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Sample records for beam hardening correction

  1. Empirical beam hardening correction (EBHC) for CT

    Energy Technology Data Exchange (ETDEWEB)

    Kyriakou, Yiannis; Meyer, Esther; Prell, Daniel; Kachelriess, Marc [Institute of Medical Physics, University of Erlangen-Nuernberg, 91052 Erlangen (Germany)

    2010-10-15

    Purpose: Due to x-ray beam polychromaticity and scattered radiation, attenuation measurements tend to be underestimated. Cupping and beam hardening artifacts become apparent in the reconstructed CT images. If only one material such as water, for example, is present, these artifacts can be reduced by precorrecting the rawdata. Higher order beam hardening artifacts, as they result when a mixture of materials such as water and bone, or water and bone and iodine is present, require an iterative beam hardening correction where the image is segmented into different materials and those are forward projected to obtain new rawdata. Typically, the forward projection must correctly model the beam polychromaticity and account for all physical effects, including the energy dependence of the assumed materials in the patient, the detector response, and others. We propose a new algorithm that does not require any knowledge about spectra or attenuation coefficients and that does not need to be calibrated. The proposed method corrects beam hardening in single energy CT data. Methods: The only a priori knowledge entering EBHC is the segmentation of the object into different materials. Materials other than water are segmented from the original image, e.g., by using simple thresholding. Then, a (monochromatic) forward projection of these other materials is performed. The measured rawdata and the forward projected material-specific rawdata are monomially combined (e.g., multiplied or squared) and reconstructed to yield a set of correction volumes. These are then linearly combined and added to the original volume. The combination weights are determined to maximize the flatness of the new and corrected volume. EBHC is evaluated using data acquired with a modern cone-beam dual-source spiral CT scanner (Somatom Definition Flash, Siemens Healthcare, Forchheim, Germany), with a modern dual-source micro-CT scanner (TomoScope Synergy Twin, CT Imaging GmbH, Erlangen, Germany), and with a modern

  2. Beam hardening correction algorithm in microtomography images

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    Sales, Erika S.; Lima, Inaya C.B.; Lopes, Ricardo T., E-mail: esales@con.ufrj.b, E-mail: ricardo@lin.ufrj.b [Coordenacao dos Programas de Pos-graduacao de Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Lab. de Instrumentacao Nuclear; Assis, Joaquim T. de, E-mail: joaquim@iprj.uerj.b [Universidade do Estado do Rio de Janeiro (UERJ), Nova Friburgo, RJ (Brazil). Inst. Politecnico. Dept. de Engenharia Mecanica

    2009-07-01

    Quantification of mineral density of bone samples is directly related to the attenuation coefficient of bone. The X-rays used in microtomography images are polychromatic and have a moderately broad spectrum of energy, which makes the low-energy X-rays passing through a sample to be absorbed, causing a decrease in the attenuation coefficient and possibly artifacts. This decrease in the attenuation coefficient is due to a process called beam hardening. In this work the beam hardening of microtomography images of vertebrae of Wistar rats subjected to a study of hyperthyroidism was corrected by the method of linearization of the projections. It was discretized using a spectrum in energy, also called the spectrum of Herman. The results without correction for beam hardening showed significant differences in bone volume, which could lead to a possible diagnosis of osteoporosis. But the data with correction showed a decrease in bone volume, but this decrease was not significant in a confidence interval of 95%. (author)

  3. Segmentation-free empirical beam hardening correction for CT

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    Schüller, Sören; Sawall, Stefan [German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg 69120 (Germany); Stannigel, Kai; Hülsbusch, Markus; Ulrici, Johannes; Hell, Erich [Sirona Dental Systems GmbH, Fabrikstraße 31, 64625 Bensheim (Germany); Kachelrieß, Marc, E-mail: marc.kachelriess@dkfz.de [German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg (Germany)

    2015-02-15

    Purpose: The polychromatic nature of the x-ray beams and their effects on the reconstructed image are often disregarded during standard image reconstruction. This leads to cupping and beam hardening artifacts inside the reconstructed volume. To correct for a general cupping, methods like water precorrection exist. They correct the hardening of the spectrum during the penetration of the measured object only for the major tissue class. In contrast, more complex artifacts like streaks between dense objects need other techniques of correction. If using only the information of one single energy scan, there are two types of corrections. The first one is a physical approach. Thereby, artifacts can be reproduced and corrected within the original reconstruction by using assumptions in a polychromatic forward projector. These assumptions could be the used spectrum, the detector response, the physical attenuation and scatter properties of the intersected materials. A second method is an empirical approach, which does not rely on much prior knowledge. This so-called empirical beam hardening correction (EBHC) and the previously mentioned physical-based technique are both relying on a segmentation of the present tissues inside the patient. The difficulty thereby is that beam hardening by itself, scatter, and other effects, which diminish the image quality also disturb the correct tissue classification and thereby reduce the accuracy of the two known classes of correction techniques. The herein proposed method works similar to the empirical beam hardening correction but does not require a tissue segmentation and therefore shows improvements on image data, which are highly degraded by noise and artifacts. Furthermore, the new algorithm is designed in a way that no additional calibration or parameter fitting is needed. Methods: To overcome the segmentation of tissues, the authors propose a histogram deformation of their primary reconstructed CT image. This step is essential for the

  4. Multi-material linearization beam hardening correction for computed tomography.

    Science.gov (United States)

    Lifton, J J

    2017-03-03

    Since beam hardening causes cupping and streaking artifacts in computed tomographic images, the presence of such artifacts can impair both qualitative and quantitative analysis of the reconstructed data. When the scanned object is composed of a single material, it is possible to correct beam hardening artifacts using the linearization method. However, for multi-material objects, an iterative segmentation-based correction algorithm is needed, which is not only computationally expensive, but may also fail if the initial segmentation result is poor. In this study, a new multi-material linearization beam hardening correction method was proposed and evaluated. The new method is fast and implemented in the same manner as a mono-material linearization. The correction takes approximately 0.02 seconds per projection. Although facing a potential disadvantage of requiring attenuation measurements of one of the object's constituent materials, applying the new method has demonstrated its capability for a multi-material workpiece with substantial reduction in both cupping and streaking artifacts. For example, the study showed that the absolute cupping artefacts in steel, titanium and aluminum spheres were reduced from 22%, 20% and 20% to 5%, 1% and 0%, respectively.

  5. Calibration free beam hardening correction for cardiac CT perfusion imaging

    Science.gov (United States)

    Levi, Jacob; Fahmi, Rachid; Eck, Brendan L.; Fares, Anas; Wu, Hao; Vembar, Mani; Dhanantwari, Amar; Bezerra, Hiram G.; Wilson, David L.

    2016-03-01

    Myocardial perfusion imaging using CT (MPI-CT) and coronary CTA have the potential to make CT an ideal noninvasive gate-keeper for invasive coronary angiography. However, beam hardening artifacts (BHA) prevent accurate blood flow calculation in MPI-CT. BH Correction (BHC) methods require either energy-sensitive CT, not widely available, or typically a calibration-based method. We developed a calibration-free, automatic BHC (ABHC) method suitable for MPI-CT. The algorithm works with any BHC method and iteratively determines model parameters using proposed BHA-specific cost function. In this work, we use the polynomial BHC extended to three materials. The image is segmented into soft tissue, bone, and iodine images, based on mean HU and temporal enhancement. Forward projections of bone and iodine images are obtained, and in each iteration polynomial correction is applied. Corrections are then back projected and combined to obtain the current iteration's BHC image. This process is iterated until cost is minimized. We evaluate the algorithm on simulated and physical phantom images and on preclinical MPI-CT data. The scans were obtained on a prototype spectral detector CT (SDCT) scanner (Philips Healthcare). Mono-energetic reconstructed images were used as the reference. In the simulated phantom, BH streak artifacts were reduced from 12+/-2HU to 1+/-1HU and cupping was reduced by 81%. Similarly, in physical phantom, BH streak artifacts were reduced from 48+/-6HU to 1+/-5HU and cupping was reduced by 86%. In preclinical MPI-CT images, BHA was reduced from 28+/-6 HU to less than 4+/-4HU at peak enhancement. Results suggest that the algorithm can be used to reduce BHA in conventional CT and improve MPI-CT accuracy.

  6. A fast beam hardening correction method incorporated in a filtered back-projection based MAP algorithm

    Science.gov (United States)

    Luo, Shouhua; Wu, Huazhen; Sun, Yi; Li, Jing; Li, Guang; Gu, Ning

    2017-03-01

    The beam hardening effect can induce strong artifacts in CT images, which result in severely deteriorated image quality with incorrect intensities (CT numbers). This paper develops an effective and efficient beam hardening correction algorithm incorporated in a filtered back-projection based maximum a posteriori (BHC-FMAP). In the proposed algorithm, the beam hardening effect is modeled and incorporated into the forward-projection of the MAP to suppress beam hardening induced artifacts, and the image update process is performed by Feldkamp–Davis–Kress method based back-projection to speed up the convergence. The proposed BHC-FMAP approach does not require information about the beam spectrum or the material properties, or any additional segmentation operation. The proposed method was qualitatively and quantitatively evaluated using both phantom and animal projection data. The experimental results demonstrate that the BHC-FMAP method can efficiently provide a good correction of beam hardening induced artefacts.

  7. Beam hardening correction for a cone-beam CT system and its effect on spatial resolution

    Institute of Scientific and Technical Information of China (English)

    ZHAO Wei; WEI Long; YU Zhong-Qiang; FU Guo-Tao; SUN Cui-Li; WANG Yan-Fang; WEI Cun-Feng; CAO Da-Quan; QUE Jie-Min; TANG Xiao; SHI Rong-Jian

    2011-01-01

    In this paper,we present a beam hardening correction (BHC) method in three-dimension space for a cone-beam computed tomography (CBCT) system in a mono-material case and investigate its effect on the spatial resolution.Due to the polychromatic character of the X-ray spectrum used,cupping and streak artifacts called beam hardening artifacts arise in the reconstructed CT images,causing reduced image quality.In addition,enhanced edges are introduced in the reconstructed CT images because of the beam hardening effect.The spatial resolution of the CBCT system is calculated from the edge response function (ERF) on different planes in space.Thus,in the CT images with beam hardening artifacts,enhanced ERFs will be extracted to calculate the modulation transfer function (MTF),obtaining a better spatial resolution that deviates from the real value.Reasonable spatial resolution can be obtained after reducing the artifacts.The 10% MTF value and the full width at half maximum (FWHM) of the point spread function with and without BHC are presented.

  8. Beam hardening correction for interior tomography based on exponential formed model and radon inversion transform

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    Chen, Siyu; Zhang, Hanming; Li, Lei; Xi, Xiaoqi; Han, Yu; Yan, Bin

    2016-10-01

    X-ray computed tomography (CT) has been extensively applied in industrial non-destructive testing (NDT). However, in practical applications, the X-ray beam polychromaticity often results in beam hardening problems for image reconstruction. The beam hardening artifacts, which manifested as cupping, streaks and flares, not only debase the image quality, but also disturb the subsequent analyses. Unfortunately, conventional CT scanning requires that the scanned object is completely covered by the field of view (FOV), the state-of-art beam hardening correction methods only consider the ideal scanning configuration, and often suffer problems for interior tomography due to the projection truncation. Aiming at this problem, this paper proposed a beam hardening correction method based on radon inversion transform for interior tomography. Experimental results show that, compared to the conventional correction algorithms, the proposed approach has achieved excellent performance in both beam hardening artifacts reduction and truncation artifacts suppression. Therefore, the presented method has vitally theoretic and practicable meaning in artifacts correction of industrial CT.

  9. A new approach for beam hardening correction based on the local spectrum distributions

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    Rasoulpour, Naser; Kamali-Asl, Alireza, E-mail: a_kamali@sbu.ac.ir; Hemmati, Hamidreza

    2015-09-11

    Energy dependence of material absorption and polychromatic nature of x-ray beams in the Computed Tomography (CT) causes a phenomenon which called “beam hardening”. The purpose of this study is to provide a novel approach for Beam Hardening (BH) correction. This approach is based on the linear attenuation coefficients of Local Spectrum Distributions (LSDs) in the various depths of a phantom. The proposed method includes two steps. Firstly, the hardened spectra in various depths of the phantom (or LSDs) are estimated based on the Expectation Maximization (EM) algorithm for arbitrary thickness interval of known materials in the phantom. The performance of LSD estimation technique is evaluated by applying random Gaussian noise to transmission data. Then, the linear attenuation coefficients with regarding to the mean energy of LSDs are obtained. Secondly, a correction function based on the calculated attenuation coefficients is derived in order to correct polychromatic raw data. Since a correction function has been used for the conversion of the polychromatic data to the monochromatic data, the effect of BH in proposed reconstruction must be reduced in comparison with polychromatic reconstruction. The proposed approach has been assessed in the phantoms which involve less than two materials, but the correction function has been extended for using in the constructed phantoms with more than two materials. The relative mean energy difference in the LSDs estimations based on the noise-free transmission data was less than 1.5%. Also, it shows an acceptable value when a random Gaussian noise is applied to the transmission data. The amount of cupping artifact in the proposed reconstruction method has been effectively reduced and proposed reconstruction profile is uniform more than polychromatic reconstruction profile. - Highlights: • A novel Beam Hardening (BH) correction approach was described. • A new concept named Local Spectrum Distributions (LSDs) was used to BH

  10. X-ray beam hardening correction for measuring density in linear accelerator industrial computed tomography

    Institute of Scientific and Technical Information of China (English)

    ZHOU Ri-Feng; WANG Jue; CHEN Wei-Min

    2009-01-01

    Due to X-ray attenuation being approximately proportional to material density, it is possible to measure the inner density through Industrial Computed Tomography (ICT) images accurately. In practice, however, a number of factors including the non-linear effects of beam hardening and diffuse scattered radia-tion complicate the quantitative measurement of density variations in materials. This paper is based on the linearization method of beam hardening correction, and uses polynomial fitting coefficient which is obtained by the curvature of iron polychromatic beam data to fit other materials. Through theoretical deduction, the paper proves that the density measure error is less than 2% if using pre-filters to make the spectrum of linear accelerator range mainly 0.3 MeV to 3 MeV. Experiment had been set up at an ICT system with a 9 MeV electron linear accelerator. The result is satisfactory. This technique makes the beam hardening correction easy and simple, and it is valuable for measuring the ICT density and making use of the CT images to recognize materials.

  11. Model-based approach for beam hardening correction and resolution measurements in microtomography

    Science.gov (United States)

    van de Casteele, Elke

    X-ray computed tomography (CT) is a relative new technique developed in the late 1970's, which enables the nondestructive visualization of the internal structure of objects. This technique is based on the interaction of X-rays with matter. Passing through an object X-rays will be attenuated in a manner dependent on the density and atomic number and of the used X-ray energies. In radiography use is made of this attenuation. However the main disadvantage of radiography is the superposition of the different internal structures in one image which complicates visualization and quantification. Tomography uses the radiographic images obtained from different angles. Using an algorithm called filter back projection it is possible to reconstruct a virtual slice through the object. When different consecutive slices are reconstructed a 3D visualization can be obtained. One of the first and most difficult artefacts one meets in muCT is beam hardening. This artefact is a result of the polychromatic X-ray tube use. When the X-ray bundle traversing the object consists of X-rays with a spectrum of different energies, the lowest X-ray energies will be preferentially absorbed. As a consequence, the higher X-ray energies remain in the beam when passing an object. These X-rays are less likely to be attenuated, thus the beam becomes harder. In the first part of this dissertation the bimodal energy model is presented for correcting beam hardening. The advantage of this model is the possibility to obtain more information about the source-detector system through the physical parameters of the model, which proves to give a good description of the beam hardening artefact for different materials at different tube voltages for the specified combination of source and detector. Furthermore a correction scheme is presented which gives good results for different materials (such as plexiglas and aluminium) and biological test objects (water and bone). In the second part of this thesis, the

  12. MicroCT Bone Densitometry: Context Sensitivity, Beam Hardening Correction and the Effect of Surrounding Media

    Directory of Open Access Journals (Sweden)

    Philip L. Salmon

    2014-12-01

    Full Text Available The context-sensitivity of microCT bone densitometry due to beam hardening artefacts was assessed. Bones and teeth are scanned with varying thickness of surrounding media (water, alcohol, biological tissue and it is important to understand how this affects reconstructed attenuation (“density” of the mineralized tissue. Aluminium tubes and rods with thickness 0.127mm–5mm were scanned both in air or surrounded by up to 2cm of water. Scans were performed with different energy filters and degrees of software beam hardening correction (BHC. Also tested were the effects of signal-to-noise ratio, magnification and truncation. The thickness of an aluminium tube significantly affected its mean reconstructed attenuation. This effect of thickness could be reduced substantially by BHC for scans in air, but not for scans in water. Varying thickness of surrounding water also changed the mean attenuation of an aluminium tube. This artefact could be almost eliminated by an optimal BHC value. The “cupping” artefact of heterogeneous attenuation (elevated at outer surfaces could be corrected if aluminium was scanned in air, but in water BHC was much less effective. Scan truncation, changes to magnification and signal-to-noise ratio also caused artificial changes to measured attenuation. Measurement of bone mineral density by microCT is highly context sensitive. A surrounding layer of liquid or biological tissue reduces the ability of software BHC to remove bone density artefacts. Sample thickness, truncation, magnification and signal to noise ratio also affect reconstructed attenuation. Thus it is important for densitometry that sample and calibration phantom dimensions and mounting materials are standardised.

  13. Beam hardening correction using iterative total variation (ITV)-based algorithm in CBCT reconstruction

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    Seo, Chang-Woo; Cha, Bo Kyung; Jeon, Sungchae; Huh, Young [Converged Medical Device Research Center, Advanced Medical Device Research Division, KERI, Gyeonggido 426-910 (Korea, Republic of)

    2015-07-01

    Recently, beam hardening reduction is required to produce high-quality reconstructions of X-ray cone-beam computed tomography (CBCT) system for medical applications. This paper introduces the iterative total variation (ITV) for filtered-backprojection suffering from the serious beam hardening problems. Feldkamp, Davis, and Kress (FDK) reconstruction algorithm for CBCT system is widely used reconstruction technique. FDK reconstruction algorithm could be realized by generating the weighted projection data, filtering the projection images, and back-projecting the filtered projection data into the volume. However, FDK algorithm suffers from the beam hardening artifacts by X-ray attenuation coefficients. Recently, total variation (TV) method for compressed sensing (CS) has been particularly useful in exploiting the prior knowledge of minimal variation in the X-ray attenuation characteristics across object or human body. But a practical implementation of this method still remains a challenge. The main problem is the iterative nature of solving the TV-based CS formulation, which generally requires multiple iterations of forward and backward projections of a large dataset in clinically or industrially feasible time frame. In this paper, we propose ITV method after FDK reconstruction for reducing the beam hardening artifacts. The beam hardening problems are reduced by the ITV method to promote sparsity inherent in the X-ray attenuation characteristics. (authors)

  14. Enhancement of image quality with a fast iterative scatter and beam hardening correction method for kV CBCT.

    Science.gov (United States)

    Reitz, Irmtraud; Hesse, Bernd-Michael; Nill, Simeon; Tücking, Thomas; Oelfke, Uwe

    2009-01-01

    The problem of the enormous amount of scattered radiation in kV CBCT (kilo voltage cone beam computer tomography) is addressed. Scatter causes undesirable streak- and cup-artifacts and results in a quantitative inaccuracy of reconstructed CT numbers, so that an accurate dose calculation might be impossible. Image contrast is also significantly reduced. Therefore we checked whether an appropriate implementation of the fast iterative scatter correction algorithm we have developed for MV (mega voltage) CBCT reduces the scatter contribution in a kV CBCT as well. This scatter correction method is based on a superposition of pre-calculated Monte Carlo generated pencil beam scatter kernels. The algorithm requires only a system calibration by measuring homogeneous slab phantoms with known water-equivalent thicknesses. In this study we compare scatter corrected CBCT images of several phantoms to the fan beam CT images acquired with a reduced cone angle (a slice-thickness of 14 mm in the isocenter) at the same system. Additional measurements at a different CBCT system were made (different energy spectrum and phantom-to-detector distance) and a first order approach of a fast beam hardening correction will be introduced. The observed image quality of the scatter corrected CBCT images is comparable concerning resolution, noise and contrast-to-noise ratio to the images acquired in fan beam geometry. Compared to the CBCT without any corrections the contrast of the contrast-and-resolution phantom with scatter correction and additional beam hardening correction is improved by a factor of about 1.5. The reconstructed attenuation coefficients and the CT numbers of the scatter corrected CBCT images are close to the values of the images acquired in fan beam geometry for the most pronounced tissue types. Only for extreme dense tissue types like cortical bone we see a difference in CT numbers of 5.2%, which can be improved to 4.4% with the additional beam hardening correction. Cupping is

  15. Enhancement of image quality with a fast iterative scatter and beam hardening correction method for kV CBCT

    Energy Technology Data Exchange (ETDEWEB)

    Reitz, Irmtraud; Hesse, Bernd-Michael; Nill, Simeon; Tuecking, Thomas; Oelfke, Uwe [DKFZ, Heidelberg (Germany)

    2009-07-01

    The problem of the enormous amount of scattered radiation in kV CBCT (kilo voltage cone beam computer tomography) is addressed. Scatter causes undesirable streak- and cup-artifacts and results in a quantitative inaccuracy of reconstructed CT numbers, so that an accurate dose calculation might be impossible. Image contrast is also significantly reduced. Therefore we checked whether an appropriate implementation of the fast iterative scatter correction algorithm we have developed for MV (mega voltage) CBCT reduces the scatter contribution in a kV CBCT as well. This scatter correction method is based on a superposition of pre-calculated Monte Carlo generated pencil beam scatter kernels. The algorithm requires only a system calibration by measuring homogeneous slab phantoms with known water-equivalent thicknesses. In this study we compare scatter corrected CBCT images of several phantoms to the fan beam CT images acquired with a reduced cone angle (a slice-thickness of 14 mm in the isocenter) at the same system. Additional measurements at a different CBCT system were made (different energy spectrum and phantom-to-detector distance) and a first order approach of a fast beam hardening correction will be introduced. The observed, image quality of the scatter corrected CBCT images is comparable concerning resolution, noise and contrast-to-noise ratio to the images acquired in fan beam geometry. Compared to the CBCT without any corrections the contrast of the contrast-and-resolution phantom with scatter correction and additional beam hardening correction is improved by a factor of about 1.5. The reconstructed attenuation coefficients and the CT numbers of the scatter corrected CBCT images are close to the values of the images acquired in fan beam geometry for the most pronounced tissue types. Only for extreme dense tissue types like cortical bone we see a difference in CT numbers of 5.2%, which can be improved to 4.4% with the additional beam hardening correction. Cupping

  16. CT metal artifact reduction method correcting for beam hardening and missing projections

    Science.gov (United States)

    Verburg, Joost M.; Seco, Joao

    2012-05-01

    We present and validate a computed tomography (CT) metal artifact reduction method that is effective for a wide spectrum of clinical implant materials. Projections through low-Z implants such as titanium were corrected using a novel physics correction algorithm that reduces beam hardening errors. In the case of high-Z implants (dental fillings, gold, platinum), projections through the implant were considered missing and regularized iterative reconstruction was performed. Both algorithms were combined if multiple implant materials were present. For comparison, a conventional projection interpolation method was implemented. In a blinded and randomized evaluation, ten radiation oncologists ranked the quality of patient scans on which the different methods were applied. For scans that included low-Z implants, the proposed method was ranked as the best method in 90% of the reviews. It was ranked superior to the original reconstruction (p = 0.0008), conventional projection interpolation (p implants, and better as compared to the original reconstruction (p combining algorithms tailored to specific types of implant materials.

  17. Beam hardening and motion artifacts in cardiac CT: evaluation and iterative correction method

    Science.gov (United States)

    Shen, Zeyang; Lee, Okkyun; Taguchi, Katsuyuki

    2016-03-01

    For myocardial perfusion CT exams, beam hardening (BH) artifacts may degrade the accuracy of myocardial perfusion defect detection. Meanwhile, cardiac motion may make BH process inconsistent, which makes conventional BH correction (BHC) methods ineffective. The aims of this study were to assess the severity of BH artifacts and motion artifacts and propose a projection-based iterative BHC method which has a potential to handle the motion-induced inconsistency better than conventional methods. In this study, four sets of forward projection data were first acquired using both cylindrical phantoms and cardiac images as objects: (1) with monochromatic x-rays without motion; (2) with polychromatic x-rays without motion; (3) with monochromatic x-rays with motion; and (4) with polychromatic x-rays with motion. From each dataset, images were reconstructed using filtered back projection; for datasets 2 and 4, one of the following BHC methods was also performed: (A) no BHC; (B) BHC that concerns water only; and (C) BHC that takes both water and iodine into account, which is an iterative method we developed in this work. Biases of images were quantified by the mean absolute difference (MAD). The MAD of images with BH artifacts alone (dataset 2, without BHC) was comparable or larger than that of images with motion artifacts alone (dataset 3): In the study of cardiac image, BH artifacts account for over 80% of the total artifacts. The use of BHC was effective: with dataset 4, MAD values were 170 HU with no BHC, 54 HU with water BHC, and 42 HU with the proposed BHC. Qualitative improvements in image quality were also noticeable in reconstructed images.

  18. Algorithm for X-ray scatter, beam-hardening, and beam profile correction in diagnostic (kilovoltage) and treatment (megavoltage) cone beam CT.

    Science.gov (United States)

    Maltz, Jonathan S; Gangadharan, Bijumon; Bose, Supratik; Hristov, Dimitre H; Faddegon, Bruce A; Paidi, Ajay; Bani-Hashemi, Ali R

    2008-12-01

    Quantitative reconstruction of cone beam X-ray computed tomography (CT) datasets requires accurate modeling of scatter, beam-hardening, beam profile, and detector response. Typically, commercial imaging systems use fast empirical corrections that are designed to reduce visible artifacts due to incomplete modeling of the image formation process. In contrast, Monte Carlo (MC) methods are much more accurate but are relatively slow. Scatter kernel superposition (SKS) methods offer a balance between accuracy and computational practicality. We show how a single SKS algorithm can be employed to correct both kilovoltage (kV) energy (diagnostic) and megavoltage (MV) energy (treatment) X-ray images. Using MC models of kV and MV imaging systems, we map intensities recorded on an amorphous silicon flat panel detector to water-equivalent thicknesses (WETs). Scattergrams are derived from acquired projection images using scatter kernels indexed by the local WET values and are then iteratively refined using a scatter magnitude bounding scheme that allows the algorithm to accommodate the very high scatter-to-primary ratios encountered in kV imaging. The algorithm recovers radiological thicknesses to within 9% of the true value at both kV and megavolt energies. Nonuniformity in CT reconstructions of homogeneous phantoms is reduced by an average of 76% over a wide range of beam energies and phantom geometries.

  19. Method for beam hardening correction in quantitative computed X-ray tomography

    Science.gov (United States)

    Yan, Chye Hwang (Inventor); Whalen, Robert T. (Inventor); Napel, Sandy (Inventor)

    2001-01-01

    Each voxel is assumed to contain exactly two distinct materials, with the volume fraction of each material being iteratively calculated. According to the method, the spectrum of the X-ray beam must be known, and the attenuation spectra of the materials in the object must be known, and be monotonically decreasing with increasing X-ray photon energy. Then, a volume fraction is estimated for the voxel, and the spectrum is iteratively calculated.

  20. Beam hardening and smoothing correction effects on performance of micro-ct SkyScan 1173 for imaging low contrast density materials

    Energy Technology Data Exchange (ETDEWEB)

    Sriwayu, Wa Ode [Physics Departement, Haluoleo University Indonesia (Indonesia); Haryanto, Freddy; Khotimah, Siti Nurul; Latief, Fourier Dzar Eljabbar [Physics Departement, ITB Indonesia email : ayoe-fisika@yahoo.com (Indonesia)

    2015-04-16

    We have designed and fabricated phantom mimicking breast cancer composition known as a region that has low contrast density. The used compositions are a microcalcifications, fatty tissues and tumor mass by using Al{sub 2}O{sub 3}, C{sub 27}H{sub 46}O, and hard nylon materials. Besides, phantom also has a part to calculate low cost criteria /CNR (Contrast to Noise Ratio). Uniformity will be measured at water distillation medium located in a part of phantom scale contrast. Phantom will be imaged by using micro ct-sky scan 1173 high energy type, and then also can be quantified CT number to examine SkyScan 1173 performance in imaging low contrast density materials. Evaluation of CT number is done at technique configuration parameter using voltage of 30 kV, exposure 0.160 mAs, and camera resolution 560x560 pixel, the effect of image quality to reconstruction process is evaluated by varying image processing parameters in the form of beam hardening corrections with amount of 25%, 66% and100% with each smoothing level S10,S2 and S7. To obtain the better high quality image, the adjustment of beam hardening correction should be 66% and smoothing level reach maximal value at level 10.

  1. On Analytical Solutions to Beam-Hardening

    Science.gov (United States)

    Rigaud, G.

    2017-01-01

    When polychromatic X-rays propagate through a material, for instance in computerized tomography (CT), low energy photons are more attenuated resulting in a "harder" beam. The beam-hardening phenomenon breaks the monochromatic radiation model based on the Radon transform giving rise to artifacts in CT reconstructions to the detriment of visual inspection and automated segmentation algorithms. We propose first a simplified analytic representation for the beam-hardening. Besides providing a general understanding of the phenomenon, this model proposes to invert the beam-hardening effect for homogeneous objects leading to classical monochromatic data. For heterogeneous objects, no analytical reconstruction of the density can be derived without more prior information. However, the beam-hardening is shown to be a smooth operation on the data and thus to preserve the encoding of the singularities of the attenuation map within the data. A microlocal analysis encourages the use of contour extraction methods to solve partially the beam-hardening effect even for heterogeneous objects. The application of both methods, exact analytical solution for homogeneous objects and feature extraction for heterogeneous ones, on real data demonstrates their relevancy and efficiency.

  2. Reduction of metal artifacts: beam hardening and photon starvation effects

    Science.gov (United States)

    Yadava, Girijesh K.; Pal, Debashish; Hsieh, Jiang

    2014-03-01

    The presence of metal-artifacts in CT imaging can obscure relevant anatomy and interfere with disease diagnosis. The cause and occurrence of metal-artifacts are primarily due to beam hardening, scatter, partial volume and photon starvation; however, the contribution to the artifacts from each of them depends on the type of hardware. A comparison of CT images obtained with different metallic hardware in various applications, along with acquisition and reconstruction parameters, helps understand methods for reducing or overcoming such artifacts. In this work, a metal beam hardening correction (BHC) and a projection-completion based metal artifact reduction (MAR) algorithms were developed, and applied on phantom and clinical CT scans with various metallic implants. Stainless-steel and Titanium were used to model and correct for metal beam hardening effect. In the MAR algorithm, the corrupted projection samples are replaced by the combination of original projections and in-painted data obtained by forward projecting a prior image. The data included spine fixation screws, hip-implants, dental-filling, and body extremity fixations, covering range of clinically used metal implants. Comparison of BHC and MAR on different metallic implants was used to characterize dominant source of the artifacts, and conceivable methods to overcome those. Results of the study indicate that beam hardening could be a dominant source of artifact in many spine and extremity fixations, whereas dental and hip implants could be dominant source of photon starvation. The BHC algorithm could significantly improve image quality in CT scans with metallic screws, whereas MAR algorithm could alleviate artifacts in hip-implants and dentalfillings.

  3. Reduction of beam hardening artifacts in cone-beam CT imaging via SMART-RECON algorithm

    Science.gov (United States)

    Li, Yinsheng; Garrett, John; Chen, Guang-Hong

    2016-03-01

    When an automatic exposure control is introduced in C-arm cone beam CT data acquisition, the spectral inconsistencies between acquired projection data are exacerbated. As a result, conventional water/bone correction schemes are not as effective as in conventional diagnostic x-ray CT acquisitions with a fixed tube potential. In this paper, a new method was proposed to reconstruct several images with different degrees of spectral consistency and thus different levels of beam hardening artifacts. The new method relies neither on prior knowledge of the x-ray beam spectrum nor on prior compositional information of the imaging object. Numerical simulations were used to validate the algorithm.

  4. Optimization of Laser Beam Transformation Hardening by One Single Parameter

    NARCIS (Netherlands)

    Meijer, J.; Sprang, van I.

    1991-01-01

    The process of laser beam transformation hardening is principally controlled by two independent parameters, the absorbed laser power on a given area and the interaction time. These parameters can be transformed into two functional parameters: the maximum surface temperature and the hardening depth.

  5. Free Vibration and Hardening Behavior of Truss Core Sandwich Beam

    Directory of Open Access Journals (Sweden)

    J. E. Chen

    2016-01-01

    Full Text Available The dynamic characteristics of simply supported pyramidal truss core sandwich beam are investigated. The nonlinear governing equation of motion for the beam is obtained by using a Zig-Zag theory. The averaged equations of the beam with primary, subharmonic, and superharmonic resonances are derived by using the method of multiple scales and then the corresponding frequency response equations are obtained. The influences of strut radius and core height on the linear natural frequencies and hardening behaviors of the beam are studied. It is illustrated that the first-order natural frequency decreases continuously and the second-order and third-order natural frequencies initially increase and then decrease with the increase of strut radius, and the first three natural frequencies all increase with the rise of the core height. Furthermore, the results indicate that the hardening behaviors of the beam become weaker with the increase of the rise of strut radius and core height. The mechanisms of variations in hardening behavior of the sandwich beam with the three types of resonances are detailed and discussed.

  6. A simulation-based study on the influence of beam hardening in X-ray computed tomography for dimensional metrology.

    Science.gov (United States)

    Lifton, Joseph J; Malcolm, Andrew A; McBride, John W

    2015-01-01

    X-ray computed tomography (CT) is a radiographic scanning technique for visualising cross-sectional images of an object non-destructively. From these cross-sectional images it is possible to evaluate internal dimensional features of a workpiece which may otherwise be inaccessible to tactile and optical instruments. Beam hardening is a physical process that degrades the quality of CT images and has previously been suggested to influence dimensional measurements. Using a validated simulation tool, the influence of spectrum pre-filtration and beam hardening correction are evaluated for internal and external dimensional measurements. Beam hardening is shown to influence internal and external dimensions in opposition, and to have a greater influence on outer dimensions compared to inner dimensions. The results suggest the combination of spectrum pre-filtration and a local gradient-based surface determination method are able to greatly reduce the influence of beam hardening in X-ray CT for dimensional metrology.

  7. The effects of x-ray beam hardening on detective quantum efficiency and radiation dose.

    Science.gov (United States)

    Wong, Molly Donovan; Wu, Xizeng; Liu, Hong

    2011-01-01

    The goal of this preliminary study was to investigate the effects of x-ray beam hardening on the detective quantum efficiency (DQE) and the radiation dose of an inline x-ray imaging system. The ability to decrease the risk of harmful radiation to the patient without compromising the detection capability would more effectively balance the tradeoff between image quality and radiation dose, and therefore benefit the fields of diagnostic x-ray imaging, especially mammography. The DQE and the average glandular dose were both calculated under the same experimental conditions for a range of beam hardening levels, corresponding to no added beam hardening and two thicknesses each of Rhodium (Rh) and Molybdenum (Mo) filters. The dose calculation results demonstrate a reduction of 15% to 24% for the range of beam hardening levels. The comparison of all quantities comprising the DQE exhibit very close correlation between the results obtained without added beam hardening to the results corresponding to the range of beam hardening levels. For the specific experimental conditions utilized in this preliminary study, the results are an indication that the use of beam hardening holds the potential to reduce the radiation dose without decreasing the performance of the system. Future studies will seek to apply this method in a clinical environment and perform a comprehensive image quality evaluation, in an effort to further evaluate the potential of beam hardening to balance the tradeoff between dose and image quality.

  8. Electron beam surface hardening of 42CrMo4 steel

    Energy Technology Data Exchange (ETDEWEB)

    Jokinen, T.; Meuronen, I. [Valmet Aviation Industries, Linnavuori (Finland). Engine Maintenance

    1997-12-31

    A study is reported in this paper which aims to find the proper parameters of an electron beam machine for using electron beam (EB) hardening on 42CrMo4 steel. Extended service life for engineering components depends on hard, wear resistant surfaces combined with tough base materials. EB hardening is particularly suitable to local treatment of complex components. Although surface hardening of 42CrMo4 steel was successful, careful optimization of process parameters and the hardened layer are required. (UK).

  9. Reducing beam hardening effects and metal artefacts using Medipix3RX: With applications from biomaterial science

    CERN Document Server

    Rajendran, K; de Ruiter, N J A; Chernoglazov, A I; Panta, R K; Butler, A P H; Butler, P H; Bell, S T; Anderson, N G; Woodfield, T B F; Tredinnick, S J; Healy, J L; Bateman, C J; Aamir, R; Doesburg, R M N; Renaud, P F; Gieseg, S P; Smithies, D J; Mohr, J L; Mandalika, V B H; Opie, A M T; Cook, N J; Ronaldson, J P; Nik, S J; Atharifard, A; Clyne, M; Bones, P J; Bartneck, C; Grasset, R; Schleich, N; Billinghurst, M

    2014-01-01

    This paper discusses methods for reducing beam hardening effects using spectral data for biomaterial applications. A small-animal spectral scanner operating in the diagnostic energy range was used. We investigate the use of photon-processing features of the Medipix3RX ASIC in reducing beam hardening and associated artefacts. A fully operational charge summing mode was used during the imaging routine. We present spectral data collected for metal alloy samples, its analysis using algebraic 3D reconstruction software and volume visualisation using a custom volume rendering software. Narrow high energy acquisition using the photon-processing detector revealed substantial reduction in beam hardening effects and metal artefacts.

  10. Laser transformation hardening on rod-shaped carbon steel byGaussian beam

    Institute of Scientific and Technical Information of China (English)

    Jong-Do KIM; Myeong-Hoon LEE; Su-Jin LEE; Woon-Ju KANG

    2009-01-01

    Laser transformation hardening(LTH) is one of the laser surface modification processes. The surface hardening of rod-shaped carbon steel (SM45C) was performed by lathe-based laser composite processor with Gaussian-beam optical head. The LTH characteristics by dominant processes, longitudinal and depth directional hardness distributions and behaviors of phase transformation in hardened zones were examined. Especially, two concepts of circumferential speed and theoretical overlap rate were applied. When laser power increased or circumferential speed decreased, the surface hardening depth gradually increases due to the increased heat input. Moreover, the longitudinal hardness distribution particularly shows periodicity of repetitive increase and decrease, which results from tempering effect by overlap. Finally, the feasibility of laser transformation hardening is verified by using the beam with Gaussian intensity distribution.

  11. Myocardial physiology measurements using contrast enhanced dynamic computed tomography: simulation of beam hardening effect

    Science.gov (United States)

    Cao, Minsong; Stantz, Keith M.; Liang, Yun

    2006-03-01

    Initial animal study for quantifying myocardial physiology through contrast-enhanced dynamic x-ray CT suggested that beam hardening is one of the limiting factors for accurate regional physiology measurement. In this study, a series of simulations were performed to investigate its deterioration effects and two correction algorithms were adapted to evaluate for their efficiency in improving the measurements. The simulation tool consists of a module simulating data acquisition of a real polyenergetic scanner system and a heart phantom consisting of simple geometric objects representing ventricles and myocardium. Each phantom component was modeled with time-varying attenuation coefficients determined by ideal iodine contrast dynamic curves obtained from experimental data or simulation. A compartment model was used to generate the ideal myocardium contrast curve using physiological parameters consistent with measured values. Projection data of the phantom were simulated and reconstructed to produce a sequence of simulated CT images. Simulated contrast dynamic curves were fitted to the compartmental model and the resultant physiological parameters were compared with ideal values to estimate the errors induced by beam hardening artifacts. The simulations yielded similar deterioration patterns of contrast dynamic curves as observed in the initial study. Significant underestimation of left ventricle curves and corruption of regional myocardium curves result in systematic errors of regional perfusion up to approximately 24% and overestimates of fractional blood volume (f iv) up to 13%. The correction algorithms lead to significant improvement with errors of perfusion reduced to 7% and errors of f iv within 2% which shows promise for more robust myocardial physiology measurement.

  12. Beam hardening: Analytical considerations of the effective attenuation coefficient of x-ray tomography

    NARCIS (Netherlands)

    Alles, J.; Mudde, R.F.

    2007-01-01

    Polychromatic x-ray beams traveling though material are prone to beam hardening, i.e., the high energy part of the incident spectrum gets over represented when traveling farther into the material. This study discusses the concept of a mean attenuation coefficient in a formal way. The total energy fl

  13. Corrections in the gold foil activation method for determination of neutron beam density

    DEFF Research Database (Denmark)

    Als-Nielsen, Jens Aage

    1967-01-01

    example for a reactor beam transmitted through a 30 cm Bi filter. The effective cross section differs 0.5% from the capture cross section at 2200 m/s. For a 20 mg/cm2 Au foil the correction for beam attenuation and hardening through the foil is 0.7% and the activity correction is 1.5%.......A finite foil thickness and deviation in the cross section from the 1ν law imply corrections in the determination of neutron beam densities by means of foil activation. These corrections, which depend on the neutron velocity distribution, have been examined in general and are given in a specific...

  14. Characteristics of laser beam welds of age-hardenable 6061-T6 aluminum alloy

    Science.gov (United States)

    Hirose, Akio; Kobayashi, Kojiro F.

    2003-03-01

    Laser beam welding is attractive for joining age-hardenable aluminum alloys, because its low over-all heat input results in a narrow weld heat affected zone (HAZ), where softening caused by dissolution of age precipitates occurs. In the present work, 1mm-thick 6061-T6 aluminum alloy plates were welded using a 2.5 kW CO2 laser and it was experimentally proved that the width of the softened region in the laser beam weld was less than 1/7 that of a TIG weld. Moreover the hardness in the softened region of the laser beam weld was found to be almost fully recovered to the base metal hardness by applying a post-weld aging treatment at 443 K for 28.8 ks without solution annealing unlike the TIG weld. These results characterize the advantage of laser beam welding in joining of the age-hardenable aluminum alloy as compared with the conventional arc welding. The hardness distributions in the HAZ were theoretically evaluated based on kinetic equations describing the dissolution of hardening β' (Mg2Si) precipitates and the precipitation of non-hardening β' (Mg2Si) precipitates during the weld thermal cycles to quantitatively prove above mentioned advantageous characteristics of laser beam welding.

  15. Simulation-aided investigation of beam hardening induced errors in CT dimensional metrology

    DEFF Research Database (Denmark)

    Tan, Ye; Kiekens, Kim; Welkenhuyzen, Frank

    2013-01-01

    Industrial X-ray CT systems are increasingly used as dimensional measuring machines. However, micron level accuracy is not always achievable yet. The measurement accuracy is influenced by many factors, such as workpiece properties, X-ray settings, beam hardening and calibration methods [1-4]. Since...

  16. Progress report on the neutral beam radiation hardening study

    Energy Technology Data Exchange (ETDEWEB)

    Lee, J.D.; Condit, R.H.; Hoenig, C.L.; Wilcox, T.P.; Erickson, J.

    1978-10-01

    A neutral beam injector as presently conceived directly views the plasma it is sustaining. In turn the injector is exposed to the primary fusion neutrons plus secondary neutrons and gammas streaming back up the neutral beam duct. The intent of this work is to examine representative beam lines to see how performance and lifetimes could be affected by this radiation environment and to determine how unacceptable effects could be alleviated. Potential radiation induced problems addressed in this report have been limited to: (1) overheating of cryopanels and insulators, (2) gamma flux induced electrical conductivity increase of insulators, and (3) neutron and gamma fluence induced damage to insulator materials.

  17. Free Vibration and Hardening Behavior of Truss Core Sandwich Beam

    National Research Council Canada - National Science Library

    Chen, J. E; Zhang, W; Sun, M; Yao, M. H

    2016-01-01

    .... The averaged equations of the beam with primary, subharmonic, and superharmonic resonances are derived by using the method of multiple scales and then the corresponding frequency response equations are obtained...

  18. Dispersion based beam tilt correction

    CERN Document Server

    Guetg, Marc W; Prat, Eduard; Reiche, Sven

    2013-01-01

    In Free Electron Lasers (FEL), a transverse centroid misalignment of longitudinal slices in an electron bunch reduces the effective overlap between radiation field and electron bunch and therefore the FEL performance. The dominant sources of slice misalignments for FELs are the incoherent and coherent synchrotron radiation within bunch compressors as well as transverse wake fields in the accelerating cavities. This is of particular importance for over-compression which is required for one of the key operation modes for the SwissFEL planned at the Paul Scherrer Institute. The centroid shift is corrected using corrector magnets in dispersive sections, e.g. the bunch compressors. First and second order corrections are achieved by pairs of sextupole and quadrupole magnets in the horizontal plane while skew quadrupoles correct to first order in the vertical plane. Simulations and measurements at the SwissFEL Injector Test Facility are done to investigate the proposed correction scheme for SwissFEL. This paper pres...

  19. Monoenergetic computed tomography reconstructions reduce beam hardening artifacts from dental restorations.

    Science.gov (United States)

    Stolzmann, Paul; Winklhofer, Sebastian; Schwendener, Nicole; Alkadhi, Hatem; Thali, Michael J; Ruder, Thomas D

    2013-09-01

    The aim of this study was to assess the potential of monoenergetic computed tomography (CT) images to reduce beam hardening artifacts in comparison to standard CT images of dental restoration on dental post-mortem CT (PMCT). Thirty human decedents (15 male, 58 ± 22 years) with dental restorations were examined using standard single-energy CT (SECT) and dual-energy CT (DECT). DECT data were used to generate monoenergetic CT images, reflecting the X-ray attenuation at energy levels of 64, 69, 88 keV, and at an individually adjusted optimal energy level called OPTkeV. Artifact reduction and image quality of SECT and monoenergetic CT were assessed objectively and subjectively by two blinded readers. Subjectively, beam artifacts decreased visibly in 28/30 cases after monoenergetic CT reconstruction. Inter- and intra-reader agreement was good (k = 0.72, and k = 0.73 respectively). Beam hardening artifacts decreased significantly with increasing monoenergies (repeated-measures ANOVA p < 0.001). Artifact reduction was greatest on monoenergetic CT images at OPTkeV. Mean OPTkeV was 108 ± 17 keV. OPTkeV yielded the lowest difference between CT numbers of streak artifacts and reference tissues (-163 HU). Monoenergetic CT reconstructions significantly reduce beam hardening artifacts from dental restorations and improve image quality of post-mortem dental CT.

  20. Marginal phase correction of truncated Bessel beams

    Science.gov (United States)

    Sedukhin

    2000-06-01

    Approximate analytic expressions are obtained for evaluating the axial intensity and the central-lobe diameter of J0 Bessel beams transmitted through a finite-aperture phase filter. A reasonable quality factor governing the axial-intensity behavior of a phase-undistorted truncated Bessel beam is found to be the inverse square root of the Fresnel number defined, for a given aperture, from the axial point of geometrical shadow. Additional drastic reduction of axial-intensity oscillations is accomplished by using marginal phase correction of the beam instead of the well-known amplitude apodization. A procedure for analytically calculating an optimal monotonic slowly varying correction phase function is described.

  1. Beam hardening: analytical considerations of the effective attenuation coefficient of X-ray tomography.

    Science.gov (United States)

    Alles, J; Mudde, R F

    2007-07-01

    Polychromatic x-ray beams traveling though material are prone to beam hardening, i.e., the high energy part of the incident spectrum gets over represented when traveling farther into the material. This study discusses the concept of a mean attenuation coefficient in a formal way. The total energy fluence is one-to-one related to the traveled distance in case of a polychromatic beam moving through a given, inhomogeneous material. On the basis of this one-to-one relation, it is useful to define a mean attenuation coefficient and study its decrease with depth. Our results are based on a novel parametrization of the energy dependence of the attenuation coefficient that allows for closed form evaluation of certain spectral integrals. This approach underpins the ad hoc semianalytical expressions given in the literature. An analytical model for the average attenuation coefficient is proposed that uses a simple fit of the attenuation coefficient as a function of the photon energy as input. It is shown that a simple extension of this model gives a rather good description of beam hardening for x-rays traveling through water.

  2. Non-vacuum electron-beam carburizing and surface hardening of mild steel

    Science.gov (United States)

    Bataev, I. A.; Golkovskii, M. G.; Losinskaya, A. A.; Bataev, A. A.; Popelyukh, A. I.; Hassel, T.; Golovin, D. D.

    2014-12-01

    In this paper, we study the structure, microhardness, and tribological properties of surface layers of mild (0.19% C) steel, which was formed by electron-beam cladding with an iron-graphite powder mixture followed by quenching and tempering. A 1.4 MeV electron beam that was extracted into air was used. Cladding of steel with the iron-graphite mixture at a beam current of 24 and 26 mA formed a hypoeutectic cast iron layer (2.19% C) and a hypereutectoid steel (1.57% C) layer, which were 2.0 and 2.6 mm thick, respectively. The microhardness of the surface-quenched and tempered steel and cast iron layers was 7 and 8 GPa, respectively. Electron-beam quenching of the surface layers of hypoeutectic cast iron was accompanied with multiple cracking. During the quenching of the 1.57% C steel layer, crack formation was not observed. In friction tests against fixed and loose abrasive particles, the surface layers of hypereutectoid steel and hypoeutectic cast iron that were produced by electron-beam cladding and quenching had lower wear rates than mild steel after pack carburizing, quenching, and tempering. In the sliding wear tests, the cast iron clad layer, which was subjected to electron-beam quenching and tempering, exhibited the highest wear resistance. Electron-beam treatment can be used to harden local areas of large workpieces. It is reasonable to treat clad layers of high-carbon steel with electron-beam quenching and tempering. To prevent multiple cracking, white cast iron layers should not be quenched.

  3. Experimental assessment of the influence of beam hardening filters on image quality and patient dose in volumetric 64-slice X-ray CT scanners

    NARCIS (Netherlands)

    Ay, Mohammad Reza; Mehranian, Abolfazi; Maleki, Asghar; Ghadiri, Hossien; Ghafarian, Pardis; Zaidi, Habib

    Beam hardening filters have long been employed in X-ray Computed Tomography (CT) to preferentially absorb soft and low-energy X-rays having no or little contribution to image formation, thus allowing the reduction of patient dose and beam hardening artefacts. In this work, we studied the influence

  4. Experimental assessment of the influence of beam hardening filters on image quality and patient dose in volumetric 64-slice X-ray CT scanners

    NARCIS (Netherlands)

    Ay, Mohammad Reza; Mehranian, Abolfazi; Maleki, Asghar; Ghadiri, Hossien; Ghafarian, Pardis; Zaidi, Habib

    2013-01-01

    Beam hardening filters have long been employed in X-ray Computed Tomography (CT) to preferentially absorb soft and low-energy X-rays having no or little contribution to image formation, thus allowing the reduction of patient dose and beam hardening artefacts. In this work, we studied the influence o

  5. Experimental assessment of the influence of beam hardening filters on image quality and patient dose in volumetric 64-slice X-ray CT scanners

    NARCIS (Netherlands)

    Ay, Mohammad Reza; Mehranian, Abolfazi; Maleki, Asghar; Ghadiri, Hossien; Ghafarian, Pardis; Zaidi, Habib

    2013-01-01

    Beam hardening filters have long been employed in X-ray Computed Tomography (CT) to preferentially absorb soft and low-energy X-rays having no or little contribution to image formation, thus allowing the reduction of patient dose and beam hardening artefacts. In this work, we studied the influence o

  6. Non-vacuum electron-beam carburizing and surface hardening of mild steel

    Energy Technology Data Exchange (ETDEWEB)

    Bataev, I.A., E-mail: ivanbataev@ngs.ru [Novosibirsk State Technical University, K. Marks 20, 630092 Novosibirsk (Russian Federation); Golkovskii, M.G., E-mail: M.G.Golkovski@inp.nsk.su [Budker Institute of Nuclear Physics SB RAS, Lavrentieva Prospect 11, 630090 Novosibirsk (Russian Federation); Losinskaya, A.A., E-mail: anna.losinskaya@mail.ru [Novosibirsk State Technical University, K. Marks 20, 630092 Novosibirsk (Russian Federation); Bataev, A.A., E-mail: bataev@adm.nstu.ru [Novosibirsk State Technical University, K. Marks 20, 630092 Novosibirsk (Russian Federation); Popelyukh, A.I., E-mail: aip13@mail.ru [Novosibirsk State Technical University, K. Marks 20, 630092 Novosibirsk (Russian Federation); Hassel, T., E-mail: hassel@iw.uni-hannover.de [Leibniz University, Welfengarten 1, 30167 Hannover (Germany); Golovin, D.D., E-mail: ddgolovin@yandex.ru [Novosibirsk State Technical University, K. Marks 20, 630092 Novosibirsk (Russian Federation)

    2014-12-15

    Highlights: • Steel specimens were carburized by non-vacuum electron-beam cladding. • The depth of the clad layers reached 2.6 mm. • The cladding rate was 1.8 m{sup 2}/h, the quenching rate 12.6 m{sup 2}/h. • The microhardness of the quenched and tempered layers reached 8 GPa. - Abstract: In this paper, we study the structure, microhardness, and tribological properties of surface layers of mild (0.19% C) steel, which was formed by electron-beam cladding with an iron–graphite powder mixture followed by quenching and tempering. A 1.4 MeV electron beam that was extracted into air was used. Cladding of steel with the iron–graphite mixture at a beam current of 24 and 26 mA formed a hypoeutectic cast iron layer (2.19% C) and a hypereutectoid steel (1.57% C) layer, which were 2.0 and 2.6 mm thick, respectively. The microhardness of the surface-quenched and tempered steel and cast iron layers was 7 and 8 GPa, respectively. Electron-beam quenching of the surface layers of hypoeutectic cast iron was accompanied with multiple cracking. During the quenching of the 1.57% C steel layer, crack formation was not observed. In friction tests against fixed and loose abrasive particles, the surface layers of hypereutectoid steel and hypoeutectic cast iron that were produced by electron-beam cladding and quenching had lower wear rates than mild steel after pack carburizing, quenching, and tempering. In the sliding wear tests, the cast iron clad layer, which was subjected to electron-beam quenching and tempering, exhibited the highest wear resistance. Electron-beam treatment can be used to harden local areas of large workpieces. It is reasonable to treat clad layers of high-carbon steel with electron-beam quenching and tempering. To prevent multiple cracking, white cast iron layers should not be quenched.

  7. Evaluation of CP shape correction for e-beam writing

    Science.gov (United States)

    Takizawa, Masahiro; Bunya, Keita; Isobe, Hideaki; Komami, Hideaki; Abe, Kenji; Kurokawa, Masaki; Yamada, Akio; Sakamoto, Kiichi; Nakamura, Takayuki; Kuwano, Kazusumi; Tateishi, Masahiro; Chau, Larry

    2012-11-01

    Character projection (CP) exposure has some advantages compared with variable shaped beam (VSB) system; (1) shot count reduction by printing complex patterns in one e-beam shot, (2) high pattern fidelity by using CP stencil. In this paper we address another advantage of CP exposure, namely the shape correction of CP stencil for cancelling the pattern deformation on the substrate. The deformation of CP printings is decomposed into some elements. They are CP stencil manufacturing error, proximity effect, beam blur of the e-beam writer and resist blur. The element caused by beam blur of e-beam writer can be predicted by measuring the total beam blur obtained from CD-dose curves. The pattern deformation was corrected by applying the shape correction software system of D2S. The corrected CP stencil of 22nm-node standard cell was manufactured and standard cell patterns were exposed. We confirmed that our shape correction method is the appropriate solution for correcting deformation issue of CP openings. The beam blur required for the 1X nm dimensions was predicted from the exposure results of standard cell patterns with applying shape correction and CD-dose curves. We simulated the optical system to realize the required beam blur. As a result, the next electron optics has the resolving capability of 1X nm dimension.

  8. Limitation in obtainable surface roughness of hardened cement paste: 'virtual' topographic experiment based on focussed ion beam nanotomography datasets.

    Science.gov (United States)

    Trtik, P; Dual, J; Muench, B; Holzer, L

    2008-11-01

    Surface roughness affects the results of nanomechanical tests. The surface roughness values to be measured on a surface of a porous material are dependent on the properties of the naturally occurring pore space. In order to assess the surface roughness of hardened cement paste (HCP) without the actual influence of the usual sample preparation for nanomechanical testing (i.e. grinding and polishing), focussed ion beam nanotomography datasets were utilized for reconstruction of 3D (nanoscale resolution) surface profiles of hardened cement pastes. 'Virtual topographic experiments' were performed and root mean square surface roughness was then calculated for a large number of such 3D surface profiles. The resulting root mean square (between 115 and 494 nm) is considerably higher than some roughness values (as low as 10 nm) reported in the literature. We suggest that thus-analysed root mean square values provide an estimate of a 'hard' lower limit that can be achieved by 'artefact-free' sample preparation of realistic samples of hardened cement paste. To the best of our knowledge, this 'hard' lower limit was quantified for a porous material based on hydraulic cement for the first time. We suggest that the values of RMS below such a limit may indicate sample preparation artefacts. Consequently, for reliable nanomechanical testing of disordered porous materials, such as hardened cement paste, the preparation methods may require further improvement.

  9. Transformation hardening by linear-polarized laser beam. Report 2. Development of novel laser beam shaping optics and its applications to materials processing; Chokusen henko reza wo mochiiru hentai koka. 2. Atarashii reza shaping kogakukei no kaihatsu to sono oyo

    Energy Technology Data Exchange (ETDEWEB)

    Miyamoto, I.; Maruo, H. [Osaka Univ., Osaka (Japan)

    1994-08-05

    Shape variable laser beam shaping optics for which linear polarized beam is utilized is applied to the hardening of carbon steel by CO2 laser beam to analyze the absorptivity. In addition, linear polarized beam is irradiated to inclined materials for laser hardening to analyze the depth of hardening and the distribution of temperature. The absorptivity of random polarized beam by the bare specimens is as low as 20%. It is as high as above 40% with the graphite coated specimen, but is nearly constant with no dependence on the angle of incidence. The absorptivity in p-polarization increases with the increase in the angle of incidence. When linear polarized beam is used, the total efficiency of the bare specimen becomes high by about 1.5 times that of the graphite coated specimen subjected to random polarized beam. Hardening of bear material by laser beam is quite possible when p-polarization is employed. An approximation equation is derived with which the temperature distribution and hardened depth can be obtained easily if beam distribution and absorptivity are given, and it is applied to the evaluation of laser hardening of inclined specimens using linear polarized beam. 22 refs., 11 figs., 1 tab.

  10. High-fidelity artifact correction for cone-beam CT imaging of the brain

    Science.gov (United States)

    Sisniega, A.; Zbijewski, W.; Xu, J.; Dang, H.; Stayman, J. W.; Yorkston, J.; Aygun, N.; Koliatsos, V.; Siewerdsen, J. H.

    2015-02-01

    CT is the frontline imaging modality for diagnosis of acute traumatic brain injury (TBI), involving the detection of fresh blood in the brain (contrast of 30-50 HU, detail size down to 1 mm) in a non-contrast-enhanced exam. A dedicated point-of-care imaging system based on cone-beam CT (CBCT) could benefit early detection of TBI and improve direction to appropriate therapy. However, flat-panel detector (FPD) CBCT is challenged by artifacts that degrade contrast resolution and limit application in soft-tissue imaging. We present and evaluate a fairly comprehensive framework for artifact correction to enable soft-tissue brain imaging with FPD CBCT. The framework includes a fast Monte Carlo (MC)-based scatter estimation method complemented by corrections for detector lag, veiling glare, and beam hardening. The fast MC scatter estimation combines GPU acceleration, variance reduction, and simulation with a low number of photon histories and reduced number of projection angles (sparse MC) augmented by kernel de-noising to yield a runtime of ~4 min per scan. Scatter correction is combined with two-pass beam hardening correction. Detector lag correction is based on temporal deconvolution of the measured lag response function. The effects of detector veiling glare are reduced by deconvolution of the glare response function representing the long range tails of the detector point-spread function. The performance of the correction framework is quantified in experiments using a realistic head phantom on a testbench for FPD CBCT. Uncorrected reconstructions were non-diagnostic for soft-tissue imaging tasks in the brain. After processing with the artifact correction framework, image uniformity was substantially improved, and artifacts were reduced to a level that enabled visualization of ~3 mm simulated bleeds throughout the brain. Non-uniformity (cupping) was reduced by a factor of 5, and contrast of simulated bleeds was improved from ~7 to 49.7 HU, in good agreement

  11. Beam hardening artifacts by dental implants: Comparison of cone-beam and 64-slice computed tomography scanners

    Directory of Open Access Journals (Sweden)

    Farzad Esmaeili

    2013-01-01

    Full Text Available Background: Cone beam computed tomography (CBCT is an alternative to a computed tomography (CT scan, which is appropriate for a wide range of craniomaxillofacial indications. The long-term use of metallic materials in dentistry means that artifacts caused by metallic restorations in the oral cavity should be taken into account when utilizing CBCT and CT scanners. The aim of this study was to quantitatively compare the beam hardening artifacts produced by dental implants between CBCT and a 64-Slice CT scanner. Materials and Methods: In this descriptive study , an implant drilling model similar to the human mandible was used in the present study. The implants (Dentis were placed in the canine, premolar and molar areas. Three series of scans were provided from the implant areas using Somatom Sensation 64-slice and NewTom VGi (CBCT CT scanners. Identical images were evaluated by three radiologists. The artifacts in each image were determined based on pre-determined criteria. Kruskal-Wallis test was used to compare mean values; Mann-Whitney U test was used for two-by-two comparisons when there was a statistical significance ( P < 0.05. Results: The images of the two scanners had similar resolutions in axial sections ( P = 0.299. In coronal sections, there were significant differences in the resolutions of the images produced by the two scanners ( P < 0.001, with a higher resolution in the images produced by NewTom VGi scanner. On the whole, there were significant differences between the resolutions of the images produced by the two CT scanners ( P < 0.001, with higher resolution in the images produced by NewTom VGi scanner in comparison to those of Somatom Sensation. Conclusion: Given the high quality of the images produced by NewTom VGi and the lower costs in comparison to CT, the use of the images of this scanner in dental procedures is recommended, especially in patients with extensive restorations, multiple prostheses and previous implants.

  12. Effect of beam hardening on transmural myocardial perfusion quantification in myocardial CT imaging

    Science.gov (United States)

    Fahmi, Rachid; Eck, Brendan L.; Levi, Jacob; Fares, Anas; Wu, Hao; Vembar, Mani; Dhanantwari, Amar; Bezerra, Hiram G.; Wilson, David L.

    2016-03-01

    The detection of subendocardial ischemia exhibiting an abnormal transmural perfusion gradient (TPG) may help identify ischemic conditions due to micro-vascular dysfunction. We evaluated the effect of beam hardening (BH) artifacts on TPG quantification using myocardial CT perfusion (CTP). We used a prototype spectral detector CT scanner (Philips Healthcare) to acquire dynamic myocardial CTP scans in a porcine ischemia model with partial occlusion of the left anterior descending (LAD) coronary artery guided by pressure wire-derived fractional flow reserve (FFR) measurements. Conventional 120 kVp and 70 keV projection-based mono-energetic images were reconstructed from the same projection data and used to compute myocardial blood flow (MBF) using the Johnson-Wilson model. Under moderate LAD occlusion (FFR~0.7), we used three 5 mm short axis slices and divided the myocardium into three LAD segments and three remote segments. For each slice and each segment, we characterized TPG as the mean "endo-to-epi" transmural flow ratio (TFR). BH-induced hypoenhancement on the ischemic anterior wall at 120 kVp resulted in significantly lower mean TFR value as compared to the 70 keV TFR value (0.29+/-0.01 vs. 0.55+/-0.01 pmeasured between 120 kVp and 70 keV mean TFR values on segments moderately affected or unaffected by BH. In the entire ischemic LAD territory, 120 kVp mean endocardial flow was significantly reduced as compared to mean epicardial flow (15.80+/-10.98 vs. 40.85+/-23.44 ml/min/100g; pBH was effectively minimized resulting in mean endocardial MBF of 40.85+/-15.3407 ml/min/100g vs. 74.09+/-5.07 ml/min/100g (p=0.0054) in the epicardium. We also found that BH artifact in the conventional 120 kVp images resulted in falsely reduced MBF measurements even under non-ischemic conditions.

  13. Focussed ion beam nanotomography reveals the 3D morphology of different solid phases in hardened cement pastes.

    Science.gov (United States)

    Trtik, P; Münch, B; Gasser, P; Leemann, A; Loser, R; Wepf, R; Lura, P

    2011-03-01

    Due to the development of integrated low-keV back-scattered electron detectors, it has become possible in focussed ion beam nanotomography to segment not only solid matter and porosity of hardened cement paste, but also to distinguish different phases within the solid matter. This paper illustrates a method that combines two different approaches for improving the contrast between different phases in the solid matrix of a cement paste. The first approach is based on the application of a specially developed 3D diffusion filter. The second approach is based on a modified data-acquisition procedure during focussed ion beam nanotomography. A pair of electron images is acquired for each slice in the focussed ion beam nanotomography dataset. The first image is captured immediately after ion beam milling; the second image is taken after a prolonged exposure to electron beam scanning. The acquisition of complementary focussed ion beam nanotomography datasets and processing the images with a 3D anisotropic diffusion filter allows distinguishing different phases within the hydration products.

  14. Quantitative analysis of artifacts in 4D DSA: the relative contributions of beam hardening and scatter to vessel dropout behind highly attenuating structures

    Science.gov (United States)

    Hermus, James; Szczykutowicz, Timothy P.; Strother, Charles M.; Mistretta, Charles

    2014-03-01

    When performing Computed Tomographic (CT) image reconstruction on digital subtraction angiography (DSA) projections, loss of vessel contrast has been observed behind highly attenuating anatomy, such as dental implants and large contrast filled aneurysms. Because this typically occurs only in a limited range of projection angles, the observed contrast time course can potentially be altered. In this work, we have developed a model for acquiring DSA projections that models both the polychromatic nature of the x-ray spectrum and the x-ray scattering interactions to investigate this problem. In our simulation framework, scatter and beam hardening contributions to vessel dropout can be analyzed separately. We constructed digital phantoms with large clearly defined regions containing iodine contrast, bone, soft issue, titanium (dental implants) or combinations of these materials. As the regions containing the materials were large and rectangular, when the phantoms were forward projected, the projections contained uniform regions of interest (ROI) and enabled accurate vessel dropout analysis. Two phantom models were used, one to model the case of a vessel behind a large contrast filled aneurysm and the other to model a vessel behind a dental implant. Cases in which both beam hardening and scatter were turned off, only scatter was turned on, only beam hardening was turned on, and both scatter and beam hardening were turned on, were simulated for both phantom models. The analysis of this data showed that the contrast degradation is primarily due to scatter. When analyzing the aneurysm case, 90.25% of the vessel contrast was lost in the polychromatic scatter image, however only 50.5% of the vessel contrast was lost in the beam hardening only image. When analyzing the teeth case, 44.2% of the vessel contrast was lost in the polychromatic scatter image and only 26.2% of the vessel contrast was lost in the beam hardening only image.

  15. Beam dynamics in rf guns and emittance correction techniques

    Science.gov (United States)

    Serafini, Luca

    1994-02-01

    In this paper we present a general review of beam dynamics in a laser-driven rf gun. The peculiarity of such an accelerating structure versus other conventional multi-cell linac structures is underlined on the basis of the Panofsky-Wenzel theorem, which is found to give a theoretical background for the well known Kim's model. A basic explanation for some proposed methods to correct rf induced emittance growth is also derived from the theorem. We also present three emittance correction techniques for the recovery of space-charge induced emittance growth, namely the optimum distributed disk-like bunch technique, the use of rf spatial harmonics to correct spherical aberration induced by space charge forces and the technique of emittance filtering by clipping the electron beam. The expected performances regarding the beam quality achievable with different techniques, as predicted by scaling laws and simulations, are analyzed, and, where available, compared to experimental results.

  16. Correction of beam-beam effects in luminosity measurement in the forward region at CLIC

    CERN Document Server

    Lukic, Strahinja

    2013-01-01

    Procedures for correcting the beam-beam effects in luminosity measurement at CLIC at 3 TeV CM energy are described and tested using Monte Carlo simulations: -> Correction of the angular counting loss due to the combined Beamstrahlung and initial-state radiation (ISR) effects, based on the reconstructed velocity of the collision frame of the Bhabha scattering. -> Deconvolution of the luminosity spectrum distortion due to the ISR emission. -> Correction of the counting bias due to the finite calorimeter energy resolution. All procedures were tested by simulation. Bhabha events were generated using BHLUMI, and used in Guinea-PIG to simulate the outgoing momenta of Bhabha particles in the bunch collisions at CLIC. Residual uncertainties after correction are listed in a table in the conclusions. The beam-beam related systematic counting uncertainty in the luminosity peak can be reduced to the order of permille.

  17. Correction of beam-beam effects in luminosity measurement in the forward region at CLIC

    CERN Document Server

    Lukic, Strahinja

    2013-01-01

    Procedures for correcting the beam-beam effects in luminosity measurement at CLIC at 3 TeV CM energy are described and tested using Monte Carlo simulations: - Correction of the angular counting loss due to the combined Beamstrahlung and initial-state radiation (ISR) effects, based on the reconstructed velocity of the collision frame of the Bhabha scattering. - Deconvolution of the luminosity spectrum distortion due to the ISR emission. - Correction of the counting bias due to the finite calorimeter energy resolution. All procedures were tested by simulation. Bhabha events were generated using BHLUMI, and used in Guinea-PIG to simulate the outgoing momenta of Bhabha particles in the bunch collisions at CLIC. Residual uncertainties after correction are listed in a table in the conclusions. The beam-beam related systematic counting uncertainty in the luminosity peak can be reduced to the order of permille.

  18. Impact properties and hardening behavior of laser and electron-beam welds of V-4Cr-4Ti

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H.M.; Strain, R.V.; Tsai, H.C.; Park, J.H.; Smith, D.L. [Argonne National Lab., IL (United States)

    1996-10-01

    The authors are conducting a program to develop an optimal laser welding procedure that can be applied to large-scale fusion-reactor structural components to be fabricated from vanadium-base alloys. Results of initial investigation of mechanical properties and hardening behavior of laser and electron-beam (EB) welds of the production-scale heat of V-4Cr-4Ti (500-kg Heat 832665) in as-welded and postwelding heat-treated (PWHT) conditions are presented in this paper. The laser weld was produced in air using a 6-kW continuous CO{sub 2} laser at a welding speed of {approx}45 mm/s. Microhardness of the laser welds was somewhat higher than that of the base metal, which was annealed at a nominal temperature of {approx}1050{degrees}C for 2 h in the factory. In spite of the moderate hardening, ductile-brittle transition temperatures (DBTTs) of the initial laser ({approx}80{degrees}C) and EB ({approx}30{degrees}C) welds were significantly higher than that of the base metal ({approx}{minus}170{degrees}C). However, excellent impact properties, with DBTT < {minus}80{degrees}C and similar to those of the base metal, could be restored in both the laser and EB welds by postwelding annealing at 1000{degrees}C for 1 h in vacuum.

  19. Grain refinement, hardening and metastable phase formation by high current pulsed electron beam (HCPEB) treatment under heating and melting modes

    Energy Technology Data Exchange (ETDEWEB)

    Grosdidier, T., E-mail: Thierry.grosdidier@univ-metz.f [Laboratoire d' Etude des Textures et Applications aux Materiaux (LETAM, CNRS 3143), Universite Paul Verlaine-Metz, Ile du Saulcy, 57045 Metz (France); Lab of Materials Modification by Laser, Ion and Electron Beams and School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Zou, J.X. [Laboratoire d' Etude des Textures et Applications aux Materiaux (LETAM, CNRS 3143), Universite Paul Verlaine-Metz, Ile du Saulcy, 57045 Metz (France); Bolle, B. [Laboratoire d' Etude des Textures et Applications aux Materiaux (LETAM, CNRS 3143), ENIM, Ile du Saulcy, 57045 Metz (France); Hao, S.Z.; Dong, C. [Lab of Materials Modification by Laser, Ion and Electron Beams and School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China)

    2010-08-15

    High current pulsed electron beam is a recently developed technique for surface modification. The pulsed electron irradiation introduces concentrated energy depositions in the thin surface layer of the treated materials, giving rise to an extremely fast heating and subsequent rapid cooling of the surface together with the formation of dynamic stress waves. Improved surface properties (hardness, corrosion resistance) can be obtained under the 'melting' mode when the top surface is melted and rapidly solidified (10{sup 7} K/s). In steels, this is essentially the result of nanostructures formed from the highly undercooled melt, melt surface purification, strain hardening induced by the thermal stress waves as well as metastable phase selections in the rapidly solidified melted layers. The use of the 'heating' mode is less conventional, combining effects of the heavy deformation and recrystallization/recovery mechanisms. A detailed analysis of a FeAl alloy demonstrates grain size refinement, hardening, solid-state enhanced diffusion and texture modification without modification of the surface geometry.

  20. [Hardening of dental instruments].

    Science.gov (United States)

    Gerasev, G P

    1981-01-01

    The possibility of prolonging the service life of stomatological instruments by the local hardening of their working parts is discussed. Such hardening should be achieved by using hard and wear-resistant materials. The examples of hardening dental elevators and hard-alloy dental drills are given. New trends in the local hardening of instruments are the treatment of their working parts with laser beams, the application of coating on their surface by the gas-detonation method. The results of research work and trials are presented.

  1. Efficient, radiation-hardened, 400- and 800-keV neutral-beam injection systems

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, O.A.; Cooper, W.S.; Fink, J.A.; Goldberg, D.A.; Ruby, L.; Soroka, L.; Tanabe, J.

    1983-04-01

    We present designs for two negative-ion based neutral beam lines with reactor-level power output. Both beam lines make use of such technologically advanced features as high-current-density surface-conversion ion sources, transverse-field-focussing (TFF) acceleration and transport, and laser photodetachment. For the second of these designs, we also presented detailed beam and vacuum calculations, as well as a brief description of a proof-of-principle test system currently under development.

  2. Atmospheric Error Correction of the Laser Beam Ranging

    Directory of Open Access Journals (Sweden)

    J. Saydi

    2014-01-01

    Full Text Available Atmospheric models based on surface measurements of pressure, temperature, and relative humidity have been used to increase the laser ranging accuracy by ray tracing. Atmospheric refraction can cause significant errors in laser ranging systems. Through the present research, the atmospheric effects on the laser beam were investigated by using the principles of laser ranging. Atmospheric correction was calculated for 0.532, 1.3, and 10.6 micron wavelengths through the weather conditions of Tehran, Isfahan, and Bushehr in Iran since March 2012 to March 2013. Through the present research the atmospheric correction was computed for meteorological data in base of monthly mean. Of course, the meteorological data were received from meteorological stations in Tehran, Isfahan, and Bushehr. Atmospheric correction was calculated for 11, 100, and 200 kilometers laser beam propagations under 30°, 60°, and 90° rising angles for each propagation. The results of the study showed that in the same months and beam emission angles, the atmospheric correction was most accurate for 10.6 micron wavelength. The laser ranging error was decreased by increasing the laser emission angle. The atmospheric correction with two Marini-Murray and Mendes-Pavlis models for 0.532 nm was compared.

  3. Implementing the complete beam hardening effect of the bowtie filter versus scaling beam intensities: effects on dosimetric applications in computed tomography.

    Science.gov (United States)

    Lopez-Rendon, Xochitl; Zhang, Guozhi; Bosmans, Hilde; Oyen, Raymond; Zanca, Federica

    2014-10-01

    The bowtie filter is an essential element of computed tomography scanners. Implementation of this filter in a Monte Carlo dosimetry platform can be based on Turner's method, which describes how to measure the filter thickness and relate the x-ray beam as a function of bowtie angle to the central beam. In that application, the beam hardening is accounted for by means of weighting factors that are associated to the photons according to their position (fan angle) and energy. We assessed an alternative approximation in which the photon spectrum is given a fan angle-dependent scaling factor. The aim of our investigation was to evaluate the effects on dose accuracy estimation when using the gold standard bowtie filter method versus a beam scaling approximation method. In particular, we wanted to assess the percentage dose differences between the two methods for several water thicknesses representative for different patients of different body mass index. The largest percentage differences were found for the thickest part of the bowtie filter and increased with patient size.

  4. Prospects for electron beam aberration correction using sculpted phase masks

    Energy Technology Data Exchange (ETDEWEB)

    Shiloh, Roy, E-mail: royshilo@post.tau.ac.il; Remez, Roei; Arie, Ady

    2016-04-15

    Technological advances in fabrication methods allowed the microscopy community to take incremental steps towards perfecting the electron microscope, and magnetic lens design in particular. Still, state of the art aberration-corrected microscopes are yet 20–30 times shy of the theoretical electron diffraction limit. Moreover, these microscopes consume significant physical space and are very expensive. Here, we show how a thin, sculpted membrane is used as a phase-mask to induce specific aberrations into an electron beam probe in a standard high resolution TEM. In particular, we experimentally demonstrate beam splitting, two-fold astigmatism, three-fold astigmatism, and spherical aberration. - Highlights: • Thin membranes can be used as aberration correctors in electron columns. • We demonstrate tilt, twofold-, threefold-astigmatism, and spherical aberrations. • Experimental and physical-optics simulation results are in good agreement. • Advantages in cost, size, nonmagnetism, and nearly-arbitrary correction.

  5. Scale factor correction for Gaussian beam truncation in second moment beam radius measurements

    Science.gov (United States)

    Hofer, Lucas R.; Dragone, Rocco V.; MacGregor, Andrew D.

    2017-04-01

    Charged-couple devices (CCD) and complementary metal oxide semiconductor (CMOS) image sensors, in conjunction with the second moment radius analysis method, are effective tools for determining the radius of a laser beam. However, the second moment method heavily weights sensor noise, which must be dealt with using a thresholding algorithm and a software aperture. While these noise reduction methods lower the random error due to noise, they simultaneously generate systematic error by truncating the Gaussian beam's edges. A scale factor that is invariant to beam ellipticity and corrects for the truncation of the Gaussian beam due to thresholding and the software aperture has been derived. In particular, simulations showed an order of magnitude reduction in measured beam radius error when using the scale factor-irrespective of beam ellipticity-and further testing with real beam data demonstrated that radii corrected by the scale factor are independent of the noise reduction parameters. Thus, through use of the scale factor, the accuracy of beam radius measurements made with a CCD or CMOS sensor and the second moment are significantly improved.

  6. A novel method for beam misalignment correction of an accelerated charged-particle beam

    Energy Technology Data Exchange (ETDEWEB)

    Rahighi, J. [Van de Graaff Laboratory, Nuclear Science Research School, NSTRI, P.O. Box 14395-836, Tehran, Iran (Iran, Islamic Republic of)]. E-mail: jrahighi@aeoi.org.ir; Lamehi-Rachti, M. [Van de Graaff Laboratory, Nuclear Science Research School, NSTRI, P.O. Box 14395-836, Tehran, Iran (Iran); Kakuee, O.R. [Van de Graaff Laboratory, Nuclear Science Research School, NSTRI, P.O. Box 14395-836, Tehran, Iran (Iran)

    2007-07-21

    A novel method is presented for misalignment correction of an accelerated charged-particle beam in a typical charged-particle scattering experiment employing large-solid-angle detectors. The correction method is based on Rutherford scattering and is quite straightforward to apply when a large solid angle and axially symmetric detection system is used in the experimental measurements. A Monte Carlo computer program and its formalism based on Rutherford scattering cross-section have been described. The program is used to calculate beam misalignment offline after data collection is completed. The method has been successfully applied to correct for misalignment calculated to be typically of the order of a few mm in a {sup 6}He radioactive beam of 27 MeV total energy emerging from a cyclotron and produced via {sup 7}Li(p,2p){sup 6}He reaction.

  7. Prospects for electron beam aberration correction using sculpted phase masks.

    Science.gov (United States)

    Shiloh, Roy; Remez, Roei; Arie, Ady

    2016-04-01

    Technological advances in fabrication methods allowed the microscopy community to take incremental steps towards perfecting the electron microscope, and magnetic lens design in particular. Still, state of the art aberration-corrected microscopes are yet 20-30 times shy of the theoretical electron diffraction limit. Moreover, these microscopes consume significant physical space and are very expensive. Here, we show how a thin, sculpted membrane is used as a phase-mask to induce specific aberrations into an electron beam probe in a standard high resolution TEM. In particular, we experimentally demonstrate beam splitting, two-fold astigmatism, three-fold astigmatism, and spherical aberration. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. The SPS beam ins-rumentation and closed orbit correction

    CERN Document Server

    Bossart, Rudolf; Burnod, L; Chapman-Hatchett, A; D'Amico, T E; Mills, P

    1977-01-01

    For the running-in and the operation of a large accelerator like the SPS, the beam instrumentation plays a prominent part. Though limiting the beam detectors to where they are strictly necessary, their number is still considerable, leading to a large amount of data to be treated simultaneously. To do this efficiently, hardware and software are equally important. The type of detectors is determined by their function, intensity, position, profile, loss, etc... whereas the type of associated electronics and acquisition systems is restricted to a minimum for simplicity, production cost, easy maintenance and fast data treatment. The performance of the main types of detectors is summarised giving some particularities of their hardware and software with some emphasis on the closed orbit measurement and correction system. (6 refs).

  9. Evaluation of external beam hardening filters on image quality of computed tomography and single photon emission computed tomography/computed tomography.

    Science.gov (United States)

    Rana, Nivedita; Rawat, Dinesh; Parmar, Madan; Dhawan, Devinder Kumar; Bhati, Ashok Kumar; Mittal, Bhagwant Rai

    2015-01-01

    This study was undertaken to evaluate the effect of external metal filters on the image quality of computed tomography (CT) and single photon emission computed tomography (SPECT)/CT images. Images of Jaszack phantom filled with water and containing iodine contrast filled syringes were acquired using CT (120 kV, 2.5 mA) component of SPECT/CT system, ensuring fixation of filter on X-ray collimator. Different thickness of filters of Al and Cu (1 mm, 2 mm, 3 mm, and 4 mm) and filter combinations Cu 1 mm, Cu 2 mm, Cu 3 mm each in combination with Al (1 mm, 2 mm, 3 mm, and 4 mm), respectively, were used. All image sets were visually analyzed for streak artifacts and contrast to noise ratio (CNR) was derived. Similar acquisition was done using Philips CT quality control (QC) phantom and CNR were calculated for its lexan, perspex, and teflon inserts. Attenuation corrected SPECT/CT images of Jaszack phantom filled with 444-555 MBq (12-15 mCi) of (99m)Tc were obtained by applying attenuation correction map generated by hardened X-ray beam for different filter combination, on SPECT data. Uniformity, root mean square (rms) and contrast were calculated in all image sets. Less streak artifacts at iodine water interface were observed in images acquired using external filters as compared to those without a filter. CNR for syringes, spheres, and inserts of Philips CT QC phantom was almost similar to Al 2 mm, Al 3 mm, and without the use of filters. CNR decreased with increasing copper thickness and other filter combinations. Uniformity and rms were lower, and value of contrast was higher for SPECT/CT images when CT was acquired with Al 2 mm and 3 mm filter than for images acquired without a filter. The study suggests that for Infinia Hawkeye 4, SPECT/CT system, Al 2 mm, and 3 mm are the optimum filters for improving image quality of SPECT/CT images of Jaszack or Philips CT QC phantom keeping other parameters of CT constant.

  10. Evaluation and Correction of the Non-linear Distortion of CEBAF Beam Position Monitors

    Energy Technology Data Exchange (ETDEWEB)

    M. Spata, T.L. Allison, K.E. Cole, J. Musson, J. Yan

    2011-09-01

    The beam position monitors at CEBAF have four antenna style pickups that are used to measure the location of the beam. There is a strong nonlinear response when the beam is far from the electrical center of the device. In order to conduct beam experiments at large orbit excitation we need to correct for this nonlinearity. The correction algorithm is presented and compared to measurements from our stretched wire BPM test stand.

  11. Correction of the Long-Range Beam-Beam Effect in LHC using Electro-Magnetic Lenses

    CERN Document Server

    Koutchouk, Jean-Pierre

    2001-01-01

    The beams in LHC collide head-on in at most four experimental points. Due to the small bunch spacing, the beams experience more than one hundred 'near-misses' on either side of the collision points. The transverse beam separation at these places, limited by the quadrupole aperture, is in the range of 7 to 13 sigma. The non-linear part of these 'long-range' interactions appears to be the dominant mechanism for beam blow-up or beam loss in simulation. A simple non-linear model of the long-range interactions can be devised. It shows that the latter may be locally corrected with good accuracy using wires as correcting lenses. The non-linearity measured by the tune footprint is reduced by one order of magnitude. Pulsing the correcting lenses cancels the so-called PACMAN effect.

  12. 浅谈激光束表面相变硬化技术%On Laser Beam Surface Phase Transformation Hardening Technology

    Institute of Scientific and Technical Information of China (English)

    李义田

    2013-01-01

    激光束表面相变硬化技术是激光热处理中研究最早、最多、进展最快、应用最广的一种新工艺,适用于大多数材料和不同形状零件的不同部位,可提高零件的耐磨性和疲劳强度。本文简要介绍了激光束表面相变硬化技术的原理以及应用。%Laser beam surface phase transformation hardening technology is the first and most researched new laser heat treatment technique with rapid progress and the widest application. It is suitable for most materials and different parts of different shaped components. It can improve the abrasive resistance and fatigue strength of the components. This article mainly introduces the principle and application of laser beam surface phase transformation hardening technology.

  13. Vibrational Energy Flow Analysis of Corrected Flexural Waves in Timoshenko Beam – Part II: Application to Coupled Timoshenko Beams

    OpenAIRE

    2006-01-01

    This paper presents the methodology for the energy flow analysis of coupled Timoshenko beam structures and various numerical applications to verify the developed methodology. To extend the application of the energy flow model for corrected flexural waves in the Timoshenko beam, which is developed in the other companion paper, to coupled structures, the wave transmission analyses of general coupled Timoshenko beam systems are performed. First, power transmission and reflection coefficients for...

  14. Vibrational Energy Flow Analysis of Corrected Flexural Waves in Timoshenko Beam – Part II: Application to Coupled Timoshenko Beams

    Directory of Open Access Journals (Sweden)

    Young-Ho Park

    2006-01-01

    Full Text Available This paper presents the methodology for the energy flow analysis of coupled Timoshenko beam structures and various numerical applications to verify the developed methodology. To extend the application of the energy flow model for corrected flexural waves in the Timoshenko beam, which is developed in the other companion paper, to coupled structures, the wave transmission analyses of general coupled Timoshenko beam systems are performed. First, power transmission and reflection coefficients for all kinds of propagating waves in the general, coupled Timoshenko beam structures are derived by the wave transmission approach. In numerical applications, the energy flow solutions using the derived coefficients agree well with the classical solutions for various exciting frequencies, damping loss factors, and coupled Timoshenko beam structures. Additionally, the numerical results for the Timoshenko beam are compared with those for the Euler-Bernoulli beam.

  15. Detector to detector corrections: a comprehensive experimental study of detector specific correction factors for beam output measurements for small radiotherapy beams

    DEFF Research Database (Denmark)

    Azangwe, Godfrey; Grochowska, Paulina; Georg, Dietmar

    2014-01-01

    Purpose: The aim of the present study is to provide a comprehensive set of detector specific correction factors for beam output measurements for small beams, for a wide range of real time and passive detectors. The detector specific correction factors determined in this study may be potentially u...... measurements, the authors recommend the use of detectors that require relatively little correction, such as unshielded diodes, diamond detectors or microchambers, and solid state detectors such as alanine, TLD, Al2O3:C, or scintillators.......Purpose: The aim of the present study is to provide a comprehensive set of detector specific correction factors for beam output measurements for small beams, for a wide range of real time and passive detectors. The detector specific correction factors determined in this study may be potentially...... useful as a reference data set for small beam dosimetry measurements. Methods: Dose response of passive and real time detectors was investigated for small field sizes shaped with a micromultileaf collimator ranging from 0.6 × 0.6 cm2 to 4.2 × 4.2 cm2 and the measurements were extended to larger fields...

  16. Radiative corrections to chargino production in electron-positron collisions with polarized beams

    Energy Technology Data Exchange (ETDEWEB)

    Diaz, Marco A.; King, Stephen F.; Ross, Douglas A.

    2001-07-01

    We study radiative corrections to chargino production at linear colliders with polarized electron beams. We calculate the one-loop corrected cross sections for polarized electon beams due to three families of quarks and squarks, working in the {ovr MS} scheme, extending our previous calculation of the unpolarized cross section with one-loop corrections due to the third family of quarks and squarks. In some cases we find rather large corrections to the tree-level cross sections. For example, for the case of right-handed polarized electrons and large tan{beta} the corrections can be of order 30%, allowing sensitivity to the squark mass parameters.

  17. Improved Scatter Correction in X-Ray Cone Beam CT with Moving Beam Stop Array Using Johns' Equation

    CERN Document Server

    Yan, Hao; Tang, Shaojie; Xu, Qiong

    2014-01-01

    In this paper, an improved scatter correction with moving beam stop array (BSA) for x-ray cone beam (CB) CT is proposed. Firstly, correlation between neighboring CB views is deduced based on John's Equation. Then, correlation-based algorithm is presented to complement the incomplete views by using the redundancy (over-determined information) in CB projections. Finally, combining the algorithm with scatter correction method using moving BSA, where part of primary radiation is blocked and incomplete projections are acquired, an improved correction method is proposed. Effectiveness and robustness is validated by Monte Carlo (MC) simulation with EGSnrc on humanoid phantom.

  18. Mechanisms of hardening, wear and corrosion improvement of 316 L stainless steel by low energy high current pulsed electron beam surface treatment

    Energy Technology Data Exchange (ETDEWEB)

    Zou, J.X. [Laboratoire d' Etude des Textures et Applications aux Materiaux (LETAM, UMR-CNRS 7078), Universite Paul Verlaine - Metz, Ile du Saulcy, 57045 Metz (France); Shanghai Engineering Research Center of Mg Materials and Applications and School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Key Laboratory of Materials Modification by Laser, Electron and Ion beams, Dalian University of Technology, Dalian 116024 (China); Zhang, K.M. [School of Materials Engineering, Shanghai University of Engineering Science, Shanghai 201620 (China); Hao, S.Z.; Dong, C. [Key Laboratory of Materials Modification by Laser, Electron and Ion beams, Dalian University of Technology, Dalian 116024 (China); Grosdidier, T., E-mail: thierry.grosdidier@univ-metz.f [Laboratoire d' Etude des Textures et Applications aux Materiaux (LETAM, UMR-CNRS 7078), Universite Paul Verlaine - Metz, Ile du Saulcy, 57045 Metz (France); Key Laboratory of Materials Modification by Laser, Electron and Ion beams, Dalian University of Technology, Dalian 116024 (China)

    2010-12-01

    The mechanisms of corrosion and wear improvements by low energy high current pulsed electron beam (LEHCPEB) have been investigated for an AISI 316 L steel. Selective purification followed by epitaxial growth occurred in the top surface melted layer (2-3 {mu}m thick) that was softened by tensile stresses and, to a much lower extent, by lower efficiency of MnS precipitation hardening. Electrochemical impedance spectroscopy and potentiodynamic polarization analyses used to model the corrosion behavior revealed that, while craters initiated at MnS inclusions initially served as pitting sites, the resistance was increased by 3 orders of magnitude after sufficient number of pulses by the formation of a homogeneous covering layer. The wear resistance was effectively improved by sub-surface (over 100 {mu}m) work hardening associated with the combine effect of the quasi-static thermal stress and the thermal stress waves. The overall results demonstrate the potential of the LEHCPEB technique for improving concomitantly the corrosion and wear performances of metallic materials.

  19. Ion recombination correction factors (P(ion)) for Varian TrueBeam high-dose-rate therapy beams.

    Science.gov (United States)

    Kry, Stephen F; Popple, Richard; Molineu, Andrea; Followill, David S

    2012-11-08

    Ion recombination is approximately corrected for in the Task Group 51 protocol by Pion, which is calculated by a two-voltage measurement. This measurement approach may be a poor estimate of the true recombination, particularly if Pion is large (greater than 1.05). Concern exists that Pion in high-dose-per-pulse beams, such as flattening filter free (FFF) beams, may be unacceptably high, rendering the two-voltage measurement technique inappropriate. Therefore, Pion was measured for flattened beams of 6, 10, 15, and 18 MV and for FFF beams of 6 and 10 MV. The values for the FFF beams were verified with 1/V versus 1/Q curves (Jaffé plots). Pion was also measured for electron beams of 6, 12, 16, 18, and 20 MeV on a traditional accelerator, as well as on the high-dose-rate Varian TrueBeam accelerator. The measurements were made at a range of depths and with PTW, NEL, and Exradin Farmer-type chambers. Consistent with the increased dose per pulse, Pion was higher for FFF beams than for flattening filter beams. However, for all beams, measurement locations, and chambers examined, Pion never exceeded 1.018. Additionally, Pion was always within 0.3% of the recombination calculated from the Jaffé plots. We conclude that ion recombination can be adequately accounted for in high-dose-rate FFF beams using Pion determined with the standard two-voltage technique.

  20. Distributed processing (DP) based e-beam lithography simulation with long range correction algorithm in e-beam machine

    Science.gov (United States)

    Ki, Won-Tai; Choi, Ji-Hyeon; Kim, Byung-Gook; Woo, Sang-Gyun; Cho, Han-Ku

    2008-05-01

    As the design rule with wafer process is getting smaller down below 50nm node, the specification of CDs on a mask is getting more tightened. Therefore, more tight and accurate E-Beam Lithography simulation is highly required in these days. However, in reality most of E-Beam simulation cases, there is a trade-off relationship between the accuracy and the simulation speed. Moreover, the necessity of full chip based simulation has been increasing in order to estimate more accurate mask CDs based on real process condition. Therefore, without consideration of long range correction algorithm such as fogging effect and loading effect correction in E-beam machine, it would be impossible and meaningless to pursue the full chip based simulation. In this paper, we introduce a breakthrough method to overcome the obstacles of E-Beam simulation. In-house E-beam simulator, ELIS (E-beam LIthography Simulator), has been upgraded to solve these problems. First, DP (Distributed Processing) strategy was applied to improve calculation speed. Secondly, the long range correction algorithm of E-beam machine was also applied to compute intensity of exposure on a full chip based (Mask). Finally, ELIS-DP has been evaluated possibility of expecting or analyzing CDs on full chip base.

  1. Optics measurement and correction during beam acceleration in the Relativistic Heavy Ion Collider

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.; Marusic, A. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.; Minty, M. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.

    2014-09-09

    To minimize operational complexities, setup of collisions in high energy circular colliders typically involves acceleration with near constant β-functions followed by application of strong focusing quadrupoles at the interaction points (IPs) for the final beta-squeeze. At the Relativistic Heavy Ion Collider (RHIC) beam acceleration and optics squeeze are performed simultaneously. In the past, beam optics correction at RHIC has taken place at injection and at final energy with some interpolation of corrections into the acceleration cycle. Recent measurements of the beam optics during acceleration and squeeze have evidenced significant beta-beats which if corrected could minimize undesirable emittance dilutions and maximize the spin polarization of polarized proton beams by avoidance of higher-order multipole fields sampled by particles within the bunch. In this report the methodology now operational at RHIC for beam optics corrections during acceleration with simultaneous beta-squeeze will be presented together with measurements which conclusively demonstrate the superior beam control. As a valuable by-product, the corrections have minimized the beta-beat at the profile monitors so reducing the dominant error in and providing more precise measurements of the evolution of the beam emittances during acceleration.

  2. Principle of a correction of the long-range beam-beam effect in LHC using electromagnetic lenses

    CERN Document Server

    Koutchouk, Jean-Pierre

    2000-01-01

    Due to the small bunch spacing, the beams in LHC collide not only in the four experimental points but experience more than one hundred 'near-misses'. They occur on either side of the collision points in places where the beam separation is in the range of 7 to 13 sigma. These so-called 'long-range'interactions are more and more recognized to be a drastic mechanism leading to beam blow-up or beam loss even-though the tunes of the particles are under control. We show in this note that, contrary to the head-on-beam interaction, a simple non linear model of the long-range interactions can be devised. This model suggests a rather simple correction principle by electromagnetic lenses, basically a wire, which correct with a good accuracy simultaneously the linear and non-linear perturbations. The correction of the average perturbation over all the bunches seems not demanding. An exact correction of the so-called PACMAN bunches may be done at a frequency an order of magnitude lower than the bunch frequency and is bein...

  3. Beam-Based Nonlinear Optics Corrections in Colliders

    CERN Document Server

    Pilat, Fulvia Caterina; Malitsky, Nikolay; Ptitsyn, Vadim

    2005-01-01

    A method has been developed to measure and correct operationally the non-linear effects of the final focusing magnets in colliders, which gives access to the effects of multi-pole errors by applying closed orbit bumps, and analyzing the resulting tune and orbit shifts. This technique has been tested and used during 3 years of RHIC (the Relativistic Heavy Ion Collider at BNL) operations. I will discuss here the theoretical basis of the method, the experimental set-up, the correction results, the present understanding of the machine model, the potential and limitations of the method itself as compared with other non linear correction techniques.

  4. Note on quantitatively correct simulations of the kinetic beam-plasma instability

    CERN Document Server

    Lotov, K V; Mesyats, E A; Snytnikov, A V; Vshivkov, V A

    2014-01-01

    A large number of model particles is shown necessary for quantitatively correct simulations of the kinetic beam-plasma instability with the clouds-in-cells method. The required number of particles scales inversely with the expected growth rate, as in the kinetic regime only a narrow interval of beam velocities is resonant with the wave.

  5. Note on quantitatively correct simulations of the kinetic beam-plasma instability

    Energy Technology Data Exchange (ETDEWEB)

    Lotov, K. V.; Timofeev, I. V. [Budker Institute of Nuclear Physics SB RAS, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 630090 Novosibirsk (Russian Federation); Mesyats, E. A.; Snytnikov, A. V.; Vshivkov, V. A. [Institute of Computational Mathematics and Mathematical Geophysics SB RAS, 630090 Novosibirsk (Russian Federation)

    2015-02-15

    A large number of model particles are shown necessary for quantitatively correct simulations of the kinetic beam-plasma instability with the clouds-in-cells method. The required number of particles scales inversely with the expected growth rate, as only a narrow interval of beam velocities is resonant with the wave in the kinetic regime.

  6. Space Charge Correction on Emittance Measurement of Low Energy Electron Beams

    Energy Technology Data Exchange (ETDEWEB)

    Treado, Colleen J.; /Massachusetts U., Amherst

    2012-09-07

    The goal of any particle accelerator is to optimize the transport of a charged particle beam along a set path by confining the beam to a small region close to the design trajectory and directing it accurately along the beamline. To do so in the simplest fashion, accelerators use a system of magnets that exert approximately linear electromagnetic forces on the charged beam. These electromagnets bend the beam along the desired path, in the case of bending magnets, and constrain the beam to the desired area through alternating focusing and defocusing effects, in the case of quadrupole magnets. We can model the transport of such a beam through transfer matrices representing the actions of the various beamline elements. However, space charge effects, produced from self electric fields within the beam, defocus the beam and must be accounted for in the calculation of beam emittance. We present below the preliminary results of a MATLAB code built to model the transport of a charged particle beam through an accelerator and measure the emittance under the influence of space charge effects. We demonstrate the method of correctly calculating the emittance of a beam under space charge effects using a least square fit to determine the initial properties of the beam given the beam size measured at a specific point after transport.

  7. Polarity correction factor for flattening filter free photon beams in several cylindrical ionization chambers.

    Science.gov (United States)

    Ogata, Toshiyuki; Uehara, Kazuyuki; Nakayama, Masao; Tsudou, Shinji; Masutani, Takashi; Okayama, Takanobu

    2016-07-01

    In this study, we aimed to compare the polarity correction factor in ionization chambers for flattening filter free (FFF) photon beams and flattening filter (FF) beams. Measurements were performed with both 6 and 10 MV FFF and FF beams. Five commercial ionization chambers were evaluated: PTW TN30013; IBA Dosimetry CC01, CC04, and CC13; and Exradin A12S. Except for the CC01 ionization chamber, the other four chambers showed less than a 0.3 % difference in the polarity effect between the FFF and the FF beams. The CC01 chamber showed a strong field-size-dependence, unlike the other chambers. The polarity effect for all chambers with FFF beams did not change with the dose rate. Except in the case of the CC01 chamber, the difference in the polarity effect between FFF and FF beams was not significant.

  8. Feedback phase correction of Bessel beams in confocal line light-sheet microscopy: a simulation study.

    Science.gov (United States)

    Moosavi, S Hoda; Gohn-Kreuz, Cristian; Rohrbach, Alexander

    2013-08-10

    Confocal line detection has been shown to improve contrast in light-sheet-based microscopy especially when illuminating the sample by Bessel beams. Besides their self-reconstructing capability, the stability in propagation direction of Bessel beams allows to block the unwanted emission light from the Bessel beam's ring system. However, due to phase aberrations induced especially at the border of the specimen, Bessel beams may not propagate along lines parallel to the slit detector. Here we present a concept of how to correct the phase of each incident Bessel beam such that the efficiency of confocal line detection is improved by up to 200%-300%. The applicability of the method is verified by the results obtained from numerical simulations based on the beam propagation method.

  9. Corrected knife-edge-based reconstruction of tightly focused higher order beams

    CERN Document Server

    Orlov, S; Marchenko, P; Banzer, P; Leuchs, G

    2016-01-01

    The knife-edge method is an established technique for profiling of even tightly focused light beams. However the straightforward implementation of this method fails if the materials and geometry of the knife-edges are not chosen carefully or in particular if knife-edges are used that are made of pure materials. In these cases artifacts are introduced in the shape and position of the reconstructed beam profile due to the interaction of the light beam under study with the knife. Hence, corrections to the standard knife-edge evaluation method are required. Here we investigate the knife-edge method for highly focused radially and azimuthally polarized beams and their linearly polarized constituents. We introduce relative shifts for those constituents and report on the consistency with the case of a linearly polarized Gaussian beam. An adapted knife-edge reconstruction technique is presented and proof-of-concept tests demonstrating the reconstruction of beam profiles are shown.

  10. Correction of Magnetic Optics and Beam Trajectory Using LOCO Based Algorithm with Expanded Experimental Data Sets

    Energy Technology Data Exchange (ETDEWEB)

    Romanov, A.; Edstrom, D.; Emanov, F. A.; Koop, I. A.; Perevedentsev, E. A.; Rogovsky, Yu. A.; Shwartz, D. B.; Valishev, A.

    2017-03-28

    Precise beam based measurement and correction of magnetic optics is essential for the successful operation of accelerators. The LOCO algorithm is a proven and reliable tool, which in some situations can be improved by using a broader class of experimental data. The standard data sets for LOCO include the closed orbit responses to dipole corrector variation, dispersion, and betatron tunes. This paper discusses the benefits from augmenting the data with four additional classes of experimental data: the beam shape measured with beam profile monitors; responses of closed orbit bumps to focusing field variations; betatron tune responses to focusing field variations; BPM-to-BPM betatron phase advances and beta functions in BPMs from turn-by-turn coordinates of kicked beam. All of the described features were implemented in the Sixdsimulation software that was used to correct the optics of the VEPP-2000 collider, the VEPP-5 injector booster ring, and the FAST linac.

  11. Sextupole correction of the longitudinal transport of relativistic beams in dispersionless translating sections

    Directory of Open Access Journals (Sweden)

    R. J. England

    2005-01-01

    Full Text Available We examine the use of sextupole magnets to correct nonlinearities in the longitudinal phase space transformation of a relativistic beam of charged particles in a dispersionless translating section, or dogleg. Through heuristic analytical arguments and examples derived from recent experimental efforts, augmented by simulations using the particle tracking codes PARMELA and ELEGANT, sextupole corrections are found to be effective in optimizing the use of such structures for beam compression or for shaping the current profile of the beam, by manipulation of the second-order longitudinal dispersion. Recent experimental evidence of the use of sextupoles to manipulate second-order horizontal and longitudinal dispersion of the beam is presented. The theoretical and experimental results indicate that these manipulations can be used to create an electron bunch with a current profile having a long ramp followed by a sharp cutoff, which is optimal for driving large-amplitude wake fields in a plasma wake field accelerator.

  12. Chromatic effects in beam wander correction for free-space quantum communications

    CERN Document Server

    Carrasco-Casado, Alberto; Fernandez, Veronica

    2016-01-01

    Beam wander caused by atmospheric turbulence can significantly degrade the performance of horizontal free-space quantum communication links. Classical beam wander correction techniques cannot be applied due to the stronger requirements of transmitting single photons. One strategy to overcome this limitation consists in using a separate wavelength from that of the quantum signal to analyze the beam wander and use this information for its correction. For this strategy to work adequately, both wavelengths should be affected equally by atmospheric turbulence, i.e. no chromatic effects should be originated from beam wander. In this letter, a series of experiments are performed to prove that this is the case for {\\lambda} ~ 850 nm as the quantum signal and {\\lambda} ~ 1550 nm as the tracking signal of a quantum communication system.

  13. Beam-Based Error Identification and Correction Methods for Particle Accelerators

    CERN Document Server

    AUTHOR|(SzGeCERN)692826; Tomas, Rogelio; Nilsson, Thomas

    2014-06-10

    Modern particle accelerators have tight tolerances on the acceptable deviation from their desired machine parameters. The control of the parameters is of crucial importance for safe machine operation and performance. This thesis focuses on beam-based methods and algorithms to identify and correct errors in particle accelerators. The optics measurements and corrections of the Large Hadron Collider (LHC), which resulted in an unprecedented low β-beat for a hadron collider is described. The transverse coupling is another parameter which is of importance to control. Improvement in the reconstruction of the coupling from turn-by-turn data has resulted in a significant decrease of the measurement uncertainty. An automatic coupling correction method, which is based on the injected beam oscillations, has been successfully used in normal operation of the LHC. Furthermore, a new method to measure and correct chromatic coupling that was applied to the LHC, is described. It resulted in a decrease of the chromatic coupli...

  14. Reduction of CT beam hardening artefacts of ethylene vinyl alcohol copolymer by variation of the tantalum content: evaluation in a standardized aortic endoleak phantom

    Energy Technology Data Exchange (ETDEWEB)

    Treitl, Karla M.; Scherr, Michael; Foerth, Monika; Braun, Franziska; Maxien, Daniel; Treitl, Marcus [Hospitals of the Ludwig-Maximilians-University of Munich, Institute for Clinical Radiology, Munich (Germany)

    2014-10-16

    Our aim was to develop an aortic stent graft phantom to simulate endoleak treatment and to find a tantalum content (TC) of ethylene-vinyl-alcohol-copolymer that causes fewer computed tomography (CT) beam hardening artefacts, but still allows for fluoroscopic visualization. Ethylene-vinyl-alcohol-copolymer specimens of different TC (10-50 %, and 100 %) were injected in an aortic phantom bearing a stent graft and endoleak cavities with simulated re-perfusion. Fluoroscopic visibility of the ethylene-vinyl-alcohol-copolymer specimens was analyzed. In addition, six radiologists analyzed endoleak visibility, and artefact intensity of ethylene-vinyl-alcohol-copolymer in CT. Reduction of TC significantly decreased CT artefact intensity of ethylene-vinyl-alcohol-copolymer and increased visibility of endoleak re-perfusion (p < 0.000). It also significantly decreased fluoroscopic visibility of ethylene-vinyl-alcohol-copolymer (R = 0.883, p ≤ 0.01), and increased the active embolic volumes prior to visualization (Δ ≥ 40 μl). Ethylene-vinyl-alcohol-copolymer specimens with a TC of 45-50 % exhibited reasonable visibility, a low active embolic volume and a tolerable CT artefact intensity. The developed aortic stent graft phantom allows for a reproducible simulation of embolization of endoleaks. The data suggest a reduction of the TC of ethylene-vinyl-alcohol-copolymer to 45 -50 % of the original, to interfere less with diagnostic imaging in follow-up CT examinations, while still allowing for fluoroscopic visualization. (orig.)

  15. Correction of beam errors in high power laser diode bars and stacks.

    Science.gov (United States)

    Monjardin, J F; Nowak, K M; Baker, H J; Hall, D R

    2006-09-01

    The beam errors of an 11 bar laser diode stack fitted with fast-axis collimator lenses have been corrected by a single refractive plate, produced by laser cutting and polishing. The so-called smile effect is virtually eliminated and collimator aberration greatly reduced, improving the fast-axis beam quality of each bar by a factor of up to 5. The single corrector plate for the whole stack ensures that the radiation from all the laser emitters is parallel to a common axis. Beam-pointing errors of the bars have been reduced to below 0.7 mrad.

  16. Detector to detector corrections: A comprehensive experimental study of detector specific correction factors for beam output measurements for small radiotherapy beams

    Energy Technology Data Exchange (ETDEWEB)

    Azangwe, Godfrey, E-mail: g.azangwe@iaea.org; Grochowska, Paulina; Izewska, Joanna; Meghzifene, Ahmed [International Atomic Energy Agency, Vienna International Centre, PO Box 100, 1400 Vienna (Austria); Georg, Dietmar; Hopfgartner, Johannes; Lechner, Wolfgang [Department of Radiation Oncology, Medical University Vienna/AKH Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria and Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University Vienna, Vienna, Währinger Gürtel 18-20, A-1090 Vienna (Austria); Andersen, Claus E.; Beierholm, Anders R.; Helt-Hansen, Jakob [Center for Nuclear Technologies, Technical University of Denmark, Risø Campus, DK-4000 Roskilde (Denmark); Mizuno, Hideyuki; Fukumura, Akifumi [National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba-shi 263-8555 (Japan); Yajima, Kaori [Association for Nuclear Technology in Medicine, 7-16, Nihonbashikodenmacho, chuou-ku, Tokyo 103-0001 (Japan); Gouldstone, Clare; Sharpe, Peter [National Physical Laboratory, Acoustics and Ionising Radiation Division, Teddington TW11 0LW (United Kingdom); Palmans, Hugo [National Physical Laboratory, Acoustics and Ionising Radiation Division, Teddington TW11 0LW, United Kingdom and EBG MedAustron GmbH, Medical Physics Department, A-2700 Wiener Neustadt (Austria)

    2014-07-15

    Purpose: The aim of the present study is to provide a comprehensive set of detector specific correction factors for beam output measurements for small beams, for a wide range of real time and passive detectors. The detector specific correction factors determined in this study may be potentially useful as a reference data set for small beam dosimetry measurements. Methods: Dose response of passive and real time detectors was investigated for small field sizes shaped with a micromultileaf collimator ranging from 0.6 × 0.6 cm{sup 2} to 4.2 × 4.2 cm{sup 2} and the measurements were extended to larger fields of up to 10 × 10 cm{sup 2}. Measurements were performed at 5 cm depth, in a 6 MV photon beam. Detectors used included alanine, thermoluminescent dosimeters (TLDs), stereotactic diode, electron diode, photon diode, radiophotoluminescent dosimeters (RPLDs), radioluminescence detector based on carbon-doped aluminium oxide (Al{sub 2}O{sub 3}:C), organic plastic scintillators, diamond detectors, liquid filled ion chamber, and a range of small volume air filled ionization chambers (volumes ranging from 0.002 cm{sup 3} to 0.3 cm{sup 3}). All detector measurements were corrected for volume averaging effect and compared with dose ratios determined from alanine to derive a detector correction factors that account for beam perturbation related to nonwater equivalence of the detector materials. Results: For the detectors used in this study, volume averaging corrections ranged from unity for the smallest detectors such as the diodes, 1.148 for the 0.14 cm{sup 3} air filled ionization chamber and were as high as 1.924 for the 0.3 cm{sup 3} ionization chamber. After applying volume averaging corrections, the detector readings were consistent among themselves and with alanine measurements for several small detectors but they differed for larger detectors, in particular for some small ionization chambers with volumes larger than 0.1 cm{sup 3}. Conclusions: The results demonstrate

  17. Process for hardening the surface of polymers

    Science.gov (United States)

    Mansur, Louis K.; Lee, Eal H.

    1992-01-01

    Hard surfaced polymers and the method for making them is generally described. Polymers are subjected to simultaneous multiple ion beam bombardment, that results in a hardening of the surface and improved wear resistance.

  18. Analysis of active closed cross-section slender beams based on asymptotically correct thin-wall beam theory

    Science.gov (United States)

    Khouli, F.; Langlois, R. G.; Afagh, F. F.

    2007-02-01

    An asymptotically correct theory for multi-cell thin-wall anisotropic slender beams that includes the shell bending strain measures is extended to include embedded active fibre composites (AFCs). A closed-form solution of the asymptotically correct cross-sectional actuation force and moments is obtained. Active thin-wall beam theories found in the literature neglect the shell bending strains, which lead to incorrect predictions for certain cross-sections, while the theory presented is shown to overcome this shortcoming. The theory is implemented and verified against single-cell examples that were solved using the University of Michigan/Variational Beam Sectional Analysis (UM/VABS) software. The stiffness constants and the actuation vector are obtained for two-cell and three-cell active cross-sections. The theory is argued to be reliable for efficient initial design analysis and interdisciplinary parametric or optimization studies of thin-wall closed cross-section slender beams with no initial twist or obliqueness.

  19. Determination of ion recombination correction factors for a liquid ionization chamber in megavoltage photon beams

    Science.gov (United States)

    Choi, Sang Hyoun; Kim, Kum-Bae; Ji, Young Hoon; Kim, Chan Hyeong; Kim, Seonghoon; Huh, Hyun Do

    2015-05-01

    The aim of this study is to determine the ion recombination correction factor for a liquid ionization chamber in a high energy photon beam by using our experimental method. The ion recombination correction factors were determined by using our experimental method and were compared with theoretical and experimental methods proposed by using the theoretical method (Greening, Johansson) and the two-dose rate method in a cobalt beam and a high energy photon beam. In order to apply the liquid ionization chamber in a reference and small field dosimetry, we acquired the absorbed dose to water correction coefficient, the beam quality correction factor, and the influence quantities for the microLion chamber according to the TRS-398 protocol and applied the results to a high energy photon beam used in clinical fields. As a result, our experimental method for ion recombination in a cobalt beam agreed with the results from the heoretical method (Greening theory) better than it did with the results from the two-dose rate method. For high energy photon beams, the two-dose rate and our experimental methods were in good agreement, less than 2% deviation, while the theoretical general collection efficiency (Johansson et al.) deviated greatly from the experimental values. When we applied the factors for the absorbed dose to water measurement, the absorbed dose to water for the microLion chamber was in good agreement, within 1%, compared with the values for the PTW 30013 chamber in 6 and 10 MV Clinac iX and 6 and 15 MV Oncor impression. With these results, not only can the microLion ionization chamber be used to measure the absorbed dose to water in a reference condition, it can also be used to a the chamber for small, non-standard field dosimetry.

  20. Correcting the beam centroid motion in an induction accelerator and reducing the beam breakup instability

    Directory of Open Access Journals (Sweden)

    J. E. Coleman

    2014-09-01

    Full Text Available Axial beam centroid and beam breakup (BBU measurements were conducted on an 80 ns FWHM, intense relativistic electron bunch with an injected energy of 3.8 MV and current of 2.9 kA. The intense relativistic electron bunch is accelerated and transported through a nested solenoid and ferrite induction core lattice consisting of 64 elements, exiting the accelerator with a nominal energy of 19.8 MeV. The principal objective of these experiments is to quantify the coupling of the beam centroid motion to the BBU instability and validate the theory of this coupling for the first time. Time resolved centroid measurements indicate a reduction in the BBU amplitude, ⟨ξ⟩, of 19% and a reduction in the BBU growth rate (Γ of 4% by reducing beam centroid misalignments ∼50% throughout the accelerator. An investigation into the contribution of the misaligned elements is made. An alignment algorithm is presented in addition to a qualitative comparison of experimental and calculated results which include axial beam centroid oscillations, BBU amplitude, and growth with different dipole steering.

  1. Corrections for shear and rotatory inertia on flexural vibrations of beams

    NARCIS (Netherlands)

    Nederveen, C.J.; Schwarzl, F.R.

    1964-01-01

    Different correction formulae for the influence of shear and rotatory inertia on flexural vibrations of freely supported beams are compared with the exact solution. It appears that in most cases a simple formula is sufficient because of the appearance of a constant which is not accurately known, viz

  2. Correction of linear-array lidar intensity data using an optimal beam shaping approach

    Science.gov (United States)

    Xu, Fan; Wang, Yuanqing; Yang, Xingyu; Zhang, Bingqing; Li, Fenfang

    2016-08-01

    The linear-array lidar has been recently developed and applied for its superiority of vertically non-scanning, large field of view, high sensitivity and high precision. The beam shaper is the key component for the linear-array detection. However, the traditional beam shaping approaches can hardly satisfy our requirement for obtaining unbiased and complete backscattered intensity data. The required beam distribution should roughly be oblate U-shaped rather than Gaussian or uniform. Thus, an optimal beam shaping approach is proposed in this paper. By employing a pair of conical lenses and a cylindrical lens behind the beam expander, the expanded Gaussian laser was shaped to a line-shaped beam whose intensity distribution is more consistent with the required distribution. To provide a better fit to the requirement, off-axis method is adopted. The design of the optimal beam shaping module is mathematically explained and the experimental verification of the module performance is also presented in this paper. The experimental results indicate that the optimal beam shaping approach can effectively correct the intensity image and provide ~30% gain of detection area over traditional approach, thus improving the imaging quality of linear-array lidar.

  3. Robust scatter correction method for cone-beam CT using an interlacing-slit plate

    CERN Document Server

    Huang, Kuidong; Zhang, Dinghua; Zhang, Hua; Shi, Wenlong

    2015-01-01

    Cone-beam computed tomography (CBCT) has been widely used in medical imaging and industrial nondestructive testing, but the presence of scattered radiation will cause significant reduction of image quality. In this article, a robust scatter correction method for CBCT using an interlacing-slit plate (ISP) is carried out for convenient practice. Firstly, a Gaussian filtering method is proposed to compensate the missing data of the inner scatter image, and simultaneously avoid too-large values of calculated inner scatter and smooth the inner scatter field. Secondly, an interlacing-slit scan without detector gain correction is carried out to enhance the practicality and convenience of the scatter correction method. Finally, a denoising step for scatter-corrected projection images is added in the process flow to control the noise amplification. The experimental results show that the improved method can not only make the scatter correction more robust and convenient, but also achieve a good quality of scatter-corre...

  4. Ion beam machining error control and correction for small scale optics.

    Science.gov (United States)

    Xie, Xuhui; Zhou, Lin; Dai, Yifan; Li, Shengyi

    2011-09-20

    Ion beam figuring (IBF) technology for small scale optical components is discussed. Since the small removal function can be obtained in IBF, it makes computer-controlled optical surfacing technology possible to machine precision centimeter- or millimeter-scale optical components deterministically. Using a small ion beam to machine small optical components, there are some key problems, such as small ion beam positioning on the optical surface, material removal rate, ion beam scanning pitch control on the optical surface, and so on, that must be seriously considered. The main reasons for the problems are that it is more sensitive to the above problems than a big ion beam because of its small beam diameter and lower material ratio. In this paper, we discuss these problems and their influences in machining small optical components in detail. Based on the identification-compensation principle, an iterative machining compensation method is deduced for correcting the positioning error of an ion beam with the material removal rate estimated by a selected optimal scanning pitch. Experiments on ϕ10 mm Zerodur planar and spherical samples are made, and the final surface errors are both smaller than λ/100 measured by a Zygo GPI interferometer.

  5. Aperture correction with an asymmetrically trimmed Gaussian weight in SPECT with a fan-beam collimator.

    Science.gov (United States)

    Kamiya, Ryo; Ogawa, Koichi

    2013-08-01

    The aim of the study is to improve the spatial resolution of SPECT images acquired with a fan-beam collimator. The aperture angle of a hole in the fan-beam collimator depends on the position of the collimator. To correct the aperture effect in an iterative image reconstruction, an asymmetrically trimmed Gaussian weight was used for a model. To confirm the validity of our method, point source phantoms and brain phantom were used in the simulation, and we applied the method to the clinical data. The results of the simulation showed that the spatial resolution of point sources improved from about 6 to 2 pixels full width at half maximum, and the corrected point sources were isotropic. The results of the simulation with the brain phantom showed that our proposed method could improve the spatial resolution of the phantom, and our method was effective for different fan-beam collimators with different focal lengths. The results of clinical data showed that the quality of the reconstructed image was improved with our proposed method. Our proposed aperture correction method with the asymmetrically trimmed Gaussian weighting function was effective in improving the spatial resolution of SPECT images acquired with the fan-beam collimator.

  6. Fluence correction factor for graphite calorimetry in a clinical high-energy carbon-ion beam

    Science.gov (United States)

    Lourenço, A.; Thomas, R.; Homer, M.; Bouchard, H.; Rossomme, S.; Renaud, J.; Kanai, T.; Royle, G.; Palmans, H.

    2017-04-01

    The aim of this work is to develop and adapt a formalism to determine absorbed dose to water from graphite calorimetry measurements in carbon-ion beams. Fluence correction factors, {{k}\\text{fl}} , needed when using a graphite calorimeter to derive dose to water, were determined in a clinical high-energy carbon-ion beam. Measurements were performed in a 290 MeV/n carbon-ion beam with a field size of 11  ×  11 cm2, without modulation. In order to sample the beam, a plane-parallel Roos ionization chamber was chosen for its small collecting volume in comparison with the field size. Experimental information on fluence corrections was obtained from depth-dose measurements in water. This procedure was repeated with graphite plates in front of the water phantom. Fluence corrections were also obtained with Monte Carlo simulations through the implementation of three methods based on (i) the fluence distributions differential in energy, (ii) a ratio of calculated doses in water and graphite at equivalent depths and (iii) simulations of the experimental setup. The {{k}\\text{fl}} term increased in depth from 1.00 at the entrance toward 1.02 at a depth near the Bragg peak, and the average difference between experimental and numerical simulations was about 0.13%. Compared to proton beams, there was no reduction of the {{k}\\text{fl}} due to alpha particles because the secondary particle spectrum is dominated by projectile fragmentation. By developing a practical dose conversion technique, this work contributes to improving the determination of absolute dose to water from graphite calorimetry in carbon-ion beams.

  7. Orbit error correction on the high energy beam transport line at the KHIMA accelerator system

    Science.gov (United States)

    Park, Chawon; Yim, Heejoong; Hahn, Garam; An, Dong Hyun

    2016-09-01

    For the purpose of treatment of various cancers and medical research, a synchrotron based medical machine has been developed under the Korea Heavy Ion Medical Accelerator (KHIMA) project and is scheduled for use to treat patient at the beginning of 2018. The KHIMA synchrotron is designed to accelerate and extract carbon ion (proton) beams with various energies from 110 to 430 MeV/u (60 to 230 MeV). Studies on the lattice design and beam optics for the High Energy Beam Transport (HEBT) line at the KHIMA accelerator system have been carried out using the WinAgile and the MAD-X codes. Because magnetic field errors and misalignments introduce deviations from the design parameters, these error sources should be treated explicitly, and the sensitivity of the machine's lattice to different individual error sources should be considered. Various types of errors, both static and dynamic, have been taken into account and have been consequentially corrected with a dedicated correction algorithm by using the MAD-X program. Based on the error analysis, the optimized correction setup is decided, and the specifications for the correcting magnets of the HEBT lines are determined.

  8. Improving the quality of radiographic images acquired with conical radiation beams through divergence correction and filtering

    Science.gov (United States)

    Silvani, M. I.; Almeida, G. L.; Latini, R. M.; Bellido, A. V. B.; Souza, E. S.; Lopes, R. T.

    2015-07-01

    Earlier works have shown the feasibility to correct the deformation of the attenuation map in radiographs acquired with conical radiation beams provided that the inspected object could be expressed into analytical geometry terms. This correction reduces the contribution of the main object in the radiograph, allowing thus the visualization of its otherwise concealed heterogeneities. However, the non-punctual character of the source demanded a cumbersome trial-and-error approach in order to determine the proper correction parameters for the algorithm. Within this frame, this work addresses the improvement of radiographs of specially tailored test-objects acquired with a conical beam through correction of its divergence by using the information contained in the image itself. The corrected images have afterwards undergone a filtration in the frequency domain aiming at the reduction of statistical fluctuation and noise by using a 2D Fourier transform. All radiographs have been acquired using 165Dy and 198Au gamma-ray sources produced at the Argonauta research reactor in Institutode Engenharia Nuclear - CNEN, and an X-ray sensitive imaging plate as detector. The processed images exhibit features otherwise invisible in the original ones. Their processing by conventional histogram equalization carried out for comparison purposes did not succeed to detect those features.

  9. X-Ray Scatter Correction on Soft Tissue Images for Portable Cone Beam CT

    OpenAIRE

    Sorapong Aootaphao; Saowapak S. Thongvigitmanee; Jartuwat Rajruangrabin; Chalinee Thanasupsombat; Tanapon Srivongsa; Pairash Thajchayapong

    2016-01-01

    Soft tissue images from portable cone beam computed tomography (CBCT) scanners can be used for diagnosis and detection of tumor, cancer, intracerebral hemorrhage, and so forth. Due to large field of view, X-ray scattering which is the main cause of artifacts degrades image quality, such as cupping artifacts, CT number inaccuracy, and low contrast, especially on soft tissue images. In this work, we propose the X-ray scatter correction method for improving soft tissue images. The X-ray scatter ...

  10. Uniform longitudinal beam profiles in the Fermilab Recycler using adaptive rf correction

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Martin; Broemmelsiek, Daniel Robert; Chase, Brian; Crisp, James L.; Eddy, Nathan; Joireman, Paul W.; Ng, King Yuen; /Fermilab

    2007-06-01

    The Fermilab Recycler Ring is a permanent magnet based 8 GeV anti-proton storage ring. A wideband RF system, driven with ARB's (ARBitrary waveform generators), allows the system to produce programmable barrier waveforms. Beam current profile distortion was observed, its origin verified both experimentally and theoretically, and an FPGA-based correction system was designed, tested and implemented to level the bunch profile.

  11. Monte Carlo calculation of beam quality correction factors in proton beams using detailed simulation of ionization chambers

    Science.gov (United States)

    Gomà, Carles; Andreo, Pedro; Sempau, Josep

    2016-03-01

    This work calculates beam quality correction factors (k Q ) in monoenergetic proton beams using detailed Monte Carlo simulation of ionization chambers. It uses the Monte Carlo code penh and the electronic stopping powers resulting from the adoption of two different sets of mean excitation energy values for water and graphite: (i) the currently ICRU 37 and ICRU 49 recommended {{I}\\text{w}}=75~\\text{eV} and {{I}\\text{g}}=78~\\text{eV} and (ii) the recently proposed {{I}\\text{w}}=78~\\text{eV} and {{I}\\text{g}}=81.1~\\text{eV} . Twelve different ionization chambers were studied. The k Q factors calculated using the two different sets of I-values were found to agree with each other within 1.6% or better. k Q factors calculated using current ICRU I-values were found to agree within 2.3% or better with the k Q factors tabulated in IAEA TRS-398, and within 1% or better with experimental values published in the literature. k Q factors calculated using the new I-values were also found to agree within 1.1% or better with the experimental values. This work concludes that perturbation correction factors in proton beams—currently assumed to be equal to unity—are in fact significantly different from unity for some of the ionization chambers studied.

  12. Line end shortening and application of novel correction algorithms in e-beam direct write

    Science.gov (United States)

    Freitag, Martin; Choi, Kang-Hoon; Gutsch, Manuela; Hohle, Christoph

    2011-03-01

    For the manufacturing of semiconductor technologies following the ITRS roadmap, we will face the nodes well below 32nm half pitch in the next 2~3 years. Despite being able to achieve the required resolution, which is now possible with electron beam direct write variable shaped beam (EBDW VSB) equipment and resists, it becomes critical to precisely reproduce dense line space patterns onto a wafer. This exposed pattern must meet the targets from the layout in both dimensions (horizontally and vertically). For instance, the end of a line must be printed in its entire length to allow a later placed contact to be able to land on it. Up to now, the control of printed patterns such as line ends is achieved by a proximity effect correction (PEC) which is mostly based on a dose modulation. This investigation of the line end shortening (LES) includes multiple novel approaches, also containing an additional geometrical correction, to push the limits of the available data preparation algorithms and the measurement. The designed LES test patterns, which aim to characterize the status of LES in a quick and easy way, were exposed and measured at Fraunhofer Center Nanoelectronic Technologies (CNT) using its state of the art electron beam direct writer and CD-SEM. Simulation and exposure results with the novel LES correction algorithms applied to the test pattern and a large production like pattern in the range of our target CDs in dense line space features smaller than 40nm will be shown.

  13. Feasibility Studies on Underwater Laser Surface Hardening Process

    Directory of Open Access Journals (Sweden)

    Biao Jin

    2015-01-01

    Full Text Available Laser surface hardening process is a very promising hardening method for ferrous and nonferrous alloys where transformations occur during cooling after laser melting in the solid state. This study experimentally characterizes laser surface hardening of tool steel in both water and air. For the underwater operation, laser surface scanning is performed over the tool steel surface which is immersed in water. The laser surface hardening tests are performed with a maximum 200 W fiber laser with a Gaussian distribution of energy in the beam. For the surface hardening, single-track melting experiment which sequentially scans elongated path of single line has been performed. As the hardened depth depends on the thermal conductivity of the material, the surface temperature and the penetration depth may be varied by underwater laser processing. The feasibility of underwater laser surface hardening process is discussed on the basis of average hardness level and hardened bead shape.

  14. A hardenability test proposal

    Energy Technology Data Exchange (ETDEWEB)

    Murthy, N.V.S.N. [Ingersoll-Rand (I) Ltd., Bangalore (India)

    1996-12-31

    A new approach for hardenability evaluation and its application to heat treatable steels will be discussed. This will include an overview and deficiencies of the current methods and discussion on the necessity for a new approach. Hardenability terminology will be expanded to avoid ambiguity and over-simplification as encountered with the current system. A new hardenability definition is proposed. Hardenability specification methods are simplified and rationalized. The new hardenability evaluation system proposed here utilizes a test specimen with varying diameter as an alternative to the cylindrical Jominy hardenability test specimen and is readily applicable to the evaluation of a wide variety of steels with different cross-section sizes.

  15. X-Ray Scatter Correction on Soft Tissue Images for Portable Cone Beam CT

    Directory of Open Access Journals (Sweden)

    Sorapong Aootaphao

    2016-01-01

    Full Text Available Soft tissue images from portable cone beam computed tomography (CBCT scanners can be used for diagnosis and detection of tumor, cancer, intracerebral hemorrhage, and so forth. Due to large field of view, X-ray scattering which is the main cause of artifacts degrades image quality, such as cupping artifacts, CT number inaccuracy, and low contrast, especially on soft tissue images. In this work, we propose the X-ray scatter correction method for improving soft tissue images. The X-ray scatter correction scheme to estimate X-ray scatter signals is based on the deconvolution technique using the maximum likelihood estimation maximization (MLEM method. The scatter kernels are obtained by simulating the PMMA sheet on the Monte Carlo simulation (MCS software. In the experiment, we used the QRM phantom to quantitatively compare with fan-beam CT (FBCT data in terms of CT number values, contrast to noise ratio, cupping artifacts, and low contrast detectability. Moreover, the PH3 angiography phantom was also used to mimic human soft tissues in the brain. The reconstructed images with our proposed scatter correction show significant improvement on image quality. Thus the proposed scatter correction technique has high potential to detect soft tissues in the brain.

  16. Correction of resist heating effect on variable shaped beam mask writer

    Science.gov (United States)

    Nakayamada, Noriaki; Suganuma, Mizuna; Nomura, Haruyuki; Kato, Yasuo; Kamikubo, Takashi; Ogasawara, Munehiro; Zable, Harold; Masuda, Yukihiro; Fujimura, Aki

    2016-04-01

    The specifications for critical dimension (CD) accuracy and line edge roughness are getting tighter to promote every photomask manufacturer to choose electron beam resists of lower sensitivity. When the resist is exposed by too many electrons, it is excessively heated up to have higher sensitivity at a higher temperature, which results in degraded CD uniformity. This effect is called "resist heating effect" and is now the most critical error source in CD control on a variable shaped beam (VSB) mask writer. We have developed an on-tool, real-time correction system for the resist heating effect. The system is composed of correction software based on a simple thermal diffusion model and computational hardware equipped with more than 100 graphical processing unit chips. We have demonstrated that the designed correction accuracy was obtained and the runtime of correction was sufficiently shorter than the writing time. The system is ready to be deployed for our VSB mask writers to retain the writing time as short as possible for lower sensitivity resists by removing the need for increased pass count.

  17. Robust scatter correction method for cone-beam CT using an interlacing-slit plate

    Science.gov (United States)

    Huang, Kui-Dong; Xu, Zhe; Zhang, Ding-Hua; Zhang, Hua; Shi, Wen-Long

    2016-06-01

    Cone-beam computed tomography (CBCT) has been widely used in medical imaging and industrial nondestructive testing, but the presence of scattered radiation will cause significant reduction of image quality. In this article, a robust scatter correction method for CBCT using an interlacing-slit plate (ISP) is carried out for convenient practice. Firstly, a Gaussian filtering method is proposed to compensate the missing data of the inner scatter image, and simultaneously avoid too-large values of calculated inner scatter and smooth the inner scatter field. Secondly, an interlacing-slit scan without detector gain correction is carried out to enhance the practicality and convenience of the scatter correction method. Finally, a denoising step for scatter-corrected projection images is added in the process flow to control the noise amplification The experimental results show that the improved method can not only make the scatter correction more robust and convenient, but also achieve a good quality of scatter-corrected slice images. Supported by National Science and Technology Major Project of the Ministry of Industry and Information Technology of China (2012ZX04007021), Aeronautical Science Fund of China (2014ZE53059), and Fundamental Research Funds for Central Universities of China (3102014KYJD022)

  18. Electron fluence correction factors for various materials in clinical electron beams.

    Science.gov (United States)

    Olivares, M; DeBlois, F; Podgorsak, E B; Seuntjens, J P

    2001-08-01

    Relative to solid water, electron fluence correction factors at the depth of dose maximum in bone, lung, aluminum, and copper for nominal electron beam energies of 9 MeV and 15 MeV of the Clinac 18 accelerator have been determined experimentally and by Monte Carlo calculation. Thermoluminescent dosimeters were used to measure depth doses in these materials. The measured relative dose at dmax in the various materials versus that of solid water, when irradiated with the same number of monitor units, has been used to calculate the ratio of electron fluence for the various materials to that of solid water. The beams of the Clinac 18 were fully characterized using the EGS4/BEAM system. EGSnrc with the relativistic spin option turned on was used to optimize the primary electron energy at the exit window, and to calculate depth doses in the five phantom materials using the optimized phase-space data. Normalizing all depth doses to the dose maximum in solid water stopping power ratio corrected, measured depth doses and calculated depth doses differ by less than +/- 1% at the depth of dose maximum and by less than 4% elsewhere. Monte Carlo calculated ratios of doses in each material to dose in LiF were used to convert the TLD measurements at the dose maximum into dose at the center of the TLD in the phantom material. Fluence perturbation correction factors for a LiF TLD at the depth of dose maximum deduced from these calculations amount to less than 1% for 0.15 mm thick TLDs in low Z materials and are between 1% and 3% for TLDs in Al and Cu phantoms. Electron fluence ratios of the studied materials relative to solid water vary between 0.83+/-0.01 and 1.55+/-0.02 for materials varying in density from 0.27 g/cm3 (lung) to 8.96 g/cm3 (Cu). The difference in electron fluence ratios derived from measurements and calculations ranges from -1.6% to +0.2% at 9 MeV and from -1.9% to +0.2% at 15 MeV and is not significant at the 1sigma level. Excluding the data for Cu, electron

  19. Orbit Error Correction on the High Energy Beam Transport Line at the KHIMA Accelerator System

    CERN Document Server

    Park, Chawon; Hahn, Garam; An, Dong Hyun

    2016-01-01

    For the purpose of treatment of various cancer and medical research, the synchrotron based medical machine under the Korea Heavy Ion Medical Accelerator (KHIMA) project have been conducted and is going to treat the patient at the beginning of 2018. The KHIMA synchrotron is designed to accelerate and extract the carbon ion (proton) beam with various energy range, 110 up to 430 MeV/u (60 up to 230 MeV). A lattice design and beam optics studies for the High Energy Beam Transport (HEBT) line at the KHIMA accelerator system have been carried out with WinAgile and the MAD-X codes. Because the magnetic eld errors and the mis-alignments introduce to the deviations from the design parameters, these error sources should be treated explicitly and the sensitivity of the machine's lattice to di erent individual error sources is considered. Various types of errors which are static and dynamic one have been taken into account and have been consequentially corrected with a dedicated correction algorithm by using the MAD-X pr...

  20. Laser Surface Hardening of 9CrSi Steel

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The effects of laser hardening parameters such as beam power, beam diameter and scanning rate on microstructureand hardness of 9CrSi steel were investigated. The microstructure of the surface layer of 9CrSi steel was changed frompearlite to martensite, retained austenite and carbide by laser hardening. The depth of the hardened layer increasedwith increasing laser energy density and the surface hardeness increased by 3~5 times as high as the untreated steel.The laser hardened surface had good wear resistance due to martensite and carbide in the surface layer. The wearmode at Iow speed was abrasive, while the wear mode at high speed was adhesive.

  1. Diffraction corrections for second harmonic beam fields and effects on the nonlinearity parameter evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Hyun Jo; Cho, Sung Jong; Nam, Ki Woong; Lee, Jang Hyun [Division of Mechanical and Automotive Engineering, Wonkwang University, Iksan (Korea, Republic of)

    2016-04-15

    The nonlinearity parameter is frequently measured as a sensitive indicator in damaged material characterization or tissue harmonic imaging. Several previous studies have employed the plane wave solution, and ignored the effects of beam diffraction when measuring the non-linearity parameter β. This paper presents a multi-Gaussian beam approach to explicitly derive diffraction corrections for fundamental and second harmonics under quasilinear and paraxial approximation. Their effects on the nonlinearity parameter estimation demonstrate complicated dependence of β on the transmitter-receiver geometries, frequency, and propagation distance. The diffraction effects on the non-linearity parameter estimation are important even in the nearfield region. Experiments are performed to show that improved β values can be obtained by considering the diffraction effects.

  2. Correction

    DEFF Research Database (Denmark)

    Pinkevych, Mykola; Cromer, Deborah; Tolstrup, Martin

    2016-01-01

    [This corrects the article DOI: 10.1371/journal.ppat.1005000.][This corrects the article DOI: 10.1371/journal.ppat.1005740.][This corrects the article DOI: 10.1371/journal.ppat.1005679.].......[This corrects the article DOI: 10.1371/journal.ppat.1005000.][This corrects the article DOI: 10.1371/journal.ppat.1005740.][This corrects the article DOI: 10.1371/journal.ppat.1005679.]....

  3. A Model-Based Scatter Artifacts Correction for Cone Beam CT

    CERN Document Server

    Zhao, Wei; Zhu, Jun; Wang, Luyao; Xing, Lei

    2016-01-01

    The purpose of this work is to provide a fast and accurate scatter artifacts correction algorithm for cone beam CT (CBCT) imaging. The method starts with an estimation of coarse scatter profiles for a set of CBCT data in either image domain or projection domain. A denoising algorithm designed specifically for Poisson signals is then applied to derive the final scatter distribution. Qualitative and quantitative evaluations using thorax and abdomen phantoms with Monte Carlo (MC) simulations, experimental Catphan phantom data, and in vivo human data acquired for a clinical image guided radiation therapy were performed. Results show that the proposed algorithm can significantly reduce scatter artifacts and recover the correct HU in either projection domain or image domain. For the MC thorax phantom study, four components segmentation yield the best results, while the results of three components segmentation are still acceptable. For the Catphan phantom data, the mean value over all pixels in the residual image is...

  4. Energy correction for the BGO calorimeter of DAMPE using an electron beam

    Science.gov (United States)

    Li, Zhi-Ying; Zhang, Zhi-Yong; Wei, Yi-Feng; Wang, Chi; Zhang, Yun-Long; Wen, Si-Cheng; Wang, Xiao-Lian; Xu, Zi-Zong; Huang, Guang-Shun

    2016-08-01

    The DArk Matter Particle Explorer is an orbital indirect dark matter search experiment which measures the spectra of photons, electrons and positrons originating from deep space. The electromagnetic calorimeter (ECAL), made of bismuth germinate (BGO), is one of the key sub-detectors of DAMPE, and is designed for energy measurement with a large dynamic range from 5 GeV to 10 TeV. In this paper, methods for energy correction are discussed, in order to reconstruct the primary energy of the incident electrons. Different methods are chosen for the appropriate energy ranges. The correction results of Geant4 simulation and beam test data (at CERN) are presented. Supported by the Chinese 973 Program (2010CB833002), the Strategic Priority Research Program on Space Science of the Chinese Academy of Science (XDA04040202-4) and 100 Talents Program of CAS

  5. Fast Scatter Artifacts Correction for Cone-Beam CT without System Modification and Repeat Scan

    CERN Document Server

    Zhao, Wei; Wang, Luyao

    2015-01-01

    We provide a fast and accurate scatter artifacts correction algorithm for cone beam CT (CBCT) imaging. The method starts with an estimation of coarse scatter profile for a set of CBCT images. A total-variation denoising algorithm designed specifically for Poisson signal is then applied to derive the final scatter distribution. Qualitatively and quantitatively evaluations using Monte Carlo (MC) simulations, experimental CBCT phantom data, and \\emph{in vivo} human data acquired for a clinical image guided radiation therapy were performed. Results show that the proposed algorithm can significantly reduce scatter artifacts and recover the correct HU within either projection domain or image domain. Further test shows the method is robust with respect to segmentation procedure.

  6. SU-E-T-464: On the Equivalence of the Quality Correction Factor for Pencil Beam Scanning Proton Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Sorriaux, J [Center of Molecular Imaging, Radiotherapy and Oncology, Institut de recherche experimentale et Clinique, Universite catholique de Louvain, Avenue Hippocrate 54, 1200 Brussels (Belgium); ICTEAM Institute, Universite catholique de Louvain, 1348 Louvain-la-Neuve (Belgium); Departement of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114 (United States); Paganetti, H; Testa, M; Giantsoudi, D; Schuemann, J [Departement of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114 (United States); Bertrand, D [Ion Beam Applications S.A, Louvain-la-Neuve (Belgium); Orban de Xivry, J. [ICTEAM Institute, Universite catholique de Louvain, 1348 Louvain-la-Neuve (Belgium); Lee, J [Center of Molecular Imaging, Radiotherapy and Oncology, Institut de recherche experimentale et Clinique, Universite catholique de Louvain, Avenue Hippocrate 54, 1200 Brussels (Belgium); ICTEAM Institute, Universite catholique de Louvain, 1348 Louvain-la-Neuve (Belgium); Palmans, H [EBG MedAustron GmbH, Wiener Neustadt (Austria); National Physical Laboratory, Teddington (United Kingdom); Vynckier, S [Departement de radiotherapie, Cliniques Universitaires Saint-Luc, Avenue Hippocrate 54, 1200 Brussels (Belgium); Sterpin, E [Center of Molecular Imaging, Radiotherapy and Oncology, Institut de recherche experimentale et Clinique, Universite catholique de Louvain, Avenue Hippocrate 54, 1200 Brussels (Belgium)

    2014-06-01

    Purpose: In current practice, most proton therapy centers apply IAEA TRS-398 reference dosimetry protocol. Quality correction factors (kQ) take into account in the dose determination process the differences in beam qualities used for calibration unit and for treatment unit. These quality correction factors are valid for specific reference conditions. TRS-398 reference conditions should be achievable in both scattered proton beams (i.e. DS) and scanned proton beams (i.e. PBS). However, it is not a priori clear if TRS-398 kQ data, which are based on Monte Carlo (MC) calculations in scattered beams, can be used for scanned beams. Using TOPAS-Geant4 MC simulations, the study aims to determine whether broad beam quality correction factors calculated in TRS-398 can be directly applied to PBS delivery modality. Methods: As reference conditions, we consider a 10×10×10 cm{sup 3} homogeneous dose distribution delivered by PBS system in a water phantom (32/10 cm range/modulation) and an air cavity placed at the center of the spread-out-Bragg-peak. In order to isolate beam differences, a hypothetical broad beam is simulated. This hypothetical beam reproduces exactly the same range modulation, and uses the same energy layers than the PBS field. Ion chamber responses are computed for the PBS and hypothetical beams and then compared. Results: For an air cavity of 2×2×0.2 cm{sup 3}, the ratio of ion chamber responses for the PBS and hypothetical beam qualities is 0.9991 ± 0.0016. Conclusion: Quality correction factors are insensitive to the delivery pattern of the beam (broad beam or PBS), as long as similar dose distributions are achieved. This investigation, for an air cavity, suggests that broad beam quality correction factors published in TRS-398 can be applied for scanned beams. J. Sorriaux is financially supported by a public-private partnership involving the company Ion Beam Applications (IBA)

  7. Scatter correction, intermediate view estimation and dose characterization in megavoltage cone-beam CT imaging

    Science.gov (United States)

    Sramek, Benjamin Koerner

    The ability to deliver conformal dose distributions in radiation therapy through intensity modulation and the potential for tumor dose escalation to improve treatment outcome has necessitated an increase in localization accuracy of inter- and intra-fractional patient geometry. Megavoltage cone-beam CT imaging using the treatment beam and onboard electronic portal imaging device is one option currently being studied for implementation in image-guided radiation therapy. However, routine clinical use is predicated upon continued improvements in image quality and patient dose delivered during acquisition. The formal statement of hypothesis for this investigation was that the conformity of planned to delivered dose distributions in image-guided radiation therapy could be further enhanced through the application of kilovoltage scatter correction and intermediate view estimation techniques to megavoltage cone-beam CT imaging, and that normalized dose measurements could be acquired and inter-compared between multiple imaging geometries. The specific aims of this investigation were to: (1) incorporate the Feldkamp, Davis and Kress filtered backprojection algorithm into a program to reconstruct a voxelized linear attenuation coefficient dataset from a set of acquired megavoltage cone-beam CT projections, (2) characterize the effects on megavoltage cone-beam CT image quality resulting from the application of Intermediate View Interpolation and Intermediate View Reprojection techniques to limited-projection datasets, (3) incorporate the Scatter and Primary Estimation from Collimator Shadows (SPECS) algorithm into megavoltage cone-beam CT image reconstruction and determine the set of SPECS parameters which maximize image quality and quantitative accuracy, and (4) evaluate the normalized axial dose distributions received during megavoltage cone-beam CT image acquisition using radiochromic film and thermoluminescent dosimeter measurements in anthropomorphic pelvic and head and

  8. Ultrafast cone-beam CT scatter correction with GPU-based Monte Carlo simulation

    Directory of Open Access Journals (Sweden)

    Yuan Xu

    2014-03-01

    Full Text Available Purpose: Scatter artifacts severely degrade image quality of cone-beam CT (CBCT. We present an ultrafast scatter correction framework by using GPU-based Monte Carlo (MC simulation and prior patient CT image, aiming at automatically finish the whole process including both scatter correction and reconstruction within 30 seconds.Methods: The method consists of six steps: 1 FDK reconstruction using raw projection data; 2 Rigid Registration of planning CT to the FDK results; 3 MC scatter calculation at sparse view angles using the planning CT; 4 Interpolation of the calculated scatter signals to other angles; 5 Removal of scatter from the raw projections; 6 FDK reconstruction using the scatter-corrected projections. In addition to using GPU to accelerate MC photon simulations, we also use a small number of photons and a down-sampled CT image in simulation to further reduce computation time. A novel denoising algorithm is used to eliminate MC noise from the simulated scatter images caused by low photon numbers. The method is validated on one simulated head-and-neck case with 364 projection angles.Results: We have examined variation of the scatter signal among projection angles using Fourier analysis. It is found that scatter images at 31 angles are sufficient to restore those at all angles with < 0.1% error. For the simulated patient case with a resolution of 512 × 512 × 100, we simulated 5 × 106 photons per angle. The total computation time is 20.52 seconds on a Nvidia GTX Titan GPU, and the time at each step is 2.53, 0.64, 14.78, 0.13, 0.19, and 2.25 seconds, respectively. The scatter-induced shading/cupping artifacts are substantially reduced, and the average HU error of a region-of-interest is reduced from 75.9 to 19.0 HU.Conclusion: A practical ultrafast MC-based CBCT scatter correction scheme is developed. It accomplished the whole procedure of scatter correction and reconstruction within 30 seconds.----------------------------Cite this

  9. Lorentz factor - Beaming corrected energy/luminosity correlations and GRB central engine models

    Science.gov (United States)

    Yi, Shuang-Xi; Lei, Wei-Hua; Zhang, Bing; Dai, Zi-Gao; Wu, Xue-Feng; Liang, En-Wei

    2017-03-01

    We work on a GRB sample whose initial Lorentz factors (Γ0) are constrained by the afterglow onset method and the jet opening angles (θj) are determined by the jet break time. We confirm the Γ0-Eγ,iso correlation by Liang et al. (2010), and the Γ0-Lγ,iso correlation by Lü et al. (2012). Furthermore, we find correlations between Γ0 and the beaming corrected γ-ray energy (Eγ) and mean γ-ray luminosity (Lγ). By also including the kinetic energy of the afterglow, we find rough correlations (with larger scatter) between Γ0 and the total (γ-ray plus kinetic) energy and the total mean luminosity, both for isotropic values and beaming corrected values: these correlations allow us to test the data with GRB central engine models. Limiting our sample to the GRBs that likely have a black hole central engine, we compare the data with theoretical predictions of two types of jet launching mechanisms from BHs, i.e. the non-magnetized ν ν bar -annihilation mechanism, and the strongly magnetized Blandford-Znajek (BZ) mechanism. We find that the data are more consistent with the latter mechanism, and discuss the implications of our findings for GRB jet composition.

  10. Wavefront-correction for nearly diffraction-limited focusing of dual-color laser beams to high intensities.

    Science.gov (United States)

    Zhao, Baozhen; Zhang, Jun; Chen, Shouyuan; Liu, Cheng; Golovin, Grigory; Banerjee, Sudeep; Brown, Kevin; Mills, Jared; Petersen, Chad; Umstadter, Donald

    2014-11-03

    We demonstrate wavefront correction of terawatt-peak-power laser beams at two distinct and well-separated wavelengths. Simultaneous near diffraction-limited focusability is achieved for both the fundamental (800 nm) and second harmonic (400 nm) of Ti:sapphire-amplified laser light. By comparing the relative effectiveness of various correction loops, the optimal ones are found. Simultaneous correction of both beams of different color relies on the linear proportionality between their wavefront aberrations. This method can enable two-color experiments at relativistic intensities.

  11. Wave-front correction of high-intensity fs laser beams by using closed-loop adaptive optics system

    Institute of Scientific and Technical Information of China (English)

    WANG; Zhaohua; JIN; Zhan; ZHENG; Jiaan; WANG; Peng; WEI; Zh

    2005-01-01

    We developed an adaptive optics system to correct the wave-front distortion of an intense fs laser beam from our multi-TW laser system, Jiguang II. In this paper, the instruments of the adaptive optical system are described and the experimental results of the closed-loop wave-front correction are presented. A distorted laser wave-front of 20 wavelengths of P-V values was corrected to 0.15 wavelength of P-V values. The beam quality of the laser system varies from 3.5 diffraction limit to 1.5 diffraction limit.

  12. Minimal residual cone-beam reconstruction with attenuation correction in SPECT

    Science.gov (United States)

    La, Valérie; Grangeat, Pierre

    1998-04-01

    This paper presents an iterative method based on the minimal residual algorithm for tomographic attenuation compensated reconstruction from attenuated cone-beam projections given the attenuation distribution. Unlike conjugate-gradient based reconstruction techniques, the proposed minimal residual based algorithm solves directly a quasisymmetric linear system, which is a preconditioned system. Thus it avoids the use of normal equations, which improves the convergence rate. Two main contributions are introduced. First, a regularization method is derived for quasisymmetric problems, based on a Tikhonov-Phillips regularization applied to the factorization of the symmetric part of the system matrix. This regularization is made spatially adaptive to avoid smoothing the region of interest. Second, our existing reconstruction algorithm for attenuation correction in parallel-beam geometry is extended to cone-beam geometry. A circular orbit is considered. Two preconditioning operators are proposed: the first one is Grangeat's inversion formula and the second one is Feldkamp's inversion formula. Experimental results obtained on simulated data are presented and the shadow zone effect on attenuated data is illustrated.

  13. CT to Cone-beam CT Deformable Registration With Simultaneous Intensity Correction

    CERN Document Server

    Zhen, Xin; Yan, Hao; Zhou, Linghong; Jia, Xun; Jiang, Steve B

    2012-01-01

    Computed tomography (CT) to cone-beam computed tomography (CBCT) deformable image registration (DIR) is a crucial step in adaptive radiation therapy. Current intensity-based registration algorithms, such as demons, may fail in the context of CT-CBCT DIR because of inconsistent intensities between the two modalities. In this paper, we propose a variant of demons, called Deformation with Intensity Simultaneously Corrected (DISC), to deal with CT-CBCT DIR. DISC distinguishes itself from the original demons algorithm by performing an adaptive intensity correction step on the CBCT image at every iteration step of the demons registration. Specifically, the intensity correction of a voxel in CBCT is achieved by matching the first and the second moments of the voxel intensities inside a patch around the voxel with those on the CT image. It is expected that such a strategy can remove artifacts in the CBCT image, as well as ensuring the intensity consistency between the two modalities. DISC is implemented on computer g...

  14. Aberration-Corrected Electron Beam Lithography at the One Nanometer Length Scale.

    Science.gov (United States)

    Manfrinato, Vitor R; Stein, Aaron; Zhang, Lihua; Nam, Chang-Yong; Yager, Kevin G; Stach, Eric A; Black, Charles T

    2017-08-09

    Patterning materials efficiently at the smallest length scales is a longstanding challenge in nanotechnology. Electron-beam lithography (EBL) is the primary method for patterning arbitrary features, but EBL has not reliably provided sub-4 nm patterns. The few competing techniques that have achieved this resolution are orders of magnitude slower than EBL. In this work, we employed an aberration-corrected scanning transmission electron microscope for lithography to achieve unprecedented resolution. Here we show aberration-corrected EBL at the one nanometer length scale using poly(methyl methacrylate) (PMMA) and have produced both the smallest isolated feature in any conventional resist (1.7 ± 0.5 nm) and the highest density patterns in PMMA (10.7 nm pitch for negative-tone and 17.5 nm pitch for positive-tone PMMA). We also demonstrate pattern transfer from the resist to semiconductor and metallic materials at the sub-5 nm scale. These results indicate that polymer-based nanofabrication can achieve feature sizes comparable to the Kuhn length of PMMA and ten times smaller than its radius of gyration. Use of aberration-corrected EBL will increase the resolution, speed, and complexity in nanomaterial fabrication.

  15. Library-based scatter correction for dedicated cone beam breast CT: a feasibility study

    Science.gov (United States)

    Shi, Linxi; Vedantham, Srinivasan; Karellas, Andrew; Zhu, Lei

    2016-04-01

    Purpose: Scatter errors are detrimental to cone-beam breast CT (CBBCT) accuracy and obscure the visibility of calcifications and soft-tissue lesions. In this work, we propose practical yet effective scatter correction for CBBCT using a library-based method and investigate its feasibility via small-group patient studies. Method: Based on a simplified breast model with varying breast sizes, we generate a scatter library using Monte-Carlo (MC) simulation. Breasts are approximated as semi-ellipsoids with homogeneous glandular/adipose tissue mixture. On each patient CBBCT projection dataset, an initial estimate of scatter distribution is selected from the pre-computed scatter library by measuring the corresponding breast size on raw projections and the glandular fraction on a first-pass CBBCT reconstruction. Then the selected scatter distribution is modified by estimating the spatial translation of the breast between MC simulation and the clinical scan. Scatter correction is finally performed by subtracting the estimated scatter from raw projections. Results: On two sets of clinical patient CBBCT data with different breast sizes, the proposed method effectively reduces cupping artifact and improves the image contrast by an average factor of 2, with an efficient processing time of 200ms per conebeam projection. Conclusion: Compared with existing scatter correction approaches on CBBCT, the proposed library-based method is clinically advantageous in that it requires no additional scans or hardware modifications. As the MC simulations are pre-computed, our method achieves a high computational efficiency on each patient dataset. The library-based method has shown great promise as a practical tool for effective scatter correction on clinical CBBCT.

  16. A model-based scatter artifacts correction for cone beam CT

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Wei; Zhu, Jun; Wang, Luyao [Department of Biomedical Engineering, Huazhong University of Science and Technology, Hubei 430074 (China); Vernekohl, Don; Xing, Lei, E-mail: lei@stanford.edu [Department of Radiation Oncology, Stanford University, Stanford, California 94305 (United States)

    2016-04-15

    Purpose: Due to the increased axial coverage of multislice computed tomography (CT) and the introduction of flat detectors, the size of x-ray illumination fields has grown dramatically, causing an increase in scatter radiation. For CT imaging, scatter is a significant issue that introduces shading artifact, streaks, as well as reduced contrast and Hounsfield Units (HU) accuracy. The purpose of this work is to provide a fast and accurate scatter artifacts correction algorithm for cone beam CT (CBCT) imaging. Methods: The method starts with an estimation of coarse scatter profiles for a set of CBCT data in either image domain or projection domain. A denoising algorithm designed specifically for Poisson signals is then applied to derive the final scatter distribution. Qualitative and quantitative evaluations using thorax and abdomen phantoms with Monte Carlo (MC) simulations, experimental Catphan phantom data, and in vivo human data acquired for a clinical image guided radiation therapy were performed. Scatter correction in both projection domain and image domain was conducted and the influences of segmentation method, mismatched attenuation coefficients, and spectrum model as well as parameter selection were also investigated. Results: Results show that the proposed algorithm can significantly reduce scatter artifacts and recover the correct HU in either projection domain or image domain. For the MC thorax phantom study, four-components segmentation yields the best results, while the results of three-components segmentation are still acceptable. The parameters (iteration number K and weight β) affect the accuracy of the scatter correction and the results get improved as K and β increase. It was found that variations in attenuation coefficient accuracies only slightly impact the performance of the proposed processing. For the Catphan phantom data, the mean value over all pixels in the residual image is reduced from −21.8 to −0.2 HU and 0.7 HU for projection

  17. Scatter correction for cone-beam computed tomography using self-adaptive scatter kernel superposition

    Institute of Scientific and Technical Information of China (English)

    XIE Shi-Peng; LUO Li-Min

    2012-01-01

    The authors propose a combined scatter reduction and correction method to improve image quality in cone beam computed tomography (CBCT).The scatter kernel superposition (SKS) method has been used occasionally in previous studies.However,this method differs in that a scatter detecting blocker (SDB) was used between the X-ray source and the tested object to model the self-adaptive scatter kernel.This study first evaluates the scatter kernel parameters using the SDB,and then isolates the scatter distribution based on the SKS.The quality of image can be improved by removing the scatter distribution.The results show that the method can effectively reduce the scatter artifacts,and increase the image quality.Our approach increases the image contrast and reduces the magnitude of cupping.The accuracy of the SKS technique can be significantly improved in our method by using a self-adaptive scatter kernel.This method is computationally efficient,easy to implement,and provides scatter correction using a single scan acquisition.

  18. Analytic image reconstruction from partial data for a single-scan cone-beam CT with scatter correction

    Energy Technology Data Exchange (ETDEWEB)

    Min, Jonghwan; Pua, Rizza; Cho, Seungryong, E-mail: scho@kaist.ac.kr [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Kim, Insoo; Han, Bumsoo [EB Tech, Co., Ltd., 550 Yongsan-dong, Yuseong-gu, Daejeon 305-500 (Korea, Republic of)

    2015-11-15

    Purpose: A beam-blocker composed of multiple strips is a useful gadget for scatter correction and/or for dose reduction in cone-beam CT (CBCT). However, the use of such a beam-blocker would yield cone-beam data that can be challenging for accurate image reconstruction from a single scan in the filtered-backprojection framework. The focus of the work was to develop an analytic image reconstruction method for CBCT that can be directly applied to partially blocked cone-beam data in conjunction with the scatter correction. Methods: The authors developed a rebinned backprojection-filteration (BPF) algorithm for reconstructing images from the partially blocked cone-beam data in a circular scan. The authors also proposed a beam-blocking geometry considering data redundancy such that an efficient scatter estimate can be acquired and sufficient data for BPF image reconstruction can be secured at the same time from a single scan without using any blocker motion. Additionally, scatter correction method and noise reduction scheme have been developed. The authors have performed both simulation and experimental studies to validate the rebinned BPF algorithm for image reconstruction from partially blocked cone-beam data. Quantitative evaluations of the reconstructed image quality were performed in the experimental studies. Results: The simulation study revealed that the developed reconstruction algorithm successfully reconstructs the images from the partial cone-beam data. In the experimental study, the proposed method effectively corrected for the scatter in each projection and reconstructed scatter-corrected images from a single scan. Reduction of cupping artifacts and an enhancement of the image contrast have been demonstrated. The image contrast has increased by a factor of about 2, and the image accuracy in terms of root-mean-square-error with respect to the fan-beam CT image has increased by more than 30%. Conclusions: The authors have successfully demonstrated that the

  19. Deformable registration of CT and cone-beam CT by local CBCT intensity correction

    Science.gov (United States)

    Park, Seyoun; Plishker, William; Shekhar, Raj; Quon, Harry; Wong, John; Lee, Junghoon

    2015-03-01

    In this paper, we propose a method to accurately register CT to cone-beam CT (CBCT) by iteratively correcting local CBCT intensity. CBCT is a widely used intra-operative imaging modality in image-guided radiotherapy and surgery. A short scan followed by a filtered-backprojection is typically used for CBCT reconstruction. While data on the mid-plane (plane of source-detector rotation) is complete, off-mid-planes undergo different information deficiency and the computed reconstructions are approximate. This causes different reconstruction artifacts at off-mid-planes depending on slice locations, and therefore impedes accurate registration between CT and CBCT. To address this issue, we correct CBCT intensities by matching local intensity histograms slice by slice in conjunction with intensity-based deformable registration. This correction-registration step is repeated until the result image converges. We tested the proposed method on eight head-and-neck cancer cases and compared its performance with state-of-the-art registration methods, Bspline, demons, and optical flow, which are widely used for CT-CBCT registration. Normalized mutual-information (NMI), normalized cross-correlation (NCC), and structural similarity (SSIM) were computed as similarity measures for the performance evaluation. Our method produced overall NMI of 0.59, NCC of 0.96, and SSIM of 0.93, outperforming existing methods by 3.6%, 2.4%, and 2.8% in terms of NMI, NCC, and SSIM scores, respectively. Experimental results show that our method is more consistent and roust than existing algorithms, and also computationally efficient with faster convergence.

  20. Using corrected Cone-Beam CT image for accelerated partial breast irradiation treatment dose verification: the preliminary experience

    OpenAIRE

    Wang, Jiazhou; Hu, Weigang; Cai, Gang; Peng, Jiayuan; Pan, Ziqiang; Guo, Xiaomao; Chen, Jiayi

    2013-01-01

    Background Accurate target localization is mandatory in the accelerated partial breast irradiation (APBI) delivery. Dosimetric verification for positional error will further guarantee the accuracy of treatment delivery. The purpose of this study is to evaluate the clinical feasibility of a cone beam computer tomographic (CBCT) image correction method in APBI. Methods A CBCT image correction method was developed. First, rigid image registration was proceeded for CTs and CBCTs; second, these im...

  1. Assessment of ionization chamber correction factors in photon beams using a time saving strategy with PENELOPE code.

    Science.gov (United States)

    Reis, C Q M; Nicolucci, P

    2016-02-01

    The purpose of this study was to investigate Monte Carlo-based perturbation and beam quality correction factors for ionization chambers in photon beams using a saving time strategy with PENELOPE code. Simulations for calculating absorbed doses to water using full spectra of photon beams impinging the whole water phantom and those using a phase-space file previously stored around the point of interest were performed and compared. The widely used NE2571 ionization chamber was modeled with PENELOPE using data from the literature in order to calculate absorbed doses to the air cavity of the chamber. Absorbed doses to water at reference depth were also calculated for providing the perturbation and beam quality correction factors for that chamber in high energy photon beams. Results obtained in this study show that simulations with phase-space files appropriately stored can be up to ten times shorter than using a full spectrum of photon beams in the input-file. Values of kQ and its components for the NE2571 ionization chamber showed good agreement with published values in the literature and are provided with typical statistical uncertainties of 0.2%. Comparisons to kQ values published in current dosimetry protocols such as the AAPM TG-51 and IAEA TRS-398 showed maximum percentage differences of 0.1% and 0.6% respectively. The proposed strategy presented a significant efficiency gain and can be applied for a variety of ionization chambers and clinical photon beams.

  2. Improvement of the beam quality by chromaticity correction for wavelength shortening in the NIJI-IV FEL

    CERN Document Server

    Sei, N; Ohgaki, H; Litvinenko, V N; Mikado, T; Yamazaki, T

    1999-01-01

    Electron-beam qualities improved by chromaticity correction in the storage ring NIJI-IV were investigated at the beam energy of 309 MeV. Sextupole-quadrupole-sextupole (SQS) magnets, which were installed in all of the short-straight sections in NIJI-IV, perfectly corrected a horizontal and a vertical chromaticity. This improvement suppressed a head-tail instability, so that higher beam current (approx 30 mA) and higher peak-electron density (approx 6x10 sup 1 sup 6 m sup - sup 3) were available for FEL experiments. The maximum FEL gain was estimated to be about 2.5% at a wavelength of 240 nm. The lasing of an FEL around 300 nm was achieved in March 1998, and the lasing of an FEL at around 240 nm was successfully observed in May 1998. The shortest wavelength of FELs with the NIJI-IV FEL system was 228 nm.

  3. Registration concepts for the just-in-time artefact correction by means of virtual computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Kasperl, St.; Franz, M. [Fraunhofer Development Center for X-ray Technology EZRT, a cooperative dept. of the Fraunhofer Institutes IZFP Saarbrucken and IIS Erlangen, Furth (Germany)

    2007-07-01

    This article deals with the enhancement of accuracy in CT by just-in-time correction of artefacts (beam hardening, scattered radiation) caused by the interaction of X-rays with matter. The so called EAR method needs for simulation a registration of the object. Therefore the article presents two different registration concepts. (authors)

  4. Laser Hardening of Metals

    Institute of Scientific and Technical Information of China (English)

    Institute for Laser Physics; V.A.Serebryakov; K.V.Gratzianov; A.S.Eremenko; A.A.Timopheev; SPBSUITMO; M.V.Volkov

    2006-01-01

    Results of experiments on laser hardening of various materials with intensity 109~1010W/cm2 are represented. Nd:glass laser with energy up to 45J with a pulse duration ~30ns was used as a source of ra diation. Comparative researches of the laser peening for the various target areas are fulfilled. Results of laser hardening were determined by the microstructure analysis. The new approach to creation of the industrial laser for peening is discussed.

  5. A two-dose-rate method for general recombination correction for liquid ionization chambers in pulsed beams

    Energy Technology Data Exchange (ETDEWEB)

    Toelli, Heikki; Sjoegren, Rickard; Wendelsten, Mikael, E-mail: heikki.tolli@radfys.umu.s [Department of Radiation Sciences, Radiation Physics, Umeaa University, SE-901 85 Umeaa (Sweden)

    2010-08-07

    The correction for general recombination losses in liquid ionization chambers (LICs) is more complex than that in air-filled ionization chambers. The reason for this is that the saturation charge in LICs, i.e. the charge that escapes initial recombination, depends on the applied voltage. This paper presents a method, based on measurements at two different dose rates in a pulsed beam, for general recombination correction in LICs. The Boag theory for pulsed beams is used and the collection efficiency is determined by numerical methods which are equivalent to the two-voltage method used in dosimetry with air-filled ionization chambers. The method has been tested in experiments in water in a 20 MeV electron beam using two LICs filled with isooctane and tetramethylsilane. The dose per pulse in the electron beam was varied between 0.1 mGy/pulse and 8 mGy/pulse. The relative standard deviations of the collection efficiencies determined with the two-dose-rate method ranged between 0.1% and 1.5%. The dose-rate variations of the general recombination corrected charge measured with the LICs are in excellent agreement with the corresponding values obtained with an air-filled plane parallel ionization chamber.

  6. Theoretical analysis of natural frequency of externally prestressed concrete beam based on rigidity correction

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A dynamic test on externally prestressed simply supported concrete beams separately with three typical types of tendon distributions was conducted. The results show that the natural frequencies of the beams increase with the increase in the prestressing force at the tensioning stage, and the natural frequencies decrease after the cracks occur in the beams. Following the calculation formula of natural frequency of externally prestressed beam, which was reported in a literature, the natural frequencies of the...

  7. SU-E-I-38: Improved Metal Artifact Correction Using Adaptive Dual Energy Calibration

    Energy Technology Data Exchange (ETDEWEB)

    Dong, X; Elder, E; Roper, J; Dhabaan, A [Winship Cancer Institute of Emory University (United States)

    2015-06-15

    Purpose: The empirical dual energy calibration (EDEC) method corrects for beam-hardening artifacts, but shows limited performance on metal artifact correction. In this work, we propose an adaptive dual energy calibration (ADEC) method to correct for metal artifacts. Methods: The empirical dual energy calibration (EDEC) method corrects for beam-hardening artifacts, but shows limited performance on metal artifact correction. In this work, we propose an adaptive dual energy calibration (ADEC) method to correct for metal artifacts. Results: Highly attenuating copper rods cause severe streaking artifacts on standard CT images. EDEC improves the image quality, but cannot eliminate the streaking artifacts. Compared to EDEC, the proposed ADEC method further reduces the streaking resulting from metallic inserts and beam-hardening effects and obtains material decomposition images with significantly improved accuracy. Conclusion: We propose an adaptive dual energy calibration method to correct for metal artifacts. ADEC is evaluated with the Shepp-Logan phantom, and shows superior metal artifact correction performance. In the future, we will further evaluate the performance of the proposed method with phantom and patient data.

  8. Evaluation of ion chamber dependent correction factors for ionisation chamber dosimetry in proton beams using a Monte Carlo method

    Energy Technology Data Exchange (ETDEWEB)

    Palmans, H. [Ghent Univ. (Belgium). Dept. of Biomedical Physics; Verhaegen, F.

    1995-12-01

    In the last decade, several clinical proton beam therapy facilities have been developed. To satisfy the demand for uniformity in clinical (routine) proton beam dosimetry two dosimetry protocols (ECHED and AAPM) have been published. Both protocols neglect the influence of ion chamber dependent parameters on dose determination in proton beams because of the scatter properties of these beams, although the problem has not been studied thoroughly yet. A comparison between water calorimetry and ionisation chamber dosimetry showed a discrepancy of 2.6% between the former method and ionometry following the ECHED protocol. Possibly, a small part of this difference can be attributed to chamber dependent correction factors. Indications for this possibility are found in ionometry measurements. To allow the simulation of complex geometries with different media necessary for the study of those corrections, an existing proton Monte Carlo code (PTRAN, Berger) has been modified. The original code, that applies Mollire`s multiple scattering theory and Vavilov`s energy straggling theory, calculates depth dose profiles, energy distributions and radial distributions for pencil beams in water. Comparisons with measurements and calculations reported in the literature are done to test the program`s accuracy. Preliminary results of the influence of chamber design and chamber materials on dose to water determination are presented.

  9. Determination of the recombination correction for the BIPM parallel-plate ionization chamber type in a pulsed photon beam

    Energy Technology Data Exchange (ETDEWEB)

    Picard, Susanne; Burns, David T. [Bureau International des Poids et Mesures, Pavillon de Breteuil, F92312 Sevres cedex (France); Ostrowsky, Aime [Laboratoire National Henri Becquerel - LNHB, CEA Saclay - 91191 Gif-sur-Yvette Cedex (France)

    2011-09-15

    The correction factor for recombination losses k{sub s} has been determined for the BIPM parallel-plate ionization chamber type in the pulsed photon beam of a clinical linear accelerator. Initial recombination is in agreement with that obtained for the same chamber type in a continuous beam, while linearity in the volume recombination loss is confirmed at dose rates up to 80 pC per pulse, which corresponds to about 0.33 mGy per pulse (or around 2 Gy min{sup -1} at 100 Hz)

  10. Determination of the ion recombination correction factor for intraoperative electron beams

    Energy Technology Data Exchange (ETDEWEB)

    Besheli, Majid Ghorbanpour; Simiantonakis, Ioannis [University Hospital, Duesseldorf (Germany). Dept. of Radiotherapy and Radiation Oncology; Duesseldorf Univ. (Germany). Faculty of Physics/Medical Physics; Zink, Klemens [Univ. of Applied Science (THM), Giessen (Germany). Inst. of Medical Physics and Radiation Protection (IMPS); Budach, Wilfried [University Hospital, Duesseldorf (Germany). Dept. of Radiotherapy and Radiation Oncology

    2016-05-01

    The ion recombination correction factor (k{sub s}) is determined for the Advanced Markus chamber exposed to electron beams produced by a dedicated intraoperative radiation therapy (IORT) accelerator at medium dose-per-pulse values. The authors evaluate five different methods. Three of them are known as Boag's modified expressions, which are based on the two-voltage-analysis method and include the free-electron component. In the fourth method the IAEA TRS-398 protocol is applied, which uses the same two-voltage-analysis method but ignores the free-electron component, and finally the fifth approach is known as the Jaffe plot. k{sub s} values were obtained in the range of 4 mGy/pulse to 42 mGy/pulse and were compared with k{sub s} values determined by means of radiochromic films, which are independent of the dose rate. It was found that k{sub s} values that resulted from the three Boag's modified expressions and the TRS-398 protocol deviated by on average 1.5% and 1.4%, respectively, from the reference k{sub s} values based on film dosimetry. These results are within the estimated relative uncertainty of ±3%. On the other hand, the absolute deviation of each method depends on the dose-per-pulse value at which the method is investigated. In conclusion, in the medium dose-per-pulse range all Boag's modified expressions could be used for k{sub s} determination. Above a dose-per-pulse value of 35 mGy/pulse, the TRS-398 approach should be avoided. At 27 mGy/pulse and a maximum operation voltage of 300 V the k{sub s} value resulting from the Jaffe plot showed a 0.3% deviation from the reference value. More investigation on the Jaffe plot is necessary at higher dose-per-pulse values.

  11. [Theoretical investigation of the saturation correction for ionization chambers irradiated with pulsed beams of arbitrary pulse length].

    Science.gov (United States)

    Karsch, Leonhard; Pawelke, Jörg

    2014-09-01

    In ionization chambers, not all released charge is collected due to the recombination of charge carriers. This effect is taken into account by the saturation correction factor kS. A physical description of the correction factor has been established for pulsed radiation. However, it is only accurate when the pulse length is short compared with the collection time of the ionization chamber. In this paper we develop a description of the saturation correction for radiation pulses of arbitrary length. For this, a system of partial differential equations is solved iteratively. The numerical solutions are verified experimentally for a Roos ionization chamber (PTW TM34001) exposed to a pulsed electron beam. The results of this iterative procedure describe the experimental data well. The calculations are also possible for beam structures which are experimentally hard to get and thereby contribute to a better understanding and correct description of the saturation correction at arbitrary pulse length. Among other things the pulse length dependent distributions of the charge carriers in the ionization chamber is calculated, inclusive of the transition to the conditions prevailing in the case of continuous irradiation. Furthermore is shown that the formula for kS established by Hochhäuser and Balk is applicable even at arbitrary pulse length, if pulse duration dependent effective values are used for the parameters a and p. These effective values have been determined for the Roos chamber at pulse lengths up to 300 μs.

  12. Simultaneous linear optics and coupling correction for storage rings with turn-by-turn beam position monitor data

    CERN Document Server

    Yang, Xi

    2015-01-01

    We propose a method to simultaneously correct linear optics errors and linear coupling for storage rings using turn-by-turn (TbT) beam position monitor (BPM) data. The independent component analysis (ICA) method is used to isolate the betatron normal modes from the measured TbT BPM data. The betatron amplitudes and phase advances of the projections of the normal modes on the horizontal and vertical planes are then extracted, which, combined with dispersion measurement, are used to fit the lattice model. The fitting results are used for lattice correction. The method has been successfully demonstrated on the NSLS-II storage ring.

  13. Correction

    CERN Document Server

    2002-01-01

    Tile Calorimeter modules stored at CERN. The larger modules belong to the Barrel, whereas the smaller ones are for the two Extended Barrels. (The article was about the completion of the 64 modules for one of the latter.) The photo on the first page of the Bulletin n°26/2002, from 24 July 2002, illustrating the article «The ATLAS Tile Calorimeter gets into shape» was published with a wrong caption. We would like to apologise for this mistake and so publish it again with the correct caption.

  14. Novel correction method for X-ray beam energy fluctuation of high energy DR system with a linear detector

    Institute of Scientific and Technical Information of China (English)

    YANG Min; CHEN Hao; MENG Fan-Yong; WEI Dong-Bo

    2011-01-01

    A high energy digital radiography (DR) testing system has generated diverse scientific and technological interest in the field of industrial non-destructive testing.However,due to the limitations of manufacturing technology for accelerators,an energy fluctuation of the X-ray beam exists and leads to bright and dark streak artifacts in the DR image.Here we report the utilization of a new software-based method to correct the fluctuation artifacts.The correction method is performed using a high pass filtering operation to extract the high frequency information that reflects the X-ray beam energy fluctuation,and then subtracting it from the original image.Our experimental results show that this method is able to rule out the artifacts effectively and is readily implemented on a practical scanning system.

  15. Correction of patient positioning errors based on in-line cone beam CTs: clinical implementation and first experiences

    Directory of Open Access Journals (Sweden)

    Häring Peter

    2006-05-01

    Full Text Available Abstract Background The purpose of the study was the clinical implementation of a kV cone beam CT (CBCT for setup correction in radiotherapy. Patients and methods For evaluation of the setup correction workflow, six tumor patients (lung cancer, sacral chordoma, head-and-neck and paraspinal tumor, and two prostate cancer patients were selected. All patients were treated with fractionated stereotactic radiotherapy, five of them with intensity modulated radiotherapy (IMRT. For patient fixation, a scotch cast body frame or a vacuum pillow, each in combination with a scotch cast head mask, were used. The imaging equipment, consisting of an x-ray tube and a flat panel imager (FPI, was attached to a Siemens linear accelerator according to the in-line approach, i.e. with the imaging beam mounted opposite to the treatment beam sharing the same isocenter. For dose delivery, the treatment beam has to traverse the FPI which is mounted in the accessory tray below the multi-leaf collimator. For each patient, a predefined number of imaging projections over a range of at least 200 degrees were acquired. The fast reconstruction of the 3D-CBCT dataset was done with an implementation of the Feldkamp-David-Kress (FDK algorithm. For the registration of the treatment planning CT with the acquired CBCT, an automatic mutual information matcher and manual matching was used. Results and discussion Bony landmarks were easily detected and the table shifts for correction of setup deviations could be automatically calculated in all cases. The image quality was sufficient for a visual comparison of the desired target point with the isocenter visible on the CBCT. Soft tissue contrast was problematic for the prostate of an obese patient, but good in the lung tumor case. The detected maximum setup deviation was 3 mm for patients fixated with the body frame, and 6 mm for patients positioned in the vacuum pillow. Using an action level of 2 mm translational error, a target point

  16. Self-corrected sensors based on atomic absorption spectroscopy for atom flux measurements in molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Du, Y., E-mail: yingge.du@pnnl.gov, E-mail: scott.chambers@pnnl.gov; Liyu, A. V. [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Droubay, T. C.; Chambers, S. A., E-mail: yingge.du@pnnl.gov, E-mail: scott.chambers@pnnl.gov [Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Li, G. [Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States)

    2014-04-21

    A high sensitivity atom flux sensor based on atomic absorption spectroscopy has been designed and implemented to control electron beam evaporators and effusion cells in a molecular beam epitaxy system. Using a high-resolution spectrometer and a two-dimensional charge coupled device detector in a double-beam configuration, we employ either a non-resonant line or a resonant line with low cross section from the same hollow cathode lamp as the reference for nearly perfect background correction and baseline drift removal. This setup also significantly shortens the warm-up time needed compared to other sensor technologies and drastically reduces the noise coming from the surrounding environment. In addition, the high-resolution spectrometer allows the most sensitive resonant line to be isolated and used to provide excellent signal-to-noise ratio.

  17. Self-corrected Sensors Based On Atomic Absorption Spectroscopy For Atom Flux Measurements In Molecular Beam Epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Du, Yingge; Droubay, Timothy C.; Liyu, Andrey V.; Li, Guosheng; Chambers, Scott A.

    2014-04-24

    A high sensitivity atom flux sensor based on atomic absorption spectroscopy has been designed and implemented to control electron beam evaporators and effusion cells in a molecular beam epitaxy system. Using a high-resolution spectrometer and a two-dimensional charge coupled device (CCD) detector in a double-beam configuration, we employ a non-resonant line or a resonant line with lower absorbance from the same hollow cathode lamp as the reference for nearly perfect background correction and baseline drift removal. This setup also significantly shortens the warm-up time needed compared to other sensor technologies and drastically reduces the noise coming from the surrounding environment. In addition, the high-resolution spectrometer allows the most sensitive resonant line to be isolated and used to provide excellent signal-to-noise ratio.

  18. Self-corrected sensors based on atomic absorption spectroscopy for atom flux measurements in molecular beam epitaxy

    Science.gov (United States)

    Du, Y.; Droubay, T. C.; Liyu, A. V.; Li, G.; Chambers, S. A.

    2014-04-01

    A high sensitivity atom flux sensor based on atomic absorption spectroscopy has been designed and implemented to control electron beam evaporators and effusion cells in a molecular beam epitaxy system. Using a high-resolution spectrometer and a two-dimensional charge coupled device detector in a double-beam configuration, we employ either a non-resonant line or a resonant line with low cross section from the same hollow cathode lamp as the reference for nearly perfect background correction and baseline drift removal. This setup also significantly shortens the warm-up time needed compared to other sensor technologies and drastically reduces the noise coming from the surrounding environment. In addition, the high-resolution spectrometer allows the most sensitive resonant line to be isolated and used to provide excellent signal-to-noise ratio.

  19. Fast characterization of line-end shortening and application of novel correction algorithms in e-beam direct write

    Science.gov (United States)

    Freitag, Martin; Choi, Kang-Hoon; Gutsch, Manuela; Hohle, Christoph; Galler, Reinhard; Krüger, Michael; Weidenmueller, Ulf

    2011-04-01

    For the manufacturing of semiconductor technologies following the ITRS roadmap, we will face the nodes well below 32nm half pitch in the next 2~3 years. Despite being able to achieve the required resolution, which is now possible with electron beam direct write variable shaped beam (EBDW VSB) equipment and resists, it becomes critical to precisely reproduce dense line space patterns onto a wafer. This exposed pattern must meet the targets from the layout in both dimensions (horizontally and vertically). For instance, the end of a line must be printed in its entire length to allow a later placed contact to be able to land on it. Up to now, the control of printed patterns such as line ends is achieved by a proximity effect correction (PEC) which is mostly based on a dose modulation. This investigation of the line end shortening (LES) includes multiple novel approaches, also containing an additional geometrical correction, to push the limits of the available data preparation algorithms and the measurement. The designed LES test patterns, which aim to characterize the status of LES in a quick and easy way, were exposed and measured at Fraunhofer Center Nanoelectronic Technologies (CNT) using its state of the art electron beam direct writer and CD-SEM. Simulation and exposure results with the novel LES correction algorithms applied to the test pattern and a large production like pattern in the range of our target CDs in dense line space features smaller than 40nm will be shown.

  20. Correction

    CERN Multimedia

    2002-01-01

    The photo on the second page of the Bulletin n°48/2002, from 25 November 2002, illustrating the article «Spanish Visit to CERN» was published with a wrong caption. We would like to apologise for this mistake and so publish it again with the correct caption.   The Spanish delegation, accompanied by Spanish scientists at CERN, also visited the LHC superconducting magnet test hall (photo). From left to right: Felix Rodriguez Mateos of CERN LHC Division, Josep Piqué i Camps, Spanish Minister of Science and Technology, César Dopazo, Director-General of CIEMAT (Spanish Research Centre for Energy, Environment and Technology), Juan Antonio Rubio, ETT Division Leader at CERN, Manuel Aguilar-Benitez, Spanish Delegate to Council, Manuel Delfino, IT Division Leader at CERN, and Gonzalo León, Secretary-General of Scientific Policy to the Minister.

  1. Correction

    Directory of Open Access Journals (Sweden)

    2012-01-01

    Full Text Available Regarding Gorelik, G., & Shackelford, T.K. (2011. Human sexual conflict from molecules to culture. Evolutionary Psychology, 9, 564–587: The authors wish to correct an omission in citation to the existing literature. In the final paragraph on p. 570, we neglected to cite Burch and Gallup (2006 [Burch, R. L., & Gallup, G. G., Jr. (2006. The psychobiology of human semen. In S. M. Platek & T. K. Shackelford (Eds., Female infidelity and paternal uncertainty (pp. 141–172. New York: Cambridge University Press.]. Burch and Gallup (2006 reviewed the relevant literature on FSH and LH discussed in this paragraph, and should have been cited accordingly. In addition, Burch and Gallup (2006 should have been cited as the originators of the hypothesis regarding the role of FSH and LH in the semen of rapists. The authors apologize for this oversight.

  2. Correction

    Directory of Open Access Journals (Sweden)

    2014-01-01

    Full Text Available Regarding Tagler, M. J., and Jeffers, H. M. (2013. Sex differences in attitudes toward partner infidelity. Evolutionary Psychology, 11, 821–832: The authors wish to correct values in the originally published manuscript. Specifically, incorrect 95% confidence intervals around the Cohen's d values were reported on page 826 of the manuscript where we reported the within-sex simple effects for the significant Participant Sex × Infidelity Type interaction (first paragraph, and for attitudes toward partner infidelity (second paragraph. Corrected values are presented in bold below. The authors would like to thank Dr. Bernard Beins at Ithaca College for bringing these errors to our attention. Men rated sexual infidelity significantly more distressing (M = 4.69, SD = 0.74 than they rated emotional infidelity (M = 4.32, SD = 0.92, F(1, 322 = 23.96, p < .001, d = 0.44, 95% CI [0.23, 0.65], but there was little difference between women's ratings of sexual (M = 4.80, SD = 0.48 and emotional infidelity (M = 4.76, SD = 0.57, F(1, 322 = 0.48, p = .29, d = 0.08, 95% CI [−0.10, 0.26]. As expected, men rated sexual infidelity (M = 1.44, SD = 0.70 more negatively than they rated emotional infidelity (M = 2.66, SD = 1.37, F(1, 322 = 120.00, p < .001, d = 1.12, 95% CI [0.85, 1.39]. Although women also rated sexual infidelity (M = 1.40, SD = 0.62 more negatively than they rated emotional infidelity (M = 2.09, SD = 1.10, this difference was not as large and thus in the evolutionary theory supportive direction, F(1, 322 = 72.03, p < .001, d = 0.77, 95% CI [0.60, 0.94].

  3. Hardening Azure applications

    CERN Document Server

    Gaurav, Suraj

    2015-01-01

    Learn what it takes to build large scale, mission critical applications -hardened applications- on the Azure cloud platform. This 208 page book covers the techniques and engineering principles that every architect and developer needs to know to harden their Azure/.NET applications to ensure maximum reliability and high availability when deployed at scale. While the techniques are implemented in .NET and optimized for Azure, the principles here will also be valuable for users of other cloud-based development platforms. Applications come in a variety of forms, from simple apps that can be bui

  4. Determination of the beam quality correction factor k_{Q,Q_0 } for the microLion chamber in a clinical photon beam

    Science.gov (United States)

    Choi, Sang Hyoun; Kim, Chan Hyeong; Huh, Hyun Do; Kim, Kum-Bae; Kim, SeongHoon

    2013-01-01

    The mcroLion chamber, which has a small volume (0.0017cc) and a high sensitivity suitable for small field dosimetry, is an ionization chamber with liquid (isooctane) filling the cavity volume. In the present work, we used two alternative ways to estimate the beam quality correction factor k_{Q,Q_0 }^{micL} of the microLion chamber in the 6 MV photon beam from a Clinac iX accelerator (Varian, USA); Monte Carlo simulations and experimental methods. The Monte Carlo calculation (1.0183 ± 0.58%) agreed to within 0.56% with the experimental determination (1.024 ± 0.58%). The results from the two methods were in good agreement within acceptable uncertainties. We think that the averaged factor, 1.0212, could be used for the microLion chamber in reference dosimetry.

  5. Correction.

    Science.gov (United States)

    2015-10-01

    In the article by Quintavalle et al (Quintavalle C, Anselmi CV, De Micco F, Roscigno G, Visconti G, Golia B, Focaccio A, Ricciardelli B, Perna E, Papa L, Donnarumma E, Condorelli G, Briguori C. Neutrophil gelatinase–associated lipocalin and contrast-induced acute kidney injury. Circ Cardiovasc Interv. 2015;8:e002673. DOI: 10.1161/CIRCINTERVENTIONS.115.002673.), which published online September 2, 2015, and appears in the September 2015 issue of the journal, a correction was needed. On page 1, the institutional affiliation for Elvira Donnarumma, PhD, “SDN Foundation,” has been changed to read, “IRCCS SDN, Naples, Italy.” The institutional affiliation for Laura Papa, PhD, “Institute for Endocrinology and Experimental Oncology, National Research Council, Naples, Italy,” has been changed to read, “Institute of Genetics and Biomedical Research, Milan Unit, Milan, Italy” and “Humanitas Research Hospital, Rozzano, Italy.” The authors regret this error.

  6. Concrete, hardened: Self desiccation

    DEFF Research Database (Denmark)

    Hansen, Ernst Jan De Place; Hansen, Kurt Kielsgaard; Persson, Bertil

    1999-01-01

    The test method covers the determination of internal relative humidity (RH) in hardened concrete and cement mortar using RH instruments. The determination of RH is done on crushed samples of concrete or cement motar. This test method is only for measuring equipment which gives off or takes up...

  7. Application of the two-dose-rate method for general recombination correction for liquid ionization chambers in continuous beams

    Science.gov (United States)

    Andersson, Jonas; Tölli, Heikki

    2011-01-01

    A method to correct for the general recombination losses for liquid ionization chambers in continuous beams has been developed. The proposed method has been derived from Greening's theory for continuous beams and is based on measuring the signal from a liquid ionization chamber and an air filled monitor ionization chamber at two different dose rates. The method has been tested with two plane parallel liquid ionization chambers in a continuous radiation x-ray beam with a tube voltage of 120 kV and with dose rates between 2 and 13 Gy min-1. The liquids used as sensitive media in the chambers were isooctane (C8H18) and tetramethylsilane (Si(CH3)4). The general recombination effect was studied using chamber polarizing voltages of 100, 300, 500, 700 and 900 V for both liquids. The relative standard deviation of the results for the collection efficiency with respect to general recombination was found to be a maximum of 0.7% for isooctane and 2.4% for tetramethylsilane. The results are in excellent agreement with Greening's theory for collection efficiencies over 90%. The measured and corrected signals from the liquid ionization chambers used in this work are in very good agreement with the air filled monitor chamber with respect to signal to dose linearity.

  8. Application of the two-dose-rate method for general recombination correction for liquid ionization chambers in continuous beams

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, Jonas; Toelli, Heikki, E-mail: jonas.andersson@radfys.umu.se [Department of Radiation Sciences, Radiation Physics, Umeaa University, SE-901 85 Umeaa (Sweden)

    2011-01-21

    A method to correct for the general recombination losses for liquid ionization chambers in continuous beams has been developed. The proposed method has been derived from Greening's theory for continuous beams and is based on measuring the signal from a liquid ionization chamber and an air filled monitor ionization chamber at two different dose rates. The method has been tested with two plane parallel liquid ionization chambers in a continuous radiation x-ray beam with a tube voltage of 120 kV and with dose rates between 2 and 13 Gy min{sup -1}. The liquids used as sensitive media in the chambers were isooctane (C{sub 8}H{sub 18}) and tetramethylsilane (Si(CH{sub 3}){sub 4}). The general recombination effect was studied using chamber polarizing voltages of 100, 300, 500, 700 and 900 V for both liquids. The relative standard deviation of the results for the collection efficiency with respect to general recombination was found to be a maximum of 0.7% for isooctane and 2.4% for tetramethylsilane. The results are in excellent agreement with Greening's theory for collection efficiencies over 90%. The measured and corrected signals from the liquid ionization chambers used in this work are in very good agreement with the air filled monitor chamber with respect to signal to dose linearity.

  9. An experimental study of the scatter correction by using a beam-stop-array algorithm with digital breast tomosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ye-Seul; Park, Hye-Suk; Kim, Hee-Joung [Yonsei University, Wonju (Korea, Republic of); Choi, Young-Wook; Choi, Jae-Gu [Korea Electrotechnology Research Institute, Ansan (Korea, Republic of)

    2014-12-15

    Digital breast tomosynthesis (DBT) is a technique that was developed to overcome the limitations of conventional digital mammography by reconstructing slices through the breast from projections acquired at different angles. In developing and optimizing DBT, The x-ray scatter reduction technique remains a significant challenge due to projection geometry and radiation dose limitations. The most common approach to scatter reduction is a beam-stop-array (BSA) algorithm; however, this method raises concerns regarding the additional exposure involved in acquiring the scatter distribution. The compressed breast is roughly symmetric, and the scatter profiles from projections acquired at axially opposite angles are similar to mirror images. The purpose of this study was to apply the BSA algorithm with only two scans with a beam stop array, which estimates the scatter distribution with minimum additional exposure. The results of the scatter correction with angular interpolation were comparable to those of the scatter correction with all scatter distributions at each angle. The exposure increase was less than 13%. This study demonstrated the influence of the scatter correction obtained by using the BSA algorithm with minimum exposure, which indicates its potential for practical applications.

  10. Experimental determination of field factors ([Formula: see text]) for small radiotherapy beams using the daisy chain correction method.

    Science.gov (United States)

    Lárraga-Gutiérrez, José Manuel

    2015-08-07

    Recently, Alfonso et al proposed a new formalism for the dosimetry of small and non-standard fields. The proposed new formalism is strongly based on the calculation of detector-specific beam correction factors by Monte Carlo simulation methods, which accounts for the difference in the response of the detector between the small and the machine specific reference field. The correct calculation of the detector-specific beam correction factors demands an accurate knowledge of the linear accelerator, detector geometry and composition materials. The present work shows that the field factors in water may be determined experimentally using the daisy chain correction method down to a field size of 1 cm × 1 cm for a specific set of detectors. The detectors studied were: three mini-ionization chambers (PTW-31014, PTW-31006, IBA-CC01), three silicon-based diodes (PTW-60018, IBA-SFD and IBA-PFD) and one synthetic diamond detector (PTW-60019). Monte Carlo simulations and experimental measurements were performed for a 6 MV photon beam at 10 cm depth in water with a source-to-axis distance of 100 cm. The results show that the differences between the experimental and Monte Carlo calculated field factors are less than 0.5%-with the exception of the IBA-PFD-for field sizes between 1.5 cm × 1.5 cm and 5 cm × 5 cm. For the 1 cm × 1 cm field size, the differences are within 2%. By using the daisy chain correction method, it is possible to determine measured field factors in water. The results suggest that the daisy chain correction method is not suitable for measurements performed with the IBA-PFD detector. The latter is due to the presence of tungsten powder in the detector encapsulation material. The use of Monte Carlo calculated [Formula: see text] is encouraged for field sizes less than or equal to 1 cm × 1 cm for the dosimeters used in this work.

  11. The main beam correction term in kinetic energy release from metastable peaks.

    Science.gov (United States)

    Petersen, Allan Christian

    2017-08-26

    The correction term for the precursor ion signal width in determination of kinetic energy release is reviewed and the correction term is formally derived. The derived correction term differs from the traditionally applied term. An experimental finding substantiates the inaccuracy in the latter. The application of the 'T-value' to study kinetic energy release is found preferable to kinetic energy release distributions when the metastable peaks are slim and simple Gaussians. For electronically predissociated systems a 'borderline zero' kinetic energy release can be directly interpreted in terms of reaction dynamics with strong curvature in the reaction coordinate. This article is protected by copyright. All rights reserved.

  12. Polarity and ion recombination corrections in continuous and pulsed beams for ionization chambers with high Z chamber walls.

    Science.gov (United States)

    Aldosary, Ghada; Safigholi, Habib; Song, William; Seuntjens, Jan; Sarfehnia, Arman

    2017-03-01

    In this work, the response of Farmer-type ionization chambers fitted with high atomic number (Z) walls is studied, and results of the effects of such walls on polarity and ion recombination correction factors in both continuous and pulsed beams are presented. Measurements were made in a continuous Co-60 beam and a pulsed 6MV linac beam using an Exradin-A12 ionization chamber fitted with the manufacturer's C-552 plastic wall, as well as geometrically identical walls made from aluminum, copper and molybdenum. The bias voltage was changed between 10values (range: +50 to +560V). Ion recombination was determined from Jaffé plots and by using the "two-voltage technique". The saturation charge measured with each chamber wall was extrapolated from Jaffé plots. Additionally, the effect of different wall materials on chamber response was studied using MCNP simulations. Results showed that the polarity correction factor is not significantly affected by changes in chamber wall material (within 0.1%). Furthermore, although the saturation charges greatly vary with each chamber wall material, and charge multiplication increases for higher atomic number wall materials, the standard methods of calculating ion recombination yielded results that differed by only 0.2%. Therefore, polarity and ion recombination correction factors are not greatly affected by the chamber wall material. The experimental saturation charges for all the different wall materials agreed well within the uncertainty with MCNP simulations. The breakdown of the linear relationship in Jaffé plots that was previously reported to exist for conventional chamber walls was also observed with the different wall materials.

  13. Joint statistical correction of clutters, spokes and beam height for a radar climatology in Southern Germany

    Directory of Open Access Journals (Sweden)

    A. Wagner

    2012-04-01

    Full Text Available Extensive corrections of radar data are a crucial prerequisite for radar derived climatology. This kind of climatology demands a high level of data quality. Little deviations or minor systematic underestimations or overestimations in single radar images become a major cause of error in statistical analysis. First results of radar derived climatology have emerged over the last years, as data sets of appropriate extent are becoming available. Usually, these statistics are based on time series lasting up to ten years as storage of radar data was not achieved before.

    We present a new statistical post-correction scheme, which is based on seven years of radar data of the Munich weather radar (2000–2006 that is operated by DWD (German Weather Service. The typical correction algorithms for single radar images, such as clutter corrections, are used. Then an additional statistical post-correction based on the results of a climatological analysis from radar images follows. The aim of this statistical correction is to correct systematic errors caused by clutter effects or measuring effects but to conserve small-scale natural variations in space.

    The statistical correction is based on a thorough analysis of the different causes of possible errors for the Munich weather radar. This robust analysis revealed the following basic effects: the decrease of rain rate in relation to height and distance from the radar, clutter effects such as remaining clutter, eliminated clutter or shading effects from obstacles near the radar, visible as spokes, as well as the influence of the Bright Band. The correction algorithm is correspondingly based on these results. It consists of three modules. The first one is an altitude correction, which minimizes measuring effects. The second module corrects clutter effects and the third one realizes a mean adjustment to selected rain gauges. Two different radar products are used. The statistical analysis as well as

  14. RHOBOT: Radiation hardened robotics

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, P.C.; Posey, L.D. [Sandia National Labs., Albuquerque, NM (United States)

    1997-10-01

    A survey of robotic applications in radioactive environments has been conducted, and analysis of robotic system components and their response to the varying types and strengths of radiation has been completed. Two specific robotic systems for accident recovery and nuclear fuel movement have been analyzed in detail for radiation hardness. Finally, a general design approach for radiation-hardened robotics systems has been developed and is presented. This report completes this project which was funded under the Laboratory Directed Research and Development program.

  15. Grind hardening process

    CERN Document Server

    Salonitis, Konstantinos

    2015-01-01

    This book presents the grind-hardening process and the main studies published since it was introduced in 1990s.  The modelling of the various aspects of the process, such as the process forces, temperature profile developed, hardness profiles, residual stresses etc. are described in detail. The book is of interest to the research community working with mathematical modeling and optimization of manufacturing processes.

  16. On the wall perturbation correction for a parallel-plate NACP-02 chamber in clinical electron beams

    Energy Technology Data Exchange (ETDEWEB)

    Zink, K.; Wulff, J. [University Hospital Marburg, Philipps-University, D-35043 Marburg, Germany and Institut fuer Medizinische Physik und Strahlenschutz - IMPS, University of Applied Sciences Giessen-Friedberg, D-35390 Giessen (Germany); Institut fuer Medizinische Physik und Strahlenschutz - IMPS, University of Applied Sciences Giessen-Friedberg, D-35390 Giessen (Germany)

    2011-02-15

    Purpose: In recent years, several Monte Carlo studies have been published concerning the perturbation corrections of a parallel-plate chamber in clinical electron beams. In these studies, a strong depth dependence of the relevant correction factors (p{sub wall} and p{sub cav}) for depth beyond the reference depth is recognized and it has been shown that the variation with depth is sensitive to the choice of the chamber's effective point of measurement. Recommendations concerning the positioning of parallel-plate ionization chambers in clinical electron beams are not the same for all current dosimetry protocols. The IAEA TRS-398 as well as the IPEM protocol and the German protocol DIN 6800-2 interpret the depth of measurement within the phantom as the water equivalent depth, i.e., the nonwater equivalence of the entrance window has to be accounted for by shifting the chamber by an amount {Delta}z. This positioning should ensure that the primary electrons traveling from the surface of the water phantom through the entrance window to the chamber's reference point sustain the same energy loss as the primary electrons in the undisturbed phantom. The objective of the present study is the determination of the shift {Delta}z for a NACP-02 chamber and the calculation of the resulting wall perturbation correction as a function of depth. Moreover, the contributions of the different chamber walls to the wall perturbation correction are identified. Methods: The dose and fluence within the NACP-02 chamber and a wall-less air cavity is calculated using the Monte Carlo code EGSnrc in a water phantom at different depths for different clinical electron beams. In order to determine the necessary shift to account for the nonwater equivalence of the entrance window, the chamber is shifted in steps {Delta}z around the depth of measurement. The optimal shift {Delta}z is determined from a comparison of the spectral fluence within the chamber and the bare cavity. The wall

  17. Mask process correction (MPC) modeling and its application to EUV mask for electron beam mask writer EBM-7000

    Science.gov (United States)

    Kamikubo, Takashi; Ohnishi, Takayuki; Hara, Shigehiro; Anze, Hirohito; Hattori, Yoshiaki; Tamamushi, Shuichi; Bai, Shufeng; Wang, Jen-Shiang; Howell, Rafael; Chen, George; Li, Jiangwei; Tao, Jun; Wiley, Jim; Kurosawa, Terunobu; Saito, Yasuko; Takigawa, Tadahiro

    2010-09-01

    In electron beam writing on EUV mask, it has been reported that CD linearity does not show simple signatures as observed with conventional COG (Cr on Glass) masks because they are caused by scattered electrons form EUV mask itself which comprises stacked heavy metals and thick multi-layers. To resolve this issue, Mask Process Correction (MPC) will be ideally applicable. Every pattern is reshaped in MPC. Therefore, the number of shots would not increase and writing time will be kept within reasonable range. In this paper, MPC is extended to modeling for correction of CD linearity errors on EUV mask. And its effectiveness is verified with simulations and experiments through actual writing test.

  18. Nuclear effects hardened shelters

    Science.gov (United States)

    Lindke, Paul

    1990-11-01

    The Houston Fearless 76 Government Projects Group has been actively engaged for more than twenty-five years as a sub-contractor and currently as a prime contractor in the design, manufacture, repair and logistics support of custom mobile ground stations and their equipment accommodations. Other associated products include environmental control units (ECU's), mobilizers for shelters and a variety of mobile power generation units (MPU's). Since 1984, Houston Fearless 76 has designed and manufactured four 8' x 8' x 22' nuclear hardened mobile shelters. These shelters were designed to contain electronic data processing/reduction equipment. One shelter is currently being operated by the Air Force as a Defense Intelligence Agency (DIA) approved and certified Special Corrpartmented Information Facility (SCIF). During the development and manufacturing process of the shelters, we received continual technical assistance and design concept evaluations from Science Applications International Corporation (SAIC) Operations Analysis and Logistics Engineering Division and the Nondestructive Inspection Lab at McClellan AFB. SAIC was originally employed by the Air Force to design the nuclear hardening specifications applied to these shelters. The specific levels of hardening to which the shelters were designed are classified and will not be mentioned during this presentation.

  19. Fluence Correction Factors and Stopping Power Ratios for Clinical Ion Beams

    DEFF Research Database (Denmark)

    Lühr, Armin Christian; Hansen, David Christoffer; Sobolevsky, Nikolai

    2011-01-01

    for increased positioning accuracy, graphite calorimetry being developed as a primary standard for dose to water dosimetry, but also for the comparison of dose distributions from Monte Carlo simulations with those of pencil beam algorithms. Material and methods. In the conversion of absorbed dose to phantom...

  20. Wavefront-sensor-induced beam size error: physical mechanism, sensitivity-analysis and correction method

    NARCIS (Netherlands)

    Koek, W.D.; Zwet, E.J. van

    2015-01-01

    When using a commonly-used quadri-wave lateral shearing interferometer wavefront sensor (QWLSI WFS) for beam size measurements on a high power CO2 laser, artefacts have been observed in the measured irradiance distribution. The grating in the QWLSI WFS not only generates the diffracted first orders

  1. Wavefront-sensor-induced beam size error: physical mechanism, sensitivity-analysis and correction method

    NARCIS (Netherlands)

    Koek, W.D.; Zwet, E.J. van

    2015-01-01

    When using a commonly-used quadri-wave lateral shearing interferometer wavefront sensor (QWLSI WFS) for beam size measurements on a high power CO2 laser, artefacts have been observed in the measured irradiance distribution. The grating in the QWLSI WFS not only generates the diffracted first orders

  2. A GPU-based finite-size pencil beam algorithm with 3D-density correction for radiotherapy dose calculation

    CERN Document Server

    Gu, Xuejun; Li, Jinsheng; Jia, Xun; Jiang, Steve B

    2011-01-01

    Targeting at developing an accurate and efficient dose calculation engine for online adaptive radiotherapy, we have implemented a finite size pencil beam (FSPB) algorithm with a 3D-density correction method on GPU. This new GPU-based dose engine is built on our previously published ultrafast FSPB computational framework [Gu et al. Phys. Med. Biol. 54 6287-97, 2009]. Dosimetric evaluations against MCSIM Monte Carlo dose calculations are conducted on 10 IMRT treatment plans with heterogeneous treatment regions (5 head-and-neck cases and 5 lung cases). For head and neck cases, when cavities exist near the target, the improvement with the 3D-density correction over the conventional FSPB algorithm is significant. However, when there are high-density dental filling materials in beam paths, the improvement is small and the accuracy of the new algorithm is still unsatisfactory. On the other hand, significant improvement of dose calculation accuracy is observed in all lung cases. Especially when the target is in the m...

  3. Open-loop correction for an eddy current dominated beam-switching magnet

    Science.gov (United States)

    Koseki, K.; Nakayama, H.; Tawada, M.

    2014-04-01

    A beam-switching magnet and the pulsed power supply it requires have been developed for the Japan Proton Accelerator Research Complex. To switch bunched proton beams, the dipole magnetic field must reach its maximum value within 40 ms. In addition, the field flatness should be less than 5 × 10-4 to guide each bunched beam to the designed orbit. From a magnetic field measurement by using a long search coil, it was found that an eddy current in the thick endplates and laminated core disturbs the rise of the magnetic field. The eddy current also deteriorates the field flatness over the required flat-top period. The measured field flatness was 5 × 10-3. By using a double-exponential equation to approximate the measured magnetic field, a compensation pattern for the eddy current was calculated. The integrated magnetic field was measured while using the newly developed open-loop compensation system. A field flatness of less than 5 × 10-4, which is an acceptable value, was achieved.

  4. Open-loop correction for an eddy current dominated beam-switching magnet

    Energy Technology Data Exchange (ETDEWEB)

    Koseki, K., E-mail: kunio.koseki@kek.jp; Nakayama, H.; Tawada, M. [High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

    2014-04-15

    A beam-switching magnet and the pulsed power supply it requires have been developed for the Japan Proton Accelerator Research Complex. To switch bunched proton beams, the dipole magnetic field must reach its maximum value within 40 ms. In addition, the field flatness should be less than 5 × 10{sup −4} to guide each bunched beam to the designed orbit. From a magnetic field measurement by using a long search coil, it was found that an eddy current in the thick endplates and laminated core disturbs the rise of the magnetic field. The eddy current also deteriorates the field flatness over the required flat-top period. The measured field flatness was 5 × 10{sup −3}. By using a double-exponential equation to approximate the measured magnetic field, a compensation pattern for the eddy current was calculated. The integrated magnetic field was measured while using the newly developed open-loop compensation system. A field flatness of less than 5 × 10{sup −4}, which is an acceptable value, was achieved.

  5. Industrial Hardening Demonstration.

    Science.gov (United States)

    1980-09-01

    less severe conditions than thermal cracking (850’ - 950°F and 10 to 20 psi). Zeolitic or molecular sieve- base catalysts are used. Catalytic reforming...with Potential Industrial Hardening A-1 Participants B Post-Attack Petroleum Refining (and Production) B-1 from Crude Oil V List of Figures Number Page...the Key Worker Shelter 116 viii B-1 Proportions of the Products Obtained by Distillation B-2 of Six Crude Oils B-2 Generalized Flow Chart of the

  6. Iterative reconstruction with correction of the spatially variant fan-beam collimator response in neurotransmission SPET imaging.

    Science.gov (United States)

    Pareto, Deborah; Cot, Albert; Pavía, Javier; Falcón, Carles; Juvells, Ignacio; Lomeña, Francisco; Ros, Domènec

    2003-10-01

    The dopamine transporter (DAT) has been shown to be a sensitive indicator of nigrostriatal dopamine function. Although visual inspection is often sufficient to assess DAT imaging, quantification could improve the diagnostic accuracy of single-photon emission tomography (SPET) studies of the dopaminergic system. The aim of this study was to assess the accuracy of quantification of the striatal/background uptake ratio when correction for attenuation, scatter and spatially variant fan-beam collimator response is performed in technetium-99m and iodine-123 SPET imaging. A numerical striatal phantom was implemented, and simulated projections of low-energy photons were obtained by using the SimSET Monte Carlo code. High-energy contamination in 123I studies was modelled from experimental measurements with 99mTc and 123I. The ordered subsets expectation maximisation (OSEM) algorithm was employed in reconstruction. Mean improvements of 8% and 16% were obtained in the calculated striatal/background uptake ratio in the putamen and the caudate, respectively, when the spatially variant point spread function was included in the transition matrix. Ideal scatter correction resulted in improvements in the putamen and caudate of 9% for 99mTc agents and 19% for 123I agents. Improvements averaged 31% in the putamen and 43% in the caudate when correction for attenuation, scatter and spatially variant collimator response was included in the reconstruction.

  7. Monte-Carlo scatter correction for cone-beam computed tomography with limited scan field-of-view

    Science.gov (United States)

    Bertram, Matthias; Sattel, Timo; Hohmann, Steffen; Wiegert, Jens

    2008-03-01

    In flat detector cone-beam computed tomography (CBCT), scattered radiation is a major source of image degradation, making accurate a posteriori scatter correction inevitable. A potential solution to this problem is provided by computerized scatter correction based on Monte-Carlo simulations. Using this technique, the detected distributions of X-ray scatter are estimated for various viewing directions using Monte-Carlo simulations of an intermediate reconstruction. However, as a major drawback, for standard CBCT geometries and with standard size flat detectors such as mounted on interventional C-arms, the scan field of view is too small to accommodate the human body without lateral truncations, and thus this technique cannot be readily applied. In this work, we present a novel method for constructing a model of the object in a laterally and possibly also axially extended field of view, which enables meaningful application of Monte-Carlo based scatter correction even in case of heavy truncations. Evaluation is based on simulations of a clinical CT data set of a human abdomen, which strongly exceeds the field of view of the simulated C-arm based CBCT imaging geometry. By using the proposed methodology, almost complete removal of scatter-caused inhomogeneities is demonstrated in reconstructed images.

  8. Direct focusing error correction with ring-wide TBT beam position data

    CERN Document Server

    Yang, M J

    2012-01-01

    Turn-By-Turn (TBT) betatron oscillation data is a very powerful tool in studying machine optics. Hundreds and thousands of turns of free oscillations are taken in just few tens of milliseconds. With beam covering all positions and angles at every location TBT data can be used to diagnose focusing errors almost instantly. This paper describes a new approach that observes focusing error collectively over all available TBT data to find the optimized quadrupole strength, one location at a time. Example will be shown and other issues will be discussed.

  9. Scattering correction based on regularization de-convolution for Cone-Beam CT

    OpenAIRE

    Xie, Shi-peng; Yan, Rui-ju

    2016-01-01

    In Cone-Beam CT (CBCT) imaging systems, the scattering phenomenon has a significant impact on the reconstructed image and is a long-lasting research topic on CBCT. In this paper, we propose a simple, novel and fast approach for mitigating scatter artifacts and increasing the image contrast in CBCT, belonging to the category of convolution-based method in which the projected data is de-convolved with a convolution kernel. A key step in this method is how to determine the convolution kernel. Co...

  10. Prefabricated Roof Beams for Hardened Shelters

    Science.gov (United States)

    1993-08-01

    Reference 44), and SDOF analysis program. This approach is widely used and, therefore, familia to the design community performing work in his ara...C2 SECTION D-D2 NOTES- 1) Usir E70XX low-hyd-agfn eect des. 2) Use A572 . 50 or" ecuwv. st roet all flanges, ebS . nd stiffeners. 3) Shear comectors

  11. Cosmic Ray Helium Hardening

    CERN Document Server

    Ohira, Yutaka

    2010-01-01

    Recent observations by CREAM, ATIC-2 and PAMELA experiments suggest that (1) the spectrum of cosmic ray (CR) helium is harder than that of CR proton below the knee $10^15 eV$ and (2) all CR spectra become hard at $\\gtrsim 10^{11} eV/n$. We propose a new picture that higher energy CRs are generated in more helium-rich region to explain the hardening (1) without introducing different sources for CR helium. The helium to proton ratio at $\\sim 100$ TeV exceeds the Big Bang abundance $Y=0.25$ by several times, and the different spectrum is not reproduced within the diffusive shock acceleration theory. We argue that CRs are produced in the chemically enriched region, such as a superbubble, and the outward-decreasing abundance naturally leads to the hard spectrum of CR helium when escaping from the supernova remnant (SNR) shock. We provide a simple analytical spectrum that also fits well the hardening (2) because of the decreasing Mach number in the hot superbubble with $\\sim 10^6$ K. Our model predicts hard and con...

  12. Evaluation of tumor localization in respiration motion-corrected cone-beam CT: Prospective study in lung

    Energy Technology Data Exchange (ETDEWEB)

    Dzyubak, Oleksandr; Kincaid, Russell; Hertanto, Agung; Hu, Yu-Chi; Pham, Hai; Yorke, Ellen; Zhang, Qinghui; Mageras, Gig S., E-mail: magerasg@mskcc.org [Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York 10065 (United States); Rimner, Andreas [Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York 10065 (United States)

    2014-10-15

    Purpose: Target localization accuracy of cone-beam CT (CBCT) images used in radiation treatment of respiratory disease sites is affected by motion artifacts (blurring and streaking). The authors have previously reported on a method of respiratory motion correction in thoracic CBCT at end expiration (EE). The previous retrospective study was limited to examination of reducing motion artifacts in a small number of patient cases. They report here on a prospective study in a larger group of lung cancer patients to evaluate respiratory motion-corrected (RMC)-CBCT ability to improve lung tumor localization accuracy and reduce motion artifacts in Linac-mounted CBCT images. A second study goal examines whether the motion correction derived from a respiration-correlated CT (RCCT) at simulation yields similar tumor localization accuracy at treatment. Methods: In an IRB-approved study, 19 lung cancer patients (22 tumors) received a RCCT at simulation, and on one treatment day received a RCCT, a respiratory-gated CBCT at end expiration, and a 1-min CBCT. A respiration monitor of abdominal displacement was used during all scans. In addition to a CBCT reconstruction without motion correction, the motion correction method was applied to the same 1-min scan. Projection images were sorted into ten bins based on abdominal displacement, and each bin was reconstructed to produce ten intermediate CBCT images. Each intermediate CBCT was deformed to the end expiration state using a motion model derived from RCCT. The deformed intermediate CBCT images were then added to produce a final RMC-CBCT. In order to evaluate the second study goal, the CBCT was corrected in two ways, one using a model derived from the RCCT at simulation [RMC-CBCT(sim)], the other from the RCCT at treatment [RMC-CBCT(tx)]. Image evaluation compared uncorrected CBCT, RMC-CBCT(sim), and RMC-CBCT(tx). The gated CBCT at end expiration served as the criterion standard for comparison. Using automatic rigid image

  13. Photon beam convolution using polyenergetic energy deposition kernels

    Energy Technology Data Exchange (ETDEWEB)

    Hoban, P.W.; Murray, D.C.; Round, W.H. (Waikato Univ., Hamilton (New Zealand). Dept. of Physics)

    1994-04-01

    In photon beam convolution calculations where polyenergetic energy deposition kernels (EDKs) are used, the primary photon energy spectrum should be correctly accounted for in Monte Carlo generation of EDKs. This requires the probability of interaction, determined by the linear attenuation coefficient, [mu], to be taken into account when primary photon interactions are forced to occur at the EDK origin. The use of primary and scattered EDKs generated with a fixed photon spectrum can give rise to an error in the dose calculation due to neglecting the effects of beam hardening with depth. The proportion of primary photon energy that is transferred to secondary electrons increases with depth of interaction, due to the increase in the ratio [mu][sub ab]/[mu] as the beam hardens. Convolution depth-dose curves calculated using polyenergetic EDKs generated for the primary photon spectra which exist at depths of 0, 20 and 40 cm in water, show a fall-off which is too steep when compared with EGS4 Monte Carlo results. A beam hardening correction factor applied to primary and scattered 0 cm EDKs, based on the ratio of kerma to terma at each depth, gives primary, scattered and total dose in good agreement with Monte Carlo results. (Author).

  14. Scattering correction based on regularization de-convolution for Cone-Beam CT

    CERN Document Server

    Xie, Shi-peng

    2016-01-01

    In Cone-Beam CT (CBCT) imaging systems, the scattering phenomenon has a significant impact on the reconstructed image and is a long-lasting research topic on CBCT. In this paper, we propose a simple, novel and fast approach for mitigating scatter artifacts and increasing the image contrast in CBCT, belonging to the category of convolution-based method in which the projected data is de-convolved with a convolution kernel. A key step in this method is how to determine the convolution kernel. Compared with existing methods, the estimation of convolution kernel is based on bi-l1-l2-norm regularization imposed on both the intermediate the known scatter contaminated projection images and the convolution kernel. Our approach can reduce the scatter artifacts from 12.930 to 2.133.

  15. Optimal Design for Nonperiodic Fine Grating Structure Controlled by Proximity Correction with Electron-Beam Lithography

    Science.gov (United States)

    Okano, Masato; Hirai, Yoshihiko; Kikuta, Hisao

    2007-02-01

    We describe a method for designing nonperiodic fine grating structures such as a small F-number diffractive cylindrical lens, to be fabricated by direct-writing electron-beam lithography. The design is based on a resist development simulator for estimating a proximity effect of electron dose and the finite difference time domain (FDTD) method for simulating an electromagnetic field. The surface profile and electron dose distribution are simultaneously optimized to obtain the high diffraction efficiency. For the design of a diffractive lens of 50 μm width and 25 μm focal length, the calculated diffraction efficiency is 49% for 650-nm-wavelength light, which is slightly lower than that of a diffractive lens profile optimized by electromagnetic analysis without restrictions on fabrication limits.

  16. Advanced transformational analysis applied to e-beam proximity effect correction

    Science.gov (United States)

    Barouch, Eytan; Coifman, Ronald R.; Ma, Jimmy T.; Peckerar, Martin C.; Rokhlin, Vladimir

    1993-06-01

    In this paper we address the problem of dose correction in the data bases consistent with ultra- large-scale integration. It is shown that recent advances in transformation theory provide a natural platform on which to build these dose correctors. Specifically, transformation approaches making use of compactly supported, smooth basis functions are shown to be particularly suitable. This is a natural result of the evolution of mathematically based correctors currently in use. Previous work in Parikh, MacDonald and others employed global transform method to determine the values of 'corrected' dose. In most cases, the mathematical inversion is essentially ill posed, in other words, the exact pattern desired cannot be obtained using a finite Gaussian sum. In this paper a set of smooth basis elements of compact support are employed. The mathematically smooth form of the basis makes it easy to match doses at boundaries without Gibbs phenomenon. Thus the transform field can be partitioned for optimum speed. Consequently, while most transformation complexities are of order N6 (the inversion of an N2 X N2 matrix) where N2 is the number of grid points characterizing the database, we developed an algorithm of complexity N2 log N. A method of dose field bias is employed to stem the requests for negative dose. The heart of the numerical process is essentially based on an adapted fast non-uniform-grid Fourier Transform combined with proper filtering and geometric localization methods. Several examples are given.

  17. Correction of beam wander for a free-space quantum key distribution system operating in urban environment

    CERN Document Server

    Carrasco-Casado, Alberto; Fernandez, Veronica

    2014-01-01

    Free-space quantum key distribution links in urban environment have demanding operating needs, such as functioning in daylight and under atmospheric turbulence, which can dramatically impact their performance. Both effects are usually mitigated with a careful design of the field of view of the receiver. However, a trade-off is often required, since a narrow field of view improves background noise rejection but it is linked to an increase in turbulence-related losses. In this paper, we present a high-speed automatic tracking system to overcome these limitations. Both a reduction in the field-of-view to decrease the background noise and the mitigation of the losses caused by atmospheric turbulence are addressed. Two different designs are presented and discussed, along with technical considerations for the experimental implementation. Finally, preliminary experimental results of beam wander correction are used to estimate the potential improvement of both the quantum bit error rate and secret key rate of a free ...

  18. Evaluation of Strain Hardening Parameters

    Institute of Scientific and Technical Information of China (English)

    DING Zong-hai; Pavel Huml; YANG Wei

    2004-01-01

    The plane-strain compression test for three kinds of materials was carried out in a temperature range between room temperature and 400 ℃. The σ - ε curves and strain-hardening rate at different temperatures were simulated and a reasonable fit to the experimental data was obtained. A modified model created by data inference and computer simulation was developed to describe the strain hardening at a large deformation, and the predicted strain hardening are in a good agreement with that observed in a large range of stress. The influences of different parameters on strain hardening behaviour under large deformation were analysed. The temperature increase within the test temperatures for stainless steel 18/8 Ti results in dropping of flow stress and strain-hardening rate. For favourable γ-fibre texture to obtain high r, the cold rolling was applied at large reduction. In the experimental procedure, the X-ray diffraction test was carried out to compare the strain hardening and microstructure under large deformation for a bcc steel (low carbon steel SS-1142). The results indicate that the high strain-hardening rate possibly occurs when the primary slip plane {110} is parallel to the rolling plane and the strain-hardening rate decreases when lots of {110} plane rotate out from the orientation {110}∥RP.

  19. Patient Position Verification and Corrective Evaluation Using Cone Beam Computed Tomography (CBCT) in Intensity modulated Radiation Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Do, Gyeong Min; Jeong, Deok Yang; Kim, Young Bum [Dept. of Radiation Oncology, Korea University Guro Hospital, Seoul (Korea, Republic of)

    2009-09-15

    Cone beam computed tomography (CBCT) using an on board imager (OBI) can check the movement and setup error in patient position and target volume by comparing with the image of computer simulation treatment in real.time during patient treatment. Thus, this study purposed to check the change and movement of patient position and target volume using CBCT in IMRT and calculate difference from the treatment plan, and then to correct the position using an automated match system and to test the accuracy of position correction using an electronic portal imaging device (EPID) and examine the usefulness of CBCT in IMRT and the accuracy of the automatic match system. The subjects of this study were 3 head and neck patients and 1 pelvis patient sampled from IMRT patients treated in our hospital. In order to investigate the movement of treatment position and resultant displacement of irradiated volume, we took CBCT using OBI mounted on the linear accelerator. Before each IMRT treatment, we took CBCT and checked difference from the treatment plan by coordinate by comparing it with the image of CT simulation. Then, we made correction through the automatic match system of 3D/3D match to match the treatment plan, and verified and evaluated using electronic portal imaging device. When CBCT was compared with the image of CT simulation before treatment, the average difference by coordinate in the head and neck was 0.99 mm vertically, 1.14 mm longitudinally, 4.91 mm laterally, and 1.07 degrees in the rotational direction, showing somewhat insignificant differences by part. In testing after correction, when the image from the electronic portal imaging device was compared with DRR image, it was found that correction had been made accurately with error less than 0.5 mm. By comparing a CBCT image before treatment with a 3D image reconstructed into a volume instead of a 2D image for the patient's setup error and change in the position of the organs and the target, we could measure and

  20. 用Timoshenko梁修正理论研究功能梯度材料梁的动力响应%Dynamic responses of a beam with functionally graded materials with Timoshenko beam correction theory

    Institute of Scientific and Technical Information of China (English)

    吴晓; 罗佑新

    2011-01-01

    The dynamic response of a beam with functionally graded materials was studied with Timoshenko beam correction theory. The neutral plane site of the beam with functionally graded materials was determined with the static equilibrium equations, and the vibration equations of the beam with functionally graded materials were established with Timoshenko beam correction theory, the expression for the natural frequencies of the beam with functionally graded materials and the analytical solution to forced vibration of the beam under the action of harmonic load were obtained. The effect of neutral plane site and gradient index on the dynamic responses of the beam were discussed, and Timoshenko beam correction theory was verified with finite element method. Analysis of examples indicated that the neutral plane site has larger influence on the dynamic responses of the beam with functionally graded materials.%采用Timoshenko梁修正理论研究了功能梯度材料梁的动力响应问题,利用静力方程确定了功能梯度材料梁的中性轴位置,在此基础上应用Timoshenko梁修正理论建立了功能梯度材料梁的振动方程,求得其自振频率表达式及其在简谐荷载作用下强迫振动的解析解.分析了中性面位置、梯度指数等因素对功能梯度材料梁的动力响应的影响,并用有限元法验证Timoshenko梁修正理论.通过实例计算,得到了中性轴位置对功能梯度材料梁动力响应有较大影响.

  1. Direct focusing error correction with ring-wide TBT beam position data

    Energy Technology Data Exchange (ETDEWEB)

    Yang, M.J.; /Fermilab

    2011-03-01

    Turn-By-Turn (TBT) betatron oscillation data is a very powerful tool in studying machine optics. Hundreds and thousands of turns of free oscillations are taken in just few tens of milliseconds. With beam covering all positions and angles at every location TBT data can be used to diagnose focusing errors almost instantly. This paper describes a new approach that observes focusing error collectively over all available TBT data to find the optimized quadrupole strength, one location at a time. Example will be shown and other issues will be discussed. The procedure presented clearly has helped to reduce overall deviations significantly, with relative ease. Sextupoles, being a permanent feature of the ring, will need to be incorporated into the model. While cumulative effect from all sextupoles around the ring may be negligible on turn-to-turn basis it is not so in this transfer line analysis. It should be noted that this procedure is not limited to looking for quadrupole errors. By modifying the target of minimization it could in principle be used to look for skew quadrupole errors and sextupole errors as well.

  2. High-quality 3D correction of ring and radiant artifacts in flat panel detector-based cone beam volume CT imaging.

    Science.gov (United States)

    Anas, Emran Mohammad Abu; Kim, Jae Gon; Lee, Soo Yeol; Hasan, Md Kamrul

    2011-10-07

    The use of an x-ray flat panel detector is increasingly becoming popular in 3D cone beam volume CT machines. Due to the deficient semiconductor array manufacturing process, the cone beam projection data are often corrupted by different types of abnormalities, which cause severe ring and radiant artifacts in a cone beam reconstruction image, and as a result, the diagnostic image quality is degraded. In this paper, a novel technique is presented for the correction of error in the 2D cone beam projections due to abnormalities often observed in 2D x-ray flat panel detectors. Template images are derived from the responses of the detector pixels using their statistical properties and then an effective non-causal derivative-based detection algorithm in 2D space is presented for the detection of defective and mis-calibrated detector elements separately. An image inpainting-based 3D correction scheme is proposed for the estimation of responses of defective detector elements, and the responses of the mis-calibrated detector elements are corrected using the normalization technique. For real-time implementation, a simplification of the proposed off-line method is also suggested. Finally, the proposed algorithms are tested using different real cone beam volume CT images and the experimental results demonstrate that the proposed methods can effectively remove ring and radiant artifacts from cone beam volume CT images compared to other reported techniques in the literature.

  3. High-quality 3D correction of ring and radiant artifacts in flat panel detector-based cone beam volume CT imaging

    Energy Technology Data Exchange (ETDEWEB)

    Anas, Emran Mohammad Abu; Hasan, Md Kamrul [Department of Electrical and Electronic Engineering, Bangladesh University of Engineering and Technology, Dhaka-1000 (Bangladesh); Kim, Jae Gon; Lee, Soo Yeol, E-mail: khasan@eee.buet.ac.b [Department of Biomedical Engineering, Kyung Hee University, Kyungki 446-701 (Korea, Republic of)

    2011-10-07

    The use of an x-ray flat panel detector is increasingly becoming popular in 3D cone beam volume CT machines. Due to the deficient semiconductor array manufacturing process, the cone beam projection data are often corrupted by different types of abnormalities, which cause severe ring and radiant artifacts in a cone beam reconstruction image, and as a result, the diagnostic image quality is degraded. In this paper, a novel technique is presented for the correction of error in the 2D cone beam projections due to abnormalities often observed in 2D x-ray flat panel detectors. Template images are derived from the responses of the detector pixels using their statistical properties and then an effective non-causal derivative-based detection algorithm in 2D space is presented for the detection of defective and mis-calibrated detector elements separately. An image inpainting-based 3D correction scheme is proposed for the estimation of responses of defective detector elements, and the responses of the mis-calibrated detector elements are corrected using the normalization technique. For real-time implementation, a simplification of the proposed off-line method is also suggested. Finally, the proposed algorithms are tested using different real cone beam volume CT images and the experimental results demonstrate that the proposed methods can effectively remove ring and radiant artifacts from cone beam volume CT images compared to other reported techniques in the literature.

  4. Fifth-order corrected field descriptions of the Hermite-Gaussian (0,0) and (0,1) mode laser beam.

    Science.gov (United States)

    Wang, J X; Scheid, W; Hoelss, M; Ho, Y K

    2001-12-01

    In this paper, we extend the work of Barton and Alexander [J. App. Phys. 66, 2800 (1989)] on the fifth-order corrected field expressions for a Hermite-Gaussian (0,0) mode laser beam to more general cases with adjustable parameters. The parametric dependence of the electron dynamics is investigated by numerical methods. Finally, the fifth-order corrected field equations for the Hermite-Gaussian (0,1) mode are also presented.

  5. System-Level Radiation Hardening

    Science.gov (United States)

    Ladbury, Ray

    2014-01-01

    Although system-level radiation hardening can enable the use of high-performance components and enhance the capabilities of a spacecraft, hardening techniques can be costly and can compromise the very performance designers sought from the high-performance components. Moreover, such techniques often result in a complicated design, especially if several complex commercial microcircuits are used, each posing its own hardening challenges. The latter risk is particularly acute for Commercial-Off-The-Shelf components since high-performance parts (e.g. double-data-rate synchronous dynamic random access memories - DDR SDRAMs) may require other high-performance commercial parts (e.g. processors) to support their operation. For these reasons, it is essential that system-level radiation hardening be a coordinated effort, from setting requirements through testing up to and including validation.

  6. Patient-specific scatter correction for flat-panel detector-based cone-beam CT imaging.

    Science.gov (United States)

    Zhao, Wei; Brunner, Stephen; Niu, Kai; Schafer, Sebastian; Royalty, Kevin; Chen, Guang-Hong

    2015-02-07

    A patient-specific scatter correction algorithm is proposed to mitigate scatter artefacts in cone-beam CT (CBCT). The approach belongs to the category of convolution-based methods in which a scatter potential function is convolved with a convolution kernel to estimate the scatter profile. A key step in this method is to determine the free parameters introduced in both scatter potential and convolution kernel using a so-called calibration process, which is to seek for the optimal parameters such that the models for both scatter potential and convolution kernel is able to optimally fit the previously known coarse estimates of scatter profiles of the image object. Both direct measurements and Monte Carlo (MC) simulations have been proposed by other investigators to achieve the aforementioned rough estimates. In the present paper, a novel method has been proposed and validated to generate the needed coarse scatter profile for parameter calibration in the convolution method. The method is based upon an image segmentation of the scatter contaminated CBCT image volume, followed by a reprojection of the segmented image volume using a given x-ray spectrum. The reprojected data is subtracted from the scatter contaminated projection data to generate a coarse estimate of the needed scatter profile used in parameter calibration. The method was qualitatively and quantitatively evaluated using numerical simulations and experimental CBCT data acquired on a clinical CBCT imaging system. Results show that the proposed algorithm can significantly reduce scatter artefacts and recover the correct CT number. Numerical simulation results show the method is patient specific, can accurately estimate the scatter, and is robust with respect to segmentation procedure. For experimental and in vivo human data, the results show the CT number can be successfully recovered and anatomical structure visibility can be significantly improved.

  7. Contact allergy to epoxy hardeners.

    Science.gov (United States)

    Aalto-Korte, Kristiina; Suuronen, Katri; Kuuliala, Outi; Henriks-Eckerman, Maj-Len; Jolanki, Riitta

    2014-09-01

    Diglycidylether of bisphenol A resin is the most important sensitizer in epoxy systems, but a minority of patients develop concomitant or solitary contact allergy to epoxy hardeners. At the Finnish Institute of Occupational Health, several in-house test substances of epoxy hardeners have been tested in a special epoxy compound patch test series. To analyse the frequency and clinical relevance of allergic reactions to different epoxy hardeners. Test files (January 1991 to March 2013) were screened for contact allergy to different epoxy hardeners, and the clinical records of patients with allergic reactions were analysed for occupation, concomitant allergic reactions, and exposure. The most commonly positive epoxy hardeners were m-xylylenediamine (n = 24), 2,4,6-tris-(dimethylaminomethyl)phenol (tris-DMP; n = 14), isophorone-diamine (n = 12), and diethylenetriamine (n = 9). Trimethylhexamethylenediamine (n = 7), tetraethylenepentamine (n = 4), and triethylenetetramine (n = 2) elicited some reactions, although most patients were found to have no specific exposure. Allergic reactions to hexamethylenetetramine, dimethylaminopropylamine and ethylenediamine dihydrochloride were not related to epoxy products. Tris-DMP is an important sensitizer in epoxy hardeners, and should be included in the patch test series of epoxy chemicals. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  8. Thermal distortion real-time detection and correction of a high-power laser beam-splitter mirror based on double Shack-Hartmann wavefront sensors

    Science.gov (United States)

    Ning, Yu; Sun, Quan; Wang, Hongyan; Wu, Wuming; Du, Shaojun; Xu, Xiaojun

    2015-05-01

    In a high-power laser system, a beam splitter refers to the mirror which locates at the cross point of the path of highpower beam and the weak light section. Because of the thermo-optic effect and elasto-optic effect, a beam splitter deforms under intense laser radiation. This deformation adds extra phase on the incident waves and deliveries inaccurate information to the wavefront sensor. Consequently, the output laser focuses at finite distance and gets divergent when arrives at the target. To settle the above problem, this paper presents a new method for real-time correction of the thermal distortion of beam splitter, based on algorithm of the data fusion of two Shack-Hartmann wavefront sensors (SH-WFS). Different from the traditional AO system, which contains a wavefront sensor, a corrector and a servo controller, two extra Shack-Hartmann wavefront detectors are adopted in our AO system, to detect the transmitted and reflected aberrations of beam splitter mirror. And these aberrations are real-timely delivered to the wavefront sensor. Based on coordinate conversion and data fusion algorithm, it makes the wavefront sensor of AO can "see" the aberrations of splitter mirror by itself. Thus, the servo system controls the corrector to compensate these aberrations correctly. In this paper, the theoretical model of data fusion algorithm is carried out. A closed-loop AO system, which consists of a typical AO system and two extra Shack-Hartmann wavefront detectors, is set up to validate the data fusion algorithm. Experimental results show that, the distortion of a CaF2 beam splitter can be real-time corrected when the AO closedloop control is on. The beam quality factor of output laser decreases from 4 to 1.7 times of diffraction limit.

  9. Efficient Spherical Wavefront Correction near the Focus for the 0.89 PW/29.0 fs Ti:Sapphire Laser Beam

    Institute of Scientific and Technical Information of China (English)

    REN Zhi-Jun; LIANG Xiao-Yan; YU Liang-Hong; LU Xiao-Ming; LENG Yu-Xin; LI Ru-Xin; XU Zhi-Zhan

    2011-01-01

    We demonstrate a new loop system of the spherical wavefront (SW) correction near the beam focus to effectively improve the focusability of 0.89 PW/29.0 fs Ti:sapphire chirped pulse amplification laser. After wavefront correction, the Strehl ratio is improved to reach 0.91, and the focal spot size using the fl4 off-axis parabola is reduced to 6.34 × 6.94μm2 (corresponding to 1.63 × 1.78 times diffraction limitation). With full peak power of 0.89 PW,the peak intensity of 2.59 × 1021 W/cm2 is obtained. The experimental results show that the SW correction scheme near the beam focus is comparatively simple, economic and high-efficient.%@@ We demonstrate a new loop system of the spherical wavefront (SW) correction near the beam focus to effectively improve the focusability of 0.89 PW/29.0 fs Ti:sapphire chirped pulse amplification laser.After wavefront correction, the Strehl ratio is improved to reach 0.91, and the focal spot size using the f/4 off-axis parabola is reduced to 6.34 x 6.94μm2 (corresponding to 1.63 x 1.78 times diffraction limitation).With full peak power of 0.89 PW, the peak intensity of 2.59 x 1021 W/cm2 is obtained.The experimental results show that the SW correction scheme near the beam focus is comparatively simple, economic and high-efficient.

  10. Fast 4D cone-beam reconstruction using the McKinnon-Bates algorithm with truncation correction and nonlinear filtering

    Science.gov (United States)

    Zheng, Ziyi; Sun, Mingshan; Pavkovich, John; Star-Lack, Josh

    2011-03-01

    A challenge in using on-board cone beam computed tomography (CBCT) to image lung tumor motion prior to radiation therapy treatment is acquiring and reconstructing high quality 4D images in a sufficiently short time for practical use. For the 1 minute rotation times typical of Linacs, severe view aliasing artifacts, including streaks, are created if a conventional phase-correlated FDK reconstruction is performed. The McKinnon-Bates (MKB) algorithm provides an efficient means of reducing streaks from static tissue but can suffer from low SNR and other artifacts due to data truncation and noise. We have added truncation correction and bilateral nonlinear filtering to the MKB algorithm to reduce streaking and improve image quality. The modified MKB algorithm was implemented on a graphical processing unit (GPU) to maximize efficiency. Results show that a nearly 4x improvement in SNR is obtained compared to the conventional FDK phase-correlated reconstruction and that high quality 4D images with 0.4 second temporal resolution and 1 mm3 isotropic spatial resolution can be reconstructed in less than 20 seconds after data acquisition completes.

  11. A practical cone-beam CT scatter correction method with optimized Monte Carlo simulations for image-guided radiation therapy.

    Science.gov (United States)

    Xu, Yuan; Bai, Ti; Yan, Hao; Ouyang, Luo; Pompos, Arnold; Wang, Jing; Zhou, Linghong; Jiang, Steve B; Jia, Xun

    2015-05-07

    Cone-beam CT (CBCT) has become the standard image guidance tool for patient setup in image-guided radiation therapy. However, due to its large illumination field, scattered photons severely degrade its image quality. While kernel-based scatter correction methods have been used routinely in the clinic, it is still desirable to develop Monte Carlo (MC) simulation-based methods due to their accuracy. However, the high computational burden of the MC method has prevented routine clinical application. This paper reports our recent development of a practical method of MC-based scatter estimation and removal for CBCT. In contrast with conventional MC approaches that estimate scatter signals using a scatter-contaminated CBCT image, our method used a planning CT image for MC simulation, which has the advantages of accurate image intensity and absence of image truncation. In our method, the planning CT was first rigidly registered with the CBCT. Scatter signals were then estimated via MC simulation. After scatter signals were removed from the raw CBCT projections, a corrected CBCT image was reconstructed. The entire workflow was implemented on a GPU platform for high computational efficiency. Strategies such as projection denoising, CT image downsampling, and interpolation along the angular direction were employed to further enhance the calculation speed. We studied the impact of key parameters in the workflow on the resulting accuracy and efficiency, based on which the optimal parameter values were determined. Our method was evaluated in numerical simulation, phantom, and real patient cases. In the simulation cases, our method reduced mean HU errors from 44 to 3 HU and from 78 to 9 HU in the full-fan and the half-fan cases, respectively. In both the phantom and the patient cases, image artifacts caused by scatter, such as ring artifacts around the bowtie area, were reduced. With all the techniques employed, we achieved computation time of less than 30 s including the

  12. SU-D-12A-07: Optimization of a Moving Blocker System for Cone-Beam Computed Tomography Scatter Correction

    Energy Technology Data Exchange (ETDEWEB)

    Ouyang, L; Yan, H; Jia, X; Jiang, S; Wang, J [UT Southwestern Medical Center, Dallas, TX (United States); Zhang, H [Southern Medical University, Guangzhou, Guang Dong (China)

    2014-06-01

    Purpose: A moving blocker based strategy has shown promising results for scatter correction in cone-beam computed tomography (CBCT). Different parameters of the system design affect its performance in scatter estimation and image reconstruction accuracy. The goal of this work is to optimize the geometric design of the moving block system. Methods: In the moving blocker system, a blocker consisting of lead strips is inserted between the x-ray source and imaging object and moving back and forth along rotation axis during CBCT acquisition. CT image of an anthropomorphic pelvic phantom was used in the simulation study. Scatter signal was simulated by Monte Carlo calculation with various combinations of the lead strip width and the gap between neighboring lead strips, ranging from 4 mm to 80 mm (projected at the detector plane). Scatter signal in the unblocked region was estimated by cubic B-spline interpolation from the blocked region. Scatter estimation accuracy was quantified as relative root mean squared error by comparing the interpolated scatter to the Monte Carlo simulated scatter. CBCT was reconstructed by total variation minimization from the unblocked region, under various combinations of the lead strip width and gap. Reconstruction accuracy in each condition is quantified by CT number error as comparing to a CBCT reconstructed from unblocked full projection data. Results: Scatter estimation error varied from 0.5% to 2.6% as the lead strip width and the gap varied from 4mm to 80mm. CT number error in the reconstructed CBCT images varied from 12 to 44. Highest reconstruction accuracy is achieved when the blocker lead strip width is 8 mm and the gap is 48 mm. Conclusions: Accurate scatter estimation can be achieved in large range of combinations of lead strip width and gap. However, image reconstruction accuracy is greatly affected by the geometry design of the blocker.

  13. CT能谱成像用于减少锁骨下对比剂伪影的临床研究%Preliminary Study of Spectral CT Imaging in Reducing Beam-hardening Artifact around Subclavian Vein

    Institute of Scientific and Technical Information of China (English)

    葛慧婷; 薛韵菁; 段青

    2013-01-01

    Purpose: To reduce the beam-hardening artifacts (BHAs) around axillary vein and subclavian vein due to the utility of contrast agent in the pulmonary enhanced CT scan by choosing the optimal keV of spectral CT imaging. Methods: Totally 66 patients who received pulmonary enhanced CT scan (Discovery CT750HD) in GSI (Gemstone spectral imaging) mode were included. Twelve sets of CT images were generated including 1 set of 140 kVp conventional polychromatic images and 11 sets of monochromatic images (40, 50, 60, 70, 80, 90, 100, 110, 120, 130 and 140keV). The measurement and comparison of image noise, signal to noise ratio (SNR), contrast to noise ratio (CNR), and average BHAs at 3 different anatomic sites were performed between polychromatic image and each monochromatic image in the arterial phase. BHA was calculated as square root of the difference of noise squares of regions of interest (ROIs) and background. Results: Compared between monochromatic images group and polychromatic images group, BHA could be minimized at 120 keV (p = 0.000), but at the same time, SNR and CNR were obviously decreases, and lead to a significant decrease in soft tissue contrast. Only at 70 keV, BHA could also be reduced (P = 0.042), and the SNR and CNR were the highest, and the artifact area background noise could be reduced, the best image quality could be gotten. Conclusion: For pulmonary enhanced CT scan, 120 keV monochromatic image, which is better than polychromatic images and other monochromatic images in reducing BHA, can be used as the best monochromatic image in reducing the BHA, but the contrast of soft tissue is poor; 70 keV monochromatic image, which provides better SNR and CNR, lower image noise, and lower BHA, is better than 140 kVp polychromatic images. In the practical application, we can combine with 120keV and 70 keV images to make the diagnosis.%目的:寻找CT能谱成像的最佳能量点以减少肺部增强CT扫描锁骨下腋静脉和锁骨下静脉对比剂伪影,

  14. 斜光束对校正滤色器校正精度的影响%Influence of oblique beam on accuracy of correction color filter

    Institute of Scientific and Technical Information of China (English)

    蒋月娟

    2001-01-01

    As the color is measured by the instrument of testing color according to the c ondition prescribed by CIE, oblique beam will be detected by a detector through correction color filter if the distance between a sample and the detector is not long enough. In this case, the equivalent spectral transmittance of correction color filter corresponding to a certain point of detector can be calculated by r evised formula. Taking Y correction color filter as an example, the influence o f oblique beam on correction accuracy of correction color filter is shown by the result of calculation and experiment.%当用测色仪器按照国际照明委员会规定的条件测量物体颜色时,若样品与探测器之间的距离 不够大,则斜光束会透过校正滤色器而被探测器接收,这时对应探测器某点校正滤色器的当 量透射比可以用修正计算式求得。 以“Y” 校正滤色器为例,从计算结果和实验说明 了斜光束对校正滤色器透射比的影响。

  15. A method for simultaneous linear optics and coupling correction for storage rings with turn-by-turn beam position monitor data

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xi [Brookhaven National Laboratory, Upton, Long Island, NY 11973 (United States); Huang, Xiaobiao, E-mail: xiahuang@slac.stanford.edu [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States)

    2016-08-21

    We propose a method to simultaneously correct linear optics errors and linear coupling for storage rings using turn-by-turn (TbT) beam position monitor (BPM) data. The independent component analysis (ICA) method is used to isolate the betatron normal modes from the measured TbT BPM data. The betatron amplitudes and phase advances of the projections of the normal modes on the horizontal and vertical planes are then extracted, which, combined with dispersion measurement, are used to fit the lattice model. The fitting results are used for lattice correction. The method has been successfully demonstrated on the NSLS-II storage ring.

  16. A method for simultaneous linear optics and coupling correction for storage rings with turn-by-turn beam position monitor data

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xi [Brookhaven National Lab. (BNL), Upton, NY (United States); Huang, Xiaobiao [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2016-08-01

    We propose a method to simultaneously correct linear optics errors and linear coupling for storage rings using turn-by-turn (TbT) beam position monitor (BPM) data. The independent component analysis (ICA) method is used to isolate the betatron normal modes from the measured TbT BPM data. The betatron amplitudes and phase advances of the projections of the normal modes on the horizontal and vertical planes are then extracted, which, combined with dispersion measurement, are used to fit the lattice model. Furthermore, the fitting results are used for lattice correction. Our method has been successfully demonstrated on the NSLS-II storage ring.

  17. A method for simultaneous linear optics and coupling correction for storage rings with turn-by-turn beam position monitor data

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xi; Huang, Xiaobiao

    2016-08-01

    We propose a method to simultaneously correct linear optics errors and linear coupling for storage rings using turn-by-turn (TbT) beam position monitor (BPM) data. The independent component analysis (ICA) method is used to isolate the betatron normal modes from the measured TbT BPM data. The betatron amplitudes and phase advances of the projections of the normal modes on the horizontal and vertical planes are then extracted, which, combined with dispersion measurement, are used to fit the lattice model. The fitting results are used for lattice correction. The method has been successfully demonstrated on the NSLS-II storage ring.

  18. A method for simultaneous linear optics and coupling correction for storage rings with turn-by-turn beam position monitor data

    Science.gov (United States)

    Yang, Xi; Huang, Xiaobiao

    2016-08-01

    We propose a method to simultaneously correct linear optics errors and linear coupling for storage rings using turn-by-turn (TbT) beam position monitor (BPM) data. The independent component analysis (ICA) method is used to isolate the betatron normal modes from the measured TbT BPM data. The betatron amplitudes and phase advances of the projections of the normal modes on the horizontal and vertical planes are then extracted, which, combined with dispersion measurement, are used to fit the lattice model. The fitting results are used for lattice correction. The method has been successfully demonstrated on the NSLS-II storage ring.

  19. Patient-specific scatter correction in clinical cone beam computed tomography imaging made possible by the combination of Monte Carlo simulations and a ray tracing algorithm

    DEFF Research Database (Denmark)

    Slot Thing, Rune; Bernchou, Uffe; Mainegra-Hing, Ernesto;

    2013-01-01

    Abstract Purpose. Cone beam computed tomography (CBCT) image quality is limited by scattered photons. Monte Carlo (MC) simulations provide the ability of predicting the patient-specific scatter contamination in clinical CBCT imaging. Lengthy simulations prevent MC-based scatter correction from...... and pelvis scan were simulated within 2% statistical uncertainty in two hours per scan. Within the same time, the ray tracing algorithm provided the primary signal for each of the projections. Thus, all the data needed for MC-based scatter correction in clinical CBCT imaging was obtained within two hours per...

  20. Single-scan scatter correction in CBCT by using projection correlation based view interpolation (PC-VI) and a stationary ring-shaped beam stop array (BSA)

    CERN Document Server

    Yan, Hao; Zhang, Yanbo; Zankl, Maria

    2014-01-01

    In the scatter correction for x-ray Cone Beam (CB) CT, the single-scan scheme with moving Beam Stop Array (BSA) offers reliable scatter measurement with low dose, and by using Projection Correlation based View Interpolation (PC-VI), the primary fluence shaded by the moving BSA (during scatter measurement) could be recovered with high accuracy. However, the moving BSA may increase the mechanical burden in real applications. For better practicability, in this paper we proposed a PC-VI based single-scan scheme with a ring-shaped stationary BSA, which serves as a virtual moving BSA during CB scan, so the shaded primary fluence by this stationary BSA can be also well recovered by PC-VI. The principle in designing the whole system is deduced and evaluated. The proposed scheme greatly enhances the practicability of the single-scan scatter correction scheme.

  1. Analytical $O(\\alpha_s)$ corrections to the beam frame double-spin density matrix elements of $e^+e^-\\to t\\bar t$

    CERN Document Server

    Kaldamäe, L; Körner, J G

    2016-01-01

    We provide analytical results for the $O(\\alpha_s)$ corrections to the double-spin density matrix elements in the reaction $e^+e^-\\to t\\bar t$. These concern the elements $ll$, $lt$, $ln$, $tt$, $tn$, and $nn$ of the double-spin density matrix elements where $l,t,n$ stand for longitudinal, transverse and normal orientations with respect to the beam frame spanned by the electron and the top quark momentum.

  2. Binary moving-blocker-based scatter correction in cone-beam computed tomography with width-truncated projections: proof of concept

    Science.gov (United States)

    Lee, Ho; Fahimian, Benjamin P.; Xing, Lei

    2017-03-01

    This paper proposes a binary moving-blocker (BMB)-based technique for scatter correction in cone-beam computed tomography (CBCT). In concept, a beam blocker consisting of lead strips, mounted in front of the x-ray tube, moves rapidly in and out of the beam during a single gantry rotation. The projections are acquired in alternating phases of blocked and unblocked cone beams, where the blocked phase results in a stripe pattern in the width direction. To derive the scatter map from the blocked projections, 1D B-Spline interpolation/extrapolation is applied by using the detected information in the shaded regions. The scatter map of the unblocked projections is corrected by averaging two scatter maps that correspond to their adjacent blocked projections. The scatter-corrected projections are obtained by subtracting the corresponding scatter maps from the projection data and are utilized to generate the CBCT image by a compressed-sensing (CS)-based iterative reconstruction algorithm. Catphan504 and pelvis phantoms were used to evaluate the method’s performance. The proposed BMB-based technique provided an effective method to enhance the image quality by suppressing scatter-induced artifacts, such as ring artifacts around the bowtie area. Compared to CBCT without a blocker, the spatial nonuniformity was reduced from 9.1% to 3.1%. The root-mean-square error of the CT numbers in the regions of interest (ROIs) was reduced from 30.2 HU to 3.8 HU. In addition to high resolution, comparable to that of the benchmark image, the CS-based reconstruction also led to a better contrast-to-noise ratio in seven ROIs. The proposed technique enables complete scatter-corrected CBCT imaging with width-truncated projections and allows reducing the acquisition time to approximately half. This work may have significant implications for image-guided or adaptive radiation therapy, where CBCT is often used.

  3. Binary moving-blocker-based scatter correction in cone-beam computed tomography with width-truncated projections: proof of concept.

    Science.gov (United States)

    Lee, Ho; Fahimian, Benjamin P; Xing, Lei

    2017-03-21

    This paper proposes a binary moving-blocker (BMB)-based technique for scatter correction in cone-beam computed tomography (CBCT). In concept, a beam blocker consisting of lead strips, mounted in front of the x-ray tube, moves rapidly in and out of the beam during a single gantry rotation. The projections are acquired in alternating phases of blocked and unblocked cone beams, where the blocked phase results in a stripe pattern in the width direction. To derive the scatter map from the blocked projections, 1D B-Spline interpolation/extrapolation is applied by using the detected information in the shaded regions. The scatter map of the unblocked projections is corrected by averaging two scatter maps that correspond to their adjacent blocked projections. The scatter-corrected projections are obtained by subtracting the corresponding scatter maps from the projection data and are utilized to generate the CBCT image by a compressed-sensing (CS)-based iterative reconstruction algorithm. Catphan504 and pelvis phantoms were used to evaluate the method's performance. The proposed BMB-based technique provided an effective method to enhance the image quality by suppressing scatter-induced artifacts, such as ring artifacts around the bowtie area. Compared to CBCT without a blocker, the spatial nonuniformity was reduced from 9.1% to 3.1%. The root-mean-square error of the CT numbers in the regions of interest (ROIs) was reduced from 30.2 HU to 3.8 HU. In addition to high resolution, comparable to that of the benchmark image, the CS-based reconstruction also led to a better contrast-to-noise ratio in seven ROIs. The proposed technique enables complete scatter-corrected CBCT imaging with width-truncated projections and allows reducing the acquisition time to approximately half. This work may have significant implications for image-guided or adaptive radiation therapy, where CBCT is often used.

  4. HARDENING FROG POINTS BY EXPLOSIVE ENERGY,

    Science.gov (United States)

    Experiments were made to determine the most efficient method of strain hardening railroad frog points in order to increase their fatigue resistance...Mechanical strain hardening with rolls 40 mm in diameter under a load of 8 tons produced in standard frogs cast from G13L high-manganese steel (AISI...Hadfield steel) a work-hardened surface layer 3-5 mm thick with a hardness of 340 HB. In other experiments, the frogs were hardened by exploding a

  5. Onycholysis induced by nail hardener.

    Science.gov (United States)

    Helsing, Per; Austad, Joar; Talberg, Hans Jørgen

    2007-10-01

    Nail hardeners appeared in the market during the 1960s. They were basically solutions of formaldehyde. The first adverse effects were published in 1966 (1). Reactions were onycholysis, chromonychia, subungual haemorrhage, and hyperkeratosis. Onycholysis may be non-inflammatory or inflammatory, and is accompanied by throbbing pain. Inflammatory reactions are followed by paronychia and occasional dermatitis on the digital pulpa.

  6. A study of respiration-correlated cone-beam CT scans to correct target positioning errors in radiotherapy of thoracic cancer

    Science.gov (United States)

    Santoro, J. P.; McNamara, J.; Yorke, E.; Pham, H.; Rimner, A.; Rosenzweig, K. E.; Mageras, G. S.

    2012-01-01

    Purpose: There is increasingly widespread usage of cone-beam CT (CBCT) for guiding radiation treatment in advanced-stage lung tumors, but difficulties associated with daily CBCT in conventionally fractionated treatments include imaging dose to the patient, increased workload and longer treatment times. Respiration-correlated cone-beam CT (RC-CBCT) can improve localization accuracy in mobile lung tumors, but further increases the time and workload for conventionally fractionated treatments. This study investigates whether RC-CBCT-guided correction of systematic tumor deviations in standard fractionated lung tumor radiation treatments is more effective than 2D image-based correction of skeletal deviations alone. A second study goal compares respiration-correlated vs respiration-averaged images for determining tumor deviations. Methods: Eleven stage II–IV nonsmall cell lung cancer patients are enrolled in an IRB-approved prospective off-line protocol using RC-CBCT guidance to correct for systematic errors in GTV position. Patients receive a respiration-correlated planning CT (RCCT) at simulation, daily kilovoltage RC-CBCT scans during the first week of treatment and weekly scans thereafter. Four types of correction methods are compared: (1) systematic error in gross tumor volume (GTV) position, (2) systematic error in skeletal anatomy, (3) daily skeletal corrections, and (4) weekly skeletal corrections. The comparison is in terms of weighted average of the residual GTV deviations measured from the RC-CBCT scans and representing the estimated residual deviation over the treatment course. In the second study goal, GTV deviations computed from matching RCCT and RC-CBCT are compared to deviations computed from matching respiration-averaged images consisting of a CBCT reconstructed using all projections and an average-intensity-projection CT computed from the RCCT. Results: Of the eleven patients in the GTV-based systematic correction protocol, two required no correction

  7. DURABILITY OF HARDENED FLY ASH PASTE

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The mechanical properties and durability ( mainly frost-resistance and carbonation resistance ) of fly ash-CaO-CaSO4 .2H2O hardened paste are studied. The relationship among durability of harden ed fly ash paste, the quantity and distribution of hydrates and the initial p aste texture of hardened fly ash paste is presented.

  8. Comparison between measured tissue phantom ratio values and calculated from percent depth doses with and without peak scatter correction factor in a 6 MV beam

    Directory of Open Access Journals (Sweden)

    Ganesh Narayanasamy

    2015-01-01

    Full Text Available The purpose of this study is to examine the accuracy of calculated tissue phantom ratio (TPR data with measured TPR values of a 6MV photon beam. TPR was calculated from the measured percent depth dose (PDD values using 2 methods – with and without correcting for the differences in peak scatter fraction (PSF. Mean error less than 1% was observed between the measured and calculated TPR values with the PSF correction, for all clinically relevant field sizes and depths. When not accounting for the PSF correction, mean difference between the measured and calculated TPR values was larger than 1% for square field sizes ranging from 3 cm to 10 cm.

  9. 一种检测和校正存储器双错的低冗余加固方法%A Low Redundancy Radiation Hardened Scheme for Double Error Detection and Correction in Memories

    Institute of Scientific and Technical Information of China (English)

    祝名; 朱恒静; 刘迎辉; 于庆奎; 唐民

    2014-01-01

    为了提高宇航用存储器的抗单粒子翻转能力,本文对传统的单错误修正、双错误探测(Single Error Correction and Double Error Detection,SEC-DED)码的构造进行了改进和优化,给出了构建单错校正、双错检测、相邻双错校正(Single Error Correction,Double Error Detection and Double Adjacent Error Correction,SEC-DED-DAEC)码奇偶校验矩阵的构造规则.通过适当地增加奇偶校验矩阵列向量的权重和、改变奇偶校验矩阵列向量顺序的方式,提出了一种具有新特征结构的SEC-DED-DAEC码,它可以修正任意相邻两位错误.实验结果表明,提出的SEC-DED-DAEC码是一种有效的宇航用存储器抗单粒子翻转加固措施,其冗余开销基本与传统的SEC-DED码相同,误码率低于国际同类文献的结果.

  10. A breast-specific, negligible-dose scatter correction technique for dedicated cone-beam breast CT: a physics-based approach to improve Hounsfield Unit accuracy

    Science.gov (United States)

    Yang, Kai; Burkett, George, Jr.; Boone, John M.

    2014-11-01

    The purpose of this research was to develop a method to correct the cupping artifact caused from x-ray scattering and to achieve consistent Hounsfield Unit (HU) values of breast tissues for a dedicated breast CT (bCT) system. The use of a beam passing array (BPA) composed of parallel-holes has been previously proposed for scatter correction in various imaging applications. In this study, we first verified the efficacy and accuracy using BPA to measure the scatter signal on a cone-beam bCT system. A systematic scatter correction approach was then developed by modeling the scatter-to-primary ratio (SPR) in projection images acquired with and without BPA. To quantitatively evaluate the improved accuracy of HU values, different breast tissue-equivalent phantoms were scanned and radially averaged HU profiles through reconstructed planes were evaluated. The dependency of the correction method on object size and number of projections was studied. A simplified application of the proposed method on five clinical patient scans was performed to demonstrate efficacy. For the typical 10-18 cm breast diameters seen in the bCT application, the proposed method can effectively correct for the cupping artifact and reduce the variation of HU values of breast equivalent material from 150 to 40 HU. The measured HU values of 100% glandular tissue, 50/50 glandular/adipose tissue, and 100% adipose tissue were approximately 46, -35, and -94, respectively. It was found that only six BPA projections were necessary to accurately implement this method, and the additional dose requirement is less than 1% of the exam dose. The proposed method can effectively correct for the cupping artifact caused from x-ray scattering and retain consistent HU values of breast tissues.

  11. A general framework and review of scatter correction methods in x-ray cone-beam computerized tomography. Part 1: Scatter compensation approaches

    Energy Technology Data Exchange (ETDEWEB)

    Ruehrnschopf, Ernst-Peter; Klingenbeck, Klaus [Siemens AG, Healthcare Sector, Imaging and Therapy Division, Forchheim (Germany)

    2011-07-15

    Since scattered radiation in cone-beam volume CT implies severe degradation of CT images by quantification errors, artifacts, and noise increase, scatter suppression is one of the main issues related to image quality in CBCT imaging. The aim of this review is to structurize the variety of scatter suppression methods, to analyze the common structure, and to develop a general framework for scatter correction procedures. In general, scatter suppression combines hardware techniques of scatter rejection and software methods of scatter correction. The authors emphasize that scatter correction procedures consist of the main components scatter estimation (by measurement or mathematical modeling) and scatter compensation (deterministic or statistical methods). The framework comprises most scatter correction approaches and its validity also goes beyond transmission CT. Before the advent of cone-beam CT, a lot of papers on scatter correction approaches in x-ray radiography, mammography, emission tomography, and in Megavolt CT had been published. The opportunity to avail from research in those other fields of medical imaging has not yet been sufficiently exploited. Therefore additional references are included when ever it seems pertinent. Scatter estimation and scatter compensation are typically intertwined in iterative procedures. It makes sense to recognize iterative approaches in the light of the concept of self-consistency. The importance of incorporating scatter compensation approaches into a statistical framework for noise minimization has to be underscored. Signal and noise propagation analysis is presented. A main result is the preservation of differential-signal-to-noise-ratio (dSNR) in CT projection data by ideal scatter correction. The objective of scatter compensation methods is the restoration of quantitative accuracy and a balance between low-contrast restoration and noise reduction. In a synopsis section, the different deterministic and statistical methods are

  12. Determination and Analysis of Hardenability for Hot-Forging Die Steels with Deep-Hardening

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    ERH end-quenching method was us ed to determine the hardenability of four kinds hot-forging die steels with dee p-hardening and hence the order of their hardenability was given. The tempering hardness of the steels was measured and the tempering resistance was studied. It was approved that ERH method is effective for the determination of hardenability of deep-hardening steel and the beginning of hardness drop in the ERH specimen is caused by bainite occurring.

  13. Optimizing hardenability of high chromium white cast iron

    Institute of Scientific and Technical Information of China (English)

    SU Ying-long; LI Dan; ZHANG Xue-kun

    2006-01-01

    The formulas proposed by J. Dodd and J. L. Parks for calculating the hardenability of high-Cr white cast iron under continuous cooling condition was recommended. For broader application, some supplements were made to the formula. Through tests on the half-cooling time of typical castings, the compositions of ideal alloys were precisely designed using the Dodd's formula. Hardness testing of heat-treated castings showed that the designed compositions were correct. The application of castings demonstrated excellent abrasion resistance.

  14. The assessment of four different correction models applied to the diffuse radiation measured with a shadow ring using global and normal beam radiation measurements for Beer Sheva, Israel

    Energy Technology Data Exchange (ETDEWEB)

    Kudish, Avraham I.; Evseev, Efim G. [Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, E D Bergmann Campus, Beer Sheva 84105 (Israel)

    2008-02-15

    The measurement of the diffuse radiation incident on a horizontal surface, a priori a straightforward task, is fraught with difficulties. It is possible to measure the diffuse radiation by three different techniques: two of which measure it directly and the third indirectly. The most accurate is the indirect one, which is based upon the concurrent measurements of the horizontal global and the normal incidence beam radiation. The disadvantage of this being the relatively expensive tracking system required for measuring the latter. The diffuse radiation can be measured directly with a pyranometer outfitted with either an occulting disk or shadow ring, which prevent the beam radiation from impinging on the pyranometer sensor. The occulting disk can provide accurate measurements of the diffuse radiation but it requires a relatively expensive sun tracking system in the east-west axis. The shadow ring is a stationary device with regard to the east-west axis and blocks the beam radiation component by creating a permanent shadow on the pyranometer sensor. The major disadvantage of the shadow ring is that it also blocks that portion of the diffuse radiation obscured by the shadow ring. This introduces a measurement error that must be corrected to account for that portion of the sky obscured by the shadow band. In addition to this geometric correction factor there is a need to correct for anisotropic sky conditions. Four correction models have been applied to the data for Beer Sheva, Israel and the results have been evaluated both graphically and statistically. An attempt has been made to score the relative performance of the models under different sky conditions. (author)

  15. Hardening of the surface layers of commercial pure titanium VT1-0 under combined treatment

    Science.gov (United States)

    Bashchenko, Lyudmila P.; Gromov, Viktor E.; Budovskikh, Evgenii A.; Ivanov, Yurii F.; Soskova, Nina A.

    2015-10-01

    The treatment of VT1-0 titanium samples was carried out by concentrated energy fluxes. The combined treatment included surface carburizing with the joint use of powder samples of compounds with high physical and mechanical properties (namely, titanium diboride TiB2, silicon carbide SiC and zirconium oxide ZrO2) and subsequent electron beam treatment of surface layers formed in electroexplosive treatment. The combined treatment of surface layers resulted in the multifold increase in microhardness, which reduces depending on the depth of hardening zone. After electron-beam treatment, the depth of hardening zone is increased. During electron-beam treatment, the two-layer hardening zone forms.

  16. Hardening of the surface layers of commercial pure titanium VT1-0 under combined treatment

    Energy Technology Data Exchange (ETDEWEB)

    Bashchenko, Lyudmila P., E-mail: luda.baschenko@gmail.com; Gromov, Viktor E., E-mail: gromov@physics.sibsiu.ru; Budovskikh, Evgenii A., E-mail: budovskih-ea@physics.sibsiu.ru; Soskova, Nina A., E-mail: gromov@physics.sibsiu.ru [Siberian State Industrial University, Novokuznetsk, 654007 (Russian Federation); Ivanov, Yurii F., E-mail: yufi55@mail.ru [Institute of High Current Electronics SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk State University, Tomsk, 634050 (Russian Federation)

    2015-10-27

    The treatment of VT1-0 titanium samples was carried out by concentrated energy fluxes. The combined treatment included surface carburizing with the joint use of powder samples of compounds with high physical and mechanical properties (namely, titanium diboride TiB{sub 2}, silicon carbide SiC and zirconium oxide ZrO{sub 2}) and subsequent electron beam treatment of surface layers formed in electroexplosive treatment. The combined treatment of surface layers resulted in the multifold increase in microhardness, which reduces depending on the depth of hardening zone. After electron-beam treatment, the depth of hardening zone is increased. During electron-beam treatment, the two-layer hardening zone forms.

  17. Surface Fatigue Resistance with Induction Hardening

    Science.gov (United States)

    Townsend, Dennis; Turza, Alan; Chapman, Mike

    1996-01-01

    Induction hardening has been used for some years to harden the surface and improve the strength and service life of gears and other components. Many applications that employ induction hardening require a relatively long time to finish the hardening process and controlling the hardness of the surface layer and its depth often was a problem. Other surface hardening methods, ie., carbonizing, take a very long time and tend to cause deformations of the toothing, whose elimination requires supplementary finishing work. In double-frequency induction hardening, one uses a low frequency for the preheating of the toothed wheel and a much higher frequency for the purpose of rapidly heating the surface by way of surface hardening.

  18. Strain hardening of polymer glasses: Entanglements, energetics, and plasticity

    Science.gov (United States)

    Hoy, Robert S.; Robbins, Mark O.

    2008-03-01

    Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While stress-strain curves for a wide range of temperature can be fit to the functional form predicted by entropic network models, many other results are fundamentally inconsistent with the physical picture underlying these models. Stresses are too large to be entropic and have the wrong trend with temperature. The most dramatic hardening at large strains reflects increases in energy as chains are pulled taut between entanglements rather than a change in entropy. A weak entropic stress is only observed in shape recovery of deformed samples when heated above the glass transition. While short chains do not form an entangled network, they exhibit partial shape recovery, orientation, and strain hardening. Stresses for all chain lengths collapse when plotted against a microscopic measure of chain stretching rather than the macroscopic stretch. The thermal contribution to the stress is directly proportional to the rate of plasticity as measured by breaking and reforming of interchain bonds. These observations suggest that the correct microscopic theory of strain hardening should be based on glassy state physics rather than rubber elasticity.

  19. Energetic model of metal hardening

    Directory of Open Access Journals (Sweden)

    Ignatova O.N.

    2011-01-01

    Full Text Available Based on Bailey hypothesis on the link between strain hardening and elastic lattice defect energy this paper suggests a shear strength energetic model that takes into consideration plastic strain intensity and rate as well as softening related to temperature annealing and dislocation annihilation. Metal strain hardening was demonstrated to be determined only by elastic strain energy related to the energy of accumulated defects. It is anticipated that accumulation of the elastic energy of defects is governed by plastic work. The suggested model has a reasonable agreement with the available experimental data for copper up to P = 70 GPa , for aluminum up to P = 10 GPa and for tantalum up to P = 20 GPa.

  20. Scintillation-Hardened GPS Receiver

    Science.gov (United States)

    Stephens, Donald R.

    2015-01-01

    CommLargo, Inc., has developed a scintillation-hardened Global Positioning System (GPS) receiver that improves reliability for low-orbit missions and complies with NASA's Space Telecommunications Radio System (STRS) architecture standards. A software-defined radio (SDR) implementation allows a single hardware element to function as either a conventional radio or as a GPS receiver, providing backup and redundancy for platforms such as the International Space Station (ISS) and high-value remote sensing platforms. The innovation's flexible SDR implementation reduces cost, weight, and power requirements. Scintillation hardening improves mission reliability and variability. In Phase I, CommLargo refactored an open-source GPS software package with Kalman filter-based tracking loops to improve performance during scintillation and also demonstrated improved navigation during a geomagnetic storm. In Phase II, the company generated a new field-programmable gate array (FPGA)-based GPS waveform to demonstrate on NASA's Space Communication and Navigation (SCaN) test bed.

  1. An aberration-corrected STEM study of structural defects in epitaxial GaN thin films grown by ion beam assisted MBE.

    Science.gov (United States)

    Poppitz, David; Lotnyk, Andriy; Gerlach, Jürgen W; Lenzner, Jörg; Grundmann, Marius; Rauschenbach, Bernd

    2015-06-01

    Ion-beam assisted molecular-beam epitaxy was used for direct growth of epitaxial GaN thin films on super-polished 6H-SiC(0001) substrates. The GaN films with different film thicknesses were studied using reflection high energy electron diffraction, X-ray diffraction, cathodoluminescence and primarily aberration-corrected scanning transmission electron microscopy techniques. Special attention was devoted to the microstructural characterization of GaN thin films and the GaN-SiC interface on the atomic scale. The results show a variety of defect types in the GaN thin films and at the GaN-SiC interface. A high crystalline quality of the produced hexagonal GaN thin films was demonstrated. The gained results are discussed.

  2. Joint statistical correction of clutters, spokes and beam height for a radar derived precipitation climatology in southern Germany

    Directory of Open Access Journals (Sweden)

    A. Wagner

    2012-11-01

    Full Text Available First results of radar derived climatology have emerged over the last years, as datasets of appropriate extent are becoming available. Usually, these statistics are based on time series lasting up to ten years as continuous storage of radar data was often not achieved before. This kind of climatology demands a high level of data quality. Small deviations or minor systematic under- or overestimations in single radar images become a major cause of error in statistical analysis. Extensive corrections of radar data are a crucial prerequisite for radar derived climatology. We present a new statistical post-correction scheme based on a climatological analysis of seven years of radar data of the Munich weather radar (2000–2006 operated by DWD (German Weather Service. Original radar products are used subject only to corrections within the signal processor without any further corrections on single radar images. The aim of this statistical correction is to make up for the average systematic errors caused by clutter, propagation, or measuring effects but to conserve small-scale natural variations in space.

    The statistical correction is based on a thorough analysis of the different causes of possible errors for the Munich weather radar. This analysis revealed the following basic effects: the decrease of rain amount as a function of height and distance from the radar, clutter effects such as clutter remnants after filtering, holes by eliminated clutter or shading effects from obstacles near the radar, visible as spokes, as well as the influence of the bright band. The correction algorithm is correspondingly based on these results. It consists of three modules. The first one is an altitude correction which minimises measuring effects. The second module corrects clutter effects and disturbances and the third one realises a mean adjustment to selected rain gauges. Two different sets of radar products are used. The statistical analysis as well as

  3. A Novel Method and Error Analysis for Beam Optics Measurements and Corrections at the Large Hadron Collider

    CERN Document Server

    Langner, Andy Sven; Rossbach, Jörg; Tomás, Rogelio

    2017-02-17

    The Large Hadron Collider (LHC) is currently the world's largest particle accelerator with the highest center of mass energy in particle collision experiments. The control of the particle beam focusing is essential for the performance reach of such an accelerator. For the characterization of the focusing properties at the LHC, turn-by-turn beam position data is simultaneously recorded at numerous measurement devices (BPMs) along the accelerator, while an oscillation is excited on the beam. A novel analysis method for these measurements ($N$-BPM method) is developed here, which is based on a detailed analysis of systematic and statistical error sources and their correlations. It has been applied during the commissioning of the LHC for operation at an unprecedented energy of 6.5 TeV. In this process a stronger focusing than its design specifications has been achieved. This results in smaller transverse beam sizes at the collision points and allows for a higher rate of particle collisions. For the derivation of ...

  4. HARDENING OF CRANE RAILS BY PLASMA DISCRETE-TIME SURFACE TREATMENT

    Directory of Open Access Journals (Sweden)

    S. S. Samotugin

    2017-01-01

    Full Text Available Crane wheels and rails are subjected to intensive wear in the process of operation. Therefore, improvement of these components’ performance can be considered a task of high importance. A promising direction in this regard is surface treatment by highly concentrated energy flows such as laser beams or plasma jets. This thesis suggests that the use of gradient plasma surface treatment can improve the performance of crane rails. A research was conducted, according to which hardened zones were deposited on crane rails under different treatment modes. Microhardness was measured both at the surface and in depth using custom-made microsections. The article includes the results of study of plasma surface hardening effects on wear resistance of crane rails. Change of plasma surface treatment parameters (current, plasma torch movement speed, argon gas flow rate allows for desired steel hardness and structure, while the choice of optimal location for hardened zones makes it possible to significantly improve wear resistance and crack resistance. As a result of plasma surface hardening, the fine-grained martensite structure is obtained with mainly lamellar morphology and higher hardness rate compared toinduction hardening or overlaying. Wear test of carbon steels revealed that plasma surfacing reduces abrasive wear rate compared to the irinitial state by 2 to 3 times. Enough sharp boundary between hardened and non-hardened portions has a positive effect on the performance of parts under dynamic loads, contributing to the inhibition of cracks during the transition from solid to a soft metal. For carbon and low alloy rail steels, the properties achieved by plasma surface hardening can effectively replace induction hardening or overlaying.The mode range for plasma surface treatment that allow sobtaining a surface layer with certain operating properties has been determined.

  5. Fluence correction factors for graphite calorimetry in a low-energy clinical proton beam: I. Analytical and Monte Carlo simulations.

    Science.gov (United States)

    Palmans, H; Al-Sulaiti, L; Andreo, P; Shipley, D; Lühr, A; Bassler, N; Martinkovič, J; Dobrovodský, J; Rossomme, S; Thomas, R A S; Kacperek, A

    2013-05-21

    The conversion of absorbed dose-to-graphite in a graphite phantom to absorbed dose-to-water in a water phantom is performed by water to graphite stopping power ratios. If, however, the charged particle fluence is not equal at equivalent depths in graphite and water, a fluence correction factor, kfl, is required as well. This is particularly relevant to the derivation of absorbed dose-to-water, the quantity of interest in radiotherapy, from a measurement of absorbed dose-to-graphite obtained with a graphite calorimeter. In this work, fluence correction factors for the conversion from dose-to-graphite in a graphite phantom to dose-to-water in a water phantom for 60 MeV mono-energetic protons were calculated using an analytical model and five different Monte Carlo codes (Geant4, FLUKA, MCNPX, SHIELD-HIT and McPTRAN.MEDIA). In general the fluence correction factors are found to be close to unity and the analytical and Monte Carlo codes give consistent values when considering the differences in secondary particle transport. When considering only protons the fluence correction factors are unity at the surface and increase with depth by 0.5% to 1.5% depending on the code. When the fluence of all charged particles is considered, the fluence correction factor is about 0.5% lower than unity at shallow depths predominantly due to the contributions from alpha particles and increases to values above unity near the Bragg peak. Fluence correction factors directly derived from the fluence distributions differential in energy at equivalent depths in water and graphite can be described by kfl = 0.9964 + 0.0024·zw-eq with a relative standard uncertainty of 0.2%. Fluence correction factors derived from a ratio of calculated doses at equivalent depths in water and graphite can be described by kfl = 0.9947 + 0.0024·zw-eq with a relative standard uncertainty of 0.3%. These results are of direct relevance to graphite calorimetry in low-energy protons but given that the fluence

  6. Over-exposure correction in knee cone-beam CT imaging with automatic exposure control using a partial low dose scan

    Science.gov (United States)

    Choi, Jang-Hwan; Muller, Kerstin; Hsieh, Scott; Maier, Andreas; Gold, Garry; Levenston, Marc; Fahrig, Rebecca

    2016-03-01

    C-arm-based cone-beam CT (CBCT) systems with flat-panel detectors are suitable for diagnostic knee imaging due to their potentially flexible selection of CT trajectories and wide volumetric beam coverage. In knee CT imaging, over-exposure artifacts can occur because of limitations in the dynamic range of the flat panel detectors present on most CBCT systems. We developed a straightforward but effective method for correction and detection of over-exposure for an Automatic Exposure Control (AEC)-enabled standard knee scan incorporating a prior low dose scan. The radiation dose associated with the low dose scan was negligible (0.0042mSv, 2.8% increase) which was enabled by partially sampling the projection images considering the geometry of the knees and lowering the dose further to be able to just see the skin-air interface. We combined the line integrals from the AEC and low dose scans after detecting over-exposed regions by comparing the line profiles of the two scans detector row-wise. The combined line integrals were reconstructed into a volumetric image using filtered back projection. We evaluated our method using in vivo human subject knee data. The proposed method effectively corrected and detected over-exposure, and thus recovered the visibility of exterior tissues (e.g., the shape and density of the patella, and the patellar tendon), incorporating a prior low dose scan with a negligible increase in radiation exposure.

  7. Radiation Hardened Electronics for Extreme Environments

    Science.gov (United States)

    Keys, Andrew S.; Watson, Michael D.

    2007-01-01

    The Radiation Hardened Electronics for Space Environments (RHESE) project consists of a series of tasks designed to develop and mature a broad spectrum of radiation hardened and low temperature electronics technologies. Three approaches are being taken to address radiation hardening: improved material hardness, design techniques to improve radiation tolerance, and software methods to improve radiation tolerance. Within these approaches various technology products are being addressed including Field Programmable Gate Arrays (FPGA), Field Programmable Analog Arrays (FPAA), MEMS Serial Processors, Reconfigurable Processors, and Parallel Processors. In addition to radiation hardening, low temperature extremes are addressed with a focus on material and design approaches.

  8. Investigations of high-frequency induction hardening process for piston rod of shock absorber

    Institute of Scientific and Technical Information of China (English)

    Xianhua Cheng; Qianqian Shangguan

    2005-01-01

    The microhardness of piston rods treated with different induction hardening processes was tested. The experimental results reveal that the depth of the hardened zone is proportional to the ratio of the moving speed of the piston rod to the output power of the induction generator. This result is proved correct through the Finite Element Method (FEM) simulation of the thermal field of induction heating. From tensile and impact tests, an optimized high frequency induction hardening process for piston rods has been obtained, where the output power was 82%×80 kW and the moving speed of workpiece was 5364 mm/min. The piston rods, treated by the optimized high frequency induction hardening process, show the best comprehensive mechanical performance.

  9. Simultaneous surface engineering and bulk hardening of precipitation hardening stainless steel

    DEFF Research Database (Denmark)

    Frandsen, Rasmus Berg; Christiansen, Thomas; Somers, Marcel A. J.

    2006-01-01

    This article addresses simultaneous bulk precipitation hardening and low temperature surface engineering of two commercial precipitation hardening stainless steels: Sandvik Nanoflex® and Uddeholm Corrax®. Surface engineering comprised gaseous nitriding or gaseous carburising. Microstructural....... The duration and temperature of the nitriding/carburising surface hardening treatment can be chosen in agreement with the thermal treatment for obtaining optimal bulk hardness in the precipitation hardening stainless steel....

  10. Fluence correction factors for graphite calorimetry in a low-energy clinical proton beam: I. Analytical and Monte Carlo simulations

    DEFF Research Database (Denmark)

    Palmans, Hugo; Al-Sulaiti, L; Andreo, P

    2013-01-01

    -eq with a relative standard uncertainty of 0.3%. These results are of direct relevance to graphite calorimetry in low-energy protons but given that the fluence correction factor is almost solely influenced by non-elastic nuclear interactions the results are also relevant for plastic phantoms that consist of carbon...

  11. SU-D-207-06: Clinical Validations of Shading Correction for Cone-Beam CT Using Planning CT as a Prior

    Energy Technology Data Exchange (ETDEWEB)

    Tsui, T; Zhu, L [Georgia Institute of Technology, Atlanta, GA (Georgia); Wei, J [Landauer Medical Physics, Newnan, GA (United States)

    2015-06-15

    Purpose: Current cone-beam CT (CBCT) images contain severe shading artifacts mainly due to scatter, hindering their quantitative use in current radiation therapy. We have previously proposed an effective shading correction method for CBCT using planning CT (pCT) as prior knowledge. In this work, we investigate the method robustness via statistical analyses on studies of a large patient group and compare the performance with that of a state-of-the-art method implemented on the current commercial radiation therapy machine -- the Varian Truebeam system. Methods: Since radiotherapy patients routinely undergo multiple-detector CT (MDCT) scans in the planning procedure, we use the high-quality pCT as “free” prior knowledge for CBCT image improvement. The CBCT image with no correction is first spatially registered with the pCT. Primary CBCT projections are estimated via forward projections of the registered image. The low frequency errors in the projections, which stem from mainly scatter, are estimated by filtering the difference between original line integral and the estimated scatter projections. The corrected CBCT image is then reconstructed from the scatter corrected projections. The proposed method is evaluated on 40 cancer patients. Results: On all patient images, we compare errors on CT number, spatial non-uniformity (SNU) and image contrast, using pCT as the ground truth. T-tests show that our algorithm improves over the Varian method on CBCT accuracies of CT number and SNU with 90% confident. The average CT number error is reduced from 54.8 HU on the Varian method to 40.9 HU, and the SNU error is reduced from 7.7% to 3.8%. There is no obvious improvement on image contrast. Conclusion: Large-group patient studies show that the proposed pCT-based algorithm outperforms the Varian method of the Truebeam system on CBCT shading correction, by providing CBCT images with higher CT number accuracy and greater image uniformity.

  12. Ductility and work hardening in nano-sized metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Chen, D. Z., E-mail: dzchen@caltech.edu [Division of Engineering and Applied Sciences, California Institute of Technology, Pasadena, California 91125 (United States); Gu, X. W. [Department of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125 (United States); An, Q.; Goddard, W. A. [Materials and Process Simulation Center, California Institute of Technology, Pasadena, California 91125 (United States); Greer, J. R. [Division of Engineering and Applied Sciences, California Institute of Technology, Pasadena, California 91125 (United States); The Kavli Nanoscience Institute, California Institute of Technology, Pasadena, California 91125 (United States)

    2015-02-09

    In-situ nano-tensile experiments on 70 nm-diameter free-standing electroplated NiP metallic glass nanostructures reveal tensile true strains of ∼18%, an amount comparable to compositionally identical 100 nm-diameter focused ion beam samples and ∼3 times greater than 100 nm-diameter electroplated samples. Simultaneous in-situ observations and stress-strain data during post-elastic deformation reveal necking and work hardening, features uncharacteristic for metallic glasses. The evolution of free volume within molecular dynamics-simulated samples suggests a free surface-mediated relaxation mechanism in nano-sized metallic glasses.

  13. INTOR neutral beam injector concept

    Energy Technology Data Exchange (ETDEWEB)

    Metzler, D.H.; Stewart, L.D.

    1981-01-01

    The US INTOR phase 1 effort in the plasma heating area is described. Positive ion based sources extrapolated from present day technology are proposed. These sources operate at 175 keV beam energy for 6 s. Five injectors - plus one spare - inject 75 MW. Beam energy, source size, interface, radiation hardening, and many other studies are summarized.

  14. Microstructural analysis of ion-irradiation-induced hardening in inconel 718

    Science.gov (United States)

    Hashimoto, N.; Hunn, J. D.; Byun, T. S.; Mansur, L. K.

    2003-05-01

    As an assessment for a possible accelerator beam line window material for the US Spallation Neutron Source (SNS) target, performance, radiation-induced hardening and microstructural evolution in Inconel 718 were investigated in both solution annealed (SA) and precipitation hardened (PH) conditions. Irradiations were carried out using 3.5 MeV Fe +, 370 keV He + and 180 keV H + either singly or simultaneously at 200 °C to simulate the damage and He/H production in the SNS target vessel wall. This resulted in systematic hardening in SA Inconel and gradual net softening in the PH material. TEM microstructural analysis showed the hardening was associated with the formation of small loop and faulted loop structures. Helium-irradiated specimens included more loops and cavities than Fe + ion-irradiated specimens. Softening of the PH material was due to dissolution of the γ '/γ ″ precipitates. High doses of helium were implanted in order to study the effect of high retention of gaseous transmutation products. Simultaneous with the hardening and/or softening due to the displacement damage cascade, helium filled cavities produced additional hardening at high concentrations.

  15. Time-dependent 3-D modelling of laser surface heating for the hardening of metallic materials

    Science.gov (United States)

    Colombo, V.; Mentrelli, A.; Trombetti, T.

    2003-12-01

    A numerical code for the time-dependent three-dimensional modelling of the laser surface heating for the hardening of metallic materials has been developed by the authors. The temperature-dependence of the thermal properties of the material (stainless steel) is taken into account in the frame of a heating process that doesn’t lead to material melting or evaporation. Calculations have been carried out for various dimensions of the parallelepiped-shaped and of the square-shaped spot of the laser beam, as well as for different scanning velocity and for different levels of the laser source power. Various patterns of the laser spot path have also been studied, including a single-pass hardening pattern, a double-pass hardening pattern with and without overlapping, multiple discontinuous and continuous hardening patterns and spiral hardening patterns. The presented results show how the proposed model can be usefully employed in the prediction of the time-evolution of temperature distribution which arises in the workpiece as a consequence of the laser-workpiece interaction under operating conditions typically encountered in industrial applications of the laser hardening process.

  16. Challenges in hardening technologies using shallow-trench isolation

    Energy Technology Data Exchange (ETDEWEB)

    Shaneyfelt, M.R.; Dodd, P.E.; Draper, B.L.; Flores, R.S.

    1998-02-01

    Challenges related to radiation hardening CMOS technologies with shallow-trench isolation are explored. Results show that trench hardening can be more difficult than simply replacing the trench isolation oxide with a hardened field oxide.

  17. Deformation Wave Hardening of Metallic Materials

    Directory of Open Access Journals (Sweden)

    A.V. Kirichek

    2014-07-01

    Full Text Available The article deals with the machine parts hardening by means of deformation waves generated by the impact system with a waveguide as an intermediary member. The conditions for the efficient use of impact energy for elastoplastic deformation of the processed material and creation of the deep hardened surface layer.

  18. Investigation of a Hardened Cement Paste Grout

    DEFF Research Database (Denmark)

    Esteves, Luis Pedro; Sørensen, Eigil Verner

    This report documents a series of tests performed on a hardened cement paste grout delivered by the client, Det Norske Veritas A/S.......This report documents a series of tests performed on a hardened cement paste grout delivered by the client, Det Norske Veritas A/S....

  19. Method of hardening a fluid mass

    NARCIS (Netherlands)

    Zitha, P.L.J.; Jansen, J.D.

    2003-01-01

    The invention relates to a method of hardening a fluid mass in contact with a wall, in a desirable shape. According to the invention, the fluid mass is a magneto-rheological fluid mixture that in addition to at least one hardening component comprises a particulate magnetic component, with minimally

  20. Method of hardening a fluid mass

    NARCIS (Netherlands)

    Zitha, P.L.J.; Jansen, J.D.

    2003-01-01

    The invention relates to a method of hardening a fluid mass in contact with a wall, in a desirable shape. According to the invention, the fluid mass is a magneto-rheological fluid mixture that in addition to at least one hardening component comprises a particulate magnetic component, with minimally

  1. Comparison of Thermal Creep Strain Calculation Results Using Time Hardening and Strain Hardening Rules

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Junehyung; Cheon, Jinsik; Lee, Byoungoon; Lee, Chanbock [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-05-15

    One of the design criteria for the fuel rod in PGSFR is the thermal creep strain of the cladding, because the cladding is exposed to a high temperature for a long time during reactor operation period. In general, there are two kind of calculation scheme for thermal creep strain: time hardening and strain hardening rules. In this work, thermal creep strain calculation results for HT9 cladding by using time hardening and strain hardening rules are compared by employing KAERI's current metallic fuel performance analysis code, MACSIS. Also, thermal creep strain calculation results by using ANL's metallic fuel performance analysis code, LIFE-METAL which adopts strain hardening rule are compared with those by using MACSIS. Thermal creep strain calculation results for HT9 cladding by using time hardening and strain hardening rules were compared by employing KAERI's current metallic fuel performance analysis code, MACSIS. Also, thermal creep strain calculation results by using ANL's metallic fuel performance analysis code, LIFE-METAL which adopts strain hardening rule were compared with those by using MACSIS. Tertiary creep started earlier in time hardening rule than in strain hardening rule. Also, calculation results by MACSIS with strain hardening and those obtained by using LIFE-METAL were almost identical to each other.

  2. A Method of Model Correction of Timoshenko Beam Based on Pareto Front%基于Pareto最优的Timoshenko梁模型修正方法

    Institute of Scientific and Technical Information of China (English)

    王乐; 冷德新

    2015-01-01

    The results of modal test included frequencies and mode shapes of specimen in different status and stages, so multiple objective functions were needed for model correction. A method of model correction of Timoshenko beam based on Pareto front was proposed. The model was corrected through global crossover and mutation, solving the noninferior solution set, defining new fitness of individuals and sorting the noninferior solution set according to crowding distance. The results showed that high precision can be achieved by this method and the Pareto front converged at nonconvex shape. Compared to the results of test, the deviation of the first natural frequency of the corrected model was less than 1%, the deviation of the second natural frequency was less than 6% and the mode shapes were in agreement with test.%模态试验结果中包含试件不同状态不同阶次的频率和振型信息,对动特性模型修正时需要建立多个目标函数.提出一种基于Pareto最优的Timoshenko梁模型修正方法.通过全局交叉和变异操作,求解群体的非劣解集,定义新的个体适应度评价方法,并根据拥挤距离对非劣解集进行排序,对动特性模型进行修正.仿真结果表明,采用该方法能够获得较高的精度,Pareto最优前沿收敛,且形状为非凸,与试验结果相比,修正后的模型一阶频率偏差不超过1%,二阶频率偏差不超过6%,振型与试验结果一致.

  3. Use of rapidly hardening hydroxyapatite cement for facial contouring surgery.

    Science.gov (United States)

    Lee, Dong Won; Kim, Ji Ye; Lew, Dae Hyun

    2010-07-01

    Hydroxyapatite cement is an ideal alloplastic material to replace the autogenous bone grafts in craniofacial surgery. Hydroxyapatite cement is advantageous because it can be easily molded by hand unlike other alloplastic materials such as silicone and high-density polyethylene. For aesthetic applications of hydroxyapatite cement, we evaluated the efficacy and safety of the rapidly hardening hydroxyapatite cement used in facial contour augmentation, especially for the forehead and the malar area. A total of 18 cases of facial skeleton augmentation or contouring surgery using rapidly hardening hydroxyapatite cement (Mimix; Biomet, Warsaw, IN) were examined, and the long-term cosmetic results and any complications were also analyzed. The aims of facial contouring surgeries were to correct the following conditions: hemifacial microsomia, craniosynostosis, posttraumatic facial deformity, deformity after tumor resection, dentofacial deformity, and Romberg disease. The application sites of hydroxyapatite cement were the forehead, malar area, chin, and paranasal area. A mean of 16 g (range, 5-50 g) of the hydroxyapatite cement was used. Postoperative infection, seroma, and migration of the implant were not observed during the follow-up period of 23 months. Rapidly hardening hydroxyapatite cement, Mimix, is easy to manipulate, promptly sclerotized, and can be replaced by living bone tissue, with a low complication rate. Therefore, it can be an optimal treatment that can be used instead of other conventional types of alloplastic materials used in facial contouring surgery.

  4. Advanced module for model parameter extraction using global optimization and sensitivity analysis for electron beam proximity effect correction

    Science.gov (United States)

    Figueiro, Thiago; Choi, Kang-Hoon; Gutsch, Manuela; Freitag, Martin; Hohle, Christoph; Tortai, Jean-Hervé; Saib, Mohamed; Schiavone, Patrick

    2012-11-01

    In electron proximity effect correction (PEC), the quality of a correction is highly dependent on the quality of the model. Therefore it is of primary importance to have a reliable methodology to extract the parameters and assess the quality of a model. Among others the model describes how the energy of the electrons spreads out in the target material (via the Point Spread Function, PSF) as well as the influence of the resist process. There are different models available in previous studies, as well as several different approaches to obtain the appropriate value for their parameters. However, those are restricted in terms of complexity, or require a prohibitive number of measurements, which is limited for a certain PSF model. In this work, we propose a straightforward approach to obtain the value of parameters of a PSF. The methodology is general enough to apply for more sophisticated models as well. It focused on improving the three steps of model calibration procedure: First, it is using a good set of calibration patterns. Secondly, it secures the optimization step and avoids falling into a local optimum. And finally the developed method provides an improved analysis of the calibration step, which allows quantifying the quality of the model as well as enabling a comparison of different models. The methodology described in the paper is implemented as specific module in a commercial tool.

  5. Analysis of Hardened Depth Variability, Process Potential, and Measurement Error in Case Carburized Components

    Science.gov (United States)

    Rowan, Olga K.; Keil, Gary D.; Clements, Tom E.

    2014-12-01

    Hardened depth (effective case depth) measurement is one of the most commonly used methods for carburizing performance evaluation. Variation in direct hardened depth measurements is routinely assumed to represent the heat treat process variation without properly correcting for the large uncertainty frequently observed in industrial laboratory measurements. These measurement uncertainties may also invalidate application of statistical control requirements on hardened depth. Gage R&R studies were conducted at three different laboratories on shallow and deep case carburized components. The primary objectives were to understand the magnitude of the measurement uncertainty and heat treat process variability, and to evaluate practical applicability of statistical control methods to metallurgical quality assessment. It was found that ~75% of the overall hardened depth variation is attributed to the measurement error resulting from the accuracy limitation of microhardness equipment and the linear interpolation technique. The measurement error was found to be proportional to the hardened depth magnitude and may reach ~0.2 mm uncertainty at 1.3 mm nominal depth and ~0.8 mm uncertainty at 3.2mm depth. A case study was discussed to explain a methodology for analyzing a large body of hardened depth information, determination of the measurement error, and calculation of the true heat treat process variation.

  6. Motion and positional error correction for cone beam 3D-reconstruction with mobile C-arms.

    Science.gov (United States)

    Bodensteiner, C; Darolti, C; Schumacher, H; Matthäus, L; Schweikard, A

    2007-01-01

    CT-images acquired by mobile C-arm devices can contain artefacts caused by positioning errors. We propose a data driven method based on iterative 3D-reconstruction and 2D/3D-registration to correct projection data inconsistencies. With a 2D/3D-registration algorithm, transformations are computed to align the acquired projection images to a previously reconstructed volume. In an iterative procedure, the reconstruction algorithm uses the results of the registration step. This algorithm also reduces small motion artefacts within 3D-reconstructions. Experiments with simulated projections from real patient data show the feasibility of the proposed method. In addition, experiments with real projection data acquired with an experimental robotised C-arm device have been performed with promising results.

  7. The influence of Glassex additive on properties of microwave-hardened and self- hardened moulding sands with water glass

    Directory of Open Access Journals (Sweden)

    K. Major-Gabryś

    2012-01-01

    Full Text Available The article takes into consideration the researches concerning inserting the Glassex additive to the microwaved-hardened and self- hardened moulding sands with water glass. In the research different types of ester hardeners to self-hardened moulding sands with water glass were used. The influence of Glassex additive on retained strength of moulding sands with different hardeners and prepared by different technologies of hardening were tested. The influence of different hardeners and the technology of hardening on retained strength of moulding sand with water glass and the Glassex additive were also estimated.

  8. Intraoperative cone-beam CT for correction of periaxial malrotation of the femoral shaft: a surface-matching approach.

    Science.gov (United States)

    Khoury, Amal; Whyne, Cari M; Daly, Michael; Moseley, Douglas; Bootsma, Greg; Skrinskas, Tomas; Siewerdsen, Jeffrey; Jaffray, David

    2007-04-01

    Limb length, alignment and rotation can be difficult to determine in femoral shaft fractures. Shaft axis rotation is particularly difficult to assess intraoperatively. Femoral malpositioning can cause deformity, pain and secondary degenerative joint damage. The aim of this study is to develop an intraoperative method based on cone-beam computed tomography (CBCT) to guide alignment of femoral shaft fractures. We hypothesize that bone surface matching can predict malrotation even with severe comminution. A cadaveric femur was imaged at 16 femoral periaxial malrotations (-51.2 degrees to 60.1 degrees). The images were processed resulting in an unwrapped bone surface plot consisting of a pattern of ridges and valleys. Fracture gaps were simulated by removing midline CT slices. The gaps were reconstituted by extrapolating the existing proximal and distal fragments to the midline of the fracture. The two bone surfaces were then shifted to align bony features. Periaxial malrotation was accurately assessed using surface matching (r2 = 0.99, slope 1.0). The largest mean error was 2.20 degrees and the average difference between repeated measurements was 0.49 degrees. CBCT can provide intraoperative high-resolution images with a large field of view. This quality of imaging enables surface matching algorithms to be utilized even with large areas of comminution.

  9. SU-E-I-05: A Correction Algorithm for Kilovoltage Cone-Beam Computed Tomography Dose Calculations in Cervical Cancer Patients

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, J; Zhang, W; Lu, J [Cancer Hospital of Shantou University Medical College, Shantou, Guangdong (China)

    2015-06-15

    Purpose: To investigate the accuracy and feasibility of dose calculations using kilovoltage cone beam computed tomography in cervical cancer radiotherapy using a correction algorithm. Methods: The Hounsfield units (HU) and electron density (HU-density) curve was obtained for both planning CT (pCT) and kilovoltage cone beam CT (CBCT) using a CIRS-062 calibration phantom. The pCT and kV-CBCT images have different HU values, and if the HU-density curve of CBCT was directly used to calculate dose in CBCT images may have a deviation on dose distribution. It is necessary to normalize the different HU values between pCT and CBCT. A HU correction algorithm was used for CBCT images (cCBCT). Fifteen intensity-modulated radiation therapy (IMRT) plans of cervical cancer were chosen, and the plans were transferred to the pCT and cCBCT data sets without any changes for dose calculations. Phantom and patient studies were carried out. The dose differences and dose distributions were compared between cCBCT plan and pCT plan. Results: The HU number of CBCT was measured by several times, and the maximum change was less than 2%. To compare with pCT, the CBCT and cCBCT has a discrepancy, the dose differences in CBCT and cCBCT images were 2.48%±0.65% (range: 1.3%∼3.8%) and 0.48%±0.21% (range: 0.1%∼0.82%) for phantom study, respectively. For dose calculation in patient images, the dose differences were 2.25%±0.43% (range: 1.4%∼3.4%) and 0.63%±0.35% (range: 0.13%∼0.97%), respectively. And for the dose distributions, the passing rate of cCBCT was higher than the CBCTs. Conclusion: The CBCT image for dose calculation is feasible in cervical cancer radiotherapy, and the correction algorithm offers acceptable accuracy. It will become a useful tool for adaptive radiation therapy.

  10. COMPLEX SURFACE HARDENING OF STEEL ARTICLES

    Directory of Open Access Journals (Sweden)

    A. V. Kovalchuk

    2014-01-01

    Full Text Available The method of complex surface hardening of steel detailswas designed. The method is a compound of two processes of hardening: chemical heat treatment and physical vapor deposition (PVD of the coating. The result, achieved in this study is much higher, than in other work on this topic and is cumulative. The method designed can be used in mechanical engineering, medicine, energetics and is perspective for military and space technologies.

  11. Properties and Commercial Application of Manual Plasma Hardening

    Science.gov (United States)

    Korotkov, V. A.

    2016-11-01

    A new method and a device for plasma hardening of various parts are considered. Installation of the new device does not require too much investment (the active mechanical productions are appropriate for its accommodation) and special choice of personnel (welders train to use it without difficulty). Plasma hardening does not deform and worsen the smoothness of the surface, which makes it possible to employ many hardened parts without finishing mechanical treatment required after bulk or induction hardening. The hardened layer (about 1 mm) produced by plasma hardening exhibits better wear resistance than after bulk hardening with tempering, which prolongs the service life of the parts.

  12. Infrared Camera Analysis of Laser Hardening

    Directory of Open Access Journals (Sweden)

    J. Tesar

    2012-01-01

    Full Text Available The improvement of surface properties such as laser hardening becomes very important in present manufacturing. Resulting laser hardening depth and surface hardness can be affected by changes in optical properties of material surface, that is, by absorptivity that gives the ratio between absorbed energy and incident laser energy. The surface changes on tested sample of steel block were made by engraving laser with different scanning velocity and repetition frequency. During the laser hardening the process was observed by infrared (IR camera system that measures infrared radiation from the heated sample and depicts it in a form of temperature field. The images from the IR camera of the sample are shown, and maximal temperatures of all engraved areas are evaluated and compared. The surface hardness was measured, and the hardening depth was estimated from the measured hardness profile in the sample cross-section. The correlation between reached temperature, surface hardness, and hardening depth is shown. The highest and the lowest temperatures correspond to the lowest/highest hardness and the highest/lowest hardening depth.

  13. Characterization of radiation beams used to determinate the correction factor for a CyberKnife® unit reference field using ionization chambers

    Energy Technology Data Exchange (ETDEWEB)

    Aragón-Martínez, Nestor, E-mail: nestoraragon@fisica.unam.mx; Massillon-JL, Guerda, E-mail: massillon@fisica.unam.mx [Instituto de Física, Universidad Nacional Autónoma de México, D.F (Mexico); Gómez-Muñoz, Arnulfo [Hospital de Oncología, Centro Médico Nacional Siglo XXI, D.F (Mexico)

    2014-11-07

    This paper aimed to characterize a 6 MV x-ray beam from a Varian® iX linear accelerator in order to obtain the correction factors needed by the IAEA/AAPM new formalism{sup 1}. The experiments were performed in a liquid water phantom under different irradiation conditions: a) Calibration of the reference field of 10 cm × 10 cm at 90 cm SSD and 10 cm depth was carried out according to the TRS-398 protocol using three ionization chambers (IC) calibrated in different reference laboratory and b) Measurement of the absorbed dose rate at 70 cm SSD and 10 cm depth in a 10 cm × 10 cm and 5.4 cm × 5.4 cm fields was obtained in order to simulate the CyberKnife® conditions where maximum distance between the source and the detector is equal to 80 cm and the maximum field size is 6 cm diameter. Depending where the IC was calibrated, differences between 0.16% and 2.24% in the absorbed dose rate measured in the 10 cm × 10 cm field at 90 cm SSD were observed, while for the measurements at 70 cm SSD, differences between 1.27% and 3.88% were obtained. For the 5.4 cm × 5.4 cm field, the absorbed dose measured with the three ICs varies between 1.37% and 3.52%. The increase in the difference on the absorbed dose when decreasing the SSD could possibly be associated to scattering radiation generated from the collimators and/or the energy dependence of the ionization chambers to low-energy radiation. The results presented in this work suggest the importance of simulating the CyberKnife® conditions using other linear accelerator for obtaining the correction factors as proposed by the IAEA/AAPM new formalism in order to measure the absorbed dose with acceptable accuracy.

  14. Characterization of radiation beams used to determinate the correction factor for a CyberKnife® unit reference field using ionization chambers

    Science.gov (United States)

    Aragón-Martínez, Nestor; Gómez-Muñoz, Arnulfo; Massillon-JL, Guerda

    2014-11-01

    This paper aimed to characterize a 6 MV x-ray beam from a Varian® iX linear accelerator in order to obtain the correction factors needed by the IAEA/AAPM new formalism1. The experiments were performed in a liquid water phantom under different irradiation conditions: a) Calibration of the reference field of 10 cm × 10 cm at 90 cm SSD and 10 cm depth was carried out according to the TRS-398 protocol using three ionization chambers (IC) calibrated in different reference laboratory and b) Measurement of the absorbed dose rate at 70 cm SSD and 10 cm depth in a 10 cm × 10 cm and 5.4 cm × 5.4 cm fields was obtained in order to simulate the CyberKnife® conditions where maximum distance between the source and the detector is equal to 80 cm and the maximum field size is 6 cm diameter. Depending where the IC was calibrated, differences between 0.16% and 2.24% in the absorbed dose rate measured in the 10 cm × 10 cm field at 90 cm SSD were observed, while for the measurements at 70 cm SSD, differences between 1.27% and 3.88% were obtained. For the 5.4 cm × 5.4 cm field, the absorbed dose measured with the three ICs varies between 1.37% and 3.52%. The increase in the difference on the absorbed dose when decreasing the SSD could possibly be associated to scattering radiation generated from the collimators and/or the energy dependence of the ionization chambers to low-energy radiation. The results presented in this work suggest the importance of simulating the CyberKnife® conditions using other linear accelerator for obtaining the correction factors as proposed by the IAEA/AAPM new formalism in order to measure the absorbed dose with acceptable accuracy.

  15. Organoapatites: materials for artificial bone. II. Hardening reactions and properties.

    Science.gov (United States)

    Stupp, S I; Mejicano, G C; Hanson, J A

    1993-03-01

    This article reports on chemical reactions and the properties they generated in artificial bone materials termed "organoapatites." These materials are synthesized using methodology we reported in the previous article of this series. Two different processes were studied here for the transition from organoapatite particles to implants suitable for the restoration of the skeletal system. One process involved the hardening of powder compacts by beams of blue light derived from a lamp or a laser and the other involved pressure-induced interdiffusion of polymers. In both cases, the hardening reaction involved the formation of a polyion complex between two polyelectrolytes. In the photo-induced reaction an anionic electrolyte polymerizes to form the coulombic network and in the pressure-induced one, pressure forms the complex by interdiffusion of two polyions. Model reactions were studied using various polycations. Based on these results the organoapatite selected for the study was that containing dispersed poly(L-lysine) and sodium acrylate as the anionic monomer. The organomineral particles can be pressed at room temperature into objects of great physical integrity and hydrolytic stability relative to anorganic controls. The remarkable fact about these objects is that intimate molecular dispersion of only 2-3% by weight organic material provides integrity to the mineral network in an aqueous medium and also doubles its tensile strength. This integrity is essentially nonexistent in "anorganic" samples prepared by the same methodology used in organoapatite synthesis. The improvement in properties was most effectively produced by molecular bridges formed by photopolymerization. The photopolymerization leads to the "hardening" of pellets prepared by pressing of organoapatite powders. The reaction was found to be more facile in the microstructure of the organomineral, and it is potentially useful in the surgical application of organoapatites as artificial bone.

  16. Influence and Analysis of Concentrate Degree of Plasma Arc for Heat Process of Hardening Treatment

    Institute of Scientific and Technical Information of China (English)

    WANG Shuo-gui; YAN Hong-ri

    2004-01-01

    According to the practicable model of the plasma arc surface quench, the influence law of the heat process、cooling course、 temperature field about surface quench treatment by plasma arc due to the concentrate degree of plasma arc heat source are discussed in this paper. It shows that the concentrate degree of plasma arc heat source can change the width of the hardening zone and can not change the maximum harden depth. With the increase of the concentrate degree, the area of the heat influence zone is decreased and its shape is narrowed after the heat source. Relative to cooling rate, the influence of the heat source concentrate degree for heat absorption is bigger. The correctness of the practical model are proved with experimental results for quench hardening of 45# steel by plasma arc.

  17. Influence and Analysis of Concentrate Degree of Plasma Arc for Heat Process of Hardening Treatment

    Institute of Scientific and Technical Information of China (English)

    WANGShuo-gui; YANHong-ri

    2004-01-01

    According to the practicable model of the plasma arc surtace quench, the influence law ot me heat process, cooling course, temperature field about surface quench treatment by plasma arc due to the concentrate degree of plasma arc heat source are discussed in this paper. It shows that the concentrate degree of plasma arc heat source can change the width of the hardening zone and can not change the maximum harden depth. With the increase of the concentrate degree, the area of the heat influence zone is decreased and its shape is narrowed after the heat source. Relative to cooling rate, the influence of the heat source concentrate degree for heat absorption is bigger. The correctness of the practical model are proved with experimental results for quench hardening of 45# steel by plasma arc.

  18. PET measurements of cerebral metabolism corrected for CSF contributions

    Energy Technology Data Exchange (ETDEWEB)

    Chawluk, J.; Alavi, A.; Dann, R.; Kushner, M.J.; Hurtig, H.; Zimmerman, R.A.; Reivich, M.

    1984-01-01

    Thirty-three subjects have been studied with PET and anatomic imaging (proton-NMR and/or CT) in order to determine the effect of cerebral atrophy on calculations of metabolic rates. Subgroups of neurologic disease investigated include stroke, brain tumor, epilepsy, psychosis, and dementia. Anatomic images were digitized through a Vidicon camera and analyzed volumetrically. Relative areas for ventricles, sulci, and brain tissue were calculated. Preliminary analysis suggests that ventricular volumes as determined by NMR and CT are similar, while sulcal volumes are larger on NMR scans. Metabolic rates (18F-FDG) were calculated before and after correction for CSF spaces, with initial focus upon dementia and normal aging. Correction for atrophy led to a greater increase (%) in global metabolic rates in demented individuals (18.2 +- 5.3) compared to elderly controls (8.3 +- 3.0,p < .05). A trend towards significantly lower glucose metabolism in demented subjects before CSF correction was not seen following correction for atrophy. These data suggest that volumetric analysis of NMR images may more accurately reflect the degree of cerebral atrophy, since NMR does not suffer from beam hardening artifact due to bone-parenchyma juxtapositions. Furthermore, appropriate correction for CSF spaces should be employed if current resolution PET scanners are to accurately measure residual brain tissue metabolism in various pathological states.

  19. Hardening of graphite surface by ion beam amorphization

    Energy Technology Data Exchange (ETDEWEB)

    Hirvonen, J.P.; Stone, D.; Nastasi, M.; Hannula, S.P.

    1986-05-01

    Ion implantation has been shown to possess potential as a practical method for improving the mechanical properties of surfaces. So far a number of tests have been performed. In these studies, metals - most often steels or other hard materials - have been used. However, the improvement of the mechanical properties at the surface is not only important for substances that already have considerable hardness, but also for materials with other unique properties. Graphite is useful in many applications. Mechanically, it is easily machined and has good dimensional stability. It has self lubricity and under certain conditions has excellent sliding properties. Chemically, it is generally impermeable, resistant to corrosion, and compatable with mating materials. It is a good conductor of both heat and electrical current. The ion implantation of graphite has been studied elsewhere but without reference to the mechanical properties of the surface. It is expected, however, that heavy ion bombardment will cause structural changes at the graphite surface resulting in a modification of the mechanical properties. In this investigation the authors focus on these properties. The main objectives have been to study how the surface mechanical properties are changed by an ion bombardment and to find the relationship between mechanical properties and microstructure.

  20. Modeling of Irradiation Hardening of Polycrystalline Materials

    Energy Technology Data Exchange (ETDEWEB)

    Li, Dongsheng; Zbib, Hussein M.; Garmestani, Hamid; Sun, Xin; Khaleel, Mohammad A.

    2011-09-14

    High energy particle irradiation of structural polycrystalline materials usually produces irradiation hardening and embrittlement. The development of predict capability for the influence of irradiation on mechanical behavior is very important in materials design for next generation reactors. In this work a multiscale approach was implemented to predict irradiation hardening of body centered cubic (bcc) alpha-iron. The effect of defect density, texture and grain boundary was investigated. In the microscale, dislocation dynamics models were used to predict the critical resolved shear stress from the evolution of local dislocation and defects. In the macroscale, a viscoplastic self-consistent model was applied to predict the irradiation hardening in samples with changes in texture and grain boundary. This multiscale modeling can guide performance evaluation of structural materials used in next generation nuclear reactors.

  1. An Anisotropic Hardening Model for Springback Prediction

    Science.gov (United States)

    Zeng, Danielle; Xia, Z. Cedric

    2005-08-01

    As more Advanced High-Strength Steels (AHSS) are heavily used for automotive body structures and closures panels, accurate springback prediction for these components becomes more challenging because of their rapid hardening characteristics and ability to sustain even higher stresses. In this paper, a modified Mroz hardening model is proposed to capture realistic Bauschinger effect at reverse loading, such as when material passes through die radii or drawbead during sheet metal forming process. This model accounts for material anisotropic yield surface and nonlinear isotropic/kinematic hardening behavior. Material tension/compression test data are used to accurately represent Bauschinger effect. The effectiveness of the model is demonstrated by comparison of numerical and experimental springback results for a DP600 straight U-channel test.

  2. Induction surface hardening of hard coated steels

    DEFF Research Database (Denmark)

    Pantleon, Karen; Kessler, Olaf; Hoffmann, Franz

    1999-01-01

    -process is the high deposition temperature, consequently the properties of steel substrates are negatively influenced. Therefore, a subsequent heat treatment of the coated steels is necessary to restore the properties of steels ready for operation. Induction surface hardening is used as a method of heat treatment....... The effect of induction surface hardening on the properties of the coating-substrate-systems is mainly characterized using investigations of microstructure and chemical composition as well as measurements of hardness and residual stresses in dependence on the distance from the surface. Furthermore......, the scratch test is used to estimate critical loads for cohesive and adhesive failure of the coatings. Additionally, distortion measurements are carried out. The results emphasize the advantage of induction surface hardening as a method of subsequent heat treatment of CVD-coated steels....

  3. A novel radiation hardened by design latch

    Institute of Scientific and Technical Information of China (English)

    Huang Zhengfeng; Liang Huaguo

    2009-01-01

    Due to aggressive technology scaling, radiation-induced soft errors have become a serious reliability concern in VLSI chip design. This paper presents a novel radiation hardened by design latch with high single-event-upset (SEU) immunity. The proposed latch can effectively mitigate SEU by internal dual interlocked scheme. The propagation delay, power dissipation and power delay product of the presented latch are evaluated by detailed SPICE simulations. Compared with previous SEU-hardening solutions such as TMR-Latch, the presented latch is more area efficient, delay and power efficient. Fault injection simulations also demonstrate the robustness of the presented latch even under high energy particle strikes.

  4. "Work-Hardenable" ductile bulk metallic glass.

    Science.gov (United States)

    Das, Jayanta; Tang, Mei Bo; Kim, Ki Buem; Theissmann, Ralf; Baier, Falko; Wang, Wei Hua; Eckert, Jürgen

    2005-05-27

    Usually, monolithic bulk metallic glasses undergo inhomogeneous plastic deformation and exhibit poor ductility (< 1%) at room temperature. We present a new class of bulk metallic glass, which exhibits high strength of up to 2265 MPa together with extensive "work hardening" and large ductility of 18%. Significant increase in the flow stress was observed during deformation. The "work-hardening" capability and ductility of this class of metallic glass is attributed to a unique structure correlated with atomic-scale inhomogeneity, leading to an inherent capability of extensive shear band formation, interactions, and multiplication of shear bands.

  5. Radiation hardening revisited: Role of intracascade clustering

    DEFF Research Database (Denmark)

    Singh, B.N.; Foreman, A.J.E.; Trinkaus, H.

    1997-01-01

    be explained in terms of conventional dispersed-barrier hardening because (a) the grown-in dislocations are not free, and (b) irradiation-induced defect clusters are not rigid indestructible Orowan obstacles. A new model called 'cascade-induced source hardening' is presented where glissile loops produced...... directly in cascades are envisaged to decorate the grown-in dislocations so that they cannot act as dislocation sources. The upper yield stress is related to the breakaway stress which is necessary to pull the dislocation away from the clusters/loops decorating it. The magnitude of the breakaway stress has...

  6. Plasma Arc Surface Hardening Robot Technology

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In national economy and national defense, a lot of ma chine components become worthless early because of wear and tear and corrode. It leads to huge loss of resource and material. Surface hardening of the steel cou ld form a hard, wearable, corrode-resisting layer on the surface to enhance the mechanical property of the machine component. From 1980s, there is a new method of surface hardening that is heating with plasma arc. It overcomes the shortage of old methods and is adopted in automotive product ...

  7. Investigation of Hardened Filling Grout Samples

    DEFF Research Database (Denmark)

    Sørensen, Eigil V.

     Suzlon Wind Energy A/S requested on August 28, 2007 an investigation of 2 samples of a hardened filling grout to be carried out, comprising drilling and strength determination of 4 test cylinders, and description of the surface characteristics of the samples....... Suzlon Wind Energy A/S requested on August 28, 2007 an investigation of 2 samples of a hardened filling grout to be carried out, comprising drilling and strength determination of 4 test cylinders, and description of the surface characteristics of the samples....

  8. Induction surface hardening of hard coated steels

    DEFF Research Database (Denmark)

    Pantleon, Karen; Kessler, Olaf; Hoffmann, Franz

    1999-01-01

    . The effect of induction surface hardening on the properties of the coating-substrate-systems is mainly characterized using investigations of microstructure and chemical composition as well as measurements of hardness and residual stresses in dependence on the distance from the surface. Furthermore......, the scratch test is used to estimate critical loads for cohesive and adhesive failure of the coatings. Additionally, distortion measurements are carried out. The results emphasize the advantage of induction surface hardening as a method of subsequent heat treatment of CVD-coated steels....

  9. Atomistic interpretation of solid solution hardening from spectral analysis.

    Science.gov (United States)

    Plendl, J N

    1971-05-01

    From analysis of a series of vibrational spectra of ir energy absorption and laser Raman, an attempt is made to interpret solid solution hardening from an atomistic point of view for the system CaF(2)/SrF(2). It is shown to be caused by the combined action of three atomic characteristics, i.e., their changes as a function of composition. They are deformation of the atomic coordination polyhedrons, overlap of the outer electron shells of the atom pairs, and the ratio of the ionic to covalent share of binding. A striking nonlinear behavior of the three characteristics, as a function of composition, gives maximum atomic bond strength to the 55/45 position of the system CaF(2)/SrF(2), in agreement with the measured data of the solid solution hardening. The curve for atomic bond strength, derived from the three characteristics, is almost identical to the curve for measured microhardness data. This result suggests that the atomistic interpretation, put forward in this paper, is correct.

  10. Monte Carlo simulated corrections for beam commissioning measurements with circular and MLC shaped fields on the CyberKnife M6 System: a study including diode, microchamber, point scintillator, and synthetic microdiamond detectors

    Science.gov (United States)

    Francescon, P.; Kilby, W.; Noll, J. M.; Masi, L.; Satariano, N.; Russo, S.

    2017-02-01

    Monte Carlo simulation was used to calculate correction factors for output factor (OF), percentage depth-dose (PDD), and off-axis ratio (OAR) measurements with the CyberKnife M6 System. These include the first such data for the InCise MLC. Simulated detectors include diodes, air-filled microchambers, a synthetic microdiamond detector, and point scintillator. Individual perturbation factors were also evaluated. OF corrections show similar trends to previous studies. With a 5 mm fixed collimator the diode correction to convert a measured OF to the corresponding point dose ratio varies between  -6.1% and  -3.5% for the diode models evaluated, while in a 7.6 mm  ×  7.7 mm MLC field these are  -4.5% to  -1.8%. The corresponding microchamber corrections are  +9.9% to  +10.7% and  +3.5% to  +4.0%. The microdiamond corrections have a maximum of  -1.4% for the 7.5 mm and 10 mm collimators. The scintillator corrections are  15%, reducing to    d max were  stopping power perturbations. The microdiamond OAR corrections were  <3% outside the beam. This paper provides OF corrections that can be used for commissioning new CyberKnife M6 Systems and retrospectively checking estimated corrections used previously. We recommend the PDD and OAR corrections are used to guide detector selection and inform the evaluation of results rather than to explicitly correct measurements.

  11. Theoretical investigation of the saturation correction for ionization chambers irradiated with pulsed beams of arbitrary pulse length; Theoretische Untersuchung der Saettigungskorrektion von Ionisationskammern in gepulsten Strahlungsfeldern bei beliebiger Pulsdauer

    Energy Technology Data Exchange (ETDEWEB)

    Karsch, Leonhard; Pawelke, Joerg [OncoRay - National Center for Radiation Research in Oncology, Dresden (Germany)

    2014-10-01

    In ionization chambers, not all released charge is collected due to the recombination of charge carriers. This effect is taken into account by the saturation correction factor k{sub S}. A physical description of the correction factor has been established for pulsed radiation. However, it is only accurate when the pulse length is short compared with the collection time of the ionization chamber. In this paper we develop a description of the saturation correction for radiation pulses of arbitrary length. For this, a system of partial differential equations is solved iteratively. The numerical solutions are verified experimentally for a Roos ionization chamber (PTW TM34001) exposed to a pulsed electron beam. The results of this iterative procedure describe the experimental data well. The calculations are also possible for beam structures which are experimentally hard to get and thereby contribute to a better understanding and correct description of the saturation correction at arbitrary pulse length. Among other things the pulse length dependent distributions of the charge carriers in the ionization chamber is calculated, inclusive of the transition to the conditions prevailing in the case of continuous irradiation. Furthermore is shown that the formula for k{sub S} established by Hochhaeuser and Balk is applicable even at arbitrary pulse length, if pulse duration dependent effective values are used for the parameters a and p. These effective values have been determined for the Roos chamber at pulse lengths up to 300 μs. (orig.)

  12. HTPro: Low-temperature Surface Hardening of Stainless Steel

    DEFF Research Database (Denmark)

    Christiansen, Thomas Lundin; Somers, Marcel A. J.

    2013-01-01

    Low-temperature surface hardening of stainless steel provides the required performance properties without affecting corrosion resistance.......Low-temperature surface hardening of stainless steel provides the required performance properties without affecting corrosion resistance....

  13. Self hardening property of Botswana fly ash | Sahu | Botswana ...

    African Journals Online (AJOL)

    Self hardening property of Botswana fly ash. ... In the present investigation, an effort has been made to study the self hardening property of Botswana fly ash by ... This will encourage the use of fly ash economically as a construction material.

  14. Feasibility Studies on Underwater Laser Surface Hardening Process

    OpenAIRE

    Biao Jin; Min Li; TaeWoo Hwang; YoungHoon Moon

    2015-01-01

    Laser surface hardening process is a very promising hardening method for ferrous and nonferrous alloys where transformations occur during cooling after laser melting in the solid state. This study experimentally characterizes laser surface hardening of tool steel in both water and air. For the underwater operation, laser surface scanning is performed over the tool steel surface which is immersed in water. The laser surface hardening tests are performed with a maximum 200 W fiber laser with a ...

  15. CASE-HARDENING OF STAINLESS STEEL

    DEFF Research Database (Denmark)

    2004-01-01

    The invention relates to case-hardening of a stainless steel article by means of gas including carbon and/or nitrogen, whereby carbon and/or nitrogen atoms diffuse through the surface into the article. The method includes activating the surface of the article, applying a top layer on the activated...

  16. Instabilities in power law gradient hardening materials

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Tvergaard, Viggo

    2005-01-01

    Tension and compression instabilities are investigated for specimens with dimensions in the micron range. A finite strain generalization of a higher order strain gradient plasticity theory is implemented in a finite element scheme capable of modeling power law hardening materials. Effects...

  17. A New Method of Hardening Inner Wall of Long Pipe

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A new laser inner wall hardening method for long pipe mas introduced. The system combines laser surface hardening with robot moving in pipeline. Some craft experiments have been done with this system and optimum parameters of laser hardening have been found.

  18. Study on Laser Transformation Hardening of HT250 by High Speed Axis Flow CO2 Laser

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    In this article, laser transformation hardening of HT250 material by high speed axis flow CO2 laser was investigated for first time in China. Appropriate laser hardening parameters, such as laser energy power P(W), laser scanning rate V(m/min),were optimized through a number of experiments. The effect of the mentioned parameters on the hardened zone, including its case depth, microhardness distributions etc., were analyzed. Through the factual experiments, it is proved that axial flow CO2 laser, which commonly outputs low mode laser beam, can also treat materials as long as the treating parameters used are rational. During the experiments, the surface qualities of some specimens treated by some parameters were found to be enhanced, which does not coincide with the former results. Furthermore in the article, the abnormal phenomenon observed in the experiments is discussed. According to the experimental results, the relationship between laser power density q and scanning rate V is shown in a curve and the corresponding formulation, which have been proved to be valuable for choosing the parameters of laser transformation hardening by axial flow CO2 lasers, was also given.

  19. Evaluation of Retro recon for SRS planning correction according to the error of recognize to coordinate

    Energy Technology Data Exchange (ETDEWEB)

    Moon, Hyeon Seok; Jeong, Deok Yang; Do, Gyeong Min; Lee, Yeong Cheol; KIm, Sun Myung; Kim, Young Bun [Dept. of Radiation Oncology, Korea University Guro Hospital, Seoul (Korea, Republic of)

    2016-12-15

    The purpose of this study was to evaluate the Retro recon in SRS planning using BranLAB when stereotactic location error occurs by metal artifact. By CT simulator, image were acquired from head phantom(CIRS, PTW, USA). To observe stereotactic location recognizing and beam hardening, CT image were approved by SRS planning system(BrainLAB, Feldkirchen, Germany). In addition, we compared acquisition image(1.25mm slice thickness) and Retro recon image(using for 2.5 mm, 5mm slice thickness). To evaluate these three images quality, the test were performed by AAPM phantom study. In patient, it was verified stereotactic location error. All the location recognizing error did not occur in scanned image of phantom. AAPM phantom scan images all showed the same trend. Contrast resolution and Spatial resolution are under 6.4 mm, 1.0 mm. In case of noise and uniformity, under 11, 5 of HU were measured. In patient, the stereotactic location error was not occurred at reconstructive image. For BrainLAB planning, using Retro recon were corrected stereotactic error at beam hardening. Retro recon may be the preferred modality for radiation treatment planning and approving image quality.

  20. Origin of the Cosmic Ray Spectral Hardening

    CERN Document Server

    Tomassetti, N

    2012-01-01

    Recent data from ATIC, CREAM and PAMELA indicate that the cosmic ray energy spectra of protons and nuclei exhibit a remarkable hardening at energies above 100 GeV per nucleon. We propose that the hardening is an interstellar propagation effect that originates from a spatial change of the cosmic ray transport properties in different regions of the Galaxy. The key hypothesis is that the diffusion coefficient is not separable into energy and space variables as usually assumed. Under this scenario, we can reproduce well the observational data. Our model has several implications for the cosmic ray acceleration/propagation physics and can be tested by ongoing experiments such as AMS or Fermi/LAT.

  1. Construction procedures using self hardening fly ash

    Science.gov (United States)

    Thornton, S. I.; Parker, D. G.

    1980-07-01

    Fly ash produced in Arkansas from burning Wyoming low sulfur coal is self-hardening and can be effective as a soil stabilizing agent for clays and sands. The strength of soil-self hardening fly ash develops rapidly when compacted immediately after mixing. Seven day unconfined compressive strengths up to 1800 psi were obtained from 20% fly ash and 80% sand mixtures. A time delay between mixing the fly ash with the soil and compaction of the mixture reduced the strength. With two hours delay, over a third of the strength was lost and with four hours delay, the loss was over half. Gypsum and some commercial concrete retarders were effective in reducing the detrimental effect of delayed compaction. Adequate mixing of the soil and fly ash and rapid compaction of the mixtures were found to be important parameters in field construction of stabilized bases.

  2. Radiation-hardened transistor and integrated circuit

    Science.gov (United States)

    Ma, Kwok K.

    2007-11-20

    A composite transistor is disclosed for use in radiation hardening a CMOS IC formed on an SOI or bulk semiconductor substrate. The composite transistor has a circuit transistor and a blocking transistor connected in series with a common gate connection. A body terminal of the blocking transistor is connected only to a source terminal thereof, and to no other connection point. The blocking transistor acts to prevent a single-event transient (SET) occurring in the circuit transistor from being coupled outside the composite transistor. Similarly, when a SET occurs in the blocking transistor, the circuit transistor prevents the SET from being coupled outside the composite transistor. N-type and P-type composite transistors can be used for each and every transistor in the CMOS IC to radiation harden the IC, and can be used to form inverters and transmission gates which are the building blocks of CMOS ICs.

  3. RADIATION HARDENED ANALOG IC FOR SENSOR

    Directory of Open Access Journals (Sweden)

    O. V. Dvornikov

    2011-01-01

    Full Text Available Problems of specialized analog integrated circuit design for sensor equipments are considered. It is offered to produce of radiation hardened analog IC on structured chips for economic efficiency at small production volume. The approach to analog IC design is described, including recommendations for choice of: types and quantities of structured chip analogue components; active and passive components; schematic decisions of analogue components with programmed parameters and small sensitivity to radiation. 

  4. Dislocation Multi-junctions and Strain Hardening

    Energy Technology Data Exchange (ETDEWEB)

    Bulatov, V; Hsiung, L; Tang, M; Arsenlis, A; Bartelt, M; Cai, W; Florando, J; Hiratani, M; Rhee, M; Hommes, G; Pierce, T; Diaz de la Rubia, T

    2006-06-20

    At the microscopic scale, the strength of a crystal derives from the motion, multiplication and interaction of distinctive line defects--dislocations. First theorized in 1934 to explain low magnitudes of crystal strength observed experimentally, the existence of dislocations was confirmed only two decades later. Much of the research in dislocation physics has since focused on dislocation interactions and their role in strain hardening: a common phenomenon in which continued deformation increases a crystal's strength. The existing theory relates strain hardening to pair-wise dislocation reactions in which two intersecting dislocations form junctions tying dislocations together. Here we report that interactions among three dislocations result in the formation of unusual elements of dislocation network topology, termed hereafter multi-junctions. The existence of multi-junctions is first predicted by Dislocation Dynamics (DD) and atomistic simulations and then confirmed by the transmission electron microscopy (TEM) experiments in single crystal molybdenum. In large-scale Dislocation Dynamics simulations, multi-junctions present very strong, nearly indestructible, obstacles to dislocation motion and furnish new sources for dislocation multiplication thereby playing an essential role in the evolution of dislocation microstructure and strength of deforming crystals. Simulation analyses conclude that multi-junctions are responsible for the strong orientation dependence of strain hardening in BCC crystals.

  5. Experimental determination of field factors (\\Omega _{{{Q}_{\\text{clin}}},{{Q}_{\\text{msr}}}}^{{{f}_{\\text{clin}}},{{f}_{\\text{msr}}}} ) for small radiotherapy beams using the daisy chain correction method

    Science.gov (United States)

    Lárraga-Gutiérrez, José Manuel

    2015-08-01

    Recently, Alfonso et al proposed a new formalism for the dosimetry of small and non-standard fields. The proposed new formalism is strongly based on the calculation of detector-specific beam correction factors by Monte Carlo simulation methods, which accounts for the difference in the response of the detector between the small and the machine specific reference field. The correct calculation of the detector-specific beam correction factors demands an accurate knowledge of the linear accelerator, detector geometry and composition materials. The present work shows that the field factors in water may be determined experimentally using the daisy chain correction method down to a field size of 1 cm  ×  1 cm for a specific set of detectors. The detectors studied were: three mini-ionization chambers (PTW-31014, PTW-31006, IBA-CC01), three silicon-based diodes (PTW-60018, IBA-SFD and IBA-PFD) and one synthetic diamond detector (PTW-60019). Monte Carlo simulations and experimental measurements were performed for a 6 MV photon beam at 10 cm depth in water with a source-to-axis distance of 100 cm. The results show that the differences between the experimental and Monte Carlo calculated field factors are less than 0.5%—with the exception of the IBA-PFD—for field sizes between 1.5 cm  ×  1.5 cm and 5 cm  ×  5 cm. For the 1 cm  ×  1 cm field size, the differences are within 2%. By using the daisy chain correction method, it is possible to determine measured field factors in water. The results suggest that the daisy chain correction method is not suitable for measurements performed with the IBA-PFD detector. The latter is due to the presence of tungsten powder in the detector encapsulation material. The use of Monte Carlo calculated k{{Q\\text{clin}},{{Q}\\text{msr}}}{{f\\text{clin}},{{f}\\text{msr}}} is encouraged for field sizes less than or equal to 1 cm  ×  1 cm for the dosimeters used in this work.

  6. Multiple scattering correction to measurement of beam attenuation in bubble wakes%气泡尾流光束衰减测量中的复散射校正

    Institute of Scientific and Technical Information of China (English)

    鲁刚; 孙春生; 张晓晖

    2012-01-01

    为了分析复散射对气泡尾流衰减测量的影响,采用小角度辐射传输方程,引入了表征复散射效应强弱的校正因子,通过数值求解分析了典型的尾流气泡尺度分布和数密度条件下复散射校正因子与接收视场角、光学厚度、光束大小和接收截面大小等参量之间的关系.结果表明,接收视场角在前向小角度范围内的变化对复散射校正因子的影响很大,而视场角较大时对复散射校正因子的影响基本相同;光学厚度的变化对复散射校正因子的影响显著,且在光学厚度小于1时,影响更明显;接收截面大小的变化在光学厚度小于1时对复散射校正因子的影响很小,但在光学厚度较大时,对复散射校正因子的影响比较明显;光束大小的变化对复散射因子的影响相对较小,且在光束束腰较大时对复散射因子的影响基本不变.该研究为尾流光束衰减测量条件的选择和优化提供了理论依据.%For analyzing the influence of multiple scattering on measuring beam attenuation in bubble wakes, the correction coefficient was introduced which denotes the extent of multiple scattering, and its theoretical formulations was derived by means of a narrow angle approximation solution to the radiation transfer equation. Given a typical bubbles size distribution function and number density in bubbles wakes, the relation among the correction coefficient and detector Geld of view ( FOV), wake optical depth, beam size, received section size were analyzed by numerical calculation. Analysis shows that the influence of FOV in forward small angle on the correction coefficient is great, but it has a little change when the FOV is wide; and the impact of optical depth on the correction coefficient is prominent, besides the impact is more prominent when the optical depth is less than 1; and the effect of received section size on the correction coefficient is very little when depth is less lhan 1, but it

  7. Effect of Overaging on Solute Distributions and Bake Hardening Phenomenon in Bake Hardening Steels%Effect of Overaging on Solute Distributions and Bake Hardening Phenomenon in Bake Hardening Steels

    Institute of Scientific and Technical Information of China (English)

    WANG Hua; SHI Wen; HE Yan-lin; LU Xiao-gang; LI Lin

    2012-01-01

    Specimens of two different kinds of bake hardening steels (BH-Mn and BH-P) were prepared and treated with different annealing processes (water quenching and overaging). A novel technique of three dimensional atom probe was used to investigate solute distributions in these steels. The results indicate that C concentration decreases, whereas V increases during overaging in both bake hardening steels. The conclusion that no vanadium carbides pre- cipitate during the overaging is therefore originally obtained by microanalysis in bake hardening steels. Moreover, bake hardening values of all the specimens were tested by tensile experiments with 2 0/~ pre-deformation. However, those of overaged specimens were further measured with higher levels of pre-deformation because no bake hardening phenomenon was present at 2% pre-deformation. As the pre-deformation increases from 2% to 6% and 8%, both overaged steels show bake hardening values, and the value data are almost the same.

  8. Numerical model of phase transformation of steel C80U during hardening

    Directory of Open Access Journals (Sweden)

    T. Domański

    2007-12-01

    Full Text Available The article concerns numerical modelling of the phase transformations in solid state hardening of tool steel C80U. The transformations were assumed: initial structure – austenite, austenite – perlite, bainite and austenite – martensite. Model for evaluation of fractions of phases and their kinetics based on continuous heating diagram (CHT and continuous cooling diagram (CCT. The dilatometric tests on the simulator of thermal cycles were performed. The results of dilatometric tests were compared with the results of the test numerical simulations. In this way the derived models for evaluating phase content and kinetics of transformations in heating and cooling processes were verified. The results of numerical simulations confirm correctness of the algorithm that were worked out. In the numerical example the simulated estimation of the phase fraction in the hardened axisimmetrical element was performed.

  9. Configurable Radiation Hardened High Speed Isolated Interface ASIC Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NVE Corporation will design and build an innovative, low cost, flexible, configurable, radiation hardened, galvanically isolated, interface ASIC chip set that will...

  10. PERFORMANCE OF COATED CUTTING TOOLS IN MACHINING HARDENED STEEL

    Directory of Open Access Journals (Sweden)

    K.Subramanyam,

    2010-10-01

    Full Text Available This paper deals with the study of the performance of coated tools in machining hardening steel under dry conditions. This paper involves of machining AISI 4340 hardened steel using coated carbide tools is studied using full factorial experiments. Many parameters influence the quality of the products in hard turning process. The objective of this study is on the effect of the cutting conditions such as cutting velocity, feed, and depth of cut on the surface finish in machining AISI 4340 hardened steel. Machining of hardened steels has become an important manufacturing process, particularly in the automotive and bearing industries.

  11. Additive strengthening mechanisms in dispersion hardened polycrystals

    DEFF Research Database (Denmark)

    Hansen, Niels; Ralph, B.

    1986-01-01

    Tensile data from polycrystalline samples of copper dispersion strengthened by alumina are analysed. The basis of this analysis is to look at the strain range from 0.05 to 0.20 where the stress-strain curves show a parabolic hardening behaviour and are parallel to one another. The means by which...... the dislocation density contributions from each of these three sources. The type of additivity suggested here not only gives very good agreement with the stress-strain data but it also uses and is in accord with the experimental measurements of dislocation densities made using transmission electron microscopy....

  12. Adaptation of penelope Monte Carlo code system to the absorbed dose metrology: characterization of high energy photon beams and calculations of reference dosimeter correction factors; Adaptation du code Monte Carlo penelope pour la metrologie de la dose absorbee: caracterisation des faisceaux de photons X de haute energie et calcul de facteurs de correction de dosimetres de reference

    Energy Technology Data Exchange (ETDEWEB)

    Mazurier, J

    1999-05-28

    This thesis has been performed in the framework of national reference setting-up for absorbed dose in water and high energy photon beam provided with the SATURNE-43 medical accelerator of the BNM-LPRI (acronym for National Bureau of Metrology and Primary standard laboratory of ionising radiation). The aim of this work has been to develop and validate different user codes, based on PENELOPE Monte Carlo code system, to determine the photon beam characteristics and calculate the correction factors of reference dosimeters such as Fricke dosimeters and graphite calorimeter. In the first step, the developed user codes have permitted the influence study of different components constituting the irradiation head. Variance reduction techniques have been used to reduce the calculation time. The phase space has been calculated for 6, 12 and 25 MV at the output surface level of the accelerator head, then used for calculating energy spectra and dose distributions in the reference water phantom. Results obtained have been compared with experimental measurements. The second step has been devoted to develop an user code allowing calculation correction factors associated with both BNM-LPRI's graphite and Fricke dosimeters thanks to a correlated sampling method starting with energy spectra obtained in the first step. Then the calculated correction factors have been compared with experimental and calculated results obtained with the Monte Carlo EGS4 code system. The good agreement, between experimental and calculated results, leads to validate simulations performed with the PENELOPE code system. (author)

  13. Hounsfield unit recovery in clinical cone beam CT images of the thorax acquired for image guided radiation therapy

    Science.gov (United States)

    Slot Thing, Rune; Bernchou, Uffe; Mainegra-Hing, Ernesto; Hansen, Olfred; Brink, Carsten

    2016-08-01

    A comprehensive artefact correction method for clinical cone beam CT (CBCT) images acquired for image guided radiation therapy (IGRT) on a commercial system is presented. The method is demonstrated to reduce artefacts and recover CT-like Hounsfield units (HU) in reconstructed CBCT images of five lung cancer patients. Projection image based artefact corrections of image lag, detector scatter, body scatter and beam hardening are described and applied to CBCT images of five lung cancer patients. Image quality is evaluated through visual appearance of the reconstructed images, HU-correspondence with the planning CT images, and total volume HU error. Artefacts are reduced and CT-like HUs are recovered in the artefact corrected CBCT images. Visual inspection confirms that artefacts are indeed suppressed by the proposed method, and the HU root mean square difference between reconstructed CBCTs and the reference CT images are reduced by 31% when using the artefact corrections compared to the standard clinical CBCT reconstruction. A versatile artefact correction method for clinical CBCT images acquired for IGRT has been developed. HU values are recovered in the corrected CBCT images. The proposed method relies on post processing of clinical projection images, and does not require patient specific optimisation. It is thus a powerful tool for image quality improvement of large numbers of CBCT images.

  14. Hardened Client Platforms for Secure Internet Banking

    Science.gov (United States)

    Ronchi, C.; Zakhidov, S.

    We review the security of e-banking platforms with particular attention to the exploitable attack vectors of three main attack categories: Man-in-the-Middle, Man-in-the-PC and Man-in-the-Browser. It will be shown that the most serious threats come from combination attacks capable of hacking any transaction without the need to control the authentication process. Using this approach, the security of any authentication system can be bypassed, including those using SecureID Tokens, OTP Tokens, Biometric Sensors and Smart Cards. We will describe and compare two recently proposed e-banking platforms, the ZTIC and the USPD, both of which are based on the use of dedicated client devices, but with diverging approaches with respect to the need of hardening the Web client application. It will be shown that the use of a Hardened Browser (or H-Browser) component is critical to force attackers to employ complex and expensive techniques and to reduce the strength and variety of social engineering attacks down to physiological fraud levels.

  15. Hardness variability in commercial and hardened technologies

    Energy Technology Data Exchange (ETDEWEB)

    Shaneyfelt, M.R.; Winokur, P.S.; Meisenheimer, T.L.; Sexton, F.W.; Roeske, S.B.; Knoll, M.G.

    1994-03-01

    Over the past 10 years, there have been a number of advances in methods to assess and assure the radiation hardness of microelectronics in military and space applications. At the forefront of these is the Qualified Manufacturers List (QML) methodology, in which the hardness of product is ``built-in`` through statistical process control (SPC) of technology parameters relevant to the radiation response, test structure to integrated circuit (IC) correlations, and techniques for extrapolating laboratory test results to varying radiation scenarios. At the same time, there has been renewed interest in the use of commercial technology -- with its enhanced performance, reduced cost, and higher reliability -- in military and space systems. In this paper, we initially demonstrate the application of QML techniques to assure and control the radiation response of hardened technologies. Through several examples, we demonstrate intra-die, wafer-to-wafer, and lot-to-lot variations in a hardened technology. We observe 10 to 30% variations in key technology parameters that result from variability in geometry, process, and design layout. Radiation-induced degradation is seen to mirror preirradiation characteristics. We then evaluate commercial technologies and report considerably higher variability in radiation hardness, i.e., variations by a factor of two to five. This variability is shown to arise from a lack of control of technology parameters relevant to the radiation response, which a commercial manufacturer has no interest in controlling in a normal process flow.

  16. Beam Techniques - Beam Control and Manipulation

    Energy Technology Data Exchange (ETDEWEB)

    Minty, Michiko G

    2003-04-24

    We describe commonly used strategies for the control of charged particle beams and the manipulation of their properties. Emphasis is placed on relativistic beams in linear accelerators and storage rings. After a brief review of linear optics, we discuss basic and advanced beam control techniques, such as transverse and longitudinal lattice diagnostics, matching, orbit correction and steering, beam-based alignment, and linac emittance preservation. A variety of methods for the manipulation of particle beam properties are also presented, for instance, bunch length and energy compression, bunch rotation, changes to the damping partition number, and beam collimation. The different procedures are illustrated by examples from various accelerators. Special topics include injection and extraction methods, beam cooling, spin transport and polarization.

  17. The output factor correction as function of the photon beam field size - direct measurement and calculation from the lateral dose response functions of gas-filled and solid detectors.

    Science.gov (United States)

    Poppinga, Daniela; Delfs, Björn; Meyners, Jutta; Harder, Dietrich; Poppe, Björn; Looe, Hui Khee

    2017-08-28

    The first aim of this study has been to extend the systematic experimental study of the field size dependence of the output factor correction for three micro-ionization chambers (PTW 31014, PTW 31022 and IBA Razor chamber), two silicon diodes (PTW 60017 and IBA Razor Diode) and the synthetic diamond detector microDiamond (PTW 60019) in a 6 MV photon beam down to an effective field side length of 2.6mm, and to summarize the present knowledge of this factor by treating it as a function of the dosimetric field size. In order to vary the dosimetric field size over this large range, output factors measurements were performed at source-to-surface distances of 60cm and 90cm. Since the output factors obtained with the organic scintillation detector Exradin W1 (Standard Imaging, Middleton, USA) at all field sizes closely agreed with those measured by EBT3 radiochromic films (ISP Corp, Wayne, USA), the scintillation detector served as the reference detector. The measured output correction factors reflect the influences of the volume averaging and density effects upon the uncorrected output factor values. In case of the microDiamond detector these opposing influences result in output factor correction values less than 1 for moderately small field sizes and larger than 1 for very small field sizes. Our results agree with most of the published experimental as well as Monte-Carlo simulated data within detector-specific limits of uncertainty. The dosimetric field side length has been identified as a reliable determinant of the output factor correction, and typical functional curve shapes of the field-size dependent output factor correction vs. dosimetric field side length have been associated with gas-filled, silicon diode and synthetic diamond detectors. The second aim of this study has been a novel, semi-empirical approach to calculate the field-size dependent output correction factors of small photon detectors by convolving film measured true dose profile data with measured

  18. Application Progress of Cone Beam CT in Orthodontic Correction and Treatment of Skeletal ClassⅢ Malocclusion%锥形束CT在骨性Ⅲ类错牙合正畸治疗中的应用进展

    Institute of Scientific and Technical Information of China (English)

    王国杰; 刘春丽; 杨晓瑞

    2016-01-01

    随着正畸学的进步,正畸治疗过程中牙槽骨的改建效果越来越受到人们的重视,尤其对于骨性Ⅲ类错牙合患者,如何及时精确评估牙槽骨改建情况对矫正成功与否至关重要。锥形束CT(Cone Beam Computed Tomography,CBCT)的出现开创了口腔三维成像的新纪元。本文首先阐述了CBCT应用于口腔正畸的优势与不足,然后重点总结了锥形束CT在骨性Ⅲ类错牙合矫正方案设计、治疗过程中对牙槽骨量的监测及治疗效果评价的相关研究,对未来CBCT在该领域的发展进行了展望。%With the progress of orthodontic learning, the effect of alveolar bone reconstruction in the process of Orthodontic treatment gets more and more attention, especially for patients with skeletal ClassⅢmalocclusion. How to make timely and accurate assessment of alveolar bone reconstruction effect is crucial for correction. The emergence of the cone beam CT (CBCT) ushered in a new era of oral three-dimensional imaging. This paper focused on the advantages and disadvantages of application of CBCT in correction and treatment of skeletal ClassⅢmalocclusion. It also summarized the application of CBCT in skeletal Class III malocclusion scheme design, related researches on monitor and effect evaluation of alveolar bone mass in the process of correction, and made prospects of the future development of CBCT in this ifeld.

  19. [Hardening of dental tissue by CO2 laser radiation].

    Science.gov (United States)

    Aboites, V; Díaz, O; Cuevas, F

    1989-03-01

    A study was conducted to test the effects of CO2 laser irradiation on dental tissue. It was found that hardening of the dental tissue occurs. This was observed qualitatively by direct observation and by X-ray radiography. The hardening produced was also quantitatively measured using a hardness-meter on Rockwell scale.

  20. Design and characterization of cellulose nanocrystal-enhanced epoxy hardeners

    Science.gov (United States)

    Shane X. Peng; Robert J. Moon; Jeffrey P. Youngblood

    2014-01-01

    Cellulose nanocrystals (CNCs) are renewable, sustainable, and abundant nanomaterial widely used as reinforcing fillers in the field of polymer nanocomposites. In this study, two-part epoxy systems with CNC-enhanced hardeners were fabricated. Three types of hardeners, Jeffamine D400 (JD400), diethylenetriamine (DETA), and (±)-trans-1,2- diaminocyclohexane (DACH), were...

  1. ANISOTROPIC STRAIN-HARDENING IN POLYCRYSTALLINE COPPER AND ALUMINUM

    NARCIS (Netherlands)

    HESS, F

    1993-01-01

    A new viscoplastic model for the plastic stress-strain behaviour of f.c.c. metals is presented. In this model the strain hardening results from increasing dislocation densities. The observed stagnation of strain hardening after strain reversals is explained by a lowering of the increase in dislocati

  2. Modeling of state parameter and hardening function for granular materials

    Institute of Scientific and Technical Information of China (English)

    彭芳乐; 李建中

    2004-01-01

    A modified plastic strain energy as hardening state parameter for dense sand was proposed, based on the results from a series of drained plane strain tests on saturated dense Japanese Toyoura sand with precise stress and strain measurements along many stress paths. In addition, a unique hardening function between the plastic strain energy and the instantaneous stress path was also presented, which was independent of stress history. The proposed state parameter and hardening function was directly verified by the simple numerical integration method. It is shown that the proposed hardening function is independent of stress history and stress path and is appropriate to be used as the hardening rule in constitutive modeling for dense sand, and it is also capable of simulating the effects on the deformation characteristics of stress history and stress path for dense sand.

  3. A radiation-hardened SOI-based FPGA

    Institute of Scientific and Technical Information of China (English)

    Han Xiaowei; Gao Jiantou; Wang Jian; Li Ming; Liu Guizhai; Zhang Feng; Guo Xufeng; Stanley L.Chen; Liu Zhongli; Yu Fang; Zhao Kai; Wu Lihua; Zhao Yan; Li Yan; Zhang Qianli; Chen Liang; Zhang Guoquan; Li Jianzhong; Yang Bo

    2011-01-01

    A radiation-hardened SRAM-based field programmable gate array VS 1000 is designed and fabricated with a 0.5 μm partial-depletion silicon-on-insulator logic process at the CETC 58th Institute.The new logic cell (LC),with a multi-mode based on 3-input look-up-table (LUT),increases logic density about 12% compared to a traditional 4-input LUT.The logic block (LB),consisting of 2 LCs,can be used in two functional modes:LUT mode and distributed read access memory mode.The hierarchical routing channel block and switch block can significantly improve the flexibility and routability of the routing resource.The VS1000 uses a CQFP208 package and contains 392 reconfigurable LCs,112 reconfigurable user I/Os and IEEE 1149.1 compatible with boundaryscan logic for testing and programming.The function test results indicate that the hardware and software cooperate successfully and the VS 1000 works correctly.Moreover,the radiation test results indicate that the VS 1000 chip has total dose tolerance of 100 krad(Si),a dose rate survivability of 1.5 × 1011 rad(Si)/s and a neutron fluence immunity of 1 × 1014 n/cm2.

  4. A radiation-hardened SOI-based FPGA

    Science.gov (United States)

    Xiaowei, Han; Lihua, Wu; Yan, Zhao; Yan, Li; Qianli, Zhang; Liang, Chen; Guoquan, Zhang; Jianzhong, Li; Bo, Yang; Jiantou, Gao; Jian, Wang; Ming, Li; Guizhai, Liu; Feng, Zhang; Xufeng, Guo; Chen, Stanley L.; Zhongli, Liu; Fang, Yu; Kai, Zhao

    2011-07-01

    A radiation-hardened SRAM-based field programmable gate array VS1000 is designed and fabricated with a 0.5 μm partial-depletion silicon-on-insulator logic process at the CETC 58th Institute. The new logic cell (LC), with a multi-mode based on 3-input look-up-table (LUT), increases logic density about 12% compared to a traditional 4-input LUT The logic block (LB), consisting of 2 LCs, can be used in two functional modes: LUT mode and distributed read access memory mode. The hierarchical routing channel block and switch block can significantly improve the flexibility and routability of the routing resource. The VS1000 uses a CQFP208 package and contains 392 reconfigurable LCs, 112 reconfigurable user I/Os and IEEE 1149.1 compatible with boundary-scan logic for testing and programming. The function test results indicate that the hardware and software cooperate successfully and the VS1000 works correctly. Moreover, the radiation test results indicate that the VS1000 chip has total dose tolerance of 100 krad(Si), a dose rate survivability of 1.5 × 1011 rad(Si)/s and a neutron fluence immunity of 1 × 1014 n/cm2.

  5. Monte Carlo correction factors for a Farmer 0.6 cm{sup 3} ion chamber dose measurement in the build-up region of the 6 MV clinical beam

    Energy Technology Data Exchange (ETDEWEB)

    Pena, J [Departamento de Fisica de PartIculas, Universidade de Santiago de Compostela, Santiago de Compostela (Spain); Sanchez-Doblado, F [Hospital Universitario Virgen Macarena, RadioFisica, Sevilla (Spain); Departamento de FisiologIa y BioFisica, Facultad de Medicina, Universidad de Sevilla (Spain); Capote, R [International Atomic Energy Agency, Nuclear Data Section, Vienna (Austria); Terron, J A [Hospital Universitario Virgen Macarena, RadioFisica, Sevilla (Spain); Departamento de FisiologIa y BioFisica, Facultad de Medicina, Universidad de Sevilla (Spain); Gomez, F [Departamento de Fisica de PartIculas, Universidade de Santiago de Compostela, Santiago de Compostela (Spain)

    2006-03-21

    Reference dosimetry of photon fields is a well-established subject and currently available protocols (such as the IAEA TRS-398 and AAPM TG-51) provide methods for converting the ionization chamber (IC) reading into dose to water, provided reference conditions of charged particle equilibrium (CPE) are fulfilled. But these protocols cannot deal with the build-up region, where the lack of CPE limits the applicability of the cavity theorems and so the chamber correction factors become depth dependent. By explicitly including the IC geometry in the Monte Carlo simulations, depth-dependent dose correction factors are calculated for a PTW 30001 0.6 cm{sup 3} ion chamber in the build-up region of the 6 MV photon beam. The corrected percentage depth dose (PDD) agrees within 2% with that measured using the NACP 02 plane-parallel ion chamber in the build-up region at depths greater than 0.4 cm, where the Farmer chamber wall reaches the phantom surface.

  6. The influence of the heel effect in cone-beam computed tomography: artifacts in standard and novel geometries and their correction

    Science.gov (United States)

    Braun, H.; Kyriakou, Y.; Kachelrieß, M.; Kalender, W. A.

    2010-10-01

    For decades, the heel effect has been known to cause an angular dependence of the emitted spectrum of an x-ray tube. In radiography, artifacts were observed and attributed to the heel effect. However, no problems due to the heel effect were discerned in multi-slice computed tomography (MSCT) so far. With flat-detector CT (FDCT), involving larger cone angles and different system geometries, the heel effect might cause new artifacts. These artifacts were analyzed in this paper for system geometries different from the ones widely used nowadays. Simulations and measurements were performed. Simulations included symmetric as well as asymmetric detector layouts and different x-ray tube orientations with respect to the detector plane. The measurements were performed on a micro-CT system in an asymmetric detector layout. Furthermore, an analytical correction scheme is proposed to overcome heel effect artifacts. It was shown that the type of artifact greatly depends on the orientation of the x-ray tube and also on the type of detector alignment (i.e. symmetric or different types of asymmetric alignment). Certain combinations exhibited almost no significant artifact while others greatly influenced the quality of the reconstructed images. The proposed correction scheme showed good results that were further improved when also applying a scatter correction. When designing CT systems, care should be taken when placing the tube and the detector. Orientation of the x-ray tube like in most MSCT systems seems advisable in asymmetric detector layouts. However, a different type of tube orientation can be overcome with suitable correction schemes.

  7. New orbit correction method uniting global and local orbit corrections

    Science.gov (United States)

    Nakamura, N.; Takaki, H.; Sakai, H.; Satoh, M.; Harada, K.; Kamiya, Y.

    2006-01-01

    A new orbit correction method, called the eigenvector method with constraints (EVC), is proposed and formulated to unite global and local orbit corrections for ring accelerators, especially synchrotron radiation(SR) sources. The EVC can exactly correct the beam positions at arbitrarily selected ring positions such as light source points, simultaneously reducing closed orbit distortion (COD) around the whole ring. Computer simulations clearly demonstrate these features of the EVC for both cases of the Super-SOR light source and the Advanced Light Source (ALS) that have typical structures of high-brilliance SR sources. In addition, the effects of errors in beam position monitor (BPM) reading and steering magnet setting on the orbit correction are analytically expressed and also compared with the computer simulations. Simulation results show that the EVC is very effective and useful for orbit correction and beam position stabilization in SR sources.

  8. Precipitation hardening in 350 grade maraging steel

    Energy Technology Data Exchange (ETDEWEB)

    Viswanathan, U.K. (Bhabha Atomic Research Centre, Bombay, (India). Radiometallurgy Div.); Dey, G.K. (Bhabha Atomic Research Centre, Bombay, (India). Metallurgy Division); Asundi, M.K. (Government Colony, Bombay, (India))

    1993-11-01

    Evolution of microstructure in 350 grade commercial maraging steel has been examined. In the earlier stages of aging, the strengthening phases are formed by the heterogeneous precipitation, and these phases have been identified as intermetallic compounds of the Ni[sub 3] (Ti, Mo) and Fe[sub 2]Mo types. The kinetics of precipitation are studied in terms of the activation energy by carrying out isothermal hardness measurements of aged material. The mechanical properties in the peak-aged and overaged conditions were evaluated and the flow behavior examined. The overaging behavior of the steel has been studied and the formation of austenite of different morphologies identified. The crystallography of the austenite has been examined in detail. From the microstructural examination of peak-aged and deformed samples, it could be inferred that the dislocation-precipitate interaction is by precipitate shearing. Increased work hardening of the material in the overaged condition was suggestive of looping of precipitates by dislocations.

  9. Precipitation hardening in 350 grade maraging steel

    Science.gov (United States)

    Viswanathan, U. K.; Dey, G. K.; Asundi, M. K.

    1993-11-01

    Evolution of microstructure in a 350 grade commercial maraging steel has been examined. In the earlier stages of aging, the strengthening phases are formed by the heterogeneous precipitation, and these phases have been identified as intermetallic compounds of the Ni3 (Ti, Mo) and Fe2Mo types. The kinetics of precipitation are studied in terms of the activation energy by carrying out isothermal hardness measurements of aged material. The mechanical properties in the peak-aged and overaged conditions were evaluated and the flow behavior examined. The overaging behavior of the steel has been studied and the formation of austenite of different morphologies identified. The crystallography of the austenite has been examined in detail. From the microstructural examination of peak-aged and deformed samples, it could be inferred that the dislocation-precipitate interaction is by precipitate shearing. Increased work hardening of the material in the overaged condition was suggestive of looping of precipitates by dislocations.

  10. Jerky loads on surface-hardened gears

    Science.gov (United States)

    Rettig, H.; Wirth, X.

    1978-01-01

    Damage occurs again and again in practice in the form of transmissions with surface hardened gears which break after a very long operating time (explained by seldom occurring jerky loads). Gear drives are frequently exposed to jerky stresses which are greater than their fatigue limit. These stresses are considered in gear calculations, first, by shock factors when the transmission is to be designed as high endurance with regard to overloads and, second, in the form of operating ratios when the design is to be time enduring with regard to overloads. The size of the operating ratio depends not only on torque characteristics, drive and processing machine, but also on the material and heat treatment.

  11. Keystroke Dynamics-Based Credential Hardening Systems

    Science.gov (United States)

    Bartlow, Nick; Cukic, Bojan

    abstract Keystroke dynamics are becoming a well-known method for strengthening username- and password-based credential sets. The familiarity and ease of use of these traditional authentication schemes combined with the increased trustworthiness associated with biometrics makes them prime candidates for application in many web-based scenarios. Our keystroke dynamics system uses Breiman’s random forests algorithm to classify keystroke input sequences as genuine or imposter. The system is capable of operating at various points on a traditional ROC curve depending on application-specific security needs. As a username/password authentication scheme, our approach decreases the system penetration rate associated with compromised passwords up to 99.15%. Beyond presenting results demonstrating the credential hardening effect of our scheme, we look into the notion that a user’s familiarity to components of a credential set can non-trivially impact error rates.

  12. Dilatant hardening of fluid-saturated sandstone

    Science.gov (United States)

    Makhnenko, Roman Y.; Labuz, Joseph F.

    2015-02-01

    The presence of pore fluid in rock affects both the elastic and inelastic deformation processes, yet laboratory testing is typically performed on dry material even though in situ the rock is often saturated. Techniques were developed for testing fluid-saturated porous rock under the limiting conditions of drained, undrained, and unjacketed response. Confined compression experiments, both conventional triaxial and plane strain, were performed on water-saturated Berea sandstone to investigate poroelastic and inelastic behavior. Measured drained response was used to calibrate an elasto-plastic constitutive model that predicts undrained inelastic deformation. The experimental data show good agreement with the model: dilatant hardening in undrained triaxial and plane strain compression tests under constant mean stress was predicted and observed.

  13. Spectral Hardening and Geoeffectiveness of Solar Flares

    Science.gov (United States)

    Jain, R.; Kumar, S.; Dave, H.; Deshpande, M. R.

    We present the results of a few typical flares that observed by the first space borne solar astronomy experiment of India namely "Solar X-ray Spectrometer (SOXS)" mission, which has completed one year of its successful operation in geostationary orbit. The SOXS mission onboard GSAT-2 Indian spacecraft was launched successfully by GSLV-D2 rocket on 08 May 2003 to study the energy release and particle acceleration in solar flares. The SOXS is composed of two independent payloads viz. SOXS Low Energy Detector (SLD) payload, and SOXS High Energy Detector (SHD) payload. We restrict our presentation to SLD payload that designed, developed and fabricated by Physical Research Laboratory (PRL) in collaboration with Space Application Centre (SAC), Ahmedabad and ISRO Satellite Centre (ISAC), Bangalore of Indian Space Research Organization (ISRO). We briefly present the scientific objectives and instrumentation of the SLD payload. The SLD payload employs the state-of-art solid state detectors viz. Si PIN and CZT detectors, which reveal sub-keV spectral and 100ms temporal resolution characteristics that are necessary to study the spectral response of the flare components. The dynamic range of Si and CZT detectors is 4-25 and 4-56 keV respectively. The SLD has observed more than 140 flares of C and M class since its commissioning in the orbit. We present the X-ray emission characteristics of a few typical flares in view of their spectral hardening and geo-effectiveness. We extend our study of these flares to optical and radio waveband observations in order to improve the relationship of X-ray spectral hardening and geo-effectiveness. The flares with harder spectra and associated with small or large CME, and radio emission at frequencies above 10 GHz are found geo-effective.

  14. Histogram-driven cupping correction (HDCC) in CT

    Science.gov (United States)

    Kyriakou, Y.; Meyer, M.; Lapp, R.; Kalender, W. A.

    2010-04-01

    Typical cupping correction methods are pre-processing methods which require either pre-calibration measurements or simulations of standard objects to approximate and correct for beam hardening and scatter. Some of them require the knowledge of spectra, detector characteristics, etc. The aim of this work was to develop a practical histogram-driven cupping correction (HDCC) method to post-process the reconstructed images. We use a polynomial representation of the raw-data generated by forward projection of the reconstructed images; forward and backprojection are performed on graphics processing units (GPU). The coefficients of the polynomial are optimized using a simplex minimization of the joint entropy of the CT image and its gradient. The algorithm was evaluated using simulations and measurements of homogeneous and inhomogeneous phantoms. For the measurements a C-arm flat-detector CT (FD-CT) system with a 30×40 cm2 detector, a kilovoltage on board imager (radiation therapy simulator) and a micro-CT system were used. The algorithm reduced cupping artifacts both in simulations and measurements using a fourth-order polynomial and was in good agreement to the reference. The minimization algorithm required less than 70 iterations to adjust the coefficients only performing a linear combination of basis images, thus executing without time consuming operations. HDCC reduced cupping artifacts without the necessity of pre-calibration or other scan information enabling a retrospective improvement of CT image homogeneity. However, the method can work with other cupping correction algorithms or in a calibration manner, as well.

  15. Clinical recommendations regarding use of cone beam computed tomography in orthodontics. [corrected]. Position statement by the American Academy of Oral and Maxillofacial Radiology.

    Science.gov (United States)

    2013-08-01

    To summarize the potential benefits and risks of maxillofacial cone beam computed tomography (CBCT) use in orthodontic diagnosis, treatment and outcomes and to provide clinical guidance to dental practitioners. This statement was developed by consensus agreement of a panel convened by the American Academy of Oral and Maxillofacial Radiology (AAOMR). The literature on the clinical efficacy of and radiation dose concepts associated with CBCT in all aspects of orthodontic practice was reviewed. The panel concluded that the use of CBCT in orthodontic treatment should be justified on an individual basis, based on clinical presentation. This statement provides general recommendations, specific use selection recommendations, optimization protocols, and radiation-dose, risk-assessment strategies for CBCT imaging in orthodontic diagnosis, treatment and outcomes. The AAOMR supports the safe use of CBCT in dentistry. This position statement is periodically revised to reflect new evidence and, without reapproval, becomes invalid after 5 years. Copyright © 2013. Published by Mosby, Inc.

  16. Non Radiation Hardened Microprocessors in Spaced Based Remote Sensing Systems

    Science.gov (United States)

    Decoursey, Robert J.; Estes, Robert F.; Melton, Ryan

    2006-01-01

    (SEU) and Single Event Latch-up (SEL) rates. Although less significant, spacecraft flying in the area around the poles experience similar upsets. Finally, powerful solar proton events in the range of 10MeV/10pfu to 100MeV/1pfu as are forecasted and tracked by NOAA's Space Environment Center in Colorado can result in Single Event Upset (SEU), Single Event Latch-up (SEL) and permanent failures such as Single Event Gate Rupture (SEGR) in some technologies. (Galactic Cosmic Rays (GCRs) are another source, especially for gate rupture) CALIPSO mitigates common radiation concerns in its data handling through the use of redundant processors, radiation-hardened Application Specific Integrated Circuits (ASIC), hardware-based Error Detection and Correction (EDAC), processor and memory scrubbing, redundant boot code and mirrored files. After presenting a system overview this paper will expand on each of these strategies. Where applicable, related on-orbit data collected since the CALIPSO initial boot on May 4, 2006 will be noted.

  17. Porosity and mechanically optimized PLGA based in situ hardening systems.

    Science.gov (United States)

    Schloegl, W; Marschall, V; Witting, M Y; Volkmer, E; Drosse, I; Leicht, U; Schieker, M; Wiggenhorn, M; Schaubhut, F; Zahler, S; Friess, W

    2012-11-01

    Goal of the present study was to develop and to characterize in situ-hardening, porous PLGA-based systems for their future application as bone grafting materials. Therefore, we investigated the precipitation behavior of formulations containing PLGA and a water-miscible solvent, DMSO, PEG 400, and NMP. To increase porosity, a pore forming agent (NaCMC) was added and to enhance mechanical properties of the system, an inorganic filler (α-TCP) was incorporated. The behavior upon contact with water and the influence of the prior addition of aqueous media on the morphology of the corresponding hardened implants were investigated. We proved cell-compatibility by live/dead assays for the hardened porous polymer/ceramic-composite scaffolds. The IsHS formulations can therefore be used to manufacture hardened scaffolds ex vivo by using molds with the desired shape and size. Cells were further successfully incorporated into the IsHS by precultivating the cells on the α-TCP-powder prior to their admixing to the formulation. However, cell viability could not be maintained due to toxicity of the tested solvents. But, the results demonstrate that in vivo cells should well penetrate, adhere, and proliferate in the hardened scaffolds. Consequently, we consider the in situ hardening system being an excellent candidate as a filling material for non-weight-bearing orthopedic indications, as the resulting properties of the hardened implant fulfill indication-specific needs like mechanical stability, elasticity, and porosity.

  18. Tailored work hardening descriptions in simulation of sheet metal forming

    Science.gov (United States)

    Vegter, Henk; Mulder, Hans.; van Liempt, Peter; Heijne, Jan

    2013-12-01

    In the previous decades much attention has been given on an accurate material description, especially for simulations at the design stage of new models in the automotive industry. Improvements lead to shorter design times and a better tailored use of material. It also contributed to the design and optimization of new materials. The current description of plastic material behaviour in simulation models of sheet metal forming is covered by a hardening curve and a yield surface. In this paper the focus will be on modelling of work hardening for advanced high strength steels considering the requirements of present applications. Nowadays work hardening models need to include the effect of hard phases in a soft matrix and the effect of strain rate and temperature on work hardening. Most material tests to characterize work hardening are only applicable to low strains whereas many practical applications require hardening data at relatively high strains. Therefore, physically based hardening descriptions are needed allowing reliable extensions to high strain values.

  19. Surface modification on PMMA : PVDF polyblend: hardening under chemical environment

    Indian Academy of Sciences (India)

    R Bajpai; V Mishra; Pragyesh Agrawal; S C Datt

    2002-02-01

    The influence of chemical environment on polymers include the surface alteration as well as other deep modifications in surface layers. The surface hardening, as an effect of organic liquids on poly(methyl methacrylate): poly(vinylidene fluoride) (PMMA: PVDF), which is one of the few known miscible blends, has been detected using microhardness testing. Organic liquids like acetone, toluene, xylene and benzene were introduced on the surface of blend specimens for different durations. Vickers microhardness (v) was measured for treated and untreated specimens. The study reveals both hardening and plasticization of specimens at different exposure times. The degree of surface hardening is maximum under acetone treatment. All the specimens exhibit surface hardening at an exposure time of 1 h with all the four liquids. This feature is prominent with longer exposures for specimens with increasing content of PVDF. However, the degree of hardening decreases with the time of exposure in the respective environments. In general, acetone and toluene impart surface hardening, whereas, xylene and benzene soften the specimen. PMMA: PVDF (83 : 17) blend exhibits surface hardening under all the four treatments when compared with the respective untreated specimens.

  20. Transverse Beam Size Effects in Beam Position Monitors

    Science.gov (United States)

    Kurennoy, Sergey

    2001-04-01

    The fields produced by a long beam with a given transverse charge distribution in a homogeneous vacuum chamber are studied. Signals induced by the displaced finite-size beam on electrodes of a beam position monitor (BPM) are calculated and compared to those from a pencil beam. The corrections to BPM signals due to a finite beam size are found analytically for a few particular transverse distributions of the beam current. The results for fields can also be directly applied for calculating the beam coupling impedances of small discontinuities.

  1. THE CONSTITUTIVE EQUATIONS FOR MIXED HARDENING ORTHOTROPIC MATERIAL

    Institute of Scientific and Technical Information of China (English)

    LIUTeng-xi; HUANGShi-qing; FUYi-ming

    2003-01-01

    A dimensionless stress yield criterion is proposed to describe the mixed hardening of orthortropic material ,including kinematic hardening and proportional hardening,and the associated plastic flow law is derived.The generalized effective stress-strain formulae can be obtained correspondingly based on the experimental stress-strain curves in various simple stress states.The initial plastic anisotropy is influenced by the elastic anisotropy.The yield criterion can be reduced to Huber-Mises Criterion for isotropic materials and associated constitutive equations can be degenerated into Prandtl-Reuss equations.

  2. THE CONSTITUTIVE EQUATIONS FOR MIXED HARDENING ORTHOTROPIC MATERIAL

    Institute of Scientific and Technical Information of China (English)

    刘腾喜; 黄世清; 傅衣铭

    2003-01-01

    A dimensionless stress yield criterion is proposed to describe the mixed hardening of orthotropic material, including kinematic hardening and proportional hardening, and the associated plastic flow law is derived. The generalized effective stress-strain formulae can be obtained correspondingly based on the experimental stress-strain curves in various simple stress states. The initial plastic anisotropy is influenced by the elastic anisotropy. The yield criterion can be reduced to Huber-Mises Criterion for isotropic materials and associated constitutive equations can be degenerated into Prandtl-Reuss equations.

  3. Variations in the Bainite Hardenability of ASTM A723 Steel

    Science.gov (United States)

    1987-05-01

    8217, ,- -’ . . • • . . . . -. . " . ,~ .. -- --. x n~ I]AD TECHNICAL REPORT ARCCB-TR-87012 VARIATIONS IN THE BAINITE U) HARDENABILITY OF ASTM A723 STEEL 0’) 00 PAUL J. COTE LAWRENCE V...rod ,SuDfll|m) S. ?YPl[ Off REPOR.r & Pl[RIOO COVER•O VARIATIONS IN THE; BAINITE HARDENABILITY OF Final ASTH A723 STEEL I. Pl[RFORMINQ ORO. REPORT...0.1%) and copper (0.1%) in A723. A key transformation characteristic for this alloy is the bainite hardenability. It is important to know the extent to

  4. Image lag modeling and correction method for flat panel detector in cone-beam CT%锥束CT平板探测器成像的余晖建模与校正方法

    Institute of Scientific and Technical Information of China (English)

    黄魁东; 张定华; 李明君; 张华

    2013-01-01

    Cone-beam computed tomography (CT) has the notable features, viz high efficiency and high precision, and is widely used in the areas such as medical imaging and industrial non-destructive testing, but the presence of image lag reduces the quality of CT images. By referencing the multi-exponential decay model for the image lag and combining with the actual decay rule of the flat panel detector output signal, a new decay modeling and correction method for the image lag based on multi-exponential fitting is proposed. Firstly, an imaging experiment using cone-beam CT based on flat panel detector is carried out;the results show that the image lag decay of the pixels in the flat panel detector has a good consistency, and is irrelevant to the initial gray value. Then, the rapid image lag correction is achieved according to the image lag decay model, and the comparison of image quality of the projected images and slice images before and after image lag correction indicates that the edge sharpness of the part has been significantly improved after the lag correction. This method does not need to obtain the scintillation compositions and the decay time constants of the detector, and is easily applied to the practical cone-beam CT imaging systems for image lag detection and correction.%锥束CT具有高效率和高精度的显著特点,在医学成像与工业无损检测等领域已得到广泛应用,但余晖的存在降低了CT图像的质量。本文借鉴余晖多指数衰减模型的思想,结合平板探测器输出信号的实际衰减规律,提出了一种新的基于多指数拟合的余晖衰减建模及校正方法。首先进行了基于平板探测器的锥束CT成像实验,结果表明平板探测器各像素的余晖衰减规律具有良好的一致性,且余晖衰减规律与初始灰度的大小无关;其后根据建立的余晖衰减模型实现了余晖的快速校正,并分析比较了余晖校正前后投影图像和切片图像质量,

  5. Optical cone beam tomography of Cherenkov-mediated signals for fast 3D dosimetry of x-ray photon beams in water

    Energy Technology Data Exchange (ETDEWEB)

    Glaser, Adam K., E-mail: Adam.K.Glaser@dartmouth.edu, E-mail: Brian.W.Pogue@dartmouth.edu; Andreozzi, Jacqueline M. [Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755 (United States); Zhang, Rongxiao [Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755 (United States); Pogue, Brian W., E-mail: Adam.K.Glaser@dartmouth.edu, E-mail: Brian.W.Pogue@dartmouth.edu [Thayer School of Engineering and Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755 (United States); Gladstone, David J. [Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03766 (United States)

    2015-07-15

    Purpose: To test the use of a three-dimensional (3D) optical cone beam computed tomography reconstruction algorithm, for estimation of the imparted 3D dose distribution from megavoltage photon beams in a water tank for quality assurance, by imaging the induced Cherenkov-excited fluorescence (CEF). Methods: An intensified charge-coupled device coupled to a standard nontelecentric camera lens was used to tomographically acquire two-dimensional (2D) projection images of CEF from a complex multileaf collimator (MLC) shaped 6 MV linear accelerator x-ray photon beam operating at a dose rate of 600 MU/min. The resulting projections were used to reconstruct the 3D CEF light distribution, a potential surrogate of imparted dose, using a Feldkamp–Davis–Kress cone beam back reconstruction algorithm. Finally, the reconstructed light distributions were compared to the expected dose values from one-dimensional diode scans, 2D film measurements, and the 3D distribution generated from the clinical Varian ECLIPSE treatment planning system using a gamma index analysis. A Monte Carlo derived correction was applied to the Cherenkov reconstructions to account for beam hardening artifacts. Results: 3D light volumes were successfully reconstructed over a 400 × 400 × 350 mm{sup 3} volume at a resolution of 1 mm. The Cherenkov reconstructions showed agreement with all comparative methods and were also able to recover both inter- and intra-MLC leaf leakage. Based upon a 3%/3 mm criterion, the experimental Cherenkov light measurements showed an 83%–99% pass fraction depending on the chosen threshold dose. Conclusions: The results from this study demonstrate the use of optical cone beam computed tomography using CEF for the profiling of the imparted dose distribution from large area megavoltage photon beams in water.

  6. Space Qualified, Radiation Hardened, Dense Monolithic Flash Memory Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Space Micro proposes to build a radiation hardened by design (RHBD) flash memory, using a modified version of our RH-eDRAM Memory Controller to solve all the single...

  7. Properties of sodium silicate bonded sand hardened by microwave heating

    Institute of Scientific and Technical Information of China (English)

    Wang Jina; Fan Zitian; Zan Xiaolei; Pan Di

    2009-01-01

    The sodium silicate bonded sand hardened by microwave heating has many advantages,such as low sodium silicate adding quantity,fast hardening speed,high room temperature strength,good collapsibility and certain surface stability. However,it has big moisture absorbability in the air,which would lead to the compression strength and the surface stability of the sand molds being sharply reduced. In this study,the moisture absorbability of the sodium silicate bonded sand hardened by microwave heating in different humidity conditions and the effect factors were investigated. Meanwhile,the reasons for the big moisture absorbability of the sand were analyzed.Some measures to overcome the problems of high moisture absorbability,bad surface stability and sharply reducing strength in the air were discussed. The results of this study establish the foundation of green and clean foundry technology based on the microwave heating hardening sodium silicate sand process.

  8. Space Qualified, Radiation Hardened, Dense Monolithic Flash Memory Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Radiation hardened nonvolatile memories for space is still primarily confined to EEPROM. There is high density effective or cost effective NVM solution available to...

  9. Tensile Strain Hardening Behavior and Fractography of Superalloy GH39

    Directory of Open Access Journals (Sweden)

    WANG Hui

    2016-10-01

    Full Text Available The strain hardening behaviour and fractography of superalloy GH39 was investigated by tensile test at different strain rates. Results indicate that strain hardening behaviours are different during the deformation process. True stress-strain curve obeys the Hollomon relationship partly. The strain hardening exponentn in this stage is constant in the initial plastic stage. However, the value of n increased with true strain ε increasing when true strain is between 0.014 and 0.13. A lot of deformation twinning can be found, the twins and dislocations worked together to increase the value of n. The strain hardening exponent is increased lightly with the strain rate increasing, SEM observations show that in the case of low strain rate, the fracture mode is typical ductile, but there is a tendency from ductile to brittle fracture with increasing the strain rate.

  10. Radiation Hardened Ethernet PHY and Switch Fabric Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Innoflight will develop a new family of radiation hardened (up to 3 Mrad(Si)), fault-tolerant, high data-rate (up to 8 Gbps), low power Gigabit Ethernet PHY and...

  11. Technologies Enabling Custom Radiation-Hardened Component Development Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Two primary paths are available for the creation of a Rad-Hard ASIC. The first approach is to use a radiation hardened process such as existing Rad-Hard foundries....

  12. Novel SEU hardened PD SOI SRAM cell

    Institute of Scientific and Technical Information of China (English)

    Xie Chengmin; Wang Zhongfang; Wang Xihu; Wu Longsheng; Liu Youbao

    2011-01-01

    A novel SEU hardened 10T PD SOI SRAM cell is proposed.By dividing each pull-up and pull-down transistor in the cross-coupled inverters into two cascaded transistors,this cell suppresses the parasitic BJT and source-drain penetration charge collection effect in PD SOl transistor which causes the SEU in PD SOI SRAM.Mixed-mode simulation shows that this novel cell completely solves the SEU,where the ion affects the single transistor.Through analysis of the upset mechanism of this novel cell,SEU performance is roughly equal to the multiple-cell upset performance of a normal 6T SOI SRAM and it is thought that the SEU performance is 17 times greater than traditional 6T SRAM in 45nm PD SOI technology node based on the tested data of the references.To achieve this,the new cell adds four transistors and has a 43.4% area overhead and performance penalty.

  13. Durability of High Performance Color Hardener

    Institute of Scientific and Technical Information of China (English)

    MA Bao-guo; DONG Rong-zhen; ZHU Hong-bo; ZHANG Li; JIAN Shou-wei

    2004-01-01

    The properties of high performance color hardener (HPCH) and the mechanism were studied.HPCH is a composite system, which is composed of cementitious and auxiliary cementing materials, composite additives, abrasion resistance component (aggregate) and pigment. The porosity and pore structure of the material are obviously improved due to the activation, filling and adsorption of auxiliary cementing materials, thus resulting in a great increase of binding capacity for ions in HPCH and the obstacles of ion migrating.The density of material structure, bonding capacity of cementitious material to the abrasion-resisting component and the corrosion resistance are greatly and effectively improved by adding the auxiliary cementing materials and compound additives. According to the tests of dry shrinkage, sulphate resistance, chloride permeability and Ca(OH)2 content distribution, the property superiority of HPCH is analyzed.The mechanism of materials modification of HPCH is explained from the microscopic point of view by testing the pore structure and pore distribution via the mercury intrusion pressure method.

  14. Open Source Radiation Hardened by Design Technology

    Science.gov (United States)

    Shuler, Robert

    2016-01-01

    The proposed technology allows use of the latest microcircuit technology with lowest power and fastest speed, with minimal delay and engineering costs, through new Radiation Hardened by Design (RHBD) techniques that do not require extensive process characterization, technique evaluation and re-design at each Moore's Law generation. The separation of critical node groups is explicitly parameterized so it can be increased as microcircuit technologies shrink. The technology will be open access to radiation tolerant circuit vendors. INNOVATION: This technology would enhance computation intensive applications such as autonomy, robotics, advanced sensor and tracking processes, as well as low power applications such as wireless sensor networks. OUTCOME / RESULTS: 1) Simulation analysis indicates feasibility. 2)Compact voting latch 65 nanometer test chip designed and submitted for fabrication -7/2016. INFUSION FOR SPACE / EARTH: This technology may be used in any digital integrated circuit in which a high level of resistance to Single Event Upsets is desired, and has the greatest benefit outside low earth orbit where cosmic rays are numerous.

  15. Cylindrical shell buckling through strain hardening

    Energy Technology Data Exchange (ETDEWEB)

    Bandyopadhyay, K.; Xu, J.; Shteyngart, S. [Brookhaven National Lab., Upton, NY (United States); Gupta, D. [USDOE, Germantown, MD (United States)

    1995-04-01

    Recently, the authors published results of plastic buckling analysis of cylindrical shells. Ideal elastic-plastic material behavior was used for the analysis. Subsequently, the buckling analysis program was continued with the realistic stress-strain relationship of a stainless steel alloy which does not exhibit a clear yield point. The plastic buckling analysis was carried out through the initial stages of strain hardening for various internal pressure values. The computer program BOSOR5 was used for this purpose. Results were compared with those obtained from the idealized elastic-plastic relationship using the offset stress level at 0.2% strain as the yield stress. For moderate hoop stress values, the realistic stress-grain case shows a slight reduction of the buckling strength. But, a substantial gain in the buckling strength is observed as the hoop stress approaches the yield strength. Most importantly, the shell retains a residual strength to carry a small amount of axial compressive load even when the hoop stress has exceeded the offset yield strength.

  16. Hardening in Two-Phase Materials. II. Plastic Strain and Mean Stress Hardening Rate

    DEFF Research Database (Denmark)

    Lilholt, Hans

    1977-01-01

    The strain parameters which are relevant in a tensile experiment, are analysed and related to the geometry of deformation and to the mean stress of two-phase materials. The hardening rate of the mean stress with respect to plastic strain is found to be useful in comparison between experiments and...... and theories, and it allows theories to be probed over a range of strains. Previous experiments on the fibre-reinforced material of copper-tungsten are analysed in relation to the geometry of deformation....

  17. Strain Hardening of Polymer Glasses: Entanglements, Energetics, and Plasticity

    OpenAIRE

    Hoy, Robert S.; Robbins, Mark O.

    2007-01-01

    Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While stress-strain curves for a wide range of temperature can be fit to the functional form predicted by entropic network models, many other results are fundamentally inconsistent with the physical picture underlying these models. Stresses are too large to be entropic and have the wrong trend with temperature. The most dramatic hardening at large strains reflects increases in energy as chains are ...

  18. Study of the mechanisms involved in the laser superficial hardening process of metallic alloys; Estudo dos mecanismos envolvidos no processo de endurecimento superficial a laser de ligas metalicas

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Edmara Marques Rodrigues da

    2001-07-01

    The laser superficial hardening process of a ferrous alloy (gray cast iron) and of an aluminum-silicon alloy was investigated in this work. These metallic alloys are used in the automobile industry for manufacturing cylinders and pistons, respectively. By application of individual pulses and single tracks, the involved mechanisms during the processing were studied. Variables such as energy density, power density, temporal width, beam diameter on the sample surface, atmosphere of the processing region, overlapping and scanning velocity. The hardened surface was characterized by optical and scanning electronic microscopy, dispersive energy microanalysis, X-ray mapping, X-ray diffraction, and measurements of roughness and Vickers microhardness. Depending on the processing parameters, it is possible to obtain different microstructures. The affected area of gray cast iron, can be hardened by remelting or transformation hardening (total or partial) if the reached temperature is higher or not that of melting temperature. Laser treatment originated new structures such as retained austenite, martensite and, occasionally, eutectic of cellular dendritic structure. Aluminum-silicon alloy does not have phase transformation in solid state, it can be hardened only by remelting. The increase of hardness is a function of the precipitation hardening process, which makes the silicon particles smaller and more disperse in the matrix. Maximal values of microhardness (700-1000 HV) were reached with the laser treatment in gray cast iron samples. The initial microhardness is of 242 HV. For aluminum-silicon alloy, the laser remelting increases the initial microhardness of 128 HV to the range of 160-320 HV. The found results give a new perspective for using the CLA/IPEN's laser in the heat treatment area. Besides providing a higher absorptivity to the materials, compared with the CO{sub 2} laser, and optical fiber access, the superficial hardening with Nd:YAG laser, depending on the

  19. Effects of Transverse Beam Size in Beam Position Monitors

    CERN Document Server

    Kurennoy, S S

    2001-01-01

    The fields produced by a long beam with a given transverse charge distribution in a homogeneous vacuum chamber are studied. Signals induced by a displaced finite-size beam on electrodes of a beam position monitor (BPM) are calculated and compared to those produced by a pencil beam. The non-linearities and corrections to BPM signals due to a finite transverse beam size are calculated for an arbitrary chamber cross section. Simple analytical expressions are given for a few particular transverse distributions of the beam current in a circular or rectangular chamber. Of particular interest is a general proof that in an arbitrary homogeneous chamber the beam-size corrections vanish for any axisymmetric beam current distribution.

  20. Effects of transverse beam size in beam position monitors.

    Energy Technology Data Exchange (ETDEWEB)

    Kurennoy, S. (Sergey)

    2001-01-01

    The fields produced by a long beam with a given transverse charge distribution in a homogeneous vacuum chamber are studied. Signals induced by the displaced finite-size beam on electrodes of a beam position monitor (BPM) are calculated and compared to those from a pencil beam. The non-linearities and corrections to BPM signals due to a finite transverse beam size are calculated for an arbitrary chamber cross section. Simple analytical expressions are given for a few particular transverse distributions of the beam current in a circular or rectangular chamber. Of particular interest is a general proof that in an arbitrary homogeneous chamber the beam-size corrections vanish for any axisymmetric beam current distribution.

  1. EFFECTS OF TRANSFERSE BEAM SIZE IN BEAM POSITIONS MONITORS

    Energy Technology Data Exchange (ETDEWEB)

    S.S. KURENNOY

    2001-06-01

    The fields produced by a long beam with a given transverse charge distribution in a homogeneous vacuum chamber are studied. Signals induced by the displaced finite-size beam on electrodes of a beam position monitor (BPM) are calculated and compared to those from a pencil beam. The non-linearities and corrections to BPM signals due to a finite transverse beam size are calculated for an arbitrary chamber cross section. Simple analytical expressions are given for a few particular transverse distributions of the beam current in a circular or rectangular chamber. Of particular interest is a general proof that in an arbitrary homogeneous chamber the beam-size corrections vanish for any axisymmetric beam current distribution.

  2. Correction of Geometric Artifacts for Fan-Beam CT%扇束CT几何伪影的校正方法

    Institute of Scientific and Technical Information of China (English)

    王亮; 张朋

    2011-01-01

    实际工业CT系统很难满足经典CT图像重建公式所要求的射线源焦点、转台中心及线阵探测器之间严格的对准关系.不满足对准关系将导致经典CT图像重建公式所重建的图像中出现几何伪影.本文引入可以描述一般情况下CT扫描几何关系的一组几何参数,给出了由金属丝的投影数据间接估计这些几何参数的方法,还给出了基于这些几何参数的图像重建公式.本文只假设转台的旋转轴垂直于由射线源焦点与线阵探测器所形成的扇束,而不要求扫描系统满足其它几何对准关系.对于扫描系统不对准的情况,先按照本文方法估计几何参数,再将其代入本文提出的图像重建公式,便可以正确重建出被测物的断层CT图像.%For a real industrial CF system, it is very difficult to meet the rigorous aligned relations among the X-ray focus, the rotation cener of turntable and the linear detector, which is required by the conventional image reconstruction formula. Misalignment will result in geometric artifacts in the image reconstructed by the conventional image reconstruction formula. In this paper, we first introduce a set of geometric parameters which fully describe general CT scanning configuration, and then propose an indinect method to estirmate the set of parameters from the projection date of a meta sikl.We also propose a generalizad filtered back-projec-tion (FBP) reconstruction formula based on such set of parameters. In this paper, we assume that the rotation axis of the CT turntable is vertical to the fan-beam forned by the X-ray focus and the linear detector array,but do not require that the CT scanning system satisfies other alignment relations. For a misaligned scanning system, we can first estimate the pararneters by our method,and then reconstruct the image conrectly using our reconstmction formula with the estimated parameters.

  3. Geometric correction methods for Timepix based large area detectors

    Science.gov (United States)

    Zemlicka, J.; Dudak, J.; Karch, J.; Krejci, F.

    2017-01-01

    X-ray micro radiography with the hybrid pixel detectors provides versatile tool for the object inspection in various fields of science. It has proven itself especially suitable for the samples with low intrinsic attenuation contrast (e.g. soft tissue in biology, plastics in material sciences, thin paint layers in cultural heritage, etc.). The limited size of single Medipix type detector (1.96 cm2) was recently overcome by the construction of large area detectors WidePIX assembled of Timepix chips equipped with edgeless silicon sensors. The largest already built device consists of 100 chips and provides fully sensitive area of 14.3 × 14.3 cm2 without any physical gaps between sensors. The pixel resolution of this device is 2560 × 2560 pixels (6.5 Mpix). The unique modular detector layout requires special processing of acquired data to avoid occurring image distortions. It is necessary to use several geometric compensations after standard corrections methods typical for this type of pixel detectors (i.e. flat-field, beam hardening correction). The proposed geometric compensations cover both concept features and particular detector assembly misalignment of individual chip rows of large area detectors based on Timepix assemblies. The former deals with larger border pixels in individual edgeless sensors and their behaviour while the latter grapple with shifts, tilts and steps between detector rows. The real position of all pixels is defined in Cartesian coordinate system and together with non-binary reliability mask it is used for the final image interpolation. The results of geometric corrections for test wire phantoms and paleo botanic material are presented in this article.

  4. The accident of overexposure at the University hospital center of Toulouse. Expertise report n.1. Checking of experimental protocols of micro-beams calibration before and after dysfunction correction; L'accident de surexposition au centre hospitalier universitaire de Toulouse. Rapport d'expertise n.1. Verification des protocoles experimentaux d'etalonnage des microfaisceaux avant et apres correction du dysfonctionnement

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2007-07-01

    The regional center of stereotaxic radiosurgery of the University hospital center of Toulouse is equipped since april 2006 of a Novalis accelerator (Brainlab) devoted to the intra-skull stereotaxic radiosurgery. In april 2007, during an intercomparison of dosimetry computer files coming from different sites, the Brainlab society finds an anomaly in the files. The analysis made by the society concludes to to the use of an inappropriate detector for the measurement of a dosimetry parameter during the initial calibration of the accelerator. following this error, 145 patients (on the 172 treated by the service in question) suffer the consequences of an overdose whom importance is variable according the cases. The I.R.S.N. in charge of an expertise about the protocols of calibration of micro-beams before and after the correction of the dysfunction, took up with the search of the technical causes of the dysfunction. This report presents successively: the documents base on which is founded the expertise; the material of dosimetry and quality control necessary to the initial calibration of the device and to its follow-up; the formula made at the accelerator commissioning; the calibration of micro-beams in the two configurations that allows the device (micro-multi-knives and conic collimator) and the definition of parameters of the software of treatment planning; the maintenance and quality control implemented in the frame of its clinical use. (N.C.)

  5. High-Performance, Radiation-Hardened Electronics for Space Environments

    Science.gov (United States)

    Keys, Andrew S.; Watson, Michael D.; Frazier, Donald O.; Adams, James H.; Johnson, Michael A.; Kolawa, Elizabeth A.

    2007-01-01

    The Radiation Hardened Electronics for Space Environments (RHESE) project endeavors to advance the current state-of-the-art in high-performance, radiation-hardened electronics and processors, ensuring successful performance of space systems required to operate within extreme radiation and temperature environments. Because RHESE is a project within the Exploration Technology Development Program (ETDP), RHESE's primary customers will be the human and robotic missions being developed by NASA's Exploration Systems Mission Directorate (ESMD) in partial fulfillment of the Vision for Space Exploration. Benefits are also anticipated for NASA's science missions to planetary and deep-space destinations. As a technology development effort, RHESE provides a broad-scoped, full spectrum of approaches to environmentally harden space electronics, including new materials, advanced design processes, reconfigurable hardware techniques, and software modeling of the radiation environment. The RHESE sub-project tasks are: SelfReconfigurable Electronics for Extreme Environments, Radiation Effects Predictive Modeling, Radiation Hardened Memory, Single Event Effects (SEE) Immune Reconfigurable Field Programmable Gate Array (FPGA) (SIRF), Radiation Hardening by Software, Radiation Hardened High Performance Processors (HPP), Reconfigurable Computing, Low Temperature Tolerant MEMS by Design, and Silicon-Germanium (SiGe) Integrated Electronics for Extreme Environments. These nine sub-project tasks are managed by technical leads as located across five different NASA field centers, including Ames Research Center, Goddard Space Flight Center, the Jet Propulsion Laboratory, Langley Research Center, and Marshall Space Flight Center. The overall RHESE integrated project management responsibility resides with NASA's Marshall Space Flight Center (MSFC). Initial technology development emphasis within RHESE focuses on the hardening of Field Programmable Gate Arrays (FPGA)s and Field Programmable Analog

  6. Towards the clinical implementation of iterative low-dose cone-beam CT reconstruction in image-guided radiation therapy: Cone/ring artifact correction and multiple GPU implementation

    Science.gov (United States)

    Yan, Hao; Wang, Xiaoyu; Shi, Feng; Bai, Ti; Folkerts, Michael; Cervino, Laura; Jiang, Steve B.; Jia, Xun

    2014-01-01

    Purpose: Compressed sensing (CS)-based iterative reconstruction (IR) techniques are able to reconstruct cone-beam CT (CBCT) images from undersampled noisy data, allowing for imaging dose reduction. However, there are a few practical concerns preventing the clinical implementation of these techniques. On the image quality side, data truncation along the superior–inferior direction under the cone-beam geometry produces severe cone artifacts in the reconstructed images. Ring artifacts are also seen in the half-fan scan mode. On the reconstruction efficiency side, the long computation time hinders clinical use in image-guided radiation therapy (IGRT). Methods: Image quality improvement methods are proposed to mitigate the cone and ring image artifacts in IR. The basic idea is to use weighting factors in the IR data fidelity term to improve projection data consistency with the reconstructed volume. In order to improve the computational efficiency, a multiple graphics processing units (GPUs)-based CS-IR system was developed. The parallelization scheme, detailed analyses of computation time at each step, their relationship with image resolution, and the acceleration factors were studied. The whole system was evaluated in various phantom and patient cases. Results: Ring artifacts can be mitigated by properly designing a weighting factor as a function of the spatial location on the detector. As for the cone artifact, without applying a correction method, it contaminated 13 out of 80 slices in a head-neck case (full-fan). Contamination was even more severe in a pelvis case under half-fan mode, where 36 out of 80 slices were affected, leading to poorer soft tissue delineation and reduced superior–inferior coverage. The proposed method effectively corrects those contaminated slices with mean intensity differences compared to FDK results decreasing from ∼497 and ∼293 HU to ∼39 and ∼27 HU for the full-fan and half-fan cases, respectively. In terms of efficiency boost

  7. Limits of Ultra-Low Dose CT Attenuation Correction for PET/CT.

    Science.gov (United States)

    Xia, Ting; Alessio, Adam M; Kinahan, Paul E

    2010-01-29

    We present an analysis of the effects of ultra-low dose X-ray computerized tomography (CT) based attenuation correction for positron emission tomography (PET). By ultra low dose we mean less than approximately 5 mAs or 0.5 mSv total effective whole body dose. The motivation is the increased interest in using respiratory motion information acquired during the CT scan for both phase-matched CT-based attenuation correction and for motion estimation. Since longer duration CT scans are desired, radiation dose to the patient can be a limiting factor. In this study we evaluate the impact of reducing photon flux rates in the CT data on the reconstructed PET image by using the CATSIM simulation tool for the CT component and the ASIM simulation tool for the PET component. The CT simulation includes effects of the x-ray tube spectra, beam conditioning, bowtie filter, detector noise, and bean hardening correction. The PET simulation includes the effect of attenuation and photon counting. Noise and bias in the PET image were evaluated from multiple realizations of test objects. We show that techniques can be used to significantly reduce the mAs needed for CT based attenuation correction if the CT is not used for diagnostic purposes. The limiting factor, however, is not the noise in the CT image but rather the bias introduced by CT sinogram elements with no detected flux. These results constrain the methods that can be used to lower CT dose in a manner suitable for attenuation correction of PET data. We conclude that ultra-low-dose CT for attenuation correction of PET data is feasible with current PET/CT scanners.

  8. APPLICATION OF SYNCHRONOUS JACK-UP SYSTEM IN CORRECTION AND BEARING-REPLACEMENT OF CURVED BEAM%液压同步顶升系统在弯梁纠偏及支座更换中的应用

    Institute of Scientific and Technical Information of China (English)

    戴岩; 周天华

    2015-01-01

    The curved beam bridge is widely used in modern city viaduct.Because the complexity of its space stress mechanism, diseases are often found in curved beam bridge which could harm structural safety and serviceability.For this reason, such sort of bridge should be repaired.In this paper, some repair schemes were compared via finite element analysis based on a real bridge project.It is decided that synchronous jack-up system should be used for this project.This system has many advantages, especially when it is used in curved beam bridge.It was discussed the feasibility of using the system for repairing curved bridge project, based on the analysis of synchronous jack-up system’ s construction process, construction system, correction and bearing-replacement operation process.Through the analysis of monitoring data, the usability of this system was demonstrated in this kind of engineering project.In the end, some recommendations were put forward for popularizing.%弯梁桥在城市高架建设中被广泛应用,但由于其空间受力复杂,导致桥梁出现病害,影响其安全性与适用性,需对既有病害进行修复。选定某一工程实例,通过有限元分析对弯梁的维修方案进行比选,明确采用液压同步顶升系统进行维修施工,并进一步归纳该系统的优势。在详细分析液压同步顶升系统的施工流程、施工系统、纠偏与支座更换操作流程的基础上,通过分析监控数据,论证了此系统应用于弯梁纠偏及支座更换的可行性。

  9. Characteristics of high wear resistant Ni-base materials strengthened by precipitation hardening of wolfram silicide

    Energy Technology Data Exchange (ETDEWEB)

    Kiuchi, Kiyoshi; Ide, Hisayuki; Ishiyama, Takashi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-12-31

    The practical application of Co-base Stellite and Ni base Inconel for reactor core components with high allowable stress levels is considered to be limited by the formation of radioactive cruds and the susceptibility to IASCC respectively. For this view-point, W-silicide strengthened Cr-W-Si Ni-base high wear resistant alloy so-called HWI alloy was newly developed as an alternative material. The chemical composition and the alloy making process were optimized by applying the electron beam purification process and the thermo-mechanical treatment. The mechanical strength higher than it of above commercial alloys was easily obtained by both solid solution hardening and precipitation hardening, because this alloy has the excellent cold and hot workabilities. The irradiation resistance and the corrosion resistance superior than these of above commercial alloys were verified by several laboratory tests of HWI heats. To maintain austenite phase stability at the practical temperature and to enrich oxide former alloying elements were clarified to be the most important means for this alloy development. (author)

  10. Acoustic emission for characterising the crack propagation in strain-hardening cement-based composites (SHCC)

    Energy Technology Data Exchange (ETDEWEB)

    Paul, S.C. [Department of Civil Engineering, Stellenbosch University (South Africa); Pirskawetz, S. [BAM Federal Institute for Materials Research and Testing (Germany); Zijl, G.P.A.G. van, E-mail: gvanzijl@sun.ac.za [Department of Civil Engineering, Stellenbosch University (South Africa); Schmidt, W. [BAM Federal Institute for Materials Research and Testing (Germany)

    2015-03-15

    This paper presents the analysis of crack propagation in strain-hardening cement-based composite (SHCC) under tensile and flexural load by using acoustic emission (AE). AE is a non-destructive technique to monitor the development of structural damage due to external forces. The main objective of this research was to characterise the cracking behaviour in SHCC in direct tensile and flexural tests by using AE. A better understanding of the development of microcracks in SHCC will lead to a better understanding of pseudo strain-hardening behaviour of SHCC and its general performance. ARAMIS optical deformation analysis was also used in direct tensile tests to observe crack propagation in SHCC materials. For the direct tensile tests, SHCC specimens were prepared with polyvinyl alcohol (PVA) fibre with three different volume percentages (1%, 1.85% and 2.5%). For the flexural test beam specimens, only a fibre dosage of 1.85% was applied. It was found that the application of AE in SHCC can be a good option to analyse the crack growth in the specimens under increasing load, the location of the cracks and most importantly the identification of matrix cracking and fibre rupture or slippage.

  11. Influence of Hardening Model on Weld Residual Stress Distribution

    Energy Technology Data Exchange (ETDEWEB)

    Mullins, Jonathan; Gunnars, Jens (Inspecta Technology AB, Stockholm (Sweden))

    2009-06-15

    This study is the third stage of a project sponsored by the Swedish Radiation Safety Authority (SSM) to improve the weld residual stress modelling procedures currently used in Sweden. The aim of this study was to determine which material hardening model gave the best agreement with experimentally measured weld residual stress distributions. Two girth weld geometries were considered: 19mm and 65mm thick girth welds with Rin/t ratios of 10.5 and 2.8, respectively. The FE solver ABAQUS Standard v6.5 was used for analysis. As a preliminary step some improvements were made to the welding simulation procedure used in part one of the project. First, monotonic stress strain curves and a mixed isotropic/kinematic hardening model were sourced from the literature for 316 stainless steel. Second, more detailed information was obtained regarding the geometry and welding sequence for the Case 1 weld (compared with phase 1 of this project). Following the preliminary step, welding simulations were conducted using isotropic, kinematic and mixed hardening models. The isotropic hardening model gave the best overall agreement with experimental measurements; it is therefore recommended for future use in welding simulations. The mixed hardening model gave good agreement for predictions of the hoop stress but tended to under estimate the magnitude of the axial stress. It must be noted that two different sources of data were used for the isotropic and mixed models in this study and this may have contributed to the discrepancy in predictions. When defining a mixed hardening model it is difficult to delineate the relative contributions of isotropic and kinematic hardening and for the model used it may be that a greater isotropic hardening component should have been specified. The kinematic hardening model consistently underestimated the magnitude of both the axial and hoop stress and is not recommended for use. Two sensitivity studies were also conducted. In the first the effect of using a

  12. Reduction of work hardening rate in low-carbon steels

    Science.gov (United States)

    Yalamanchili, Bhaskar Rao

    Low carbon grades of steel rods are used to produce finished products such as fine wire, coat hangers, staples, and roofing nails. These products are subject to ductility failures during production due to excessively high work hardening rates during wire drawing. The high work hardening rates are attributed to the presence of residuals, free nitrogen, or combinations thereof. This research concludes that the most cost-effective way to reduce the work hardening rate during wire drawing is to combine boron with nitrogen to form boron nitride, and thus reducing its work hardening contribution. The results of this study also conclude the following: (1) Boron/Nitrogen ratio is the more significant factor than rod tensile strength, which affects work hardening rate. Higher ratio is better in the 0.79 to 1.19 range. (2) Maintaining this narrow B/N range requires precise process control. (3) Process conditions such as dissolved oxygen (Steel Texas (North Star) benefited from this research by being able to provide a competitive edge in both quality and cost of its low carbon boron grades thus making North Star a preferred supplier of wire rod for these products.

  13. Cryptographic Path Hardening: Hiding Vulnerabilities in Software through Cryptography

    CERN Document Server

    Ganesh, Vijay; Rinard, Martin

    2012-01-01

    We propose a novel approach to improving software security called Cryptographic Path Hardening, which is aimed at hiding security vulnerabilities in software from attackers through the use of provably secure and obfuscated cryptographic devices to harden paths in programs. By "harden" we mean that certain error-checking if-conditionals in a given program P are replaced by equivalent" we mean that adversaries cannot use semi-automatic program analysis techniques to reason about the hardened program paths and thus cannot discover as-yet-unknown errors along those paths, except perhaps through black-box dictionary attacks or random testing (which we can never prevent). Other than these unpreventable attack methods, we can make program analysis aimed at error-finding "provably hard" for a resource-bounded attacker, in the same sense that cryptographic schemes are hard to break. Unlike security-through-obscurity, in Cryptographic Path Hardening we use provably-secure crypto devices to hide errors and our mathemati...

  14. General Friction Model Extended by the Effect of Strain Hardening

    DEFF Research Database (Denmark)

    Nielsen, Chris V.; Martins, Paulo A.F.; Bay, Niels

    2016-01-01

    An extension to the general friction model proposed by Wanheim and Bay [1] to include the effect of strain hardening is proposed. The friction model relates the friction stress to the fraction of real contact area by a friction factor under steady state sliding. The original model for the real co...... of friction in metal forming, where the material generally strain hardens. The extension of the model to cover strain hardening materials is validated by comparison to previously published experimental data.......An extension to the general friction model proposed by Wanheim and Bay [1] to include the effect of strain hardening is proposed. The friction model relates the friction stress to the fraction of real contact area by a friction factor under steady state sliding. The original model for the real......-ideally plastic material, and secondly, to extend the solution by the influence of material strain hardening. This corresponds to adding a new variable and, therefore, a new axis to the general friction model. The resulting model is presented in a combined function suitable for e.g. finite element modeling...

  15. DIMENSIONAL STABILITY OF METHYL METHACRYLATE HARDENED HYBRID POPLAR WOOD

    Directory of Open Access Journals (Sweden)

    Wei-Dan Ding,

    2011-11-01

    Full Text Available This study examines the dimensional stability of fast-growing poplar clones wood after treatment by impregnation with methyl methacrylate (MMA. Six hybrid poplar clones from one plantation in Quebec were sampled. The effects of hardening with MMA on density as well as longitudinal, radial, tangential, and volumetric swelling properties (S, water uptake capacity (D, anti-swelling efficiency (ASE, and water repellent efficiency (WRE after soaking were investigated. Hardening treatment increased the density of all poplar woods by 1.2 to 1.6 and decreased the inner water migration rate during soaking. S and D values of hardened woods were significantly lower than those of controls, depending on the clone type. ASE and WRE values suggested that incorporating MMA effectively improved the dimensional stability of poplar wood at the early soaking stage, but was less effective in the long term.

  16. Ion-irradiation-induced hardening in Inconel 718

    Science.gov (United States)

    Hunn, J. D.; Lee, E. H.; Byun, T. S.; Mansur, L. K.

    2001-07-01

    Inconel 718 is a material under consideration for areas in the target region of the spallation neutron source (SNS), now under construction at Oak Ridge National Laboratory (ORNL) in the US. In these positions, displacement damage from protons and neutrons will affect the mechanical properties. In addition, significant amounts of helium and hydrogen will build up in the material due to transmutation reactions. Nanoindentation measurements of solution-annealed (SA) Inconel 718 specimens, implanted with Fe-, He-, and H-ions to simulate SNS target radiation conditions, have shown that hardening occurs due to ion-induced displacement damage as well as due to the build-up of helium bubbles in the irradiated layer. Precipitation-hardened (PH) Inconel 718 also exhibited hardening by helium build-up but showed softening as a function of displacement damage due to dissolution of the γ ' and γ″ precipitates.

  17. Surface hardening of steel in a solar furnace

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, G.P. [UCLM, ETSII, Ciudad Real (Spain); Damborenea, J.J. de [CENIM-CSIC, Madrid (Spain); Vazquez, A.J. [CENIM-CSIC, Madrid (Spain)

    1997-07-01

    The concentration of solar energy provides the possibility to get power densities high enough to produce surface modifications of materials, with low environmental impact. The present paper discusses the possibilities of surface hardening steel by means of concentrated solar energy. Surface treatments have been made by using the solar furnace of the Platafoma Solar in Almeria (Spain), which consists of a group of heliostats and a parabolic mirror. The surface transformation hardening treatment was performed on a 40CrMo4 steel. The paper presents the microstructural changes and the hardness values obtained after the solar treatment in a superficial zone. According to the power density applied on the sample, the hardened zone varied between 1 and 10 mm deep and the treatment time was less than 30 s. (orig.)

  18. Influence of coolant motion on structure of hardened steel element

    Directory of Open Access Journals (Sweden)

    A. Kulawik

    2008-08-01

    Full Text Available Presented paper is focused on volumetric hardening process using liquid low melting point metal as a coolant. Effect of convective motion of the coolant on material structure after hardening is investigated. Comparison with results obtained for model neglecting motion of liquid is executed. Mathematical and numerical model based on Finite Element Metod is described. Characteristic Based Split (CBS method is used to uncouple velocities and pressure and finally to solve Navier-Stokes equation. Petrov-Galerkin formulation is employed to stabilize convective term in heat transport equation. Phase transformations model is created on the basis of Johnson-Mehl and Avrami laws. Continuous cooling diagram (CTPc for C45 steel is exploited in presented model of phase transformations. Temporary temperatures, phases participation, thermal and structural strains in hardening element and coolant velocities are shown and discussed.

  19. THE MACHINING OF HARDENED CARBON STEELS BY COATED CUTTING TOOLS

    Directory of Open Access Journals (Sweden)

    Yusuf ŞAHİN

    2001-02-01

    Full Text Available The investigation of machining AISI 1050 carbon steels hardened to the 60 HRC hardness was carried out to determine the tool life and wear behaviour of the various cutting tools under different conditions. These experiments were conducted at using coated ceramic cutting tools and carbide cutting tools. The experimental results showed that the coated ceramic tools exhibited better performance than those of the coated carbide tools when machining the hardened steels. Moreover, wear behaviour of cutting tools were investigated in a scanning electron microscope. Electron microscopic examination also indicated that flank wear, thermal cracks on the tool nose combined with the nose deformation on the tools were responsible for the wear behaviour of the ceramic tools. For the carbide tools, however, removal of coated material from the substrate tool and combined with the crater wear were effective for the machining the hardened steel.

  20. Stress field near an interface edge of linear hardening materials

    Institute of Scientific and Technical Information of China (English)

    许金泉; 付列东

    2002-01-01

    The elastic-plastic singular stress field near an interface edge of bounded linear hardening material is substantially as same as that of bonded elastic materials whose Young' s modulus and Poisson ratio are substituted by equivalent values, respectively. Further investigation by the elasto-plastic boundary element method (BEM) on the stress field near the interface edge showed that the stress field there can be divided into three regions: the domain region of the elastic-plastic singular stress field, the transitional region and the elastic region. The domain region of the elastic-plastic singular stress becomes larger with the increasing of the linear hardening coefficient. When the linear hardening coefficient decreases to a certain value, the effective stress in most of the yield zone equals approximately the yield stress. The stress distribution in the elastic region under small-scale yielding condition was also investigated.

  1. Stress field near an interface edge of linear hardening materials

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The elastic-plastic singular stress field near an interface edge of bounded linear hardening material is substantially as same as that of bonded elastic materials whose Young's modulus and Poisson ratio are substituted by equivalent values, respectively. Further investigation by the elasto-plastic boundary element method (BEM) on the stress field near the interface edge showed that the stress field there can be divided into three regions: the domain region of the elastic-plastic singular stress field, the transitional region and the elastic region. The domain region of the elastic-plastic singular stress becomes larger with the increasing of the linear hardening coefficient. When the linear hardening coefficient decreases to a certain value, the effective stress in most of the yield zone equals approximately the yield stress. The stress distribution in the elastic region under small-scale yielding condition was also investigated.

  2. Characterization of Scattered X-Ray Photons in Dental Cone-Beam Computed Tomography.

    Directory of Open Access Journals (Sweden)

    Ching-Ching Yang

    Full Text Available Scatter is a very important artifact causing factor in dental cone-beam CT (CBCT, which has a major influence on the detectability of details within images. This work aimed to improve the image quality of dental CBCT through scatter correction.Scatter was estimated in the projection domain from the low frequency component of the difference between the raw CBCT projection and the projection obtained by extrapolating the model fitted to the raw projections acquired with 2 different sizes of axial field-of-view (FOV. The function for curve fitting was optimized by using Monte Carlo simulation. To validate the proposed method, an anthropomorphic phantom and a water-filled cylindrical phantom with rod inserts simulating different tissue materials were scanned using 120 kVp, 5 mA and 9-second scanning time covering an axial FOV of 4 cm and 13 cm. The detectability of the CT image was evaluated by calculating the contrast-to-noise ratio (CNR.Beam hardening and cupping artifacts were observed in CBCT images without scatter correction, especially in those acquired with 13 cm FOV. These artifacts were reduced in CBCT images corrected by the proposed method, demonstrating its efficacy on scatter correction. After scatter correction, the image quality of CBCT was improved in terms of target detectability which was quantified as the CNR for rod inserts in the cylindrical phantom.Hopefully the calculations performed in this work can provide a route to reach a high level of diagnostic image quality for CBCT imaging used in oral and maxillofacial structures whilst ensuring patient dose as low as reasonably achievable, which may ultimately make CBCT scan a reliable and safe tool in clinical practice.

  3. INFLUENCE OF MICROALLOYING BY BORON ON HARDENABILITY OF STEEL

    Directory of Open Access Journals (Sweden)

    E. P. Baradyntseva

    2016-01-01

    Full Text Available The research conducted in laboratory of metallurgical science by which the factors exerting impact on hardenability of steel microalloyed by boron were analysed. The research was made because the implementation of this process in mass production is connected with the certain difficulties. The conducted researches have allowed to draw a conclusion that changing content of various chemical elements, such as nitrogen, boron, the titan and aluminum in steel containing boron, produced by JSC «BSW – Management Company of Holding «BMC» at the stage of preparation of chart flowsheet make it possible to predict terms of hardenability of the final product.

  4. Aspect-oriented security hardening of UML design models

    CERN Document Server

    Mouheb, Djedjiga; Pourzandi, Makan; Wang, Lingyu; Nouh, Mariam; Ziarati, Raha; Alhadidi, Dima; Talhi, Chamseddine; Lima, Vitor

    2015-01-01

    This book comprehensively presents a novel approach to the systematic security hardening of software design models expressed in the standard UML language. It combines model-driven engineering and the aspect-oriented paradigm to integrate security practices into the early phases of the software development process. To this end, a UML profile has been developed for the specification of security hardening aspects on UML diagrams. In addition, a weaving framework, with the underlying theoretical foundations, has been designed for the systematic injection of security aspects into UML models. The

  5. Laser hardening processing on tool steel SKD61

    Institute of Scientific and Technical Information of China (English)

    金.弗拉基米尔.阿列克谢耶维奇

    2015-01-01

    This paper is aimed at overcoming different degree defects of crystalline structure in SKD61 carbide tool steel under quenching in solid phase and liquid phase. The paper studies the micro-structure and properties of laser strengthening SKD61 by using the method of laser hardening on the rein-forcement to improve the wear resistance of SKD61 . The results showed that the laser strengthening meth-od can improve the wear resistance of SKD61 . The study can provide reference for laser hardening metal materials.

  6. Diffusive Origin of the Cosmic-Ray Spectral Hardening

    CERN Document Server

    Tomassetti, N

    2012-01-01

    Recent data from ATIC, CREAM and PAMELA revealed that the energy spectra of cosmic ray (CR) nuclei above 100 GeV/nucleon experience a remarkable hardening with increasing energy. This effect cannot be recovered by the conventional descriptions of CR acceleration and diffusive propagation processes. Using analytical calculations, I show that the hardening effect can be consequence of a spatial change of the CR diffusion properties in different regions of the Galaxy. I discuss the implications of this scenario for the main CR observables and its connections with the open issues of the CR physics.

  7. Microstructure and properties of cast iron after laser surface hardening

    Directory of Open Access Journals (Sweden)

    Stanislav

    2013-12-01

    Full Text Available Laser surface hardening of cast iron is not trivial due to the material’s heterogeneity and coarse-grained microstructure, particularly in massive castings. Despite that, hardening of heavy moulds for automotive industry is in high demand. The present paper summarises the findings collected over several years of study of materials structure and surface properties. Phase transformations in the vicinity of graphite are described using examples from production of body parts in automotive industry. The description relates to formation of martensite and carbide-based phases, which leads to hardness values above 65 HRC and to excellent abrasion resistance.

  8. ASSESSMENT OF KINETIC PROCESSES OF HARDENING OF BUILDING MATERIALS

    Directory of Open Access Journals (Sweden)

    P. V. Voronov

    2010-12-01

    Full Text Available Problem statement. Kinetic processes are of huge importance when producing building units and operating them as well. However, both technological and operation parameters are determined by the structure of a material under study.Results and conclusions. Kinetics with asymptotic approximation at hardening of building materials is analyzed. The validity of use of new kinetic equation is proved, characterizing harden composite systems and taking into consideration structural and topological peculiarities of new solid-like phase formation directly effecting the evolution of the processes. Results of research of change of strength at solidification a cement-sandy solution with various additives are submitted.

  9. Radiation Hardened 10BASE-T Ethernet Physical Layer (PHY)

    Science.gov (United States)

    Lin, Michael R. (Inventor); Petrick, David J. (Inventor); Ballou, Kevin M. (Inventor); Espinosa, Daniel C. (Inventor); James, Edward F. (Inventor); Kliesner, Matthew A. (Inventor)

    2017-01-01

    Embodiments may provide a radiation hardened 10BASE-T Ethernet interface circuit suitable for space flight and in compliance with the IEEE 802.3 standard for Ethernet. The various embodiments may provide a 10BASE-T Ethernet interface circuit, comprising a field programmable gate array (FPGA), a transmitter circuit connected to the FPGA, a receiver circuit connected to the FPGA, and a transformer connected to the transmitter circuit and the receiver circuit. In the various embodiments, the FPGA, transmitter circuit, receiver circuit, and transformer may be radiation hardened.

  10. Effect on Hydration and Hardening of Tricalcium Phosphate Bone Cement

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The bioactive α-Ca3 (PO4)2 bone cement was studied by XRD , SEM and isothermal calorimetric measurements. The results showed that a mixed pattern of TCP and hydroxylapatite were obtained after hydration and hardening. The mechanism of hydration and hardening of the α-Ca3 ( PO4 )2 was dissolution-precipitation,(NH4) H2 PO4 was the best set accelerator to the α-Ca3 ( PO4 )2 cement, and the HAP powers and the(NH4) H2 PO4 concentration had a great effect on the hydration rate of α-Ca3 ( PO4 )2.

  11. Temperature Development during Hardening of Large Concrete Cubes

    DEFF Research Database (Denmark)

    Sørensen, Eigil V.; Burcharth, Hans Falk

    The purpose ofthe project is to verify ifthermal cracking will occur in large unreinforced concrete cubes due to large temperature differences during hardening o f the concrete. The first part o f the project is to numerically simulate the temperature development during hardening, evaluate the risk...... of thermally induced crackingunder varying execution conditions, and verify the temperature calculations by caJTying out measurements in situ. The cubes are cast and cured under marine environmental conditions in the north western part of Spain and are to serve as coastal proteetion in a harbour under...

  12. Temperature Development during Hardening of Large Concrete Cubes

    DEFF Research Database (Denmark)

    Sørensen, Eigil V.; Burcharth, Hans Falk

    The purpose ofthe project is to verify ifthermal cracking will occur in large unreinforced concrete cubes due to large temperature differences during hardening o f the concrete. The first part o f the project is to numerically simulate the temperature development during hardening, evaluate the risk...... of thermally induced cracking under varying execution conditions, and verify the temperature calculations by carrying out measurements in situ. The cubes are cast and cured under marine environmental conditions in the north western part of Spain and are to serve as coastal proteetion in a harbour under...

  13. Impact of Scaled Technology on Radiation Testing and Hardening

    Science.gov (United States)

    LaBel, Kenneth A.; Cohn, Lewis M.

    2005-01-01

    This presentation gives a brief overview of some of the radiation challenges facing emerging scaled digital technologies with implications on using consumer grade electronics and next generation hardening schemes. Commercial semiconductor manufacturers are recognizing some of these issues as issues for terrestrial performance. Looking at means of dealing with soft errors. The thinned oxide has indicated improved TID tolerance of commercial products hardened by "serendipity" which does not guarantee hardness or say if the trend will continue. This presentation also focuses one reliability implications of thinned oxides.

  14. Temperature influence on water transport in hardened cement pastes

    Energy Technology Data Exchange (ETDEWEB)

    Drouet, Emeline [CEA, DEN, DPC, SECR, Laboratoire d' Etude du Comportement des Bétons et des Argiles, F-91191 Gif sur Yvette Cedex (France); Poyet, Stéphane, E-mail: stephane.poyet@cea.fr [CEA, DEN, DPC, SECR, Laboratoire d' Etude du Comportement des Bétons et des Argiles, F-91191 Gif sur Yvette Cedex (France); Torrenti, Jean-Michel [Université Paris-Est, IFSTTAR, Département Matériaux & Structures, 14-52 boulevard Newton, F-77447 Marne la Vallée cedex 2 (France)

    2015-10-15

    Describing water transport in concrete is an important issue for the durability assessment of radioactive waste management reinforced concrete structures. Due to the waste thermal output such structures would be submitted to moderate temperatures (up to 80 °C). We have then studied the influence of temperature on water transport within hardened cement pastes of four different formulations. Using a simplified approach (describing only the permeation of liquid water) we characterized the properties needed to describe water transport (up to 80 °C) using dedicated experiments. For each hardened cement paste the results are presented and discussed.

  15. A rapid cold-hardening process in insects.

    Science.gov (United States)

    Lee, R E; Chen, C P; Denlinger, D L

    1987-12-04

    Traditionally studies of cold tolerance in insects have focused on seasonal adaptations related to overwintering that are observed after weeks or months of exposure to low temperature. In contrast, an extremely rapid cold-hardening response was observed in nonoverwintering stages that confers protection against injury due to cold shock at temperatures above the supercooling point. This response was observed in nondiapausing larvae and pharate adults of the flesh fly, Sarcophaga crassipalpis, nondiapausing adults of the elm leaf beetle, Xanthogaleruca luteola, and the milkweed bug, Oncopeltus fasciatus. The rapid hardening response is correlated with the accumulation of glycerol.

  16. Nonlinear dynamics of spring softening and hardening in folded-mems comb drive resonators

    KAUST Repository

    Elshurafa, Amro M.

    2011-08-01

    This paper studies analytically and numerically the spring softening and hardening phenomena that occur in electrostatically actuated microelectromechanical systems comb drive resonators utilizing folded suspension beams. An analytical expression for the electrostatic force generated between the combs of the rotor and the stator is derived and takes into account both the transverse and longitudinal capacitances present. After formulating the problem, the resulting stiff differential equations are solved analytically using the method of multiple scales, and a closed-form solution is obtained. Furthermore, the nonlinear boundary value problem that describes the dynamics of inextensional spring beams is solved using straightforward perturbation to obtain the linear and nonlinear spring constants of the beam. The analytical solution is verified numerically using a Matlab/Simulink environment, and the results from both analyses exhibit excellent agreement. Stability analysis based on phase plane trajectory is also presented and fully explains previously reported empirical results that lacked sufficient theoretical description. Finally, the proposed solutions are, once again, verified with previously published measurement results. The closed-form solutions provided are easy to apply and enable predicting the actual behavior of resonators and gyroscopes with similar structures. © 2011 IEEE.

  17. Phenomenological interpretation of the shear behavior of reinforced Engineered Cementitious Composite beams

    DEFF Research Database (Denmark)

    Paegle, Ieva; Fischer, Gregor

    2016-01-01

    This paper describes an experimental investigation of the shear behavior of beams consisting of steel Reinforced Engineered Cementitious Composites (R/ECC). This study investigates and quantifies the effect of ECC's strain hardening and multiple cracking behavior on the shear capacity of beams lo...

  18. Beam lead microelectronics. Citations from the NTIS data base

    Science.gov (United States)

    Reed, W. E.

    1980-04-01

    The technology and application of beam lead devices are treated in these Federally-sponsored research reports. Topics include design, fabrication, bonding, packaging, testing, and radiation hardening. This updated bibliography contains 85 abstracts, 4 of which are new entries to the previous edition.

  19. Study of beam-beam long range compensation with octupoles

    CERN Document Server

    Barranco Garcia, Javier; Buffat, Xavier; Tambasco, Claudia

    2017-01-01

    Long range beam-beam effects are responsible for particle losses and define fundamental operational parameters of colliders (i.e. crossing angles, intensities, emittances, ${\\beta}$${^∗}$). In this study we propose octuple magnets as a possible scheme to efficiently compensate long-range beam-beam interactions with a global correction scheme. The impact and improvements on the dynamic aperture of colliding beams together with estimates of the luminosity potentials are dis- cussed for the HL-LHC upgrade and extrapolations made for the FCC project.

  20. Research into Grinding Hardening of Microalloyed Non-quenched and Tempered Steel

    Institute of Scientific and Technical Information of China (English)

    HAN Zheng-tong; ZHANG Ning-ju; GAO Ding; YANG Gang

    2007-01-01

    Grinding hardening is a new technology of hardening steel piece surfaces with grinding heat generated in the grinding process instead of with a high or medium frequency induction heating method, which can effectively integrate grinding and surface hardening. Experimental studies were carried out on grinding hardening of non-quenched and tempered steel. Through grinding experiments with variable depths of cut and feeding rate, the variation in the depth of the hardening layer was studied and the microstructure of the hardening zone of the test pieces was subsequently analyzed. In the end, the hardening effect of non-quenched and tempered steel was compared with that of 40Cr steel, which revealed the superiority of non-quenched and tempered steel in grinding hardening technology.

  1. Differential hardening in IF steel - Experimental results and a crystal plasticity based model

    NARCIS (Netherlands)

    Mulder, J.; Eyckens, P.; van den Boogaard, Antonius H.; Hora, P.

    2015-01-01

    Work hardening in metals is commonly described by isotropic hardening, especially for monotonically increasing proportional loading. The relation between different stress states in this case is determined by equivalent stress and strain definitions, based on equal plastic dissipation. However,

  2. Rapid cold hardening process of insects and its ecologically adaptive significance

    Institute of Scientific and Technical Information of China (English)

    WANG Xianhui; QI Xianlei; KANG Le

    2003-01-01

    In contrast to overwintering cold hardening, a rapid cold hardening process has recently been described in insects. This process can rapidly enhance cold tolerance of insects in several hours or even minutes. The characteristics of rapid cold hardening include inducing conditions, cold hardening effects, and fitness costs. Physiological and biochemical mechanisms of rapid cold hardening include rapid changes in the phospholipid composition and the increase in hemolymph osmolalities, polyols production, proline and cold-induced proteins. Moreover, there are different views about the ecologically adaptive significance of rapid cold hardening in insects. This paper reviews research results about rapid cold hardening of insects since 1987, focusing on forms of cold injury, strategies of cold tolerance, and definitions, characteristics, physiological and biochemical mechanisms and adaptive significance of rapid cold hardening.

  3. Effect of hardening methods of moulding sands with water glass on structure of bonding bridges

    Directory of Open Access Journals (Sweden)

    M. Stachowicz

    2010-07-01

    Full Text Available Research on influence of hardening methods on structure of bonding bridges in moulding sands with sodium water glass is presented.Moulding sands with addition of 2.5 % of binder with molar module 2.0 were hardened with CO2 and dried in traditional way or hardenedwith microwaves. It was proved that the hardening method affects structure of bonding bridges, correlating with properties of the hardened moulding sands. It was found that strength of the moulding sands hardened with microwaves for 4 min is very close to that measured after traditional drying at 110 °C for 120 min. So, application of microwave hardening ensures significant shortening of the process time to the value comparable with CO2 hardening but guaranteeing over 10-fold increase of mechanical properties. Analysis of SEM images of hardened moulding sands permitted explaining differences in quality parameters of moulding sands by connecting them with structure of the created bonding bridges.

  4. Corroding and Protecting of Surface Residual Stress With the Surface Hardening of Steel

    Institute of Scientific and Technical Information of China (English)

    ZOU Qing-hua

    2004-01-01

    The states of the stress with the surface hardening are analyzed, the related experiential formula of the stress -temperature and stress-depth hardened curves are set up, the protecting measures against hydrogen stress corrosion are discussed.

  5. Analysis of Laser Surface Hardened Layers of Automobile Engine Cylinder Liner

    Institute of Scientific and Technical Information of China (English)

    LIU Xiu-bo; YU Gang; GUO Jian; SHANG Quan-yi; ZHANG Zhen-guo; GU Yi-jie

    2007-01-01

    Gray cast iron that is used for automobile engine cylinder liners was laser surface hardened using Nd∶YAG quasi-continuous and CO2 continuous wave laser, respectively. The macromorphology and microstructure of the laser surface hardened layers were investigated using an optical microscope. Geometric dimensions including depth and width and microhardness distribution of the hardened layers were also examined in order to evaluate the quality of the hardened layers.

  6. Hardening digital systems with distributed functionality: robust networks

    Science.gov (United States)

    Vaskova, Anna; Portela-Garcia, Marta; Garcia-Valderas, Mario; López-Ongil, Celia; Portilla, Jorge; Valverde, Juan; de la Torre, Eduardo; Riesgo, Teresa

    2013-05-01

    Collaborative hardening and hardware redundancy are nowadays the most interesting solutions in terms of fault tolerance achieved and low extra cost imposed to the project budget. Thanks to the powerful and cheap digital devices that are available in the market, extra processing capabilities can be used for redundant tasks, not only in early data processing (sensed data) but also in routing and interfacing1

  7. Hardening by twin boundary during nanoindentation in nanocrystals.

    Science.gov (United States)

    Qu, Shaoxing; Zhou, Haofei

    2010-08-20

    The atomistic deformation processes of nanocrystals embedded with nanoscale twin boundaries during nanoindentation are studied by molecular dynamics simulations. Load-displacement curves are obtained and the hardening mechanisms associated with the nanoscale twin boundaries are revealed. Johnson's theoretical indentation model is adopted to estimate the elastic stage of the nanoindentation. In addition, twin boundary-mediated dislocation nucleation is observed and analyzed.

  8. Preparation of Dispersion-Hardened Copper by Internal Oxidation

    DEFF Research Database (Denmark)

    Brøndsted, Povl; Sørensen, Ole Toft

    1978-01-01

    Internal oxidation experiments in CO2/CO atmospheres on Cu-Al alloys for preparation of dispersion-hardened Cu are described. The oxygen pressures of the atmospheres used in the experiments were controlled with a solid electrolyte oxygen cell based on ZrO2 (CaO). The particle size distributions...

  9. Coefficient of work-hardening in stage-IV

    CSIR Research Space (South Africa)

    Nabarro, FRN

    1994-04-15

    Full Text Available The theory of work hardening in stage IV depends on the relation between the relative misorientation Psi of neighbouring subgrains and the plastic strain gamma (Psi = B gamma exp). The value of the constant B is suggested to be better related...

  10. Decorative application of strain-hardening cementitious composites

    NARCIS (Netherlands)

    Ibrovic, V.; Lukovic, M.; Schlangen, E.

    2014-01-01

    Strain hardening cementitious composites (SHCC) have been used in variety of structural applications. Apart from this, they are also suitable for non-structural applications. In this work, the application of SHCC for producing cover plates for light switches and power sockets is presented. For desig

  11. Case Depth Measurement of Induction Hardening Using Image Processing

    Institute of Scientific and Technical Information of China (English)

    Kitti Pongsathaporn; Pramuk Jenkittiyon; Siriporn Daopiset; Somnuk Watanasriyakul

    2004-01-01

    Case depth measurement of the induction hardened steel parts is necessary for quality control. Vickers microhardness test is the most industrially accepted method to identify the case depth. But this method is a time consuming one and it requires expensive equipment. The aim of this study is to develop a different method to determine the case depth using image processing. The surface hardened steel samples were cross cut, ground and etched with Nital. The etched macrosectioned specimens were scanned by a scanner. The scanned images were evaluated by the developed software. The principle of the software is to identify the gray level difference. The effective case depths of the surface hardened specimens obtained by Vickers microhardness test and the developed method were compared. It was found that the deviation of the developed method was ±0.12 mm at the case depth range of 0.6 - 2.0 mm and ±0.14 mm at the case depth range of 2.1 - 4.3 mm. The measuring time was only 20% of Vickers microhardness test. The deviation range is much lower than the tolerance case depth specification for induction hardening in general.

  12. Decorative application of strain-hardening cementitious composites

    NARCIS (Netherlands)

    Ibrovic, V.; Lukovic, M.; Schlangen, E.

    2014-01-01

    Strain hardening cementitious composites (SHCC) have been used in variety of structural applications. Apart from this, they are also suitable for non-structural applications. In this work, the application of SHCC for producing cover plates for light switches and power sockets is presented. For

  13. Modelling polychromatic high energy photon beams by superposition.

    Science.gov (United States)

    Metcalfe, P E; Hoban, P W; Murray, D C; Round, W H

    1989-09-01

    A unified three dimensional superposition approach to dose calculations used in treatment planning of polychromatic high energy photon beams in radiotherapy is developed. The approach we have used involves computing the dose at all points in a medium by superposing the dose spread array (DSA) from the interaction of a photon at a point in the medium with an array of data representing the TERMA (photon fluence times the photon energy) at points in the beam. The polychromatic nature of the beam is accounted for by modelling the beam as having ten spectral components. A "polychromatic dose spread array" (PDSA) for an interaction from a beam with this spectrum was derived. The TERMA array is calculated from a weighted average of the TERMA arrays for the ten photon energies to give a "polychromatic TERMA array". Thus the method accounts for the effect of beam hardening of the TERMA. But it does not account for the effect of beam hardening on the PDSA since a single PDSA (usually for the spectrum at the surface of the medium) is used at all depths. However, by considering measured and calculated beam central axis data, this model is shown to be adequate for computing depth doses for beams in a homogeneous medium penetrating to extreme radiological depths. A computation time advantage is gained because only one superposition per beam is required.

  14. Single Event Upset Detection and Hardening schemes for CNTFET SRAM – A Review

    Directory of Open Access Journals (Sweden)

    T.R.Rajalakshmi

    2015-12-01

    Full Text Available Carbon nanotubes (CNT provide a better alternative of silicon, when it comes to nano scales. Thanks to its high stability and high performance of carbon nanotube, CNT based FET (CNTFET devices which are gaining popularity of late. Single Event Upset (SEU in a device is caused due to radiation. Radiation can be through two ways, one due to charge particles present in the atmosphere and other due to alpha particles. In this article we review some of the detection and hardening schemes in CMOS SRAM and make related simulations on CNTFET SRAM. The aim of this paper is to present the challenges the CNTFET SRAM is facing when the radiation effects are introduced. A full experimentation of all the schemes of detection and correction schemes will be beyond the scope, so only certain experiments that can be well carried out with CNTFET SRAM memory is more focussed.

  15. Control And Transport Of Intense Electron Beams

    CERN Document Server

    Li, H

    2004-01-01

    The transport of intense beams for advanced accelerator applications with high-intensity beams such as heavy-ion inertial fusion, spallation neutron sources, and intense light sources requires tight control of beam characteristics over long distances. The University of Maryland Electron Ring (UMER), which uses low energy, high current electron beams to model the transport physics of intense space-charge-dominated beams, employs real-time beam characterization and control in order to optimize beam quality throughout the strong focusing lattice. We describe in this dissertation the main beam control techniques used in UMER, which include optimal beam steering by quadrupole scans, beam rotation correction using a skew corrector, rms envelope matching and optimization, empirical envelope matching, beam injection, and phase space reconstruction using a tomographic method. Using these control techniques, we achieved the design goals for UMER. The procedure is not only indispensable for optimum beam transport over l...

  16. Theoretical Studies of Laws Nanostructuring and Heterogeneous Hardening of Steel Samples by Wave Intensive Plastic Deformation

    Directory of Open Access Journals (Sweden)

    A.V. Kirichek

    2015-12-01

    Full Text Available Theoretical studies and calculations, allowing to define the required parameters of the wave deformation hardening, are performed in order to obtain heterogeneous hardened surface layer in steel samples. The conditions for the effective use of impact energy for elastic-plastic deformation of the processed material and the establishment of a deep hardened surface layer are revealed.

  17. Application of Artificial Neural Network to Predicting Hardenability of Gear Steel

    Institute of Scientific and Technical Information of China (English)

    GAO Xiu-hua; QI Ke-min; DENG Tian-yong; QIU Chun-lin; ZHOU Ping; DU Xian-bin

    2006-01-01

    The prediction of the hardenability and chemical composition of gear steel was studied using artificial neural networks. A software was used to quantitatively forecast the hardenability by its chemical composition or the chemical composition by its hardenability. The prediction result is more precise than that obtained from the traditional method based on the simple mathematical regression model.

  18. The prediction of differential hardening behaviour of steels by multi-scale crystal plasticity modelling

    NARCIS (Netherlands)

    Eyckens, P.; Mulder, J.; Gawad, J.; Vegter, H.; Roose, D.; Boogaard, van den A.H.; Van Bael, A.; Van Houtte, P.

    2015-01-01

    An essential aspect of materials modelling in the field of metal plasticity is hardening. The classical assumption of isotropic hardening in metal plasticity models is often too simplified to describe actual material behaviour. This paper focuses on the non-isotropic hardening termed differential ha

  19. Longitudinal wake field corrections in circular machines

    Energy Technology Data Exchange (ETDEWEB)

    Symon, K.R.

    1996-10-01

    In computations of longitudinal particle motions in accelerators and storage rings, the fields produced by the interactions of the beam with the cavity in which it circulates are usually calculated by multiplying Fourier components of the beam current by the appropriate impedances. This procedure neglects the slow variation with time of the Fourier coefficients and of the beam revolution frequency. When there are cavity elements with decay times that are comparable with or larger than the time during which changes in the beam parameters occur, these changes can not be neglected. Corrections for this effect have been worked out in terms of the response functions of elements in the ring. The result is expressed as a correction to the impedance which depends on the way in which the beam parameters are changing. A method is presented for correcting a numerical simulation by keeping track of the steady state and transient terms in the response of a cavity.

  20. Devising Strain Hardening Models Using Kocks–Mecking Plots—A Comparison of Model Development for Titanium Aluminides and Case Hardening Steel

    Directory of Open Access Journals (Sweden)

    Markus Bambach

    2016-08-01

    Full Text Available The present study focuses on the development of strain hardening models taking into account the peculiarities of titanium aluminides. In comparison to steels, whose behavior has been studied extensively in the past, titanium aluminides possess a much larger initial work hardening rate, a sharp peak stress and pronounced softening. The work hardening behavior of a TNB-V4 (Ti–44.5Al–6.25Nb–0.8Mo–0.1B alloy is studied using isothermal hot compression tests conducted on a Gleeble 3500 simulator, and compared to the typical case hardening steel 25MoCrS4. The behavior is analyzed with the help of the Kocks-Mecking plots. In contrast to steel the TNB-V4 alloy shows a non-linear course of θ (i.e., no stage-III hardening initially and exhibits neither a plateau (stage IV hardening nor an inflection point at all deformation conditions. The present paper describes the development and application of a methodology for the design of strain hardening models for the TNB-V4 alloy and the 25CrMoS4 steel by taking the course of the Kocks-Mecking plots into account. Both models use different approaches for the hardening and softening mechanisms and accurately predict the flow stress over a wide range of deformation conditions. The methodology may hence assist in further developments of more sophisticated physically-based strain hardening models for TiAl-alloys.

  1. Microstructural variation of hardened cement-fly ash pastes leached by soft water

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The microstructural variations of hardened cement-fly ash pastes leached by soft water were investigated by MIP, XRD, TG and SEM. The results show that the mass of hardened cement-fly ash paste reduces and its microstructure deteriorates partly after leaching of soft water. At the leaching duration of 180 days, the hardened paste containing fly ash deteriorated a little more serious than the plain cement paste, but the incorporation of fly ash in a proper ratio was helpful to defer the trend of deterioration of the hardened paste microstructure. The microstructural stability of hardened cement-fly ash paste wasn’t damaged severely during the 180 days leaching duration.

  2. Effect of hardening methods of moulding sands with water glass on structure of bonding bridges

    OpenAIRE

    Stachowicz, M.; K. Granat; Nowak, D.

    2010-01-01

    Research on influence of hardening methods on structure of bonding bridges in moulding sands with sodium water glass is presented.Moulding sands with addition of 2.5 % of binder with molar module 2.0 were hardened with CO2 and dried in traditional way or hardenedwith microwaves. It was proved that the hardening method affects structure of bonding bridges, correlating with properties of the hardened moulding sands. It was found that strength of the moulding sands hardened with microwaves for 4...

  3. Design Features of Hardening Turners with Outstripping Plastic Deformation

    Directory of Open Access Journals (Sweden)

    V. M. Yaroslavtsev

    2014-01-01

    Full Text Available An efficiency of the cutting method with outstripping plastic deformation (OPD in lathe works is defined in many respects by design features of the add-on devices for mechanical hardening of a cut-off layer material in the course of cutting. Applied on lathes, deforming OPD devices can have differing dimensions, placement on the lathe, drive type (manual, electric, hydraulic, pneumatic, pneumohydraulic, electromagnetic, and autonomy degree towards the metalcutting equipment and industrial equipment.At the same time there are a number of inherent design features of work-hardening devices the modernized lathes with OPD use for machining. Now the OPD standard devices implement two principle construction options: loading device is placed on the machine or on the OPD slide support separate of the tool, or it is structurally aligned with the cutting tool. In the latter case the OPD device for turning is called a tool mandrel, which is mounted in a tool post of the machine or, at large dimensions, such a mandrel is mounted on the machine instead of the tool mandrel.When designing the OPD devices, is important to take into consideration production requirements and recommendations for the technological equipment, developed in the course of creation, working off and introduction of such installations for mechanical hardening of material. In compliance with it, OPD devices, their placement on the machine, and working displacements shouldn't limit technological capabilities of the applied metal-cutting equipment. OPD stresses have to be smoothly regulated, with maximum loads being limited to admissible values for the machine model to be modernized. It is necessary to ensure synchronized longitudinal and cross displacements of the cutting tool and OPD hardener with respect to the axis of billet rotation to enable regulation and readjustment of the hardener and tool placement. It ought to foresee the increased mobile components rigidity and manufacturing

  4. Motion correction for improving the accuracy of dual-energy myocardial perfusion CT imaging

    Science.gov (United States)

    Pack, Jed D.; Yin, Zhye; Xiong, Guanglei; Mittal, Priya; Dunham, Simon; Elmore, Kimberly; Edic, Peter M.; Min, James K.

    2016-03-01

    Coronary Artery Disease (CAD) is the leading cause of death globally [1]. Modern cardiac computed tomography angiography (CCTA) is highly effective at identifying and assessing coronary blockages associated with CAD. The diagnostic value of this anatomical information can be substantially increased in combination with a non-invasive, low-dose, correlative, quantitative measure of blood supply to the myocardium. While CT perfusion has shown promise of providing such indications of ischemia, artifacts due to motion, beam hardening, and other factors confound clinical findings and can limit quantitative accuracy. In this paper, we investigate the impact of applying a novel motion correction algorithm to correct for motion in the myocardium. This motion compensation algorithm (originally designed to correct for the motion of the coronary arteries in order to improve CCTA images) has been shown to provide substantial improvements in both overall image quality and diagnostic accuracy of CCTA. We have adapted this technique for application beyond the coronary arteries and present an assessment of its impact on image quality and quantitative accuracy within the context of dual-energy CT perfusion imaging. We conclude that motion correction is a promising technique that can help foster the routine clinical use of dual-energy CT perfusion. When combined, the anatomical information of CCTA and the hemodynamic information from dual-energy CT perfusion should facilitate better clinical decisions about which patients would benefit from treatments such as stent placement, drug therapy, or surgery and help other patients avoid the risks and costs associated with unnecessary, invasive, diagnostic coronary angiography procedures.

  5. Product surface hardening in non-self-sustained glow discharge plasma before synthesis of superhard coatings

    Science.gov (United States)

    Krasnov, P. S.; Metel, A. S.; Nay, H. A.

    2017-05-01

    Before the synthesis of superhard coating, the product surface is hardened by means of plasma nitriding, which prevents the surface deformations and the coating brittle rupture. The product heating by ions accelerated from plasma by applied to the product bias voltage leads to overheating and blunting of the product sharp edges. To prevent the blunting, it is proposed to heat the products with a broad beam of fast nitrogen molecules. The beam injection into a working vacuum chamber results in filling of the chamber with quite homogeneous plasma suitable for nitriding. Immersion in the plasma of the electrode and heightening of its potential up to 50-100 V initiate a non-self-sustained glow discharge between the electrode and the chamber. It enhances the plasma density by an order of magnitude and reduces its spatial nonuniformity down to 5-10%. When a cutting tool is isolated from the chamber, it is bombarded by plasma ions with an energy corresponding to its floating potential, which is lower than the sputtering threshold. Hence, the sharp edges are sputtered only by fast nitrogen molecules with the same rate as other parts of the tool surface. This leads to sharpening of the cutting tools instead of blunting.

  6. Strain Hardening and Size Effect in Five-fold Twinned Ag Nanowires.

    Science.gov (United States)

    Narayanan, Sankar; Cheng, Guangming; Zeng, Zhi; Zhu, Yong; Zhu, Ting

    2015-06-10

    Metallic nanowires usually exhibit ultrahigh strength but low tensile ductility owing to their limited strain hardening capability. Here we study the unique strain hardening behavior of the five-fold twinned Ag nanowires by nanomechanical testing and atomistic modeling. In situ tensile tests within a scanning electron microscope revealed strong strain hardening behavior of the five-fold twinned Ag nanowires. Molecular dynamics simulations showed that such strain hardening was critically controlled by twin boundaries and pre-existing defects. Strain hardening was size dependent; thinner nanowires achieved more hardening and higher ductility. The size-dependent strain hardening was found to be caused by the obstruction of surface-nucleated dislocations by twin boundaries. Our work provides mechanistic insights into enhancing the tensile ductility of metallic nanostructures by engineering the internal interfaces and defects.

  7. Radiation Hardening of LED Luminaires for Accelerator Tunnels

    CERN Document Server

    Devine, James D

    2016-01-01

    This paper summarises progress made towards the radiation hardening of LED emergency luminaires for evacuation and emergency response within the underground areas of the CERN accelerator complex. The objective has been to radiation harden existing Commercial Off-The-Shelf (COTS) emergency luminaires to maximise lighting performance, without compromising IEC 60598-2-22 compliance. A systems level approach has been adopted, leading to the development of a diode bridge based AC/DC power converter. Modified COTS luminaires including this converter design have been irradiated (to 100 kGy TID using a Cobalt-60 source), with results of a subsequent photometric analysis presented. Following encouraging tests results, a reference design for the power converter has been released under the CERN Open Hardware License to encourage manufacturer adoption. The paper concludes with areas of interest for future research in further improving the radiation hardness of LED emergency lighting for accelerators with detailed studies...

  8. Age-hardening in a commercial Mg-based alloy

    Energy Technology Data Exchange (ETDEWEB)

    Macchi, C.E. [IFIMAT, UNCentro and CONICET, Pinto 399, B7000GHG Tandil (Argentina); Somoza, A. [IFIMAT, UNCentro and CICPBA, Pinto 399, B7000GHG Tandil (Argentina); Nie, J.F. [School of Physics and Materials Engineering, PO Box 69M, Monash University, Victoria 3800 (Australia)

    2007-07-01

    Age-hardening phenomena induced by thermal and thermo-mechanical treatments in the commercial Mg-based alloy WE54 were studied by positron annihilation lifetime spectroscopy and Vickers microhardness. To this aim, samples were plastically deformed and subsequently aged at 250 C for times ranging from 0 to 1000 hours. The results obtained are discussed in terms of the role of vacancies in the solute transport and therefore they contribute to the discussion on the vacancy-solute clusters (and/or intermediate precipitates) interactions during the precipitation sequence of the WE54. Besides, we show that cold work previous aging not only accelerates but increases the hardening response of the alloy. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Hardening electronic devices against very high total dose radiation environments

    Science.gov (United States)

    Buchanan, B.; Shedd, W.; Roosild, S.; Dolan, R.

    1972-01-01

    The possibilities and limitations of hardening silicon semiconductor devices to the high neutron and gamma radiation levels and greater than 10 to the eighth power rads required for the NERVA nuclear engine development are discussed. A comparison is made of the high dose neutron and gamma hardening potential of bipolar, metal insulator semiconductors and junction field effect transistors. Experimental data is presented on device degradation for the high neutron and gamma doses. Previous data and comparisons indicate that the JFET is much more immune to the combined neutron displacement and gamma ionizing effects than other transistor types. Experimental evidence is also presented which indicates that p channel MOS devices may be able to meet the requirements.

  10. Poromechanical behaviour of hardened cement paste under isotropic loading

    CERN Document Server

    Ghabezloo, Siavash; Guédon, Sylvine; Martineau, Francçois; Saint-Marc, Jérémie

    2008-01-01

    The poromechanical behaviour of hardened cement paste under isotropic loading is studied on the basis of an experimental testing program of drained, undrained and unjacketed compression tests. The macroscopic behaviour of the material is described in the framework of the mechanics of porous media. The poroelastic parameters of the material are determined and the effect of stress and pore pressure on them is evaluated. Appropriate effective stress laws which control the evolution of total volume, pore volume, solid volume, porosity and drained bulk modulus are discussed. A phenomenon of degradation of elastic properties is observed in the test results. The microscopic observations showed that this degradation is caused by the microcracking of the material under isotropic loading. The good compatibility and the consistency of the obtained poromechanical parameters demonstrate that the behaviour of the hardened cement paste can be indeed described within the framework of the theory of porous media.

  11. Laser surface hardening of AISI H13 tool steel

    Institute of Scientific and Technical Information of China (English)

    Jae-Ho LEE; Jeong-Hwan JANG; Byeong-Don JOO; Young-Myung SON; Young-Hoon MOON

    2009-01-01

    An attempt was made to improve the surface hardness and wear properties of AISI H13 tool steel through solid solution hardening and refinement of microstructures using a 200 W fiber laser as a heat generating source. The hardness of laser melted zone was investigated. In order to identify the effect of heat input on the laser melting zone, scanning conditions were controlled. The results show that, the hardness of as-received AISI H13 tool steel is approximately Hv 240, and the hardness after laser surface heat treatment is around Hv 480-510. The hardening depth and width are increased with the increase in the heat input applied. Application of experimental results will be considered in tooling industry.

  12. INVESTIGATION ON HARDENED STEEL MILLING WITH MICRO-END MILL

    Institute of Scientific and Technical Information of China (English)

    HUYing-ning; WANGCheng-yong; WUXue-qi; QINZhe; ZENGBao-ping

    2004-01-01

    Tool wear and breakage of the micro-milling tool is an important problem for high speed machining of hardened steel die and mould. Dry milling of S136 hardened steel is carried out using TiA1N coated carbide micro-end mill (Ф2 mm). The effect of cutting speed, feed per tooth and radial depth of cut on cutting force is analyzed. Cutting parameters adapting to dry machining and strategy optimized for higher rate of material removal with lower cutting force are attained. Results of SEM observation show that the main failure patterns of micro-end mill are breakage of tool tip, wear and drop-off of surface coating, micro-chipping, and breakage of flank.

  13. Investigation of the structure and properties of boron-containing coatings obtained by electron-beam treatment

    Energy Technology Data Exchange (ETDEWEB)

    Krivezhenko, Dina S., E-mail: dinylkaa@yandex.ru; Drobyaz, Ekaterina A., E-mail: ekaterina.drobyaz@yandex.ru; Bataev, Ivan A., E-mail: ivanbataev@ngs.ru; Chuchkova, Lyubov V., E-mail: twitty-kun@mail.ru [Novosibirsk State Technical University, Novosibirsk, 630073 (Russian Federation)

    2015-10-27

    An investigation of surface-hardened materials obtained by cladding with an electron beam injected into the air atmosphere was carried out. Structural investigations of coatings revealed that an increase in boron carbide concentration in a saturating mixture contributed to a rise of a volume fraction of iron borides in coatings. The maximum hardened depth reached 2 mm. Hardened layers were characterized by the formation of heterogeneous structure which consisted of iron borides and titanium carbides distributed uniformly in the eutectic matrix. Areas of titanium boride conglomerations were detected. It was found that an increase in the boron carbide content led to an enhancement in hardness of the investigated materials. Friction testing against loosely fixed abrasive particles showed that electron-beam cladding of powder mixtures containing boron carbides, titanium, and iron in air atmosphere allowed enhancing a resistance of materials hardened in two times.

  14. Investigation of the structure and properties of boron-containing coatings obtained by electron-beam treatment

    Science.gov (United States)

    Krivezhenko, Dina S.; Drobyaz, Ekaterina A.; Bataev, Ivan A.; Chuchkova, Lyubov V.

    2015-10-01

    An investigation of surface-hardened materials obtained by cladding with an electron beam injected into the air atmosphere was carried out. Structural investigations of coatings revealed that an increase in boron carbide concentration in a saturating mixture contributed to a rise of a volume fraction of iron borides in coatings. The maximum hardened depth reached 2 mm. Hardened layers were characterized by the formation of heterogeneous structure which consisted of iron borides and titanium carbides distributed uniformly in the eutectic matrix. Areas of titanium boride conglomerations were detected. It was found that an increase in the boron carbide content led to an enhancement in hardness of the investigated materials. Friction testing against loosely fixed abrasive particles showed that electron-beam cladding of powder mixtures containing boron carbides, titanium, and iron in air atmosphere allowed enhancing a resistance of materials hardened in two times.

  15. Control technology for surface treatment of materials using induction hardening

    Energy Technology Data Exchange (ETDEWEB)

    Kelley, J.B.; Skocypec, R.D. [Sandia National Labs., NM (United States)

    1997-04-01

    In the industrial and automotive industries, induction case hardening is widely used to provide enhanced strength, wear resistance, and toughness in components made from medium and high carbon steels. The process uses significantly less energy than competing batch process, is environmentally benign, and is a very flexible in-line manufacturing process. As such, it can directly contribute to improved component reliability, and the manufacture of high-performance lightweight parts. However, induction hardening is not as widely used as it could be. Input material and unexplained process variations produce significant variation in product case depth and quality. This necessitates frequent inspection of product quality by destructive examination, creates higher than desired scrap rates, and causes de-rating of load stress sensitive components. In addition, process and tooling development are experience-based activities, accomplished by trial and error. This inhibits the use of induction hardening for new applications, and the resultant increase in energy efficiency in the industrial sectors. In FY96, a Cooperative Research and Development Agreement under the auspices of the Technology Transfer Initiative and the Partnership for a New Generation of Vehicles was completed. A multidisciplinary team from Sandia National Labs and Delphi Saginaw Steering Systems investigated the induction hardening by conducting research in the areas of process characterization, computational modeling, materials characterization, and high speed data acquisition and controller development. The goal was to demonstrate the feasibility of closed-loop control for a specific material, geometry, and process. Delphi Steering estimated annual savings of $2-3 million per year due to reduced scrap losses, inspection costs, and machine down time if reliable closed-loop control could be achieved. A factor of five improvement in process precision was demonstrated and is now operational on the factory floor.

  16. Sequential circuit design for radiation hardened multiple voltage integrated circuits

    Science.gov (United States)

    Clark, Lawrence T.; McIver, III, John K.

    2009-11-24

    The present invention includes a radiation hardened sequential circuit, such as a bistable circuit, flip-flop or other suitable design that presents substantial immunity to ionizing radiation while simultaneously maintaining a low operating voltage. In one embodiment, the circuit includes a plurality of logic elements that operate on relatively low voltage, and a master and slave latches each having storage elements that operate on a relatively high voltage.

  17. Elastic constant versus temperature behavior of three hardened maraging steels

    Science.gov (United States)

    Ledbetter, H. M.; Austin, M. W.

    1985-01-01

    Elastic constants of three maraging steels were determined by measuring ultrasonic velocities. Annealed steels show slightly lower bulk moduli and considerably lower shear moduli than hardened steels. All the elastic constants (Young's modulus, shear modulus, bulk modulus and Poisson's ratio) show regular temperature behavior between 76 and 400 K. Young's modulus and the shear modulus increase with increasing yield strength, but the bulk modulus and Poisson's ratio are relatively unchanged. Elastic anisotropy is quite small.

  18. Steel phase transformants in the CO{sub 2} laser hardening process; Modelizacion de las transformaciones de fase en el proceso de endurecimiento de aceros con laser de CO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Amado, J. M.; Alvarez, C.; Nicolas, G.; Lopez, A. J.; Perez, J. A.; Ramil, A.; Saavedra, E.; Sanesteban, J.; Tobar, M. J.; Yanez, A.

    2004-07-01

    Hardening processes of steel are very dependent on the heating and cooling rates, in both cases high rates are needed. In the laser hardening the power density of the laser beam is responsible of the fast heating of the material; fast cooling is achieved due to the heat conduction from the region being treated to the bulk of the work piece. Within this work thermal cycles are determined with a Finite Element Model which computes the temperature of the material during the laser treatment. For the prediction of the hardening IT diagrams are applied, isothermal steps are connected with constant volume fraction steps; the content of each is computed in the framework of the Johnson-Mehl and Avrami law. During the cooling process, a similar procedure is applied but now using TTT diagrams. Model validation is done comparing, on a local basis, microhardness measurement on a treated work piece with the martensite concentration extracted from the model. (Author) 6 refs.

  19. Disaster-hardened imaging POD for PACS

    Science.gov (United States)

    Honeyman-Buck, Janice; Frost, Meryll

    2005-04-01

    After the events of 9/11, many people questioned their ability to keep critical services operational in the face of massive infrastructure failure. Hospitals increased their backup and recovery power, made plans for emergency water and food, and operated on a heightened alert awareness with more frequent disaster drills. In a film-based radiology department, if a portable X-ray unit, a CT unit, an Ultrasound unit, and an film processor could be operated on emergency power, a limited, but effective number of studies could be performed. However, in a digital department, there is a reliance on the network infrastructure to deliver images to viewing locations. The system developed for our institution uses several imaging PODS, a name we chose because it implied to us a safe, contained environment. Each POD is a stand-alone emergency powered network capable of generating images and displaying them in the POD or printing them to a DICOM printer. The technology we used to create a POD consists of a computer with dual network interface cards joining our private, local POD network, to the hospital network. In the case of an infrastructure failure, each POD can and does work independently to produce CTs, CRs, and Ultrasounds. The system has been tested during disaster drills and works correctly, producing images using equipment technologists are comfortable using with very few emergency switch-over tasks. Purpose: To provide imaging capabilities in the event of a natural or man-made disaster with infrastructure failure. Method: After the events of 9/11, many people questioned their ability to keep critical services operational in the face of massive infrastructure failure. Hospitals increased their backup and recovery power, made plans for emergency water and food, and operated on a heightened alert awareness with more frequent disaster drills. In a film-based radiology department, if a portable X-ray unit, a CT unit, an Ultrasound unit, and an film processor could be

  20. Precipitation hardening of biodegradable Fe-Mn-Pd alloys

    Energy Technology Data Exchange (ETDEWEB)

    Moszner, F. [Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland); Sologubenko, A.S. [Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland); Laboratory for Nanometallurgy, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland); Schinhammer, M. [Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland); Lerchbacher, C. [Christian Doppler Laboratory for Early Stages of Precipitation, University of Leoben, Franz-Josef-Strasse 18, 8700 Leoben (Austria); Haenzi, A.C. [Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland); Leitner, H. [Christian Doppler Laboratory for Early Stages of Precipitation, University of Leoben, Franz-Josef-Strasse 18, 8700 Leoben (Austria); Uggowitzer, P.J. [Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland); Loeffler, J.F., E-mail: joerg.loeffler@mat.ethz.ch [Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland)

    2011-02-15

    This work presents a phenomenological description of the precipitation controlled hardening of a new biodegradable Fe-based alloy developed to fulfill the requirements of temporary implant applications. Pronounced strengthening of the solution-treated martensitic Fe-10Mn-1Pd (in wt.%) alloy upon isothermal aging at temperatures within the ferrite-austenite phase field is observed and attributed to the thermally activated formation of coherent plate-like Pd-rich precipitates on {l_brace}1 0 0{r_brace} planes of the matrix. The onset and the early stages of alloy decomposition were studied using two complementary techniques: transmission electron microscopy and three-dimensional atom probe analysis. Three distinct regions of the hardening kinetics are recognized and closely correlated to the evolution of the alloy microstructure. Upon aging, clustering of Pd atoms within the Fe-Mn solid solution occurs. The very small clusters grow, coarsen and adopt a plate-like shape, rearranging mutually to reduce the overall elastic strain energy. The elastic interaction of the dislocation substructure with Pd-rich precipitates of evolving morphology affects the dislocation mobility and is responsible for the hardness evolution of the alloy. A study of the hardening kinetics shows that the process exhibits all the features characteristic of maraging steels.

  1. Residual stress analysis of drive shafts after induction hardening

    Energy Technology Data Exchange (ETDEWEB)

    Lemos, Guilherme Vieira Braga; Rocha, Alexandre da Silva; Nunes, Rafael Menezes, E-mail: lemos_gl@yahoo.com.br [Universidade Federal do Rio Grande do Sul (UFRS), Porto Algre, RS (Brazil); Hirsch, Thomas Karl [Stiftung Institut für Werkstofftechnik (IWT), Bremen (Germany)

    2014-08-15

    Typically, for automotive shafts, shape distortion manifests itself in most cases after the induction hardening by an effect known as bending. The distortion results in a boost of costs, especially due to machining parts in the hardened state to fabricate its final tolerances. In the present study, residual stress measurements were carried out on automotive drive shafts made of DIN 38B3 steel. The samples were selected in consequence of their different distortion properties by an industrial manufacturing line. One tested shaft was straightened, because of the considerable dimensional variation and the other one not. Firstly, the residual stress measurements were carried out by using a portable diffractometer, in order to avoid cutting the shafts and evaluate the original state of the stresses, and afterwards a more detailed analysis was realized by a conventional stationary diffractometer. The obtained results presented an overview of the surface residual stress profiles after induction hardening and displayed the influence of the straightening process on the redistribution of residual stresses. They also indicated that the effects of the straightening in the residual stresses cannot be neglected. (author)

  2. Study on the hardening mechanism of cement asphalt binder

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The hydration and hardening mechanism of cement asphalt binder(CAB) was studied.The early hydration process,hydration products and paste microstructure of CAB made by Portland cement and anionic asphalt emulsion were investigated by calorimetry,X-ray diffraction,and environmental scanning electron microscopy.The early hydration process of CAB can be characterized as 5 stages similar to those of Portland cement.There is no chemical reaction detected between cement and asphalt,hence no new hydration products other than those of Portland cement are produced.The hardening of CAB begins with the hydration of cement.When the hydration of cement comes into the acceleration period and its exothermic rate comes to the maximum,the coalescence of asphalt particles in asphalt emulsion is triggered.In the hardened system of CAB,it was found that the hydration products of cement form the skeleton and are covered by the continuous asphalt film.They formed an interpenetrating network system.The emulsifiers in the asphalt emulsion may retard the hydration process of cement.

  3. Press Hardening Steel (PHS): a new coating and process technology

    Energy Technology Data Exchange (ETDEWEB)

    Faderl, J. [voestalpine Stahl Linz GmbH (Austria); Vehof, R. [Polynorm N.V., Bundschoten (Netherlands)

    2005-07-01

    Press hardening technology has been known for many years. Increased requirements with respect to safety and light weight construction of the steel body for cars and trucks force the automotive industry to use high strength steels more and more. Strength levels up to 1000 MPa can be provided with AHSS grades. Above 1000 MPa, these steel grades are coming to their limit with respect to strength vs. formability balance. PHS is a very attractive alternative concept. Hardenable 22MnB5 has been supplied - uncoated - for a long time. To avoid decarburization during heat treatment and to improve corrosion behaviour hot dip aluminized 22MnB5 was introduced to the market. Both materials, uncoated and hot dip aluminized, do not provide cathodic corrosion protection without postcoating (sheradizing..). In the last two years an improved press hardening technology and a zinc based coating providing cathodic protection was developed by voestalpine. Some results about strength homogeneity, formability, corrosion behaviour of this voestalpine-PHS technology will be presented in the paper. (orig.)

  4. Recent developments in turning hardened steels - A review

    Science.gov (United States)

    Sivaraman, V.; Prakash, S.

    2017-05-01

    Hard materials ranging from HRC 45 - 68 such as hardened AISI H13, AISI 4340, AISI 52100, D2 STL, D3 STEEL Steel etc., need super hard tool materials to machine. Turning of these hard materials is termed as hard turning. Hard turning makes possible direct machining of the hard materials and also eliminates the lubricant requirement and thus favoring dry machining. Hard turning is a finish turning process and hence conventional grinding is not required. Development of the new advanced super hard tool materials such as ceramic inserts, Cubic Boron Nitride, Polycrystalline Cubic Boron Nitride etc. enabled the turning of these materials. PVD and CVD methods of coating have made easier the production of single and multi layered coated tool inserts. Coatings of TiN, TiAlN, TiC, Al2O3, AlCrN over cemented carbide inserts has lead to the machining of difficult to machine materials. Advancement in the process of hard machining paved way for better surface finish, long tool life, reduced tool wear, cutting force and cutting temperatures. Micro and Nano coated carbide inserts, nanocomposite coated PCBN inserts, micro and nano CBN coated carbide inserts and similar developments have made machining of hardened steels much easier and economical. In this paper, broad literature review on turning of hardened steels including optimizing process parameters, cooling requirements, different tool materials etc., are done.

  5. 球铁曲轴激光淬火强化技术研究%Study on the Laser Hardening Technology for a Crankshaft of Nodular Iron

    Institute of Scientific and Technical Information of China (English)

    周建忠; 花银群; 杨继昌; 张永康

    2001-01-01

    介绍了曲轴激光淬火强化系统,采用千瓦级快速轴流激光器对球铁曲轴进行了激光淬火强化试验,探讨了曲轴激光淬火强化时轴颈和圆角的激光扫描轨迹方式、功率密度及扫描速度等工艺参数对球铁激光强化性能的影响,指出了曲轴激光强化工程应用所要解决的主要问题。研究结果表明,球铁曲轴经激光淬火强化后,能获得较高的表面硬度和残余压应力,因而能有效的提高和改善曲轴的使用寿命。%The laser hardening system which used for crankshafts was introduced, and the investigation on the surface hardening of a nodular iron crankshaft was carried out by using a kW CO2 laser system. The key technologies, mechanism of strengthening, laser processes, as well as laser beam scanning pattern were analyzed. The effects of laser hardening processing parameters,such as power density, scanning speed, etc. on the properties of nodular iron hardening were studied. The results showed that under the condition of optimum process, high hardness and residual compressive stresses at the specimen surface were obtained so that the fatigue life of crankshafts could be improved. Finally, the key problem that affected engineering application of laser hardening for crankshafts was indicated.

  6. Optics measurement and correction during acceleration with beta-squeeze in RHIC

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Marusic, A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Minty, M. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2015-05-03

    In the past, beam optics correction at RHIC has only taken place at injection and at final energy, with interpolation of corrections partially into the acceleration cycle. Recent measurements of the beam optics during acceleration and squeeze have evidenced significant beta-beats that, if corrected, could minimize undesirable emittance dilutions and maximize the spin polarization of polarized proton beams by avoiding the high-order multipole fields sampled by particles within the bunch. We recently demonstrated successful beam optics corrections during acceleration at RHIC. We verified conclusively the superior control of the beam realized via these corrections

  7. The first experience with LHC beam gas ionization monitor

    CERN Document Server

    Sapinski, M; Dehning, B; Guerrero, A; Patecki, M; Versteegen, R

    2012-01-01

    The Beam Gas Ionization Monitors (BGI) are used to measure beam emittance on LHC. This paper describes the detectors and their operation and discusses the issues met during the commissioning. It also discusses the various calibration procedures used to correct for non-uniformity of Multi-Channel plates and to correct the beam size for effects affecting the electron trajectory after ionization.

  8. An Evaluation of the Corrosion and Mechanical Performance of Interstitially Surface-Hardened Stainless Steel

    Science.gov (United States)

    Jones, Jennifer L.; Koul, Michelle G.; Schubbe, Joel J.

    2014-06-01

    A surface hardening technique called "interstitial hardening" is commercially available, whereby interstitial carbon atoms are introduced into stainless steel surfaces without the formation of carbides. Surface hardening of machine elements such as impellors or fasteners would improve performance regarding cavitation and galling resistance, and has intensified interest in this process. However, there remains a need to characterize and validate the specific performance characteristics of the hardened materials. This paper describes experimental testing conducted on 316L stainless steel that has been surface hardened using available commercial techniques, using carbon as the interstitial atom. The corrosion performance of the hardened surface is assessed using electrochemical potentiodynamic testing to determine the breakdown potential in 3.5 wt.% NaCl solution to identify the most promising method. The hardness and thickness of the surface-hardened layer is characterized and compared using metallography and microhardness profiling. Corrosion fatigue and slow strain rate testing of untreated, hardened, and damaged, hardened surfaces exposed to ASTM seawater is conducted. Finally, critical galling stresses are determined and compared. Post-test examination of damage attempts to identify mechanisms of material failure and characterize how corrosion-assisted cracks initiate and grow in surface-hardened materials.

  9. The CERN Beam Interlock System: Principle and Operational Experience

    CERN Document Server

    Puccio, B; Kwiatkowski, M; Romera Ramirez, I; Todd, B

    2010-01-01

    A complex Machine Protection System has been designed to protect the LHC machine from an accidental release of the beam energy, with about 20 subsystems providing status information to the Beam Interlock System that is the backbone of machine protection. Only if the subsystems are in the correct state for beam operation, the Beam Interlock System receives a status flag and beam can be injected into LHC (Large Hadron Collider). The Beam Interlock System also relays commands from the connected subsystems in case of failure for triggering the LHC Beam Dumping System. To maintain the required level of safety of the Beam Interlock System, the performance of the key components is verified before every fill of the machine and validated after every emergency beam dump before beam operation is allowed to continue. This includes all critical paths, starting from the inputs from connected systems triggering a beam dump request, followed by the correct interruption and propagation sequence of the two redundant beam permi...

  10. Shear behavior of reinforced Engineered Cementitious Composites (ECC) beams

    DEFF Research Database (Denmark)

    Paegle, Ieva; Fischer, Gregor

    2010-01-01

    This paper describes an experimental investigation of the shear behavior of beams consisting of steel reinforced Engineered Cementitious Composites (ECC). Based on the strain hardening and multiple cracking behavior of ECC, this study investigates the extent to which ECC can improve the shear...... randomly distributed PVA (polyvinyl alcohol) fiber beams with different stirrup spacing and reinforced concrete (RC) beams for comparison. Displacement and strain measurements taken using the ARAMIS photogrammetric data acquisition system by means of processing at high frame rate captured images of applied...

  11. Radiation Hardening and Verification Procedure for Compact Flip-Flop Design

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Inyong; Sung, Seung Hwan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    For radiation-related applications applying electronic devices in nuclear, space, medicine, and scientific experiment, single event transients (SETs) and single event upsets (SEUs) are become primary concern since they can cause malfunctions in a system by affecting the signal transition and flipping digital bits. The D flip-flop as a register is generally used in digital circuits that require data stability and high speed. For many years, radiation-hardened-by-design (RHBD) circuits have been gradually developed from traditional circuit architectures. One of common methods is to exploit redundancy in an important circuit block to preserve the correct signal. This technique uses a voting process to have a correct output when other duplicated systems fail due to a single event effect (SEE) including SET and SEU. For instance, B. Olson applied the redundancy technique, formally referred the triple modular redundancy (TMR). Other researchers use various error detection and correction (EDAC) algorithms including redundant bits in the storage circuits to detect and correct errors at the system level. practical experiments at radiation exposure facilities. Korea Atomic Energy Research Institute (KAERI) operates a laboratory with high energy radioactive isotope, {sup 60}Co in Jeongeup, Korea. The facility can provide various experiments requiring experimental environment changes by controlling radiation activity and radiated energy. The future direction on RHBD circuits would be integration with the digital DFF presented in this paper and analog front-end units such as OP-amp for charge sensitive or shaping amplifier. Analog-to-digital converters (ADCs) are also major components necessarily imbedded in the most of sensor related electronics. Thus RHBD techniques are inevitably required to protect these circuits from SEE; specifically, SEUs for digital logics and SETs for analog signals. Since most ADCs consist of both analog and digital circuits in their architectures

  12. Improved impact toughness of 13Cr martensitic stainless steel hardened by laser

    Science.gov (United States)

    Tsay, L. W.; Chang, Y. M.; Torng, S.; Wu, H. C.

    2002-08-01

    The impact toughness of AISI 403 martensitic stainless steel plate and laser-hardened specimens tempered at various temperatures were examined. Phosphorus was the primary residual impurity responsible for tempered embrittlement of this alloy. The experimental result also indicated that AISI 403 stainless steel was very sensitive to reverse-temper embrittlement. The improved impact toughness of the laser-hardened specimen was attributed to the refined microstructure in the laser-hardened zone.

  13. Development of a Pressure-Dependent Constitutive Model with Combined Multilinear Kinematic and Isotropic Hardening

    Science.gov (United States)

    Allen Phillip A.; Wilson, Christopher D.

    2003-01-01

    The development of a pressure-dependent constitutive model with combined multilinear kinematic and isotropic hardening is presented. The constitutive model is developed using the ABAQUS user material subroutine (UMAT). First the pressure-dependent plasticity model is derived. Following this, the combined bilinear and combined multilinear hardening equations are developed for von Mises plasticity theory. The hardening rule equations are then modified to include pressure dependency. The method for implementing the new constitutive model into ABAQUS is given.

  14. The hardening compositions from the burnt rocks for using in the mining conditions

    Energy Technology Data Exchange (ETDEWEB)

    Galpern, E.I. [Inst. of Industrial Construction and Building, Donetsk, (Ukraine); Pashchenko, L.V.; Saranchuk, V.I. [Inst. of Physical, Organic and Coal Chemistry NAS, Donetsk (Ukraine)

    1997-12-31

    The complex investigation of burnt coal rocks as raw material for hardening alkaline cements reception have been carried out. The hardening composition on the base of pit heap burnt rocks for the grouting of worked-out space in mining conditions have been obtained. It has been shown that burnt rocks activation by blast granulated slag and water glass allowed to obtain the cements of needed strength. The influence of main technological factors on obtained hardening composition properties have been studied. (orig.)

  15. Electrolytic surface hardening of steel,cast iron and aluminium-bronze

    Institute of Scientific and Technical Information of China (English)

    Suhas Keshav Paknikar

    2006-01-01

    Electrolytic hardening process was developed in USSR in the 1950s. The process was developed but was not commercially exploited. There is no evidence of work done on this process in India. The author has done this original work applied to different materials like steel,cast iron and aluminum-bronze. This paper gives details of microstructural transformations along with hardness value achieved. There is vital scope for this process to become viable for surface hardening and selective hardening of small components.

  16. Multi-MGy Radiation Hardened Camera for Nuclear Facilities

    Energy Technology Data Exchange (ETDEWEB)

    Girard, Sylvain; Boukenter, Aziz; Ouerdane, Youcef [Universite de Saint-Etienne, Lab. Hubert Curien, UMR-CNRS 5516, F-42000 Saint-Etienne (France); Goiffon, Vincent; Corbiere, Franck; Rolando, Sebastien; Molina, Romain; Estribeau, Magali; Avon, Barbara; Magnan, Pierre [ISAE, Universite de Toulouse, F-31055 Toulouse (France); Paillet, Philippe; Duhamel, Olivier; Gaillardin, Marc; Raine, Melanie [CEA, DAM, DIF, F-91297 Arpajon (France)

    2015-07-01

    There is an increasing interest in developing cameras for surveillance systems to monitor nuclear facilities or nuclear waste storages. Particularly, for today's and the next generation of nuclear facilities increasing safety requirements consecutive to Fukushima Daiichi's disaster have to be considered. For some applications, radiation tolerance needs to overcome doses in the MGy(SiO{sub 2}) range whereas the most tolerant commercial or prototypes products based on solid state image sensors withstand doses up to few kGy. The objective of this work is to present the radiation hardening strategy developed by our research groups to enhance the tolerance to ionizing radiations of the various subparts of these imaging systems by working simultaneously at the component and system design levels. Developing radiation-hardened camera implies to combine several radiation-hardening strategies. In our case, we decided not to use the simplest one, the shielding approach. This approach is efficient but limits the camera miniaturization and is not compatible with its future integration in remote-handling or robotic systems. Then, the hardening-by-component strategy appears mandatory to avoid the failure of one of the camera subparts at doses lower than the MGy. Concerning the image sensor itself, the used technology is a CMOS Image Sensor (CIS) designed by ISAE team with custom pixel designs used to mitigate the total ionizing dose (TID) effects that occur well below the MGy range in classical image sensors (e.g. Charge Coupled Devices (CCD), Charge Injection Devices (CID) and classical Active Pixel Sensors (APS)), such as the complete loss of functionality, the dark current increase and the gain drop. We'll present at the conference a comparative study between these radiation-hardened pixel radiation responses with respect to conventional ones, demonstrating the efficiency of the choices made. The targeted strategy to develop the complete radiation hard camera

  17. Design and characterization of a dedicated cone-beam CT scanner for detection of acute intracranial hemorrhage

    Science.gov (United States)

    Xu, J.; Sisniega, A.; Zbijewski, W.; Dang, H.; Stayman, J. W.; Wang, X.; Foos, D. H.; Aygun, N.; Koliatsos, V. E.; Siewerdsen, J. H.

    2016-03-01

    Purpose: Prompt and reliable detection of intracranial hemorrhage (ICH) has substantial clinical impact in diagnosis and treatment of stroke and traumatic brain injury. This paper describes the design, development, and preliminary performance characterization of a dedicated cone-beam CT (CBCT) head scanner prototype for imaging of acute ICH. Methods: A task-based image quality model was used to analyze the detectability index as a function of system configuration, and hardware design was guided by the results of this model-based optimization. A robust artifact correction pipeline was developed using GPU-accelerated Monte Carlo (MC) scatter simulation, beam hardening corrections, detector veiling glare, and lag deconvolution. An iterative penalized weighted least-squares (PWLS) reconstruction framework with weights adjusted for artifact-corrected projections was developed. Various bowtie filters were investigated for potential dose and image quality benefits, with a MC-based tool providing estimates of spatial dose distribution. Results: The initial prototype will feature a source-detector distance of 1000 mm and source-axis distance of 550 mm, a 43x43 cm2 flat panel detector, and a 15° rotating anode x-ray source with 15 kW power and 0.6 focal spot size. Artifact correction reduced image nonuniformity by ~250 HU, and PWLS reconstruction with modified weights improved the contrast to noise ratio by 20%. Inclusion of a bowtie filter can potentially reduce dose by 50% and improve CNR by 25%. Conclusions: A dedicated CBCT system capable of imaging millimeter-scale acute ICH was designed. Preliminary findings support feasibility of point-of-care applications in TBI and stroke imaging, with clinical studies beginning on a prototype.

  18. Precipitation hardening in Fe--Ni base austenitic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Chang, K.M.

    1979-05-01

    The precipitation of metastable Ni/sub 3/X phases in the austenitic Fe--Ni-base alloys has been investigated by using various combinations of hardening elements, including Ti, Ta, Al, and Nb. The theoretical background on the formation of transition precipitates has been summarized based on: atomic size, compressibility, and electron/atom ratio. A model is proposed from an analysis of static concentration waves ordering the fcc lattice. Ordered structure of metastable precipitates will change from the triangularly ordered ..gamma..', to the rectangularly ordered ..gamma..'', as the atomic ratio (Ti + Al)/(Ta + Nb) decreases. The concurrent precipitation of ..gamma..' and ..gamma..'' occurs at 750/sup 0/C when the ratio is between 1.5 and 1.9. Aging behavior was studied over the temperature range of 500/sup 0/C to 900/sup 0/C. Typical hardness curves show a substantial hardening effect due to precipitation. A combination of strength and fracture toughness can be developed by employing double aging techniques. The growth of these coherent intermediate precipitates follows the power law with the aging time t : t/sup 1/3/ for the spherical ..gamma..' particles; and t/sup 1/2/ for the disc-shaped ..gamma..''. The equilibrium ..beta.. phase is observed to be able to nucleate on the surface of imbedded carbides. The addition of 5 wt % Cr to the age-hardened alloys provides a non-magnetic austenite which is stable against the formation of mechanically induced martensite.Cr addition retards aging kinetics of the precipitation reactions, and suppresses intergranular embrittlement caused by the high temperature solution anneal. The aging kinetics are also found to be influenced by solution annealing treatments.

  19. Effect of hardening method and structure of linking bridges on strength of water glass moulding sands

    OpenAIRE

    Stachowicz, M.; K. Granat

    2010-01-01

    The paper presents examination results of the effect of four hardening methods on structure of linking bridges in sandmixes containing hydrated sodium silicate. Test pieces prepared of the moulding sands containing 2.5 % of a binder with molar module between 2.4 and 2.6 were hardened with carbon dioxide, dried traditionally in an oven and hardened with microwaves at 2.54 GHz or using a combination of the CO2 process and microwave heating. It was revealed that the hardening method influences s...

  20. Optimizing the Thermal Regime During the Acceleration of Concrete’s Hardening

    Directory of Open Access Journals (Sweden)

    Vladimir Corobceanu

    2007-01-01

    Full Text Available Researches conducted at the Faculty of Construction in Jassy showed several factors that may help finding technical solutions which will make possible to economically apply acceleration procedures of concrete hardening by thermal treatment with solar energy. It has to be mentioned the fact that the thermal treatment do not exclude, but it is based on the acceleration methods of concrete hardening through composition with or without the usage of different additives -- plasticizer type (to reduce the quantity of water from the concrete and accelerators for cement binding or hardening. These methods also take into account the climate where the process of hardening takes place.

  1. Radiation-Hardened Memristor-based Memory for Extreme Environments Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA space exploration missions require radiation-hardened memory technologies that can survive and operate over a wide temperature range. Memristors...

  2. Effect of dynamic strain aging on isotropic hardening in low cycle fatigue for carbon manganese steel

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Zhi Yong, E-mail: huangzy@scu.edu.cn [Sichuan University, School of Aeronautics and Astronautics, No. 29 Jiuyanqiao Wangjiang Road, Chengdu 610064 (China); Chaboche, Jean-Louis [ONERA, DMSM, 29 avenue de la Division Lecerc, F-92320 Chatillon (France); Wang, Qing Yuan [Sichuan University, School of Aeronautics and Astronautics, No. 29 Jiuyanqiao Wangjiang Road, Chengdu 610064 (China); Wagner, Danièle; Bathias, Claude [Université ParisOuest Nanterre La Défense (France)

    2014-01-01

    Carbon–manganese steel A48 (French standard) is used in steam generator pipes of nuclear reactor pressure vessels at high temperatures (about 200 °C). The steel is sensitive to dynamic strain aging in monotonic tensile test and low cycle fatigue test at certain temperature range and strain rate. Its isotropic hardening behavior observed from experiments has a hardening, softening and hardening evolution with the effect of dynamic strain aging. The isotropic hardening model is improved by coupling the dislocation and dynamic strain aging theory to describe the behavior of A48 at 200 °C.

  3. Hardening mechanisms in a dynamic strain aging alloy, Hastelloy X, during isothermal and thermomechanical cyclic deformation

    Science.gov (United States)

    Miner, R. V.; Castelli, M. G.

    1992-01-01

    The relative contributions of the hardening mechanisms in Hastelloy X during cyclic deformation were investigated by conducting isothermal cyclic deformation tests within a total strain range of +/-0.3 pct and at several temperatures and strain rates, and thermomechanical tests within several different temperature limits. The results of the TEM examinations and special constant structure tests showed that the precipitation on dislocations of Cr23C6 contributed to hardening, but only after sufficient time above 500 C. Solute drag alone produced very considerable cyclic hardening. Heat dislocation densities, peaking around 10 exp 11 per sq cm, were found to develop at temperatures producing the greatest cyclic hardening.

  4. A new ester hardener for moulding sands with water glass having slower activity

    Directory of Open Access Journals (Sweden)

    K. Major-Gabryś

    2009-10-01

    Full Text Available The article takes into consideration the researches concerning inputting the new hardener to moulding sands with water glass, carried out in ester technology. Investigations are continuation of works connected to hardener based on carbonic acid’s esters, that significantly upgrades the ability of these moulding sands to mechanical reclamation. Its’ nuisance is short vitality. This is why, new investigations were taken to elaborate another hardener keeping the positive characteristics of the previous one and allowing the wider usage of technologies of loose self-hardened moulding sands with water glass.

  5. Development of a Flexible Laser Hardening & Machining Center and Proof of Concept on C-45 Steel

    Science.gov (United States)

    Bouquet, Jan; Van Camp, Dries; Vanhove, Hans; Clijsters, Stijn; Amirahmad, Mohammadi; Lauwers, Bert

    The production of hardened precision parts is conventionally done in 3 steps. Rough machining of a workpiece in soft stage is followed by a hardening step, usually a batch process, and finalized by a hard machining finishing step. To omit the inevitable time delay and loss of accuracy because of part re-clamping, these steps should be incorporated within one flexible machining center. This paper describes the development of this machining center which allowsmachining and laser hardening in one setup, followed by a proof of concept for hardening C45 steel on this setup.

  6. Rationale simplified hardening training and recreational complexes future teachers

    Directory of Open Access Journals (Sweden)

    Verbludov I.B.

    2010-02-01

    Full Text Available Distribution in the modern world epidemiological diseases are influenza and acute respiratory viral infections requires a search for simplified, effective preventive means. The main direction of prevention of these diseases is to strengthen and enhance the activities of the immune system. Strengthening the protective systems of the body is directly related to the constant holding of different types of hardening. This study illustrates the possibility of using quenching air and water in the independent exercise training and recreational facilities in all conditions of students.

  7. Bake hardening behavior of TRIP and DP steels

    Institute of Scientific and Technical Information of China (English)

    Jicheng Zhang; Renyu Fu; Mei Zhang; Rendong Liu; Xicheng Wei; Lin Li

    2008-01-01

    The bake hardening (BH) behavior of transformation-induced plasticity (TRIP) and dual-phase (DP) steels after different prestrains was studied. The experimental results indicate that TRIP steel exhibits good BH ability while DP steel does not, and prestrain displays a strong effect on the BH values of both steels. The comparison of microstructures of the two steels showed that the hard second phase in the matrix might be harmful to the BH ability. For deformed specimens, baking resulted in a loss of uniform elongation, but there was no obvious decrease in uniform elongation for unprestrained specimens.

  8. The development of radiation hardened robot for nuclear facility

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seung Ho; Jung, Seung Ho; Kim, Byung Soo and others

    2000-04-01

    The work conducted in this stage covers development of core technology of tele-robot system including monitoring technique in high-level radioactive area, tele-sensing technology and radiation-hardened technology for the non-destructive tele-inspection system which monitors the primary coolant system during the normal operations of PHWR(Pressurized Heavy Water Reactor) NPPs and measures the decrease of bending part of feeder pipe during overall. Based on the developed core technology, the monitoring mobile robot system of the primary coolant system and the feeder pipe inspecting robot system are developed.

  9. New Stainless Steel Alloys for Low Temperature Surface Hardening?

    DEFF Research Database (Denmark)

    Christiansen, Thomas Lundin; Dahl, Kristian Vinter; Somers, Marcel A. J.

    2015-01-01

    The present contribution showcases the possibility for developing new surface hardenable stainless steels containing strong nitride/carbide forming elements (SNCFE). Nitriding of the commercial alloys, austenitic A286, and ferritic AISI 409 illustrates the beneficial effect of having SNCFE present...... in the stainless steel alloys. The presented computational approach for alloy design enables “screening” of hundreds of thousands hypothetical alloy systems by use of Thermo-Calc. Promising compositions for new stainless steel alloys can be selected based on imposed criteria, i.e. facilitating easy selection...

  10. Fatigue Hardening and Nucleation of Persistent Slip Bands in Copper

    DEFF Research Database (Denmark)

    Pedersen, Ole Bøcker; Winter, A. T.

    1982-01-01

    that there is a large volume fraction of obstacles to plastic flow which are essentially non-deformable and give rise to inclusion stresses of considerable magnitude. The much lower hardening rates in cycles after saturation when persistent slip bands have formed suggest a lower volume fraction of obstacles......, as is observed by transmission electron microscopy. A simple composite model involving an inclusion stress, a bowing stress and a passing, stress accounts for the workhardening rates semi-quantitatively in terms of observed dislocation microstructures. Possible implications for polycrystals are considered....

  11. Thermomechanical hardening of stable and metastable austenitic steels

    Science.gov (United States)

    Baraz, V. R.; Gladkovskii, S. V.; Ishina, E. A.

    2005-11-01

    Phase composition, mechanical properties, and variation of the density of cold-deformed Fe-Cr-Ni-Mn steels differing in the stability of austenite are studied. A comparative analysis of formation of phase composition and accumulation of discontinuities in the process of drawing of stable and metastable austenitic steels is performed. The effect of post-deformation annealing on the variation of the density and mechanical properties is considered. The capacity for recovery of the density is shown to be correlated with the resistance of the studied thermomechanically hardened steels to fatigue fracture. The determined dependences are explained.

  12. Ferroelectric memories: A possible answer to the hardened nonvolatile question

    Energy Technology Data Exchange (ETDEWEB)

    Messenger, G.C.; Coppage, F.N.

    1988-12-01

    Ferroelectric memory cells have been fabricated using a process compatible with semiconductor VLSI (Very Large-Scale Integration) manufacturing techniques which are basically nonvolatile and radiation hard. The memory can be made NDRO (Nondestructive Readout) for strategic systems using several techniques; the most practical is probably a rapid read/restore in combination with EDAC software. This memory can replace plated wire and will have substantial advantages in cost, weight, size, power and speed. It provides a practical cost-competitive solution to the need for nonvolatile RAM in all hardened tactical, avionic, and space systems.

  13. Interaction between alloying and hardening of cast iron surface

    Institute of Scientific and Technical Information of China (English)

    刘政军; 郝雪枫; 傅迎庆; 牟力军

    2002-01-01

    To improve wear resistance of surface will increase the service life of gray cast iron directly. This paper presents that gray cast iron surface coated with alloy powder is locally remelted by TIG arc to increase the wear resistance. The influences of arc current and scanning rate etc on surface properties are found. Under different conditions, the microstructure, hardness and wear resistance of remelted layer are analyzed and measured. The results indicate that the gray cast iron surface can be strengthened by TIG arc local remelting treatment. Especially, surface alloying hardening effect is best and surface properties are improved remarkably.

  14. Sensitivity studies of beam directionality, beam size, and neutron spectrum for a fission converter-based epithermal neutron beam for boron neutron capture therapy.

    Science.gov (United States)

    Sakamoto, S; Kiger, W S; Harling, O K

    1999-09-01

    Sensitivity studies of epithermal neutron beam performance in boron neutron capture therapy are presented for realistic neutron beams with varying filter/moderator and collimator/delimiter designs to examine the relative importance of neutron beam spectrum, directionality, and size. Figures of merit for in-air and in-phantom beam performance are calculated via the Monte Carlo technique for different well-optimized designs of a fission converter-based epithermal neutron beam with head phantoms as the irradiation target. It is shown that increasing J/phi, a measure of beam directionality, does not always lead to corresponding monotonic improvements in beam performance. Due to the relatively low significance, for most configurations, of its effect on in-phantom performance and the large intensity losses required to produce beams with very high J/phi, beam directionality should not be considered an important figure of merit in epithermal neutron beam design except in terms of its consequences on patient positioning and collateral dose. Hardening the epithermal beam spectrum, while maintaining the specific fast neutron dose well below the inherent hydrogen capture dose, improves beam penetration and advantage depth and, as a desirable by-product, significantly increases beam intensity. Beam figures of merit are shown to be strongly dependent on beam size relative to target size. Beam designs with J/phi approximately 0.65-0.7, specific fast neutron doses of 2-2.6x10(-13) Gy cm2/n and beam sizes equal to or larger than the size of the head target produced the deepest useful penetration, highest therapeutic ratios, and highest intensities.

  15. Prediction of beam hardening artefacts in computed tomography using Monte Carlo simulations

    DEFF Research Database (Denmark)

    Thomsen, M.; Bergbäck Knudsen, Erik; Willendrup, Peter Kjær

    2015-01-01

    We show how radiological images of both single and multi material samples can be simulated using the Monte Carlo simulation tool McXtrace and how these images can be used to make a three dimensional reconstruction. Good numerical agreement between the X-ray attenuation coefficient in experimental......, illustrated with an example. Linearisation requires knowledge about the X-ray transmission at varying sample thickness, but in some cases homogeneous calibration phantoms are hard to manufacture, which affects the accuracy of the calibration. Using simulated data overcomes the manufacturing problems...

  16. Miniaturized Radiation Hardened Beam-Steerable GPS Receiver Front End Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA is seeking proposals for innovative research in the areas of on-orbit positioning, navigation, and timing (PNT). Tahoe RF is proposing to build a fully...

  17. Simulation-aided investigation of beam hardening induced errors in CT dimensional metrology

    DEFF Research Database (Denmark)

    Tan, Ye; Kiekens, Kim; Welkenhuyzen, Frank;

    2014-01-01

    Industrial x-ray computed tomography (CT) systems are being increasingly used as dimensional measuring machines. However, micron level accuracy is not always achievable, as of yet. The measurement accuracy is influenced by many factors, such as the workpiece properties, x-ray voltage, filter, bea...

  18. Miniaturized Radiation Hardened Beam-Steerable GPS Receiver Front End Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Position, Navigation and Timing (PNT) capability via GPS services are used by NASA for (1) real-time on-board autonomous navigation, (2) attitude determination and...

  19. Recommended values of the humidity correction factor k{sub n} for determining exposure in an X-ray beam with free-air chambers; Valores recomendados del factor de correccion por humedad, k{sub h} para la determinacion de la exposicion en un haz de rayos X usando camaras de paredes de aire

    Energy Technology Data Exchange (ETDEWEB)

    Los Arcos, J.M.; Brosed, A.

    1983-07-01

    The experimental values stated by CCEMRI (Section I) concerning the humidity correction factor k{sub h} required for determining exposure in an X-ray beam with free-air chambers are commented and a method to estimate k{sub n} numerically, at any particular combination of relative humidity, pressure and temperature, la explained. A table of k{sub h}, calculated for relative humidity varying from 0% to 90%, for pressures in the range of 70 kPa to 104kPa and temperatures between 15 degree centigree and 30 degree centigree, is included. (Author) 10 refs.

  20. Applications of Crank-Nicolson method with ADI in laser transformation hardening

    Science.gov (United States)

    Kartono, Agus; Tofany, Novan; Ahmad, Mohammad Fadhli; Mamat, Mustafa; Husain, Mohd Lokman

    2012-12-01

    A two-dimensional numerical solution for pulsed laser transformation hardening is developed using the finite difference method (FDM). The FDM has been developed using Crank-Nicolson scheme which solved by using alternating-direction implicit method. If this present model was compared to the analytical solution, then the Crank-Nicolson scheme showed better results in terms of accuracy, consistency, stability, convergence, and performance than to the explicit scheme. The longer heating duration, higher laser beam intensity, and greater number of pulse had influences on increasing the maximum temperature. The repetitive heating had influences on extending the heat duration and increasing the initial temperature of domain. The shorter cooling duration in repetitive pulse produced higher maximum temperature. The thinner material's thickness increased the cooling rate, which finally increased the possibility of austenite to transform into martensite phase. In addition, it was also found that the higher maximum temperature always reduced the cooling rate value when temperature cools down toward to the starting temperature of martensite formation. It reduced the possibility of martensite formation. It was also seen that the heat was conducted more effective to the axial direction than to the radial direction.

  1. Hardening of Thermal Photons Through Inverse Compton Scattering in Strong Magnetic Fields

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A new spectrum function is obtained by use of the Compton scattering cross section in the laboratory frame derived earlier. This spectrum function, besides some modifications in the coefficients of the resonant term, contains also a non-resonant term which is inversely proportional to the square of the magnetic field. Based on this spectrum function, the hardening of thermal photons through inverse Compton scattering by relativistic electron beams on the surface of a strongly magnetized neutron star is investigated. Two new features are found. First, there is a maximum scattered photon energy for a given resonant scattering, beyond which resonance disappears. This maximum depends on the electron energy and the magnetic field, but is independent of the incident photon energy. Second, beyond each resonant scattering, there is a high-energy tail, resulting from non-resonant scattering. It is also found that all the tails have a common upper limit which is the highest scattered photon energy for the given incident photon and electron energies. These two new features are absent in the Monte Carlo simulations and therefore, may have physical implications for γγ-ray emissions.

  2. Influence of Plastic Deformation on Low Temperature Surface Hardening of Austenitic and Precipitation Hardening Stainless Steels by Gaseous Nitriding

    DEFF Research Database (Denmark)

    Bottoli, Federico; Winther, Grethe; Christiansen, Thomas Lundin

    2015-01-01

    This article addresses an investigation of the influence of plastic deformation on low temperature surface hardening by gaseous nitriding of three commercial austenitic stainless steels: AISI 304, EN 1.4369 and Sandvik Nanoflex® with various degrees of austenite stability. The materials were...... plastically deformed to different equivalent strains by uniaxial tension. Gaseous nitriding of the strained material was performed in ammonia gas at atmospheric pressure at 703 K (430 °C) and 693 K (420 °C) depending on the material. Microstructural characterization of the as-deformed states and the nitrided...

  3. A model for quantitative correction of coronary calcium scores on multidetector, dual source, and electron beam computed tomography for influences of linear motion, calcification density, and temporal resolution : A cardiac phantom study

    NARCIS (Netherlands)

    Greuter, M. J. W.; Groen, J. M.; Nicolai, L. J.; Dijkstra, H.; Oudkerk, M.

    2009-01-01

    Purpose: The objective of this study is to quantify the influence of linear motion, calcification density, and temporal resolution on coronary calcium determination using multidetector computed tomography (MDCT), dual source CT (DSCT), and electron beam tomography (EBT) and to find a quantitative me

  4. Implicit numerical integration for a kinematic hardening soil plasticity model

    Science.gov (United States)

    Rouainia, M.; Muir Wood, D.

    2001-11-01

    Soil models based on kinematic hardening together with elements of bounding surface plasticity, provide a means of introducing some memory of recent history and stiffness variation in the predicted response of soils. Such models provide an improvement on simple elasto-plastic models in describing soil behaviour under non-monotonic loading. Routine use of such models requires robust numerical integration schemes. Explicit integration of highly non-linear models requires extremely small steps in order to guarantee convergence. Here, a fully implicit scheme is presented for a simple kinematic hardening extension of the Cam clay soil model. The algorithm is based on the operator split methodology and the implicit Euler backward integration scheme is proposed to integrate the rate form of the constitutive relations. This algorithm maintains a quadratic rate of asymptotic convergence when used with a Newton-Raphson iterative procedure. Various strain-driven axisymmetric triaxial paths are simulated in order to demonstrate the efficiency and good performance of the proposed algorithm.

  5. Phase transformations in titanium alloys hardened by rapid heating

    Energy Technology Data Exchange (ETDEWEB)

    Gridnev, V.N.; Ivasishin, O.M.; Oshkaderov, S.P.; Smirnov, A.M. (AN Ukrainskoj SSR, Kiev. Inst. Metallofiziki)

    Features of phase transformations in titanium alloys, which subjected to hardening by rapid heating, are studied. The model for mathematical description of ..cap alpha..+..beta.. ..-->.. ..beta..- transformation under the conditions of continuous heating with different rate, is proposed. The increase of the polymorphic transformation temperature with the heating rate, is predicted and confirmed experimentally. Under certain conditions this fact can result in a two-stage process, of ..cap alpha..+..beta.. ..-->.. ..beta..-transformation, which begins according to difussion mechanism, and completes according to the non-diffusion one. It is shown, that ..cap alpha..+..beta.. ..-->.. ..beta..-transformation under non-equilibrium conditions is followed by appearing of concentration non-uniformity in reacting phases, that essentially affects the grain and intragranular structure of hardened alloys, and their phase composition. Variants of phase composition of the alloys of different classes quenched after rapid heating in the ..beta..-field, are analyzed. Possible aspects of the effect of increased heating rates on the ageing process are considered.

  6. Folding and faulting of strain-hardening sedimentary rocks

    Science.gov (United States)

    Johnson, A.M.

    1980-01-01

    The question of whether single- or multi-layers of sedimentary rocks will fault or fold when subjected to layer-parallel shortening is investigated by means of the theory of elastic-plastic, strain-hardening materials, which should closely describe the properties of sedimentary rocks at high levels in the Earth's crust. The most attractive feature of the theory is that folding and faulting, intimately related in nature, are different responses of the same idealized material to different conditions. When single-layers of sedimentary rock behave much as strain-hardening materials they are unlikely to fold, rather they tend to fault, because contrasts in elasticity and strength properties of sedimentary rocks are low. Amplifications of folds in such materials are negligible whether contacts between layer and media are bonded or free to slip for single layers of dolomite, limestone, sandstone, or siltstone in media of shale. Multilayers of these same rocks fault rather than fold if contacts are bonded, but they fold readily if contacts between layers are frictionless, or have low yield strengths, for example due to high pore-water pressure. Faults may accompany the folds, occurring where compression is increased in cores of folds. Where there is predominant reverse faulting in sedimentary sequences, there probably were few structural units. ?? 1980.

  7. Discrepant hardening observed in cosmic-ray elemental spectra

    CERN Document Server

    Ahn, H S; Bagliesi, M G; Beatty, J J; Bigongiari, G; Childers, J T; Conklin, N B; Coutu, S; DuVernois, M A; Ganel, O; Han, J H; Jeon, J A; Kim, K C; Lee, M H; Lutz, L; Maestro, P; Malinin, A; Marrocchesi, P S; Minnick, S; Mognet, S I; Nam, J; Nam, S; Nutter, S L; Park, I H; Park, N H; Seo, E S; Sina, R; Wu, J; Yang, J; Yoon, Y S; Zei, R; Zinn, S Y; 10.1088/2041-8205/714/1/L89

    2010-01-01

    The balloon-borne Cosmic Ray Energetics And Mass (CREAM) experiment launched five times from Antarctica has achieved a cumulative flight duration of about 156 days above 99.5% of the atmosphere. The instrument is configured with complementary and redundant particle detectors designed to extend direct measurements of cosmic-ray composition to the highest energies practical with balloon flights. All elements from protons to iron nuclei are separated with excellent charge resolution. Here we report results from the first two flights of ~70 days, which indicate hardening of the elemental spectra above ~200 GeV/nucleon and a spectral difference between the two most abundant species, protons and helium nuclei. These results challenge the view that cosmic-ray spectra are simple power laws below the so-called knee at ~1015 eV. This discrepant hardening may result from a relatively nearby source, or it could represent spectral concavity caused by interactions of cosmic rays with the accelerating shock. Other possible ...

  8. Dislocation Starvation and Exhaustion Hardening in Mo-alloy Nanofibers

    Energy Technology Data Exchange (ETDEWEB)

    Chisholm, Claire [University of California, Berkeley & LBNL; Bei, Hongbin [ORNL; Lowry, M. B. [University of California, Berkeley; Oh, Jason [Hysitron, Inc., MN; Asif, S.A. Syed [Hysitron, Inc., MN; Warren, O. [Hysitron, Inc., MN; Shan, Zhiwei [Xi' an Jiaotong University, China & Hysitron, Inc., MN; George, Easo P [ORNL; Minor, Andrew [University of California, Berkeley & LBNL

    2012-01-01

    The evolution of defects in Mo alloy nanofibers with initial dislocation densities ranging from 0 to 1.6 1014 m2 were studied using an in situ push-to-pull device in conjunction with a nanoindenter in a transmission electron microscope. Digital image correlation was used to determine stress and strain in local areas of deformation. When they had no initial dislocations the Mo alloy nanofibers suffered sudden catastrophic elongation following elastic deformation to ultrahigh stresses. At the other extreme fibers with a high dislocation density underwent sustained homogeneous deformation after yielding at much lower stresses. Between these two extremes nanofibers with intermediate dislocation densities demonstrated a clear exhaustion hardening behavior, where the progressive exhaustion of dislocations and dislocation sources increases the stress required to drive plasticity. This is consistent with the idea that mechanical size effects ( smaller is stronger ) are due to the fact that nanostructures usually have fewer defects that can operate at lower stresses. By monitoring the evolution of stress locally we find that exhaustion hardening causes the stress in the nanofibers to surpass the critical stress predicted for self-multiplication, supporting a plasticity mechanism that has been hypothesized to account for the rapid strain softening observed in nanoscale bcc materials at high stresses.

  9. Microstructural aspects and wear behavior of sinter hardened distaloy HP

    Energy Technology Data Exchange (ETDEWEB)

    Sheikhi Moghaddam, K.; Ghambari, M.; Farhangi, H. [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran (Iran, Islamic Republic of); Solimanjad, N.; Bergmark, A. [Hoeganaes AB, Bruksgatan, Hoeganaes (Sweden); Khorsand, H. [K.N. Toosi University, Tehran (Iran, Islamic Republic of)

    2011-11-15

    Effect of cooling rate during sinter hardening on the microstructure and wear behavior of sintered steel grade Distaloy HP has been studied. Wear performances are closely related to macro and micro hardness of the materials. Dry sliding wear tests have been conducted using a reciprocating pin on flat wear testing machine under normal loads of 25, 35 and 45N and at a constant speed of 0.3 m/s. The samples were sinter hardened at different cooling rates 0.5-3 C/s in order to investigate the influence of microstructure and hardness on wear behavior. It has been shown that, sintering process and cooling rate change the microstructure and hence the hardness and wear behavior of the material. The best wear resistance was detected at a cooling rate of 3 C/s. At this cooling rate the material had an almost martensitic microstructure and the wear rate was some how independent of the applied load. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. FATIGUE LIVES FOR INDUCTION HARDENED SHAFTS MATERIALS ACCORDING TO THE ENVIRONMENTAL TEMPERATURES

    Institute of Scientific and Technical Information of China (English)

    D.G. Lee; K.C.Jang; J.M. Kuk; I.S. Kim

    2005-01-01

    Rotary bending fatigue tests were carried out with two kinds of materials, S43C and S50C, using the front engine and front drive shaft (FF shaft) of vehicle. The specimens were induction hardened about 1.0mm depth from the specimen surface, and the hardness value on the surface was about HRC56-60. The tested environment temperatures were -30, 25 and 80℃ in order to look over effect of the induction hardening and the environmental temperatures on the fatigue characteristics. The fatigue limit of induction hardened specimens increased more about 45%than non-hardened specimens showing that the endurances of S43C and S50C were 98.1 and 107.9MPa in non-hardened samples, 147.1 and 156.9MPa in hardened samplesrespectably. The maximum tensile and compressive stress on the small circular defect was about +250 and -450MPa respectively when circular defect is situated on top and bottom. The fatigue life increased 80, 25and -30℃ in order regardless of hardening. In comparison of the fatigue lives on the basis of tested result at 25℃, the fatigue lives of non-hardened specimens decreased about 35%, but that of hardened specimens decreased about only 5% at 80℃ more than at 25℃. And fatigue life of non-hardened and hardened specimens were about 110% and 120% higher at -30℃ than that of 25℃. Based on the result of stress distribution near the defect, the tensile and compressive stress repeatedly generated by load direction were the largest on the small circular defect due to the stress concentration.

  11. 采用感应预热的连续激光淬火%Continuous Laser Hardening with Induction Pre-Heating

    Institute of Scientific and Technical Information of China (English)

    I Doležel; V.Kotlan; R.Hamar; D.Pánek

    2015-01-01

    A novel way of continuous surface hardening of steel bodies by a laser beam is modeled.This heat treatment is supplemented with pre-heating of the hardened parts by a classic inductor in order to reduce the temperature gradients and subsequent mechanical stresses in the processed material.The mathematical model of the process is solved numerically in 3D and the solution respects all important nonlinearities (a saturation curve of the hardened steel and temperature dependences of its physical properties).The methodology is illustrated with a typical example,whose results are presented and discussed.%模拟了钢件采用激光束进行表面连续淬火的新方法。这种热处理方法采用传统的感应器对淬火零件进行预热,以便减小温度梯度及随后产生的被处理材料的机械应力。该工艺的数学模型采用3D数值建立,其解法考虑了所有重要的非线性特性(被淬火钢的磁饱和曲线及其物理性能与温度的关系)。用典型的实例进行了说明,介绍了结果并进行了讨论。

  12. Nonlinearities and effects of transverse beam size in beam position monitors

    Science.gov (United States)

    Kurennoy, Sergey S.

    2001-09-01

    The fields produced by a long beam with a given transverse charge distribution in a homogeneous vacuum chamber are studied. Signals induced by a displaced finite-size beam on electrodes of a beam position monitor (BPM) are calculated and compared to those produced by a pencil beam. The nonlinearities and corrections to BPM signals due to a finite transverse beam size are calculated for an arbitrary chamber cross section. Simple analytical expressions are given for a few particular transverse distributions of the beam current in a circular or rectangular chamber. Of particular interest is a general proof that in an arbitrary homogeneous chamber the beam-size corrections vanish for any axisymmetric beam current distribution.

  13. Nonlinearities and effects of transverse beam size in beam position monitors

    Directory of Open Access Journals (Sweden)

    Sergey S. Kurennoy

    2001-09-01

    Full Text Available The fields produced by a long beam with a given transverse charge distribution in a homogeneous vacuum chamber are studied. Signals induced by a displaced finite-size beam on electrodes of a beam position monitor (BPM are calculated and compared to those produced by a pencil beam. The nonlinearities and corrections to BPM signals due to a finite transverse beam size are calculated for an arbitrary chamber cross section. Simple analytical expressions are given for a few particular transverse distributions of the beam current in a circular or rectangular chamber. Of particular interest is a general proof that in an arbitrary homogeneous chamber the beam-size corrections vanish for any axisymmetric beam current distribution.

  14. Aberration Correction in Electron Microscopy

    CERN Document Server

    Rose, Harald H

    2005-01-01

    The resolution of conventional electron microscopes is limited by spherical and chromatic aberrations. Both defects are unavoidable in the case of static rotationally symmetric electromagnetic fields (Scherzer theorem). Multipole correctors and electron mirrros have been designed and built, which compensate for these aberrations. The principles of correction will be demonstrated for the tetrode mirror, the quadrupole-octopole corrector and the hexapole corrector. Electron mirrors require a magnetic beam separator free of second-order aberrations. The multipole correctors are highly symmetric telescopic systems compensating for the defects of the objective lens. The hexapole corrector has the most simple structure yet eliminates only the spherical aberration, whereas the mirror and the quadrupole-octopole corrector are able to correct for both aberrations. Chromatic correction is achieved in the latter corrector by cossed electric and magnetic quadrupoles acting as first-order Wien filters. Micrographs obtaine...

  15. Low energy high current pulsed electron beam treatment for improving surface microstructure and properties

    Energy Technology Data Exchange (ETDEWEB)

    Wu, J; Allain-Bonasso, N; Zhang, X D; Hao, S Z; Grosdider, T; Dong, C [Laboratoire d' Etude des Textures et Applications aux Materiaux (LETAM, UMR-CNRS 3143), Universite Paul Verlaine-Metz, Ile du Saulcy, 57045 Metz (France); Zou, J X, E-mail: jiang.wu@univ-metz.fr, E-mail: thierry.grosdidier@univ-metz.fr [National Engineering Research Center of Light Alloy Net Forming, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2010-06-15

    Low energy high current pulsed electron beam (LEHCPEB) is a fairly new technique for surface modifications authorizing improvement in wear and corrosion properties as well as texture changes and hardening. This contribution highlights some microstructure modifications encountered at the surface of HCPEB treated steels and bulk metallic glasses taking into account the effects of surface melting and the effects of the induced stress.

  16. Continuous Hardening During Isothermal Aging at 723 K (450 °C) of a Precipitation Hardening Stainless Steel

    Science.gov (United States)

    Celada-Casero, Carola; Chao, Jesús; Urones-Garrote, Esteban; San Martin, David

    2016-11-01

    The isothermal aging behavior of a cold-rolled precipitation hardening stainless steel has been studied at 723 K (450 °C) for holding times up to 72 hours. The precipitation hardening has been investigated using microhardness Vickers (Hv), thermoelectric power (TEP) measurements, and tensile testing. Microhardness compared to TEP measurements is more sensitive to detect the initial stages of aging. Two precipitation regimes have been observed: the first one related to the formation of Cu-clusters for aging times below 1 hour and a second one associated with formation of Ni-rich precipitates. The results show that the material exhibits an outstanding continuous age strengthening response over the aging time investigated, reaching a hardness of 710 ± 4 HV1 and an ultimate tensile strength ( σ UTS) of 2.65 ± 0.02 GPa after 72 hours. Engineering stress-plastic strain curves reveal that the strength increases and the ductility decreases as the aging time increases. However, after prolonged holding times (24-72 hours) and, although small, a rise in both the strength and the total elongation is observed. The precipitation kinetics can be well predicted over the entire range of aging times by the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. Finally, a reliable linear hardness-yield strength correlation has been found, which enables a rapid evaluation of the strength from bulk hardness measurements.

  17. Beam loading

    CERN Document Server

    Gamp, Alexander

    2013-01-01

    We begin by giving a description of the radio-frequency generator-cavity-beam coupled system in terms of basic quantities. Taking beam loading and cavity detuning into account, expressions for the cavity impedance as seen by the generator and as seen by the beam are derived. Subsequently methods of beam-loading compensation by cavity detuning, radio-frequency feedback and feedforward are described. Examples of digital radio-frequency phase and amplitude control for the special case of superconducting cavities are also given. Finally, a dedicated phase loop for damping synchrotron oscillations is discussed.

  18. Strain hardening as an indicator of bread-making performance: A review with discussion

    NARCIS (Netherlands)

    Vliet, van T.

    2008-01-01

    Since strain hardening has been proposed as an important quality indicator of dough with respect to bread-making performance, a large body of experimental support for this concept has been published. Nevertheless, some questions remain with respect to the use of the concept of strain hardening. This

  19. Numerical Simulation of Stresses due to Solid State Transformations : The Simulation of Laser Hardening

    NARCIS (Netherlands)

    Geijselaers, H.J.M.

    2003-01-01

    The properties of many engineeringmaterialsmay be favourablymodified by application of a suitable heat treatment. Examples are precipitation hardening, tempering and annealing. One of the most important treatments is the transformation hardening of steel. Steel is an alloy of iron and carbon. At roo

  20. Physical and Thermodynamical Properties of Water Phases in Hardening Portland Cement Systems

    DEFF Research Database (Denmark)

    Hansen, T. Bæk

    The present study is devoted to the description of water phases in hardening portland cement paste systems containing a significant amount of micro-filler and having a low to moderate water/powder ratio. Emphasis has been placed on the early stages of the hardening process....