摘要:

The Barkhausen noise technique was used to characterize machined surfaces of small diameter tensile specimens. The Barkhausen noise butterfly curves measured for specimens with different surface finishing (grinding, lathe working) at several different analyzing frequencies were compared to those obtained on electro‐polished specimens. Microstructure modifications at the surface by machining are the reason for a complex structure of the butterfly curves, especially, those achieved at high analyzing frequencies. A new analyzing technique was developed based on cross correlation of a Barkhausen noise butterfly curve with a curve of a reference material. Depth profiling results achieved by this method showed excellent agreement with x‐ray diffraction measurements. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570334

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The display industry is trying to improve yields by refining the automation processes in the manufacturing of Liquid Crystal Display (LCD) Glass. To help achieve better yields, it is necessary to locate with better precision the LCD panels with respect to robotic tools. Two approaches will be discussed to make ranging measurements on LCD Glass: a laser confocal displacement sensor and ultrasonic rangers. The knowledge gained from these measurements will improve the positioning of the robotic tools with respect to the LCD glass during the manufacturing process. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570335

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Optical Low‐Coherence Reflectometry (OLCR) is a white‐light interference technique which can be used as a sensor in a number of processing applications. Research at the Center for Process Analytical Chemistry focuses on analysis of both transparent and highly‐scattering materials. OLCR has been applied to monitor the thickness of polymer films and clear coatings on scattering matrices. Additional process applications include fermentation monitoring and non‐invasive thickness determination of highly scattering coatings on both conducting and non‐conducting substrates. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570336

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The detection of flaws that involve 5&percent; or more of the pipe wall thickness is not easy to achieve for internal defects inspected from the outside. In this work we focus on a relatively straightforward technique, based on obtaining the characteristic signature of relevant defects, and projecting the actual signals on these “standard” defect configurations, thus increasing the signal‐to‐noise ratio and providing an alternative way to determine the nature of the defect. Several options are discussed, including some that are computationally less demanding, and are susceptible of being implemented on‐line. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570337

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

This expository paper introduces the concept of on‐line sensor methodologies for monitoring the integrity of components in next generation power systems, and explains general benefits of the approach, while describing early conceptual developments of suitable NDE methodologies. The paper first explains the philosophy behind this approach (i.e. the design‐for‐inspectability concept). Specifically, we describe where and how decades of accumulated knowledge and experience in nuclear power system maintenance are utilized in Generation IV power system designs, as the designs are being actively developed, in order to advance their safety and economy. Second, we explain that Generation IV reactor design features call for the replacement of the current outage‐based maintenance by on‐line inspection and monitoring. Third, the model‐based approach toward design and performance optimization of on‐line sensor systems, using electromagnetic, ultrasonic, and radiation detectors, will be explained. Fourth, general types of NDE inspections that are considered amenable to on‐line health monitoring will be listed. Fifth, we will describe specific modeling developments to be used for radiography, EMAT UT, and EC detector design studies. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570338

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Mammography is the best method available as a non‐invasive technique for the early detection of breast cancer. The radiographic appearance of the female breast consists of radiolucent (dark) regions due to fat and radiodense (light) regions due to connective and epithelial tissue. The amount of radiodense tissue can be used as a marker for predicting breast cancer risk. Previously, we have shown that the use of statistical models is a reliable technique for segmenting radiodense tissue. This paper presents improvements in the model that allow for further development of an automated system for segmentation of radiodense tissue. The segmentation algorithm employs a two‐step process. In the first step, segmentation of tissue and non‐tissue regions of a digitized X‐ray mammogram image are identified using a radial basis function neural network. The second step uses a constrained Neyman‐Pearson algorithm, developed especially for this research work, to determine the amount of radiodense tissue. Results obtained using the algorithm have been validated by comparing with estimates provided by a radiologist employing previously established methods. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570339

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

One of the important issues in the simulation work is proper representation of the simulated objects. The geometrical shapes of the simulated objects may range from very simple to very complicated geometries. In addition, a lot of objects come with heterogeneous material properties that need to be included into simulations. These two issues play important roles in both industrial and medical radiography simulations. CT (computed tomography) became widely available to the radiography community in the recent years. Since this technology provides two‐dimensional images, CT images can be used to build models toward using in simulation work. In this work, we developed a CT image based algorithm to account for object shape complexities and heterogeneities. The resulting algorithm and absorbed energy doses in a human body part and ideal detector images obtained through the algorithm will be presented. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570340

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We extend volume‐integral eddy‐current models that have been developed for conventional nondestructive evaluation (NDE) to tissue characterization and hyperthermia thermometry. Hyperthermia is a method of cancer treatment in which the tumor is selectively heated electromagnetically relative to the surrounding tissue. The problem is to noninvasively measure the temperature of the tumor, so that the treatment can be properly handled. In past research we have reported on inverse methods in eddy‐current NDE, and we demonstrate how these inversion algorithms can be applied to solve this problem. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570341

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The ultrasonic attenuation coefficient of a fluid or solid material is an acoustic parameter routinely estimated in nondestructive evaluation (NDE) and biological tissue characterization. In this paper, a new measurement and analysis technique for estimating the attenuation coefficient as a function of frequency for a fluid or solid is described. This broadband technique combines two established concepts in attenuation coefficient estimation: (1) frequency spectrum amplitude ratios of front surface, first back surface, and second back surface reflections from interfaces of materials with plate‐like geometries, and (2) equivalent diffraction points within the transducer wave field. The new approach yields estimates of the attenuation coefficient, reflection coefficient, and material density without the need to make diffraction corrections. This simplifies the overall estimation process by eliminating the transducer characterization step, that is, by eliminating experimental characterization of the effective radius and focal length of the transducer which are required when careful calculated diffraction corrections are applied. In this paper, attenuation coefficient and reflection coefficient estimates are presented for water and three solids with estimates based on measurements made with two different transducers. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570342

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The predictions of four measurement models are compared for the 2002 Ultrasonic Benchmark Problem. The problem involves the pulse‐echo responses of spherical and cylindrical cavities. The ultrasonic waves are considered to be generated and detected by either a planar or spherically focused probe, each of finite diameter and positioned to produce normally incident or refracted waves (longitudinal or shear) of the desired angle. Among the results are a new expression for the response of the cylindrical cavity and a quantitative comparison of the various models. Noteworthy is the differences in the predictions of the beam models, for refracted angles near critical angles and for focused probes. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570343

出版商:AIP    

年代:1903

数据来源: AIP