Site effects by generalized inversion technique using strong motion recordings of the 2008 Wenchuan earthquake

The generalized inversion of S-wave amplitude spectra from the free-field strong motion recordings of the China National Strong Motion Observation Network System （NSMONS） are used to evaluate the site effects in the Wenchuan area. In this regard, a total of 602 recordings from 96 aftershocks of the Wenchuan earthquake with magnitudes of M3.7-M6.5 were selected as a dataset. These recordings were obtained from 28 stations at a hypocenter distance ranging from 30 km to 150 km. The inversion results have been verified as reliable by comparing the site response at station 62WUD using the Generalized Inversion Technique （GIT） and the Standard Spectral Ratio method （SSR）. For all 28 stations, the site predominant frequency F and the average site amplification in different frequency bands of 1.0-5.0 Hz, 5.0-10.0 Hz and 1.0-10.0 Hz have been calculated based on the inversion results. Compared with the results from the horizontal-to-vertical spectral ratio （HVSR） method, it shows that the HVSR method can reasonably estimate the site predominant frequency but underestimates the site amplification. The linear fitting between the average site amplification for each frequency band and the V20 （the average uppermost-20 m shear wave velocity） shows good correlation. A distance measurement called the asperity distance DAspt is proposed to reasonably characterize the source-to-site distance for large earthquakes. Finally, the inversed site response is used to identify the soil nonlinearity in the main shock and aftershocks of Wenchuan earthquake. In ten of the 28 stations analyzed in the main shock, the soil behaved nonlinearly, where the ground motion level is apparently beyond a threshold ofPGA 〉 300 cm/s^2 or PGV 〉 20 cm/s, and only one station coded 51SFB has evidence of soil nonlinear behavior in the aftershocks.

PREPARATION OF WATERBORNE ULTRAFINE PARTICLES OF EPOXY RESIN BY PHASE INVERSION TECHNIQUE

Waterborne ultrafine particles of epoxy resin were prepared by phase inversion technique. The results of SEM revealed that the particles diameter was in the range of 50 to 100 nm and the effects on amount of water required at phase inversion point were also discussed.

A two-step multi-frequency receiver function inversion method for shallow crustal S-wave velocity structure and its application across the basin-mountain range belts in Northeast China

A shallow crustal velocity structure(above 10 km depth) is essential for understanding the crustal structures and deformation and assessing the exploration prospect of natural resources, and also provides priori information for imaging deeper crustal and mantle structure. Passive-source seismic methods are cost-effective and advantageous for regional-scale imaging of shallow crustal structures compared to active-source methods. Among these passive methods, techniques utilizing receiver function waveforms and/or body-wave amplitude ratios have recently gained prominence due to their relatively high spatial resolution. However, in basin regions, reverberations caused by near-surface unconsolidated sedimentary layers often introduce strong non-uniqueness and uncertainty, limiting the applicability of such methods. To address these challenges, we propose a two-step inversion method that uses multi-frequency P-RF waveforms and P-RF horizontal-to-vertical amplitude ratios. Synthetic tests indicate that our two-step inversion method can mitigate the non-uniqueness of the inversion and enhance the stability of the results. Applying this method to teleseismic data from a linear seismic array across the sedimentary basins in Northeast China, we obtain a high-resolution image of the shallow crustal S-wave velocity structure along the array. Our results reveal significant differences between the basins and mountains. The identification of low-velocity anomalies(<2.8 km s^(-1)) at depths less than 1.0 km beneath the Erlian Basin and less than 2.5 km beneath the Songliao Basin suggests the existence of sedimentary layers. Moreover, the high-velocity anomalies(~3.4–3.8 km s^(-1)) occurring at depths greater than 7 km in the Songliao Basin may reflect mafic intrusions emplaced during the Early Cretaceous. Velocity anomaly distribution in our imaging result is consistent with the location of the major faults, uplifts, and sedimentary depressions, as well as active-source seismic results. This application further validates the effectiveness of our method in constraining the depth-dependent characteristics of the S-wave velocity in basins with unconsolidated sedimentary cover.

Study of Spectral Response Characteristics of Oilseed Rape (Brassica napus) to Particulate Matters Based on Hyper-Spectral Technique

Haze is mainly caused by the suspended particulate matters in the air,of which the particulate matters pollution harms leaf vegetables.In this paper,oilseed rapes at four different growing periods were investigated in a simulated particulate pollution environment.In combination of hyper-spectral technology and micro examination,the response of hyper-spectral characteristics of the leaf to particulate matters was investigated in-depth.The hyperspectral,chlorophyll content,net photosynthetic rate and stomatal conductance of leaf were obtained.The deposition and adsorption of particulate matters on the leaf were observed by Environmental Scanning Electron Microscope(ESEM).Normalized difference vegetation index(NDVI),modified red edge normalized(mNDVI705)and modified red edge simple ratio index(mSR705)were selected as characteristic parameters and the range of 510 nm~620 nm as the sensitive band.16 methods were used to establish the physiological information inversion model.The main results were as follows:Under the influence of particulate matters,the spectral reflectance decreased as a whole.With the increase of leaf age,the phenomenon of blue shift aggravated.The amplitude of yellow and blue edge decreased with overall decreasing vegetation indices.The furrows and irregular band protrusions in leaves were favorable for keeping particulate matters.With longer affecting time and more deposition of particle matters on the leaf,the stomatal opening became smaller.After comparing,principal component regression(PCR)+multiple scatter correction(MSC)+second derivative(SD)+Savitzky-Golay smooth(SG),and partial least square(PLS)+multiple scatter correction(MSC)+first derivative(FD)+Savitzky-Golay smooth(SG)were determined the best method to establish the inversion model of chlorophyll content and net photosynthetic rate respectively.This study may bring novel ideas for the diagnosis and analysis of the physiological response of leaf vegetables under particulate matters pollution using hyper-spectral technology.

Simultaneous inversion of velocity distribution and interface positions

This paper deals with the simultaneous inversion of velocity distribution and interface positions in a laterally heterogeneous medium using seismic travel time data. Due to the application of variable step length and linear interpolation techniques (for both theoretical travel times and the partial derivative matrix), the computing speed is increased greatly. As compared with other domestic computing programs of this kind, it is five times or more faster than others. Besides reflected waves, the transmitted waves can also be used to form the partial derivative matrix of travel times with respect to interface positions. So this method can make full use of the information about interface positions contained in various transmitted waves and speed up the convergence rate. Digital tests and processing results of real data indicate the feasibility and effectiveness of the method and its program.

Study on T700/Cyanate/PS/Epoxy Composites with ex-situ Toughening Technique

Composites were prepared with polysulfone through ex-situ toughening technique. The dynamic parameters of cyanate/epoxy resin were studied by differential scanning calorimetric（DSC） analysis and dynamic mechanical analysis（DMA）. Microstructual toughening mechanism was studied through scanning electron microscopy（SEM）. The particle microstructure in interlaminar region of composites toughened through ex-situ toughening technique revealed that a reaction induced phase decomposition and phase inversion happened in the interlaminar region. The thermosetting particles were surrounded by the PS phase, which could signifi cantly improve the delamination resistance of composites. The compression after impact（CAI） can be signifi cantly improved from 180 MPa to 260 MPa by using ex-situ toughening while the mechanical properties are not affected.

3D Gravity Inversion with Correlation Image in Space Domain and Application to the Northern Sinai Peninsula

We present a 3D inversion method to recover density distribution from gravity data in space domain.Our method firstly employs 3D correlation image of the vertical gradient of gravity data as a starting model to generate a higher resolution image for inversion.The 3D density distribution is then obtained by inverting the correlation image of gravity data to fit the observed data based on classical inversion method of the steepest descent method.We also perform the effective equivalent storage and subdomain techniques in the starting model calculation,the forward modeling and the inversion procedures,which allow fast computation in space domain with reducing memory consumption but maintaining accuracy.The efficiency and stability of our method is demonstrated on two sets of synthetic data and one set of the Northern Sinai Peninsula gravity data.The inverted 3D density distributions show that high density bodies beneath Risan Aniza and low density bodies exist to the southeast of Risan Aniza at depths between 1~10 and 20 km,which may be originated from hot anomalies in the lower crust.The results show that our inversion method is useful for 3D quantitative interpretation.

结肠镜反转技术对右半结肠息肉检出率及诊断价值的研究

目的探讨结肠镜反转技术对右半结肠息肉的检出率及诊疗价值。方法选取2020年2月至2021年12月于萍乡市第三人民医院内科80例接受肠镜检查的患者作为研究对象,第一次均接受普通结肠镜检查,复查行结肠镜反转技术检查,以病理组织检查结果为金标准,分析两次检查结果并评估结肠镜反转技术的诊断价值。结果80例患者中,病理学检查右半结肠息肉35例,其中1枚息肉18例,2枚息肉9例,3枚息肉3例,4枚息肉5例;结肠镜反转技术检查准确率为95.00%(76/80),高于普通结肠镜检查的76.25%(61/80),差异有统计学意义(P<0.05)。结肠镜反转技术特异度、阳性预测值、阴性预测值均高于普通结肠镜检查,差异有统计学意义(P<0.05);两种检测方法灵敏度比较差异无统计学意义。结论结肠镜反转技术诊断右半结肠息肉价值高,可提高息肉检出率,减少误诊及漏诊,实现疾病早期发现及早治疗,对预防结直肠癌具有积极的临床意义。

Inverse Class-AB功率放大器线性度和效率分析

inverse Class-AB模式可以使功率放大器得到更好的性能,但是传统的教科书中并没有这种模式的理论分析因此有必要从理论上对inverse Class-AB模式进行分析。通过对输出波形傅里叶函数的研究可以得到最大输出电压摆幅以及计算最大功率。通过Volterra序列分析法以out-of-band抵消技术我们分析这种模式功率放大器的非线性。最后我们进行了大量的仿真以验证所提出的理论。

Modified hepatic left lateral lobe inversion in laparoscopic proximal gastrectomy: An analysis of 13 cases

BACKGROUND In laparoscopic proximal gastrectomy(LPG),the prolapse of the hepatic left lateral lobe near the lesser curvature and esophageal hiatus can obstruct the field of vision and operation.Therefore,it is necessary to retract or obstruct the hepatic left lateral lobe to ensure a clear field of vision.AIM To investigate the safety and clinical efficacy of the modified hepatic left lateral lobe inversion technique for LPG.METHODS A retrospective analysis was conducted on the clinical data of 13 consecutive patients with early-stage upper gastric adenocarcinoma or adenocarcinoma of the esophagogastric junction treated with LPG from January to December 2023 at the Department of Gastrointestinal Surgery,Second Affiliated Hospital of Fujian Medical University.The modified hepatic left lateral lobe inversion technique was used to expose the surgical field in all patients,and short-term outcomes were observed.RESULTS In all 13 patients,the modified hepatic left lateral lobe inversion technique was successful during surgery without the need for re-retraction or alteration of the liver traction method.There were no instances of esophageal hiatus occlusion,eliminating the need for forceps to assist in exposure.There was no occurrence of intraoperative hepatic hemorrhage,hepatic vein injury,or hepatic congestion.No postoperative digestive complications of Clavien-Dindo grade≥II occurred wi-thin 30 days after surgery,except for a single case of pulmonary infection.Some patients experienced increases in alanine aminotransferase and aspartate aminotransferase levels on the first day after surgery,which significantly decreased by the third day and returned to normal by the seventh day after surgery.CONCLUSION The modified hepatic left lateral lobe inversion technique has demonstrated satisfactory results,offering ad-vantages in terms of facilitating surgical procedures,reducing surgical trauma,and protecting the liver.

Quantitative Schlieren Image-Noise Reduction Using Inverse Process and Multi-Path Integration

This report deals with introducing two new techniques based on a novel concept of complex brightness gradient in quantitative schlieren images, “inverse process” and “multi-path integration” for image-noise reduction. Noise in schlieren images affects the projections (density thickness) images of computerized tomography (CT). One spot noise in the schlieren image appears in a line shape in the density thickness image. Noise effect like an infectious disease spreads from a noisy pixel to the next pixel in the direction of single-path integration. On the one hand, the noise in the schlieren image reduces the quality of the image and quantitative analysis and is undesirable;on the other it is unavoidable. Therefore, the importance of proper noise reduction techniques seems essential and tangible. In the present report, a novel technique “multi-path integration” is proposed for noise reduction in projections images of CT. Multi-path integration is required the schlieren brightness gradient in two orthogonal directions. The 20-directional quantitative schlieren optical system presents only images of schlieren brightness in the horizontal gradient and another 20-directional optical system seems necessary to obtain vertical schlieren brightness gradient, simultaneously. Using the “inverse process”, a new technique enables us to obtain vertical schlieren brightness gradient from horizontal experimental data without the necessity of a new optical system and can be used for obtaining any optional directions of schlieren brightness gradient.

人工智能辅助压缩感知技术结合三种T2WI压脂技术的应用研究

目的探讨人工智能辅助压缩感知技术(ACS)结合3种T2加权像(T2WI)压脂技术在图像质量、成像时间及方案选择方面的优势。方法对因腰痛行常规腰椎MRI平扫的30例患者,除了进行原有的检查序列外,再结合ACS加行5组矢状位(SAG)T2WI压脂序列,使用的3种T2WI压脂技术包括频率选择饱和法(FS)、水脂分离成像技术(WFI)及短反转时间的反转恢复技术(STIR),共包括ACS-SAG-T2WI-FS(A组,30例)、ACS-SAG-T2WIWFI(B组,30例)、ACS-SAG-STIR(C组,30例)、SAG-T2WI-FS(D组,30例)、SAG-T2WI-WFI(E组,30例)、SAG-STIR(F组,30例)6组序列。通过客观评价指标信噪比(SNR)、对比噪声比(CNR)等,以及脊柱疾病诊断经验丰富的2名放射科医师对图像质量的主观评价评估检查效果。结果A组第4椎体、第4~5椎间盘、同层脊髓的SNR、CNR大于D组;B组第4椎体、第4~5椎间盘、同层脊髓的SNR、CNR大于E组;C组第4椎体、第4~5椎间盘、同层脊髓的SNR、CNR大于F组(P均<0.01)。从成像时间看,A组比D组节省13.2%的时间,B组比E组节省8.9%的时间,C组比F组节省12.4%的时间(P均<0.01)。2名放射科医师对A、B、C组的主观评价均高于D、E、F组(P均<0.01;2名医师评分具有一致性,Kappa=0.972、P<0.01)。结论ACS结合3种T2WI压脂技术在时间、质量上均优于单纯使用3种T2WI压脂技术。其中ACS-SAG-T2WI-FS成像时间最短,图像质量最好,为首选方法;ACS-SAG-T2WI-WFI能提供多期图像,时间优势差为次选;ACS-SAG-STIR有最稳定的压脂能力,可作为最后的选择。

声表面波混频谐波的实验观察

基于超声无损检测技术的需要,该文在理论分析声表面波混频效应的基础上,提出了一种混频声表面波的激发方法,并进行了相应的声表面波混频谐波的实验观察研究。设计并制作了以斜入射的体横波和体纵波分别激发声表面波的楔块,通过选择适当的体横、纵波激励信号的周波数及时间延迟,可使斜入射体横、纵波分别激发的声表面波完全混叠。通过对接收到的混叠声表面波时域信号进行脉冲反相处理和傅里叶变换,得到明显的声表面波混频谐波信号。结果表明,借助于楔块两列斜入射的体横、纵波可有效产生混频声表面波,实验观察与理论预期一致,这为发展基于混频声表面波的超声无损检测技术奠定了基础。

基于纳米孔隙弹性理论的页岩气储层地震弹性反演方法

页岩中的有机质干酪根广泛发育大量纳米级别的孔隙,这些孔隙具有极大的表面-体积比,孔隙表面会产生明显的表面效应,从而对页岩整体弹性性质产生影响.在对页岩进行储层预测时,考虑纳米孔隙的影响是十分必要的.现有的AVO技术以经典弹性理论为基础,通常可以预测页岩储层的纵横波速度、弹性模量和密度等,但往往忽略了纳米孔隙的表面效应.结合纳米孔隙弹性理论和AVO技术,将表征纳米孔表面效应的参数(表面弹性模量、纳米孔径)耦合到反射系数近似公式中,提出了一种新的AVO参数化表征方法,直接体现了纳米孔隙相关参数对反射系数的响应特征.新方法中包含3个待反演参数:基质剪切模量、纳米孔隙相关参数和密度.基于平滑背景约束的贝叶斯反演策略,利用测井的模型试验和实际地震数据验证了所提方法的可行性和适用性,实现了对页岩纳米孔隙相关属性的定量预测.通过定量关系转换,创建了一种用以描述页岩含气能力的指示因子.本文提出的方法为预测页岩气储层弹性性质提供了一种新的思路.

长白山天池火山2015—2022年InSAR变形与活动状态分析

地表形变信息可有效反映火山下岩浆房的活动状态,对于理解火山活动演化过程非常重要。文中利用Sentinel-1A/B的升、降轨影像,采用SBAS InSAR与Stacking InSAR技术,获取了长白山天池火山2015—2022年间的地表形变时间序列及速率,并结合Mogi点源模型反演岩浆房的几何参数,得到的主要结论如下:(1)火山口及周围区域整体下沉,火山口附近视线向形变速率约为-4~-2mm/a,远离火山口的局部形变速率可达-6mm/a。(2)根据Mogi模型反演的火山下浅层岩浆房深约6km,体积变化率为-3.3×10^(5)m^(3)/a,岩浆房位于长白山天池火山口下偏西的位置。(3)1992—2022年期间,火山经历了从平静到扰动、再到平静的岩浆活动过程,在2002—2005年监测到明显的地表隆升变形,岩浆房体积显著膨胀,之后岩浆的活动性逐渐减弱。

A general alternate loading technique and its applications in the inverse designs of centrifugal and mixed-flow pump impellers

For the inverse designs of centrifugal and mixed-flow pump impellers,clarifying the generation process of secondary flows and putting forward corresponding suppression measures is an important approach to improve the impeller performance.In this paper,to provide a better qualitative insight into the generation mechanism of secondary flows in the impeller,a simple kinematic equation is derived based on the ideal assumptions,which indicates that the potential rothalpy gradient(PRG)is the most important dynamic source that actively induces secondary vortical flows.Induced by the natural adverse PRG on the S1 and S2 stream surfaces,two typical secondary flows,H-S and P-S secondary flows,are clearly presented.To specially suppress these typical secondary flows,a general alternate loading technique(GALT)is proposed,aiming to adjust the real blade loadingδp to control the PRG features.At the blade fore part,theδp on the hub streamline should be slowly increased to avoid breakneck growth of the potential rothalpy to reduce adverse streamwise PRG on the S2 streamsurface.At the blade middle part,theδp should be moderately decreased to reduce adverse streamwise PRG on the S1 streamsurface.At the blade aft part,the difference in theδp between the shroud and hub streamlines should be decreased faster to control the exit uniformity.By applying the GALT to the impeller designs of three typical pump types in hydraulic engineering,the organizational effect of the PRG on fundamental flow structures is proven.The GALT can effectively control the PRG distributions and suppress the secondary flows,thereby widening the pump’s high-efficiency zone,improving flow uniformity and suppressing pressure fluctuations.Compared with the current Z-G method and the ALT,the GALT can meet the requirements of"de-experience"better,thereby enabling the designers to obtain good products explicitly and quickly.

基于BSA-BP神经网络方法的引水隧洞围岩参数反演模型及应用

针对地下工程围岩参数取值,提出将回溯搜索优化算法(BSA)与BP神经网络相结合的混合网络(BSA-BP)方法,对隧道围岩参数进行反演研究。通过建立隧道有限元开挖模型,利用反演参数计算监测断面的位移并与现场实测值进行对比,最终对围岩稳定性进行分析预测。结果表明,经BSA算法优化的BP神经网络相对于GA-BP神经网络,具有更快的反演速度与计算效率。利用BSA-BP神经网络反演参数得到的位移计算值与现场实测值相对误差均在5%以内,表明该模型具有较高的反演精度,合理可行,为地下工程参数反演提供了一种新方法。

C/X双频双圆极化共口径微带天线设计

设计实现了一款C/X双频双圆极化共口径微带天线,在C/X频段均能以双圆极化方式工作,有效提高了天线的口径利用率。采用寄生结构和L型探针耦合馈电拓展了天线的阻抗带宽;以嵌套方式将X波段天线置于C波段天线的间隙处实现了共口径设计;通过对称反相馈电技术实现了良好的交叉极化比。测试结果表明,C波段的阻抗带宽和3 dB轴比带宽分别大于23%和17%;X波段的阻抗带宽和3 dB轴比带宽分别大于28%和18%;测试频点处的交叉极化比均大于25 dB。

小样本矿物高光谱数据增强与丰度反演

为了解决基于深度学习的开展矿物高光谱丰度反演研究中标签数据不足的问题,提出一种基于添加填充系数的Hapke混合模型的小样本矿物高光谱数据增强方法,用于生成大量带标签的数据集。在实验室内选择5种常见矿物按照质量比例对矿物粉末进行多元混合,并对混合矿物开展光谱量测。基于线性混合模型、Hapke混合模型、填充系数分别为0.1,0.2和0.3的Hapke混合模型共5种模型,按照对应的质量比例生成模拟的混合矿物光谱,与实验室实测光谱进行比较。最后,基于Monte Carlo法随机生成多元“和为一”的丰度矩阵,利用5种混合模型开展数据增强,分别生成40000条模拟光谱作为堆栈自编码网络的训练集,反演矿物高光谱数据的丰度信息。研究结果表明:Hapke模型以及添加填充系数后的光谱模拟精度均优于线性混合模型的模拟精度,当Hapke模型的填充系数为0.1和0.2时,光谱角距离误差均值分别为0.0535和0.0537,模拟的矿物光谱更接近实测光谱,且优于未添加填充系数时的光谱角距离误差0.0748。利用填充系数为0.1和0.2的Hapke模型生成的模拟数据作为深度学习训练集,矿物高光谱丰度反演的均方根误差(RMSE)为0.1248,优于其他4种模型的反演结果。基于添加填充系数后的Hapke混合模型生成的模拟数据更接近真实光谱,可为深度学习的小样本矿物丰度反演研究提供数据支撑。