肺部孤立性小结节病变的CT表现及鉴别诊断

目的讨论肺部小结节的良恶性病变的影像表现及鉴别诊断. 材料与方法搜集经手术证实的肺部小结节病变共17例(直径〈3.0cm〉,男性11例,女性6例,年龄38-83岁,平均63.2岁.采用PQ5000螺旋CT机进行螺旋扫描,7例进行增强扫描,其中5例进行三维重建结果 17例病变中恶性病例12例,良性病例5例,恶性病变中腺癌8例,鳞癌2例,转移癌2例,良性病变中结核3例,炎性结节2例CT征象包括分叶征14例,胸膜凹陷征7例,血管集束征8例,毛刺征14例,密度不均匀者13例.结论 CT扫描对于鉴别肺部良恶性小结节病灶有重要价值.     

A study of SAR remote sensing of internal solitary waves in the north of the South China Sea: Ⅱ. Simulation of SAR signatures of internal solitary waves

A new model developed from the full-spectrum model of Lyzenga and Bennett （ 1988 ） is built up by us preliminarily through considering the impact of the ocean surface mixed layer turbulence on SAR remote sensing of internal solitary waves. In the partial differential equation of the action spectral density of the surface gravity-capillary waves the source function representing the contribution of the turbulence is added besides the usual source function representing the contribution of the wind. The source function is determined by applying the κ - ε model and adopting the Nasmyth spectrum of oceanic turbulence （ Nasmyth, 1970; Oakey, 1982; Fan, 2002） on the basis of the previous simulation results of internal tide transformation obtained in the companion paper （Fan et al. ,2008）. Either under relatively high wind speed, or under low wind speed, our model predicts significant large modulations of radar backscatter at all three bands （ L, C and X bands） for both VV and HH polarization. These results prove that considering the impact of ocean surface mixed layer turbulence on SAR remote sensing of internal solitary waves is reasonable and appropriate for settlement of the well-known problem of contemporary radar imaging models.     

Evaluation of Inference Adequacy in Cumulative Logistic Regression Models: An Empirical Validation of ISWRidge Relationships

Internal solitary wave propagation over a submarine ridge results in energy dissipation, in which the hydrodynamic interaction between a wave and ridge affects marine environment. This study analyzes the effects of ridge height and potential energy during wave-ridge interaction with a binary and cumulative logistic regression model. In testing the Global Null Hypothesis, all values are p＜0.001, with three statistical methods, such as Likelihood Ratio, Score, and Wald. While comparing with two kinds of models, tests values obtained by cumulative logistic regression models are better than those by binary logistic regression models. Although this study employed cumulative logistic regression model, three probability functions 1, 2 and 3, are utilized for investigating the weighted influence of factors on wave reflection. Deviance and Pearson tests are applied to check the goodness-of-fit of the proposed model. The analytical results demonstrated that both ridge height (X1) and potential energy (X2) significantly impact (p＜0.0001) the amplitude-based reflected rate; the P-values for the deviance and Pearson are all ＞0.05 (0.2839, 0.3438, respectively). That is, the goodness-of-fit between ridge height (X1) and potential energy (X2) can further predict parameters under the scenario of the best parsimonious model.Investigation of 6 predictive powers (R2, Max-rescaled R2, Somers'D, Gamma, Tau-a, and c, respectively) indicate that these predictive estimates of the proposed model have better predictive ability than ridge height alone, and are very similar to the interaction of ridge height and potential energy. It can be concluded that the goodness-of-fit and prediction ability of the cumulative logistic regression model are better than that of the binary logistic regression model.     

南海内波研究前沿与热点

内波为发生在层结海洋内部的亚中尺度波动,是物理海洋学研究,特别是海洋混合及能量级串研究,不可或的缺环节。孤立内波的突发性巨大冲击能量可对水下航行和工程设施构成灾难性威胁,实现实时监测与预报海洋内波具有重大现实意义。南海是全球海洋中超强内波多发海区之一。长期现场观测表明,吕宋海峡以西海域内孤立波振幅高达150～200 m,且终年发生。因此,南海是目前海洋内孤立波观测与研究热点海域。本文以2015年至2021年间发表的论文为依据,评述南海内波研究新进展,认为7 a来研究成果取得质的提升。第一,实现了由卫星为主要手段2D观测到以卫星与潜标同步3D观测为主要手段的提升。由此催生出振幅240 m超强内孤立波、中尺度涡对内波的调制作用、重现周期23 h内孤立波、浅海内孤立波裂变现象、深海盆内波及动能级串等创新成果。第二,研究区开始呈现向中部深海盆扩展趋势。迄今为止,南海内波观测与研究集中在吕宋海峡以西和北部陆架,现已出现向中部深海盆扩展趋势。第三,海洋探测高新技术应用于南海内波观测与研究,取得了突破性成果。由卫星高度计沿轨海面高度场二维平面波分解技术得出的南海M2内潮辐射图,解决了多年争论不休的南...     

低纬大气Kelvin波和Rossby波的非线性相互作用

利用多重尺度摄动法,对低纬大气Kelvin波和Rossby波的波包演变进行了分析,得到两波的非线性相互作用方程为耦合的非线性复系数Landau方程组。数值计算表明两波相遇将使波振幅变化,波宽变窄;两波非线性相互作用可能是低纬强烈天气突然爆发的原因之一。     

Assessing the west ridge of Luzon Strait as an internal wave mediator

The Luzon Strait is blocked by two meridional ridges at depths, with the east ridge somewhat higher than the west ridge in the middle reaches of the Strait. Previous numerical models identified the Luzon Strait as the primary generation site of internal M₂ tides entering the northern South China Sea (Niwa and Hibiya, 2004), but the role of the west-versus-east ridge was uncertain. We used a hydrostatic model for the northern South China Sea and a nonhydrostatic, process-oriented model to evaluate how the west ridge of Luzon Strait modifies westward propagation of internal tides, internal bores and internal solitary waves. The dynamic role of the west ridge depends strongly on the characteristics of internal waves and is spatially inhomogeneous. For M₂ tides, both models identify the west ridge in the middle reaches of Luzon Strait as a dampener of incoming internal waves from the east ridge. In the northern Luzon Strait, the west ridge is quite imposing in height and becomes a secondary generation site for M₂ internal tides. If the incoming wave is an internal tide, previous models suggested that wave attenuation depends crucially on how supercritical the west ridge slope is. If the incoming wave is an internal bore or internal solitary wave, our investigation suggests a loss of sensitivity to the supercritical slope for internal tides, leaving ridge height as the dominant factor regulating the wave attenuation. Mechanisms responsible for the ridge-induced attenuation are discussed.     

抛物线型背景流对内孤立波特征和能量影响的数值模拟研究

本文基于南海东北部观测的抛物线型背景流,设计了8种形式的抛物线型背景流,利用IGW模式研究了其对内孤立波(ISW)的特征和能量学的影响。研究结果表明:背景流对波包中ISW数目没有影响,但减小了ISW的相速度;对于下边界在主温跃层附近或在其上的抛物线型背景流,ISW振幅和最大位移深度均增加;随着抛物背景流曲率减小,ISW振幅、斜压与正压能比值减小,同时ISW相速度、正压能、斜压能、KE/APE都增加;如果抛物背景流底部延伸至海底,且曲率减小,则ISW振幅、相速度减小,同时正压能、斜压能、KE/APE增加;在整个深度上的背景流,随着下层曲率减小和上层曲率增大,ISW振幅、相速度、斜压与正压能比值、斜压能、KE/APE均增加。     

Experimental investigation of the load exerted by nonstationary internal solitary waves on a submerged slender body over a slope

Laboratory experiments are performed in a large stratified fluid flume to examine the characteristics of the load on a submerged slender body that is exerted by a nonstationary internal solitary wave (ISW) from its interaction with a gentle slope. The nonstationary ISW over the slope and its load on the body are measured by using multi-channel conductivity-probe arrays and a specially designed force measurement device, respectively, and the body’s vertical and horizontal positions on the load are determined by analyzing the effects of the incident ISW’s amplitude. The experimental results show that the load on the slender body increases as the incident ISW’s amplitude increases; additionally, the effect of oscillations is enhanced because of the ISW’s distortion, breaking and fission. The oscillating action from fission waves becomes dominant as the amplitude reaches a certain value. Additionally, the load is correlated with body’s vertical position relative to the pycnocline. The magnitudes of the vertical and horizontal forces reach a maximum and minimum in the pycnocline, respectively, and the horizontal force in this direction is the opposite above and below the pycnocline. Compared to a case without a slope, the load on the slender body increases because of the nonstationary ISW, and its effect on the maximum force is transferred to the pycnocline. When the body’s horizontal position is located close to the top of the slope, the direction of the horizontal and vertical forces remains consistent, but its acting time becomes longer. In addition, high-frequency actions on the slender body are impacted by nonstationary ISWs near the slope’s top.     

Numerical study on evolution of an internal solitary wave across an idealized shelf with different front slopes

Numerical simulations are performed to investigate the influence of variable front slopes on flow evolution and waveform inversion of a depression ISW (internal solitary wave) over an idealized shelf with variable front slopes. A finite volume based on Cartesian grid method is adopted to solve the Reynolds averaged Navier-Stokes equations using a k-ε model for the turbulent closure. Numerical results exhibit the variations of several pertinent properties of the flow field, in the case with or without waveform inversion on the horizontal plateau of an obstacle. The clockwise vortex is stronger than the counterclockwise one, almost throughout the wave-obstacle interaction. Analysis of the turbulent energy budget reveals that the turbulent production term in the governing equations dominates the wave evolution during a wave-obstacle interaction; otherwise the buoyancy production term and the dissipation term due to viscosity within turbulent eddies play a major role in energy dissipation. In addition, the front slope affects mainly the process and reflection of the wave evolution but has less influence than other physical parameters. Moreover, total wave energy of the leading crest is smaller than that of the leading trough even in the cases with waveform inversion on the plateau.     

On the structure and propagation of internal solitary waves generated at the Mascarene Plateau in the Indian Ocean

Analysis of a comprehensive dataset of Synthetic Aperture Radar (SAR) images acquired over the sea area around the Mascarene Plateau in the western Indian Ocean reveals, for the first time, the full two-dimensional spatial structure of internal solitary waves in this region of the ocean. The satellite SAR images show that powerful internal waves radiate both to the west and east from a central sill near 12.5°S, 61°E between the Saya de Malha and Nazareth Banks. To first order, the waves appear in tidally generated packets on both sides of the sill, and those on the western side have crest lengths in excess of 350 km, amongst the longest yet recorded anywhere in the world's oceans. The propagation characteristics of these internal waves are well described by first mode linear waves interacting with background shear taken from the westward-flowing South Equatorial Current (SEC), a large part of which flows through the sill in question. Analysis of the timings and locations of the packets indicates that both the westward- and eastward-traveling waves are generated from the western side of the sill at the predicted time of maximum tidal flow to the west. The linear generation mechanism is therefore proposed as the splitting of a large lee wave that forms on the western side of the sill, in a similar manner to that already identified for the shelf break generation of internal waves in the northern Bay of Biscay. While lee waves should form on either side of the sill in an oscillatory tidal flow, that on the western side would be expected to be much larger than that on the eastern side because of a superposition of the tidal flow and the steady westward flow of SEC. The existence of a large lee wave at the right time in the tidal cycle is then finally confirmed by direct observations. Our study also confirms the existence of second mode internal waves that form on the western side of the sill and travel across the sill towards the east.