2017年9月4日河北临城M_L4.4地震震源深度测定

震源深度是地震定位中的重要参数之一。对于一个地震,sPn与Pn震相到时差是一个常量,与震中距无关,只与震源深度和地壳模型有关。基于该理论,以河北数字台网数据为基础,识别sPn震相和Pn震相,计算2017年9月4日河北临城ML4.4地震震源深度,结果为6.86km。双差定位法是目前确定震源深度比较精确的方法,双差定位得到的震源深度为7.01km。双差定位法所用数据量比较大,计算过程繁杂。利用sPn与Pn到时差计算震源深度的结果与双差定位法结果接近,计算快速、简单,所需数据量小。因此,将该方法应用到实际工作中,可以快速、准确地测定近震震源深度。     

多孔黏弹介质平面波理论及波场数值模拟

本文将黏弹固体骨架与各向异性多孔弹性模型相结合,并将地层黏弹性的特性考虑其中,更好地刻画了快P波和横波在地震频带的衰减现象。将多孔黏弹模型模拟结果同传统弹性模型模拟结果对比显示,多孔黏弹模型在模拟真实储层方面更具优势。     

地下洞室黏弹性位移反分析模式分层运算

在洞室黏弹性位移参数反分析中,对分层优化方法存在初始值选取困难、计算量大等问题进行了探讨,提出了基于最小二乘法的模式分层运算方法,改变参数求解机制,避免了由于初始值选取不当造成迭代不收敛的现象,加强了求解搜索的有效性,提高解的精度和稳定性,通过工程实例进行验证。数值计算结果表明,模式分层运算对洞室黏弹性多参数位移反分析计算的结果真实、可靠。     

罗氏沼虾线粒体锰超氧化物歧化酶的克隆表达与功能研究

罗氏沼虾(Macrobrachium rosenbergii)是我国重要的经济虾类之一。近年来, 细菌性感染造成罗氏沼虾养殖业病害频发, 经济损失巨大。因此了解其免疫机制对于指导疾病防控至关重要。线粒体锰超氧化物歧化酶(mitochondrial manganese superoxide dismutase, mMnSOD)被认为是抵御氧化应激的第一道防线, 在先天性免疫中具有至关重要的作用。目前, 甲壳动物中mMnSOD的免疫功能尚不清楚。为此, 本研究克隆了罗氏沼虾mMnSOD基因(mMnSOD of M. rosenbergii, MrmMnSOD), 制备了多克隆抗体, 分析了嗜水气单胞菌(Aeromonas hydrophila)感染下, MrmMnSOD在不同组织中的表达模式。结果显示, 肝胰腺和肠组织中MrmMnSOD的基因表达水平分别在感染后3h和6h达到最大; 组织免疫荧光分析显示, 肝胰腺和肠组织中MrmMnSOD均在感染后12h达到最大荧光强度。以上结果表明, mMnSOD参与了罗氏沼虾对嗜水气单胞菌的免疫应激反应。进一步的蛋白抑菌实验表明, MrmMnSOD可显著抑制大肠杆菌(Escherichia coli)、嗜水气单胞菌、副溶血弧菌(Vibrio parahaemolyticus)、金黄色葡萄球菌(Staphylococcus aureus)和无乳链球菌(Streptococcus agalactiae)的生长, 推测该蛋白可能属于免疫相关分子, 可通过抑菌反应发挥免疫功能。当前的研究结果进一步丰富了甲壳动物先天性免疫基础理论, 也可为今后罗氏沼虾的病害防控和药物研发提供新的靶点参考。     

南海北部主要经济鱼类体长与体重关系

文中根据1997～1999年和2001～2002年期间在南海北部底拖网调查的43种共33 389尾鱼的体长（叉长、肛长）和体重数据,应用统计分析方法对各鱼种体长与体重关系进行分析.结果表明,43种鱼分别隶属于4目16科25属,相关系数R^2的范围为0.764～0.993,相关系数R^2值相对较高,其中58%的R^2值超过0.95.幂指数b值范围为2.50～3.44,平均2.90.盒须图分析表明,50%的b值在2.79～3.01范围.经初步分析,43种主要经济鱼类中,有16种为等速生长、22种负的异速生长和5种正的异速生长.     

龙口桑岛附近海域表层沉积物分布特征

根据桑岛附近海域184个表层沉积物样品的粒度测量结果,分析了表层沉积物类型、分布特征和粒度参数变化规律,并探讨了影响沉积物分布的主要因素。结果表明,桑岛附近海域表层沉积物主要包括砂质粉砂、砂质砾、砾石等7种类型,砂质粉砂分布广泛,含砾的粗粒沉积物主要分布在桑岛周边近岸,细粒组分高值区主要在远岸地区。沉积物分选程度总体上呈中等,偏态值基本都是正值。桑岛南侧水道和依岛北侧表层沉积物起动流速小于最大潮流流速,潮流作用在此处明显;砂质海岸和桑岛北侧海岸沉积物主要受波浪作用影响。     

五圆柱体结构群绕流特性及互扰效应研究

基于Fluent流体计算平台,运用大涡模拟方法对亚临界雷诺数Re=3900下“X”形排列五圆柱体结构群三维绕流特性进行研究,主要分析来流攻角α与间距比L/D两个关键参数对五圆柱体结构群的尾流区三维涡结构演化与流体力系数的影响,并揭示其内在流动互扰机理。研究表明:来流攻角和间距比的变化对五圆柱体结构群流动控制及互扰效应的影响显著。在小间距比工况下,观察到柱体群间隙区域内流体高速流动的现象,导致五圆柱体之间的互扰作用十分强烈。间隙流对中间圆柱体和下游圆柱体有较强的冲击作用,对其表面的流体力分布特性有显著的影响。另外,大间距比工况下,当α=0°与L/D≥5.0工况时,柱体群尾流效应强于其间隙流效应。当α=22.5°与L/D=7.0时,位于下游与中间处的圆柱体流体绕流特性存在较大差异。而当α=45°与L/D≥6.0时,位于上游与中间处的圆柱体尾流区均会产生正负交替的漩涡结构。     

A new efficient 3D non-hydrostatic free-surface flow model for simulating water wave motions

A new three-dimensional, non-hydrostatic free surface flow model is presented. For simulating water wave motions over uneven bottoms, the model employs an explicit project method on a Cartesian the staggered gird system to solve the complete three-dimensional Navier–Stokes equations. A bi-conjugated gradient method with a pre-conditioning procedure is used to solve the resulting matrix system. The model is capable of resolving non-hydrostatic pressure by incorporating the integral method of the top-layer pressure treatment, and predicting wave propagation and interaction over irregular bottom by including a partial bottom-cell treatment. Four examples of surface wave propagation are used to demonstrate the capability of the model. Using a small of vertical layers (e.g. 2–3 layers), it is shown that the model could effectively and accurately resolve wave shoaling, non-linearity, dispersion, fission, refraction, and diffraction phenomena.     

Comparison of Five Numerical Codes for Automated Tracing of Coronal Loops

The three-dimensional (3D) modeling of coronal loops and filaments requires algorithms that automatically trace curvilinear features in solar EUV or soft X-ray images. We compare five existing algorithms that have been developed and customized to trace curvilinear features in solar images: i) the oriented-connectivity method (OCM), which is an extension of the Strous pixel-labeling algorithm (developed by Lee, Newman, and Gary); ii) the dynamic aperture-based loop-segmentation method (developed by Lee, Newman, and Gary); iii) unbiased detection of curvilinear structures (developed by Steger, Raghupathy, and Smith); iv) the oriented-direction method (developed by Aschwanden); and v) ridge detection by automated scaling (developed by Inhester). We test the five existing numerical codes with a TRACE image that shows a bipolar active region and contains over 100 discernable loops. We evaluate the performance of the five codes by comparing the cumulative distribution of loop lengths, the median and maximum loop length, the completeness or detection efficiency, the accuracy, and flux sensitivity. These algorithms are useful for the reconstruction of the 3D geometry of coronal loops from stereoscopic observations with the STEREO spacecraft, or for quantitative comparisons of observed EUV loop geometries with (nonlinear force-free) magnetic field extrapolation models.     

ANABRANCHING RIVERS: THEIR CAUSE,CHARACTER AND CLASSIFICATION

Anabranching rivers consist of multiple channels separated by vegetated semi-permanent alluvial islands excised from existing floodplain or formed by within-channel or deltaic accretion. These rivers occupy a wide range of environments from low to high energy, however, their existence has never been adequately explained. They occur concurrently with other types of channel pattern, although specific requirements include a flood-dominated flow regime and banks that are resistant to erosion, with some systems characterized by mechanisms to block or constrict channels, thereby triggering avulsion. The fundamental advantage of an anabranching river is that, by constructing a semi-permanent system of multiple channels, it can concentrate stream flow and maximize bed-sediment transport (work per unit area of the bed) under conditions where there is little or no opportunity to increase gradient. On the basis of stream energy, sediment size and morphological characteristics, six types of anabranching river are recognized; types 1–3 are lower energy and types 4–6 are higher energy systems. Type 1 are cohesive sediment rivers (commonly termed anastomosing) with low w/d ratio channels that exhibit little or no lateral migration. They are divisible into three subtypes based on vegetative and sedimentary environment. Type 2 are sand-dominated, island-forming rivers, and type 3 are mixed-load laterally active meandering rivers. Type 4 are sand-dominated, ridge-forming rivers characterized by long, parallel, channel-dividing ridges. Type 5 are gravel-dominated, laterally active systems that interface between meandering and braiding in mountainous regions. Type 6 are gravel-dominated, stable systems that occur as non-migrating channels in small, relatively steep basins. Anabranching rivers represent a relatively uncommon but widespread and distinctive group that, because of particular sedimentary, energy-gradient and other hydraulic conditions, operate most effectively as a system of multiple channels separated by vegetated floodplain islands or alluvial ridges.