R/S分形预测裂缝发育程度

裂缝发育与否对于低渗低丰度气藏有着至关重要的影响,根据分析本区块不同岩性的成像测井对应层位的裂缝参数以及自然伽马分维数,建立二者之间的联系,形成了一套通过自然伽马分维数来识别不同岩性裂缝发育程度的图版,本区块裂缝孔隙度的范围在0~0.15%之间,以0.05%,0.1%为裂缝发育程度的界限,分为发育,较发育,不发育3类,进而预测裂缝发育的程度。     

LD夜视成像探测中基于PSF的超分辨率重建技术研究

夜视目标识别在视频监控中起着非常重要的作用。从早期的红外热成像发展至今,激光夜视成像系统被广泛的应用。它不仅受到大气吸收和散射特性的影响,还与光学系统中的透镜及传感器的衍射极限有关。在既有成本下,通过图像复原和超分辨率重建,可以尽可能的提高夜视成像的成像质量。很多学者的研究结果表明,成像系统的点扩散函数作为先验知识,可以提高图像复原的质量。因此,本文在最大后验概率框架下,实现点扩散函数与凸集投影超分辨率重建相结合,并应用到半导体激光夜视成像探测系统中,客观的图像质量评价标准被用来决定迭代次数。目标识别的实验结果表明,用本文提出的重建方法可以有效提高半导体激光夜视成像的范围和成像质量。     

多元遥感影像数据融合研究

由于遥感数据越来越丰富,不同传感器获取的影像数据在几何、光谱和空间分辨率等方面存在着一定的局限性和差异性。全色波段和多光谱影像融合得到的影像,兼有全色波段的高空间分辨率和多光谱影像的高光谱分辨率特性,可以满足影像解译的需求,而且融合后更能突出影像的某些特征:如土地利用变化和森林覆盖的变化等等。本文主要是介绍遥感影像融合的基本原理、融合后影像的评定和分析,并且将以主成份影像融合、IHS变换与直方图匹配法的遥感影像融合,进行以南昌市部分地区Quickbird全色影像和多光谱影像的融合实验分析。     

数码相机的成像缺陷与应对方法

数码相机逐渐普及,但由于数码器件的物理特性和技术限制,目前数码相机成像不可避免地还存在很多不足之处。着重对数码相机的成像缺陷进行研究和归纳,并提供应对思路与方法。     

Assessment of rice fields by GIS/GPS-supported classification of MODIS data

INTRODUCTIONInthelastdecade,remotesensinghasbeenincreasinglyidentifiedasanobjective,standardized,possiblycheaperandfastermethodologyforcropproductionsurveysthanconventionalfieldinves-tigations(Bauman,1992).Muchprogresshasbeenmadethroughintensivestudiesoninventoryandproductionforecastingformajorcrops,suchaswheat,rice,cottonandmaize(Tennakoonetal.,1992;Rayetal.,1994;Fangetal.,1998).China,adevelopingcountrywith1.2billionpeople,hasbeenpayingcloseattentiontoitsex-istingandfuturefoodproduction…     

“医学成像技术”课程教学改革探究

本文以课堂教学模式创新为出发点,对“医学成像技术”课程教学进行改革。注重学生对课程基本概念和成像原理的理解与掌握,突出课程教学内容与临床实践的紧密结合,剖析成像技术的发展趋势,强化对成像技术转化应用的认识。课程教学改革既促进了学生学习的主观能动性,也强调了对创新思维的培养。     

Book reviews

Thigh muscle volume is a useful determinant of functional fitness. However, anthropometric prediction of muscle content is influenced by the variability of adipose tissue accumulation. The aims of this study were to predict thigh muscle and adipose tissue volumes from anthropometry and to assess the validity of the method by examining the various components of the measurements and the assumptions involved. The 19 participants (9 men, 10 women; age 23-49 years) varied in adiposity. They all underwent magnetic resonance imaging (MRI) of the upper leg and the eight men and two women with the lowest adiposity underwent detailed anthropometry involving girths and skinfolds. Using MRI as the reference method, muscle volume was predicted from anthropometry using a circular concentric model, and the assumptions inherent in the method were tested further using the MRI data alone. Muscle volume was best predicted by anthropometry in the 10 leanest participants using a five-slice truncated cone model that overestimated the mean MRI value by 30% ( R 2 = 0.95; standard error of estimate = 288 cm 3 ; P ? 0.001). A single skinfold plus girth measurement at the mid-thigh almost matched its predictive ability, but with an increased bias. Measurements of leg circumference by means of the two techniques agreed well. The assumption of a circular cross-section was valid. In contrast, the agreement between skinfold thickness measured by caliper and superficial adipose tissue thickness by MRI was poor, contributing to the scatter of fat and lean area comparisons. An anterior skinfold thickness measurement underestimated the area of superficial adipose tissue at that level, particularly at the most proximal and distal sites. Although these limitations increase the uncertainties of muscle volume determination by anthropometry, they do not prevent its valid prediction in leaner individuals. The prediction of superficial adipose tissue was poorer.     

Creatine kinase,myosin heavy chains and magnetic resonance imaging after eccentric exercise

The aim of this study was to examine the relationship between myosin heavy chain (MHC) release as a specific marker of slow-twitch muscle fibre breakdown and magnetic resonance imaging (MRI) of skeletal muscle injury after eccentric exercise. The effects of a single series of 70 high-intensity eccentric contractions of the quadriceps femoris muscle group (single leg) on plasma concentrations of creatine kinase and MHC fragments were assessed in 10 young male sport education trainees before and 1 and 4 days after exercise. To visualize muscle injury, MRI of the loaded thigh was performed before and 4 days after the eccentric exercise. All participants recorded an increase ( P ? 0.05) in creatine kinase after exercise. In five participants, T2 signal intensity was unchanged post-exercise compared with pre-exercise and MHC plasma concentration was normal; however, they showed an increase ( P ? 0.05) in creatine kinase after exercise. For the remaining five participants, there was an increase in T2 signal intensity of the loaded vastus intermedius and vastus lateralis. These changes in MRI were accompanied by an increase in MHC plasma concentration ( P ? 0.01) as well as an increase in creatine kinase ( P ? 0.01). We suggest that changes in MRI T2 signal intensity after muscle damage induced by eccentric exercise are closely related to damage to structurally bound contractile filaments of some muscle fibres. Additionally, MHC plasma release indicates that this damage affects not only fast-twitch fibres but also some slow-twitch fibres.     

Simple PSF based method for pupil phase mask’s optimization in wavefront coding system

INTRODUCTION Wavefront coding was introduced to increase the depth of focus for optical system in 1995 by Dowski and Cathey (1995). A cubic phase mask was placed in pupil plane to encode the wavefront of the optical system by which the intermediate image formed could almost be invariant in a large depth of focus, and the intermediate image could be digitally restored into clear one. This technique shows wonderful re- sults in extending the depth of focus (Cathey and Dowski, 2002; Gómez-…     

磁共振动态增强技术在小肝癌诊断中的应用价值

目的分析小肝癌(SHCC)在MR平扫及动态增强的信号特点,评价其诊断符合率.方法回顾性分析经病理证实的40例患者总共44个SHCC病灶的T1WI、T2WI及多期动态增强扫描图像,并绘制动态增强时间-信号强度曲线,探讨SHCC的强化特点.结果动态增强在小肝癌的检出及定性诊断方面都明显优于MR平扫,其差异具有统计学意义;SHCC以速升速降型强化方式为主,动态增强各期中动脉晚期显示小肝癌最为理想,较其它各期两两比较均具有统计学意义.结论肝脏多期动态增强扫描能够真实直观的反映SHCC的供血特点,更有利于其检出及定性诊断,时间-信号强度曲线对强化类型的显示更为直观.