基于响应面弹性充液水消声器声学性能优化研究

为有效控制通海水管路系统管内流噪声,尤其是降低通海管路管口辐射噪声级,提出一种带有新型弹性背腔和气囊结构、具备阻隔管路噪声传递功能的弹性充液水消声器。首先建立新型弹性背腔单元声学传递矩阵,并通过仿真分析弹性背腔单元声学特性;其次,根据Box-Behnken响应面优化方法设计水消声器传递损失试验,通过湖试台架声学试验,采用两负载法获得水消声器多型样机传递损失结果;最后,根据试验结果建立传递损失与试验因素间的数学模型,获得不同结构变量对传递损失的二阶交互作用响应面,深入分析不同结构变量间交互影响关系,并通过试验对得到的最优试验条件进行验证。结果表明,数学模型和试验数据相关性较高、拟合程度较好,设计的水消声器能有效降低通海水管路系统管内流噪声,根据数学模型优化设计的水消声器可使管口辐射噪声级降低9.6 dB。

航空瞬变电磁数据背景场去除研究

与地面瞬变电磁法相比,航空瞬变电磁法受不同的噪声类型影响较大,如天电噪声、运动噪声等,并且背景场对数据的影响也是不可忽略的。由于背景场中含有一次场信息,使得背景场幅值远大于含有地质信息的二次场信号。为较清晰地获得地下电性结构,需找到可以高效去除背景场的方法。本文提出利用线性插值方法来对背景场问题进行研究。首先,获得前、后高空飞行的测线数据,经过叠加、平均计算得到叠加周期内相同采样时间道的响应值,然后,利用插值原理针对每个采样时间道建立一个插值函数,最后,根据飞行时间来计算工区每条测线上采集数据的背景场值,从而达到去除背景场的目的。实测数据背景场去除的算例表明,该方法可较好地去除背景场对二次场异常的掩盖,去除后可较清晰地判断异常出现的位置。时间域航空电磁数据预处理包含较多处理模块,该方法的提出为高效的数据处理奠定了基础。

3D magnetotelluric inversions with unstructured finite-element and limited-memory quasi-Newton methods

Traditional 3D Magnetotelluric(MT) forward modeling and inversions are mostly based on structured meshes that have limited accuracy when modeling undulating surfaces and arbitrary structures. By contrast, unstructured-grid-based methods can model complex underground structures with high accuracy and overcome the defects of traditional methods, such as the high computational cost for improving model accuracy and the difficulty of inverting with topography. In this paper, we used the limited-memory quasi-Newton(L-BFGS) method with an unstructured finite-element grid to perform 3D MT inversions. This method avoids explicitly calculating Hessian matrices, which greatly reduces the memory requirements. After the first iteration, the approximate inverse Hessian matrix well approximates the true one, and the Newton step(set to 1) can meet the sufficient descent condition. Only one calculation of the objective function and its gradient are needed for each iteration, which greatly improves its computational efficiency. This approach is well-suited for large-scale 3D MT inversions. We have tested our algorithm on data with and without topography, and the results matched the real models well. We can recommend performing inversions based on an unstructured finite-element method and the L-BFGS method for situations with topography and complex underground structures.

术中亚低温治疗急性颅脑损伤后CD4^+、CD8^+及比值变化

目的探讨术中亚低温对颅脑损伤者CD4+、CD8+变化的影响。方法选择2010年1月—2015年12月在湖北随州市曾都医院实施开颅血肿清除的患者80例,按治疗方法不同分为两组(各40例)。观察组男性29例,女性11例;年龄31~60岁,平均45.2岁;入组GCS评分8~13分,平均10.3分。对照组男性30例,女性10例;年龄31~60岁,平均45.3岁;入组GCS评分8~13分,平均10.4分。对照组行常规去骨瓣减压血肿清除术,观察组在对照组基础上结合术中亚低温,比较干预后CD4+、CD8+、CD4+/CD8+、免疫球蛋白、欧洲脑卒中评分(ESS)、Barthel指数及Fugl-Meyer评分变化情况。结果干预后观察组CD4+、CD8+高于对照组[(35.1±2.0)%vs.(26.0±0.9)%,(30.6±1.3)%vs.(24.4±1.0)%,P<0.05],CD4^+/CD8^+高于对照组(1.9±0.3 vs.1.6±0.2,P<0.05),Ig M、Ig G、Ig A高于对照组(1.60±0.03 vs.1.32±0.02,9.52±0.12 vs.8.84±0.10,3.91±0.20 vs.1.83±0.15,P<0.05),ESS、Barthel指数、Fugl-Meyer评分高于对照组(P<0.05)。结论术中亚低温能有效减少手术对患者免疫功能影响,促进神经功能恢复,提高生活质量及肢体功能。

Efficient finite-volume simulation of the LWD orthogonal azimuth electromagnetic response in a three-dimensional anisotropic formation using potentials on cylindrical meshes

In this study,the cylindrical finite-volume method(FVM)is advanced for the efficient and high-precision simulation of the logging while drilling(LWD)orthogonal azimuth electromagnetic tool(OAEMT)response in a three-dimensional(3 D)anisotropic formation.To overcome the ill-condition and convergence problems arising from the low induction number,Maxwell’s equations are reformulated into a mixed Helmholtz equation for the coupled potentials in a cylindrical coordinate system.The electrical fi eld continuation method is applied to approximate the perfectly electrical conducting(PEC)boundary condition,to improve the discretization accuracy of the Helmholtz equation on the surface of metal mandrels.On the base,the 3 D FVM on Lebedev’s staggered grids in the cylindrical coordinates is employed to discretize the mixed equations to ensure good conformity with typical well-logging tool geometries.The equivalent conductivity in a non-uniform element is determined by a standardization technique.The direct solver,PARDISO,is applied to efficiently solve the sparse linear equation systems for the multi-transmitter problem.To reduce the number of calls to PARDISO,the whole computational domain is divided into small windows that contain multiple measuring points.The electromagnetic(EM)solutions produced by all the transmitters per window are simultaneously solved because the discrete matrix,relevant to all the transmitters in the same window,is changed.Finally,the 3 D FVM is validated against the numerical mode matching method(NMM),and the characteristics of both the coaxial and coplanar responses of the EM field tool are investigated using the numerical results.

Airborne electromagnetic data denoising based on dictionary learning

Time-domain airborne electromagnetic(AEM)data are frequently subject to interference from various types of noise,which can reduce the data quality and affect data inversion and interpretation.Traditional denoising methods primarily deal with data directly,without analyzing the data in detail;thus,the results are not always satisfactory.In this paper,we propose a method based on dictionary learning for EM data denoising.This method uses dictionary learning to perform feature analysis and to extract and reconstruct the true signal.In the process of dictionary learning,the random noise is fi ltered out as residuals.To verify the eff ectiveness of this dictionary learning approach for denoising,we use a fi xed overcomplete discrete cosine transform(ODCT)dictionary algorithm,the method-of-optimal-directions(MOD)dictionary learning algorithm,and the K-singular value decomposition(K-SVD)dictionary learning algorithm to denoise decay curves at single points and to denoise profi le data for diff erent time channels in time-domain AEM.The results show obvious diff erences among the three dictionaries for denoising AEM data,with the K-SVD dictionary achieving the best performance.

Three-dimensional inversion of controlled-source audio-frequency magnetotelluric data based on unstructured fi nite-element method

We propose a new 3D inversion scheme to invert the near-and transition-zone data of CSAMT with topography accurately.In this new method,the earth was discretized into unstructured tetrahedra to fit the ragged topography and the vector fi nite-element method was adopted to obtain precise responses and good sensitivity.To simulate the attitude and shape of the transmitter,we divided a long-grounded transmitter into dipoles and integrated these dipoles to obtain good responses in the near-and transition-fi eld zones.Next,we designed an L2 norm-based objective functional and applied a standard quasi-Newton method as the optimization method to solve the inverse problem and guarantee steady convergence.We tested our 3D inversion method first on synthetic data and then on a field dataset acquired from select sites near Changbai Mountain,China.In both tests,the new inversion algorithm achieved excellent fitting between the predicted and observed data,even in near-and transition-fi eld zones,and the inversion results agreed well with the true model.These fi ndings reveal that the proposed algorithm is eff ective for 3D inversion of CSAMT data.

Gravity compression forward modeling and multiscale inversion based on wavelet transform

The main problems in three-dimensional gravity inversion are the non-uniqueness of the solutions and the high computational cost of large data sets. To minimize the high computational cost, we propose a new sorting method to reduce fluctuations and the high frequency of the sensitivity matrix prior to applying the wavelet transform. Consequently, the sparsity and compression ratio of the sensitivity matrix are improved as well as the accuracy of the forward modeling. Furthermore, memory storage requirements are reduced and the forward modeling is accelerated compared with uncompressed forward modeling. The forward modeling results suggest that the compression ratio of the sensitivity matrix can be more than 300. Furthermore, multiscale inversion based on the wavelet transform is applied to gravity inversion. By decomposing the gravity inversion into subproblems of different scales, the non-uniqueness and stability of the gravity inversion are improved as multiscale data are considered. Finally, we applied conventional focusing inversion and multiscale inversion on simulated and measured data to demonstrate the effectiveness of the proposed gravity inversion method.

3D forward modeling and response analysis for marine CSEMs towed by two ships

A dual-ship-towed marine electromagnetic （EM） system is a new marine exploration technology recently being developed in China. Compared with traditional marine EM systems, the new system tows the transmitters and receivers using two ships, rendering it unnecessary to position EM receivers at the seafloor in advance. This makes the system more flexible, allowing for different configurations （e.g., in-line, broadside, and azimuthal and concentric scanning） that can produce more detailed underwater structural information. We develop a three-dimensional goal-oriented adaptive forward modeling method for the new marine EM system and analyze the responses for four survey configurations. Ocean-ottom topography has a strong effect on the marine EM responses; thus, we develop a forward modeling algorithm based on the finite-element method and unstructured grids. To satisfy the requirements for modeling the moving transmitters of a dual-ship-towed EM system, we use a single mesh for each of the transmitter locations. This mitigates the mesh complexity by refining the grids near the transmitters and minimizes the computational cost. To generate a rational mesh while maintaining the accuracy for single transmitter, we develop a goal-oriented adaptive method with separate mesh refinements for areas around the transmitting source and those far away. To test the modeling algorithm and accuracy, we compare the EM responses calculated by the proposed algorithm and semi-analytical results and from published sources. Furthermore, by analyzing the EM responses for four survey configurations, we are confirm that compared with traditional marine EM systems with only in-line array, a dual-ship-towed marine system can collect more data.

3D parallel inversion of time-domain airborne EM data

To improve the inversion accuracy of time-domain airborne electromagnetic data, we propose a parallel 3D inversion algorithm for airborne EM data based on the direct Gauss-Newton optimization. Forward modeling is performed in the frequency domain based on the scattered secondary electrical field. Then, the inverse Fourier transform and convolution of the transmitting waveform are used to calculate the EM responses and the sensitivity matrix in the time domain for arbitrary transmitting waves. To optimize the computational time and memory requirements, we use the EM ＂footprint＂ concept to reduce the model size and obtain the sparse sensitivity matrix. To improve the 3D inversion, we use the OpenMP library and parallel computing. We test the proposed 3D parallel inversion code using two synthetic datasets and a field dataset. The time-domain airborne EM inversion results suggest that the proposed algorithm is effective, efficient, and practical.

Three-dimensional forward modeling for the SBTEM method using an unstructured fi nite-element method

In this study,we propose a three-dimensional(3D)forward modeling algorithm of surface-to-borehole transient electromagnetic(SBTEM)fields based on an unstructured vector fi nite-element method to analyze the characteristics of SBTEM responses for complex geoelectrical models.To solve the double-curl diff usion equation for the electric fi eld,we use an unstructured tetrahedral mesh to discretize the model domain and select the unconditionally stable backward Euler scheme to discretize the time derivative.In our numerical experiments,we use a grounded wire as a transmitting source.After validating the algorithm’s eff ectiveness,we first analyze the diffusion characteristics and detectability of the electromagnetic field.After that,we focus our attention on the distribution and the cause of zero bands for Ex and dBy/dt components with the hope of guiding future field surveys.Finally,by simulating diff erent models,we analyze the capability of the SBTEM method in detecting typical mineral veins so that we can provide a reference for mineral resource exploration in the deep earth.

Inversion of time-domain airborne EM data with IP effect based on Pearson correlation constraints

Due to the induced polarization(IP)eff ect,the sign reversal often occurs in timedomain airborne electromagnetic(AEM)data.The inversions that do not consider IP eff ect cannot recover the true umderground electrical structures.In view of the fact that there are many parameters of airborne induced polarization data in time domain,and the sensitivity diff erence between parameters is large,which brings challenges to the stability and accuracy of the inversion.In this paper,we propose an inversion mehtod for time-domain AEM data with IP effect based on the Pearson correlation constraints.This method uses the Pearson correlation coeffi cient in statistics to characterize the correlation between the resistivity and the chargeability and constructs the Pearson correlation constraints for inverting the objective function to reduce the non uniqueness of inversion.To verify the eff ectiveness of this method,we perform both Occam’s inversion and Pearson correlation constrained inversion on the synthetic data.The experiments show that the Pearson correlation constrained inverison is more accurate and stable than the Occam’s inversion.Finally,we carried out the inversion to a survey dataset with and without IP eff ect.The results show that the data misfit and the continuity of the inverted section are greatly improved when the IP eff ect is considered.

Fransdimensional Bayesian inversion of timedomain airborne EM data

To reduce the dependence of EM inversion on the choice of initial model and to obtain the global minimum, we apply transdimensional Bayesian inversion to time-domain airborne electromagnetic data. The transdimensional Bayesian inversion uses the Monte Carlo method to search the model space and yields models that simultaneously satisfy the acceptance probability and data fitting requirements. Finally, we obtain the probability distribution and uncertainty of the model parameters as well as the maximum probability. Because it is difficult to know the height of the transmitting source during flight, we consider a fixed and a variable flight height. Furthermore, we introduce weights into the prior probability density function of the resistivity and adjust the constraint strength in the inversion model by changing the weighing coefficients. This effectively solves the problem of unsatisfactory inversion results in the middle high-resistivity layer. We validate the proposed method by inverting synthetic data with 3% Gaussian noise and field survey data.

基于有理Krylov子空间法的可控源海洋电磁三维各向异性正演研究

海底沉积层层理发育较好,呈现出明显的各向异性.为了解时间域海洋电磁法在任意各向异性介质中响应特征,本文提出一种基于非结构网格有限单元法和有理Krylov子空间法的时间域海洋电磁正演模拟技术.与传统的后推欧拉时间离散方法相比,Krylov子空间法通过求解降阶的矩阵指数函数避免对时间步长的离散,计算效率更高.本文通过对主电导率张量进行欧拉旋转模拟介质的电各向异性,成功实现了三维介质时间域海洋电磁各向异性模拟.在与一维半解析解对比验证了算法的精度之后,本文分析和对比了不同电各向异性模型的振幅偏移距曲线及电场分量、电流密度分布特征.本文提出基于视电阻率极性图识别海底介质各向异性特征的方法,为进一步开展时间域海洋可控源电磁法各向异性三维反演和解释奠定基础.

基于模糊分析的电控柴油机掺烧丁醇性能优化

为优化丁醇/柴油电控柴油机的综合性能,首先,利用AVL-FIRE建立混合燃料发动机燃烧室模型,采用仿真值与台架试验值对比,对丁醇掺混比和EGR率单因素对发动机综合性能的影响进行仿真研究;然后,采用正交试验设计安排5个重要因素进行多参数优化匹配,将指示功率和NO排放作为评价指标,权重分别设为0.4和0.6.对仿真结果运用模糊数学分析,结果表明:对综合性能影响大小的顺序为:EGR率(a_(2))、丁醇掺混比(a_(1))、进气温度(a_(4))、进气压力(a_(3))、喷油提前角(a_(5));最优参数组合为:a_(1)=10%,a_(2)=12.5%,a_(3)=0.223 MPa,a_(4)=335.15 K,a_(5)=20.6°CA,该组合指示功率53.8 kW较原机的55 kW略低,NO排放质量分数2.2×10^(-4)%较原机的8.5×10^(-4)%降低了74.1%.该优化方法可以在满足动力性的同时,实现有效减少NO排放的目的.

阿帕替尼联合替吉奥对老年晚期胃癌的疗效

目的探讨阿帕替尼联合替吉奥对老年晚期胃癌疗效预测及预后影响。方法选取2016年3月到2018年3月收治的48例老年晚期胃癌患者为研究对象,采用随机数字法分为对照组(n=24)和观察组(n=24)。对照组患者接受单一替吉奥治疗,观察组患者接受阿帕替尼联合替吉奥治疗。比较两组患者的临床疗效和不良反应,同时比较两组治疗前后辅助性T细胞(Th) 1[肿瘤坏死因子(TNF)-α、干扰素(IFN)-γ]和Th2[白细胞介素(IL)-4、IL-19]类细胞因子水平变化,并统计两组患者的总体生存期(OS)和肿瘤进展时间(TTP)。结果对照组和观察组疾病控制率分别为45. 83%和75. 00%,观察组高于对照组(P <0. 05)。治疗前两组TNF-α、IFN-γ、IL-4及IL-19水平差异无统计学意义(P> 0. 05),治疗后两组TNF-α、IFN-γ水平较治疗前有所上升,IL-4、IL-19水平较治疗前有所下降,且观察组TNF-α、IFN-γ水平显著高于对照组,IL-4、IL-19水平显著低于对照组,差异有统计学意义(P <0. 01)。治疗前两组缺氧诱导因子(HIF)-1α及血管内皮生长因子(VEGF)水平均无统计学差异(P> 0. 05),治疗后两组HIF-1α及VEGF水平均较治疗前有所下降,且观察组HIF-1α及VEGF水平显著低于对照组,差异有统计学意义(P <0. 05)。观察组的TTP和OS均显著长于对照组,差异有统计学意义(P <0. 05)。治疗期间两组均无死亡病例,且两组各不良反应发生率差异无统计学意义(P> 0. 05)。结论阿帕替尼联合替吉奥治疗能提高老年晚期胃癌的治疗疗效,且安全性可靠,可延长患者生存期。