北部湾地区不同相对密度的海砂力学特性分析

为探究相对密度和有效围压对饱和海砂力学特性的影响,利用GDS动态三轴试验仪,对广西北部湾地区海砂开展了一系列固结排水三轴剪切试验,分析了相对密度、有效围压对饱和海砂强度特征、体变特征、割线模量以及摩擦角的影响规律。结果表明：随着围压的减小或相对密度的增大,试样体积应变不断增大,而相对密度或有效围压的增加均会提高试样的峰值强度,有效围压与峰值强度之间呈现良好的线性增长关系。随着围压的减小或相对密度的增大,应力相对软化系数、剪胀系数均不断增大,且有效围压与应力相对软化系数、剪胀系数分别呈线性和半对数线性相关。割线模量随轴向应变的增加整体呈衰减趋势,各试验工况下轴向应变为5%时试样的割线模量相比于轴向应变0.164%衰减了80%~90%。饱和海砂的峰值摩擦角随相对密度的增加而增大,随有效围压的增大而减小,相对密度D_r为50%时有效围压σ_c为50 kPa对应的峰值摩擦角是σ_c为200 kPa的1.098倍。     

油藻混合水体遥感反射比光谱分析

辐射传输模式HydroLight是研究水体辐射传输特性的有效工具,同时也是进行石油类水体辐射传输特性的有效模型。本文基于2018年8月在辽宁大连港海域实测的石油类污染水体的表观及固有光学量数据,通过设置不同浓度的配比模拟试验,利用HydroLight对油类物质和藻类物质的单一组分和两者混合水体的遥感反射比（remote sensing reflectance,R_rs）光谱进行了模拟。模拟结果表明：（1）在仅含油类物质单一组分的水体中,R_rs随着油浓度C_oil的变化分为两个特征波段：400~480 nm和480~700 nm。在400~480 nm波段范围内R_rs随C_oil的增加而减小,在480~700 nm随C_oil的增大而增大;（2）在仅含藻类物质的单一成分水体中,叶绿素的光谱特性需要其浓度C_chl达到一定值才能表现出来,在低C_chl时的R_rs光谱特性反映为纯水的光谱特性;（3）在油藻混合水体中,随C_oil的增加会增大叶绿素的R_rs,但不会明显改变叶绿素的R_rs随波长的变化趋势,这说明油藻混合水体的光谱形状主要受叶绿素的影响,油类物质的存在只改变光谱的量值。利用HydroLight对石油类污染水体的R_rs展开研究,有助于丰富水色遥感基础研究,对完善各类水体生物光学模型研究具有重要的理论意义。     

砂土地基中箱筒型防波堤基础稳定性试验研究与机理分析

箱筒型防波堤基础是一种能够适应复杂海况的新型基础形式。利用室内模型试验对箱筒型防波堤基础在水平静载荷及水平循环荷载作用下的稳定特性进行了研究。结果表明：砂性土地基中箱筒型防波堤基础破坏可分为准弹性、塑性及破坏三个阶段,以荷载位移曲线出现明显拐点判断箱筒型防波堤基础极限承载力约为0.08 kN。以循环过程中施加荷载与静载荷水平极限承载力比值定义荷载循环比ζ_b,当ζ_b=0.5、ζ_b=1.0时,防波堤基础前10次累计位移最为明显,分别占总循环累计位移的96.70%、91.88%,这主要是由于砂土发生剪胀,土颗粒重新排列所致;而后40次循环累计位移不明显,分别占总循环累计位移的3.30%、8.12%,此时土体发生剪缩,土颗粒之间致密化。当ζ_b=0.5时,循环结束后防波堤基础抗滑移系数K₁、抗倾覆系数K₂分别为1.619、3.372;当ζ_b=1.0时,抗滑移系数K₁、抗倾覆系数K₂分别为0.839、-18.063,说明ζ_b=0.5循环荷载作用下砂性土地基防波堤基础稳定性良好,但ζ_b=1.0循环加载时,基础首先发生滑移破坏进而发生严重的倾覆破坏。     

开孔双壁圆形钢吊箱围堰消波效果影响因素分析

跨海大桥桥墩基础施工若采用双壁钢围堰,则在其外壁进行开孔可有效减小波浪力,有利于降低钢围堰的制作造价和提高基础施工的安全性。以某跨海大桥基础施工采用的双壁圆形钢吊箱围堰为研究对象,引入波浪力折减系数K_d对消波效果进行评价,采用数值方法着重分析波浪参数和围堰自身结构设计参数对消波效果的影响规律。结果表明:K_d随波陡增大呈先快后缓的增大趋势,波陡超过0.032后,消波效果基本不再变化;随着相对水深的增大,K_d呈先减小后增大并趋缓的规律,在相对水深d/L约为0.455时取得最小值;K_d随开孔率的增大呈线性减小,开孔率越大,消波效果越好。随着双壁间距s的增大,K_d总体上呈减小趋势,且减小速率先快后慢;双壁间距较小时,开孔的消波作用较弱。开孔率和双壁间距两种因素间存在耦合作用,两者越大,其耦合作用也越强。围堰设计中可适当增大开孔率并选取合适的双壁间距以得到最佳消波效果。     

铵锌镉还原法测试硝酸盐氮、氧同位素方法研究

本研究利用铵锌镉还原法将海水、湖水和自来水水体中硝酸盐转化为N₂O气体测试氮、氧同位素, 结果表明当反应体系的pH值在6～8之间, NO₃^-还原为NO₂^-的转化率大于95%, NO₂^-还原为N₂O的转化率大于99%。配置5种丰度的硝酸盐氮、氧同位素标样, 将实验结果与理论值绘制校准曲线, 氮同位素校准曲线斜率为0.48, 相关性良好(R²=0.999 8), 5种丰度δ¹⁵N_N2O标准偏差在0.18‰～0.43‰之间(n=5);氧同位素校准曲线斜率为0.70, 相关性良好(R²=0.999 6), 5种丰度δ¹⁸O_N2O标准偏差在0.27‰～0.46‰之间(n=5)。铵锌镉还原法与镉柱还原法测定硝酸盐氮、氧同位素结果的精密度和准确度一致, 同时海水、湖水和自来水3种不同类型水样的硝酸盐氮、氧同位素测试数据满足实验要求, 而且在实验流程的简洁性和高效性方面更具优势。     

随机波浪中畸形波在三维岛礁地形上的试验研究

在试验水池中,开展了波浪在岛礁地形上演化问题的研究。首先在实验水池中建立了西太平洋某岛礁地形的模型,然后采用改进的JONSWAP谱,由造波机产生不同周期、波高的随机波浪。试验中观察到了不同类型畸形波生成的过程及不同波面形态的畸形波。对偏度、峰度及水深与畸形波要素H_m/H_s（H_m表示波列中的最大波高, H_s为有效波高）的关系进行了详细的分析,同时,对畸形波波高H_fr与偏度的关也进行了分析。通过对试验结果分析,发现峰度与畸形波要素i>H_m/H_s呈正相关, H_fr增大时相应的偏度也会呈现增大的趋势。此外,水深的变化剧烈时（如斜坡、海山位置）有助于畸形波的发生。     

Wave Interactions with Multiple Semi-Immersed Jarlan-Type Perforated Breakwaters

This study examines wave interactions with multiple semi-immersed Jarlan-type perforated breakwaters. A numerical model based on linear wave theory and an eigenfunction expansion method has been developed to study the hydrodynamic characteristics of breakwaters. The numerical results show a good agreement with previous analytical results and experimental data for limiting cases of double partially immersed impermeable walls and double and triple Jarlan-type breakwaters. The wave transmission coefficient C_T; reflection coefficient C_R, and energy dissipation coefficient C_E coefficients and the horizontal wave force exerted on the front and rear walls are examined. The results show that C_R reaches the maximum value when B/L = 0.46n while it is smallest when B/L=0.46n+0.24 (n=0, 1, 2,...). An economical triple semi-immersed Jarlan-type perforated breakwater can be designed with B/L = 0.25 and C_R and C_T ranging from 0.25 to 0.32 by choosing a relative draft d/h of 0.35 and a permeability parameter of the perforated front walls being 0.5 for an incident wave number kh nearly equal to 2.0. The triple semi-immersed Jarlan-type perforated breakwaters with significantly reduced C_R, will enhance the structure’s wave absorption ability, and lead to smaller wave forces compared with the double one. The proposed model may be used to predict the response of a structure in the preliminary design stage for practical engineering.     

纳米复合永磁材料中软磁性相交换硬化的研究

本文就纳米复合永磁材料中软磁相被交换硬化问题,从一维模型和三维模拟计算进行了分析研究. 一维和三维各向异性样品研究表明,在相同微结构下,当硬磁相的各向异性降低时,除矫顽力降低外,在磁矩全部反转之前退磁曲线是一样的. 因此,硬磁相各向异性的降低不会导致最大磁能积(BH)_max增大和剩磁增加. 对于三维各向同性样品的模拟计算表明,降低硬磁相的各向异性会使剩磁和(BH)_max都明显降低. 因此,增强硬磁相的各向异性并增大硬磁相晶粒尺寸是提高     

珠江口溶解有机物的遥感动态监测

河口有色溶解有机物（colored dissolved organic matter,CDOM）的分布是各种物理-生物地球化学过程共同作用的结果。为实现河口高动态变化CDOM的监测,遥感是一种重要的手段。由珠江口四个不同季节的航次获得的实测数据,本文构建了一个遥感算法以反演CDOM在400 nm的吸收系数（a_CDOM （400））。该算法使用以波段反射率比值R_rs （667）/R_rs （443）和R_rs （748）/R_rs （412）为自变量。将构建的算法应用于2002-2014年的MODIS/Aqua数据,本文计算了珠江口不同季节的a_CDOM （400）气候态分布。CDOM的分布主要受珠江径流量和区域水下地形特征的影响。沿着垂直于水深梯度的断面,气候态a_CDOM （400）呈指数减少（y=ae^bx,b<0）,但不同季节差异很大。珠江口CDOM主要是河流淡水输运而来。其中,富里酸比例随盐度的增加而降低。基于构建的算法、CDOM保守混合方程和径流量,本文由MODIS/Aqua数据进一步估算了2002-2014年夏季和冬季珠江DOC的有效入海浓度和有效入海通量。珠江的有效入海浓度和有效入海通量都与流量存在正相关关系,且在夏季的相关性更明显,R2分别为0.698和0.9657。     

长江口湍流剖面的观测与分析

小尺度湍流过程对河口物质输运与能量交换至关重要。受传统观测方法的限制, 河口浅水区域的剖面观测资料至今较为匮乏, 进而限制了湍流过程的研究。为此, 采用新型5波束声学多普勒流速剖面仪(Nortek Signature 1 000 kHz AD2CP)在长江口开展湍流剖面观测, 获取高频、低噪的高质量湍流剖面数据, 并与声学多普勒点式流速仪(acoustic doppler velocimeters, ADV)同步观测的数据进行对比。结果表明, 通过AD2CP与ADV获得的近底部边界层摩阻流速u_*、拖曳系数C_d、雷诺应力S_R等特征参数基本一致, 底摩擦与波浪能量为河口区域湍动能的主要输入源。湍流垂向结构存在显著的非局地平衡, 即温盐等斜压作用引起的浮力通量、对流项以及强波浪作用影响的脉动压力做功、黏性输运等因素可能为长江口湍流非局地平衡的主因。     

三峡及邻区晚第三纪以来构造应力场特征探讨

用三峡及邻区（东经１０８°～１１３°，北纬２９°～３３°）地质资料，地震资料，现 场地应力测量资料论证三峡及邻区晚第三纪以来构造应力场稳定性及其分区特 征。     

Anisotropic Drained Deformation Behavior and Shear Strength of Natural Soft Marine Clay

The deformation behavior and shear strength of soft marine clays subjected to wave or traffic loads are different from that in triaxial loading due to the changes of major principal stress direction β and intermediate principal stress coefficient b. To investigate the anisotropy affected by β and b in natural soft marine clay, a series of drained tests were conducted by hollow cylinder apparatus. The principal stress direction relative to vertical direction were maintained constant under an increasing shear stress, with fixed intermediate principal stress coefficient b. The influence of the b and β on anisotropy of typically Wenzhou intact clay is discussed. It was found that octahedral stress–strain relationships expressed anisotropy with different b and β. The friction angle and deviator stress ratio with different b and β were presented to provide guidance for engineering projects in the coastal zone.     

Present-day stress and pore pressure fields in the Cuu Long and Nam Con Son Basins, offshore Vietnam

Knowledge of the in situ, or contemporary stress field is vital for planning optimum orientations of deviated and horizontal wells, reservoir characterization and a better understanding of geodynamic processes and their effects on basin evolution.This study provides the first documented analysis of in situ stress and pore pressure fields in the sedimentary formations of the Cuu Long and Nam Con Son Basins, offshore Vietnam, based on data from petroleum exploration and production wells.In the Cuu Long Basin, the maximum horizontal stress is mainly oriented in NNW–SSE to N–S in the northern part and central high. In the Nam Con Son Basin, the maximum horizontal stress is mainly oriented in NE–SW in the northern part and to N–S in the central part of the basin.The magnitude of the vertical stress has a gradient of approximately 22.2 MPa/km at 3500 m depth. Minimum horizontal stress magnitude is approximately 61% of the vertical stress magnitude in normally pressured sequences.The effect of pore pressure change on horizontal stress magnitudes was estimated from pore pressure and fracture tests data in depleted zone caused by fluid production, and an average pore pressure–stress coupling ratio (ΔS_h/ΔP_p) obtained was 0.66. The minimum horizontal stress magnitude approaches the vertical stress magnitude in overpressured zones of the Nam Con Son Basin, suggesting that an isotropic or strike-slip faulting stress regime may exist in the deeper overpressured sequences.     

海浪对海洋上层的动量与混合作用分析

分析了波浪影响海洋环流的3种机制，给出了波浪对海流的雷诺应力表示、搅拌混合系数表示以及对温盐扩散的搅拌混合系数表示；计算了东中国海区域的波浪动量作用、搅拌混合系数空间分布和时间演化，进而定量分析了波浪对表层海流的动量输送及对海洋上混合层与跃层形成的作用。     

Dynamic stress analysis of the leg joints of self-elevating platform

Since a self-elevating platform often works in water for a long time,the lattice leg is largely influenced by wave and current.The amplitude of leg joint stresses is a very important factor for the fatigue life of the platform.However,there are not many researches having been done on the mechanism and dynamic stress analysis of these leg joints.This paper focuses on the dynamic stress analysis and suppression methods of the leg joints of self-elevating platforms.Firstly,the dynamic stresses of the lattice leg joints are analyzed for a self-elevating platform by use of the 5th-order Stokes wave theory.Secondly,the axial and bending stresses are studied due to their large contributions to total stresses.And then,different joint types are considered and the leg-hull interface stiffness is analyzed for the improvement of the joint dynamic stress amplitude.Finally,some useful conclusions are drawn for the optimization design of the self-elevating platform.     

钛合金载人舱球壳试验压力和应力衡准取值研究

各国潜水器规范对潜水器载人舱球壳试验压力的规定各有不同,以球壳的中面膜应力作为计算对象,推算各规范和标准关于膜应力在试验压力下的应力衡准。结合"蛟龙号"和"深海勇士号"两型潜水器载人舱球壳的外压试验,对计算应力和实测应力数据分析对比,提出适合钛合金载人舱球壳的试验压力和应力衡准参考值。     

An individual-component approximation to quadratic stress for flow-decomposition analysis

An individual-component approximation (ICA) to the one-dimensional quadratic stress is presented for analysis of hydrodynamic systems that contain multiple-frequency fluid motion such as tidal current and nearshore currents. Criteria governing development of the approximation are accuracy, symmetry, and preservation of contributions (magnitude and direction) of individual and coupled velocity components. Preservation of directionality is required to isolate functioning of individual terms for flow-decomposition analysis. The ICA is compared with the small-amplitude approximation analytically and through numerical examination for two velocity components. The two approximations differ at second order within the range of validity of the small-amplitude approximation. The ICA is exact in the limits of components with large magnitudes and components of equal magnitudes. Based on calculations comparing the exact numerical solution for velocity components with a wide range of relative magnitudes, relative periods, and phase differences, the ICA is accurate except in restricted regions of small-magnitude quadratic velocity. The ICA is generalized to multiple components without restriction on magnitude, period, or phase, and example calculations are given for flows comprised of three components and six components. The method is applied to velocity tidal constituents for Galveston Bay, Texas, and Tampa Bay, Florida.     

南半球亚极地流涡的平均特征及其变化

Based on the Simple Ocean Data Assimilation(SODA) products,we study the mean properties and variations of the Southern Hemisphere subpolar gyres(SHSGs) in this paper.The results show that the gyre strengths in the SODA estimates are(55.9±9.8)×10~6m~3/s for the Weddell Gyre(WG),(37.0±6.4) ×10~6m~3/s for the Ross Gyre(RG),and(27.5±8.2)×10~6m~3/s for the Australian-Antarctic Gyre(AG),respectively.There exists distinct connectivity between the adjacent gyres and then forms an oceanic super gyre structure in the southern subpolar oceans.And the interior exchanges are about(8.0±3.2)×10~6m~3/s at around 70°E and(4.3±3.1)×10~6m~3/s at around 140°E.The most pronounced variation for all three SHSGs occurs on the seasonal time scale,with generally stronger(weaker)SHSGs during austral winter(summer).And the seasonal changes of the gyre structures show that the eastern boundary of the WG and AG extends considerably further east during winter and the interior exchange in the super gyre structure increases accordingly.The WG and RG also show significant semi-annual changes.The correlation analyses confirm that the variations of the gyre strengths are strongly correlated with the changes in the local wind forcing on the semi-annual and seasonal time scales.     

坛紫菜超氧化物歧化酶基因的克隆及表达分析

超氧化物歧化酶(SOD)是植物细胞应对氧化胁迫的第一道,也是最重要的防线。本研究以坛紫菜转录组数据库中的unigene序列为基础,通过RACE扩增技术克隆得到了3条坛紫菜SOD基因的全长序列,分别命名为PhMSD,PhCSD1和PhCSD2。序列分析结果表明,PhMSD序列全长973 bp,可编码包含224个氨基酸,等电点为5.75的多肽序列;PhCSD1序列全长1029 bp,可编码包含134个氨基酸,等电点为4.65的多肽序列;PhCSD2序列全长954 bp,可编码包含216个氨基酸,等电点为10.74的多肽序列。根据保守序列和系统进化树分析,可以将三条PhSODs分成两个亚型:其中PhMSD属于锰超氧化物歧化酶,PhCSD1和PhCSD2属于铜锌超氧化物歧化酶。采用实时荧光定量PCR技术(qPCR)测定了3条PhSOD基因在坛紫菜不同世代,高温胁迫不同时间水平以及不同失水胁迫梯度下的表达水平变化,结果表明:3条PhSOD基因在叶状体世代中的表达水平均显著高于丝状体世代;在不同水平的高温和失水胁迫下,PhCSD1和PhCSD2的表达水平显著上调,而PhMSD则表现出不同的表达模式,高温胁迫下被显著抑制,失水胁迫下没有发生显著变化。     

振动时效技术在自升式风电安装平台固桩架上的应用

振动时效技术是一种有效消除焊接残余应力、提升构件使用寿命、保证结构尺寸精度的方法。在自升式平台固桩架建造过程中,焊接施工导致其内部产生大量的残余应力,残余应力是导致固桩架精度超差和损伤失效的重要原因之一,它会大幅度降低平台的疲劳寿命,因此,固桩架建造完成后消除其内部残余应力对于平台的使用安全至关重要。本文以一个质量约100 t的固桩架分段为研究对象,采用专门的振动时效设备对固桩架施加激振力,测量振动时效前后主焊缝附近的残余应力水平。通过对比分析发现,振动时效技术可以有效降低固桩架焊接过程中产生的残余应力,达到调整、均化、降低残余应力水平、提高构件尺寸精度稳定性的效果,有利于提升平台的使用寿命。