浅海双深度Warping变换融合无源测距

针对浅海环境中利用单深度接收信号自相关函数的Warping变换方法测距时易出现的多值性问题,提出一种双深度Warping变换融合测距方法。该方法将双深度测量场的Warping变换提取结果与具有深度差异的拷贝场本征函数信息融合,判别简正波干涉项模态,提高测距的准确度。此外,针对实际海洋环境中测量场Warping变换特征峰位置难以准确提取的问题,将Warping变换的频率不变性与图像形态学方法结合以增强特征频率结构,提高后续测距的稳健性。海试数据处理结果显示,测距结果与实际距离符合较好,表明所提方法具有实际可行性。

A convergent flow in warped product spaces

In this paper,we study a kind of curvature flow in warped product spaces.We obtain convergence results under barrier conditions and restrictions on prescribed function.We also obtain the asymptotic behavior of a kind of inverse curvature flow in Schwarzschild manifold.

On the efficient non-linear solver for hydraulic fracturing and well cementing simulations based on Anderson acceleration

The aim of this study is to create a fast and stable iterative technique for numerical solution of a quasi-linear elliptic pressure equation. We developed a modified version of the Anderson acceleration(AA)algorithm to fixed-point(FP) iteration method. It computes the approximation to the solutions at each iteration based on the history of vectors in extended space, which includes the vector of unknowns, the discrete form of the operator, and the equation's right-hand side. Several constraints are applied to AA algorithm, including a limitation of the time step variation during the iteration process, which allows switching to the base FP iterations to maintain convergence. Compared to the base FP algorithm, the improved version of the AA algorithm enables a reliable and rapid convergence of the iterative solution for the quasi-linear elliptic pressure equation describing the flow of particle-laden yield-stress fluids in a narrow channel during hydraulic fracturing, a key technology for stimulating hydrocarbon-bearing reservoirs. In particular, the proposed AA algorithm allows for faster computations and resolution of unyielding zones in hydraulic fractures that cannot be calculated using the FP algorithm. The quasi-linear elliptic pressure equation under consideration describes various physical processes, such as the displacement of fluids with viscoplastic rheology in a narrow cylindrical annulus during well cementing,the displacement of cross-linked gel in a proppant pack filling hydraulic fractures during the early stage of well production(fracture flowback), and multiphase filtration in a rock formation. We estimate computational complexity of the developed algorithm as compared to Jacobian-based algorithms and show that the performance of the former one is higher in modelling of flows of viscoplastic fluids. We believe that the developed algorithm is a useful numerical tool that can be implemented in commercial simulators to obtain fast and converged solutions to the non-linear problems described above.

Time-Lapse Full-Waveform Inversion Using Cross-Correlation-Based Dynamic Time Warping

Offshore carbon capture, utilization, and storage(OCCUS) is regarded as a crucial technology for mitigating greenhouse gas emissions.Quantitative monitoring maps of sealed carbon dioxide are necessary in a comprehensive OCCUS project. A potential high-resolution method for the aforementioned purpose lies in the full-waveform inversion(FWI) of time-lapse seismic data. However, practical applications of FWI are severely restricted by the well-known cycle-skipping problem. A new time-lapse FWI method using cross-correlation-based dynamic time warping(CDTW) is proposed to detect changes in the subsurface property due to carbon dioxide(CO_(2)) injection and address the aforementioned issue. The proposed method, namely CDTW, which combines the advantages of cross-correlation and dynamic time warping, is employed in the automatic estimation of the discrepancy between the seismic signals simulated using the baseline/initial model and those acquired. The proposed FWI method can then back-project the estimated discrepancy to the subsurface space domain, thereby facilitating retrieval of the induced subsurface property change by taking the difference between the inverted baseline and monitor models. Numerical results on pairs of signals prove that CDTW can obtain reliable shifts under amplitude modulation and noise contamination conditions. The performance of CDTW substantially outperforms that of the conventional dynamic time warping method. The proposed time-lapse fullwaveform inversion(FWI) method is applied to the Frio-2 CO_(2) storage model. The baseline and monitor models are inverted from the corresponding time-lapse seismic data. The changes in velocity due to CO_(2) injection are reconstructed by the difference between the baseline and the monitor models.

Prediction of the undrained shear strength of remolded soil with non-linear regression,fuzzy logic,and artificial neural network

This study aims to predict the undrained shear strength of remolded soil samples using non-linear regression analyses,fuzzy logic,and artificial neural network modeling.A total of 1306 undrained shear strength results from 230 different remolded soil test settings reported in 21 publications were collected,utilizing six different measurement devices.Although water content,plastic limit,and liquid limit were used as input parameters for fuzzy logic and artificial neural network modeling,liquidity index or water content ratio was considered as an input parameter for non-linear regression analyses.In non-linear regression analyses,12 different regression equations were derived for the prediction of undrained shear strength of remolded soil.Feed-Forward backpropagation and the TANSIG transfer function were used for artificial neural network modeling,while the Mamdani inference system was preferred with trapezoidal and triangular membership functions for fuzzy logic modeling.The experimental results of 914 tests were used for training of the artificial neural network models,196 for validation and 196 for testing.It was observed that the accuracy of the artificial neural network and fuzzy logic modeling was higher than that of the non-linear regression analyses.Furthermore,a simple and reliable regression equation was proposed for assessments of undrained shear strength values with higher coefficients of determination.

Isometric Immersions of Lightlike Warped Product Manifolds

In this paper, we deal with isommetric immersions of globally null warped product manifolds into Lorentzian manifolds with constant curvature c in codimension k≥3. Under the assumptions that the globally null warped product manifold has no points with the same constant sectional curvature c as the Lorentzian ambient, we show that such isometric immersion splits into warped product of isometric immersions.

Crealet presents its innovative warp tension solutions at Techtextil 2024

Crealet is the world leader in sophisticated warp feeding technology and tailored solutions.Controlled warp tension stands also for controlled fabric quality.The Swiss firm presents its latest developments for technical textile applications at Techtextil 2024 in Frankfurt,Germany.

MRI去金属伪影WARP序列在关节假体周围感染中的应用

MRI去金属伪影WARP序列在关节假体周围感染中的应用。方法 选取2021年1月-2022年12月本院收治的关节假体周围感染患者62例为观察对象,62例患者均接受常规序列、WARP序列检查。分析62例患者的诊断效果。结果 WARP序列检查最大层面伪影平均面积优于常规序列(P〈0.05);WARP序列检查 图像清晰度、手术指导作用、信噪比优于常规序列(P〈0.05)。结论 MRI去金属伪影WARP序列可以在关节假体周围感染的诊断、评估中起到积极作用。

一种基于warping变换的浅海脉冲声源被动测距方法

针对浅海波导中脉冲声源被动测距问题,提出了一种利用接收信号的能量密度函数进行warping变换的声源被动测距方法.对于浅海波导,接收信号的能量密度函数中不同号简正波相干部分,经warping变换后输出结果的频谱中包含与声源和接收器位置无关的不变性频率特征.这些特征频率在数值上等于理想波导中相干的两号简正波的截止频率差,与海底参数无关,因此仅需已知海水中的平均声速和海水深度便可计算出特征频率值.当声源距离未知时,利用特征频率的提取值与真实特征频率之间的关系可以实现快速测距,极大地提高了计算速度.为了验证方法的有效性,对2011年11月黄海海域水声实验的接收脉冲数据进行了处理,测距结果与实测距离符合良好,平均测距误差在8%以内.

基于WARP的无线通信实验研究平台设计

针对无线通信研究与教学实验软硬件分离导致的实验结果不准确与实验效果不直观问题,设计实现了基于Matlab与Wireless Open Access Research Platform(WARP)的可视化实验研究平台。该平台基于WARPLAB环境,并以802.11n物理层标准为原型实现了2×2 MIMO-OFDM传输系统。基于该平台可以进行MIMO无线通信、信源编解码、实测信道参数与OFDM无线通信理论等研究教学实验活动。

基于平面的Warping技术

提出了一种基于平面的逆向Warping算法,用于根据多幅参考图像生成任意视点下的新图像.首先通过参考图像的深度信息来重建三维平面,然后寻找这些重建平面间的对应关系,并比较它们对空间平面同一部分的采样密度,以获得最好的采样结果.在生成新视点图像时,首先对那些采样密度最好的重建平面进行可见性判断,然后将其投影到新视点下,在此基础上求得目标图像上各点的深度,最后将目标图像上的点逆向Warping到相应的参考图像中,以获取它们的颜色值.同时,对于参考图像中不能被重建成平面的像素点,用正向Warping的方法对其进行处理.实验数据显示,此算法的时间效率不会随着参考图像的增加而急剧下降,并且由于只保存了参考图像中采样密度最好的重建平面,所以算法对存储量的要求也很小.

基于图像Warping的空洞填补方法

1 引言 Warping是一种基于图像的绘制方法(Image-Based Rendering,IBR).IBR是近几年来出现的一种新的真实感绘制方法,受到了计算机图形学界研究人员的普遍关注.IBR是通过一组预先获得的图像,根据不同的视点,来产生新的场景画面.与传统的绘制技术相比,IBR具有不需要建立三维模型,图形绘制独立于场景复杂度,既可以使用计算机生成的图像,也可以用实拍的相片,对工作平台的要求较低等优点.

基于几何与图像混合绘制中的快速WARP变换算法研究

基于几何与图像的混合绘制中 ,3D Warp算法以严格的数学变换为基础 ,从而能够保证准确的投影关系 .但该算法在实时绘制阶段需进行大量的数学运算 ,故其时间复杂度较高 .该文提出了一种新的快速 Warp变换算法 ,算法以 3D Warp算法为基础 ,采用了崭新的投影过程 ,从而使时间复杂度较 3D Warp算法有较大幅度的下降(降低约 7.5 1倍 ) .同时 ,该算法是一种流水结构 ,能够有效利用现有的加速硬件 。

The ridgelet transform with non-linear threshold for seismic noise attenuation in marine carbonates

Wavelet transforms have been successfully used in seismic data processing with their ability for local time - frequency analysis. However, identification of directionality is limited because wavelet transform coefficients reveal only three spatial orientations. Whereas the ridgelet transform has a superior capability for direction detection and the ability to process signals with linearly changing characteristics. In this paper, we present the issue of low signal-to-noise ratio （SNR） seismic data processing based on the ridgelet transform. Actual seismic data with low SNR from south China has been processed using ridgelet transforms to improve the SNR and the continuity of seismic events. The results show that the ridgelet transform is better than the wavelet transform for these tasks.

一种基于双引导声源和warping变换的拷贝声场计算方法

提出了在均匀浅海环境中只知道少量环境参数的情况下，利用不同距离上的两枚引导声源和warping变换的拷贝声场计算方法。这种方法主要基于简正波估计技术，从声场衰减信息和相位信息两个方向来重构拷贝声场，从而与目标声场匹配进行定位。其优点在于能避免传统的匹配场定位技术中拷贝场计算时对环境模型和环境参数的依赖。在简正波估计技术中采用warping变换的处理方式，数值仿真主要采用线性Bartlett匹配处理器分析了目标定位效果，在信噪比高于10-15dB的情况下，定位效果良好。

Microstructure evolution of Al-Zn-Mg-Cu alloy during non-linear cooling process

The microstructure evolution and properties of an Al-Zn-Mg-Cu alloy were investigated under different non-linear cooling processes from the solution temperature, combined with in-situ electrical resistivity measurements, selected area diffraction patterns （SADPs）, transmission electron microscopy （TEM）, and tensile tests. The relative resistivity was calculated to characterize the phase transformation of the experimental alloy during different cooling processes. The results show that at high temperatures, the microstructure evolutions change from the directional diffusion of Zn and Mg atoms to the precipitation of S phase, depending on the cooling rate. At medium temperatures, q phase nucleates on A13Zr dispersoids and grain boundaries under fast cooling conditions, while S phase precipitates under the slow cooling conditions. The strength and ductility of the aged alloy suffer a significant deterioration due to the heterogeneous precipitation in medium temperature range. At low temperatures, homogeneously nucleated GP zone, η′ and η phases precipitate.

波导不变量误差对频域β-warping变换及浅海被动测距的影响

频域β-warping变换可将接收信号自相关函数中简正波互相关部分,变为时域上时延随声源距离线性增大的脉冲序列。对信号自相关函数进行β-warping变换需要已知波导不变量值。但是,在实际应用中,很难获得波导不变量的准确值。研究表明,在事先获得粗略的水体声速剖面参数的情况下,如果估计得到的波导不变量为其真实值的q倍,那么频域β-warping变换后得到的脉冲时延也会变为波导不变量取真实值时的q倍。进一步研究表明,在水平不变浅海波导中采用频域β-warping变换进行被动测距时,通过设置一个已知距离的引导声源,那么即使估计得到的波导不变量存在一定误差,实际测距结果仍与真实距离符合得较好。

基于Shear-Warp的加速透视体绘制算法

在医学图像的三维可视化中,不透明度传递函数和观察角度是需要频繁调节的,因此,难以实现实时体绘制。为了提高三维图像的视觉效果和重建效率,提出了一种加速的透视体绘制算法。依据不透明度传递函数的相关性对原有的min-max octree数据结构进行有效的再利用,从而加速体数据分类编码,以使在频繁改变不透明度传递函数和观察角度时,也能实现快速重建;基于透视Shear-Warp算法,并用即时中间切片插值重采样的方法,提高重建的效果。实验证明该方法不仅效率高,而且显示效果好。

用Shear-warp算法实现超声心脏图像的快速体绘制

Shear- warp是基于物体空间扫描的一种体绘制技术 ,与传统的体绘制法相比 ,具有速度快、图像质量高的特点。本文介绍了 Shear- warp算法的原理 ,并将该算法应用到旋转扫描超声心脏图像插值结果的可视化 ,实现了心脏三维解剖结构的快速、准确重建。

基于3D WARP的混合绘制算法研究

几何绘制 (GBR)是传统计算机图形学的研究内容 ,随着计算机图形学的发展 ,图象绘制 (IBR)成为研究热点 ,两者各有其优缺点 .其中 ,GBR具有绘制自由度大、速度慢等特点 ,需占用大量系统资源 ;而 IBR则正好相反 ,因此 ,寻找一种能够结合 GBR与 IBR优点 ,而又能克服其缺点的方法是必要的 .为了使几何绘制和图象绘制能够实现有机地结合 ,提出了一种全新的“基于几何与图象的混合绘制 (Geom etry and Image- Based Hybrid Rendering,GIBHR)”方法 ,并分析了 GIBHR的研究内容 ,同时给出了 GIBHR的绘制流程 .在此基础上 ,将 IBR领域的 3DWARP算法在几何绘制领域进行了进一步拓展与推论 ,证明了其可行性和有效性 ,提出了一种基于 3D WARP的混合绘制算法 ,最后对该算法进行了实验 .结果表明 ,该算法在提高几何绘制速度方面具有明显优势 。