA,即在反演前期使用FA,后期使用WBA,很好地解决了FA后期搜索精度低及WBA早熟收敛的问题.本文首先反演了三个典型理论模型的无噪声、含噪声的数据,验证了WFBA对瑞雷波数据反演的有效性与稳定性.然后将WFBA与WBA、FA单独反演以及不含惯性权重的FBA和粒子群优化算法（PSO）反演的结果进行了对比,说明了WFBA相对于WBA、FA、FBA和PSO具有更稳定、收敛速度更快、求解精度更高等优点.最后,反演了来自美国怀俄明地区的实测资料,检验了WFBA对瑞雷波数据反演的实用性.理论模型试算和实测资料分析表明,WFBA很适用于瑞雷波频散曲线的定量解释,具有很高的实用性价值.     

基于贝叶斯框架的各向异性页岩储层岩石物理反演技术

页岩岩石物理建模旨在建立页岩矿物组分、微观结构、流体填充与岩石弹性参数的关系.对四川盆地龙马溪组页岩进行岩石物理建模研究,针对页岩黏土含量高、层间微裂缝发育等特点,利用Backus平均理论描述页岩黏土矿物弹性参数,利用Chapman理论计算与水平微裂缝有关的VTI各向异性,并利用Bond变换考虑地层倾角的影响.提出以黏土矿物纵、横波速度和孔隙纵横比为拟合参数进行岩石物理反演的方法,并引入贝叶斯框架减小反演的多解性.由已知的黏土矿物纵、横波速度和孔隙纵横比作为先验信息,并以测井纵、横波速度作为约束条件建立反演的目标函数,同时利用粒子群算法进行最优化搜索.计算结果表明,基于先验约束和粒子群算法的反演方法能够较准确地反演黏土矿物的弹性参数、孔隙形态参数以及裂缝密度等参数.计算得到的黏土纵、横波速度较高,并且在一定范围内变化,这可能与龙马溪组页岩的黏土矿物组分中具有较高弹性模量的伊利石含量较高有关,同时也与黏土定向排列等微观物性特征有关.反演得到的裂缝密度与纵波各向异性参数ε呈明显的正相关,而与横波各向异性参数γ相关性较小.另外,页岩各向异性参数与黏土垂向的纵横波速度有较强的相关性.     

基于粒子群算法的浮筒配置优化问题的研究

针对传统的验证法在解决浮筒配置问题中存在的计算量大、计算时间长、工作重复性强等缺点,提出了一种将浮筒纵向位置配置和浮筒充气量综合考虑、一体优化的方法。文章将各种合理性校验准则作为约束条件,通过逼近沉艇起浮瞬间和浮起后的平衡状态,来求取各对浮筒的纵向位置和充气量,将浮筒配置问题转换为一个多目标、多约束的最优化问题。在此基础上,根据粒子群优化算法的特点,提出了一种双向搜索策略,来求解浮筒配置优化问题。这种方法简单实用,计算时间短,无需人工干预,算法运行一次可获得多组配置方案供决策人员选择。算例表明用这种方法来解决浮筒配置问题是可行的、有效的。     

Granite is an Effective Helium Source Rock: Insights from the Helium Generation and Release Characteristics in Granites from the North Qinling Orogen,China

Global helium(He) shortage is a challenging problem; however, the types of helium source rock and the mechanisms of He generation and release therein remain still poorly understood. In this study, in order to evaluate the potential of granite as an effective helium source rock, we collected granitic samples from the North Qinling Orogen, Central China, in the south of the helium-rich Weihe Basin. The helium generation and release behaviors in granite were studied through analysis of U and Th concentrations, EMPA images, and He and Ar concentrations and isotopic ratios extracted by crushing and stepwise heating. The results indicate that Ar has a better retention and a lower mobility than He. 3 He/4 He ratios released by crushing and stepwise heating are 0.016–0.056 RA and 0.003–0.572 RA, respectively, where RA is the atmospheric 3 He/4 He of 1.4×10-6, reflecting a crustal and radiogenic source. Helium concentrations extracted by the two ways are 0.13–0.95 ucm3 STP/g and 7.82–115.62 ucm3 STP/g, respectively, suggesting that matrix-sited He accounts for more than 98% of total helium preserved in granite. In addition, the total generated He amounts in granites are calculated based on the measured U and Th concentrations in granitic samples. Dividing the preserved He quantities by the generated He amounts, it turned out that less than 10% of He produced since the formation of the granite is preserved in the rock over geological time, suggesting that more than 90% generated He can be transferred to the Weihe Basin. Temperature and fracture are the two critical factors controlling He release. Based on the relationship between He diffusivity of granites and temperature and the He closure temperatures of a variety of U-and Th-rich minerals(27–250°C), we estimate that He can be partially released out of granite at the depths 400 m and totally released at the depths 7800 m. Fractures provide effective transfer of free He from deep source rocks to shallow reservoirs. Finally, a model on granite as an effective helium source rock is established. We suggest exploring He resources in hydrocarbon basins with granitic basement(or adjacent to granite bodies), high geothermal field, and young active fractures.     

基于PSO-BP神经网络的地表下沉系数选取研究

针对BP神经网络自身收敛速度慢、容易陷入局部极小点的缺点,引入粒子群优化算法,建立地表下沉系数的PSO-BP选取模型。利用粒子群算法反复优化BP网络的权值和阈值,将其作为BP网络的初始值,并将上覆岩层岩性、开采深厚比、松散层厚度、覆岩中坚硬岩层所占比例、是否为重复采动和顶板管理方法等主要影响因素作为网络输入,进行BP算法,直至网络达到训练指标。利用实测资料数据,建立PSO-BP预计模型,并同普通BP神经网络预计结果对比。结果表明：PSO-BP神经网络不仅训练速度快,而且预测精度明显提高,该模型对地表下沉系数选取具有一定的应用价值。     

珊瑚颗粒形状对钙质粗粒土的压缩性能影响

珊瑚颗粒形状不规则是其显著区别于陆源土的一大特征。为揭示珊瑚颗粒形状对钙质粗粒土压缩性能的影响,人工挑选出不同形状(块状、枝状、棒状、片状)的珊瑚颗粒,以块状颗粒为基础,与其他3种不同形状的粗颗粒任意一种混合,控制不同颗粒形状配比制成钙质粗粒土试样,完成室内压缩试验,对比分析试验前后珊瑚颗粒的圆度、长宽比、扁平度和凹凸度等形状参数,评价颗粒形状对压缩性能的影响。结果表明:(1)粒径为10~20 mm钙质粗粒土的压缩模量是4~5. 5 MPa,回弹系数为42~53;(2)随枝状、棒状或片状颗粒掺量的增加(0、10%、20%、30%),试样压缩模量呈小幅波状变化,回弹系数呈持续减小趋势;(3)各加载区间应力-应变曲线包括应力快速增长阶段、应力-应变同步增长阶段、应变增长阶段共3个阶段和1个稳定点;(4)随枝状颗粒掺量的增加,试样的长宽比和凹凸度逐渐增加,圆度和扁平度基本无变化;因颗粒破碎的影响,试验后试样的长宽比及扁平度有所增加,圆度及凹凸度则有所减小。选择钙质粗粒土地基时,应考虑其压缩性能,避免施工初期的快速加载。