16排螺旋CT3D及MIP在肝癌APS中的临床应用

目的:探讨16排螺旋CT三维及最大密度重建技术在肝癌动门脉分流诊断中的应用价值.方法:对64例肝癌伴动门脉分流患者的16排螺旋CT增强图像进行三维及最大密度重建,并对重建图像进行观察和分析(与CT轴位图像和数字减影血管造影图像进行对照).结果:16排螺旋CT三维及最大密度重建技术能全面、直观、多方位地显示肝癌动门脉分流的影像征象,并能较好显示动门脉分流导致的血液动力学改变.结论:16排螺旋CT三维及最大密度重建作为轴位CT图像的重要后处理技术,具有无创、直观、快速显示肝癌动门脉分流各种影像征象的特点,为临床诊断和治疗肝癌动门脉分流提供可靠的依据.     

18F-FDG PET/CT联合神经元抗体检测诊断神经系统副肿瘤综合征

目的:探讨全身18F-FDG PET/CT联合神经元抗体检测在神经系统副肿瘤综合征（PNS）患者诊疗中的应用价值。方法:回顾性收集56例临床疑诊PNS患者的临床、神经副肿瘤抗体检测及全身18F-FDG PET/CT资料,对照病理及临床随访结果,利用ROC曲线评价PET/CT、神经元抗体及二者联合检测结果的诊断效能。结果:56例疑诊PNS患者中,共有肿瘤患者20例,其中肿瘤伴PNS 19例,肿瘤伴脊髓转移1例。18F-FDG PET/CT显像提示肿瘤或可能肿瘤23例,其中20例为真阳性,3例为假阳性（随访结果分别为反流性食管炎、反应性骨改变、颈部炎性病变）,其余33例为真阴性;敏感度、特异度、准确度分别为100.0％、91.7％、94.6％。神经元抗体阳性33例,其中PNS伴肿瘤8例（抗Amphiphysin抗体脑炎3例,抗GABAB抗体脑炎2例,抗Yo抗体脑炎1例,抗Hu抗体脑炎2例）,PNS不伴肿瘤25例（LGI1抗体脑炎10例,抗Amphiphysin抗体脑炎3例,抗Hu抗体脑炎1例,抗GABAB抗体脑炎3例,抗Yo抗体脑炎3例,抗CASPR2、GAD65、NMDA、PNMA及SOX1抗体脑炎各1例）;神经元抗体阴性23例（其中伴肿瘤12例）;敏感度、特异度、准确度分别为40.0％、30.6％、33.9％。两种联合检测结果的敏感度、特异度、准确度分别为100.0％、33.3％、57.1％,50.0％、94.4％、78.6％。ROC分析显示AUC分别为0.958（P<0.001;95％CI,0.904～1.000）、0.353（P>0.05;95％CI,0.199～0.506）、0.667（P<0.05;95％CI,0.528～0.806）及0.672（P<0.05;95％CI,0.514～0.830）,18F-FDG PET/CT及两种联合检测方法具有统计学意义。结论:全身18F-FDG PET/CT可作为疑诊PNS患者无创筛查肿瘤的一线检查方法。      

Byproduct Formation During the Reduction of TCE by Zero-Valence Iron and Palladized Iron

Trichloroethene (TCE) was reduced with zero-valence iron and palladized iron in zero-head-space extractors. Progress of the reaction in these batch studies was monitored with purge-and-trap gas chromatography and a flame ionization detector. When a 5 ppm initial concentration of TCF. reacts with zero-valence iron, approximately 140 ppb of vinyl chloride persists for as long as 73 days. The concentration of vinyl chloride (approximately If) ppb) remaining with palladized iron is approximately an order of magnitude less than when zero-valence iron is the reductant. These data suggest that volatile byproducts may be under-represented in oilier published data regarding reduction with zero-valence metals. These results also demonstrate that the reduction of TCE with palladized iron (0.05 percent palladium) is more than an order of magnitude faster than with zero-valence iron. Wilh a 5:1 solution-to-solid ratio the TCE half-life with zero-valence iron is 7.41 hours. but is only 0.59 hours with the palladized iron.     

Vibration of cylindrical shells with clamped ends

A general method is outlined for the determination of natural frequencies of cylindrical shells with any boundary conditions when the effects of rotatory inertia and transverse shear deformation are included in the analysis. This is applied to cylindrical shells with both ends clamped. It is shown that the inclusion of these effects tends to have a greater effect upon frequencies of cylindrical shells with clamped ends than it does for corresponding shells with simply supported ends, for which numerical results are available. The authors suggest an empirical relation, which together with the latter results enables rapid estimates to be made of the effects of rotatory inertia and shear deformation on the frequencies of a wide range of cylindrical shells with clamped ends. An assessment of the accuracy of the theory with these effects included is made by comparing frequencies with values from a three-dimensional elasticity theory, but this comparison has to be restricted to cylindrical shells with simply supported ends.     

芦山7.0级地震近断层地震动的方向性

基于芦山7.0级地震中断层距小于100 km自由场台站的强震动记录观测数据,研究此次地震近断层地震动的方向性特性,并探讨方向性特性与震源破裂机制、断层距离和空间方位的关系.研究结果表明：（1）与距断层较远记录不同,近断层地震动在不同的观测方向上表现出显著的强度差异,存在明显的极大和极小作用方向.在不同的方向上,最大加速度反应可达最小值的4倍以上;（2）这种方向性差异在T=1.0 s以上的长周期段更为明显,在T=0.1 s以下的短周期段,地震动随方向变化的差异较小.地震动强度随方向变化的差异随周期增大而增大,不同方向上的加速度反应谱值的最大值与最小值之比从周期T=0.01 s时的约1.7增大到周期T=10 s时的约2.4;（3）在距离断层约35 km以内,地震动具有明显方向性,地震动卓越方向具有垂直断层走向的特征,随断层距的增大,这种方向性不明显.从不同方向上地震动强度的差异来看,随断层距增大,地震动强度在不同方向上的差异在减小,表现为各个周期的最大值/中值和最大值/最小值比值均随断层距离增大缓慢减小;（4）近断层地震动的方向性特性主要受断层上、下盘的相对运动所控制,其在长周期的卓越方向与水平同震位移方向一致,且该卓越方向上的地震动强度绝对大小与地震破裂造成的静态位移明显相关,表现为地震动强度随水平同震位移的增大而增大.     

胸膜原发性肿瘤的CT诊断

目的:探讨胸膜原发性肿瘤的CT表现,提高对该类疾病的认识。方法:回顾性分析经病理学证实的24例胸膜原发性肿瘤的CT资料。结果:24例中恶性间皮瘤9例,8例表现为胸膜弥漫性增厚及多发结节,1例局限性增厚,增强较明显不均匀强化3例,不均匀轻-中等强化6例,8例见胸腔积液,3例伴有淋巴结转移,1例见肝内及肺内转移。孤立性纤维瘤7例,3例表现为梭形肿块,4例呈半球形肿块,增强不均匀轻度到明显强化,5例见胸膜尾征,2例少量胸腔积液。神经鞘瘤5例,1例表现为梭形肿块,4例呈半球形、球形肿块,增强不均匀轻-中度强化,均见胸膜尾征。纤维脂肪瘤1例表现为脂肪及纤维混杂密度梭形团块,边界较清晰,增强见较多纤维成分延迟强化。滑膜肉瘤1例表现为巨大不规则肿块,增强不均匀强化,并见左侧肾上腺转移灶环状强化。炎性肌纤维母细胞瘤1例表现为球形等及稍低密度肿块,增强不均匀延迟强化。结论:胸膜原发性肿瘤少见,不同肿瘤的CT表现各有特点,CT对其诊断及鉴别诊断有重要价值。      

Nonplanar Faults: Mechanics of Slip and Off-fault Damage

Stress interactions and sliding characteristics of faults with random fractal waviness in a purely elastic medium differ both qualitatively and quantitatively from those of faults with planar surfaces. With nonplanar fault models, solutions for slip diverge as resolution of the fractal features increases, and the scaling of fault slip with fault rupture dimension becomes nonlinear. We show that the nonlinear scaling of slip and divergence of solutions arise because stresses from geometric interactions at irregularities along nonplanar faults grow with increasing slip and produce backstresses that progressively impede slip. However, in real materials with finite strength, yielding will halt the growth of the interaction stresses, which will profoundly affect slip of nonplanar faults. We infer that in the brittle seismogenic portion of the Earth’s crust, off-fault yielding occurs on pervasive secondary faults. Predicted rates of stress relaxation with distance from major faults with random fractal roughness follow a power-law relationship that is consistent with reported clustering of background seismicity up to 15 kilometers from faults.     

高轴压比下内藏钢桁架混凝土组合高剪力墙抗震试验研究

通过对3个1／3缩尺的高剪力墙模型（其中包括1个普通混凝土高剪力墙、1个内藏钢框架组合高剪力墙和1个内藏钢桁架组合高剪力墙）的抗震性能试验研究，探讨了不同组合形式剪力墙的承载力、刚度及其退化过程、延性、滞回特性及破坏特征。试验表明：内藏钢框架混凝土组合高剪力墙和内藏钢桁架混凝土组合高剪力墙的抗震性能比普通混凝土高剪力墙明显提高。     

The role of prior model calibration on predictions with ensemble Kalman filter

This paper, based on a real world case study (Limmat aquifer, Switzerland), compares inverse groundwater flow models calibrated with specified numbers of monitoring head locations. These models are updated in real time with the ensemble Kalman filter (EnKF) and the prediction improvement is assessed in relation to the amount of monitoring locations used for calibration and updating. The prediction errors of the models calibrated in transient state are smaller if the amount of monitoring locations used for the calibration is larger. For highly dynamic groundwater flow systems a transient calibration is recommended as a model calibrated in steady state can lead to worse results than a noncalibrated model with a well-chosen uniform conductivity. The model predictions can be improved further with the assimilation of new measurement data from on-line sensors with the EnKF. Within all the studied models the reduction of 1-day hydraulic head prediction error (in terms of mean absolute error [MAE]) with EnKF lies between 31% (assimilation of head data from 5 locations) and 72% (assimilation of head data from 85 locations). The largest prediction improvements are expected for models that were calibrated with only a limited amount of historical information. It is worthwhile to update the model even with few monitoring locations as it seems that the error reduction with EnKF decreases exponentially with the amount of monitoring locations used. These results prove the feasibility of data assimilation with EnKF also for a real world case and show that improved predictions of groundwater levels can be obtained.     

2012年6月30日新疆新源、和静交界Ms6．6地震的中期粗略预测

基于静中动判据和三性法,对2012年6月30日新源、和静交界Ms6．6地震的粗略中期预测作了回顾。静中动判据指的是1979年3月29日有一个6级地震在库车东北发生,它对预测大震的地区有指示意义。该震距2012年6月30日新源、和静交界Ms6．6地震约150km。由于地震越大与1外因的关系越密切,所以我们认为北天山地区1812年尼勒克8级地震与1911年阿拉木图81/2级地震之间的时间间隔为（4×25）-1年可能反映着有25年周期的外因存在,这个外因对7级地震也会有触发作用,1914年巴里坤7．5级地震即属于此。这3次大震组成的时间系列对以后大震的发生年份有一定指示意义,所以我们从1812年尼勒克大震的发生年份算起,经8×25年,即2012年作为库车周围200km的范围可能发生7级地震的年份。但实际发生的地震震级偏低,只有6．6级。     

基于有限差分正演的带地形三维大地电磁反演方法

本研究实现了一套基于有限差分（FD）方法的大地电磁测深数据带地形三维反演算法及代码.其中,在大地电磁场正演数值模拟方面,开发了起伏地形条件下基于交错网格剖分、有限差分方法的大地电磁测深三维正演代码;在满足平面波场假设的前提下,使用长方体网格剖分模拟三维起伏地形,实现了带地形三维正演计算;并设计理论模型进行试算,经试算结果与前人的有限元法计算结果对比,验证了所研发的带地形三维正演计算的正确性与可靠性.在反演方面,本研究基于非线性共轭梯度方法编写了大地电磁测深带地形三维反演代码,试验了不同的共轭梯度搜索因子β,避免了目标函数对海森矩阵（参数二次导数矩阵）的显式计算和存储,初步实现了大地电磁资料的带地形三维反演.最后,对一系列理论模型进行正演计算,利用其生成的合成数据模拟实测数据进行反演,并与现有的不带地形大地电磁测深三维反演结果比较,检验了所研发的带地形三维反演计算的可靠性与稳定性.     

周至井气压系数的变化特征及其与地震的关系

主要采用周至井水位、气压的时值,通过高阶差分回归拟合水位、气压的相关系数与气压系数。并对采用不同滑动步长、不同差分计算出不同时段内的气压系数进行了分析对比,比较了其异同。同时也探讨了相关系数和气压系数与地震的关系。     

Modelling the effect of waves,weathering and beach development on shore platform development

A mathematical model was used to study shore platform development. Mechanical wave erosion was dependent on such variables as tidal range, wave height and period, breaker height and depth, breaker type, surf zone width and bottom roughness, submarine gradient, rock resistance and the elevational frequency of wave action within the intertidal zone. Also included were the effects of sand and pebble accumulation, cliff height and debris mobility, and downwearing associated with tidal wetting and drying. The occurrence, location and thickness of beaches often depended on initially quite minor variations in platform morphology, but owing to their abrasive or protective effect on underlying rock surfaces, they were able to produce marked differences in platform morphology. Generalizations are difficult, but the model suggests that platform gradient increases with tidal range. Platform width also increases with tidal range with slow downwearing but it decreases with fast downwearing. Platform gradient decreases and width increases with wave energy, and decreasing rock resistance and platform roughness. With low tidal range, platform gradient is generally lower and platform width greater with beaches of fine sand than with gravel, but the relationship is more variable with a high tidal range. Platform width increases and platform gradient decreases with the rate of downwearing on bare surfaces, particularly in low tidal range environments, but the pattern is less clear on beach‐covered platforms. Platforms with large amounts of beach sediment tend to be narrower and steeper than bare platform surfaces. Platform gradient increases and platform width decreases with increasing cliff height and with decreasing cliff debris mobility. Copyright © 2005 John Wiley & Sons, Ltd.     

海啸波近岸共振响应的数值模拟及分析

应用有限差分方法求解非线性浅水长波方程,建立了海啸波产生和传播的二维数值模型;对太平洋地震引起的夏威夷群岛海啸波进行模拟,并将模拟结果和测站实测值进行比较,验证了模型的正确性。利用快速傅里叶变换对数值模拟结果进行谱分析,得到整个计算区域的能量谱分布,并给出了发生能量聚集的位置及相应的谱峰周期。讨论了海啸波传播到近岸时可能产生的共振响应现象,发现海啸波和近岸的共振响应不仅与近岸复杂地形有关,还与海啸波传播到近岸时的波浪入射方向有关。     

流体对石灰岩断层摩擦滑动影响的实验研究

在气体介质三轴高温岩石力学实验仪器上,采用意大利Scaglia Bianca石灰岩,在温度50～300℃、围压150MPa,含50MPa孔隙压、无孔隙压含饱和水和完全干燥三种条件下,开展摩擦滑动实验.实验力学数据和显微结构表明,完全干燥样品在120℃时出现慢滑移,实验样品中没有出现溶解与沉淀.无孔隙压含饱和水条件下,100℃、120℃、150℃条件下出现典型的慢滑移,实验样品中含有微弱的溶解与沉淀;300℃条件下出现黏滑,实验样品中出现沉淀.在含50MPa孔隙压条件下,50℃时的实验表现为典型的稳滑,实验样品中以溶解为主;在100～150℃时,出现慢滑移,实验样品中以溶解为主,沉淀为辅;在200～300℃时,出现典型黏滑,实验样品中以沉淀为主.实验结果表明,石灰岩断层泥摩擦滑动稳定性随温度变化,受流体中碳酸钙的溶解和沉淀作用控制,因此,流体中矿物质的饱和度这一化学性质对断层带的摩擦强度和摩擦滑动稳定性具有显著影响.     

Numerical modelling of downstream migrating antidunes

A numerical model is presented that compute the geometrical dimensions and movement of downstream migrating antidunes. The model solves the Navier–Stokes equations together with the k‐epsilon turbulence model to find the water flow field over the bedforms. A two‐dimensional width‐averaged grid is used. The bed elevation changes are computed by solving the convection–diffusion equation for suspended sediments and bedload, together with the Engelund–Hansen sediment transport formula. The free surface is computed with an algorithm based on water continuity in the surface cells. Non‐orthogonal adaptive grids were used, moving vertically with the computed location of the bed and the free water surface. The numerical model was tested on data from a physical model study where regular downstream migrating antidunes had been observed. The numerical model started out with a flat bed and the trains of antidunes formed over time. Many of the physical processes observed in earlier studies were replicated by the numerical model. Four dune parameters were computed in the current tests: The antidune wavelength, height and celerity, together with the average water depth. The antidune wavelengths were best predicted with an accuracy of 3 to 8% compared with the measurements. The antidune heights were computed with a deviation of 11 to 25% compared with an empirical formula. The water depths over the antidunes were predicted with an accuracy of 3 to 9% related to the measured values. The average antidune celerity was the parameter with largest deviation: For the coarsest grid it was overpredicted with 37%. Copyright © 2017 John Wiley & Sons, Ltd.     

1997～1998年伽师强震群小地震震源机制解系统聚类分析

用P、S波最大振幅比法计算1997~1998年伽师强震群MS2.5~3.7小地震震源机制解,对小地震震源机制解进行系统聚类分析。结果表明,伽师小地震主要以走滑和正断层为主,与该时段发生的伽师6级强震具有相似的断错性质。1997年伽师小地震主压应力P轴方位为北东或近南北向,与1997~1998年6级强震主压应力P轴方位一致。1997年4月6日6.4级和1998年8月2日6.1级两次6级正断层地震前出现地震空段现象。     

Experimental verification of effective anisotropic crack theories in variable crack aspect ratio medium

Physical modelling of cracked/fractured media using downscaled laboratory experiments has been used with great success as a useful alternative for understanding the effect of anisotropy in the hydrocarbon reservoir characterization and in the crustal and mantle seismology. The main goal of this work was to experimentally verify the predictions of effective elastic parameters in anisotropic cracked media by Hudson and Eshelby–Cheng's effective medium models. For this purpose, we carried out ultrasonic measurements on synthetic anisotropic samples with low crack densities and different aspect ratios. Twelve samples were prepared with two different crack densities, 5% and 8%. Three samples for each crack density presented cracks with only one crack aspect ratio, whereas other three samples for each crack density presented cracks with three different aspect ratios in their composition. It results in samples with aspect ratio values varying from 0.13 to 0.26. All the cracked samples were simulated by penny‐shaped rubber inclusions in a homogeneous isotropic matrix made with epoxy resin. Moreover, an isotropic sample for reference was constructed with epoxy resin only. Regarding velocity predictions performed by the theoretical models, Eshelby–Cheng shows a better fit when compared with the experimental results for samples with single and mix crack aspect ratio (for both crack densities). From velocity values, our comparisons were also performed in terms of the ε, γ, and δ parameters (Thomsen parameters). The results show that Eshelby–Cheng effective medium model fits better with the measurements of ε and γ parameters for crack samples with only one type of crack aspect ratio.     

The algorithms for calculating synthetic seismograms from a dipole source using the derivatives of Green’s function

The problem of calculating complete synthetic seismograms from a point dipole with an arbitrary seismic moment tensor in a plane parallel medium composed of homogeneous elastic isotropic layers is considered. It is established that the solutions of the system of ordinary differential equations for the motion–stress vector have a reciprocity property, which allows obtaining a compact formula for the derivative of the motion vector with respect to the source depth. The reciprocity theorem for Green’s functions with respect to the interchange of the source and receiver is obtained for a medium with cylindrical boundary. The differentiation of Green’s functions with respect to the coordinates of the source leads to the same calculation formulas as the algorithm developed in the previous work (Pavlov, 2013). A new algorithm appears when the derivatives with respect to the horizontal coordinates of the source is replaced by the derivatives with respect to the horizontal coordinates of the receiver (with the minus sign). This algorithm is more transparent, compact, and economic than the previous one. It requires calculating the wavenumbers associated with Bessel function’s roots of order 0 and order 1, whereas the previous algorithm additionally requires the second order roots.     

MSCT及后处理技术在腹外疝合并肠梗阻诊断中的应用价值

目的：探讨MSCT及后处理技术对腹外疝合并肠梗阻的诊断价值。方法：回顾性分析21例经手术证实腹外疝合并肠梗阻患者的MSCT资料。全部病例行全腹部MSCT检查,其中19例平扫,2例增强扫描。薄层横断面图像传至工作站行多平面重组成像（MPR）和曲面重组成像（CPR）等图像后处理。结果：2l例腹外疝合并肠梗阻患者经MSCT检查诊断明确,MSCT薄层横断面图像结合后处理技术显示腹外疝2l例,其中腹股沟斜疝8例,腹股沟直疝5例,切口疝4例,股疝2例,闭孔疝2例;其中13例为不完全性肠梗阻,8例为完全性肠梗阻。结论：MSCT及后处理技术在腹外疝合并肠梗阻的诊断中具有重要价值,为临床手术方案的制定提供准确可靠的影像学信息。