Fluid—Structure Interaction of Two-Phase Flow Passing Through 90° Pipe Bend Under Slug Pattern Conditions

China Ocean Engineering - Numerical simulations of evolution characteristics of slug flow across a 90° pipe bend have been carried out to study the fluid—structure interaction response...     

Spatial distribution of turbulent diapycnal mixing along the Mindanao current inferred from rapid-sampling Argo floats

The Mindanao Current (MC) bridges the North Pacific low-latitude western boundary current system region and the Indonesian Seas by supplying the North Pacific waters to the Indonesian Throughflow. Although the previous study speculated that the diapycnal mixing along the MC might be strong on the basis of the water mass analysis of the gridded climatologic dataset, the real spatial distribution of diapycnal mixing along the MC has remained to be clarified. We tackle this question here by applying a finescale parameterization to temperature and salinity profiles obtained using two rapid-sampling profiling Argo floats that drifted along the MC. The western boundary (WB) region close to the Mindanao Islands and the Sangihe Strait are the two mixing hotspots along the MC, with energy dissipation rate ε and diapycnal diffusivity K_ρ enhanced up to?~?10^–6 W kg^?1 and?~?10^–3 m² s^?1, respectively. Except for the above two mixing hotspots, the turbulent mixing along the MC is mostly weak, with ε and K_ρ to be 10^–11–10^–9 W kg^?1 and 10^–6–10^–5 m² s^?1, respectively. Strong mixing in the Sangihe Strait can be basically attributed to the existence of internal tides, whereas strong mixing in the WB region suggests the existence of internal lee waves. We also find that water mass transformation along the MC mainly occurs in the Sangihe Strait where the water masses are subjected to strong turbulent mixing during a long residence time.

     

A Lagrangian study of the near-surface intrusion of Pacific water into the South China Sea

Satellite-tracked Lagrangian drifters are used to investigate the transport pathways of near-surface water around the Luzon Strait. Particular attention is paid to the intrusion of Pacific water into the South China Sea(SCS).Results from drifter observations suggest that except for the Kuroshio water, other Pacific water that carried by zonal jets, Ekman currents or eddies, can also intrude into the SCS. Motivated by this origin problem of the intrusion water, numerous simulated trajectories are constructed by altimeter-based velocities. Quantitative estimates from simulated trajectories suggest that the contribution of other Pacific water to the total intrusion flux in the Luzon Strait is approximately 13% on average, much smaller than that of Kuroshio water. Even so, over multiple years and many individual intrusion events, the contribution from other Pacific water is quite considerable. The interannual signal in the intrusion flux of these Pacific water might be closely related to variations in a wintertime westward current and eddy activities east of the Luzon Strait. We also found that Ekman drift could significantly contribute to the intrusion of Pacific water and could affect the spreading of intrusion water in the SCS. A case study of an eddy-related intrusion is presented to show the detailed processes of the intrusion of Pacific water and the eddy-Kuroshio interaction.     

黄河口潮滩泥沙絮凝研究

本文基于现场观测的絮团粒径、悬沙浓度及水动力数据,研究了黄河口南部潮滩泥沙絮凝特征。研究发现,黄河口潮滩絮团粒径在25.42～264.44 μm之间,平均为95.20 μm。水体紊动对黄河口潮滩絮凝的影响存在差异,紊动对絮凝促进作用的上限约为G_l=3.76 s⁻¹。紊动强度低于G_l时,紊动促进泥沙絮凝,絮团粒径随紊动加强而增大;反之水体紊动对絮凝主要起抑制作用,絮团粒径随紊动强度增大而减小。悬沙浓度对黄河口潮滩泥沙絮凝起抑制作用,同等紊动条件下高悬沙浓度对应的絮团粒径更小。黄河口潮滩絮团有效密度与粒径呈现负相关关系,沉速主要受粒径影响。本研究补充了对弱潮河口潮滩泥沙絮凝特性的认识。     

潮沟系统水沙输运研究——以长江口崇明东滩为例

本研究以崇明东滩2015年4月实测潮间带水沙数据为基础,分析了潮沟、盐沼及光滩的水沙特征,重点研究了潮沟系统及邻近潮滩潮周期内悬沙通量情况。结果表明:（1）潮沟表层沉积物比潮滩细,二者平均中值粒径分别为21.7 μm和33.0 μm,悬沙粒径由海向陆逐渐变小;（2）大、小潮沟潮周期内潮流均以往复流为主,垂向平均流速分别为15.4 cm/s和34.6 cm/s;盐沼界和光滩则以旋转流为主,平均流速分别为11.3 cm/s和28.9 cm/s;（3）潮沟中的高悬沙浓度出现在涨潮初期,最大可达7.5 kg/m3,而潮滩高悬沙浓度则出现在潮落潮中期和高水位时刻;大、小潮沟和盐沼界站涨潮阶段平均悬沙浓度大于落潮阶段,光滩站则相反。潮沟悬沙主要来自邻近水域,而潮滩悬沙则与滩面表层沉积物密切相关;（4）潮沟在潮周期内净输沙方向均指向滩地,大潮沟潮周期单宽净输沙量可达4.0 t/m;盐沼界处垂直岸线和沿岸输沙强度相近,净输沙由海向陆,潮周期离岸输沙强度为1.0 t/m;光滩沿岸输沙强度远大于垂直岸线输沙,光滩净输沙由陆向海。研究揭示了潮间带潮沟系统的强供沙能力以及研究区域光滩冲蚀,盐沼植被带淤积的动力地貌过程。     

缢蛏天然抗性相关巨噬蛋白2(Sc-Nramp2)基因克隆及其在副溶血弧菌刺激下的表达分析

克隆得到缢蛏天然抗性相关巨噬蛋白2（Sc-Nramp2）基因的cDNA全长序列3 681 bp,该基因的开放阅读框有1 776 bp,编码591个氨基酸,预测分子量为65.86 kDa;其结构具有Slc11蛋白家族的典型特征,包括有10个典型的跨膜结构和2个糖基化位点。Sc-Nramp2基因3'-UTR有2个类似于脊椎动物Nramp2中铁反应控制蛋白结合位点;同源性分析表明,Sc-Nramp2和太平洋牡蛎Nramp2-like的同源性最高为71.6%。实时荧光定量PCR结果表明,Sc-Nramp2基因在闭壳肌、外套膜、肝胰腺、斧足、水管和鳃6个组织中均有表达,其中肝胰腺中的表达量最高,其次是鳃,与其他组织均有极显著性差异（P<0.01）;注射副溶血弧菌后,肝胰腺中Sc-Nramp2基因的表达量较对照组显著上调（P<0.01）,且表达量呈现先上升后下降的趋势,在12 h时达到最大表达量,推测Sc-Nramp2基因参与了缢蛏非特异性免疫应答反应。     

Interference phase of mass neutrino in Reissner—Nordstr?m—de Sitter space—time

In Reissner--Nordstr?m--de Sitter space--time, we calculate the interference phase of mass neutrino along geodesic in the radial direction, and then investigate the effects of the cosmological constant La on the phase. Morever, the expression of the interference phase can be reduced to that in Reissner--Nordstr?m space--time when Λ approaches to zero.     

氧化钒晶体的半导体至金属相变的理论研究

本文利用第一性原理方法研究了金红石相和单斜相VO₂晶体的电子结构和热力学性质.在计算中采用局域密度近似结合Hubbard U模型(LDA+U)描述电子的局域强关联效应,同时也利用微扰密度泛函方法计算了两种相结构的声子谱.计算结果表明V原子3d电子轨道中x²-y²轨道能级分裂决定了VO₂晶体在不同相结构下的金属和绝缘体特性.零温状态方程计算揭示了在68 GPa时可以发生从单斜结构     

Particle-Velocity-Field Difference Smoothing for Coherent Source Localization in Spatially Nonuniform Noise

This communication considers the problem of estimating 2-D directions of arrival (DOAs) of multiple coherent signals under spatially nonuniform noise (spatially inhomogeneous temporary white noise) using an array of vector hydrophones. A novel preprocessing method called particle-velocity-field difference smoothing (PVFDS) is proposed. The key idea underlying the PVFDS is to remove the spatially nonuniform noise by using the matrix difference of pairs of particle-velocity data correlation matrices, and to decorrelate the coherent signals by summing these difference correlation matrices. Unlike most of other existing preprocessing techniques, such as spatial smoothing and forward–backward averaging, the PVFDS processing does not decrease the array aperture. For arbitrary array geometries, the PVFDS can resolve up to four coherent signals, and for centro–symmetric arrays, forward–backward averaging can double this number to eight. Monte Carlo simulations illustrate that the PVFDS-based eigenstructure algorithms can offer better performance than the particle-velocity-field smoothing (PVFS)-based counterparts.      

三疣梭子蟹和华溪蟹主要器官比较组织学的初步研究

近年来随着养殖业的发展,蟹类病害频繁发生,日趋严重。在开展病害研究过程中,由于三疣梭子蟹Portunus trituberculatus的SPF(无特定病原体)材料难于获得,而试验蟹的获得又受到养殖条件、养殖周期等因素的限制,因此阻碍了相关研究的开展,尤其是病毒学研究的进展。筛选一种可替代的模式生物,并开展相关研究显得尤为迫切。华溪蟹Sinopotamon和三疣梭子蟹亲缘关系较近,作为野生的蟹类容易获得,价格低廉,也容易在实验室条件下饲养。笔者在梭子蟹病原研究中发现,华溪蟹不带梭子蟹病原,但在实验条件下可感染相关病原,是开展此两类蟹病原体研究的较好实验动物,有必要开展这两种蟹的组织比较形态学的基础研究,以支持相关的应用研究。笔者经过对三疣梭子蟹和华溪蟹的组织石蜡切片观察发现,两种蟹的各组织器官结构基本相似,各组织结构都由4层构成,即粘膜层、粘膜下层、肌层和外膜。上皮细胞分泌物形成几丁质板,覆盖在上皮细胞表面。三疣梭子蟹的食管粘膜下层较发达。华溪蟹食管粘膜下层的肌层均相对较薄,食管腔较小。这两种蟹的胃壁结构无明显差别。在三疣梭子蟹的局部胃壁,可见嗜酸性几丁质层,上皮细胞顶部间有间隙,间隙中有一些嗜碱性物质。三疣梭子蟹肠粘膜下层不明显。华溪蟹的中肠非常细小,被肝胰腺等组织包裹,难以分离,管腔小,管壁外结缔组织少。两种蟹肝胰腺均由许多分枝的肝小管组成,小管间为结缔组织,血窦。肝小管由单层柱状上皮构成,高低不等,可以明显区分出分泌细胞、吸收细胞、储存细胞和胚性细胞4种形态的细胞,其功能也不同。三疣梭子蟹鳃轴基本弯曲,窄处鳃轴与鳃丝粗细相当,鳃丝和鳃小片间隔较大。华溪蟹鳃轴笔直延伸,窄处鳃轴明显粗于鳃丝,鳃丝间隔较小。两者鳃小片均由扁平上皮组成,外侧有薄层几丁质板。华溪蟹的鳃血管中可以明显看到较多染成红色的血细胞。三疣梭子蟹心肌纤维排列松散,线粒体较少,形态多样。华溪蟹心肌纤维排列致密,线粒体多呈群分布,且数量更多。心肌由梭形心肌细胞组成,有横纹,彼此相连成网,其周围有少量原生质。肌细胞的核呈棒状。