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射线束在被检工件内的散射,常常使射线底片对比度降低.对于这个现象,文献[1]已做了较好的分析,并且给出了一定条件下的散射比与工件板厚之间的实验线性回归关系.本人认为除工件厚度外,影响散射比的因素还有很多,如焦距、射线照射场大小和X射线线质等,我们应试图找出一种能较全面反映这些因素的一般表述式. 相似文献
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在X射线源透射式工业计算机断层扫描成像技术(X-TICT)中,X射线透射物质时,发生了Compton光子散射现象,有用信息连同散射光子一起进入探头形成伪影。因此,必须进行散射修正。利用X射线透射物质时X光子散射遵循的Compton散射强度方程,结合X射线与物质相互作用的特性,建立了有效去除X—TICT在复合材料工件检测中光子散射问题造成的图像伪影的散射修正模型。探头的总计数减去散射光子数,即可有效去除X-TICT在复合材料工件检测中散射光子造成的伪影。 相似文献
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本文提出了充水管道环焊缝X射线透照时管电压的估算公式;探讨了充半水小径管道环焊缝X射线透照的某些规律。 相似文献
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前 言本标准由范围、规范性引用文件、检测人员、防护、表面状态、射线源和能量的选择、胶片和增感屏、像质计、透照方式、几何条件、散射线的屏蔽、识别系统、曝光曲线、胶片处理、底片的质量、底片的观察、验收标准、射线检测报告及底片的存档等 1 8章组成。本标准检测技术部分在 SY40 5 6— 1 993《石油天然气管道对接焊缝射线照相及质量分级》的基础上 ,参照 GB3 3 2 3— 1 987和 JB473 0— 1 994编写而成。本标准与 GB3 3 2 3— 1 987的 AB级相当 ,但 X射线底片的最低黑度由 1 .2提至 1 .5 ;明确了双壁单影透照时 ,K值和一次透照… 相似文献
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第三讲典型工件的射线照相技术 总被引:1,自引:0,他引:1
1 变截面工件透照技术变截面工件射线照相常采用的技术主要有双(多 )胶片技术、适当提高透照电压 ( X射线 )和补偿方法等。双胶片技术是在同一暗盒中放置两张感光度不同或相同的胶片同时透照 ,感光度不同的胶片的选取应按胶片特性曲线进行。适当提高透照电压进行透照时 ,技术上需要处理的问题是如何确定透照电压 ,或者说 ,对截面厚度变化的工件如何确定透照厚度。美国 ASTM标准要求底片黑度同时满足下列要求 :D =( D0 - 0 .1 5D0 )~ ( D0 0 .30 D0 )即 D =0 .85D0 ~ 1 .3D0且对 X射线1 .8≤ D≤ 4.0或对γ射线2 .0≤ D≤ 4.0式… 相似文献
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描述了球形容器及导管环焊缝X射线照相透照厚度比K函数,揭示了K与焦距f、倾角α、球径R和壁厚δ之间的函数关系,并推导出环缝投影轨迹函数。 相似文献
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Anand A. Kulkarni Allen Goland Herbert Herman Andrew J. Allen Jan Ilavsky Gabrielle G. Long Francesco De Carlo 《Journal of Thermal Spray Technology》2005,14(2):239-250
Achieving control of the microstructure of plasma-sprayed thermal barrier coating (TBC) systems offers an opportunity to tailor
coating properties to demanding applications. Accomplishing this requires a fundamental understanding of the correlations
among processing, microstructure development, and related TBC properties. This article describes the quantitative characterization
of the microstructure of plasma-sprayed partially stabilized zirconia (PSZ) coatings by means of x-ray and neutron-scattering
imaging techniques. Small-angle neutron scattering, ultra-small-angle x-ray scattering, and x-ray microtomography were used
to characterize and visualize the nature and structure of the features in these material systems. In addition, the influence
of processing parameters on microstructure development is discussed along with thermal cycling effects on the pore morphology,
and their resultant influence of the porosity on the thermal conductivity and elastic modulus of plasma-sprayed PSZ TBCs. 相似文献
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采用溶胶凝胶法,以正硅酸甲脂(tetramethyl orthosilicate,TMOS)为硅源、甲醇为溶剂,利用碱催化“一步法”,结合乙醇超临界干燥制备了密度分别是95、110、135和165mg/cm3的SiO2气凝胶。运用小角X射线散射(small-angle X-ray scattering,SAXS)分析SiO2气凝胶的微结构,并测量各密度样品635nm波长的90°方向光散射率,针对不同密度样品分别研究了光散射率与微结构的关系。研究表明:随着初始溶剂用量的增加,密度(r)、质量分形维数(Dm)随之减少,而初级粒子(a)与次级粒子(d)尺寸在增大,这可能是在初始溶剂用量增加情况下,因为原料TMOS初始浓度降低,导致相分离方式由成核主导向生长主导转变;此外分别从初级粒子、次级粒子的角度考虑,对散射率进行分析得出635nm光与气凝胶的相互作用主要是与次级粒子结构的不相干Rayleigh散射,且光散射的数值与二级结构内的体分形维数、初级粒子尺寸,次级粒子尺寸均有关。 相似文献
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为揭示声波散射在焊接板结构超声导波合成孔径阵列成像中的作用机制,将散射回波矩阵和散射渡越时间矩阵用于分析描述超声水平剪切(shear horizontal,SH)导波声波散射,探讨了焊缝散射和边界散射在导波成像中的作用关系.结果表明,散射矩阵是揭示声波散射在超声导波阵列成像作用机制的有效工具,散射回波矩阵与散射渡越时间矩阵具有相同的散射矩阵因子,导波图像出现与散射矩阵因子成倍数关系的“条带”伪像,图像椭圆簇轨迹特征复杂化,图像背景噪声增强,图像信噪比减小.研究工作可为深入开展焊接板结构超声导波非直线阵列成像算法研究提供基础. 相似文献
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Diffuse scattering measurements of static atomic displacements in crystalline binary solid solutions
G. E. Ice C. J. Sparks X. Jiang L. Robertson 《Journal of Phase Equilibria and Diffusion》1998,19(6):529-537
Diffuse x-ray scattering from crystalline solid solutions is sensitive to both local chemical order and local bond distances.
In short-range ordered alloys, fluctuations of chemistry and bond distances break the long-range symmetry of the crystal within
a local region and contribute to the total energy of the alloy. Recent use of tunable synchrotron radiation to change the
x-ray scattering contrast between elements has greatly advanced the measurement of bond distances between the three kinds
of atom pairs found in crystalline binary alloys. The estimated standard deviation on these recovered static displacements
approaches ± 0.001 ? (± 0.0001 nm), which is an order of magnitude more precise than obtained with extended x-ray absorption
fine structure measurement. In addition, both the radial and tangential displacements can be recovered to five near neighbors
and beyond. These static displacement measurements provide new information that challenges the most advanced theoretical models
of binary crystalline alloys. 相似文献
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J.D. Comins W. Pang A.G. Every D. Pietersen 《International Journal of Refractory Metals and Hard Materials》1998,16(4-6):389-394
Surface Brillouin scattering is used to study a variety of acoustic excitations in TiN films on high speed and mild steel. The dispersion relation is measured and calculated using surface Green's functions. Reduced elastic constants of the thinner films are necessary to produce agreement between theory and experiment. This is considered to be the result of an interface layer consisting mainly of titanium oxide (TiO) as identified by XPS measurements. In TiNx films the residual stress and critical load are well correlated with the surface acoustic wave velocity. 相似文献
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Chao XuChunhui Yang Li DaiLiang Sun Yuheng XuLiangcai Cao 《Journal of Alloys and Compounds》2011,509(10):4167-4170
A series of LiNbO3:Fe:Mn:Zr crystals with different ratios of Li/Nb in the melt (0.94,1.05,1.20 and 1.38, respectively) were grown by the conventional Czochralski technique. The ultraviolet-visible spectra were measured in order to analyze the defect structure of the crystals. The measurement of the Zr concentrations and Li/Nb ratios in the crystals was carried out with an inductively coupled plasma atomic emission spectrometer. The light-induced scattering was investigated as a function of exposure energy. The results showed that the ability to resist the light-induced scattering was improved considerably with the increase of the Li/Nb ratio. The relationship between the defect structures and the light-induced scattering was discussed. 相似文献
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以NaHB4做还原剂,利用一步共还原氯金酸(HAuCl4)和硝酸银(AgNO3)制备了金银复合结构的纳米颗粒。用透射电子显微镜对所制备的金银复合纳米微粒的形貌和尺寸进行了表征。紫外可见光学吸收光谱的研究表明:通过一步共还原法所制备的金银复合纳米微粒的光学吸收谱具有单峰的等离子体吸收特征,其吸收峰介于纯金和纯银纳米颗粒特征吸收峰之间,且随着反应液中金离子和银离子的摩尔比的增加而向长波方向移动。Mie散射理论的定量计算结果同样说明了实验所观察到的金银复合纳米微粒的光学吸收的组分可剪裁性。 相似文献
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含Li的Al-Zn-Mg-Cu合金沉淀析出过程的定量分析 总被引:3,自引:0,他引:3
应用小角度X射线散射技术结合TEM分析定量的描述Al-Zn-Mg-Cu-Li合金时效过程中析出相尺寸分布和形貌等信息。通过分析确定合金在几种时效状态下析出相为轴比在0.2~0.4之间的扁回转椭球形。确定了析出相特征尺寸的对数正态分布和质量依回转半径的Maxwell分布。并分析分布曲线随动力强度Ks的变化特征,可以看出,析出相尺寸和质量分布曲线基本满足随动力强度增加,几何平均值增加,分布范围变宽。 相似文献