数字化ECT成像系统

基于电容敏感原理设计的数字化电容层析成像系统,利用有限元法,分析了阵列电极结构对敏感场分布的影响,通过优化设计和仿真试验,改善了敏感场分布的均匀性;构建了以DSP为核心、FPGA协同工作的12电极的数字化ECT系统,提出了由离线预迭代和在线一步成像所构成的新的图像重建算法——预迭代法,其成像速度及精度均明显提高．     

电磁波CT揭露重大工程岩溶发育特征--以某地铁岩溶勘察为例

灰岩地区岩溶发育程度严重影响重大工程建设,以钻探为主的城市岩溶勘察,很难充分查明地下岩溶发育特征及规模,而高密度电法、浅层地震反射等其余地球物理方法因场地条件限制和干扰因素较多,在城市岩溶探测中很难实施。鉴于此,本文采用井间电磁波CT层析技术对某地铁进行岩溶探测,应用联合迭代重建技术（simultaneous iterative reconstruction technique 简称SIRT）进行反演,获取电磁波CT吸收系数等值线图,并通过吸收系数判断岩溶发育状态。研究结果表明：电磁波CT层析技术可较好揭露地下岩溶发育规模和特征,探测结果与钻孔资料揭露岩溶信息高度吻合。该方法的成功引入为重大工程岩溶探测提供了新思路,其探测成果结合钻孔信息可作为重大工程建设可靠的地质参考依据,具有较好的科学意义和推广价值。     

AM ultrasound-modulated optical tomography with realtime FFT

We report on a novel ultrasound-modulated optical tomographic technique applied in dense tissue-simulating turbid media. A 1 MHz ultrasound beam is focused into the media to modulate and tag the scattering laser light passing through the ultrasonic focused zone. A 10 kHz sinusoidal wave, as a detection wave, is carried by the ultrasound beam through amplitude-modulation (AM). The scattering photons that come from the focused zone carry the modulated information, received by detector and demodulated by real-time fast Fourier transform (FFT). The optical tomographic images of the tissue simulating media and buried object are reconstructed with AM spectral intensity. This method can be applied to imaging three-dimensional tissue structures with different optical parameters. For the first time, we obtained the tomography of buried objects in biological tissue phantoms with a detecting depth of 30 mm.     

电阻抗CT技术在人体上肢图象重建中的应用

人体实验是电阻抗ＣＴ技术应用于临床的重要研究课题之一。在研制了适用于人体上肢的环状无源３２－电极系统的基础之上,对不同受试者的上臂和前臂作了多组测试工作。文中给出了电阻抗ＣＴ逆问题计算的数学模型和人体实验的结果。结果表明：经过图象重建和处理后,基本符合人体上肢的解剖学特征,可以清晰地分辨出骨骼与肌肉组织。     

94例肺癌CT征象分析

目的：探讨肺鳞癌、肺腺癌的ＣＴ鉴别要点。方法：对５１例肺鳞癌及４３例肺腺癌的ＣＴ表现进行回顾性分析。结果：鳞癌７０．６％为中央型,２９．４％为周围型;腺癌４．７％为中央型,９５．３％为周围型。１５例周围型肺鳞癌均表现为肿块,而４１例周围型肺腺癌中,５例为局灶性实变,３例为两肺弥漫性实变与结节。在周围型肺癌中,肺腺癌肿块的毛刺征、胸膜凹陷征、小泡征及早期远处转移多见,三级支气管受累少见;而鳞癌的三级     

Seismic tomography showing subduction and slab breakoff of the Yangtze block beneath the Dabie-Sulu orogenic belt

Seismic tomography reveals that a subducted ancient block has been preserved beneath the Moho of the Dabie-Sulu orogenic belt. Taking into account of geological and geochronological data, we inferred from the tomographic images that the Yangtze block was subducted northward beneath the Sino-Korean block and broken off at the depth <200 km during 200—190 Ma. The slab breakoff of the Yangtze block is the most important dynamic mechanism to control the exhumation of UHP rocks.     

The subducted slab of Yangtze Continental block beneath the Tethyan orogen in western Yunnan

The western Yunnan area is a natural laboratory with fully developed and best preserved Tethyan orogen in the world. Seismic tomography reveals a slab-like high velocity anomaly down to 250 km beneath the western Yunnan Tethyan orogen, to its west there is a low-velocity column about 300 km wide. in the region from Lancangjiang to Mojiang an obvious low velocity in the lower crust and uppermost mantle overlies on the slab. Synthesizing the available geological and geochemical results, the present paper demonstrates that this slab-like high velocity anomaly is a part of the subducted plate of Yangtze Continental segment after the closure of Paleotethys. The collision of India and Eurasia continent starting from 50-60 MaBP might trigger thermal disturbance in the upper mantle and cause the uprising of asthenosphere, in that case the subducted Yangtze plate could be broken off, causing Cenozoic magmatic activities and underplating in the Lancangjiang-Mojiang region.     

Rock mass structure analysis based on seismic velocity and attenuation images

Seismic traveltime, amplitude and pulse-width can be used to reconstruct seismic velocity and attenuation coefficient images for a rock mass. This study discusses the appearance differences of velocity and attenuation coefficient in the ore vein and rock mass in the images. The location of the rock vein and the characteristic of the rock mass are discussed according to the difference responses of velocity and attenuation from the ore vein and mixed rock vein, fracture and rock body. The effect and limitation of the seismic tomography method for investigating ore body and rock mass is suggested on the basis of a field test result. The special observation method in this study gives a good reference for obtaining full position and directional observation in seismic tomography.     

三维非轴对称温度场的实时全息干涉层析测试技术

介绍了激光实时全息干涉层析技术用于三维温度场测量的原理、实验装置 ,对实验中的一些技术问题进行了探讨 .通过采集多个方向上的全息干涉图投影数据 ,用代数重建技术对三维温度场进行重建 ,得到较为满意的结果 .文中还对不同算法对重建结果的影响进行了讨论 .     

井间层析成像的平滑SIRT算法

井间层析成像是一个非线性反演问题 ,为了保证反演过程的稳定性 ,并提高迭代的收敛速度 ,对常规的SIRT算法进行了改进 ,即引入了平滑算子对梯度场进行动态平滑 ,并且通过线性搜索确定速度更新的步长。将这种改进的算法称为平滑SIRT算法。模型试算的结果证明 ,该方法提高了迭代的收敛速度 ,而且反演结果不受初始模型的影响 ,使反演过程的稳定性大大提高