High Resolution in Seismic Refraction Tomography for Environmental Study

Seismic refraction tomography (SRT) involves more complex mathematic algorithms to fit more flexible model. In the field procedure SRT in generally needs more shot points than standard seismic refraction survey to obtain high resolution profile. In this seismic refraction study, we have used 9 shot-points for inline and 10 shot-points for offset in purpose to obtaine high resolution of seismic refraction tomography. During a recent geophysical test site, the subsurface material was mapped along survey line using seismic refraction method. Analyses of the site investigation data revealed that the studied site was made up of two layers of the subsurface. The upper layer has velocity values with range of 500 m/s to1500 m/s which can be classified as unconsolidated surface deposits and mixtures of unsaturated sands and gravels. Meanwhile the lower layer has velocity values with range of2000 m/s to5500 m/s which is classified as compacted fine’s soil due to high pressure of the overburden. Analysis of seismic refraction data demonstrated that refraction tomography software systems are able to reveal subsurface material which represented by their seismic velocity value. Furthermore, the velocity model obtained in this study is agreed with its synthetic modelling result as initial model. This validity and reasonable results was able to assist in interpretation of the seismic refraction method for the environmental study.

Investigating the Depth and the Geometry of the Quarzitic Panafrican Basement Using Near-Surface 3D Seismic Refraction Tomography: Case Study of the Locality of Bakel (Senegal)

Seismic refraction investigations have been carried out in Bakel, Eastern Senegal. The purpose was to map geometrical relationship between the existing rock types and the Panafrican quarzitic basement, which is valuable information for the project of the Bakel fluviatile port construction. Four seismic refraction profiles were acquired. The obtained data have been processed by inversion. The obtained four seismic P-wave velocity profiles have been integrated to obtain a 3D model. By comparing the outcropping geological formations with the observed seismic data at the surface, it was possible to identify the lithology corresponding to each measured range of seismic velocity for the alluvium, the weathered bed rock, and the fresh rock. The results showed that the depth of the fresh rock of the basement varies from 0 to 18 meters above the sea level, with a deepening toward the Senegal River and toward the Northern part of the studied area. The presence of alluviums and their thickness are linked to the existence of bays and gulfs. The results of this study give valuable information for the river bed dredging cost assessment prior to the port construction phase.

Soil and Subsurface Sediment Microzonation Using with Seismic Refraction Tomography for Site Assessment (Case Study: IKIA Airport, Iran)

The site effects relating to the amplification of ground motion under earthquake loading are strongly influenced by both the subsurface soil condition and the geologic structure. In this study, for site characterization at the Imam Khomeini International Airport (IKIA) area in south of Tehran, in-situ seismic refraction tomography were carried out as a part of site investigations project, in addition geologic setting, borehole drilling, ground waters information and measurements. Based on seismic refraction studies, three layers are separable which with increasing in depth the S and P wave velocity is increased and this indicates increasing in compaction of soil and geologic materials. In the second and third separated layers, the zones with low and high seismic shear wave velocity is approximately equal, and northeast and southwest of the airport site has the low velocities, in addition to containing loose soils, highly weathered stones, and low depth to groundwater. In terms of Poisson’s ratio, the most important and key installations of airport site are located in suitable positions. According to Iranian Seismic Code, most of the lands around the airport are in class 2 and 3. It seems that a fault or a discontinuity is passed from northwest to the southeast of the study area. This site, according to geological, subsurface geophysical, and geotechnical boreholes studies, is high risk-earthquake prone.

Wet Refractivity Tomography with an Improved Kalman-Filter Method

An improved retrieval method, which uses the solution with a Gaussian constraint as the initial state variables for the Kalman Filtering （KF） method, was developed to retrieve the wet refractivity profiles from slant wet delays （SWD） extracted by the double-differenced （DD） GPS method. The accuracy of the GPS-derived SWDs is also tested in this study against the measurements of a water vapor radiometer （WVR） and a weather model. It is concluded that the GPS-derived SWDs have similar accuracy to those measured with WVR and are much higher in quality than those derived from the weather model used. The developed method is used to retrieve the 3D wet refractivity distribution in the Hong Kong region. The retrieved profiles agree well with the radiosonde observations, with a difference of about 4 mm km^- 1 in the low levels. The accurate profiles obtained with this method are applicable in a number of meteorological applications.

Tropospheric Wet Refractivity Tomography Based on the BeiDou Satellite System

This paper presents a novel approach for assessing the precision of the wet refractivity field using BDS （BeiDou navigation satellite system） simulations only,GPS,and BDS＋GPS for the Shenzhen and Hongkong GNSS network.The simulations are carried out by adding artificial noise to a real observation dataset.Instead of using the δ and σ parameters computed from slant wet delay,as in previous studies,we employ the Bias and RMS parameters,computed from the tomography results of total voxels,in order to obtain a more direct and comprehensive evaluation of the precision of the refractivity field determination.The results show that：（1） the precision of tropospheric wet refractivity estimated using BDS alone （only 9 satellites used） is basically comparable to that of GPS; （2） BDS＋GPS （as of current operation） may not be able to significantly improve the data＇s spatial density for the application of refractivity tomography; and （3） any slight increase in the precision of refractivity tomography,particularly in the lower atmosphere,bears great significance for any applications dependent on the Chinese operational meteorological service.

层析+折射约束迭代反演近地表建模方法及应用探索

塔西南山前带是塔里木盆地重要的勘探接替领域之一,其地表为巨厚黄土覆盖,黄土厚度可达500 m以上,速度在纵、横向上变化快,表层结构复杂。为改善地震成像效果,针对复杂地表区表层模型精度难以满足需求的问题,开展了拟合时深曲线量板、层析反演及折射反演等方面研究工作。结果表明:多种表层建模方法综合运用是提高近地表模型精度的有效途径;黄土曲线量板可反映连续介质区近地表速度变化规律;层析+折射约束迭代反演近地表建模方法能够将模型精度误差控制在5%以内;逐级递进约束层析反演可拓展可信速度场深度约1500 m。以上成果认识,对类似探区构建高精度近地表模型及提高地震成像精度具有指导意义。

SS-OCT在角膜成像中的应用进展

成像技术的进步彻底改变了眼科领域,改变了我们对眼科疾病的理解、诊断和治疗。扫频源光学相干断层扫描(SS-OCT)是一种最新的非接触式高分辨率成像技术。它进一步提高了成像深度和扫描速度,增加了新的算法和功能。SS-OCT允许对角膜结构进行三维评估,提供角膜前、后表面的曲率和高度图以及角膜厚度图。这可以帮助眼科医生筛查和诊断角膜病变,如圆锥角膜、角膜营养不良和变性。SS-OCT更快、更精准和更灵敏的角膜测量有助于对即将进行角膜和屈光手术的患者做好术前计划和术后监测。文章总结SS-OCT技术的发展及其在角膜疾病中潜在的临床效用与在手术中的应用进展,以支持更多未来可能的研究和临床治疗。

低中度近视儿童青少年周边视网膜离焦状态及其影响因素分析

目的探讨低中度近视儿童青少年周边视网膜离焦状态及其影响因素。方法横断面研究。281例6~15周岁双眼近视儿童青少年纳入研究,仅选择右眼数据分析。进行睫状肌麻痹验光及眼轴长度(AL)、平均角膜曲率(AveK)测量后,按照等效球镜度(SE)分为低度近视(LM)组(-3.00 D≤SE≤-0.50 D)和中度近视(MM)组(-6.00 D≤SE<-3.00 D);根据AL[AL1组(23.00 mm≤AL≤24.00 mm)]、AL2组(24.00 mm0.05)外,TRDV、RDV-30、RDV-45、RDV-15-30、RDV-30-45、RDV-45-53、RDV-S、RDV-I、RDV-N均显著正向增加(均为P<0.05)。根据AL和AveK分组比较结果显示,AL2组患者TRDV、RDV-30、RDV-45、RDV-15-30、RDV-30-45、RDV-45-53、RDV-S、RDV-I、RDV-N均显著高于AL1组(均为P<0.05);AL3组患者TRDV、RDV-30、RDV-45、RDV-15-30、RDV-30-45、RDV-45-53、RDV-S、RDV-N均显著高于AL2组和AL1组,RDV-I、RDV-T均显著高于AL1组(均为P<0.05);AveK1组患者TRDV、RDV-30、RDV-45、RDV-15-30、RDV-30-45、RDV-45-53、RDV-S、RDV-I均显著高于AveK2组(均为P<0.05)。相关性分析结果显示,TRDV、RDV-45、RDV-30-45、RDV-45-53、RDV-S、RDV-N与年龄和AL均存在正相关,与SE和AveK均存在负相关;RDV-30、RDV-15-30、RDV-I与AL均存在正相关,与SE、AveK均存在负相关;RDV-T仅与AL存在正相关;RDV-15与年龄、SE、AL、AveK均不存在相关性。多元线性回归分析结果显示,年龄是RDV-45-53、RDV-S的影响因素;AL是TRDV、RDV-30、RDV-45、RDV-15-30、RDV-30-45、RDV-45-53、RDV-S、RDV-T的影响因素;AveK是RDV-I的影响因素;SE对各范围RDV均不存在显著影响。结论低中度近视儿童青少年周边视网膜离焦已基本达到远视离焦状态,其中AL相对较短的患者远视离焦量最少。在年龄、SE、AL、AveK四种因素中,年龄、AL和AveK均能影响低中度近视儿童青少年周边视网膜离焦,而AL是最重要的影响因素。

基于光学相干断层扫描血管成像术探讨Eye-TEAS防治儿童近视疗效及作用机制

目的:基于光学相干断层扫描血管成像术(OCTA)探讨眼周经皮穴位电刺激仪(Eye-TEAS)防治儿童近视的疗效和机制。方法:纳入60名近视儿童,记录黄斑中心凹下脉络膜厚度(SFCT)等眼部各参数水平,并对各参数进行相关性分析;采用Eye-TEAS对受试者进行3个月的干预治疗,每天30 min,每周使用不低于5次。检测Eye-TEAS干预前、干预1次后、干预1个月后、干预3个月后受试者等效屈光度(SER)、眼轴长度(AL)、SFCT及黄斑区3 mm×3 mm面积内的脉络膜中大血管密度(CVD)、脉络膜毛细血管密度(CCVD)的变化情况。结果:58名近视儿童完成了干预及随访,在基线数据观察中,SER与SFCT、CCVD均呈显著正相关(P<0.01),AL与SER、SFCT、CVD、CCVD呈显著负相关(P<0.05或P<0.01)。相较于干预前,干预第1次后、1个月后、3个月后SER、AL均未发生显著变化(P>0.05)。干预第1次后SFCT与基线水平比较,差异无统计学意义(P>0.05)。干预1个月、3个月后SFCT与基线水平比较,差异均有统计学意义(P<0.05),其中干预1个月后SER变化和SFCT变化呈显著正相关(P<0.05)。在干预第1次、干预1个月后CVD较基线水平增加(P<0.05),但干预3个月后CVD与基线水平比较,差异无统计学意义(P>0.05)。相较于基线数据,干预1个月后和干预3个月后CCVD均显著升高(P<0.01)。结论:近视儿童SFCT、眼底微循环情况与AL、SER具有高度相关性;Eye-TEAS干预后SFCT显著增厚,CVD、CCVD也显著增加,这可能与Eye-TEAS通过影响脉络膜血流的变化减缓近视的进展有关。

基于声学层析成像的温度场和流速场重构

为有效重构三维管道内液体的温度场和流速场,提出了一种超声飞渡时间计算表征,并基于此求解温度场和流速场反演模型。同时考虑温度梯度导致的声线弯曲效应,采用正四面体前向展开法,追踪超声弯曲路径;开展“华龙一号”反应堆主管道冷却剂温度场和流速场重构实验。实验结果表明,所提方法能有效重构管道冷却剂温度场和流速场,且考虑弯曲效应能进一步提高重构精度。

Direct and real-time sub-wavelength resolution photoacoustic imaging method based on acoustic lens with negative refractive index

The signal processing technology based on material with negative refractive index provides researchers with the latest ideas. As a new nondestructive bio-photonic technology, photoacoustic tomography is a kind of imaging method based on the differences of optical absorption within the biological organization However, photoacoustic tomography by the scanning sensor or by the sensors array at present has its inherent disadvantages that may lead to poor real-time performance and high cost in the imaging process. The characteristics of acoustic lens with negative refractive index such as focusing, filtering and directional control on acoustic wave, are very suitable for solving the problem in photoacoustic tomography. With an analysis on the nega-tive quality response of acoustic lens and the advantages of negative refractive imaging, we proposed an approach using the lens to change the current photoacoustic imaging methods. The experiment showed that the imaging effectiveness of photoacoustic tomography by the designed lens is very impressive that the pressure distribution of the absorber is basically consistent with the image of the absorber. In addition, the result of 0. 6 times wavelength in the experimental image is demonstrated on sub-wave-length photoacoustic imaging through the lens designed in this work.

Principle of diffraction enhanced imaging (DEI) and computed tomography based on DEI method

In the first part of this article a more general DEI equation was derived using simple concepts. Not only does the new DEI equation explain all the problems that can be done by the DEI equation proposed by Chapman, but also explains the problem that can not be explained with the old DEI equation, such as the noise background caused by the small angle scattering reflected by the analyzer. In the second part, a DEI-PI-CT formula has been proposed and the contour contrast caused by the extinction of refraction beam has been qualitatively explained, and then based on the work of Ando's group two formulae of refraction CT with DEI method has been proposed. Combining one refraction CT formula proposed by Dilmanian with the two refraction CT formulae proposed by us, the whole framework of CT algorithm can be made to reconstruct three components of the gradient of refractive index.

Image Distortion of Optical Coherence Tomography

A kind of image distortion in Optical Coherence Tomography (OCT) resulted from average refractive index changes between structures of bio tissue is discussed for the first time.Analysis is given on following situations:1) Exact refraction index changes between microstructures;2)The gradient of average refractive index change between different tissue layers is parallel to the probe beam;3) The gradient of average refractive index change is vertical to the probe beam.The results show that the image distortion of situation 1) is usually negligible;in situation 2) there is a spread or shrink effect without relative location error; however,in situation 3) there is a significant image error inducing relative location displacement between different structures.Preliminary design to eliminate the distortion is presented,the method of which mainly based on the image classification and pixel array re arrangement.

OPTICAL COHER ENCE TOMOGRAPHY OF ADIPOSE TISSUE AT PHOTODYNAMIC/PHOTOTHERMAL TRE ATMENT IN VITRO

Temporal changes in structure and refractive index distribution of adipose tissue at photo-dynamic/photothermal treatment were studied with OCT in vitro.Ethanol-water solutions of indocyanine green(ICG)and brilliant green(BG)were used for fat tissue staining.CW laser diode(808 nm)and LED light source(442 and 597 nm)were used for ir adiation of stained tissue slices.The data received supporting the hypothesis that photodynamic/photothermal treatment,induces fat cell lipolysis during a certain period of time after light exposure.

Ocular image-based deep learning for predicting refractive error:A systematic review

ackground:Uncorrected refractive error is a major cause of vision impairment worldwide and its increasing prevalent necessitates effective screening and management strategies.Meanwhile,deep learning,a subset of Artificial Intelligence,has significantly advanced ophthalmological diagnostics by automating tasks that required extensive clinical expertise.Although recent studies have investigated the use of deep learning models for refractive power detection through various imaging techniques,a comprehensive systematic review on this topic is has yet be done.This review aims to summarise and evaluate the performance of ocular image-based deep learning models in predicting refractive errors.Main text:We search on three databases(PubMed,Scopus,Web of Science)up till June 2023,focusing on deep learning applications in detecting refractive error from ocular images.We included studies that had reported refractive error outcomes,regardless of publication years.We systematically extracted and evaluated the continuous outcomes(sphere,SE,cylinder)and categorical outcomes(myopia),ground truth measurements,ocular imaging modalities,deep learning models,and performance metrics,adhering to PRISMA guidelines.Nine studies were identified and categorised into three groups:retinal photo-based(n=5),OCT-based(n=1),and external ocular photo-based(n=3).For high myopia prediction,retinal photo-based models achieved AUC between 0.91 and 0.98,sensitivity levels between 85.10%and 97.80%,and specificity levels between 76.40%and 94.50%.For continuous prediction,retinal photo-based models reported MAE ranging from 0.31D to 2.19D,and R^(2) between 0.05 and 0.96.The OCT-based model achieved an AUC of 0.79–0.81,sensitivity of 82.30%and 87.20%and specificity of 61.70%–68.90%.For external ocular photo-based models,the AUC ranged from 0.91 to 0.99,sensitivity of 81.13%–84.00%and specificity of 74.00%–86.42%,MAE ranges from 0.07D to 0.18D and accuracy ranges from 81.60%to 96.70%.The reported papers collectively showed promising performances,in particular the retinal photo-based and external eye photo-based DL models.Conclusions:The integration of deep learning model and ocular imaging for refractive error detection appear promising.However,their real-world clinical utility in current screening workflow have yet been evaluated and would require thoughtful consideration in design and implementation.

综合地球物理方法在隧道勘察中的应用

为解决隧道工程中断层破碎带探测、岩土工程质量评价难题,以贵池区公共矿产品运输廊道建设项目C1-01号隧道为研究对象,综合应用高密度电法、地震折射层析成像、声波沉井等方法,对隧道纵断面、出洞口、入洞口和洞身段进行数据观测,研究断层破碎带的分布和岩体工程质量。结果表明,隧洞洞身段共圈定4处断裂构造异常,编号依次为F1、F2、F3及F4;在隧洞洞身段里程K1+000~K1+090的上部区域,圈定一条低电阻率-低速度值综合异常反映的不规则条带状异常,解译为浅部采空区或基岩破碎的反映;隧洞入口处和出口处浅部围岩的纵波速度在200~1 000 m/s;洞身纵波速度值在2.16~3.93 km/s之间变化,Vp速度值整体变化平稳。

几种静校正方法的比较研究

为解决近地表速度异常和地形起伏引起的静校正问题,已出现了多种静校正方法,这常常使资料处理人员无所适从。这里从众多的静校正方法中选择了三个具有代表性的,在生产中用得较多的方法(折射静校正、无射线追踪层析静校正、非线性层析静校正),从方法原理、方法特点、实际应用效果等方面进行了比较研究,最后给出了针对不同目标选择适当静校正方法的建议,以帮助资料处理人员在实际资料处理中,有针对性地选择静校正方法,快速有效地完成资料处理任务,提高处理质量。

白内障手术后角膜屈光动态变化的研究

目的 评价白内障手术不同切口造成角膜屈光的动态变化。方法 随机选取白内障囊外摘出术（ECCE）组26例30眼,白内障超声乳化术（Phaco）组21例27眼,应用ORBSCAN裂隙光扫描角膜层面照相/测厚系统,于术前和术后 3天;1、2周;1、2、3个月对术眼角膜进行检测,比较分析术后角膜屈光的变化情况。结果 ECCE组、Phaco组术后角膜总平均屈光力变化不明显（P>0.05）,3天～1周主要受角膜厚度影响（P<0.05）;两组术后1个月角膜总合散光分别为3.95D±2.97D和1.89D±0.30D,差异有显著性（P<0.05）;两组角膜散光与手术时间呈二次抛物线回归关系,ECCE组在术后1个月出现散光骤变（P<0.05）,但两组角膜散光均于术后3个月趋向稳定（P>0.05）。结论白内障手术后角膜屈光存在动态变化。ORBSCAN通过检测角膜前后表面曲率。角膜厚度,比较真实地反映角膜形态学的改变。

川东北复杂山地三维静校正应用及实例分析

川东北复杂山地由于地表高程变化大、风化层厚度不均匀、低降速带速度横向变化大、高速层底界不稳定等因素,得到的地震资料具有严重的静校正问题,因此,如何解决山地静校正问题是后续地震资料处理的关键之一,本文首先分析高程静校正、折射静校正、层析静校正的基本原理和适用条件,结合实际复杂山地三维地震资料的特点,进行试验对比,提出了进行山地静校正的基本思路,即:首先进行高程静校正,这样可以利用高程静校正更容易拾取初至时间,然后利用折射静校正结合微测井等资料建立近地表速度-深度模型,以此速度-深度模型作为层析静校正的初始模型进行迭代处理,最后得到最终的近地表速度-深度模型和静校正值.根据以上处理流程,我们建立了适合于川东北山地三维复杂地表地震资料的静校处理正方法,并在实际生产过程中取得了良好的效果.

高度近视眼黄斑区视网膜厚度与视力损害的关系

背景部分高度近视患者在出现眼部并发症的形态改变之前就可表现为视功能的改变，黄斑区视网膜厚度的改变与其是否相关尚不清楚。目的探讨高度近视眼视网膜厚度与视力损害的关系。方法采用连续病例观察研究设计。选取2011年1月至2012年1月在北京同仁医院眼科中心接受准分子激光角膜原位磨镶术（LASIK）的高度近视患者132例245眼，近视等效球镜为一6．00—一20．00D。所有患者均接受最佳矫正视力（BCVA）和傅里叶域光学相干断层扫描仪（FD—OCT）检查，扫描模式为黄斑MM6。所有受检眼根据矫正视力的不同分为矫正视力≥0．9组和矫正视力≤O．8组；根据有无后巩膜葡萄肿将人选眼亚分为无后巩膜葡萄肿组及后巩膜葡萄肿组，后巩膜葡萄肿组再根据OCT图像上后巩膜葡萄肿的形态亚分为黄斑对称组及黄斑倾斜组。利用OCT随机软件生成的视网膜厚度图获取各组患者黄斑区不同象限视网膜厚度的平均值，比较不同视力组间和不同形态后巩膜葡萄肿间黄斑区视网膜厚度的差异。结果不同视力组间和各亚组间受检者的人口基线特征匹配。矫正视力≥0．9组BCVA为1．02±0．16，矫正视力≤0．8组为0．62~0．08，差异有统计学意义（t=3．233，P=0．001）；矫正视力≥0．9组黄斑中心凹区视网膜厚度为（256．28±13．19）斗m，明显较矫正视力≤0．8组的（231．17±10．96）斗m厚，差异有统计学意义（t=2．134，P=0．031）。无后巩膜葡萄肿组及后巩膜葡萄肿I组、Ⅱ组间BCVA分别为1．00~0．27、0．78±O．21和0．90~0．13，3个组间差异有统计学意义（F=15．760，P=0．015），无后巩膜葡萄肿组及后巩膜葡萄肿Ⅱ组患者BCVA均高于后巩膜葡萄肿I组，差异均有统计学意义（q=16．131，P=0．006；q=一10．831，P=0．008）；3个组间黄斑中心凹区平均视网膜厚度值的差异有统计学意义（F=2．316，P=0．025），后巩膜葡萄肿I组患者视网膜厚度为（234．21±15．69）Ixm，明显低于无后巩膜葡萄肿组的（252．25±15．31）斗m，差异有统计学意义（q=12．977，P=0．023）；3个组黄斑旁中心凹区视网膜厚度值的差异无统计学意义（F=0．318，P=0．078）；3个组间黄斑周边区视网膜厚度的差异有统计学意义（F=1．925，P=0．013），后巩膜葡萄肿Ⅱ组视网膜厚度值为（273．26±16．37）斗m，与后巩膜葡萄肿I组患者的（289．11±19．30）txm及无后巩膜葡萄肿组的（290．33±17．12）斗m比较明显下降，差异均有统计学意义（g=一8．305，P=0．023；g=-7．011，P=0．012）。结论高度近视眼黄斑中心凹区视网膜厚度的改变与BCVA损害有关，后巩膜葡萄肿的后顶点对应处视网膜变薄累及黄斑中心凹时会导致视力下降。