Characterization of paraffin based breast tissue equivalent phantom using a CdTe detector pulse height analysis.

Science.gov (United States)

Cubukcu, Solen; Yücel, Haluk

2016-12-01

In this study, paraffin was selected as a base material and mixed with different amounts of CaSO 4 ·2H 2 O and H 3 BO 3 compounds in order to mimic breast tissue. Slab phantoms were produced with suitable mixture ratios of the additives in the melted paraffin. Subsequently, these were characterized in terms of first half-value layer (HVL) in the mammographic X-ray range using a pulse-height spectroscopic analysis with a CdTe detector. Irradiations were performed in the energy range of 23-35 kV p under broad beam conditions from Mo/Mo and Mo/Rh target/filter combinations. X-ray spectra were acquired with a CdTe detector without and with phantom material interposition in increments of 1 cm thickness and then evaluated to obtain the transmission data. The net integral areas of the spectra for the slabs were used to plot the transmission curves and these curves were fitted to the Archer model function. The results obtained for the slabs were compared with those of standard mammographic phantoms such as CIRS BR series phantoms and polymethylmethacrylate plates (PMMA). From the evaluated transmission curves, the mass attenuation coefficients and HVLs of some mixtures are close to those of the commercially available standard mammography phantoms. Results indicated that when a suitable proportion of H 3 BO 3 and CaSO 4 ·2H 2 O is added to the paraffin, the resulting material may be a good candidate for a breast tissue equivalent phantom.

Average glandular dose in digital mammography and digital breast tomosynthesis: comparison of phantom and patient data

NARCIS (Netherlands)

Bouwman, R. W.; van Engen, R. E.; Young, K. C.; den Heeten, G. J.; Broeders, M. J. M.; Schopphoven, S.; Jeukens, C. R. L. P. N.; Veldkamp, W. J. H.; Dance, D. R.

2015-01-01

For the evaluation of the average glandular dose (AGD) in digital mammography (DM) and digital breast tomosynthesis (DBT) phantoms simulating standard model breasts are used. These phantoms consist of slabs of polymethyl methacrylate (PMMA) or a combination of PMMA and polyethylene (PE). In the last

Dynamic Eigenvalue Problem of Concrete Slab Road Surface

Science.gov (United States)

Pawlak, Urszula; Szczecina, Michał

2017-10-01

The paper presents an analysis of the dynamic eigenvalue problem of concrete slab road surface. A sample concrete slab was modelled using Autodesk Robot Structural Analysis software and calculated with Finite Element Method. The slab was set on a one-parameter elastic subsoil, for which the modulus of elasticity was separately calculated. The eigen frequencies and eigenvectors (as maximal vertical nodal displacements) were presented. On the basis of the results of calculations, some basic recommendations for designers of concrete road surfaces were offered.

Evidence-based recommendations for musculoskeletal kinematic 4D-CT studies using wide area-detector scanners: a phantom study with cadaveric correlation

Energy Technology Data Exchange (ETDEWEB)

Gondim Teixeira, Pedro Augusto; Formery, Anne-Sophie; Blum, Alain [CHRU-Nancy Hopital Central, Service d' Imagerie Guilloz, Nancy (France); Hossu, Gabriela [Universite de Lorraine, IADI U947, Nancy (France); INSERM, CIC-IT 1433, Nancy (France); Winninger, Daniel [IDCmem, Nancy (France); Batch, Toufik [Hopital de Mercy, Service de Radiologie, Metz (France); Gervaise, Alban [Legouest Military Instruction Hospital, Medical Imaging Department, Metz (France)

2017-02-15

To establish evidence-based recommendations for musculoskeletal kinematic 4D-CT on wide area-detector CT. In order to assess factors influencing image quality in kinematic CT studies, a phantom consisting of a polymethylmethacrylate rotating disk with round wells of different sizes was imaged with various acquisition protocols. Cadaveric acquisitions were performed on the ankle joint during motion in two different axes and at different speeds to allow validation of phantom data. Images were acquired with a 320 detector-row CT scanner and were evaluated by two readers. Motion artefacts were significantly correlated with various parameters (movement axis, distance to centre, rotation speed and volume acquisition speed) (p < 0.0001). The relation between motion artefacts and distance to motion fulcrum was exponential (R{sup 2} 0.99). Half reconstruction led to a 23 % increase in image noise and a 40 % decrease in motion artefacts. Cadaveric acquisitions confirmed phantom data. Based on these findings, high tube rotation speed and half reconstruction are recommended for kinematic CT. The axis of motion significantly influences image artefacts and should be considered in patient training and evaluation of acquisition protocol suitability. This study provides evidence-based recommendations for musculoskeletal kinematic 4D-CT. (orig.)

Average glandular dose in digital mammography and digital breast tomosynthesis: comparison of phantom and patient data

International Nuclear Information System (INIS)

Bouwman, R W; Van Engen, R E; Den Heeten, G J; Broeders, M J M; Veldkamp, W J H; Young, K C; Dance, D R; Schopphoven, S; Jeukens, C R L P N

2015-01-01

For the evaluation of the average glandular dose (AGD) in digital mammography (DM) and digital breast tomosynthesis (DBT) phantoms simulating standard model breasts are used. These phantoms consist of slabs of polymethyl methacrylate (PMMA) or a combination of PMMA and polyethylene (PE). In the last decades the automatic exposure control (AEC) increased in complexity and became more sensitive to (local) differences in breast composition. The question is how well the AGD estimated using these simple dosimetry phantoms agrees with the average patient AGD. In this study the AGDs for both dosimetry phantoms and for patients have been evaluated for 5 different x-ray systems in DM and DBT modes. It was found that the ratios between patient and phantom AGD did not differ considerably using both dosimetry phantoms. These ratios averaged over all breast thicknesses were 1.14 and 1.15 for the PMMA and PMMA-PE dosimetry phantoms respectively in DM mode and 1.00 and 1.02 in the DBT mode. These ratios were deemed to be sufficiently close to unity to be suitable for dosimetry evaluation in quality control procedures. However care should be taken when comparing systems for DM and DBT since depending on the AEC operation, ratios for particular breast thicknesses may differ substantially (0.83–1.96). Although the predictions of both phantoms are similar we advise the use of PMMA  +  PE slabs for both DM and DBT to harmonize dosimetry protocols and avoid any potential issues with the use of spacers with the PMMA phantoms. (paper)

Behaviour of a stiffened circular slab

International Nuclear Information System (INIS)

Kulkarni, M.G.; Subramanian, K.V.

1975-01-01

Configuration of intake structure for cooling water system for Madras Atomic Power Project was studied on a hydraulic model and it was recommended to provide a circular slab in the structure to give directional property to the inflow and reduce air entrainment. This slab, as indicated by hydraulic model tests was required to withstand hydrodynamic pressures of the order of 10T/m 2 due to breaking waves of about 6 m height. Analysis of this circular cover slab, Stiffened by radial and circumferential beams, carried with the help of an analysis based on grid idealisation is presented. Results of approximate design analysis to assess behaviour of radial stiffener have been compared. Actual design is based on judgement of actual degree of fixity possessed by the supports or restraints. (author)

Experimental determination of the angular dependence factor for the dose equivalent for photons in calibration phantoms of PMMA

International Nuclear Information System (INIS)

Lund, E.; Carlsson, C.A.; Pernicka, F.

1994-01-01

The conversion coefficients from air kerma to dose equivalent at a depth of 10 mm in both a spherical and a slab phantom of PMMA have been determined for the X ray qualities: 40, 80 and 295 kV, ISO 'narrow' spectra; and for 137 Cs γ rays. The angular dependence factors have been experimentally determined for the same qualities and for different angles between 0 o and 180 o . The absorbed doses have been measured with thermoluminescence LiF dosemeters. The conversion coefficients and the angular dependence factors are generally found to agree well with calculated ones. Some minor discrepancies are found for the angular dependence factors and the 30 x 30 x 15 cm 3 PMMA slab phantom. (Author)

Recommended procedures for performance testing of radiobioassay laboratories: Volume 3, In vivo test phantoms

International Nuclear Information System (INIS)

MacLellan, J.A.; Traub, R.J.

1988-11-01

Draft American National Standards Institute (ANSI) Standard N13.30 (Performance Criteria for Radiobioassay) was developed for the US Department of Energy and the US Nuclear Regulatory Commission to help ensure that bioassay laboratories provide accurate and consistent results. The draft standard describes the procedures necessary to establish a bioassay performance-testing laboratory and program. The bioassay performance-testing laboratory will conduct tests to evaluate the performance of service laboratories. Pacific Northwest Laboratory helped develop testing procedures as part of an effort to evaluate the draft ANSI N13.30 performance criteria by testing the existing measurement capabilities of various bioassay laboratories. This report recommends guidelines for the preparation, handling, storage, distribution, shipping, and documentation of test phantoms used for calibration of measurement systems for direct bioassay. The data base and recommended records system for documenting radiobioassay performance at the service laboratories are also presented

Non-invasive perfusion imaging by modified STAR using asymmetric inversion slabs (ASTAR)

International Nuclear Information System (INIS)

Kimura, Tokunori

2000-01-01

Arterial spin labeling (ASL) such as STAR, EPISTAR, and FAIR have been used as imaging techniques of tissue perfusion and blood vessels (in MRA). We have developed 'ASTAR', a modified version of STAR by using asymmetric inversion slabs. ASTAR solves the problems of suppression of venous inflow and subtraction error of stationary tissue signal caused by the imbalance of signal variations. The signal variations are dependent on MT effects. In order to avoid overlapping the control slab to the tissue (including large veins), the control and tag slabs are arranged asymmetrically to preserve the same offset of modulation frequency. We evaluated both the subtraction error caused by the MT effects, and the imperfection of an IR slab using a stationary phantom. We then measured the vessel signal on the brain of a volunteer, using the above methods. Two indexes were used for the evaluation: ASL signal to control signal ratio (ASLR [%]=100*deltaS/S cont ) and ASL signal to noise ratio (ASLNR=delatS/Noise) where deltaS=|S cont -S tag |. Phantom study: each ASLR and ASLNR between ASTAR and EPISTAR was comparable and showed a decrease in noise signal level. This means that the ASL signal from the stationary tissue with an imbalance in MT effects and the imperfection in inversion slab profiles were cancelled out almost perfectly. When calculating CBF, ASLR for zero perfusion stationary tissue should be below 0.1%. We were able to satisfy this requirement in our ASTAR experiment. ASLR and ASLNR in FAIR were 40% larger than in EPISTAR and ASTAR. Volunteer brain study: compared with each ASL image, the MT effects were cancelled out in EPISTAR and ASTAR. Veins (sagittal sinus etc) disappeared in STAR and ASTAR, but were visible in EPISTAR and FAIR. Perfusion signals were similar in ASTAR and EPISTAR, indicating that both cancellation of MT effects and venous inflow from the opposite side of the tag were suppressed in ASTAR. In conclusion, ASTAR is a practical method to image blood

The role of phantom parameters on the response of the AEOI Neutriran Albedo Neutron Personnel Dosemeter

International Nuclear Information System (INIS)

Sohrabi, M.; Katouzi, M.

1992-01-01

The response of the AEOI Neutriran Albedo Neutron Personnel Dosemeter (NANPD) which can also be used for other albedo dosemeter types was determined on 18 different phantom configurations. The effects of type, geometry, material, thickness, dosemeter-to-phantom angle in particular with the presence of legs were investigated using a Pu-Be neutron source. It was concluded that the slab phantoms (single or double) and circular and elliptical cylinder phantoms seemed to provide a better response, whereas the ICRU sphere geometry does not seem to be appropriate for the calibration of albedo dosemeters. It is interesting to note that the presence of legs maintains the constancy of the response in a situation when a radiation worker bends down during work. (author)

A 2D ion chamber array audit of wedged and asymmetric fields in an inhomogeneous lung phantom

Energy Technology Data Exchange (ETDEWEB)

Lye, Jessica; Dunn, Leon, E-mail: leon.dunn@arpansa.gov.au; Alves, Andrew [Australian Clinical Dosimetry Service, Yallambie, Victoria 3085 (Australia); Kenny, John [Australian Clinical Dosimetry Service, Yallambie, Victoria 3085, Australia and Radiation Oncology Queensland, Toowoomba, Queensland 4350 (Australia); Lehmann, Joerg; Williams, Ivan [Australian Clinical Dosimetry Service, Yallambie, Victoria 3085, Australia and School of Applied Science, RMIT University, Melbourne 3000 (Australia); Kron, Tomas [School of Applied Science, RMIT University, Melbourne 3000, Australia and Peter MacCallum Cancer Centre, Melbourne 3008 (Australia); Cole, Andrew [Australian Clinical Dosimetry Service, Yallambie, Victoria 3085, Australia and Australian Radiation Protection and Nuclear Safety Agency, Yallambie, Victoria 3085 (Australia)

2014-10-15

Purpose: The Australian Clinical Dosimetry Service (ACDS) has implemented a new method of a nonreference condition Level II type dosimetric audit of radiotherapy services to increase measurement accuracy and patient safety within Australia. The aim of this work is to describe the methodology, tolerances, and outcomes from the new audit. Methods: The ACDS Level II audit measures the dose delivered in 2D planes using an ionization chamber based array positioned at multiple depths. Measurements are made in rectilinear homogeneous and inhomogeneous phantoms composed of slabs of solid water and lung. Computer generated computed tomography data sets of the rectilinear phantoms are supplied to the facility prior to audit for planning of a range of cases including reference fields, asymmetric fields, and wedged fields. The audit assesses 3D planning with 6 MV photons with a static (zero degree) gantry. Scoring is performed using local dose differences between the planned and measured dose within 80% of the field width. The overall audit result is determined by the maximum dose difference over all scoring points, cases, and planes. Pass (Optimal Level) is defined as maximum dose difference ≤3.3%, Pass (Action Level) is ≤5.0%, and Fail (Out of Tolerance) is >5.0%. Results: At close of 2013, the ACDS had performed 24 Level II audits. 63% of the audits passed, 33% failed, and the remaining audit was not assessable. Of the 15 audits that passed, 3 were at Pass (Action Level). The high fail rate is largely due to a systemic issue with modeling asymmetric 60° wedges which caused a delivered overdose of 5%–8%. Conclusions: The ACDS has implemented a nonreference condition Level II type audit, based on ion chamber 2D array measurements in an inhomogeneous slab phantom. The powerful diagnostic ability of this audit has allowed the ACDS to rigorously test the treatment planning systems implemented in Australian radiotherapy facilities. Recommendations from audits have led to

A 2D ion chamber array audit of wedged and asymmetric fields in an inhomogeneous lung phantom

International Nuclear Information System (INIS)

Lye, Jessica; Dunn, Leon; Alves, Andrew; Kenny, John; Lehmann, Joerg; Williams, Ivan; Kron, Tomas; Cole, Andrew

2014-01-01

Purpose: The Australian Clinical Dosimetry Service (ACDS) has implemented a new method of a nonreference condition Level II type dosimetric audit of radiotherapy services to increase measurement accuracy and patient safety within Australia. The aim of this work is to describe the methodology, tolerances, and outcomes from the new audit. Methods: The ACDS Level II audit measures the dose delivered in 2D planes using an ionization chamber based array positioned at multiple depths. Measurements are made in rectilinear homogeneous and inhomogeneous phantoms composed of slabs of solid water and lung. Computer generated computed tomography data sets of the rectilinear phantoms are supplied to the facility prior to audit for planning of a range of cases including reference fields, asymmetric fields, and wedged fields. The audit assesses 3D planning with 6 MV photons with a static (zero degree) gantry. Scoring is performed using local dose differences between the planned and measured dose within 80% of the field width. The overall audit result is determined by the maximum dose difference over all scoring points, cases, and planes. Pass (Optimal Level) is defined as maximum dose difference ≤3.3%, Pass (Action Level) is ≤5.0%, and Fail (Out of Tolerance) is >5.0%. Results: At close of 2013, the ACDS had performed 24 Level II audits. 63% of the audits passed, 33% failed, and the remaining audit was not assessable. Of the 15 audits that passed, 3 were at Pass (Action Level). The high fail rate is largely due to a systemic issue with modeling asymmetric 60° wedges which caused a delivered overdose of 5%–8%. Conclusions: The ACDS has implemented a nonreference condition Level II type audit, based on ion chamber 2D array measurements in an inhomogeneous slab phantom. The powerful diagnostic ability of this audit has allowed the ACDS to rigorously test the treatment planning systems implemented in Australian radiotherapy facilities. Recommendations from audits have led to

Concrete mixtures with high-workability for ballastless slab tracks

Directory of Open Access Journals (Sweden)

Olga Smirnova

2017-10-01

Full Text Available The concrete track-supporting layer and the monolithic concrete slab of ballastless track systems are made in-situ. For this reason the concrete mixtures of high workability should be used. Influence of the sand kind, the quartz microfiller fineness and quantity as well as quantity of superplasticizer on workability of fresh concrete and durability of hardened concrete is shown. The compositions of the high-workability concrete mixtures with lower consumption of superplasticizer are developed. The results of the research can be recommended for high performance concrete of ballastless slab track.

Sci-Sat AM: Radiation Dosimetry and Practical Therapy Solutions - 04: On 3D Fabrication of Phantoms and Experimental Verification of Patient Dose Computation Algorithms

Energy Technology Data Exchange (ETDEWEB)

Khan, Rao; Zavan, Rodolfo; McGeachy, Philip; Madamesila, Joseph; Villarreal-Barajas, Jose Eduardo [Radiation Oncology, Washington University School of Medicine, St Louis, MO, USA, Instituto de Física de São Carlos, Universidade de São Paulo, SP, Brazil, CancerCare Manitoba, Winnipeg,Manitoba, Physics and Astronomy, University of Calgary, Calgary, Alberta (Canada)

2016-08-15

Purpose: Transport based dose calculation algorithm Acuros XB (AXB) has been shown to accurately account for heterogeneities mostly through comparisons with Monte Carlo simulations. This study aims at providing additional experimental verification for AXB for flattened and unflattened clinical energies in low density phantoms of the same material. Materials and Methods: Polystyrene slabs were created using a bench-top 3D printer. Six slabs were printed at varying densities from 0.23 g/cm{sup 3} to 0.68 g/cm{sup 3}, corresponding to different density humanoid tissues. The slabs were used to form different single and multilayer geometries. Dose was calculated with AXB 11.0.31 for 6MV, 15MV flattened and 6FFF (flattening filter free) energies for field sizes of 2×2 cm{sup 2} and 5×5 cm{sup 2}. The phantoms containing radiochromic EBT3 films were irradiated. Absolute dose profiles and 2D gamma analyses were performed for 96 dose planes. Results: For all single slab, multislab configurations and energies, absolute dose differences between the AXB calculation and film measurements remained <3% for both fields, with slightly poor disagreement in penumbra. The gamma index at 2% / 2mm averaged 98% in all combinations of fields, phantoms and photon energies. Conclusions: The transport based dose algorithm AXB is in good agreement with the experimental measurements for small field sizes using 6MV, 6FFF and 15MV beams adjacent to low density heterogeneous media. This work provides sufficient experimental ground to support the use of AXB for heterogeneous dose calculation purposes.

Construction of foundation slab of Temelin reactor building

International Nuclear Information System (INIS)

Lebr, P.; Vyleta, M.

1988-01-01

The concreting is described of the foundation slab under the WWER-1000 reactor in the Temelin nuclear power plant. The slab area is 68x68 m and thickness 2.4 m. For ease of concreting, the slab was divided in 12 blocks with vertical partition walls of steel mesh. The total thickness was concreted in three stages in which the partial thicknesses slightly differed for operating reasons. The first two partial thicknesses were concreted in layers of 0.45 m each, the third thickness consisted of two layers of 0.30 m each. The reinforcement was completely cleaned of the concrete residues from the previous stages in the break between the second and the third stages. Totally, 11,050 m 3 concrete were used. Briefly described is quality control during concreting and experiences and recommendations are summed up for other concreting jobs. (Z.M.). 19 figs

Comparison of analytic and iterative digital tomosynthesis reconstructions for thin slab objects

Science.gov (United States)

Yun, J.; Kim, D. W.; Ha, S.; Kim, H. K.

2017-11-01

For digital x-ray tomosynthesis of thin slab objects, we compare the tomographic imaging performances obtained from the filtered backprojection (FBP) and simultaneous algebraic reconstruction (SART) algorithms. The imaging performance includes the in-plane molulation-transfer function (MTF), the signal difference-to-noise ratio (SDNR), and the out-of-plane blur artifact or artifact-spread function (ASF). The MTF is measured using a thin tungsten-wire phantom, and the SDNR and the ASF are measured using a thin aluminum-disc phantom embedded in a plastic cylinder. The FBP shows a better MTF performance than the SART. On the contrary, the SART outperforms the FBP with regard to the SDNR and ASF performances. Detailed experimental results and their analysis results are described in this paper. For a more proper use of digital tomosynthesis technique, this study suggests to use a reconstuction algorithm suitable for application-specific purposes.

SU-C-209-07: Phantoms for Digital Breast Tomosynthesis Imaging System Evaluation

Energy Technology Data Exchange (ETDEWEB)

Jacobson, D; Liu, Y [Medical College of Wisconsin, Milwaukee, WI (United States)

2016-06-15

Purpose: Digital Breast Tomosynthesis (DBT) is gaining importance in breast imaging. There is a need for phantoms that can be used for image evaluation and comparison. Existing commercially available phantoms for DBT are expensive and may lack clinically relevant test objects. The purpose of this study is to develop phantoms for DBT evaluation. Methods Four phantoms have been designed and constructed to assess the image quality (IQ) of two DBT systems. The first contains a spiral of 0.3 mm SiC beads in gelatin to measure the tomographic slice thickness profile and uniformity of coverage in a series of tomographic planes. The second contains simulated tumors inclined with respect to the phantom base to assess tomographic image quality. The third has a tilted array of discs with varying contrast and diameter. This phantom was imaged alone and in a stack of TE slabs giving 2 to 10 cm thickness. The fourth has a dual wedge of glandular and adipose simulating materials. One wedge contains discs with varying diameter and thickness; the other supports a mass with six simulated spicules of varying size and a cluster of simulated calcifications. The simulated glandular tissue material varies between 35 and 100% of the total thickness (5.5 cm). Results: All phantoms were scanned successfully. The best IQ comparison was achieved with the dual wedge phantom as demonstrated by the spiculated mass and calcifications. Images were evaluated by two radiologists and one physicist. The projection images and corresponding set of tomographic planes were comparable and the synthesized projection images were inferior to the projection images for both systems. Conclusion: Four phantoms were designed, constructed and imaged on two DBT systems. They successfully demonstrated performance differences between two systems, and between true and synthesized projection images. Future work will incorporate these designs into a single phantom.

The Japanese adult, child and infant phantoms

International Nuclear Information System (INIS)

Cristy, Mark; Egbert, Stephen D.

1987-01-01

The mathematical phantom for adult Japanese atomic-bomb survivors is a modification of the 57-kg ORNL (Oak Ridge National Laboratory) phantom for Western 15-year-old males and adult females. For younger Japanese survivors mathematical phantoms were similarly modified from the 18 and 9 kg ORNL phantoms for Western 5- and 1-year-olds, respectively. To make the phantom correspond more closely with dimensions and organ sizes recommended for Japanese adults by Maruyama and coworkers (cf E184), changes were made in the size of the lungs, the pancreas, the thyroid, and the testes and in the length of the legs. Also, the head-and-neck region was modified to improve the dose estimates for the thyroid from external radiation, after the ideas of Nagarajan et al. The arms were separated from the trunk to represent more accurately the shielding by the phantom in external exposures. Furthermore, provisions were made to provide a phantom in a kneeling posture. The elemental composition of the tissues was changed to that given by Kerr. The resulting phantom is slightly smaller in mass (55 kg). Details of these changes are given

A phantom for assessing the personal dose equivalent, HP(10)

International Nuclear Information System (INIS)

Santoro, C.; Filho, J.A

2013-01-01

Characteristics of a phantom designed to evaluate the personal dose equivalent, H P (10), and appropriate for photographic dosimetry are presented. It is called HP(10) phantom due to cavities constructed to insert dosimetric films at a depth of 10 mm. The H P (10) phantom is irradiated with ionizing radiation energy, E, from 45 to 1250 keV, with doses ranging from 0.2 to 50 mSv. It is positioned in the direction α = 0 °, and the radiation field focusing perpendicular to its front surface. So, are established calibration curves of dosimeters in the position conventionally true and quantities H P (10). It made a comparison between the responses obtained with the H P (10) phantom and responses obtained when using the calibration procedure recommended by ISO dosimeters. The ISO recommends getting the air kerma, Ka, for photons at test point of the radiation field by an ionization chamber. And through conversion coefficients, h pK (10; E, α), becomes the air kerma for H P (10). The ISO 4037-3 recommendation has been studied by researchers to ensure that the low energy spectral differences occur in radiation fields which are generated by various X-ray equipment, and induce changes in the percentages of conversion coefficients on the order of 10% to 90% . On the basis of the recommendations ISO, this article develops phantom able to assess the dose to the influence of scattering and absorption of radiation, its implications with respect to dosimetry, providing improvement in the assessment of doses. (author)

Comparison of dose calculation algorithms in slab phantoms with cortical bone equivalent heterogeneities

International Nuclear Information System (INIS)

Carrasco, P.; Jornet, N.; Duch, M. A.; Panettieri, V.; Weber, L.; Eudaldo, T.; Ginjaume, M.; Ribas, M.

2007-01-01

To evaluate the dose values predicted by several calculation algorithms in two treatment planning systems, Monte Carlo (MC) simulations and measurements by means of various detectors were performed in heterogeneous layer phantoms with water- and bone-equivalent materials. Percentage depth doses (PDDs) were measured with thermoluminescent dosimeters (TLDs), metal-oxide semiconductor field-effect transistors (MOSFETs), plane parallel and cylindrical ionization chambers, and beam profiles with films. The MC code used for the simulations was the PENELOPE code. Three different field sizes (10x10, 5x5, and 2x2 cm 2 ) were studied in two phantom configurations and a bone equivalent material. These two phantom configurations contained heterogeneities of 5 and 2 cm of bone, respectively. We analyzed the performance of four correction-based algorithms and one based on convolution superposition. The correction-based algorithms were the Batho, the Modified Batho, the Equivalent TAR implemented in the Cadplan (Varian) treatment planning system (TPS), and the Helax-TMS Pencil Beam from the Helax-TMS (Nucletron) TPS. The convolution-superposition algorithm was the Collapsed Cone implemented in the Helax-TMS. All the correction-based calculation algorithms underestimated the dose inside the bone-equivalent material for 18 MV compared to MC simulations. The maximum underestimation, in terms of root-mean-square (RMS), was about 15% for the Helax-TMS Pencil Beam (Helax-TMS PB) for a 2x2 cm 2 field inside the bone-equivalent material. In contrast, the Collapsed Cone algorithm yielded values around 3%. A more complex behavior was found for 6 MV where the Collapsed Cone performed less well, overestimating the dose inside the heterogeneity in 3%-5%. The rebuildup in the interface bone-water and the penumbra shrinking in high-density media were not predicted by any of the calculation algorithms except the Collapsed Cone, and only the MC simulations matched the experimental values within

Comparison of dose calculation algorithms in slab phantoms with cortical bone equivalent heterogeneities.

Science.gov (United States)

Carrasco, P; Jornet, N; Duch, M A; Panettieri, V; Weber, L; Eudaldo, T; Ginjaume, M; Ribas, M

2007-08-01

To evaluate the dose values predicted by several calculation algorithms in two treatment planning systems, Monte Carlo (MC) simulations and measurements by means of various detectors were performed in heterogeneous layer phantoms with water- and bone-equivalent materials. Percentage depth doses (PDDs) were measured with thermoluminescent dosimeters (TLDs), metal-oxide semiconductor field-effect transistors (MOSFETs), plane parallel and cylindrical ionization chambers, and beam profiles with films. The MC code used for the simulations was the PENELOPE code. Three different field sizes (10 x 10, 5 x 5, and 2 x 2 cm2) were studied in two phantom configurations and a bone equivalent material. These two phantom configurations contained heterogeneities of 5 and 2 cm of bone, respectively. We analyzed the performance of four correction-based algorithms and one based on convolution superposition. The correction-based algorithms were the Batho, the Modified Batho, the Equivalent TAR implemented in the Cadplan (Varian) treatment planning system (TPS), and the Helax-TMS Pencil Beam from the Helax-TMS (Nucletron) TPS. The convolution-superposition algorithm was the Collapsed Cone implemented in the Helax-TMS. All the correction-based calculation algorithms underestimated the dose inside the bone-equivalent material for 18 MV compared to MC simulations. The maximum underestimation, in terms of root-mean-square (RMS), was about 15% for the Helax-TMS Pencil Beam (Helax-TMS PB) for a 2 x 2 cm2 field inside the bone-equivalent material. In contrast, the Collapsed Cone algorithm yielded values around 3%. A more complex behavior was found for 6 MV where the Collapsed Cone performed less well, overestimating the dose inside the heterogeneity in 3%-5%. The rebuildup in the interface bone-water and the penumbra shrinking in high-density media were not predicted by any of the calculation algorithms except the Collapsed Cone, and only the MC simulations matched the experimental values

The dynamics of double slab subduction

Science.gov (United States)

Holt, A. F.; Royden, L. H.; Becker, T. W.

2017-04-01

We use numerical models to investigate the dynamics of two interacting slabs with parallel trenches. Cases considered are: a single slab reference, outward dipping slabs (out-dip), inward dipping slabs (in-dip) and slabs dipping in the same direction (same-dip). Where trenches converge over time (same-dip and out-dip systems), large positive dynamic pressures in the asthenosphere are generated beneath the middle plate and large trench-normal extensional forces are transmitted through the middle plate. This results in slabs that dip away from the middle plate at depth, independent of trench geometry. The single slab, the front slab in the same-dip case and both out-dip slabs undergo trench retreat and exhibit stable subduction. However, slabs within the other double subduction systems tend to completely overturn at the base of the upper mantle, and exhibit either trench advance (rear slab in same-dip), or near-stationary trenches (in-dip). For all slabs, the net slab-normal dynamic pressure at 330 km depth is nearly equal to the slab-normal force induced by slab buoyancy. For double subduction, the net outward force on the slabs due to dynamic pressure from the asthenosphere is effectively counterbalanced by the net extensional force transmitted through the middle plate. Thus, dynamic pressure at depth, interplate coupling and lithospheric stresses are closely linked and their effects cannot be isolated. Our results provide insights into both the temporal evolution of double slab systems on Earth and, more generally, how the various components of subduction systems, from mantle flow/pressure to interplate coupling, are dynamically linked.

Experimental sensitivity analysis of subsoil-slab behaviour regarding degree of fibre-concrete slab reinforcement

Science.gov (United States)

Hrubesova, E.; Lahuta, H.; Mohyla, M.; Quang, T. B.; Phi, N. D.

2018-04-01

The paper is focused on the sensitivity analysis of behaviour of the subsoil – foundation system as regards the variant properties of fibre-concrete slab resulting into different relative stiffness of the whole cooperating system. The character of slab and its properties are very important for the character of external load transfer, but the character of subsoil cannot be neglected either because it determines the stress-strain behaviour of the all system and consequently the bearing capacity of structure. The sensitivity analysis was carried out based on experimental results, which include both the stress values in soil below the foundation structure and settlements of structure, characterized by different quantity of fibres in it. Flat dynamometers GEOKON were used for the stress measurements below the observed slab, the strains inside slab were registered by tensometers, the settlements were monitored geodetically. The paper is focused on the comparison of soil stresses below the slab for different quantity of fibres in structure. The results obtained from the experimental stand can contribute to more objective knowledge of soil – slab interaction, to the evaluation of real carrying capacity of the slab, to the calibration of corresponding numerical models, to the optimization of quantity of fibres in the slab, and finally, to higher safety and more economical design of slab.

Anthropomorphic phantom materials

International Nuclear Information System (INIS)

White, D.R.; Constantinou, C.

1982-01-01

The need, terminology and history of tissue substitutes are outlined. Radiation properties of real tissues are described and simulation procedures are outlined. Recent tissue substitutes are described and charted, as are calculated radiation classifications. Manufacturing procedures and quality control are presented. Recent phantom studies are reviewed and a discussion recorded. Elemental compositions of the recommended tissue substitutes are charted with elemental composition given for each tissue substitute

Phantom Eye Syndrome: A Review of the Literature

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Agda M. Andreotti

2014-01-01

Full Text Available The purpose of this literature review was to describe the main features of phantom eye syndrome in relation to their possible causes, symptoms, treatments, and influence of eye amputation on quality of life of anophthalmic patients. For this, a bibliographical research was performed in Pubmed database using the following terms: “eye amputation,” “eye trauma,” “phantom eye syndrome,” “phantom pain,” and “quality of life,” associated or not. Thirteen studies were selected, besides some relevant references contained in the selected manuscripts and other studies hallowed in the literature. Thus, 56 articles were included in this review. The phantom eye syndrome is defined as any sensation reported by the patient with anophthalmia, originated anophthalmic cavity. In phantom eye syndrome, at least one of these three symptoms has to be present: phantom vision, phantom pain, and phantom sensations. This syndrome has a direct influence on the quality of life of the patients, and psychological support is recommended before and after the amputation of the eyeball as well as aid in the treatment of the syndrome. Therefore, it is suggested that, for more effective treatment of phantom eye syndrome, drug therapy should be associated with psychological approach.

Construction of an Anthropomorphic Phantom for Use in Evaluating Pediatric Airway Digital Tomosynthesis Protocols

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Nima Kasraie

2018-01-01

Full Text Available Interpretation of radiolucent foreign bodies (FBs is a common task charged to pediatric radiologists. The use of a motion compensated technique to decrease breathing motion on images would greatly decrease overall exposure to ionizing radiation and increase access to treatment yielding a great impact on clinical care. This study reports on the methodology and materials used to construct an in-house anthropomorphic phantom for investigating image quality in digital tomosynthesis protocols for volumetric imaging of the pediatric airway. Availability and cost of possible substitute materials were considered and simplifying assumptions were made. Two different modular phantoms were assembled in coronal slab layers using materials designed to approximate a one- and three-year-old thorax at diagnostic photon energies for use with digital tomosynthesis protocols such as those offered on GE’s VolumeRAD application. Exposures were made using both phantoms with inserted food particles inside an oscillating airway. The goal of the phantom is to help evaluate (1 whether the currently used protocol is sufficient to image the airway despite breathing motion and (2 whether it is not, to find the optimal protocol by testing various commercially available protocols using this phantom. The affordable construction of the pediatric sized phantom aimed at optimizing GE’s VolumeRAD protocol for airway foreign body imaging is demonstrated in this study which can be used to test VolumeRAD’s ability to image the airways with and without a low-density foreign body within the airways.

Determination of equivalent breast phantoms for different age groups of Taiwanese women: An experimental approach

International Nuclear Information System (INIS)

Dong, Shang-Lung; Chu, Tieh-Chi; Lin, Yung-Chien; Lan, Gong-Yau; Yeh, Yu-Hsiu; Chen, Sharon; Chuang, Keh-Shih

2011-01-01

Purpose: Polymethylmethacrylate (PMMA) slab is one of the mostly used phantoms for studying breast dosimetry in mammography. The purpose of this study was to evaluate the equivalence between exposure factors acquired from PMMA slabs and patient cases of different age groups of Taiwanese women in mammography. Methods: This study included 3910 craniocaudal screen/film mammograms on Taiwanese women acquired on one mammographic unit. The tube loading, compressed breast thickness (CBT), compression force, tube voltage, and target/filter combination for each mammogram were collected for all patients. The glandularity and the equivalent thickness of PMMA were determined for each breast using the exposure factors of the breast in combination with experimental measurements from breast-tissue-equivalent attenuation slabs. Equivalent thicknesses of PMMA to the breasts of Taiwanese women were then estimated. Results: The average ± standard deviation CBT and breast glandularity in this study were 4.2 ± 1.0 cm and 54% ± 23%, respectively. The average equivalent PMMA thickness was 4.0 ± 0.7 cm. PMMA slabs producing equivalent exposure factors as in the breasts of Taiwanese women were determined for the age groups 30-49 yr and 50-69 yr. For the 4-cm PMMA slab, the CBT and glandularity values of the equivalent breast were 4.1 cm and 65%, respectively, for the age group 30-49 yr and 4.4 cm and 44%, respectively, for the age group 50-69 yr. Conclusions: The average thickness of PMMA slabs producing the same exposure factors as observed in a large group of Taiwanese women is less than that reported for American women. The results from this study can provide useful information for determining a suitable thickness of PMMA for mammographic dose survey in Taiwan. The equivalence of PMMA slabs and the breasts of Taiwanese women is provided to allow average glandular dose assessment in clinical practice.

Determination of equivalent breast phantoms for different age groups of Taiwanese women: An experimental approach

Energy Technology Data Exchange (ETDEWEB)

Dong, Shang-Lung; Chu, Tieh-Chi; Lin, Yung-Chien; Lan, Gong-Yau; Yeh, Yu-Hsiu; Chen, Sharon; Chuang, Keh-Shih [Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, 101 Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan (China); Department of Radiology, Cheng Hsin General Hospital, 45 Cheng Hsin Street, Pai-Tou District, Taipei 11220, Taiwan (China); Department of Medical Imaging and Radiological Sciences, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung 80708, Taiwan (China); Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, 101 Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan (China)

2011-07-15

Purpose: Polymethylmethacrylate (PMMA) slab is one of the mostly used phantoms for studying breast dosimetry in mammography. The purpose of this study was to evaluate the equivalence between exposure factors acquired from PMMA slabs and patient cases of different age groups of Taiwanese women in mammography. Methods: This study included 3910 craniocaudal screen/film mammograms on Taiwanese women acquired on one mammographic unit. The tube loading, compressed breast thickness (CBT), compression force, tube voltage, and target/filter combination for each mammogram were collected for all patients. The glandularity and the equivalent thickness of PMMA were determined for each breast using the exposure factors of the breast in combination with experimental measurements from breast-tissue-equivalent attenuation slabs. Equivalent thicknesses of PMMA to the breasts of Taiwanese women were then estimated. Results: The average {+-} standard deviation CBT and breast glandularity in this study were 4.2 {+-} 1.0 cm and 54% {+-} 23%, respectively. The average equivalent PMMA thickness was 4.0 {+-} 0.7 cm. PMMA slabs producing equivalent exposure factors as in the breasts of Taiwanese women were determined for the age groups 30-49 yr and 50-69 yr. For the 4-cm PMMA slab, the CBT and glandularity values of the equivalent breast were 4.1 cm and 65%, respectively, for the age group 30-49 yr and 4.4 cm and 44%, respectively, for the age group 50-69 yr. Conclusions: The average thickness of PMMA slabs producing the same exposure factors as observed in a large group of Taiwanese women is less than that reported for American women. The results from this study can provide useful information for determining a suitable thickness of PMMA for mammographic dose survey in Taiwan. The equivalence of PMMA slabs and the breasts of Taiwanese women is provided to allow average glandular dose assessment in clinical practice.

Long-life slab replacement concrete.

Science.gov (United States)

2015-03-01

This research was initiated following reports of high incidence of cracking on FDOT concrete pavement replacement : slab projects. Field slabs were instrumented for data acquisition from high-early-strength concrete pavement : replacement slabs place...

Influence of slab length on dynamic characteristics of subway train-steel spring floating slab track-tunnel coupled system

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Qing-yuan Xu

Full Text Available A subway train-steel spring floating slab track-tunnel coupling dynamic model, considering short and middle-long wavelength random track irregularities, and longitudinal connection between adjacent slabs of steel spring floating slab track, was developed. And the influence of slab length on dynamic characteristics of the system under different track conditions and train speeds are theoretically studied. The calculated results show: (1 In general, the acceleration of each component of the coupled system decreases with the increase of slab length under the perfectly smooth track condition; (2 Slab length has different influence laws on acceleration of each component of subway train-steel spring floating slab track-tunnel coupled system under random irregularity of track condition. The lower the dominant frequency distribution of vibration acceleration is, the higher influence slab length has; (3 With the increase of slab length, the force of rail, fastener and steel spring also decreases significantly, which helps to lengthen the service life of these components; (4 With the increase of slab length, the longitudinal bending moment of slab increases sharply at first, then it begins to drop slightly. When slab length exceeds the distance between two bogies of a vehicle, the longitudinal bending moment of slab changes little; (5 Slab length has significant influence on the dynamic force and displacement of the coupled system when train speed is higher.

Measurement of TLD Albedo response on various calibration phantoms

International Nuclear Information System (INIS)

Momose, T.; Tsujimura, N.; Shinohara, K.; Ishiguro, H.; Nakamura, T.

1996-01-01

The International Commission on Radiation Units and Measurements (ICRU) has recommended that individual dosemeter should be calibrated on a suitable phantom and has pointed out that the calibration factor of a neutron dosemeter is strongly influenced by the the exact size and shape of the body and the phantom to which the dosemeter is attached. As the principle of an albedo type thermoluminescent personal dosemeter (albedo TLD) is essentially based on a detection of scattered and moderated neutron from a human body, the sensitivity of albedo TLD is strongly influenced by the incident neutron energy and the calibration phantom. (1) Therefore for albedo type thermoluminescent personal dosemeter (albedo TLD), the information of neutron albedo response on the calibration phantom is important for appropriate dose estimation. In order to investigate the effect of phantom type on the reading of the albedo TLD, measurement of the TLD energy response and angular response on some typical calibration phantoms was performed using dynamitron accelerator and 252 Cf neutron source. (author)

Technical Note: Experimental carbon ion range verification in inhomogeneous phantoms using prompt gammas

Energy Technology Data Exchange (ETDEWEB)

Pinto, M.; Dauvergne, D.; Dedes, G.; Krimmer, J.; Ray, C.; Testa, E., E-mail: e.testa@ipnl.in2p3.fr; Testa, M. [IPNL, Université de Lyon, Lyon F-69003 |(France); Université Lyon 1, Villeurbanne F-69622 (France); CNRS/IN2P3, UMR 5822, Villeurbanne F-69622 (France); De Rydt, M. [IPNL, Université de Lyon, Lyon F-69003 (France); Université Lyon 1, Villeurbanne F-69622 (France); CNRS/IN2P3, UMR 5822, Villeurbanne F-69622 (France); Instituut voor Kern- en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, Leuven B-3001 (Belgium); Freud, N.; Létang, J. M. [CREATIS, Université de Lyon, Lyon F-69003 (France); Université Lyon 1, Villeurbanne F-69622 (France); CNRS UMR 5220, INSERM U1044, INSA-Lyon, Centre Léon Bérard, 69008 Lyon (France)

2015-05-15

Purpose: The purpose of this study was to experimentally assess the possibility to monitor carbon ion range variations—due to tumor shift and/or elongation or shrinking—using prompt-gamma (PG) emission with inhomogeneous phantoms. Such a study is related to the development of PG monitoring techniques to be used in a carbon ion therapy context. Methods: A 95 MeV/u carbon ion beam was used to irradiate phantoms with a variable density along the ion path to mimic the presence of bone and lung in homogeneous humanlike tissue. PG profiles were obtained after a longitudinal scan of the phantoms. A setup comprising a narrow single-slit collimator and two detectors placed at 90° with respect to the beam axis was used. The time of flight technique was applied to allow the selection between PG and background events. Results: Using the positions at 50% entrance and 50% falloff of the PG profiles, a quantity called prompt-gamma profile length (PGPL) is defined. It is possible to observe shifts in the PGPL when there are absolute ion range shifts as small as 1–2 mm. Quantitatively, for an ion range shift of −1.33 ± 0.46 mm (insertion of a Teflon slab), a PGPL difference of −1.93 ± 0.58 mm and −1.84 ± 1.27 mm is obtained using a BaF{sub 2} and a NaI(Tl) detector, respectively. In turn, when an ion range shift of 4.59 ± 0.42 mm (insertion of a lung-equivalent material slab) is considered, the difference is of 4.10 ± 0.54 and 4.39 ± 0.80 mm for the same detectors. Conclusions: Herein, experimental evidence of the usefulness of employing PG to monitor carbon ion range using inhomogeneous phantoms is presented. Considering the homogeneous phantom as reference, the results show that the information provided by the PG emission allows for detecting ion range shifts as small as 1–2 mm. When considering the expected PG emission from an energy slice in a carbon ion therapy scenario, the experimental setup would allow to retrieve the same PGPL as the high statistics of

Analysis of the Dose Distribution of Moving Organ using a Moving Phantom System

International Nuclear Information System (INIS)

Kim, Yon Lae; Park, Byung Moon; Bae, Yong Ki; Kang, Min Young; Bang, Dong Wan; Lee, Gui Won

2006-01-01

Few researches have been performed on the dose distribution of the moving organ for radiotherapy so far. In order to simulate the organ motion caused by respiratory function, multipurpose phantom and moving device was used and dosimetric measurements for dose distribution of the moving organs were conducted in this study. The purpose of our study was to evaluate how dose distributions are changed due to respiratory motion. A multipurpose phantom and a moving device were developed for the measurement of the dose distribution of the moving organ due to respiratory function. Acryl chosen design of the phantom was considered the most obvious choice for phantom material. For construction of the phantom, we used acryl and cork with density of 1.14 g/cm 3 , 0.32 g/cm 3 respectively. Acryl and cork slab in the phantom were used to simulate the normal organ and lung respectively. The moving phantom system was composed of moving device, moving control system, and acryl and cork phantom. Gafchromic film and EDR2 film were used to measure dose distributions. The moving device system may be driven by two directional step motors and able to perform 2 dimensional movements (x, z axis), but only 1 dimensional movement(z axis) was used for this study. Larger penumbra was shown in the cork phantom than in the acryl phantom. The dose profile and isodose curve of Gafchromic EBT film were not uniform since the film has small optical density responding to the dose. As the organ motion was increased, the blurrings in penumbra, flatness, and symmetry were increased. Most of measurements of dose distributions, Gafchromic EBT film has poor flatness and symmetry than EDR2 film, but both penumbra distributions were more or less comparable. The Gafchromic EBT film is more useful as it does not need development and more radiation dose could be exposed than EDR2 film without losing film characteristics. But as response of the optical density of Gafchromic EBT film to dose is low, beam profiles

MODOS GUIADOS EM SLABS METAMATERIAIS GUIDED MODES IN METAMATERIAL SLABS

Directory of Open Access Journals (Sweden)

Leonardo André Ambrosio

2006-12-01

Full Text Available Este trabalho apresenta um estudo de revisão de modos propagantes em um guia-de-onda slab constituído de materiais com índices de refração negativo, os chamados metamateriais, Mostra-se que os modos guiados em um slab metamaterial possuem algumas propriedades particulares, tais como a propagação de ondas lentas simétricas ou anti-simétricas, a ausência de modos fundamentais para ondas rápidas e a possibilidade de propagação de ondas guiadas em um meio menos denso. A análise é baseada em expansões de campo no guia e nos espaços superior e inferior ao mesmo.This paper presents a review of the propagation modes in a slab waveguide consisting of negative refraction index materials, known as metamaterials. Some particular properties of guided modes in a metamaterial slab, such as slow symmetric or antisymmetric slow wave propagation, the absence of fundamental modes for fast waves and the possibility of guided waves in a less dense medium. The analysis is based on field expansions in the guide and the upper and lower spaces of it.

Preface: Deep Slab and Mantle Dynamics

Science.gov (United States)

Suetsugu, Daisuke; Bina, Craig R.; Inoue, Toru; Wiens, Douglas A.

2010-11-01

We are pleased to publish this special issue of the journal Physics of the Earth and Planetary Interiors entitled "Deep Slab and Mantle Dynamics". This issue is an outgrowth of the international symposium "Deep Slab and Mantle Dynamics", which was held on February 25-27, 2009, in Kyoto, Japan. This symposium was organized by the "Stagnant Slab Project" (SSP) research group to present the results of the 5-year project and to facilitate intensive discussion with well-known international researchers in related fields. The SSP and the symposium were supported by a Grant-in-Aid for Scientific Research (16075101) from the Ministry of Education, Culture, Sports, Science and Technology of the Japanese Government. In the symposium, key issues discussed by participants included: transportation of water into the deep mantle and its role in slab-related dynamics; observational and experimental constraints on deep slab properties and the slab environment; modeling of slab stagnation to constrain its mechanisms in comparison with observational and experimental data; observational, experimental and modeling constraints on the fate of stagnant slabs; eventual accumulation of stagnant slabs on the core-mantle boundary and its geodynamic implications. This special issue is a collection of papers presented in the symposium and other papers related to the subject of the symposium. The collected papers provide an overview of the wide range of multidisciplinary studies of mantle dynamics, particularly in the context of subduction, stagnation, and the fate of deep slabs.

Fabrication and characterization of a 3-D non-homogeneous tissue-like mouse phantom for optical imaging

Science.gov (United States)

Avtzi, Stella; Zacharopoulos, Athanasios; Psycharakis, Stylianos; Zacharakis, Giannis

2013-11-01

In vivo optical imaging of biological tissue not only requires the development of new theoretical models and experimental procedures, but also the design and construction of realistic tissue-mimicking phantoms. However, most of the phantoms available currently in literature or the market, have either simple geometrical shapes (cubes, slabs, cylinders) or when realistic in shape they use homogeneous approximations of the tissue or animal under investigation. The goal of this study is to develop a non-homogeneous realistic phantom that matches the anatomical geometry and optical characteristics of the mouse head in the visible and near-infrared spectral range. The fabrication of the phantom consisted of three stages. Initially, anatomical information extracted from either mouse head atlases or structural imaging modalities (MRI, XCT) was used to design a digital phantom comprising of the three main layers of the mouse head; the brain, skull and skin. Based on that, initial prototypes were manufactured by using accurate 3D printing, allowing complex objects to be built layer by layer with sub-millimeter resolution. During the second stage the fabrication of individual molds was performed by embedding the prototypes into a rubber-like silicone mixture. In the final stage the detailed phantom was constructed by loading the molds with epoxy resin of controlled optical properties. The optical properties of the resin were regulated by using appropriate quantities of India ink and intralipid. The final phantom consisted of 3 layers, each one with different absorption and scattering coefficient (μa,μs) to simulate the region of the mouse brain, skull and skin.

Electron beam dosimetry in heterogeneous phantoms using a MAGIC normoxic polymer gel

International Nuclear Information System (INIS)

Ghahraman Asl, R.; Nedaie, H.; Bolouri, B.; Arbabi, A.

2010-01-01

Nowadays radiosensitive polymer gels are used as a reliable dosimetry tool for verification of 3D dose distributions. Special characteristics of these dosimeters have made them useful for verification of complex dose distributions in clinical situations. The aim of this work was to evaluate the capability of a normoxic polymer gel to determine electron dose distributions in different slab phantoms in presence of small heterogeneities. Materials and Methods: Different cylindrical phantoms consisting gel were used under slab phantoms during each irradiation. MR images of irradiated gel phantoms were obtained to determine their R2 relaxation maps. 1D and 2D lateral dose profiles were acquired at depths of 1 cm for an 8 MeV beam and 1 and 4 cm for the 15 MeV energy, and then compared with the lateral dose profiles measured using a diode detector. In addition, 3D dose distributions around these heterogeneities for the same energies and depths were measured using a gel dosimeter. Results: Dose resolution for MR gel images at the range of 0-10 Gy was less than 1.55 Gy. Mean dose difference and distance to agreement for dose profiles were 2.6% and 2.2 mm, respectively. The results of the MAGIC-type polymer gel for bone heterogeneity at 8 MeV showed a reduction in dose of approximately 50%, and 30% and 10% at depths 1 and 4 cm at 15 MeV. However, for air heterogeneity increases in dose of approximately 50% at depth 1 cm under the heterogeneity at 8 MeV and 20% and 45% respectively at 15 MeV were observed. Discussion and Conclusion: Generally, electron beam distributions are significantly altered in the presence of tissue inhomogeneities such as bone and air cavities, this being related to mass stopping and mass scattering powers of heterogeneous materials. At the same time, hot and cold scatter lobes under heterogeneity regions due to scatter edge effects were also seen. However, these effects (increased dose, reduced dose, hot and cold spots) at deeper depths, are

Symbol phantoms

International Nuclear Information System (INIS)

Yamaguchi, Hiroshi; Hongo, Syozo; Takeshita, Hiroshi

1990-01-01

We have developed Japanese phantoms in two procedures for computation of organ doses exposed to internal and/or external radiation sources. One method is to make mathematical phantoms on the basis of ORNL mathematical phantoms. Parameters to specify organs of Japanese mathematical phantom are determined by interpolations of the ORNL data, which define the organs of Caucasian males and females of various ages, i.e. new born, 1, 5, 10, 15 years and adult, with survey data for Japanese physiques. Another procedure is to build 'symbol phantoms' for the Japanese public. The concept and its method of the symbol phantom enables us to make a phantom for an individual when we have all of his transversal section images obtained by a medical imaging device like MRI, and thus we may achieve more realistic phantoms for Japanese public than the mathematical phantoms. Both studies are in progress in NIRS. (author)

Spread prestressed concrete slab beam bridges.

Science.gov (United States)

2015-04-01

TxDOT uses prestressed slab beam bridges for short-span bridges ranging from approximately 3050 ft in : length. These bridges have precast, pretensioned slab beams placed immediately adjacent to one another : with a cast-in-place slab made composi...

Generating Atomistic Slab Surfaces with Adsorbates

Science.gov (United States)

2017-12-01

slabs of various thickness and with various vacuum spacing need be calculated. This can occur in serial or simultaneously . If performed in serial, the...the user. Although the optimization of the slab thickness and vacuum padding can be done simultaneously , it is more computationally conservative to...monolayer is a slab (True if slab), the type of mesh desired (adsorbates.py was written for “Gamma”), how detailed the mesh should be (in units of inverse

Behaviour of reinforced concrete slabs with steel fibers

Science.gov (United States)

Baarimah, A. O.; Syed Mohsin, S. M.

2017-11-01

This paper investigates the potential effect of steel fiber added into reinforced concrete slabs. Four-point bending test is conducted on six slabs to investigate the structural behaviour of the slabs by considering two different parameters; (i) thickness of slab (ii) volume fraction of steel fiber. The experimental work consists of six slabs, in which three slabs are designed in accordance to Eurocode 2 to fulfil shear capacity characteristic, whereas, the other three slabs are designed with 17% less thickness, intended to fail in shear. Both series of slabs are added with steel fiber with a volume fraction of Vf = 0%, Vf = 1% and Vf = 2% in order to study the effect and potential of fiber to compensate the loss in shear capacity. The slab with Vf = 0% steel fiber and no reduction in thickness is taken as the control slab. The experimental result suggests promising improvement of the load carrying capacity (up to 32%) and ductility (up to 87%) as well as delayed in crack propagation for the slabs with Vf = 2%. In addition, it is observed that addition of fibers compensates the reduction in the slab thickness as well as changes the failure mode of the slab from brittle to a more ductile manner.

Saturation measurement accuracy in clinical near-infrared cerebral oximeters with a 3D-printed channel array phantom

Science.gov (United States)

Afshari, Ali; Ghassemi, Pejhman; Halprin, Molly; Lin, Jonathan; Weininger, Sandy; Gandjbakhche, Amir H.; Wang, Jianting; Pfefer, Joshua

2018-02-01

Clinical cerebral oximeters based on near-infrared spectroscopy (NIRS) are a commonly used, non-invasive tool for intraoperative monitoring of hemoglobin saturation. Research to verify performance of cerebral oximeters in human subject trials has shown differences between commercially available devices. Test methods based on tissue-simulating phantoms have been proposed to augment clinical findings. While prior studies have focused on liquid phantoms, this work is aimed at developing methods based on solid polymer phantoms that are stable. Specifically, we have designed and fabricated a neonatal/pediatric head mimicking layered phantoms based on a 3D-printed cerebral matrix incorporating an array of vessel-simulating linear channels. Superficial layers incorporating homogeneous molded polydimethylsiloxane (PDMS) slabs were fabricated to represent CSF, scalp and skull regions. The cerebral matrix was filled with bovine blood desaturated with sodium dithionite to achieve oxygenation levels across the 40-90% range. Measurements were performed with a commercially available cerebral oximeter using two probes with different illumination-collection geometries, as designed for neonatal and pediatric patients. Reference measurements of samples were performed with a CO-oximeter before injection and after extraction. Results from applied cerebral oximeters indicate a strong sensitivity to the thickness of the superficial layer of the phantom. Better correlation with the reference CO-oximeter results were obtained in the superficial layer thickness of 0.8-2.5 mm range. Channel array phantoms with modular superficial layers represent a promising approach for performance testing of NIRS-based cerebral oximeters.

Phantoms and computational models in therapy, diagnosis and protection

International Nuclear Information System (INIS)

Anon.

1992-01-01

The development of realistic body phantoms and computational models is strongly dependent on the availability of comprehensive human anatomical data. This information is often missing, incomplete or not easily available. Therefore, emphasis is given in the Report to organ and body masses and geometries. The influence of age, sex and ethnic origins in human anatomy is considered. Suggestions are given on how suitable anatomical data can be either extracted from published information or obtained from measurements on the local population. Existing types of phantoms and computational models used with photons, electrons, protons and neutrons are reviewed in this Report. Specifications of those considered important to the maintenance and development of reliable radiation dosimetry and measurement are given. The information provided includes a description of the phantom or model, together with diagrams or photographs and physical dimensions. The tissues within body sections are identified and the tissue substitutes used or recommended are listed. The uses of the phantom or model in radiation dosimetry and measurement are outlined. The Report deals predominantly with phantom and computational models representing the human anatomy, with a short Section devoted to animal phantoms in radiobiology

Benchmark experiments of dose distributions in phantom placed behind iron and concrete shields at the TIARA facility

International Nuclear Information System (INIS)

Nakane, Yoshihiro; Sakamoto, Yukio; Tsuda, Shuichi

2004-01-01

To verify the calculation methods used for the evaluations of neutron dose at the radiation shielding design of the high-intensity proton accelerator facility (J-PARC), dose distributions in a plastic phantom of 30x30x30 cm 3 slab placed behind iron and concrete test shields were measured by using a tissue equivalent proportional counter for 65-MeV quasi-monoenergetic neutrons generated from the 7 Li(p,n) reactions with 68-MeV protons at the TIARA facility. Dose distributions in the phantom were calculated by using the MCNPX and the NMTC/JAM-MCNP codes with the flux-to-dose conversion coefficients prepared for the shielding design of the facility. The comparison results show the calculated results were in good agreement with the measured ones within 20%. (author)

Safety analysis on tokamak helium cooling slab fuel fusion-fission hybrid reactor

International Nuclear Information System (INIS)

Wei Renjie; Jian Hongbing

1992-01-01

The thermal analyses for steady state, depressurization and total loss of flow in the tokamak helium cooling slab fuel element fusion-fission hybrid reactor are presented. The design parameters, computed results of HYBRID program and safety evaluation for conception design are given. After all, it gives some recommendations for developing the design

Application of average adult Japanese voxel phantoms to evaluation of photon specific absorbed fractions

International Nuclear Information System (INIS)

Sato, Kaoru; Manabe, Kentaro; Endo, Akira

2012-01-01

Average adult Japanese male (JM-103) and female (JF-103) voxel (volume pixel) phantoms newly constructed at the Japan Atomic Energy Agency (JAEA) have average characteristics of body sizes and organ masses in adult Japanese. In JM-103 and JF-103, several organs and tissues were newly modeled for dose assessments based on tissue weighting factors of the 2007 Recommendations of the International Commission on Radiological Protection(ICRP). In this study, SAFs for thyroid, stomach, lungs and lymphatic nodes of JM-103 and JF-103 phantoms were calculated, and were compared with those of other adult Japanese phantoms based on individual medical images. In most cases, differences in SAFs between JM-103, JF-103 and other phantoms were about several tens percent, and was mainly attributed to mass differences of organs, tissues and contents. Therefore, it was concluded that SAFs of JM-103 and JF-103 represent those of average adult Japanese and that the two phantoms are applied to dose assessment for average adult Japanese on the basis of the 2007 Recommendations. (author)

Conversion of ICRP male reference phantom to polygon-surface phantom

Science.gov (United States)

Yeom, Yeon Soo; Han, Min Cheol; Kim, Chan Hyeong; Jeong, Jong Hwi

2013-10-01

The International Commission on Radiological Protection (ICRP) reference phantoms, developed based on computed tomography images of human bodies, provide much more realism of human anatomy than the previously used MIRD5 (Medical Internal Radiation Dose) mathematical phantoms. It has been, however, realized that the ICRP reference phantoms have some critical limitations showing a considerable amount of holes for the skin and wall organs mainly due to the nature of voxels of which the phantoms are made, especially due to their low voxel resolutions. To address this problem, we are planning to develop the polygon-surface version of ICRP reference phantoms by directly converting the ICRP reference phantoms (voxel phantoms) to polygon-surface phantoms. The objective of this preliminary study is to see if it is indeed possible to construct the high-quality polygon-surface phantoms based on the ICRP reference phantoms maintaining identical organ morphology and also to identify any potential issues, and technologies to address these issues, in advance. For this purpose, in the present study, the ICRP reference male phantom was roughly converted to a polygon-surface phantom. Then, the constructed phantom was implemented in Geant4, Monte Carlo particle transport code, for dose calculations, and the calculated dose values were compared with those of the original ICRP reference phantom to see how much the calculated dose values are sensitive to the accuracy of the conversion process. The results of the present study show that it is certainly possible to convert the ICRP reference phantoms to surface phantoms with enough accuracy. In spite of using relatively less resources (original ICRP reference phantoms, it is believed that the polygon-surface version of ICRP reference phantoms properly developed will not only provide the same or similar dose values (say, difference <5 or 10%) for highly penetrating radiations, but also provide correct dose values for the weakly penetrating

Evaluation of organ doses and specific k effective dose of 64-slice CT thorax examination using an adult anthropomorphic phantom

International Nuclear Information System (INIS)

Hashim, S.; Karim, M.K.A.; Bakar, K.A.; Sabarudin, A.; Chin, A.W; Saripan, M.I.; Bradley, D.A.

2016-01-01

The magnitude of radiation dose in computed tomography (CT) depends on the scan acquisition parameters, investigated herein using an anthropomorphic phantom (RANDO®) and thermoluminescence dosimeters (TLD). Specific interest was in the organ doses resulting from CT thorax examination, the specific k coefficient for effective dose estimation for particular protocols also being determined. For measurement of doses representing five main organs (thyroid, lung, liver, esophagus and skin), TLD-100 (LiF:Mg, Ti) were inserted into selected holes in a phantom slab. Five CT thorax protocols were investigated, one routine (R1) and four that were modified protocols (R2 to R5). Organ doses were ranked from greatest to least, found to lie in the order: thyroid>skin>lung>liver>breast. The greatest dose, for thyroid at 25 mGy, was that in use of R1 while the lowest, at 8.8 mGy, was in breast tissue using R3. Effective dose (E) was estimated using three standard methods: the International Commission on Radiological Protection (ICRP)-103 recommendation (E103), the computational phantom CT-EXPO (E(CTEXPO)) method, and the dose-length product (DLP) based approach. E103 k factors were constant for all protocols, ~8% less than that of the universal k factor. Due to inconsistency in tube potential and pitch factor the k factors from CTEXPO were found to vary between 0.015 and 0.010 for protocols R3 and R5. With considerable variation between scan acquisition parameters and organ doses, optimization of practice is necessary in order to reduce patient organ dose. - Highlights: • Using TLD-100 dosimeters and a RANDO phantom 5 CT thorax protocol organ doses were assessed. • The specific k coefficient for effective dose estimation of protocols differed with approach. • Organ dose was observed to decrease in the order: thyroid>skin>lung>liver>breast. • E103 k factors were constant for all protocols, lower by ~8% compared to the universal k factor.

Method for Bubbledeck Concrete Slab with Gaps

Directory of Open Access Journals (Sweden)

Sergiu Călin

2009-01-01

Full Text Available The composite slabs are made of BubbleDeck type slab elements with spherical gaps, poured in place on transversal and longitudinal directions. By introducing the gaps leads to a 30...50\\% lighter slab which reduces the loads on the columns, walls and foundations, and of course of the entire building. BubbleDeck slab elements are plates with ribs on two directions made of reinforced concrete or precast concrete with spherical shaped bubbles. These slab elements have a bottom and an upper concrete part connected with vertical ribs that go around the gaps.

Conversion of ICRP male reference phantom to polygon-surface phantom

International Nuclear Information System (INIS)

Yeom, Yeon Soo; Han, Min Cheol; Kim, Chan Hyeong; Jeong, Jong Hwi

2013-01-01

The International Commission on Radiological Protection (ICRP) reference phantoms, developed based on computed tomography images of human bodies, provide much more realism of human anatomy than the previously used MIRD5 (Medical Internal Radiation Dose) mathematical phantoms. It has been, however, realized that the ICRP reference phantoms have some critical limitations showing a considerable amount of holes for the skin and wall organs mainly due to the nature of voxels of which the phantoms are made, especially due to their low voxel resolutions. To address this problem, we are planning to develop the polygon-surface version of ICRP reference phantoms by directly converting the ICRP reference phantoms (voxel phantoms) to polygon-surface phantoms. The objective of this preliminary study is to see if it is indeed possible to construct the high-quality polygon-surface phantoms based on the ICRP reference phantoms maintaining identical organ morphology and also to identify any potential issues, and technologies to address these issues, in advance. For this purpose, in the present study, the ICRP reference male phantom was roughly converted to a polygon-surface phantom. Then, the constructed phantom was implemented in Geant4, Monte Carlo particle transport code, for dose calculations, and the calculated dose values were compared with those of the original ICRP reference phantom to see how much the calculated dose values are sensitive to the accuracy of the conversion process. The results of the present study show that it is certainly possible to convert the ICRP reference phantoms to surface phantoms with enough accuracy. In spite of using relatively less resources (<2 man-months), we were able to construct the polygon-surface phantom with the organ masses perfectly matching the ICRP reference values. The analysis of the calculated dose values also implies that the dose values are indeed not very sensitive to the detailed morphology of the organ models in the phantom

Overview of the ICRP/ICRU adult reference computational phantoms and dose conversion coefficients for external idealised exposures

International Nuclear Information System (INIS)

Endo, Akira; Petoussi-Henss, Nina; Zankl, Maria; Schlattl, Helmut; Bolch, Wesley E.; Eckerman, Keith F.; Hertel, Nolan E.; Hunt, John G.; Pelliccioni, Maurizio; Menzel, Hans-Georg

2014-01-01

This paper reviews the ICRP Publications 110 and 116 describing the reference computational phantoms and dose conversion coefficients for external exposures. The International Commission on Radiological Protection (ICRP) in its 2007 Recommendations made several revisions to the methods of calculation of the protection quantities. In order to implement these recommendations, the DOCAL task group of the ICRP developed computational phantoms representing the reference adult male and female and then calculated a set of dose conversion coefficients for various types of idealised external exposures. This paper focuses on the dose conversion coefficients for neutrons and investigates their relationship with the conversion coefficients of the protection and operational quantities of ICRP Publication 74. Contributing factors to the differences between these sets of conversion coefficients are discussed in terms of the changes in phantoms employed and the radiation and tissue weighting factors. This paper briefly reviews the reference computational phantoms and dose conversion coefficients for external exposures that were published jointly by ICRP and ICRU. Both these publications appeared as a consequence of the ICRP 2007 Recommendations; to implement these recommendations, the ICRP has developed reference computational phantoms representing the adult male and female. These phantoms are used to calculate reference dose conversion coefficients for external and internal sources. Using the reference phantoms and methodology consistent with the 2007 Recommendations, dose conversion coefficients for both effective doses and organ-absorbed doses for various types of idealised external exposures have been calculated. These data sets supersede the existing ICRP/ICRU data sets and expand the particle types and energy ranges. For neutrons, the new effective dose conversion coefficients become smaller compared with those in ICRP74, for energies below hundreds of keV. This is mainly

Personal dose equivalent conversion coefficients for electrons to 1 Ge V.

Science.gov (United States)

Veinot, K G; Hertel, N E

2012-04-01

In a previous paper, conversion coefficients for the personal dose equivalent, H(p)(d), for photons were reported. This note reports values for electrons calculated using similar techniques. The personal dose equivalent is the quantity used to approximate the protection quantity effective dose when performing personal dosemeter calibrations and in practice the personal dose equivalent is determined using a 30×30×15 cm slab-type phantom. Conversion coefficients to 1 GeV have been calculated for H(p)(10), H(p)(3) and H(p)(0.07) in the recommended slab phantom. Although the conversion coefficients were determined for discrete incident energies, analytical fits of the conversion coefficients over the energy range are provided using a similar formulation as in the photon results previously reported. The conversion coefficients for the personal dose equivalent are compared with the appropriate protection quantity, calculated according to the recommendations of the latest International Commission on Radiological Protection guidance. Effects of eyewear on H(p)(3) are also discussed.

A study on properties of water substitute solid phantom using EGS code

International Nuclear Information System (INIS)

Saitoh, H.; Myojoyama, A.; Tomaru, T.; Fukuda, K.; Fujisaki, T.; Abe, S.

2003-01-01

To reduce the uncertainty in the calibration of radiation beams, absorbed dose to water for high energy electrons is recommended as the standards and reference absorbed dose by AAPM Report no.51, IAEA Technical Reports no.398 and JSMP Standard dosimetry for radiotherapy 2001. In these recommendations, water is defined as the reference medium, however, the water substitute solid phantoms are discouraged. Nevertheless, when accurate chamber positioning in water is not possible, or when no waterproof chamber is available, their use is permitted at beam qualities R 50 2 (E 0 pl and fluence-scaling factors h pl of several commercially available water substitute solid phantoms were determined using EGS Monte Carlo simulation. Furthermore, the electron dosimetry using these scaling method was evaluated. As a result, it is obviously that dose-distribution in solid phantom can be converted to appropriate dose-distribution in water by means of IAEA depth-scaling. (author)

Monoenergetic Critical Parameters and Decay Constants for Small Spheres and Thin Slabs

Energy Technology Data Exchange (ETDEWEB)

Carlvik, I

1967-04-15

A method has been developed for the solution of the monoenergetic critical problem for a slab or a sphere. The method utilizes an expansion of the flux density in Legendre polynomials of the coordinate. It is equivalent to the usual variational method using powers of the coordinate, but the use of Legendre polynomials makes it possible to calculate most of the elements of the resulting matrix by means of recurrence formulae. A series of calculations has been performed for slabs and spheres with d {<=} 5, where d is the thickness of the slab or the diameter of the sphere measured in mean free paths. The critical problem is equivalent to the problem of determining the decay constant of a subcritical system with an exponentially decaying flux density. In consequence the calculations also give a series of decay constants for subcritical slabs and spheres. Comparisons with diffusion theory show that large errors can result from uncritical application of diffusion theory to small assemblies. The author would recommend that measurements on small pulsed assemblies be analyzed by means of more accurate methods, for example the present method extended to multi-group treatment of the energy dependence. The results of the calculations show clearly the interesting fact that the exponentially decaying flux of very small spheres has a minimum at the center.

Monte Carlo evaluation of the convolution/superposition algorithm of Hi-Art tomotherapy in heterogeneous phantoms and clinical cases

International Nuclear Information System (INIS)

Sterpin, E.; Salvat, F.; Olivera, G.; Vynckier, S.

2009-01-01

The reliability of the convolution/superposition (C/S) algorithm of the Hi-Art tomotherapy system is evaluated by using the Monte Carlo model TomoPen, which has been already validated for homogeneous phantoms. The study was performed in three stages. First, measurements with EBT Gafchromic film for a 1.25x2.5 cm 2 field in a heterogeneous phantom consisting of two slabs of polystyrene separated with Styrofoam were compared to simulation results from TomoPen. The excellent agreement found in this comparison justifies the use of TomoPen as the reference for the remaining parts of this work. Second, to allow analysis and interpretation of the results in clinical cases, dose distributions calculated with TomoPen and C/S were compared for a similar phantom geometry, with multiple slabs of various densities. Even in conditions of lack of lateral electronic equilibrium, overall good agreement was obtained between C/S and TomoPen results, with deviations within 3%/2 mm, showing that the C/S algorithm accounts for modifications in secondary electron transport due to the presence of a low density medium. Finally, calculations were performed with TomoPen and C/S of dose distributions in various clinical cases, from large bilateral head and neck tumors to small lung tumors with diameter of <3 cm. To ensure a ''fair'' comparison, identical dose calculation grid and dose-volume histogram calculator were used. Very good agreement was obtained for most of the cases, with no significant differences between the DVHs obtained from both calculations. However, deviations of up to 4% for the dose received by 95% of the target volume were found for the small lung tumors. Therefore, the approximations in the C/S algorithm slightly influence the accuracy in small lung tumors even though the C/S algorithm of the tomotherapy system shows very good overall behavior.

Surface Waves Propagating on Grounded Anisotropic Dielectric Slab

Directory of Open Access Journals (Sweden)

Zhuozhu Chen

2018-01-01

Full Text Available This paper investigates the characteristics of surface waves propagating on a grounded anisotropic dielectric slab. Distinct from the existing analyses that generally assume that the fields of surface wave uniformly distribute along the transverse direction of the infinitely large grounded slab, our method takes into account the field variations along the transverse direction of a finite-width slab. By solving Maxwell’s equations in closed-form, it is revealed that no pure transverse magnetic (TM or transverse electric (TE mode exists if the fields are non-uniformly distributed along the transverse direction of the grounded slab. Instead, two hybrid modes, namely quasi-TM and quasi-TE modes, are supported. In addition, the propagation characteristics of two hybrid modes supported by the grounded anisotropic slab are analyzed in terms of the slab thickness, slab width, as well as the relative permittivity tensor of the anisotropic slab. Furthermore, different methods are employed to compare the analyses, as well as to validate our derivations. The proposed method is very suitable for practical engineering applications.

Cattle cruelty and risks of meat contamination at Akinyele cattle market and slaughter slab in Oyo State, Nigeria.

Science.gov (United States)

Adeyemo, Olanike K; Adeyemi, Isaac G; Awosanya, Emmanuel J

2009-12-01

Cattle transported to the government-run cattle market and slaughter slab in Akinyele, Oyo State, Nigeria on their final voyage are facing a disturbingly cruel, filthy and unsafe environment that is also raising the risk of contamination of meat sold for human consumption. This report gives a picture of what the cattle have to go through before they are slaughtered. This study also reveals cattle awaiting slaughter in abysmal health conditions, cows pulled with extreme force towards lairage and slaughter slab. Equally disturbing is the filthy situation inside the abattoir where the risk of contamination of meat is significant. Also, poor meat handling, transportation and sales practices subject meat to contamination leading to poor quality and exposure of human consumers to health risk. Development of hygienic slaughter slab operations, improved transportation system for both livestock and meat is therefore recommended; not only for Akinyele, but all abattoirs and slaughter slabs in Nigeria.

A low-cost phantom for simple routine testing of single photon emission computed tomography (SPECT) cameras

International Nuclear Information System (INIS)

Ng, A.H.; Ng, K.H.; Dharmendra, H.; Perkins, A.C.

2009-01-01

A simple sphere test phantom has been developed for routine performance testing of SPECT systems in situations where expensive commercial phantoms may not be available. The phantom was based on a design with six universal syringe hubs set in the frame to support a circular array of six glass blown spheres of different sizes. The frame was then placed into a water-filled CT abdomen phantom and scanned with a triple head camera system (Philips IRIX TM , USA). Comparison was made with a commercially available phantom (Deluxe Jaszczak phantom). Whereas the commercial phantom demonstrates cold spot resolution, an important advantage of the sphere test phantom was that hot spot resolution could be easily measured using almost half (370 MBq) of the activity recommended for use in the commercial phantom. Results showed that the contrast increased non-linearly with sphere volume and radionuclide concentration. The phantom was found to be suitable as an inexpensive option for daily performance tests.

Nonimaging concentrators for diode-pumped slab lasers

Science.gov (United States)

Lacovara, Philip; Gleckman, Philip L.; Holman, Robert L.; Winston, Roland

1991-10-01

Diode-pumped slab lasers require concentrators for high-average power operation. We detail the properties of diode lasers and slab lasers which set the concentration requirements and the concentrator design methodologies that are used, and describe some concentrator designs used in high-average power slab lasers at Lincoln Laboratory.

Evidence of fire resistance of hollow-core slabs

DEFF Research Database (Denmark)

Hertz, Kristian Dahl; Sørensen, Lars Schiøtt; Giuliani, Luisa

is therefore going on in the Netherlands about the fire resistance of hollow-core slabs. In 2014 the producers of hollow-core slabs have published a report of a project called Holcofire containing a collection of 162 fire tests on hollow-core slabs giving for the first time an overview of the fire tests made....... The present paper analyses the evidence now available for assessment of the fire resistance of extruded hollow-core slabs. The 162 fire tests from the Holcofire report are compared against the requirements for testing from the product standard for hollow-core slabs EN1168 and knowledge about the possible......Hollow-core slabs have during the past 50 years comprised a variety of different structures with different cross-sections and reinforcement. At present the extruded hollow-core slabs without cross-reinforcement in the bottom flange and usually round or oval longitudinal channels (holes...

Flowing Air-Water Cooled Slab Nd: Glass Laser

Science.gov (United States)

Lu, Baida; Cai, Bangwei; Liao, Y.; Xu, Shifa; Xin, Z.

1989-03-01

A zig-zag optical path slab geometry Nd: glass laser cooled through flowing air-water is developed by us. Theoretical studies on temperature distribution of slab and rod configurations in the unsteady state clarify the advantages of the slab geometry laser. The slab design and processing are also reported. In our experiments main laser output characteristics, e. g. laser efficiency, polarization, far-field divergence angle as well as resonator misalignment are investigated. The slab phosphate glass laser in combination with a crossed Porro-prism resonator demonstrates a good laser performance.

The effect of blood sample positions in a water phantom at the time of irradiation on the dicentric yield

International Nuclear Information System (INIS)

Inoue, Yoshinori

1995-01-01

Blood samples of man and rabbit, placed at various distances from the surface of a water phantom with a dosimeter were exposed to 250mGy of 60 Co γ-rays. Increases in the dicentric yields in the lymphocytes were observed with increased distances from the surface of the water phantom. As a variation of the dicentric yield with increasing distance in water was found, in the experiment to obtain calibration curves for biological dosimetry, it is recommended that blood samples should be positioned at a constant distance from the surface of a water phantom at the time of irradiation. ICRU REPORT 23 recommends that the calibration measurement be carried out with an ionization chamber positioned at 5cm depth below the surface of a water phantom for 150 kV-10 MV X rays, and 137 Cs and 60 Co γ-rays. As the same reasons which determine a 5cm depth in the recommendation, should be applied to this case, it is desirable that the experiment be carried out with blood samples positioned at 5cm distance from the surface of a water phantom. (author)

Computer tomographic phantom

International Nuclear Information System (INIS)

Lonn, A.H.R.; Jacobsen, D.R.; Zech, D.J.

1988-01-01

A reference phantom for computer tomography employs a flexible member with means for urging the flexible member into contact along the curved surface of the lumbar region of a human patient. In one embodiment, the reference phantom is pre-curved in an arc greater than required. Pressure from the weight of a patient laying upon the reference phantom is effective for straightening out the curvature sufficiently to achieve substantial contact along the lumbar region. The curvature of the reference phantom may be additionally distorted by a resilient pad between the resilient phantom and a table for urging it into contact with the lumbar region. In a second embodiment of the invention, a flexible reference phantom is disposed in a slot in the top of a resilient cushion. The resilient cushion and reference phantom may be enclosed in a flexible container. A partially curved reference phantom in a slot in a resilient cushion is also contemplated. (author)

Dose distribution in organs: patient-specific phantoms versus reference phantoms

Energy Technology Data Exchange (ETDEWEB)

Lacerda, I.V.B., E-mail: isabelle.lacerda@ufpe.br [Universidade Federal de Pernambuco (UFPE), Recife (Brazil); Vieira, J.W. [Instituto Federal de Pernambuco (IFPE), Recife (Brazil); Oliveira, M.L.; Lima, F.R.A. [Centro Regional de Ciências Nucleares do Nordeste (CRCN-NE/CNEN-PB), Recife (Brazil)

2017-07-01

Discrepancies between ICRP phantoms and real patients lead to disparities on patient-dose estimations. This paper aims to compare distribution of dose in organs of male/female specific-phantoms and ICRP reference phantoms. The absorbed dose estimation was performed using the EGSnrc Monte Carlo code and a parallel source algorithm. In this work were used a patient-specific phantom for a man (1.73m/70.3kg) and another for a woman (1.63m/60.3kg) and the male and female ICRP reference phantoms. The comparison of the absorbed dose from each phantom gender was performed using the relative error. The results were expressed in terms of conversion coefficients to brain, lungs, liver and kidneys. The greatest absolute relative error between the organs of the patient-specific phantom and the reference phantom was 22.92% in the liver and 62.84% in the kidneys, respectively for man and woman. There are errors that cannot be disregarded. This paper shows the need for a specific study for each patient or for the population of each country, since there are different body types, which affects the distribution of the organ doses. (author)

Dose distribution in organs: patient-specific phantoms versus reference phantoms

International Nuclear Information System (INIS)

Lacerda, I.V.B.; Vieira, J.W.; Oliveira, M.L.; Lima, F.R.A.

2017-01-01

Discrepancies between ICRP phantoms and real patients lead to disparities on patient-dose estimations. This paper aims to compare distribution of dose in organs of male/female specific-phantoms and ICRP reference phantoms. The absorbed dose estimation was performed using the EGSnrc Monte Carlo code and a parallel source algorithm. In this work were used a patient-specific phantom for a man (1.73m/70.3kg) and another for a woman (1.63m/60.3kg) and the male and female ICRP reference phantoms. The comparison of the absorbed dose from each phantom gender was performed using the relative error. The results were expressed in terms of conversion coefficients to brain, lungs, liver and kidneys. The greatest absolute relative error between the organs of the patient-specific phantom and the reference phantom was 22.92% in the liver and 62.84% in the kidneys, respectively for man and woman. There are errors that cannot be disregarded. This paper shows the need for a specific study for each patient or for the population of each country, since there are different body types, which affects the distribution of the organ doses. (author)

0-6722 : spread prestressed concrete slab beam bridges.

Science.gov (United States)

2014-08-01

The Texas Department of Transportation uses : precast prestressed concrete slab beam bridges for : shorter-span bridges of approximately 3050 ft in : length. Conventional slab beam bridges have slab : beams placed immediately adjacent to one anoth...

Mantle wedge serpentinization effects on slab dips

Directory of Open Access Journals (Sweden)

Eh Tan

2017-01-01

Full Text Available The mechanical coupling between a subducting slab and the overlying mantle wedge is an important factor in controlling the subduction dip angle and the flow in mantel wedge. This paper investigates the role of the amount of mantle serpentinization on the subduction zone evolution. With numerical thermos-mechanical models with elasto-visco-plastic rheology, we vary the thickness and depth extent of mantle serpentinization in the mantle wedge to control the degree of coupling between the slab and mantle wedge. A thin serpentinized mantle layer is required for stable subduction. For models with stable subduction, we find that the slab dip is affected by the down-dip extent and the mantle serpentinization thickness. A critical down-dip extent exists in mantle serpentinization, determined by the thickness of the overriding lithosphere. If the down-dip extent does not exceed the critical depth, the slab is partially coupled to the overriding lithosphere and has a constant dip angle regardless of the mantle serpentinization thickness. However, if the down-dip extent exceeds the critical depth, the slab and the base of the overriding lithosphere would be separated and decoupled by a thick layer of serpentinized peridotite. This allows further slab bending and results in steeper slab dip. Increasing mantle serpentinization thickness will also result in larger slab dip. We also find that with weak mantle wedge, there is no material flowing from the asthenosphere into the serpentinized mantle wedge. All of these results indicate that serpentinization is an important ingredient when studying the subduction dynamics in the mantle wedge.

Repairing reinforced concrete slabs using composite layers

International Nuclear Information System (INIS)

Naghibdehi, M. Ghasemi; Sharbatdar, M.K.; Mastali, M.

2014-01-01

There are several strengthening methods for rehabilitation of RC structural elements. The efficiency of these methods has been demonstrated by many researchers. Due to their mechanical properties, using fibrous materials in rehabilitation applications is growing fast. Therefore, this study presents rehabilitation of slabs in such a way that plain concrete layers on top, on bottom, on the entire cross section are replaced by reinforced concrete layers. In order to reinforce the concrete, Polypropylene (PP) and steel fibers were used by 0.5%, 1% and 2% fiber volume fractions. Nineteen slabs were studied under flexural loadings and fibrous material effects on the initial crack force, the maximum loading carrying capacity, absorbed energy and ductility were investigated. The obtained results demonstrated that increasing the fiber volume fraction or using reinforced concrete layer on top, bottom, or at the entire cross section of the slabs not only always leads to improvement in the slab performance, but also sometimes debilitates the slab performance. Hence, this study will propose the best positioning of reinforced concrete layer, fiber volume fraction and fiber type to achieve the best flexural performance of slabs. - Highlights: • Using PP fibers at the bottom layer led to the best slab performance in bending. • Using steel fiber at the top layer and entire cross-section led to the best slab performance. • Maximum increase in the initial crack force and loading were obtained at 2% steel fiber. • Maximum increase in the initial crack force and loading were obtained at 1% PP fiber

Long-life slab replacement concrete : [summary].

Science.gov (United States)

2015-04-01

Concrete slab replacement projects in Florida have demonstrated a high incidence of : replacement slab cracking. Causes of cracking have not been reliably determined. University of South Florida researchers : sought to identify the factors or : param...

The internal radiation dose calculations based on Chinese mathematical phantom

International Nuclear Information System (INIS)

Wang Haiyan; Li Junli; Cheng Jianping; Fan Jiajin

2006-01-01

The internal radiation dose calculations built on Chinese facts become more and more important according to the development of nuclear medicine. the MIRD method developed and consummated by the society of Nuclear Medicine (America) is based on the European and American mathematical phantom and can't fit Chinese well. The transport of γ-ray in the Chinese mathematical phantom was simulated with Monte Carlo method in programs as MCNP4C. the specific absorbed fraction (Φ) of Chinese were calculated and the Chinese Φ database was created. The results were compared with the recommended values by ORNL. the method was proved correct by the coherence when the target organ was the same with the source organ. Else, the difference was due to the different phantom and the choice of different physical model. (authors)

Effect of kenaf fiber in reinforced concrete slab

Science.gov (United States)

Syed Mohsin, S. M.; Baarimah, A. O.; Jokhio, G. A.

2018-04-01

The effect of kenaf fibers in reinforced concrete slab with different thickness is discusses and presented in this paper. Kenaf fiber is a type of natural fiber and is added in the reinforced concrete slab to improve the structure strength and ductility. For this study, three types of mixtures were prepared with fiber volume fraction of 0%, 1% and 2%, respectively. The design compressive strength considered was 20 MPa. Six cubes were prepared to be tested at 7th and 28th day. A total of six reinforced concrete slab with two variances of thickness were also prepared and tested under four-point bending test. The differences in the thickness is to study the potential of kenaf fiber to serve as part of shear reinforcement in reinforced concrete slab that was design to fail in shear. It was observed that, addition of kenaf fiber in reinforced concrete slab improves the flexural strength and ductility of the reinforced concrete slab. In the slab with reduction in thickness, the mode of failure change from brittle to ductile with the inclusion of kenaf fiber.

Cost analysis of reinforced concrete slabs and columns

OpenAIRE

Spuś, Piotr

2013-01-01

The construction industry is increasingly looking for solutions that are both simple and effective and that provide cost savings, speed and flexibility of execution. Two-way slabs are a form of construction unique to reinforced concrete comparing with the other major structural materials. It is an efficient, economical, and widely used structural system. The present dissertation aims to analyze and compare costs between four types of slabs: waffle slab with recuperate molds, flat slabs wit...

Numerical Investigation of Slab-Column Connection by Finite Element Method

International Nuclear Information System (INIS)

Akram, T.; Shaikh, M.A.; Memon, A.A.

2007-01-01

The flat slab-on-column construction subjected to high transverse stresses concentrated at the slab-column connection can lead to a non-ductile, sudden and brittle punching failure and results in the accidental collapse of flat slab buildings. The major parameters affecting the slab-column connection are the concrete strength, slab thickness, slab reinforcement and aspect ratio of column. The application of numerical methods based on the finite element theory for solving practical tasks allow to perform virtual testing of structures and explore their behavior under load and other effects in different conditions taking into account the elastic and plastic behavior of materials, appearance and development of cracks and other damages (disintegrations), and finally to simulate the failure mechanism and its consequences. In this study, the models are developed to carry out the finite element analysis of slab- column connection using ADINA (Automatic Dynamic Incremental Nonlinear Analysis) by varying the slab thickness and slab confining reinforcement and to investigate their effect on the deflection and load carrying capacity. Test results indicate that by increasing the slab thickness, the deflection and the load carrying capacity of slab-column connection increases, more over, by increasing the slab confining reinforcement, the deflection decreases where as the load carrying capacity increases. (author)

A DXA Whole Body Composition Cross-Calibration Experience: Evaluation With Humans, Spine, and Whole Body Phantoms.

Science.gov (United States)

Krueger, Diane; Libber, Jessie; Sanfilippo, Jennifer; Yu, Hui Jing; Horvath, Blaine; Miller, Colin G; Binkley, Neil

2016-01-01

New densitometer installation requires cross-calibration for accurate longitudinal assessment. When replacing a unit with the same model, the International Society for Clinical Densitometry recommends cross-calibrating by scanning phantoms 10 times on each instrument and states that spine bone mineral density (BMD) should be within 1%, whereas total body lean, fat, and %fat mass should be within 2% of the prior instrument. However, there is limited validation that these recommendations provide adequate total body cross-calibration. Here, we report a total body cross-calibration experience with phantoms and humans. Cross-calibration between an existing and new Lunar iDXA was performed using 3 encapsulated spine phantoms (GE [GE Lunar, Madison, WI], BioClinica [BioClinica Inc, Princeton, NJ], and Hologic [Hologic Inc, Bedford, MA]), 1 total body composition phantom (BioClinica), and 30 human volunteers. Thirty scans of each phantom and a total body scan of human volunteers were obtained on each instrument. All spine phantom BMD means were similar (within 1%; g/cm2 bias) between the existing and new dual-energy X-ray absorptiometry unit. The BioClinica body composition phantom (BBCP) BMD and bone mineral content (BMC) values were within 2% with biases of 0.005 g/cm2 and -3.4 g. However, lean and fat mass and %fat differed by 4.6%-7.7% with biases of +463 g, -496 g, and -2.8%, respectively. In vivo comparison supported BBCP data; BMD and BMC were within ∼2%, but lean and fat mass and %fat differed from 1.6% to 4.9% with biases of +833 g, -860 g, and -1.1%. As all body composition comparisons exceeded the recommended 2%, the new densitometer was recalibrated. After recalibration, in vivo bias was lower (g, respectively. Similarly, BBCP lean and fat agreement improved. In conclusion, the BBCP behaves similarly, but not identical, to human in vivo measurements for densitometer cross-calibration. Spine phantoms, despite good BMD and BMC agreement, did not detect

All about FAX: a Female Adult voXel phantom for Monte Carlo calculation in radiation protection dosimetry.

Science.gov (United States)

Kramer, R; Khoury, H J; Vieira, J W; Loureiro, E C M; Lima, V J M; Lima, F R A; Hoff, G

2004-12-07

The International Commission on Radiological Protection (ICRP) has created a task group on dose calculations, which, among other objectives, should replace the currently used mathematical MIRD phantoms by voxel phantoms. Voxel phantoms are based on digital images recorded from scanning of real persons by computed tomography or magnetic resonance imaging (MRI). Compared to the mathematical MIRD phantoms, voxel phantoms are true to the natural representations of a human body. Connected to a radiation transport code, voxel phantoms serve as virtual humans for which equivalent dose to organs and tissues from exposure to ionizing radiation can be calculated. The principal database for the construction of the FAX (Female Adult voXel) phantom consisted of 151 CT images recorded from scanning of trunk and head of a female patient, whose body weight and height were close to the corresponding data recommended by the ICRP in Publication 89. All 22 organs and tissues at risk, except for the red bone marrow and the osteogenic cells on the endosteal surface of bone ('bone surface'), have been segmented manually with a technique recently developed at the Departamento de Energia Nuclear of the UFPE in Recife, Brazil. After segmentation the volumes of the organs and tissues have been adjusted to agree with the organ and tissue masses recommended by ICRP for the Reference Adult Female in Publication 89. Comparisons have been made with the organ and tissue masses of the mathematical EVA phantom, as well as with the corresponding data for other female voxel phantoms. The three-dimensional matrix of the segmented images has eventually been connected to the EGS4 Monte Carlo code. Effective dose conversion coefficients have been calculated for exposures to photons, and compared to data determined for the mathematical MIRD-type phantoms, as well as for other voxel phantoms.

Storm-time slab thickness at low latitudes

International Nuclear Information System (INIS)

Chauhan, N.S.; Gurm, H.S.

1981-01-01

The ATS-6 data for a period of 1975-76 is used for the study of slab thickness during two moderate storms (Ksub(p) - ) around the crest of the anomaly, Ahmedabad and a very great (Ksub(p) + ) outside the equatorial anomaly region, Delhi. While at Ahmedabad, on the average, the slab thickness is found to be above the frequency. Comparison of slab thickness with foF2 and the equatorial magnetic record (for Ahmedabad only) shows that the foF2 changes alone cannot be held responsible for the slab thickness variation and thus entry of the plasma flux from the plasmasphere cannot be ruled out. The pressure variation effect of storm-time heating on the slab thickness at Ahmedabad is that even for Ksub(p)=8, the thermal expansion and the contraction effects are unable to explain complete quantitative and qualitative features of the observations

SU-G-BRB-01: A Novel 3D Printed Patient-Specific Phantom for Spine SBRT Quality Assurance: Comparison of 3D Printing Techniques

Energy Technology Data Exchange (ETDEWEB)

Lee, S; Kim, M; Lee, M; Suh, T [Research Institute of Biomedical Engineering, The Catholic University of Korea, Seoul (Korea, Republic of); Department of Biomedical Engineering, The Catholic University of Korea, Seoul (Korea, Republic of)

2016-06-15

Purpose: The novel 3 dimensional (3D)-printed spine quality assurance (QA) phantoms generated by two different 3D-printing technologies, digital light processing (DLP) and Polyjet, were developed and evaluated for spine stereotactic body radiation treatment (SBRT). Methods: The developed 3D-printed spine QA phantom consisted of an acrylic body and a 3D-printed spine phantom. DLP and Polyjet 3D printers using the high-density acrylic polymer were employed to produce spine-shaped phantoms based on CT images. To verify dosimetric effects, the novel phantom was made it enable to insert films between each slabs of acrylic body phantom. Also, for measuring internal dose of spine, 3D-printed spine phantom was designed as divided laterally exactly in half. Image fusion was performed to evaluate the reproducibility of our phantom, and the Hounsfield unit (HU) was measured based on each CT image. Intensity-modulated radiotherapy plans to deliver a fraction of a 16 Gy dose to a planning target volume (PTV) based on the two 3D-printing techniques were compared for target coverage and normal organ-sparing. Results: Image fusion demonstrated good reproducibility of the fabricated spine QA phantom. The HU values of the DLP- and Polyjet-printed spine vertebrae differed by 54.3 on average. The PTV Dmax dose for the DLP-generated phantom was about 1.488 Gy higher than for the Polyjet-generated phantom. The organs at risk received a lower dose when the DLP technique was used than when the Polyjet technique was used. Conclusion: This study confirmed that a novel 3D-printed phantom mimicking a high-density organ can be created based on CT images, and that a developed 3D-printed spine phantom could be utilized in patient-specific QA for SBRT. Despite using the same main material, DLP and Polyjet yielded different HU values. Therefore, the printing technique and materials must be carefully chosen in order to accurately produce a patient-specific QA phantom.

SU-G-BRB-01: A Novel 3D Printed Patient-Specific Phantom for Spine SBRT Quality Assurance: Comparison of 3D Printing Techniques

International Nuclear Information System (INIS)

Lee, S; Kim, M; Lee, M; Suh, T

2016-01-01

Purpose: The novel 3 dimensional (3D)-printed spine quality assurance (QA) phantoms generated by two different 3D-printing technologies, digital light processing (DLP) and Polyjet, were developed and evaluated for spine stereotactic body radiation treatment (SBRT). Methods: The developed 3D-printed spine QA phantom consisted of an acrylic body and a 3D-printed spine phantom. DLP and Polyjet 3D printers using the high-density acrylic polymer were employed to produce spine-shaped phantoms based on CT images. To verify dosimetric effects, the novel phantom was made it enable to insert films between each slabs of acrylic body phantom. Also, for measuring internal dose of spine, 3D-printed spine phantom was designed as divided laterally exactly in half. Image fusion was performed to evaluate the reproducibility of our phantom, and the Hounsfield unit (HU) was measured based on each CT image. Intensity-modulated radiotherapy plans to deliver a fraction of a 16 Gy dose to a planning target volume (PTV) based on the two 3D-printing techniques were compared for target coverage and normal organ-sparing. Results: Image fusion demonstrated good reproducibility of the fabricated spine QA phantom. The HU values of the DLP- and Polyjet-printed spine vertebrae differed by 54.3 on average. The PTV Dmax dose for the DLP-generated phantom was about 1.488 Gy higher than for the Polyjet-generated phantom. The organs at risk received a lower dose when the DLP technique was used than when the Polyjet technique was used. Conclusion: This study confirmed that a novel 3D-printed phantom mimicking a high-density organ can be created based on CT images, and that a developed 3D-printed spine phantom could be utilized in patient-specific QA for SBRT. Despite using the same main material, DLP and Polyjet yielded different HU values. Therefore, the printing technique and materials must be carefully chosen in order to accurately produce a patient-specific QA phantom.

Evaluation of some water - equivalent plastics as phantom materials for electron dosimetry

International Nuclear Information System (INIS)

Mihailescu, D.; Borcia, C.

2005-01-01

In the International Code of Practice for Dosimetry TRS-398 published by the International Atomic Energy Agency (IAEA), water is recommended as the reference medium for the determination of absorbed dose for high-energy electron beams. Plastic phantoms may be used under certain circumstances (electron energy below 10 MeV, R 50 2 ) for electron beam dosimetry. In this case, a depth-scaling factor is required for the conversion of depth in solid phantoms to depth in water. A fluence-scaling factor is also necessary for converting ionization chamber readings in plastic phantom to readings in water. The aim of this paper is to calculate, using Monte Carlo simulations, the depth-scaling factors c pl and fluence-scaling factors h pl of some commercially available water substitute solid phantoms in order to evaluate their water equivalency. Two sets of calculations were performed: one for electron pencil beams and another for 10 x 10 cm 2 parallel beams, both of which are normally incident on water and solid phantoms. We used only mono-energetic beams of 6, 9, 12, 15, and 18 MeV. The results were compared with TRS-398 recommended values. In the case of pencil beams, we found that by applying the TRS-398 protocol, unacceptable uncertainties (up to 10%) were introduced in the dose distribution calculations. By contrast, TRS-398 can safely be used for 10 x 10 cm 2 beams (reference beams). In this case, uncertainties lower than 1% were obtained, what was in agreement with other published data. (authors)

Rewetting of composite slab

International Nuclear Information System (INIS)

Satapathy, A.K.; Singh, K.C.

1996-01-01

The process of re-establishment of wetting of hot surface is of practical importance in chemical, metallurgical and nuclear industries. Rewetting is considered in emergency core cooling in nuclear reactors in the event of postulated loss of coolant accident (LOCA). This paper deals with numerical solution of the two-dimensional quasi-static conduction controlled rewetting of an infinite parallel sided composite slab assuming perfect contact is maintained at the interface. On the wetted side upstream of the quench front, a constant heat transfer coefficient is assumed. The downstream of quench front and unwetted side of slab are supposed to be adiabatic. The solution gives the quench front temperature as a function of various model parameters such as Peclet number, wet side Blot number, dimensionless thickness of slab and cladding to fuel ratio of thermal conductivities. The results show that for large values of rewetting velocities, the dimensionless rewetting temperature is unaffected by fuel properties for all values of Blot numbers. (author). 7 refs., 2 tabs., 1 fig

Phantom position dependence

International Nuclear Information System (INIS)

Thorson, M.R.; Endres, G.W.R.

1981-01-01

Sensitivity of the Hanford dosimeter response to its position relative to the phantom and the neutron source has always been recognized. A thorough investigation was performed to quantify dosimeter response according to: (a) dosimeter position on phantom, (b) dosimeter distance from phantom, and (c) angular relationship of dosimeter relative to neutron source and phantom. Results were obtained for neutron irradiation at several different energies

Chinese reference human voxel phantoms for radiation protection: development, application and recent progress

International Nuclear Information System (INIS)

Pan Yuxi; Qiu Rui; Ren Li; Zhu Huanjun; Li Junli; Liu Liye

2014-01-01

This paper presents the work of constructing Chinese reference human voxel phantoms, taking Chinese reference adult female voxel model for example. In this study, a site-specific skeleton structure was built, some radiation sensitive organs were supplemented. Organ sub-segmentation was taken into account. The constructed phantoms include almost all radiation sensitive organs required by ICRP new recommendation. Masses of the organs are almost consistent with the Chinese reference data within 5%. The Chinese reference human phantoms have been applied both in internal dosimetry and external dosimetry. The results provide fundamental data for Chinese radiation dosimetry. In addition, the newly established detailed breast model and micro-bone model were introduced. (authors)

TECHNOLOGY FOR INSTALLATION OF REINFORCED CONCRETE FLOOR SLABS LIGHTENED BY CORE DRIVERS WITH PRELIMINARY REINFORCEMENT STRESS

Directory of Open Access Journals (Sweden)

S. N. Leonovich

2015-01-01

Full Text Available The paper presents technology for installation of floor slabs lightened by plastic core drivers which are preliminary stressed under construction conditions.  Efficiency of such constructive solution is justified by the action of preliminary concrete compression in the tensile zone while reducing structure dead weight due to void arrangement.  The paper provides classification of systems for preliminary stress and contains recommendations on selection of the system depending on peculiariar features of the designed construction.  Main products and materials required for execution of works , requirements to stressed wire rope reinforcement, its main characteristics have been considered in the paper.Principal diagram of the lightened preliminary stressed slab stipulates arrangement of so called  dummy caisson. Strands of reinforcement ropes are located within the framework of bars passing over supporting structures (over vertical bearing structures of  the framework and voids are formed in the cells between bars by laying hollow plastic items joined together by a cage. The paper presents technological sequence of operations required for arrangement of the lightened preliminary stressed slab, schemes for equipment arrangement and characteristics of the applied devices and units (pushing device for reinforcement ropes, hydraulic jack with delivery hydraulic pump, mixing station, injection pump and others.  Recommendations have been given for execution of works in cold weather. The paper considers problems pertaining to control quality of the materials and items which are supplied to a construction site and directly execution of works on preliminary stress of a cellular slab.The executed analysis of technology permits to conclude that it is characterized by high level of applicability for import substitution. It is necessary to consider the possibility to apply the technology at objects of various application while comparing it with other

Control of exceptional points in photonic crystal slabs

DEFF Research Database (Denmark)

Kaminski, Piotr Marek; Taghizadeh, Alireza; Breinbjerg, Olav

2017-01-01

Various ways of controlling the extent of the ring of exceptional points in photonic crystal slabs are investigated. The extent of the ring in photonic crystal slabs is found to vary with the thickness of the slab. This enables recovery of Dirac cones in open, non-Hermitian systems, such as a pho...

Analysis of Double Skin Composite Slabs

Directory of Open Access Journals (Sweden)

Husain M. Husain

2018-03-01

Full Text Available This paper deals with finite element modeling of the ultimate load behavior of double skin composite (DSC slabs. In a DSC slab, shear connectors in the form of nut bolt technique studs are used to transfer shear between the outer skin made of steel plates and the concrete core. The current study is based on finite element analysis using ANSYS Version 11 APDL release computer program. Experimental programmes were carried out by the others, two simply supported DSC beams were tested until failure under a concentrated load applied at the center. These test specimens were analyzed by the finite element method and the analyses have shown that these slabs displayed a high degree of flexural characteristics, ultimate strength, and ductility. The close agreement has been observed between the finite element and experimental results for ultimate loads and load–deflection responses. The finite element model was thus found to be capable of predicting the behavior of DSC slabs accurately.

CAISSON TYPE HOLLOW FLOOR SLABS OF MONOLITHIC MULTI-STOREYED BUILDINGS

Directory of Open Access Journals (Sweden)

Malakhova Anna Nikolaevna

2016-06-01

Full Text Available One of the disadvantages of building structures made of reinforced concrete is their considerable weight. One of the trends to decrease the weight of concrete structures, including floor slabs, is the arrangement of voids in the cross-sectional building structures. In Russian and foreign practice paper, cardboard and plastic tubes has been used for creation of voids in the construction of monolithic floor slabs. Lightweight concretes were also used for production of precast hollow core floor slabs. The article provides constructive solutions of precast hollow core floor slabs and solid monolithic slabs that were used in the construction of buildings before wide use of large precast hollow core floor slabs. The article considers the application of caisson hollow core floor slabs for modern monolithic multi-storeyed buildings. The design solutions of such floor slabs, experimental investigations and computer modeling of their operation under load were described in this article. The comparative analysis of the calculation results of computer models of a hollow slabs formed of rod or plastic elements showed the similarity of calculation results.

Calculating seismic of slabs ITA NNP Garona

International Nuclear Information System (INIS)

Ezeberry, J. I.; Guerrero, A.; Gamarra, J.; Beltran, F.

2014-01-01

This article describes the methodology that Idom has employed to perform the seismic evaluation of slabs within the ITA project of the NPP Santa Maria de Garona. Seismic calculations that have been conducted include consideration of the effects of the interaction of soil structure as well as the possible take-off containers with respect to slab during the earthquake. Therefore, the main contribution of the work is the study of the coupling of rolling containers with the flexibility of the whole ground-slab For calculations has been used ABAQUS/Explicit program, allowing to solve effectively the nonlinearities listed above using explicit integration algorithms over time. The results of the calculations reflect the importance of jointly analyse the seismic responses of slab and containers. (Author)

Area Factor Determinations for an Industrial Worker Exposed to a Concrete Slab End-State

International Nuclear Information System (INIS)

Jannik, G. Timothy; Lee, Patricia L.; Farfan, Eduardo B.; Roach, Jesse L.

2008-01-01

The U.S. Department of Energy's (DOE) Savannah River Site (SRS) is decommissioning many of its excess facilities through removal of the facility structures leaving only the concrete-slab foundations in place. Site-specific, risk-based derived concentration guideline levels (DCGLs) for radionuclides have been determined for a future industrial worker potentially exposed to residual contamination on these concrete slabs as described in Jannik. These risk-based DCGLs were estimated for an exposure area of 100 m 2 . During deactivation and decommissioning (D and D) operations at SRS, the need for area factors for larger and smaller contaminated areas arose. This paper compares the area factors determined for an industrial worker exposed to a concrete slab end-state for several radionuclides of concern at SRS with 1) the illustrative area factors provided in MARSSIM, 2) the area correction factors provided in the U.S. Environmental Protection Agency's (EPA) Soil Screening Guidance, and 3) the hot spot criterion for field application provided in the RESRAD User's Manual. The purpose of this site-specific assessment is to determine if any of the recommended area factors provided in the guidance documents could be utilized at SRS for field applications of the industrial worker DCGLs. Results show the area factors that were determined for an SRS industrial worker exposed to concrete slab end-states for the common radionuclides provided in the referenced guidance documents. In addition to the SRS site-specific area factors, the following area factors are provided for comparison: - Illustrative examples of outdoor area dose factors (MARSSIM); - Area correction factors as a function of source area (Soil Screening Guidance). Note: the area correction factors were inverted to correspond to a DCGL area factor. - Recommended area correction factors as a function of source area (Soil Screening Guidance); - Ranges for hot spot multiplication factors (RESRAD). As it can be seen

Photon transport in thin disordered slabs

Indian Academy of Sciences (India)

We examine using Monte Carlo simulations, photon transport in optically `thin' slabs whose thickness is only a few times the transport mean free path *, with particles of different scattering anisotropies. The confined geometry causes an auto-selection of only photons with looping paths to remain within the slab.

Monte Carlo evaluation of the convolution/superposition algorithm of Hi-Art tomotherapy in heterogeneous phantoms and clinical cases

Energy Technology Data Exchange (ETDEWEB)

Sterpin, E.; Salvat, F.; Olivera, G.; Vynckier, S. [Department of Radiotherapy, Saint-Luc University Hospital, Universite Catholique de Louvain, 10 Avenue Hippocrate, 1200 Brussels (Belgium); Facultat de Fisica (ECM), Universitat de Barcelona, Diagonal 647, 08028 Barcelona (Spain); Tomotherapy Inc., 1240 Deming Way, Madison, Wisconsin 53717 and Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53705 (United States); Department of Radiotherapy, Saint-Luc University Hospital, Universite Catholique de Louvain, 10 Avenue Hippocrate, 1200 Brussels (Belgium)

2009-05-15

The reliability of the convolution/superposition (C/S) algorithm of the Hi-Art tomotherapy system is evaluated by using the Monte Carlo model TomoPen, which has been already validated for homogeneous phantoms. The study was performed in three stages. First, measurements with EBT Gafchromic film for a 1.25x2.5 cm{sup 2} field in a heterogeneous phantom consisting of two slabs of polystyrene separated with Styrofoam were compared to simulation results from TomoPen. The excellent agreement found in this comparison justifies the use of TomoPen as the reference for the remaining parts of this work. Second, to allow analysis and interpretation of the results in clinical cases, dose distributions calculated with TomoPen and C/S were compared for a similar phantom geometry, with multiple slabs of various densities. Even in conditions of lack of lateral electronic equilibrium, overall good agreement was obtained between C/S and TomoPen results, with deviations within 3%/2 mm, showing that the C/S algorithm accounts for modifications in secondary electron transport due to the presence of a low density medium. Finally, calculations were performed with TomoPen and C/S of dose distributions in various clinical cases, from large bilateral head and neck tumors to small lung tumors with diameter of <3 cm. To ensure a ''fair'' comparison, identical dose calculation grid and dose-volume histogram calculator were used. Very good agreement was obtained for most of the cases, with no significant differences between the DVHs obtained from both calculations. However, deviations of up to 4% for the dose received by 95% of the target volume were found for the small lung tumors. Therefore, the approximations in the C/S algorithm slightly influence the accuracy in small lung tumors even though the C/S algorithm of the tomotherapy system shows very good overall behavior.

Air slab-correction for Γ-ray attenuation measurements

Science.gov (United States)

Mann, Kulwinder Singh

2017-12-01

Gamma (γ)-ray shielding behaviour (GSB) of a material can be ascertained from its linear attenuation coefficient (μ, cm-1). Narrow-beam transmission geometry is required for μ-measurement. In such measurements, a thin slab of the material has to insert between point-isotropic γ-ray source and detector assembly. The accuracy in measurements requires that sample's optical thickness (OT) remain below 0.5 mean free path (mfp). Sometimes it is very difficult to produce thin slab of sample (absorber), on the other hand for thick absorber, i.e. OT >0.5 mfp, the influence of the air displaced by it cannot be ignored during μ-measurements. Thus, for a thick sample, correction factor has been suggested which compensates the air present in the transmission geometry. The correction factor has been named as an air slab-correction (ASC). Six samples of low-Z engineering materials (cement-black, clay, red-mud, lime-stone, cement-white and plaster-of-paris) have been selected for investigating the effect of ASC on μ-measurements at three γ-ray energies (661.66, 1173.24, 1332.50 keV). The measurements have been made using point-isotropic γ-ray sources (Cs-137 and Co-60), NaI(Tl) detector and multi-channel-analyser coupled with a personal computer. Theoretical values of μ have been computed using a GRIC2-toolkit (standardized computer programme). Elemental compositions of the samples were measured with Wavelength Dispersive X-ray Fluorescence (WDXRF) analyser. Inter-comparison of measured and computed μ-values, suggested that the application of ASC helps in precise μ-measurement for thick samples of low-Z materials. Thus, this hitherto widely ignored ASC factor is recommended to use in similar γ-ray measurements.

Influence of slab connection in case of expanded concrete pavements

OpenAIRE

Deluka-Tibljaš, Aleksandra; Prager, Andrija; Rukavina, Tatjana

2002-01-01

Load transfer from the stressed slab to the neighboring unstressed slab is analyzed in order to establish possibilities for stress reduction in concrete. The contact between slabs is established by means of reinforcing steel shear studs while the influence of friction in the concrete to concrete contact is neglected. The influence of slab thickness, slab cross-section and spacing of shear studs is analyzed, and the expansion joint movement due to change in temperature is studied. Conditions e...

Coffered slabs as a perspective type of the reinforced concrete structures

OpenAIRE

Kibkalo Anton; Volkov Mikhail; Vodolagina Anna; Murgul Vera

2016-01-01

The article discusses coffered slabs. In this paper considered the technology of arrangement of this slabs. Cast-in-place and precast ways of construction of coffered slab are reviewed. Сast-in-place and precast coffered slabs has been analysed in this article. Among other things construction of coffered slabs has an economical and technical advantages.

Coffered slabs as a perspective type of the reinforced concrete structures

Directory of Open Access Journals (Sweden)

Kibkalo Anton

2016-01-01

Full Text Available The article discusses coffered slabs. In this paper considered the technology of arrangement of this slabs. Cast-in-place and precast ways of construction of coffered slab are reviewed. Сast-in-place and precast coffered slabs has been analysed in this article. Among other things construction of coffered slabs has an economical and technical advantages.

Fire resistance of extruded hollow-core slabs

DEFF Research Database (Denmark)

Hertz, Kristian Dahl; Sørensen, Lars Schiøtt; Giuliani, Luisa

2017-01-01

to the structural codes with data derived from a standard fire test and from a thorough examination of the comprehensive test documentation available on fire exposed hollow-core slabs. Findings – Mechanisms for loss of load-bearing capacity are clarified, and evidence of the fire resistance is found. Originality......Purpose – Prefabricated extruded hollow-core slabs are preferred building components for floor structures in several countries. It is therefore important to be able to document the fire resistance of these slabs proving fulfilment of standard fire resistance requirements of 60 and 120 min found...... in most national building regulations. The paper aims to present a detailed analysis of the mechanisms responsible for the loss of loadbearing capacity of hollow-core slabs when exposed to fire. Design/methodology/approach – Furthermore, it compares theoretica calculation and assessment according...

Material-specific Conversion Factors for Different Solid Phantoms Used in the Dosimetry of Different Brachytherapy Sources

Directory of Open Access Journals (Sweden)

Sedigheh Sina

2015-07-01

Full Text Available Introduction Based on Task Group No. 43 (TG-43U1 recommendations, water phantom is proposed as a reference phantom for the dosimetry of brachytherapy sources. The experimental determination of TG-43 parameters is usually performed in water-equivalent solid phantoms. The purpose of this study was to determine the conversion factors for equalizing solid phantoms to water. Materials and Methods TG-43 parameters of low- and high-energy brachytherapy sources (i.e., Pd-103, I-125 and Cs-137 were obtained in different phantoms, using Monte Carlo simulations. The brachytherapy sources were simulated at the center of different phantoms including water, solid water, poly(methyl methacrylate, polystyrene and polyethylene. Dosimetric parameters such as dose rate constant, radial dose function and anisotropy function of each source were compared in different phantoms. Then, conversion factors were obtained to make phantom parameters equivalent to those of water. Results Polynomial coefficients of conversion factors were obtained for all sources to quantitatively compare g(r values in different phantom materials and the radial dose function in water. Conclusion Polynomial coefficients of conversion factors were obtained for all sources to quantitatively compare g(r values in different phantom materials and the radial dose function in water.

Structural Test and Analysis of RC Slab After Fire Loading

International Nuclear Information System (INIS)

Chung, Chulhun; Im, Cho Rong; Park, Jaegyun

2013-01-01

In the present study the behavior of fire and the residual strength of fire-ignited RC slabs are investigated by experimental tests and numerical simulations. The fire tests of RC slabs were carried out in a furnace using the ISO 834 standard fire. The load capacity of the cooled RC slabs that were not loaded during the fire tests was evaluated by additional 3 point bending tests. The influence of the proportion of PP (polypropylene) fibers in the RC slabs on the structural behavior of the RC slabs after the fire loading was investigated. The results of the fire tests showed that the maximum temperature of concrete with PP fiber was lower than that of concrete without PP fiber. As the concrete was heated, the ultimate compressive strength decreased and the ultimate strain increased. The load-deflection relations of RC slabs after fire loading were compared by using existing stress-strain-temperature models. The comparison between the numerical analysis and the experimental tests showed that some numerical analyses were reliable and therefore, can be applied to evaluate the ultimate load of RC slabs after fire loading. The ultimate load capacity after cooling down the RC slabs without PP fiber showed a considerable reduction from that of the RC slabs with PP fiber

Structural Test and Analysis of RC Slab After Fire Loading

Energy Technology Data Exchange (ETDEWEB)

Chung, Chulhun; Im, Cho Rong; Park, Jaegyun [Dankook Univ., Yongin (Korea, Republic of)

2013-04-15

In the present study the behavior of fire and the residual strength of fire-ignited RC slabs are investigated by experimental tests and numerical simulations. The fire tests of RC slabs were carried out in a furnace using the ISO 834 standard fire. The load capacity of the cooled RC slabs that were not loaded during the fire tests was evaluated by additional 3 point bending tests. The influence of the proportion of PP (polypropylene) fibers in the RC slabs on the structural behavior of the RC slabs after the fire loading was investigated. The results of the fire tests showed that the maximum temperature of concrete with PP fiber was lower than that of concrete without PP fiber. As the concrete was heated, the ultimate compressive strength decreased and the ultimate strain increased. The load-deflection relations of RC slabs after fire loading were compared by using existing stress-strain-temperature models. The comparison between the numerical analysis and the experimental tests showed that some numerical analyses were reliable and therefore, can be applied to evaluate the ultimate load of RC slabs after fire loading. The ultimate load capacity after cooling down the RC slabs without PP fiber showed a considerable reduction from that of the RC slabs with PP fiber.

Overview of the ICRP/ICRU adult reference computational phantoms and dose conversion coefficients for external idealised exposures

CERN Document Server

Endo, A; Zankl, M; Bolch, W E; Eckerman, K F; Hertel, N E; Hunt, J G; Pelliccioni, M; Schlattl, H; Menzel, H-G

2014-01-01

This paper reviews the ICRP Publications 110 and 116 describing the reference computational phantoms and dose conversion coefficients for external exposures. The International Commission on Radiological Protection (ICRP) in its 2007 Recommendations made several revisions to the methods of calculation of the protection quantities. In order to implement these recommendations, the DOCAL task group of the ICRP developed computational phantoms representing the reference adult male and female and then calculated a set of dose conversion coefficients for various types of idealised external exposures. This paper focuses on the dose conversion coefficients for neutrons and investigates their relationship with the conversion coefficients of the protection and operational quantities of ICRP Publication 74. Contributing factors to the differences between these sets of conversion coefficients are discussed in terms of the changes in phantoms employed and the radiation and tissue weighting factors.

Estimation of the Reliability of Plastic Slabs

DEFF Research Database (Denmark)

Pirzada, G. B. : Ph.D.

In this thesis, work related to fundamental conditions has been extended to non-fundamental or the general case of probabilistic analysis. Finally, using the ss-unzipping technique a door has been opened to system reliability analysis of plastic slabs. An attempt has been made in this thesis...... to give a probabilistic treatment of plastic slabs which is parallel to the deterministic and systematic treatment of plastic slabs by Nielsen (3). The fundamental reason is that in Nielsen (3) the treatment is based on a deterministic modelling of the basic material properties for the reinforced...

Experimental and theoretical investigation of column - flat slab joint ductility

International Nuclear Information System (INIS)

Iskhakov, I.; Ribakov, Y.; Shah, A.

2009-01-01

Most modern seismic codes use ductility as one of the basic design parameters. Actually, ductility defines the ability of a structure or its elements to absorb energy by plastic deformations. Until the end of the previous century ductility was defined qualitatively. Most research works related to ductility are focused on structural elements' sections. This study was aimed at complex experimental and theoretical investigation of flat slab-column joints ductility. It is one of the first attempts to obtain quantitative values of joint's ductility for the case of high strength concrete columns and normal strength concrete slabs. It was shown that the flat slab-column joint is a three-dimension (3D) element and its ductility in horizontal and vertical directions are different. This is the main difference between ductility of elements and joint ductility. In case of flat slab-column joints, essential contribution to joint's ductility can be obtained due to the slab's confining effect. Based on experimental data, the authors demonstrate that flat slab-column joint's ductility depends on the joint's confining effect in two horizontal and vertical directions. Furthermore, the influence of slab load intensity and slab reinforcement ratio on the joint's ductility is performed in this study. It is also demonstrated that the effect of the ratio between the slab thickness and the column's section dimension on the ductility parameter is significant. Equations for obtaining a quantitative value of a flat slab-column joint's ductility parameter were developed.

FABRICATION OF TISSUE-SIMULATIVE PHANTOMS AND CAPILLARIES AND THEIR INVESTIGATION BY OPTICAL COHERENCE TOMOGRAPHY TECHNIQUES

Directory of Open Access Journals (Sweden)

A. V. Bykov

2013-03-01

Full Text Available Methods of tissue-simulative phantoms and capillaries fabrication from PVC-plastisol and silicone for application as test-objects in optical coherence tomography (OCT and skin and capillary emulation are considered. Comparison characteristics of these materials and recommendations for their application are given. Examples of phantoms visualization by optical coherence tomography method are given. Possibility of information using from B-scans for refractive index evaluation is shown.

Strengthening of RC bridge slabs using CFRP sheets

Directory of Open Access Journals (Sweden)

Fahmy A. Fathelbab

2014-12-01

Full Text Available Many old structures became structurally insufficient to carry the new loading conditions requirements. Moreover, they suffer from structural degradation, reinforcement steel bars corrosion, bad weather conditions…etc. Many official authorities in several countries had recognized many old bridges and buildings as structurally deficient by today’s standards. Due to these reasons, structural strengthening became an essential requirement and different strengthening techniques appeared in market. Fiber Reinforced Polymer (FRP strengthening techniques established a good position among all other techniques, giving excellent structural results, low time required and moderate cost compared with the other techniques. The main purpose of this research is to study analytically the strengthening of a reinforced concrete bridge slabs due to excessive loads, using externally bonded FRP sheets technique. A commercial finite element program ANSYS was used to perform a structural linear and non-linear analysis for strengthened slab models using several schemes of FRP sheets. A parametric study was performed to evaluate analytically the effect of changing both FRP stiffness and FRP schemes in strengthening RC slabs. Comparing the results with control slab (reinforced concrete slab without strengthening it is obvious that attaching FRP sheets to the RC slab increases its capacity and enhances the ductility/toughness.

Phantom pain and phantom sensations in upper limb amputees : an epidemiological study

NARCIS (Netherlands)

Kooijman, CM; Dijkstra, PU; Geertzen, JHB; Elzinga, A; van der Schans, CP

Phantom pain in subjects with an amputated limb is a well-known problem. However, estimates of the prevalence of phantom pain differ considerably in the literature. Various factors associated with phantom pain have been described including pain before the amputation, gender, dominance, and time

Individual virtual phantom reconstruction for organ dosimetry based on standard available phantoms

International Nuclear Information System (INIS)

Babapour Mofrad, F.; Aghaeizadeh Zoroofi, R.; Abbaspour Tehran Fard, A.; Akhlaghpoor, Sh.; Chen, Y. W.; Sato, Y.

2010-01-01

In nuclear medicine application often it is required to use computational methods for evaluation of organ absorbed dose. Monte Carlo Simulation and phantoms have been used in many works before. The shape, size and volume In organs are varied, and this variation will produce error in dose calculation if no correction is applied. Materials and Methods: A computational framework for constructing individual phantom for dosimetry was performed on five liver CT scan data sets of Japanese normal individuals. The Zubal phantom was used as an original phantom to be adjusted by each individual data set. This registration was done by Spherical Harmonics and Thin-Plate Spline methods. Hausdorff distance was calculated for each case. Results: Result of Hausdorff distance for five lndividual phantoms showed that before registration ranged from 140.9 to 192.1, and after registration it changed to 52.5 to 76.7. This was caused by Index similarity ranged from %56.4 to %70.3. Conclusion: A new and automatic three-dimensional (3D) phantom construction approach was-suggested for individual internal dosimetry simulation via Spherical Harmonics and Thin-Plate Spline methods. The results showed that the Individual comparable phantom can be calculated with acceptable accuracy using geometric registration. This method could be used for race-specific statistical phantom modeling with major application in nuclear medicine for absorbed dose calculation.

Quality assurance applied to mammographic equipments using phantoms and software for its evaluation

Energy Technology Data Exchange (ETDEWEB)

Mayo, Patricia, E-mail: p.mayo@titaniast.co [Titania Servicios Tecnologicos S.L., Grupo Dominguis, Apartado 46015, Valencia (Spain); Rodenas, Francisco [Departamento de Matematica Aplicada, Universidad Politecnica de Valencia, Apartado 46022, Valencia (Spain); Manuel Campayo, Juan [Hospital Clinico Universitario de Valencia, Avda. Blasco Ibanez, Apartado 46017, Valencia (Spain); Verdu, Gumersido [Departamento de Ingenieria Quimica y Nuclear, Universidad Politecnica de Valencia, Apartado 46022, Valencia (Spain)

2010-07-21

The image quality assessment in radiographic equipments is a very important item for a complete quality control of the radiographic image chain. The periodic evaluation of the radiographic image quality must guarantee the constancy of this quality to carry out a suitable diagnosis. Mammographic phantom images are usually used to study the quality of images obtained by determined mammographic equipment. The digital image treatment techniques allow to carry out an automatic analysis of the phantom image. In this work we apply some techniques of digital image processing to analyze in an automatic way the image quality of mammographic phantoms, namely CIRS SP01 and RACON for different varying conditions of the mammographic equipment. The CIRS SP01 phantom is usually used in analogic mammographic equipments and the RACON phantom has been specifically developed by authors to be applied to acceptance and constancy tests of the image quality in digital radiographic equipments following recommendations of international associations. The purpose of this work consists in analyzing the image quality for both phantoms by means of an automatic software utility. This analysis allows us to study the functioning of the image chain of the mammographic system in an objective way, so an abnormal functioning of the radiographic equipment might be detected.

Quality assurance applied to mammographic equipments using phantoms and software for its evaluation

International Nuclear Information System (INIS)

Mayo, Patricia; Rodenas, Francisco; Manuel Campayo, Juan; Verdu, Gumersido

2010-01-01

The image quality assessment in radiographic equipments is a very important item for a complete quality control of the radiographic image chain. The periodic evaluation of the radiographic image quality must guarantee the constancy of this quality to carry out a suitable diagnosis. Mammographic phantom images are usually used to study the quality of images obtained by determined mammographic equipment. The digital image treatment techniques allow to carry out an automatic analysis of the phantom image. In this work we apply some techniques of digital image processing to analyze in an automatic way the image quality of mammographic phantoms, namely CIRS SP01 and RACON for different varying conditions of the mammographic equipment. The CIRS SP01 phantom is usually used in analogic mammographic equipments and the RACON phantom has been specifically developed by authors to be applied to acceptance and constancy tests of the image quality in digital radiographic equipments following recommendations of international associations. The purpose of this work consists in analyzing the image quality for both phantoms by means of an automatic software utility. This analysis allows us to study the functioning of the image chain of the mammographic system in an objective way, so an abnormal functioning of the radiographic equipment might be detected.

General analysis of slab lasers using geometrical optics.

Science.gov (United States)

Chung, Te-yuan; Bass, Michael

2007-02-01

A thorough and general geometrical optics analysis of a slab-shaped laser gain medium is presented. The length and thickness ratio is critical if one is to achieve the maximum utilization of absorbed pump power by the laser light in such a medium; e.g., the fill factor inside the slab is to be maximized. We point out that the conditions for a fill factor equal to 1, laser light entering and exiting parallel to the length of the slab, and Brewster angle incidence on the entrance and exit faces cannot all be satisfied at the same time. Deformed slabs are also studied. Deformation along the width direction of the largest surfaces is shown to significantly reduce the fill factor that is possible.

Behaviors of the percentage depth dose curves along the beam axis of a phantom filled with different clinical PTO objects, a Monte Carlo Geant4 study

International Nuclear Information System (INIS)

EL Bakkali, Jaafar; EL Bardouni, Tarek; Safavi, Seyedmostafa; Mohammed, Maged; Saeed, Mroan

2016-01-01

The aim of this work is to assess the capabilities of Monte Carlo Geant4 code to reproduce the real percentage depth dose (PDD) curves generated in phantoms which mimic three important clinical treatment situations that include lung slab, bone slab, bone-lung slab geometries. It is hoped that this work will lead us to a better understanding of dose distributions in an inhomogeneous medium, and to identify any limitations of dose calculation algorithm implemented in the Geant4 code. For this purpose, the PDD dosimetric functions associated to the three clinical situations described above, were compared to one produced in a homogeneous water phantom. Our results show, firstly, that the Geant4 simulation shows potential mistakes on the shape of the calculated PDD curve of the first physical test object (PTO), and it is obviously not able to successfully predict dose values in regions near to the boundaries between two different materials. This is, surely due to the electron transport algorithm and it is well-known as the artifacts at interface phenomenon. To deal with this issue, we have added and optimized the StepMax parameter to the dose calculation program; consequently the artifacts due to the electron transport were quasi disappeared. However, the Geant4 simulation becomes painfully slow when we attempt to completely resolve the electron artifact problems by considering a smaller value of an electron StepMax parameter. After electron transport optimization, our results demonstrate the medium-level capabilities of the Geant4 code to modeling dose distribution in clinical PTO objects. - Highlights: • Assessment of the capabilities of Geant4 code to reproduce the PDD curves in heterogeneities. • Resolving artifacts due to the electron transport. • Understanding in dose distribution differences in interfaces which include water, bone, and lung interfaces.

Untangling Slab Dynamics Using 3-D Numerical and Analytical Models

Science.gov (United States)

Holt, A. F.; Royden, L.; Becker, T. W.

2016-12-01

Increasingly sophisticated numerical models have enabled us to make significant strides in identifying the key controls on how subducting slabs deform. For example, 3-D models have demonstrated that subducting plate width, and the related strength of toroidal flow around the plate edge, exerts a strong control on both the curvature and the rate of migration of the trench. However, the results of numerical subduction models can be difficult to interpret, and many first order dynamics issues remain at least partially unresolved. Such issues include the dominant controls on trench migration, the interdependence of asthenospheric pressure and slab dynamics, and how nearby slabs influence each other's dynamics. We augment 3-D, dynamically evolving finite element models with simple, analytical force-balance models to distill the physics associated with subduction into more manageable parts. We demonstrate that for single, isolated subducting slabs much of the complexity of our fully numerical models can be encapsulated by simple analytical expressions. Rates of subduction and slab dip correlate strongly with the asthenospheric pressure difference across the subducting slab. For double subduction, an additional slab gives rise to more complex mantle pressure and flow fields, and significantly extends the range of plate kinematics (e.g., convergence rate, trench migration rate) beyond those present in single slab models. Despite these additional complexities, we show that much of the dynamics of such multi-slab systems can be understood using the physics illuminated by our single slab study, and that a force-balance method can be used to relate intra-plate stress to viscous pressure in the asthenosphere and coupling forces at plate boundaries. This method has promise for rapid modeling of large systems of subduction zones on a global scale.

A systematic approach towards the objective evaluation of low-contrast performance in MDCT: Combination of a full-reference image fidelity metric and a software phantom

International Nuclear Information System (INIS)

Falck, Christian von; Rodt, Thomas; Waldeck, Stephan; Hartung, Dagmar; Meyer, Bernhard; Wacker, Frank; Shin, Hoen-oh

2012-01-01

Objectives: To assess the feasibility of an objective approach for the evaluation of low-contrast detectability in multidetector computed-tomography (MDCT) by combining a virtual phantom containing simulated lesions with an image quality metric. Materials and methods: A low-contrast phantom containing hypodense spheric lesions (−20 HU) was scanned on a 64-slice MDCT scanner at 4 different dose levels (25, 50, 100, 200 mAs). In addition, virtual round hypodense low-contrast lesions (20 HU object contrast) based on real CT data were inserted into the lesion-free section of the datasets. The sliding-thin-slab algorithm was applied to the image data with an increasing slice-thickness from 1 to 15 slices. For each dataset containing simulated lesions a lesion-free counterpart was reconstructed and post-processed in the same manner. The low-contrast performance of all datasets containing virtual lesions was determined using a full-reference image quality metric (modified multiscale structural similarity index, MS-SSIM*). The results were validated against a reader-study of the real lesions. Results: For all dose levels and lesion sizes there was no statistically significant difference between the low-contrast performance as determined by the image quality metric when compared to the reader study (p < 0.05). The intraclass correlation coefficient was 0.72, 0.82, 0.90 and 0.84 for lesion diameters of 4 mm, 5 mm, 8 mm and 10 mm, respectively. The use of the sliding-thin-slab algorithm improves lesion detectability by a factor ranging from 1.15 to 2.69 when compared with the original axial slice (0.625 mm). Conclusion: The combination of a virtual phantom and a full-reference image quality metric enables a systematic, automated and objective evaluation of low-contrast detectability in MDCT datasets and correlates well with the judgment of human readers.

Visualizing Three-dimensional Slab Geometries with ShowEarthModel

Science.gov (United States)

Chang, B.; Jadamec, M. A.; Fischer, K. M.; Kreylos, O.; Yikilmaz, M. B.

2017-12-01

Seismic data that characterize the morphology of modern subducted slabs on Earth suggest that a two-dimensional paradigm is no longer adequate to describe the subduction process. Here we demonstrate the effect of data exploration of three-dimensional (3D) global slab geometries with the open source program ShowEarthModel. ShowEarthModel was designed specifically to support data exploration, by focusing on interactivity and real-time response using the Vrui toolkit. Sixteen movies are presented that explore the 3D complexity of modern subduction zones on Earth. The first movie provides a guided tour through the Earth's major subduction zones, comparing the global slab geometry data sets of Gudmundsson and Sambridge (1998), Syracuse and Abers (2006), and Hayes et al. (2012). Fifteen regional movies explore the individual subduction zones and regions intersecting slabs, using the Hayes et al. (2012) slab geometry models where available and the Engdahl and Villasenor (2002) global earthquake data set. Viewing the subduction zones in this way provides an improved conceptualization of the 3D morphology within a given subduction zone as well as the 3D spatial relations between the intersecting slabs. This approach provides a powerful tool for rendering earth properties and broadening capabilities in both Earth Science research and education by allowing for whole earth visualization. The 3D characterization of global slab geometries is placed in the context of 3D slab-driven mantle flow and observations of shear wave splitting in subduction zones. These visualizations contribute to the paradigm shift from a 2D to 3D subduction framework by facilitating the conceptualization of the modern subduction system on Earth in 3D space.

Recent progress in high-power slab lasers in Japan

International Nuclear Information System (INIS)

Fujii, Y.

1988-01-01

Recently, many solid-state lasers have been widely employed in Japanese industries, especially in the electronics industries for precise and reliable processing. To expand the use of solid-state lasers and to achieve higher processing speed, the authors are developing slab lasers of high power, high repetition rate, and high beam quality. Metal processing systems with optical fibers for large and complex 3-D work, multiwork station systems linked to only one laser with optical fibers, and compact x-ray sources for lithography are promising areas for such lasers. Surnitomo Metal Mining is growing Nd:GGG and Nd:YAG crystals 60 mm in diameter and 200 mm long. From 2 at.% Nd-doped GGG crystals without central core regions. The authors obtained two slab materials with dimensions of 35 X 9 X 192 and 55 X 15 X 213 mm/sup 3/. By using the smaller slab, they constructed a slab laser and obtained 370-W laser output power at 24-kW lamp input power and 10-pps repetition rate. Now they are constructing a 1-kW slab laser using the other larger size slab

Fire resistance of prefabricated monolithic slab

Directory of Open Access Journals (Sweden)

Gravit Marina

2017-01-01

Full Text Available A prefabricated monolithic slab (PMS has a number of valuable advantages, they allow to significantly decrease the weight of construction keeping the necessary structural-load capacity, to speed up and cheapen work conduction, to increase the heat isolating properties of an enclosure structure [1]. In order to create a design method of prefabricated monolithic slab fire-resistance, it's necessary to perform a series of PMS testing, one of which is being described in this article. Subjected to the test is a fragment of prefabricated monolithic slab with polystyrene concrete inserts along the beams with bent metal profile 250 mm thick, with a 2.7 m span loaded with evenly spread load equal to 600 kg/m2. After 3 hour testing for fire-resistance [2] no signs of construction ultimate behavior were detected.

Reinforcement of the concrete base slab of the ATLAS cavern

CERN Multimedia

Maximilien Brice

2002-01-01

Photo 02: UX15 cavern, preparation for concreting of base slab first lift. Photo 05: UX15 cavern, placing of reinforcement for base slab first lift. Photo 07: UX15 cavern, preparation for concreting of base slab first lift. Photo 09: UX15 cavern, placing of reinforcement for base slab first lift. Photo 10: UX15 cavern, view into PX14 shaft above. Photo 12: UX15 cavern, temporary access platform of RB16 tunnel. Photo 15: UJ17 chamber, invert excavation.

Self-shielding for thick slabs in a converging neutron beam

CERN Document Server

Mildner, D F R

1999-01-01

We have previously given a correction to the neutron self-shielding for a thin slab to account for the increased average path length through the slab when irradiated in a converging neutron beam. This expression overstates the case for the self-shielding for a thick (or highly absorbing) slab. We give a better approximation to the increase in effective shielding correction for a slab placed in a converging neutron beam. It is negligible at large absorption mean free paths. (author)

Modeling radon entry into Florida slab-on-grade houses

International Nuclear Information System (INIS)

Revzan, K.L.; Fisk, W.J.; Sextro, R.G.

1993-01-01

Radon entry into a Florida house whose concrete slab is supported by a permeable concrete-block stem wall and a concrete footer is modeled. The slab rests on backfill material; the same material is used to fill the footer trench. A region of undisturbed soil is assumed to extend 10 m beyond and below the footer. The soil is assumed homogeneous and isotropic except for certain simulations in which soil layers of high permeability or radium content are introduced. Depressurization of the house induces a pressure field in the soil and backfill. The Laplace equation, resulting from Darcy's law and the continuity equation, is solved using a steady-state finite-difference model to determine this field. The mass-transport equation is then solved to obtain the diffusive and advective radon entry rates through the slab; the permeable stem wall; gaps at the intersections of the slab, stem wall, and footer; and gaps in the slab. These rates are determined for variable soil, backfill, and stem-wall permeability and radium content, slab-opening width and position, slab and stem-wall diffusivity, and water table depth. The variations in soil permeability and radium content include cases of horizontally stratified soil. We also consider the effect of a gap between the edge of the slab and the stem wall that restricts the passage of soil gas from the stem wall into the house. Calculations indicate that the total radon entry rate is relatively low unless the soil or backfill permeability or radium content is high. Variations in most of the factors, other than the soil permeability and radium content, have only a small effect on the total radon entry rate. However, for a fixed soil permeability, the total radon entry rate may be reduced by a factor of 2 or more by decreasing the backfill permeability, by making the stem wall impermeable and gap-free, (possibly by constructing a one-piece slab/stem-wall/footer), or by increasing the pressure in the interior of the stem wall

Modified bond model for shear in slabs under concentrated loads

NARCIS (Netherlands)

Lantsoght, E.O.L.; Van der Veen, C.; De Boer, A.

2015-01-01

Slabs subjected to concentrated loads close to supports, as occurring for truck loads on slab bridges, are less studied than beams in shear or slab-column connections in punching. To predict the shear capacity for this case, the Bond Model for concentric punching shear was studied initially.

Rayleigh-Taylor instability in accelerated elastic-solid slabs

Science.gov (United States)

Piriz, S. A.; Piriz, A. R.; Tahir, N. A.

2017-12-01

We develop the linear theory for the asymptotic growth of the incompressible Rayleigh-Taylor instability of an accelerated solid slab of density ρ2, shear modulus G , and thickness h , placed over a semi-infinite ideal fluid of density ρ110.1007/s000330050121] to arbitrary values of AT and unveil the singular feature of an instability threshold below which the slab is stable for any perturbation wavelength. As a consequence, an accelerated elastic-solid slab is stable if ρ2g h /G ≤2 (1 -AT) /AT .

Production of High Quality Die Steels from Large ESR Slab Ingots

Science.gov (United States)

Geng, Xin; Jiang, Zhou-hua; Li, Hua-bing; Liu, Fu-bin; Li, Xing

With the rapid development of manufacture industry in China, die steels are in great need of large slab ingot of high quality and large tonnage, such as P20, WSM718R and so on. Solidification structure and size of large slab ingots produced with conventional methods are not satisfied. However, large slab ingots manufactured by ESR process have a good solidification structure and enough section size. In the present research, the new slab ESR process was used to produce the die steels large slab ingots with the maximum size of 980×2000×3200mm. The compact and sound ingot can be manufactured by the slab ESR process. The ultra-heavy plates with the maximum thickness of 410 mm can be obtained after rolling the 49 tons ingots. Due to reducing the cogging and forging process, the ESR for large slab ingots process can increase greatly the yield and production efficiency, and evidently cut off product costs.

Shear strength of end slabs of prestressed concrete reactor vessels

International Nuclear Information System (INIS)

Cheung, K.C.; Gotschall, H.L.; Liu, T.C.

1975-01-01

Prestressed concrete reactor vessels (PCRV's) have been adopted for primary containments in most large high-temperature gas-cooled reactor installations. The most common configuration for PCRVs is a right-vertical cylinder with thick end slabs. In order to assess the integrity of a PCRV it is necessary to predict the ultimate strength of the end slabs. The complexity of the basic mechanism of shear failure in the PCRV end slabs has thus far prohibited the development of a completely analytical solution. However, many experimental investigations of PCRV end slabs have been conducted over the past decade. This information makes it possible to establish empirical formulae for the ultimate strength of PCRV end slabs. The basis and development of an empirical shear-flexure interaction expression is presented. (Auth.)

Slab2 - Updated Subduction Zone Geometries and Modeling Tools

Science.gov (United States)

Moore, G.; Hayes, G. P.; Portner, D. E.; Furtney, M.; Flamme, H. E.; Hearne, M. G.

2017-12-01

The U.S. Geological Survey database of global subduction zone geometries (Slab1.0), is a highly utilized dataset that has been applied to a wide range of geophysical problems. In 2017, these models have been improved and expanded upon as part of the Slab2 modeling effort. With a new data driven approach that can be applied to a broader range of tectonic settings and geophysical data sets, we have generated a model set that will serve as a more comprehensive, reliable, and reproducible resource for three-dimensional slab geometries at all of the world's convergent margins. The newly developed framework of Slab2 is guided by: (1) a large integrated dataset, consisting of a variety of geophysical sources (e.g., earthquake hypocenters, moment tensors, active-source seismic survey images of the shallow slab, tomography models, receiver functions, bathymetry, trench ages, and sediment thickness information); (2) a dynamic filtering scheme aimed at constraining incorporated seismicity to only slab related events; (3) a 3-D data interpolation approach which captures both high resolution shallow geometries and instances of slab rollback and overlap at depth; and (4) an algorithm which incorporates uncertainties of contributing datasets to identify the most probable surface depth over the extent of each subduction zone. Further layers will also be added to the base geometry dataset, such as historic moment release, earthquake tectonic providence, and interface coupling. Along with access to several queryable data formats, all components have been wrapped into an open source library in Python, such that suites of updated models can be released as further data becomes available. This presentation will discuss the extent of Slab2 development, as well as the current availability of the model and modeling tools.

Contribution to the study of slab thickness

International Nuclear Information System (INIS)

Moraitis, G.A.; Rorris, G.P.

1978-01-01

A method is proposed for calculating the time-independent values of the equivalent slab thickness of the ionosphere, defined as the ratio of the total electron content to the corresponding maximum electron density of the F region. Periodic variations of slab thickness are studied and are correlated to relative changes in exospheric temperature, deduced from the OGO-6 model

The threshold contrast thickness evaluated with different CDMAM phantoms and software

Directory of Open Access Journals (Sweden)

Fabiszewska Ewa

2016-03-01

Full Text Available The image quality in digital mammography is described by specifying the thickness and diameter of disks with threshold visibility. The European Commission recommends the CDMAM phantom as a tool to evaluate threshold contrast visibility in digital mammography [1, 2]. Inaccuracy of the manufacturing process of CDMAM 3.4 phantoms (Artinis Medical System BV, as well as differences between software used to analyze the images, may lead to discrepancies in the evaluation of threshold contrast visibility. The authors of this work used three CDMAM 3.4 phantoms with serial numbers 1669, 1840, and 1841 and two mammography systems of the same manufacturer with an identical types of detectors. The images were analyzed with EUREF software (version 1.5.5 with CDCOM 1.6. exe file and Artinis software (version 1.2 with CDCOM 1.6. exe file. The differences between the observed thicknesses of the threshold contrast structures, which were caused by differences between the CDMAM 3.4 phantoms, were not reproduced in the same way on two mammography units of the same type. The thickness reported by the Artinis software (version 1.2 with CDCOM 1.6. exe file was generally greater than the one determined by the EUREF software (version 1.5.5 with CDCOM 1.6. exe file, but the ratio of the results depended on the phantom and diameter of the structure. It was not possible to establish correction factors, which would allow correction of the differences between the results obtained for different CDMAM 3.4 phantoms, or to correct the differences between software. Great care must be taken when results of the tests performed with different CDMAM 3.4 phantoms and with different software application are interpreted.

Phantom pain after eye amputation

DEFF Research Database (Denmark)

Rasmussen, Marie L R; Prause, Jan U; Toft, Peter B

2011-01-01

Purpose: To characterize the quality of phantom pain, its intensity and frequency following eye amputation. Possible triggers and relievers of phantom pain are investigated. Methods: The hospital database was searched using surgery codes for patients who received ocular evisceration, enucleation...... was conducted by a trained interviewer. Results: Of the 173 patients in the study, 39 experienced phantom pain. The median age of patients who had experienced phantom pain was 45 years (range: 19–88). Follow-up time from eye amputation to participation in the investigation was 4 years (range: 2–46). Phantom...... scale, ranging from 0 to 100, was 36 (range: 1–89). One-third of the patients experienced phantom pain every day. Chilliness, windy weather and psychological stress/fatigue were the most commonly reported triggers for pain. Conclusions: Phantom pain after eye amputation is relatively common. The pain...

Damage detection in concrete precast slabs: a quick assessment through modal tests

Directory of Open Access Journals (Sweden)

Leal Pimentel Roberto

2015-01-01

Full Text Available The use of modal tests for detecting damage in reinforced concrete precast slabs is evaluated. A set of eight slabs were tested, each belonging to flats constructed for residential use. Two groups of slabs were identified and, in each group, both cracked and uncracked slabs were found. This made it possible to compare the responses of the slabs when subjected to modal tests. The tests were carried out employing an instrumented hammer and heel drops as excitation sources. Responses were measured using an accelerometer. The lowest natural frequencies of the slabs could be identified and after filtering the results, plots indicating the variation of the lowest natural frequency versus the number of cycles of free decay were obtained for each slab. Such a plot is of more general use than the value of the natural frequency by itself, as it does not depend on slab configuration. It was observed that the cracked slabs presented a similar pattern of variation of the natural frequencies throughout the decay, being distinctive from the pattern observed for their uncracked counterparts. This provided evidence that a quick assessment of the structural condition of such slabs through the use of the tests were feasible.

Hybrid pregnant reference phantom series based on adult female ICRP reference phantom

Science.gov (United States)

Rafat-Motavalli, Laleh; Miri-Hakimabad, Hashem; Hoseinian-Azghadi, Elie

2018-03-01

This paper presents boundary representation (BREP) models of pregnant female and her fetus at the end of each trimester. The International Commission on Radiological Protection (ICRP) female reference voxel phantom was used as a base template in development process of the pregnant hybrid phantom series. The differences in shape and location of the displaced maternal organs caused by enlarging uterus were also taken into account. The CT and MR images of fetus specimens and pregnant patients of various ages were used to replace the maternal abdominal pelvic organs of template phantom and insert the fetus inside the gravid uterus. Each fetal model contains 21 different organs and tissues. The skeletal model of the fetus also includes age-dependent cartilaginous and ossified skeletal components. The replaced maternal organ models were converted to NURBS surfaces and then modified to conform to reference values of ICRP Publication 89. The particular feature of current series compared to the previously developed pregnant phantoms is being constructed upon the basis of ICRP reference phantom. The maternal replaced organ models are NURBS surfaces. With this great potential, they might have the feasibility of being converted to high quality polygon mesh phantoms.

Accidents due to falls from roof slabs.

Science.gov (United States)

Rudelli, Bruno Alves; Silva, Marcelo Valerio Alabarce da; Akkari, Miguel; Santili, Claudio

2013-01-01

CONTEXT AND OBJECTIVE Falls from the roof slabs of houses are accidents of high potential severity that occur in large Brazilian cities and often affect children and adolescents. The aims of this study were to characterize the factors that predispose towards this type of fall involving children and adolescents, quantify the severity of associated lesions and suggest preventive measures. DESIGN AND SETTING Descriptive observational prospective longitudinal study in two hospitals in the metropolitan region of São Paulo. METHODS Data were collected from 29 cases of falls from roof slabs involving children and adolescents between October 2008 and October 2009. RESULTS Cases involving males were more prevalent, accounting for 84%. The predominant age group was schoolchildren (7 to 12 years old; 44%). Leisure activities were most frequently being practiced on the roof slab at the time of the fall (86%), and flying a kite was the most prevalent game (37.9%). In 72% of the cases, the children were unaccompanied by an adult responsible for them. Severe conditions such as multiple trauma and traumatic brain injuries resulted from 79% of the accidents. CONCLUSION Falls from roof slabs are accidents of high potential severity, and preventive measures aimed towards informing parents and guardians about the dangers and risk factors associated with this type of accident are needed, along with physical protective measures, such as low walls around the slab and gates with locks to restrict free access to these places.

Accidents due to falls from roof slabs

Directory of Open Access Journals (Sweden)

Bruno Alves Rudelli

Full Text Available CONTEXT AND OBJECTIVE Falls from the roof slabs of houses are accidents of high potential severity that occur in large Brazilian cities and often affect children and adolescents. The aims of this study were to characterize the factors that predispose towards this type of fall involving children and adolescents, quantify the severity of associated lesions and suggest preventive measures. DESIGN AND SETTING Descriptive observational prospective longitudinal study in two hospitals in the metropolitan region of São Paulo. METHODS Data were collected from 29 cases of falls from roof slabs involving children and adolescents between October 2008 and October 2009. RESULTS Cases involving males were more prevalent, accounting for 84%. The predominant age group was schoolchildren (7 to 12 years old; 44%. Leisure activities were most frequently being practiced on the roof slab at the time of the fall (86%, and flying a kite was the most prevalent game (37.9%. In 72% of the cases, the children were unaccompanied by an adult responsible for them. Severe conditions such as multiple trauma and traumatic brain injuries resulted from 79% of the accidents. CONCLUSION Falls from roof slabs are accidents of high potential severity, and preventive measures aimed towards informing parents and guardians about the dangers and risk factors associated with this type of accident are needed, along with physical protective measures, such as low walls around the slab and gates with locks to restrict free access to these places.

Extraordinary wavelength reduction in terahertz graphene-cladded photonic crystal slabs

Science.gov (United States)

Williamson, Ian A. D.; Mousavi, S. Hossein; Wang, Zheng

2016-01-01

Photonic crystal slabs have been widely used in nanophotonics for light confinement, dispersion engineering, nonlinearity enhancement, and other unusual effects arising from their structural periodicity. Sub-micron device sizes and mode volumes are routine for silicon-based photonic crystal slabs, however spectrally they are limited to operate in the near infrared. Here, we show that two single-layer graphene sheets allow silicon photonic crystal slabs with submicron periodicity to operate in the terahertz regime, with an extreme 100× wavelength reduction from graphene’s large kinetic inductance. The atomically thin graphene further leads to excellent out-of-plane confinement, and consequently photonic-crystal-slab band structures that closely resemble those of ideal two-dimensional photonic crystals, with broad band gaps even when the slab thickness approaches zero. The overall photonic band structure not only scales with the graphene Fermi level, but more importantly scales to lower frequencies with reduced slab thickness. Just like ideal 2D photonic crystals, graphene-cladded photonic crystal slabs confine light along line defects, forming waveguides with the propagation lengths on the order of tens of lattice constants. The proposed structure opens up the possibility to dramatically reduce the size of terahertz photonic systems by orders of magnitude. PMID:27143314

Imaging performance of an isotropic negative dielectric constant slab.

Science.gov (United States)

Shivanand; Liu, Huikan; Webb, Kevin J

2008-11-01

The influence of material and thickness on the subwavelength imaging performance of a negative dielectric constant slab is studied. Resonance in the plane-wave transfer function produces a high spatial frequency ripple that could be useful in fabricating periodic structures. A cost function based on the plane-wave transfer function provides a useful metric to evaluate the planar slab lens performance, and using this, the optimal slab dielectric constant can be determined.

Multi-resolution voxel phantom modeling: a high-resolution eye model for computational dosimetry.

Science.gov (United States)

Caracappa, Peter F; Rhodes, Ashley; Fiedler, Derek

2014-09-21

Voxel models of the human body are commonly used for simulating radiation dose with a Monte Carlo radiation transport code. Due to memory limitations, the voxel resolution of these computational phantoms is typically too large to accurately represent the dimensions of small features such as the eye. Recently reduced recommended dose limits to the lens of the eye, which is a radiosensitive tissue with a significant concern for cataract formation, has lent increased importance to understanding the dose to this tissue. A high-resolution eye model is constructed using physiological data for the dimensions of radiosensitive tissues, and combined with an existing set of whole-body models to form a multi-resolution voxel phantom, which is used with the MCNPX code to calculate radiation dose from various exposure types. This phantom provides an accurate representation of the radiation transport through the structures of the eye. Two alternate methods of including a high-resolution eye model within an existing whole-body model are developed. The accuracy and performance of each method is compared against existing computational phantoms.

Requalification analysis of a circular composite slab for seismic load

International Nuclear Information System (INIS)

Srinivasan, M.G.; Kot, C.A.

1993-01-01

The circular roof slab of an existing facility was analyzed to requalify the structure for supporting a significant seismic load that it was not originally designed for. The slab has a clear span of 66 ft and consists of a 48 in. thick reinforced concrete member and a steel liner plate. Besides a number of smaller penetrations, the slab contains two significant cutouts. The dominant load for the slab came from seismic excitation. It was characterized by a response spectrum with a peak spectral acceleration of 0.72 g in the vertical direction. The first part of the analysis showed that the nature of attachment between the liner plate and the reinforced concrete (RC) slab would justify assuming composite action between the two. A finite clement analysis, with the ANSYS code, was made to investigate the region surrounding the openings. As the reinforcement in the slab was quite inhomogeneous, it was necessary to determine the stresses in other areas of the slab also. These were obtained with closed form expressions. Finally it is shown that the strength design provisions of the Code Requirements for Nuclear Safety Related Concrete Structures were met by the reinforced concrete slab and the allowable stress provisions of the American National Standard for safety related steel structures in nuclear facilities were met by the liner plate. The composite action between the RC slab and the liner plate provides for the additional strength required to support the enhanced seismic load. The issues that complicated the analysis of this nontypical structure, i.e., composite action and nonlinear stiffness of RC sections, are discussed. It was possible to circumvent the difficulties by making conservative and simplifying assumptions. If design codes incorporate guidelines on practical methods for dynamic analysis of RC structures, some of the unneeded conservatism could be eliminated in future designs

Fire resistance of extruded hollow-core slabs

DEFF Research Database (Denmark)

Hertz, Kristian Dahl; Giuliani, Luisa; Sørensen, Lars Schiøtt

2016-01-01

Prefabricated extruded hollow-core slabs are preferred building components for floor structures in several countries. It is therefore important to be able to document the fire resistance of these slabs proving fulfilment of standard fire resistance requirements of 60- and 120 minutes found in most...... a standard fire test and from a thorough examination of the comprehensive test documentation available on fire exposed hollow-core slabs. Mechanisms for loss of load-bearing capacity are clarified, and evidence of the fire resistance is found. For the first time the mechanisms responsible for loss of load......-bearing capacity are identified and test results and calculation approach are for the first time Applied in accordance with each other for assessment of fire resistance of the structure....

Investigation on the performance of bridge approach slab

Directory of Open Access Journals (Sweden)

Abdelrahman Amr

2018-01-01

Full Text Available In Egypt, where highway bridges are to be constructed on soft cohesive soils, the bridge abutments are usually founded on rigid piles, whereas the earth embankments for the bridge approaches are directly founded on the natural soft ground. Consequently, excessive differential settlement frequently occurs between the bridge deck and the bridge approaches resulting in a “bump” at both ends of the bridge deck. Such a bump not only creates a rough and uncomfortable ride but also represents a hazardous condition to traffic. One effective technique to cope with the bump problem is to use a reinforced concrete approach slab to provide a smooth grade transition between the bridge deck and the approach pavement. Investigating the geotechnical and structural performance of approach slabs and revealing the fundamental affecting factors have become mandatory. In this paper, a 2-D finite element model is employed to investigate the performance of approach slabs. Moreover, an extensive parametric study is carried out to appraise the relatively optimum geometries of approach slab, i.e. slab length, thickness, embedded depth and slope, that can yield permissible bumps. Different geo-mechanical conditions of the cohesive foundation soil and the fill material of the bridge embankment are examined.

Processing and properties of large-sized ceramic slabs

Energy Technology Data Exchange (ETDEWEB)

Raimondo, M.; Dondi, M.; Zanelli, C.; Guarini, G.; Gozzi, A.; Marani, F.; Fossa, L.

2010-07-01

Large-sized ceramic slabs with dimensions up to 360x120 cm{sup 2} and thickness down to 2 mm are manufactured through an innovative ceramic process, starting from porcelain stoneware formulations and involving wet ball milling, spray drying, die-less slow-rate pressing, a single stage of fast drying-firing, and finishing (trimming, assembling of ceramic-fiberglass composites). Fired and unfired industrial slabs were selected and characterized from the technological, compositional (XRF, XRD) and microstructural (SEM) viewpoints. Semi-finished products exhibit a remarkable microstructural uniformity and stability in a rather wide window of firing schedules. The phase composition and compact microstructure of fired slabs are very similar to those of porcelain stoneware tiles. The values of water absorption, bulk density, closed porosity, functional performances as well as mechanical and tribological properties conform to the top quality range of porcelain stoneware tiles. However, the large size coupled with low thickness bestow on the slab a certain degree of flexibility, which is emphasized in ceramic-fiberglass composites. These outstanding performances make the large-sized slabs suitable to be used in novel applications: building and construction (new floorings without dismantling the previous paving, ventilated facades, tunnel coverings, insulating panelling), indoor furnitures (table tops, doors), support for photovoltaic ceramic panels. (Author) 24 refs.

Processing and properties of large-sized ceramic slabs

International Nuclear Information System (INIS)

Raimondo, M.; Dondi, M.; Zanelli, C.; Guarini, G.; Gozzi, A.; Marani, F.; Fossa, L.

2010-01-01

Large-sized ceramic slabs with dimensions up to 360x120 cm 2 and thickness down to 2 mm are manufactured through an innovative ceramic process, starting from porcelain stoneware formulations and involving wet ball milling, spray drying, die-less slow-rate pressing, a single stage of fast drying-firing, and finishing (trimming, assembling of ceramic-fiberglass composites). Fired and unfired industrial slabs were selected and characterized from the technological, compositional (XRF, XRD) and microstructural (SEM) viewpoints. Semi-finished products exhibit a remarkable microstructural uniformity and stability in a rather wide window of firing schedules. The phase composition and compact microstructure of fired slabs are very similar to those of porcelain stoneware tiles. The values of water absorption, bulk density, closed porosity, functional performances as well as mechanical and tribological properties conform to the top quality range of porcelain stoneware tiles. However, the large size coupled with low thickness bestow on the slab a certain degree of flexibility, which is emphasized in ceramic-fiberglass composites. These outstanding performances make the large-sized slabs suitable to be used in novel applications: building and construction (new floorings without dismantling the previous paving, ventilated facades, tunnel coverings, insulating panelling), indoor furnitures (table tops, doors), support for photovoltaic ceramic panels. (Author) 24 refs.

Image quality assessment using the CD-DISC phantom for vascular radiology and vascular surgery

International Nuclear Information System (INIS)

Struelens, Lara; Hambach, Lionel; Buls, Nico; Smans, Kristien; Malchair, Francoise; Hoornaert, Marie-Therese; Vanhavere, Filip; Bosmans, Hilde

2008-01-01

The purpose of the study was to evaluate image quality (IQ) associated with vascular radiology and vascular surgery procedures in Belgium and to determine reference values for future image quality assessment. IQ was evaluated with the CD-DISC contrast-detail phantom. This circular PMMA phantom contains 225 holes with different diameter and depth, to quantify resolution and contrast. Images of the phantom were acquired for both fluoroscopy and subtraction images on 21 systems. Three observers evaluated the images by determining the threshold contrast visible for every diameter. This results in contrast-detail curves and image quality figures. We observed a large difference in IQ between the centres. No straightforward correlation could be found with radiation dose or other exposure settings. A comparison was made with the image quality evaluation of the systems performed with the TOR[18FG] phantom for fluoroscopy. There is no clear correlation observed between the results of the CD-DISC phantom and the TOR phantom. However, systems with very poor or very good image quality could be detected by both phantoms. An important result is that a 75th percentile reference contrast-detail curve could be proposed to separate the best centres from these with poorer quality. Some centres had also a significantly better image quality than others. Therefore, we introduced also a 25th percentile. Centres with IQ above this value are recommended to lower the dose and work with acceptable rather than excellent image quality. The CD-DISC phantom thus allows to guide the image quality setting

SU-F-BRE-13: Replacing Pre-Treatment Phantom QA with 3D In-Vivo Portal Dosimetry for IMRT Breast Cancer

Energy Technology Data Exchange (ETDEWEB)

Stroom, J; Vieira, S; Greco, C [Champalimaud Foundation, Lisbon (Portugal); Olaciregui-Ruiz, I; Rozendaal, R; Herk, M van [The Netherlands Cancer Institute, Amsterdam, North Holland (Netherlands); Moser, E [Champalimaud Foundation, Lisbon, Lisbon (Portugal)

2014-06-15

Purpose: Pre-treatment QA of individual treatment plans requires costly linac time and physics effort. Starting with IMRT breast treatments, we aim to replace pre-treatment QA with in-vivo portal dosimetry. Methods: Our IMRT breast cancer plans are routinely measured using the ArcCheck device (SunNuclear). 2D-Gamma analysis is performed with 3%/3mm criteria and the percentage of points with gamma<1 (nG1) is calculated within the 50% isodose surface. Following AAPM recommendations, plans with nG1<90% are approved; others need further inspection and might be rejected. For this study, we used invivo portal dosimetry (IPD) to measure the 3D back-projected dose of the first three fractions for IMRT breast plans. Patient setup was online corrected before for all measured fractions. To reduce patient related uncertainties, the three IPD results were averaged and 3D-gamma analysis was applied with abovementioned criteria . For a subset of patients, phantom portal dosimetry (PPD) was also performed on a slab phantom. Results: Forty consecutive breast patients with plans that fitted the EPID were analysed. The average difference between planned and IPD dose in the reference point was −0.7+/−1.6% (1SD). Variation in nG1 between the 3 invivo fractions was about 6% (1SD). The average nG1 for IPD was 89+/−6%, worse than ArcCheck (95+/−3%). This can be explained by patient related factors such as changes in anatomy and/or model deficiencies due to e.g. inhomogeneities. For the 20 cases with PPD, mean nG1 was equal to ArcCheck values, which indicates that the two systems are equally accurate. These data therefore suggest that proper criteria for 3D invivo verification of breast treatments should be nG1>80% instead of nG1>90%, which, for our breast cases, would result in 5% (2/40) further inspections. Conclusion: First-fraction in-vivo portal dosimetry using new gamma-evaluation criteria will replace phantom measurements in our institution, saving resources and yielding 3D

Novel variational approach for analysis of photonic crystal slabs

International Nuclear Information System (INIS)

Aram, Mohammad Hasan; Khorasani, Sina

2015-01-01

We propose a new method, based on variational principle, for the analysis of photonic crystal (PC) slabs. Most of the methods used today treat PC slabs as three-dimensional (3D) crystal, and this makes these methods very time and/or memory consuming. In our proposed method, we use the Bloch theorem to expand the field on infinite plane waves, whose amplitudes depend on the component perpendicular to the slab surface. By approximating these amplitudes with appropriate functions, we can find modes of PC slabs almost as fast as we can find modes of two-dimensional crystals. In addition to this advantage, we can also calculate radiation modes with this method, which is not feasible with the 3D plane wave expansion method. (paper)

An improved MCNP version of the NORMAN voxel phantom for dosimetry studies.

Science.gov (United States)

Ferrari, P; Gualdrini, G

2005-09-21

In recent years voxel phantoms have been developed on the basis of tomographic data of real individuals allowing new sets of conversion coefficients to be calculated for effective dose. Progress in radiation studies brought ICRP to revise its recommendations and a new report, already circulated in draft form, is expected to change the actual effective dose evaluation method. In the present paper the voxel phantom NORMAN developed at HPA, formerly NRPB, was employed with MCNP Monte Carlo code. A modified version of the phantom, NORMAN-05, was developed to take into account the new set of tissues and weighting factors proposed in the cited ICRP draft. Air kerma to organ equivalent dose and effective dose conversion coefficients for antero-posterior and postero-anterior parallel photon beam irradiations, from 20 keV to 10 MeV, have been calculated and compared with data obtained in other laboratories using different numerical phantoms. Obtained results are in good agreement with published data with some differences for the effective dose calculated employing the proposed new tissue weighting factors set in comparison with previous evaluations based on the ICRP 60 report.

Slab replacement maturity guidelines.

Science.gov (United States)

2014-04-01

This study investigated the use of maturity method to determine early age strength of concrete in slab : replacement application. Specific objectives were (1) to evaluate effects of various factors on the compressive : maturity-strength relationship ...

Development of realistic physical breast phantoms matched to virtual breast phantoms based on human subject data

International Nuclear Information System (INIS)

Kiarashi, Nooshin; Nolte, Adam C.; Sturgeon, Gregory M.; Ghate, Sujata V.; Segars, William P.; Nolte, Loren W.; Samei, Ehsan

2015-01-01

Purpose: Physical phantoms are essential for the development, optimization, and evaluation of x-ray breast imaging systems. Recognizing the major effect of anatomy on image quality and clinical performance, such phantoms should ideally reflect the three-dimensional structure of the human breast. Currently, there is no commercially available three-dimensional physical breast phantom that is anthropomorphic. The authors present the development of a new suite of physical breast phantoms based on human data. Methods: The phantoms were designed to match the extended cardiac-torso virtual breast phantoms that were based on dedicated breast computed tomography images of human subjects. The phantoms were fabricated by high-resolution multimaterial additive manufacturing (3D printing) technology. The glandular equivalency of the photopolymer materials was measured relative to breast tissue-equivalent plastic materials. Based on the current state-of-the-art in the technology and available materials, two variations were fabricated. The first was a dual-material phantom, the Doublet. Fibroglandular tissue and skin were represented by the most radiographically dense material available; adipose tissue was represented by the least radiographically dense material. The second variation, the Singlet, was fabricated with a single material to represent fibroglandular tissue and skin. It was subsequently filled with adipose-equivalent materials including oil, beeswax, and permanent urethane-based polymer. Simulated microcalcification clusters were further included in the phantoms via crushed eggshells. The phantoms were imaged and characterized visually and quantitatively. Results: The mammographic projections and tomosynthesis reconstructed images of the fabricated phantoms yielded realistic breast background. The mammograms of the phantoms demonstrated close correlation with simulated mammographic projection images of the corresponding virtual phantoms. Furthermore, power

Development of realistic physical breast phantoms matched to virtual breast phantoms based on human subject data

Energy Technology Data Exchange (ETDEWEB)

Kiarashi, Nooshin [Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Duke University Medical Center, Durham, North Carolina 27710 and Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708 (United States); Nolte, Adam C. [Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Duke University Medical Center, Durham, North Carolina 27710 and Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708 (United States); Sturgeon, Gregory M.; Ghate, Sujata V. [Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Duke University Medical Center, Durham, North Carolina 27710 (United States); Segars, William P. [Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Duke University Medical Center, Durham, North Carolina 27710 and Medical Physics Graduate Program, Duke University, Durham, North Carolina 27708 (United States); Nolte, Loren W. [Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708 and Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708 (United States); Samei, Ehsan [Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Duke University Medical Center, Durham, North Carolina 27710 (United States); Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708 (United States); Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708 (United States); Medical Physics Graduate Program, Duke University, Durham, North Carolina 27708 (United States); Department of Physics, Duke University, Durham, North Carolina 27708 (United States); and others

2015-07-15

Purpose: Physical phantoms are essential for the development, optimization, and evaluation of x-ray breast imaging systems. Recognizing the major effect of anatomy on image quality and clinical performance, such phantoms should ideally reflect the three-dimensional structure of the human breast. Currently, there is no commercially available three-dimensional physical breast phantom that is anthropomorphic. The authors present the development of a new suite of physical breast phantoms based on human data. Methods: The phantoms were designed to match the extended cardiac-torso virtual breast phantoms that were based on dedicated breast computed tomography images of human subjects. The phantoms were fabricated by high-resolution multimaterial additive manufacturing (3D printing) technology. The glandular equivalency of the photopolymer materials was measured relative to breast tissue-equivalent plastic materials. Based on the current state-of-the-art in the technology and available materials, two variations were fabricated. The first was a dual-material phantom, the Doublet. Fibroglandular tissue and skin were represented by the most radiographically dense material available; adipose tissue was represented by the least radiographically dense material. The second variation, the Singlet, was fabricated with a single material to represent fibroglandular tissue and skin. It was subsequently filled with adipose-equivalent materials including oil, beeswax, and permanent urethane-based polymer. Simulated microcalcification clusters were further included in the phantoms via crushed eggshells. The phantoms were imaged and characterized visually and quantitatively. Results: The mammographic projections and tomosynthesis reconstructed images of the fabricated phantoms yielded realistic breast background. The mammograms of the phantoms demonstrated close correlation with simulated mammographic projection images of the corresponding virtual phantoms. Furthermore, power

Tensor-guided fitting of subduction slab depths

Science.gov (United States)

Bazargani, Farhad; Hayes, Gavin P.

2013-01-01

Geophysical measurements are often acquired at scattered locations in space. Therefore, interpolating or fitting the sparsely sampled data as a uniform function of space (a procedure commonly known as gridding) is a ubiquitous problem in geophysics. Most gridding methods require a model of spatial correlation for data. This spatial correlation model can often be inferred from some sort of secondary information, which may also be sparsely sampled in space. In this paper, we present a new method to model the geometry of a subducting slab in which we use a data‐fitting approach to address the problem. Earthquakes and active‐source seismic surveys provide estimates of depths of subducting slabs but only at scattered locations. In addition to estimates of depths from earthquake locations, focal mechanisms of subduction zone earthquakes also provide estimates of the strikes of the subducting slab on which they occur. We use these spatially sparse strike samples and the Earth’s curved surface geometry to infer a model for spatial correlation that guides a blended neighbor interpolation of slab depths. We then modify the interpolation method to account for the uncertainties associated with the depth estimates.

Slab tears and intermediate-depth seismicity

Science.gov (United States)

Meighan, Hallie E.; ten Brink, Uri S.; Pulliam, Jay

2013-01-01

Active tectonic regions where plate boundaries transition from subduction to strike slip can take several forms, such as triple junctions, acute, and obtuse corners. Well-documented slab tears that are associated with high rates of intermediate-depth seismicity are considered here: Gibraltar arc, the southern and northern ends of the Lesser Antilles arc, and the northern end of Tonga trench. Seismicity at each of these locations occurs, at times, in the form of swarms or clusters, and various authors have proposed that each marks an active locus of tear propagation. The swarms and clusters start at the top of the slab below the asthenospheric wedge and extend 30–60 km vertically downward within the slab. We propose that these swarms and clusters are generated by fluid-related embrittlement of mantle rocks. Focal mechanisms of these swarms generally fit the shear motion that is thought to be associated with the tearing process.

Determination of mammography images constancy parameters for C R system using Phantom Mama and mammographic accreditation phantom

International Nuclear Information System (INIS)

Santos, Andre U. dos; Souza, Wedla P. de; Hoff, Gabriela

2009-01-01

In the diagnostic imaging services is common to find the analogical image acquiring method in transition to the digital acquiring method. However it is necessary to define the appropriate techniques for acquisition of images. For that achievement the reference parameter of image must be determinate and based on that, determine the constancy and diagnostic image quality tests. Annually, for each imaging system, it is recommended the technical parameters review for different types of breast, reducing the dose on the mammary gland and preserving the image quality. It should be done based on national regulations and in accordance to the requirements of the medical team. The methodological proposes of this work has the objective of realize the constancy analysis for the image quality, using the PhantonMama and Mamographic Accreditation Phantom model 18-220 (recommended by ACR) and the software. Both protocols suggested were adequate for the analysis proposed. (author)

Vertical slab sinking and westward subduction offshore of Mesozoic North America

Science.gov (United States)

Sigloch, Karin; Mihalynuk, Mitchell G.

2013-04-01

Subducted slabs in the mantle, as imaged by seismic tomography, preserve a record of ancient subduction zones. Ongoing debate concerns how direct this link is. How long ago did each parcel of slab subduct, and where was the trench located relative to the imaged slab position? Resolving these questions will benefit paleogeographic reconstructions, and restrict the range of plausible rheologies for mantle convection simulations. We investigate one of the largest and best-constrained Mesozoic slab complexes, the "Farallon" in the transition zone and lower mantle beneath North America. We quantitatively integrate observations from whole-mantle P-wave tomography, global plate reconstructions, and land geological evidence from the North American Cordillera. These three data sets permit us to test the simplest conceivable hypothesis for linking slabs to paleo-trenches: that each parcel of slab sank only vertically shortly after entering the trench That is, we test whether within the limits of tomographic resolution, all slab material lies directly below the location where it subducted beneath its corresponding arc. Crucially and in contrast to previous studies, we do not accept or impose an Andean-style west coast trench (Farallon-beneath-continent subduction) since Jurassic times, as this scenario is inconsistent with many geological observations. Slab geometry alone suggests that trenches started out as intra-oceanic because tomography images massive, linear slab "walls" in the lower mantle, extending almost vertically from about 800 km to 2000+ km depth. Such steep geometries would be expected from slabs sinking vertically beneath trenches that were quasi-stationary over many tens of millions of years. Intra-oceanic trenches west of Mesozoic North America could have been stationary, whereas a coastal Farallon trench could not, because the continent moved westward continuously as the Atlantic opened. Overlap of North American west-coast positions, as reconstructed in a

TECHNOLOGY FOR INSTALLATION OF REINFORCED CONCRETE FLOOR SLABS LIGHTENED BY CORE DRIVERS WITH PRELIMINARY REINFORCEMENT STRESS

OpenAIRE

S. N. Leonovich; I. I. Peredkov

2015-01-01

The paper presents technology for installation of floor slabs lightened by plastic core drivers which are preliminary stressed under construction conditions.  Efficiency of such constructive solution is justified by the action of preliminary concrete compression in the tensile zone while reducing structure dead weight due to void arrangement.  The paper provides classification of systems for preliminary stress and contains recommendations on selection of the system depending on peculiariar fe...

Roof slab cooling device in a FBR type reactor

International Nuclear Information System (INIS)

Tarutani, Kohei

1987-01-01

Purpose: To obtain a roof slab cooling device capable of retaining cooling performance even in a case of electric power supply stop or failure and effective from economical point of view. Constitution: Atmospheric air is introduced into the cooling chamber of a proof slab and spontaneously passed to a exit pipeway connected to a stack thereby cooling the roof slab. Specifically, atmospheric air entered from the inlet pipeway is introduced to the cooling chamber and absorbs heat generate from the inside of the reactor container. Warmed air is sucked from the exit pipeway and then released into the atmosphere passing through the stack. The air cools the roof slab during circulation due to spontaneous passage and keeps the slab at a low temperature. Since the air is passed spontaneously, no power such as for a blower is required at all and, if the electric power supply should be lost, the cooling power can be maintained as it is to provide a high reliability. Further, since no electric power is required for the blowing power, it has high economical merit. (Horiuchi, T.)

Electron beam absorption in solid and in water phantoms: depth scaling and energy-range relations

International Nuclear Information System (INIS)

Grosswendt, B.; Roos, M.

1989-01-01

In electron dosimetry energy parameters are used with values evaluated from ranges in water. The electron ranges in water may be deduced from ranges measured in solid phantoms. Several procedures recommended by national and international organisations differ both in the scaling of the ranges and in the energy-range relations for water. Using the Monte Carlo method the application of different procedures for electron energies below 10 MeV is studied for different phantom materials. It is shown that deviations in the range scaling and in the energy-range relations for water may accumulate to give energy errors of several per cent. In consequence energy-range relations are deduced for several solid phantom materials which enable a single-step energy determination. (author)

NMR-CT image and symbol phantoms

International Nuclear Information System (INIS)

Hongo, Syozo; Yamaguchi, Hiroshi; Takeshita, Hiroshi

1990-01-01

We have developed Japanese phantoms in two procedures. One is described as a mathematical expression. Another is 'symbol phantoms' in 3 dimensional picture-elements, each of which symbolize an organ name. The concept and the algorithm of the symbol phantom enables us to make a phantom for a individual in terms of all his transversal section images. We got 85 transversal section images of head and trunk parts, and those of 40 legs parts by using NMR-CT. We have made the individual phantom for computation of organ doses. The transversal section images were not so clear to identify all organs needed to dose estimation that we had to do hand-editing the shapes of organs with viewing a typical section images: we could not yet make symbol phantom in a automatic editing. Symbols were coded to be visual cords as ASCII characters. After we got the symbol phantom of the first stage, we can edit it easily using a word-processor. Symbol phantom could describe more freely the shape of organs than mathematical phantom. Symbol phantom has several advantages to be an individual phantom, but the only difficult point is how to determine its end-point as a reference man when we apply the method to build the reference man. (author)

Ratios between the effective doses for tomographic phantoms MAX and FAX

International Nuclear Information System (INIS)

Kramer, R.; Khoury, H.J.

2005-01-01

In the last two decades, the coefficients for the equivalent dose in organs and tissues, as well as to the effective dose, recommended by the International Commission on Radiological Protection (ICRP) were determined using exposure models based on stylized phantoms type MIRD, representing the human body with its radiosensitive organs and tissues according to the ICRP 23 Reference Man, Monte Carlo codes that simulate in a simplified way radiation physics, fabric compositions from different sources, and sometimes applied in a no realistic way, and by the list of organs and tissues at risk with their corresponding weight factors, published in ICRP 60. In the meantime, the International Commission on radiation units and Measurements (ICRU) published reference data to human tissue compositions in ICRU 44 and ICRP launched new anatomical and physiological data of reference in the report number 89. In addition a draft report with recommendations to be released in 2005 (http://icrp.org/) advances significant changes in the list of radiosensitive organs and tissues as well as their corresponding weight factors. As a practical consequence, all components of the traditional stylized models of exposure should be replaced: Monte Carlo codes, human phantoms, the compositions of the fabric and the selection of the organs and tissues at risk with their respective weight factors to determine the effective dose. This article presents the results of comprehensive research into the dosimetric consequences of replacing the stylized models of exposure. The calculations were done using the EGS4 Monte Carlo and MCNP4C codes for external and internal exposure to photons and electrons with phantoms ADAM and EVA, as well as with tomographic phantoms MAX and FAX, for different compositions and tissue distributions. The ratios between effective doses for models of exposure based on phantoms of voxels and effective doses for the stylized models for external and internal exposure to photons and

Closure behavior of spherical void in slab during hot rolling process

Science.gov (United States)

Cheng, Rong; Zhang, Jiongming; Wang, Bo

2018-04-01

The mechanical properties of steels are heavily deteriorated by voids. The influence of voids on the product quality should be eliminated through rolling processes. The study on the void closure during hot rolling processes is necessary. In present work, the closure behavior of voids at the center of a slab at 800 °C during hot rolling processes has been simulated with a 3D finite element model. The shape of the void and the plastic strain distribution of the slab are obtained by this model. The void decreases along the slab thickness direction and spreads along the rolling direction but hardly changes along the strip width direction. The relationship between closure behavior of voids and the plastic strain at the center of the slab is analyzed. The effects of rolling reduction, slab thickness and roller diameter on the closure behavior of voids are discussed. The larger reduction, thinner slab and larger roller diameter all improve the closure of voids during hot rolling processes. Experimental results of the closure behavior of a void in the slab during hot rolling process mostly agree with the simulation results..

Construction of Chinese reference female phantom

International Nuclear Information System (INIS)

Sheng Yinxiangzi; Liu Lixing; Xia Xiaobin

2013-01-01

In this study, a Voxel-based Chinese Reference female Phantom (VCRP-woman) is developed from an individual female phantom which was based on high resolution cross-sectional color photographs. An in-house C ++ program was developed to adjust the phantom. Finally, a reference female phantom with have the same height, weighte and similar organs masses with the Chinese reference adult female data. The adjusted phantom is then imported to MCNPX to calculate the organs absorbed dose and effective dose conversion coefficients. Results are compared between VCRP-woman and the ICRP adult reference female phantom. (authors)

Phantom Sensations, Supernumerary Phantom Limbs and Apotemnophilia: Three Body Representation Disorders.

Science.gov (United States)

Tatu, Laurent; Bogousslavsky, Julien

2018-01-01

Body representation disorders continue to be mysterious and involve the anatomical substrate that underlies the mental representation of the body. These disorders sit on the boundaries of neurological and psychiatric diseases. We present the main characteristics of 3 examples of body representation disorders: phantom sensations, supernumerary phantom limb, and apotemnophilia. The dysfunction of anatomical circuits that regulate body representation can sometimes have paradoxical features. In the case of phantom sensations, the patient feels the painful subjective sensation of the existence of the lost part of the body after amputation, surgery or trauma. In case of apotemnophilia, now named body integrity identity disorder, the subject wishes for the disappearance of the existing and normal limb, which can occasionally lead to self-amputation. More rarely, a brain-damaged patient with 4 existing limbs can report the existence of a supernumerary phantom limb. © 2018 S. Karger AG, Basel.

21. Phantom pain.

NARCIS (Netherlands)

Wolff, A.P.; Vanduynhoven, E.; Kleef, M. van; Huygen, F.; Pope, J.E.; Mekhail, N.

2011-01-01

Phantom pain is pain caused by elimination or interruption of sensory nerve impulses by destroying or injuring the sensory nerve fibers after amputation or deafferentation. The reported incidence of phantom limb pain after trauma, injury or peripheral vascular diseases is 60% to 80%. Over half the

Development Length for Headed Bars in Slab-Column Joints of RC Slab Bridges

Science.gov (United States)

2015-12-04

In accordance with the Caltrans Seismic Design Criteria, the superstructure in a slab bridge should remain essentially elastic and only the pile extensions/columns are permitted to develop inelastic deformations during a seismic event. Hence, the lon...

Moisture transfer in a concrete slab

International Nuclear Information System (INIS)

Huang, C.L.D.; Siang, H.H.; Kirmser, P.G.

1979-01-01

A diffusion theory with a linear or a nonlinear coefficient of diffusivity is insufficient for the characterization of the drying behaviour of hydrated concrete slabs. A general mathematical model, based on nonequilibrium, irreversible flows of heat and mass, yields a set of nonlinear partial differential equations of parabolic type. Implicit finite difference calculations for a concrete slab yield moisture, temperature, and pressure histories as well as global average drying rates. Graphs show that during the pendular state of dessication, diffusion, capillary, and evaporation-condensation processes are the governing mechanisms in drying. (orig.)

Analisis Perbandingan Material Slab Beton Pada Perkerasan Apron Dengan Menggunakan Program Bantu Elemen Hingga

Directory of Open Access Journals (Sweden)

Hendrawan Setyo Warsito

2016-04-01

Full Text Available Kekuatan slab beton sangat dipengaruhi oleh jenis material yang dipakai. Jenis material yang dimaksud adalah material beton dengan menggunakan PC (Portland Cement dan penggunaan geopolimer dalam komposisi campuran slab beton. Beton geopolimer merupakan beton yang ramah lingkungan. Permasalahan lain yang timbul adalah letak roda pesawat tidak selalu berada pada titik yang sama disuatu permukaan slab beton apron. Pada tugas akhir ini dimaksudkan untuk menganalisis suatu slab beton yang dibebani roda pesawat dengan campuran variasi material beton dan variasi letak roda pesawat pada slab beton dengan program bantu metode elemen hingga. Dengan data pergerakan pesawat, spesifikasi apron bandara Juanda kondisi eksisting. Dilakukan perhitungan tebal slab beton menggunakan software FAARFIELD dan diperoleh tebal slab beton sebesar 442,5 mm. Dari analisis program bantu elemen hingga dapat diperoleh tegangan pada slab beton yang ditimbulkan oleh pembebanan roda pesawat. Hasil validasi dari analisis tegangan menggunakan program bantu elemen hingga dengan analisis Westergaard yaitu memiliki nilai tegangan yang hampir sama pada ketebalan slab beton 450mm. Nilai tegangan tiap-tiap material beton menunjukan nilai tebal slab beton yang diijinkan untuk tipe pesawat tertentu. Dari analisis menggunakan program bantu elemen hingga tebal slab beton yang diijinkan untuk material slab beton PC yaitu sebesar 425mm. Sedangkan untuk material beton geopolimer yaitu sebesar  415 mm.

Dose calculation on voxels phantoms using the GEANT4 code

International Nuclear Information System (INIS)

Martins, Maximiano C.; Santos, Denison S.; Queiroz Filho, Pedro P.; Begalli, Marcia

2009-01-01

This work implemented an anthropomorphic phantom of voxels on the structure of Monte Carlo GEANT4, for utilization by professionals from the radioprotection, external dosimetry and medical physics. This phantom allows the source displacement that can be isotropic punctual, plain beam, linear or radioactive gas, in order to obtain diverse irradiation geometries. In them, the radioactive sources exposure is simulated viewing the determination of effective dose or the dose in each organ of the human body. The Zubal head and body trunk phantom was used, and we can differentiate the organs and tissues by the chemical constitution in soft tissue, lung tissue, bone tissue, water and air. The calculation method was validated through the comparison with other well established method, the Visual Monte Carlo (VMC). Besides, a comparison was done with the international recommendation for the evaluation of dose by exposure to punctual sources, described in the document TECDOC - 1162- Generic Procedures for Assessment and Response During a Radiological Emergency, where analytical expressions for this calculation are given. Considerations are made on the validity limits of these expressions for various irradiation geometries, including linear sources, immersion into clouds and contaminated soils

Calibration of clinical dosemeters in the IAEA water phantom

International Nuclear Information System (INIS)

Caldas, L.V.E.; Albuquerque, M.P.P.

1994-01-01

The procedures recommended by the IAEA Code of Practice were applied at the Calibration Laboratory of Sao Paulo in order to provide in the future the clinical dosemeters users with absorbed dose to water calibration factors for Cobalt 60 radiation beams. In this work the clinical dosemeters were calibrated free in air and in water, and the results were compared, using conversion factors. The several tested clinical dosemeters of different manufacturers and models belong to the laboratory and to hospitals. For the measurements in water the IAEA cubic water phantom was used. The dosemeters were all calibrated free in air in terms of air kerma, and the calibration factors in terms of absorbed dose to water were obtained through conversion factors. the same dosemeters were also calibrated into the water phantom. Good agreement was found between the two methods, the differences were always less than 0.5%. The data obtained during this work show that when the dosemeters are used only in Cobalt 60 radiation and the users apply in the hospital routine work the IAEA Code of Practice, the calibration can be performed directly in the water phantom. This procedure provides the useful calibration factors in terms of absorbed dose to water

Development and application of a pediatric head phantom for dosimetry in computed tomography

International Nuclear Information System (INIS)

Martins, Elaine Wirney

2016-01-01

To determine the exposure levels and the absorbed dose in patients undergoing CT scans, is necessary to calculate the CT dose index in measurements with a PMMA or water phantom. The phantom must be enough to simulate the attenuation and scattering characteristics of a human body or parts in a radiation field. The CT specific quantities : CT air kerma index (Ca,100) , weighted CT air kerma index (CW ), a total volume CT air kerma index (Cvol) and the CT air kerma-length product (PKL) must be determined and compared to literature reference levels. In this work a head pediatric phantom was developed, considering that the Brazilian published Diagnostic Reference Levels (DRL) are based on adult phantom measurements. This developed phantom shows a construction innovation using materials to simulate the skullcap, cortical bone (aluminum) and cancellous bone (PVC), and it was filled with distilled water. The phantom dimension follows the recommendations of the World Health Organization and the International Commission on Radiation Units for children from 0 to 5 years old head size: diameter of 160 mm and height of 155 mm. The skullcap has 4 mm of thickness and 111.9 mm of internal diameter. In order to evaluate its behavior, tests were carried out in calibration laboratories and in clinical beams. The results showed attenuation up to 23% when different materials are used as skullcap, demonstrating that the DRLs adopted could be overestimating the dose received by pediatric patients. It is observed that the dose received by CT skull scans presents different distribution, due to the skullcap partially attenuation and/or backscattering which is not considered when the PMMA phantom is used.

Analysis of the Behaviour of Composite Steel and Steel Fiber Reinforced Concrete Slabs

Directory of Open Access Journals (Sweden)

Mindaugas Petkevičius

2011-04-01

Full Text Available There was a pending influence of steel fiber on the strength and stiffness of composite steel–concrete slabs under statical short–time load. Steel profiled sheeting and steel fiber reinforced concrete were used for specimens. Four composite slabs were made. Experimental investigations into the behaviour and influence of steel fiber reinforced concrete in composite slabs were conducted. Transverse, longitudinal, shear deformation and deflection of the slab were measured. The results indicated that the use of steel fiber in composite slabs was effective: strength was 20–24 % higher and the meanings of deflections under the action of the bending moment were 0,6MR (where MR is the bending moment at failure of the slabs and were 16–18 % lower for slabs with usual concrete. Article in Lithuanian

First-principles approach for superconducting slabs and heterostructures

Energy Technology Data Exchange (ETDEWEB)

Csire, Gabor [Wigner Research Centre for Physics, Budapest (Hungary)

2016-07-01

We present a fully ab-initio method to calculate the transition temperature for superconducting slabs and heterostructures. In the case of thin superconductor layers the electron-phonon interaction may change significantly. Therefore we calculate the layer dependent phonon spectrum to determine the layer dependence of the electron-phonon coupling for such systems. The phonon spectrum is than coupled to the Kohn-Sham-Bogoliubov-de Gennes equation via the McMillan-Hopfield parameter, and it is solved self-consistently. The theory is applied to niobium slabs and niobium-gold heterostructures. Based on these calculations we investigate both the dependence of the superconducting transition temperature on the thickness of superconducting slabs and the inverse proximity effect observed in thin superconducting heterostructures.

Estimation of RC slab-column joints effective strength using neural networks

Directory of Open Access Journals (Sweden)

A. A. Shah

Full Text Available The nominal strength of slab-column joints made of highstrength concrete (HSC columns and normal strength concrete (NSC slabs is of great importance in structural design and construction of concrete buildings. This topic has been intensively studied during the last decades. Different types of column-slab joints have been investigated experimentally providing a basis for developing design provisions. However, available data does not cover all classes of concretes, reinforcements, and possible loading cases for the proper calculation of joint stresses necessary for design purposes. New numerical methods based on modern software seem to be effective and may allow reliable prediction of column-slab joint strength. The current research is focused on analysis of available experimental data on different slab-to-column joints with the aim of predicting the nominal strength of slabcolumn joint. Neural networks technique is proposed herein using MATLAB routines developed to analyze available experimental data. The obtained results allow prediction of the effective strength of column-slab joints with accuracy and good correlation coefficients when compared to regression based models. The proposed method enables the user to predict the effective design of column-slab joints without the need for conservative safety coefficients generally promoted and used by most construction codes.

Assessment of specific absorbed fractions for photons and electrons using average adult Japanese female phantom

International Nuclear Information System (INIS)

Manabe, Kentaro; Sato, Kaoru; Takahashi, Fumiaki

2016-12-01

In the 2007 Recommendations of the International Commission on Radiological Protection (ICRP), the procedure for calculating effective doses was modified as follows. Equivalent doses are evaluated using the male and female voxel phantoms on the basis of reference anatomical data of Caucasians, and effective doses are calculated using sex-averaged equivalent doses in applying tissue weighting factors. Specific absorbed fractions (SAFs), which are essential data for calculating internal doses, depend on the body weights, organ masses, and positional relations of organs of the phantoms. Then, the dose coefficients, which are committed effective doses per unit intake of radionuclides, developed by ICRP on the basis of the 2007 Recommendations reflect the physical characteristics of Caucasians and are averaged over the sexes. Meanwhile, the physiques of adult Japanese are generally smaller than those of adult Caucasians, and organ masses are also different from each other. Therefore, dose coefficients reflecting Japanese physical characteristics are different from those of ICRP. Knowledge of the influence of race differences on dose coefficients is important to apply the sex averaged dose coefficients of ICRP to the Japanese system of radiation protection. SAF data based on phantoms which have Japanese physical characteristics is essential for assessment of the dose coefficients reflecting Japanese physical characteristics. The Japan Atomic Energy Agency constructed average adult Japanese phantoms, JM-103 (male) and JF-103 (female), and is developing a dose estimation method for internal exposure using these phantoms. This report provides photon and electron SAFs of JF-103. The data of this report and the previously published data of JM-103 are applicable to evaluate sex-specific and sex-averaged dose coefficients reflecting the physical characteristics of the average adult Japanese for intakes of radionuclides emitting photons and electrons. Appendix as CD-ROM. (J.P.N.)

Seismic Evidence for Possible Slab Melting from Strong Scattering Waves

Directory of Open Access Journals (Sweden)

Cheng-Horng Lin

2011-01-01

Full Text Available Slab melting in young and hot subduction zones has been studied using geochemical observations and thermal modelling, but there are few data from seismic studies to confirm slab melting. Also the detailed geometry in the deep part of the melting slab is often ambiguous in that the intraslab earthquakes within the Wadati-Benioff zone are only limited to shallower depths. To improve our understanding of both the seismic features and geometry found in a young and hot subducted slab, I analyzed anomalous moonquake-like seismograms that were generated by an intermediate-depth earthquake recorded in central Japan. For this study, possible reflected (or scattered sources were examined using detailed analyses of particle motions and a grid search for travel-time differences between the direct and later P-waves. The results show that using strong seismic scattering, slab melting is likely occurring in the deeper, flexing part of the subducted Philippine Sea plate. Because the subducted Philippine Sea plate in central Japan is young and therefore hot, partial melting might have taken place to produce abundant melting spots in the subducted slab. Melting spots, identified as ¡§bright spots,¡¨ could efficiently reflect or scatter seismic energy and generate many later phases with large amplitudes.

Dose errors due to charge storage in electron irradiated plastic phantoms

International Nuclear Information System (INIS)

Galbraith, D.M.; Rawlinson, J.A.; Munro, P.

1984-01-01

Commercial plastics used for radiation dosimetry are good electrical insulators. Used in electron beams, these insulators store charge and produce internal electric fields large enough to measurably alter the electron dose distribution in the plastic. The reading per monitor unit from a cylindrical ion chamber imbedded in a polymethylmethacrylate (PMMA) or polystyrene phantom will increase with accumulated electron dose, the increase being detectable after about 20 Gy of 6-MeV electrons. The magnitude of the effect also depends on the type of the plastic, the thickness of the plastic, the wall thickness of the detector, the diameter and depth of the hole in the plastic, the energy of the electron beam, and the dose rate used. Effects of charge buildup have been documented elsewhere for very low energy electrons at extremely high doses and dose rates. Here we draw attention to the charging effects in plastics at the dose levels encountered in therapy dosimetry where ion chamber or other dosimeter readings may easily increase by 5% to 10% and where a phantom, once charged, will also affect subsequent readings taken in 60 Co beams and high-energy electron and x-ray beams for periods of several days to many months. It is recommended that conducting plastic phantoms replace PMMA and polystyrene phantoms in radiation dosimetry

Comparing Hp(3) evaluated from the conversion coefficients from air kerma to personal dose equivalent for eye lens dosimetry calibrated on a new cylindrical PMMA phantom

Science.gov (United States)

Esor, J.; Sudchai, W.; Monthonwattana, S.; Pungkun, V.; Intang, A.

2017-06-01

Based on a new occupational dose limit recommended by ICRP (2011), the annual dose limit for the lens of the eye for workers should be reduced from 150 mSv/y to 20 mSv/y averaged over 5 consecutive years in which no single year exceeding 50 mSv. This new dose limit directly affects radiologists and cardiologists whose work involves high radiation exposure over 20 mSv/y. Eye lens dosimetry (Hp(3)) has become increasingly important and should be evaluated directly based on dosimeters that are worn closely to the eye. Normally, Hp(3) dose algorithm was carried out by the combination of Hp(0.07) and Hp(10) values while dosimeters were calibrated on slab PMMA phantom. Recently, there were three reports from European Union that have shown the conversion coefficients from air kerma to Hp(3). These conversion coefficients carried out by ORAMED, PTB and CEA Saclay projects were performed by using a new cylindrical head phantom. In this study, various delivered doses were calculated using those three conversion coefficients while nanoDot, small OSL dosimeters, were used for Hp(3) measurement. These calibrations were performed with a standard X-ray generator at Secondary Standard Dosimetry Laboratory (SSDL). Delivered doses (Hp(3)) using those three conversion coefficients were compared with Hp(3) from nanoDot measurements. The results showed that percentage differences between delivered doses evaluated from the conversion coefficient of each project and Hp(3) doses evaluated from the nanoDots were found to be not exceeding -11.48 %, -8.85 % and -8.85 % for ORAMED, PTB and CEA Saclay project, respectively.

A phantom for assessing the personal dose equivalent, H{sub P}(10); Um fantoma para a avaliacao do equivalente de dose pessoal, H{sub P}(10).

Energy Technology Data Exchange (ETDEWEB)

Santoro, C.; Filho, J.A [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Departamento de Energia Nuclear; Santos, M.A.P.; Filho, L.C.G., E-mail: chsantoro@gmail.com, E-mail: masantos@cnen.gov.br, E-mail: l.filho@cnen.gov.br, E-mail: jaf@ufpe.br [Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE/CNEN-PE), Recife, PE (Brazil)

2013-10-15

Characteristics of a phantom designed to evaluate the personal dose equivalent, H{sub P}(10), and appropriate for photographic dosimetry are presented. It is called HP(10) phantom due to cavities constructed to insert dosimetric films at a depth of 10 mm. The H{sub P}(10) phantom is irradiated with ionizing radiation energy, E, from 45 to 1250 keV, with doses ranging from 0.2 to 50 mSv. It is positioned in the direction α = 0 °, and the radiation field focusing perpendicular to its front surface. So, are established calibration curves of dosimeters in the position conventionally true and quantities H{sub P}(10). It made a comparison between the responses obtained with the H{sub P}(10) phantom and responses obtained when using the calibration procedure recommended by ISO dosimeters. The ISO recommends getting the air kerma, Ka, for photons at test point of the radiation field by an ionization chamber. And through conversion coefficients, h{sub pK} (10; E, α), becomes the air kerma for H{sub P}(10). The ISO 4037-3 recommendation has been studied by researchers to ensure that the low energy spectral differences occur in radiation fields which are generated by various X-ray equipment, and induce changes in the percentages of conversion coefficients on the order of 10% to 90% . On the basis of the recommendations ISO, this article develops phantom able to assess the dose to the influence of scattering and absorption of radiation, its implications with respect to dosimetry, providing improvement in the assessment of doses. (author)

SU-C-213-02: Characterizing 3D Printing in the Fabrication of Variable Density Phantoms

International Nuclear Information System (INIS)

Madamesila, J; McGeachy, P; Villarreal-Barajas, J; Khan, R

2015-01-01

Purpose: In this work, we present characterization, process flow, quality control and application of 3D fabricated low density phantoms for radiotherapy quality assurance. Methods: A Rostock delta 3D printer using polystyrene filament of diameter 1.75 mm was used to print geometric volumes of 2×2×1 cm 3 of varying densities. The variable densities of 0.1 to 0.75 g/cm 3 were created by modulating the infill. A computed tomography (CT) scan was performed to establish an infill-density calibration curve as well as characterize the quality of the print such as uniformity and the infill pattern. The time required to print these volumes was also recorded. Using the calibration, two low density cones (0.19, 0.52 g/cm 3 ) were printed and benchmarked against commercially available phantoms. The dosimetric validation of the low density scaling of Anisotropic Analytical Algorithm (AAA) was performed by using a 0.5 g/cm 3 slab of 10×10×2.4 cm 3 with EBT3 GafChromic film. The gamma analysis at 3%/3mm criteria were compared for the measured and computed dose planes. Results: Analysis of the volume of air pockets in the infill resulted in a reasonable uniformity for densities 0.4 to 0.75 g/cm 3 . Printed phantoms with densities below 0.4 g/cm 3 exhibited a higher ratio of air to polystyrene resulting in large non-uniformity. Compared to the commercial inserts, good agreement was observed only for the printed 0.52 g/cm 3 cone. Dosimetric comparison for a printed low density volume placed in-between layers of solid water resulted in >95% gamma agreement between AAA calculated dose planes and measured EBT3 films for a 6MV 5×5 cm 2 clinical beam. The comparison showed disagreement in the penumbra region. Conclusion: In conclusion, 3D printing technology opens the door to desktop fabrication of variable density phantoms at economical prices in an efficient manner for the quality assurance needs of a small clinic

Effect of the electron transport through thin slabs on the simulation of linear electron accelerators of use in therapy: A comparative study of various Monte Carlo codes

Energy Technology Data Exchange (ETDEWEB)

Vilches, M. [Servicio de Fisica y Proteccion Radiologica, Hospital Regional Universitario ' Virgen de las Nieves' , Avda. de las Fuerzas Armadas, 2, E-18014 Granada (Spain)], E-mail: mvilches@ugr.es; Garcia-Pareja, S. [Servicio de Radiofisica Hospitalaria, Hospital Regional Universitario ' Carlos Haya' , Avda. Carlos Haya, s/n, E-29010 Malaga (Spain); Guerrero, R. [Servicio de Radiofisica, Hospital Universitario ' San Cecilio' , Avda. Dr. Oloriz, 16, E-18012 Granada (Spain); Anguiano, M.; Lallena, A.M. [Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada (Spain)

2007-09-21

When a therapeutic electron linear accelerator is simulated using a Monte Carlo (MC) code, the tuning of the initial spectra and the renormalization of dose (e.g., to maximum axial dose) constitute a common practice. As a result, very similar depth dose curves are obtained for different MC codes. However, if renormalization is turned off, the results obtained with the various codes disagree noticeably. The aim of this work is to investigate in detail the reasons of this disagreement. We have found that the observed differences are due to non-negligible differences in the angular scattering of the electron beam in very thin slabs of dense material (primary foil) and thick slabs of very low density material (air). To gain insight, the effects of the angular scattering models considered in various MC codes on the dose distribution in a water phantom are discussed using very simple geometrical configurations for the LINAC. The MC codes PENELOPE 2003, PENELOPE 2005, GEANT4, GEANT3, EGSnrc and MCNPX have been used.

Effect of the electron transport through thin slabs on the simulation of linear electron accelerators of use in therapy: A comparative study of various Monte Carlo codes

International Nuclear Information System (INIS)

Vilches, M.; Garcia-Pareja, S.; Guerrero, R.; Anguiano, M.; Lallena, A.M.

2007-01-01

When a therapeutic electron linear accelerator is simulated using a Monte Carlo (MC) code, the tuning of the initial spectra and the renormalization of dose (e.g., to maximum axial dose) constitute a common practice. As a result, very similar depth dose curves are obtained for different MC codes. However, if renormalization is turned off, the results obtained with the various codes disagree noticeably. The aim of this work is to investigate in detail the reasons of this disagreement. We have found that the observed differences are due to non-negligible differences in the angular scattering of the electron beam in very thin slabs of dense material (primary foil) and thick slabs of very low density material (air). To gain insight, the effects of the angular scattering models considered in various MC codes on the dose distribution in a water phantom are discussed using very simple geometrical configurations for the LINAC. The MC codes PENELOPE 2003, PENELOPE 2005, GEANT4, GEANT3, EGSnrc and MCNPX have been used

Interaction of an ion bunch with a plasma slab

Energy Technology Data Exchange (ETDEWEB)

Krasovitskiy, V. B., E-mail: krasovit@mail.ru [Russian Academy of Sciences, Keldysh Institute of Applied Mathematics (Russian Federation); Turikov, V. A. [Peoples’ Friendship University of Russia (Russian Federation)

2016-11-15

Charge neutralization of a short ion bunch passing through a plasma slab is studied by means of numerical simulation. It is shown that a fraction of plasma electrons are trapped by the bunch under the action of the collective charge separation field. The accelerated electrons generated in this process excite beam−plasma instability, thereby violating the trapping conditions. The process of electron trapping is also strongly affected by the high-frequency electric field caused by plasma oscillations at the slab boundaries. It is examined how the degree of charge neutralization depends on the parameters of the bunch and plasma slab.

Light-assisted templated self assembly using photonic crystal slabs.

Science.gov (United States)

Mejia, Camilo A; Dutt, Avik; Povinelli, Michelle L

2011-06-06

We explore a technique which we term light-assisted templated self-assembly. We calculate the optical forces on colloidal particles over a photonic crystal slab. We show that exciting a guided resonance mode of the slab yields a resonantly-enhanced, attractive optical force. We calculate the lateral optical forces above the slab and predict that stably trapped periodic patterns of particles are dependent on wavelength and polarization. Tuning the wavelength or polarization of the light source may thus allow the formation and reconfiguration of patterns. We expect that this technique may be used to design all-optically reconfigurable photonic devices.

Evidence for Slab Melt Contributions to the Mexican Volcanic Belt and Other Young Hot Slab Arcs from Lu-Hf Isotopes

Science.gov (United States)

Goldstein, S. L.; Cai, Y. M.; Langmuir, C. H.; Lagatta, A.; Straub, S. M.; Gomez-Tuena, A.; Martin Del Pozzo, A.

2007-12-01

Despite major advances in delineating the processes that govern magma generation at convergent margins, the problem persists of distinguishing slab, mantle wedge, and crustal contributions. A corrollary question is whether there is significant melting of subducted ocean crust. Especially in thick crust regions, the importance of crustal versus mantle contributions to lavas represents a long-standing fundamental issue in arc magma geochemistry. We show that frontal arc magmas from the Central Mexican Volcanic Belt (CMVB), including the large andesitic stratovolcanoes Popocatepetl and Nevado de Toluca, display negligible crustal contamination, and contain substantial contributions from melting of subducted Pacific ocean crust. Despite ca. 50 km thick continental crust, the CMVB erupts near primitive lavas including "high-Nb" alkaline basalts that show negligible "subduction signatures" in their trace element patterns. These "high-Nb" basalts define the regional mantle wedge composition in isotope-trace element space. The "normal" calcalkaline lavas form a negative correlation between Hf isotopes and Lu/Hf. One endmember is like the high Nb basalts representing the regional mantle wedge. The other endmember has higher Hf isotopes (approaching values of Pacific MORB) and very low Lu/Hf of less than 0.04 (e.g. compared to typical values of ca. 0.2 in Pacific MORB). The low Lu/Hf values require low degree partial melting of a source rich in garnet. The high Hf isotopes require a depleted mantle source with isotopes like Pacific MORB. Together the Lu-Hf data indicate a substantial component derived from melting of eclogitic Pacific ocean crust. A key feature of the data is that the stratovolcano lavas showing the largest slab melt signature also show the highest Hf isotope ratios and thus are more "depleted mantle-like" than the regional mantle wedge. Thus, the integrated data allow us to clearly distinguish between mantle and crustal sources in the CMVB and point to

Sub-wavelength grating mode transformers in silicon slab waveguides.

Science.gov (United States)

Bock, Przemek J; Cheben, Pavel; Schmid, Jens H; Delâge, André; Xu, Dan-Xia; Janz, Siegfried; Hall, Trevor J

2009-10-12

We report on several new types of sub-wavelength grating (SWG) gradient index structures for efficient mode coupling in high index contrast slab waveguides. Using a SWG, an adiabatic transition is achieved at the interface between silicon-on-insulator waveguides of different geometries. The SWG transition region minimizes both fundamental mode mismatch loss and coupling to higher order modes. By creating the gradient effective index region in the direction of propagation, we demonstrate that efficient vertical mode transformation can be achieved between slab waveguides of different core thickness. The structures which we propose can be fabricated by a single etch step. Using 3D finite-difference time-domain simulations we study the loss, polarization dependence and the higher order mode excitation for two types (triangular and triangular-transverse) of SWG transition regions between silicon-on-insulator slab waveguides of different core thicknesses. We demonstrate two solutions to reduce the polarization dependent loss of these structures. Finally, we propose an implementation of SWG structures to reduce loss and higher order mode excitation between a slab waveguide and a phase array of an array waveguide grating (AWG). Compared to a conventional AWG, the loss is reduced from -1.4 dB to < -0.2 dB at the slab-array interface.

On Early Age Crack Formation in FRC Slabs

DEFF Research Database (Denmark)

Olesen, John Forbes; Stang, Henrik

1997-01-01

The problem of early age crack formation in FRC slabs due to restrained temperature and shrinkage deformations, is given an analytical treatment. A model taking into account the ageing properties of the tensile softening curve and the continued development in the temperature and shrinkage...... deformations after crack initiation, is presented. Based on this model a design strategy for FRC slabs is outlined....

Evolution of dosimetric phantoms

International Nuclear Information System (INIS)

Reddy, A.R.

2010-01-01

In this oration evolution of the dosimetric phantoms for radiation protection and for medical use is briefly reviewed. Some details of the development of Indian Reference Phantom for internal dose estimation are also presented

Flexural strength and behaviour of SFRSCC ribbed slab under four point bending

Science.gov (United States)

Ahmad, Hazrina; Hashim, Mohd Hisbany Mohd; Bakar, Afidah Abu; Hamzah, Siti Hawa; Rahman, Fadhillah Abdul

2017-11-01

An experimental investigation was carried out to study the ultimate strength and behaviour of SFRSCC ribbed slab under four point bending. Comparison was been made between ribbed slab that was fully reinforced with steel fibres (SFWS) with conventionally reinforced concrete ribbed slab (CS and CRC). The volume fraction of the 35 mm hooked end steel fibres used in the mix was 1% (80 kg/m3) with the aspect ratio of 65. Three full scale slab samples with the dimension of 2.8 x 1.2 m with 0.2 m thickness was constructed for the purpose of this study. The slab samples was loaded until failure in a four point bending test. As a whole, based on the results, it can be concluded that the performance of the steel fiber reinforced samples (SFWS) was found to be almost equivalent to the conventionally reinforced concrete ribbed slab sample (CRC).

Ultimate deformation capacity of reinforced concrete slabs underblast load

NARCIS (Netherlands)

Doormaal, J.C.A.M. van; Weerheijm, J.

1996-01-01

In this paper a test method to determine the deformation capacity and the resistance-deformation curve of blast-loaded slabs is described. This method was developed at TNO-PML. The method has been used to determine the ultimate deformation capacity of some simply supported reinforced concrete slabs

Development and application of the Chinese adult female computational phantom Rad-HUMAN

International Nuclear Information System (INIS)

Wu, Yican; Cheng, Mengyun; Wang, Wen; Fan, Yanchang; Zhao, Kai; He, Tao; Pei, Xi; Shang, Leiming; Chen, Chaobin; Long, Pengcheng; Cao, Ruifen; Wang, Guozhong; Zhou, Shaoheng; Yu, Shengpeng; Hu, Liqin; Zeng, Q.

2013-01-01

Rad-HUMAN is a whole-body numerical phantom of a Chinese adult woman which contains 46 organs and tissues and was created by MCAM6 software using the color photographs of the Chinese Visible Human dataset. This dataset was obtained from a 22-year old Chinese female cadaver judged to represent normal human anatomy as much as possible. The density and elemental composition recommended in the ICRP Publication 89 and in the ICRU report 44 were assigned to the organ and tissue in Rad-HUMAN for radiation protection purpose. The last step was to implement the anatomical data into a Monte Carlo code. Rad-HUMAN contains more than 28.8 billion tiny volume units, which produces an accurately whole-body numerical phantom of a Chinese adult female

Intra- and interobserver reliability of gray scale/dynamic range evaluation of ultrasonography using a standardized phantom

International Nuclear Information System (INIS)

Lee, Song; Choi, Joon Il; Park, Michael Yong; Yeo, Dong Myung; Byun, Jae Young; Jung, Seung Eun; Rha, Sung Eun; Oh, Soon Nam; Lee, Young Joon

2014-01-01

To evaluate intra- and interobserver reliability of the gray scale/dynamic range of the phantom image evaluation of ultrasonography using a standardized phantom, and to assess the effect of interactive education on the reliability. Three radiologists (a resident, and two board-certified radiologists with 2 and 7 years of experience in evaluating ultrasound phantom images) performed the gray scale/dynamic range test for an ultrasound machine using a standardized phantom. They scored the number of visible cylindrical structures of varying degrees of brightness and made a pass or fail decision. First, they scored 49 phantom images twice from a 2010 survey with limited knowledge of phantom images. After this, the radiologists underwent two hours of interactive education for the phantom images and scored another 91 phantom images from a 2011 survey twice. Intra- and interobserver reliability before and after the interactive education session were analyzed using K analyses. Before education, the K-value for intraobserver reliability for the radiologist with 7 years of experience, 2 years of experience, and the resident was 0.386, 0.469, and 0.465, respectively. After education, the K-values were improved (0.823, 0.611, and 0.711, respectively). For interobserver reliability, the K-value was also better after the education for the 3 participants (0.067, 0.002, and 0.547 before education; 0.635, 0.667, and 0.616 after education, respectively). The intra- and interobserver reliability of the gray scale/dynamic range was fair to substantial. Interactive education can improve reliability. For more reliable results, double- checking of phantom images by multiple reviewers is recommended.

Radon Sub-slab Suctioning System Integrated in Insulating Layer

DEFF Research Database (Denmark)

Rasmussen, Torben Valdbjørn

2013-01-01

This poster presents a new radon sub-slab suctioning system. This system makes use of a grid of horizontal pressurised air ducts located within the lower part of the rigid insulation layer of the ground floor slab. For this purpose a new system of prefabricated lightweight elements is introduced...

Out-of-plane ultimate shear strength of RC mat-slab foundations

International Nuclear Information System (INIS)

Kumagai, Hitoshi; Nukui, Yasushi; Imamura, Akira; Terayama, Takeshi; Hagiwara, Tetsuya; Kojima, Isao

2011-01-01

There have been few studies on the out-of-plane shear in RC mat-slab foundations, and the reasonable method has been demanded to estimate ultimate shear strength of RC mat-slab foundations in the nuclear facilities. In the previous study, the out-of-plane loading tests on the 20 square slab specimens had been performed to collect the fundamental data. In this study, the test results were successfully predicted by 3D non-linear Finite Element Analysis. It has been confirmed that the ultimate shear stress in the slab specimen can be estimated by the Arakawa's formula, which is commonly used to estimate the shear strength of RC beams. (author)

New Packaging for Amplifier Slabs

Energy Technology Data Exchange (ETDEWEB)

Riley, M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Thorsness, C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Suratwala, T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Steele, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Rogowski, G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2015-03-18

The following memo provides a discussion and detailed procedure for a new finished amplifier slab shipping and storage container. The new package is designed to maintain an environment of <5% RH to minimize weathering.

Dose conversion coefficients calculated using a series of adult Japanese voxel phantoms against external photon exposure

International Nuclear Information System (INIS)

Sato, Kaoru; Endo, Akira; Saito, Kimiaki

2008-10-01

This report presents a complete set of conversion coefficients of organ doses and effective doses calculated for external photon exposure using five Japanese adult voxel phantoms developed at the Japan Atomic Energy Agency (JAEA). At the JAEA, high-resolution Japanese voxel phantoms have been developed to clarify the variation of organ doses due to the anatomical characteristics of Japanese, and three male phantoms (JM, JM2 and Otoko) and two female phantoms (JF and Onago) have been constructed up to now. The conversion coefficients of organ doses and effective doses for the five voxel phantoms have been calculated for six kinds of idealized irradiation geometries from monoenergetic photons ranging from 0.01 to 10 MeV using EGS4, a Monte Carlo code for the simulation of coupled electron-photon transport. The dose conversion coefficients are given as absorbed dose and effective dose per unit air-kerma free-in-air, and are presented in tables and figures. The calculated dose conversion coefficients are compared with those of voxel phantoms based on the Caucasian and the recommended values in ICRP74 in order to discuss (1) variation of organ dose due to the body size and individual anatomy, such as position and shape of organs, and (2) effect of posture on organ doses. The present report provides valuable data to study the influence of the body characteristics of Japanese upon the organ doses and to discuss developing reference Japanese and Asian phantoms. (author)

Optimal Material Layout - Applied on Reinforced Concrete Slabs

DEFF Research Database (Denmark)

Dollerup, Niels; Jepsen, Michael S.; Damkilde, Lars

2015-01-01

This paper introduces a general, finite-element-based optimisation tool for improving the material layout of concrete structures. The application presented is general and exemplified by material optimisation of reinforced concrete slabs. By utilising the optimisation tool, it is possible to deter......This paper introduces a general, finite-element-based optimisation tool for improving the material layout of concrete structures. The application presented is general and exemplified by material optimisation of reinforced concrete slabs. By utilising the optimisation tool, it is possible...... to determine the optimal material layout of a slab in the ultimate load state, based on simple inputs such as outer geometry, boundary conditions, multiple load cases and design domains. The material layout of the optimal design can either be fully orthotropic or isotropic, or a combination with a predefined...

The impact of anthropometric patient-phantom matching on organ dose: A hybrid phantom study for fluoroscopy guided interventions

International Nuclear Information System (INIS)

Johnson, Perry B.; Geyer, Amy; Borrego, David; Ficarrotta, Kayla; Johnson, Kevin; Bolch, Wesley E.

2011-01-01

Purpose: To investigate the benefits and limitations of patient-phantom matching for determining organ dose during fluoroscopy guided interventions. Methods: In this study, 27 CT datasets representing patients of different sizes and genders were contoured and converted into patient-specific computational models. Each model was matched, based on height and weight, to computational phantoms selected from the UF hybrid patient-dependent series. In order to investigate the influence of phantom type on patient organ dose, Monte Carlo methods were used to simulate two cardiac projections (PA/left lateral) and two abdominal projections (RAO/LPO). Organ dose conversion coefficients were then calculated for each patient-specific and patient-dependent phantom and also for a reference stylized and reference hybrid phantom. The coefficients were subsequently analyzed for any correlation between patient-specificity and the accuracy of the dose estimate. Accuracy was quantified by calculating an absolute percent difference using the patient-specific dose conversion coefficients as the reference. Results: Patient-phantom matching was shown most beneficial for estimating the dose to heavy patients. In these cases, the improvement over using a reference stylized phantom ranged from approximately 50% to 120% for abdominal projections and for a reference hybrid phantom from 20% to 60% for all projections. For lighter individuals, patient-phantom matching was clearly superior to using a reference stylized phantom, but not significantly better than using a reference hybrid phantom for certain fields and projections. Conclusions: The results indicate two sources of error when patients are matched with phantoms: Anatomical error, which is inherent due to differences in organ size and location, and error attributed to differences in the total soft tissue attenuation. For small patients, differences in soft tissue attenuation are minimal and are exceeded by inherent anatomical differences

3D Printing Openable Imaging Phantom Design

International Nuclear Information System (INIS)

Kim, Myoung Keun; Won, Jun Hyeok; Lee, Seung Wook

2017-01-01

The purpose of this study is to design an openable phantom that can replace the internal measurement bar used for contrast comparison in order to increase the efficiency of manufacturing imaging phantom used in the medical industry and to improve convenience using 3D printer. Phantom concept design, 3D printing, and Image reconstruction were defined as the scope of the thesis. Also, we study metal artifact reduction with openable phantom. We have designed a Openable phantom using 3D printing, and have investigated metal artifact reduction after inserting a metallic material inside the phantom. The openable phantom can be adjusted at any time to suit the user's experiment and can be easily replaced and useful.

Radon exhalation study from cement, cement slabs and concrete slabs with variation in fly ash

International Nuclear Information System (INIS)

Sharma, Nisha; Singh, Jaspal

2012-01-01

Fly ash is a waste product from coal-fired power plants. Fly ash has become a subject of world-wide interest in recent years because of its diverse uses, e.g. in the manufacture of concrete for building purposes, for the filling of underground cavities, or as a component of building material. The fly ash may contain enhanced levels of the natural radionuclides in the uranium and thorium series and by using the fly ash in building materials, the radiation levels in houses may thus be technologically enhanced. Because of its relatively high radionuclide contents (including 226 Ra), fly ash may, however, present a potential hazard to the population through its radon emanation, which would be highly undesirable. Since fly ash is frequently used as a building material, the idea of the experiment was to mix fly ash in different proportions in the cement in the powder form, cemented slabs and concrete slabs to study the combined behaviors. Alpha sensitive LR-115 type II plastic track detector, commonly known as Solid State Nuclear Track Detectors (SSNTDs), were used to measure the radon concentration. The alpha particles emitted from the radon causes the radiation damaged tracks. The chemical etching in NaOH at 60°C for about 90 minutes was done to reveal these latent tracks, which were then scanned and counted by an optical microscope of suitable magnification. By calculating the track density of registered tracks, the radon concentrations were determined. In case of cement in the powder form and in cemented slab, starting from the pure cement, fly ash was added up to 70% by weight. In this case the radon exhalation rate has increased by addition of fly ash in the cement and in case of concrete slabs by the addition of fly ash in the cement the radon exhalation increases up to 60% and then decreases. Therefore, on the basis of our investigations we concluded that in general radon exhalation rate increases with the addition of fly ash. (author)

Flexural Strengthening of RC Slabs Using a Hybrid FRP-UHPC System Including Shear Connector

Directory of Open Access Journals (Sweden)

Jiho Moon

2017-01-01

Full Text Available A polymeric hybrid composite system made of UHPC and CFRP was proposed as a retrofit system to enhance flexural strength and ductility of RC slabs. While the effectiveness of the proposed system was confirmed previously through testing three full-scale one-way slabs having two continuous spans, the slabs retrofitted with the hybrid system failed in shear. This sudden shear failure would stem from the excessive enhancement of the flexural strength over the shear strength. In this study, shear connectors were installed between the hybrid system and a RC slab. Using simple beam, only positive moment section was examined. Two full-scale RC slabs were cast and tested to failure: the first as a control and the second using this new strengthening technique. The proposed strengthening system increased the ultimate load carrying capacity of the slab by 70%, the stiffness by 60%, and toughness by 128%. The efficiency of shear connectors on ductile behavior of the retrofitted slab was also confirmed. After the UHPC top is separated from the slab, the shear connector transfer shear load and the slab system were in force equilibrium by compression in UHPC and tension in CFRP.

Pediatric Phantom Dosimetry of Kodak 9000 Cone-beam Computed Tomography.

Science.gov (United States)

Yepes, Juan F; Booe, Megan R; Sanders, Brian J; Jones, James E; Ehrlich, Ygal; Ludlow, John B; Johnson, Brandon

2017-05-15

The purpose of the study was to evaluate the radiation dose of the Kodak 9000 cone-beam computed tomography (CBCT) device for different anatomical areas using a pediatric phantom. Absorbed doses resulting from maxillary and mandibular region three by five cm CBCT volumes of an anthropomorphic 10-year-old child phantom were acquired using optical stimulated dosimetry. Equivalent doses were calculated for radiosensitive tissues in the head and neck area, and effective dose for maxillary and mandibular examinations were calculated following the 2007 recommendations of the International Commission on Radiological Protection (ICRP). Of the mandibular scans, the salivary glands had the highest equivalent dose (1,598 microsieverts [μSv]), followed by oral mucosa (1,263 μSv), extrathoracic airway (pharynx, larynx, and trachea; 859 μSv), and thyroid gland (578 μSv). For the maxilla, the salivary glands had the highest equivalent dose (1,847 μSv), followed closely by oral mucosa (1,673 μSv), followed by the extrathoracic airway (pharynx, larynx, and trachea; 1,011 μSv) and lens of the eye (202 μSv). Compared to previous research of the Kodak 9000, completed with the adult phantom, a child receives one to three times more radiation for mandibular scans and two to 10 times more radiation for maxillary scans.

Analysis of instability of tall buildings with prestressed and waffle slabs

Directory of Open Access Journals (Sweden)

V. M. Passos

Full Text Available ABSTRACT The construction system of prestressed flat slabs has been gaining market in Brazil, since it eliminates the use of beams, allows you to perform structures under coluns by area and reduces the cycle of concrete slabs. Thus the analysis of global stability of buildings, takes into account the effects of 2nd order, and these additional effects to the structure obtained from the deformation thereof, calculated by the iterative method P-Delta. The Brazilian ABNT NBR 6118: 2014 [2] assesses the overall stability of reinforced concrete structures through practical parameters, which are the parameter a (Alpha and gz (Gamma z coefficient. In this research we seek to study the global stability of slender buildings consist of flat slabs, with slenderness (ratio of the smaller width with the height of the building approximately one to six, from the modeling of a building with prestressed slabs nonadherent and waffle slabs. To model will use the commercial software CAD / TQS.

Calculation of shear strength of prestressed hollow core slabs by use of plastic theory

DEFF Research Database (Denmark)

Hoang, Linh Cao; Jørgensen, H.G.; Nielsen, Mogens Peter

2014-01-01

Th is paper deals with calculations of the shear capacity of precast, prestressed hollow core slabs. Such slabs are often used as floor systems in building structures. A common way to produce hollow core slabs is to use the extrusion technique where long strips of slabs are extruded and thereafter...

Optimising the Slab Yard Planning and Crane Scheduling Problem using a two-stage heuristic

DEFF Research Database (Denmark)

Hansen, Anders Dohn; Clausen, Jens

2010-01-01

In this paper, we present the Slab Yard Planning and Crane Scheduling Problem. The problem has its origin in steel production facilities with a large throughput. A slab yard is used as a buffer for slabs that are needed in the upcoming production. Slabs are transported by cranes and the problem...

Analysis and design of composite slab by varying different parameters

Science.gov (United States)

Lambe, Kedar; Siddh, Sharda

2018-03-01

Composite deck slabs are in demand because of its faster, lighter and economical construction work. Composite slab consists of cold formed deck profiled sheet and concrete either lightweight or normal. Investigation of shear behaviour of the composite slab is very complex. Shear bond strength depends on the various parameter such as a shape of sheeting, a thickness of the sheet, type of embossment and its frequency of use, shear stiffener or intermediate stiffener, type of load, an arrangement of load, length of shear span, the thickness of concrete and support friction etc. In present study finite element analysis is carried out with ABAQUS 6.13, a simply supported composite slab is considered for the investigation of the shear bond behaviour of the composite slab by considering variation in three different parameters, the shape of a sheet, thickness of sheet and shear span. Different shear spans of two different shape of cold formed deck profiled sheet i.e. with intermediate stiffeners and without intermediate stiffeners are considered with two different thicknesses (0.8 mm and 1.2 mm) for simulation. In present work, simulation of models has done for static loading with 20 mm mesh size is considered.

Code system to compute radiation dose in human phantoms

International Nuclear Information System (INIS)

Ryman, J.C.; Cristy, M.; Eckerman, K.F.; Davis, J.L.; Tang, J.S.; Kerr, G.D.

1986-01-01

Monte Carlo photon transport code and a code using Monte Carlo integration of a point kernel have been revised to incorporate human phantom models for an adult female, juveniles of various ages, and a pregnant female at the end of the first trimester of pregnancy, in addition to the adult male used earlier. An analysis code has been developed for deriving recommended values of specific absorbed fractions of photon energy. The computer code system and calculational method are described, emphasizing recent improvements in methods

A novel DTI-QA tool: Automated metric extraction exploiting the sphericity of an agar filled phantom.

Science.gov (United States)

Chavez, Sofia; Viviano, Joseph; Zamyadi, Mojdeh; Kingsley, Peter B; Kochunov, Peter; Strother, Stephen; Voineskos, Aristotle

2018-02-01

To develop a quality assurance (QA) tool (acquisition guidelines and automated processing) for diffusion tensor imaging (DTI) data using a common agar-based phantom used for fMRI QA. The goal is to produce a comprehensive set of automated, sensitive and robust QA metrics. A readily available agar phantom was scanned with and without parallel imaging reconstruction. Other scanning parameters were matched to the human scans. A central slab made up of either a thick slice or an average of a few slices, was extracted and all processing was performed on that image. The proposed QA relies on the creation of two ROIs for processing: (i) a preset central circular region of interest (ccROI) and (ii) a signal mask for all images in the dataset. The ccROI enables computation of average signal for SNR calculations as well as average FA values. The production of the signal masks enables automated measurements of eddy current and B0 inhomogeneity induced distortions by exploiting the sphericity of the phantom. Also, the signal masks allow automated background localization to assess levels of Nyquist ghosting. The proposed DTI-QA was shown to produce eleven metrics which are robust yet sensitive to image quality changes within site and differences across sites. It can be performed in a reasonable amount of scan time (~15min) and the code for automated processing has been made publicly available. A novel DTI-QA tool has been proposed. It has been applied successfully on data from several scanners/platforms. The novelty lies in the exploitation of the sphericity of the phantom for distortion measurements. Other novel contributions are: the computation of an SNR value per gradient direction for the diffusion weighted images (DWIs) and an SNR value per non-DWI, an automated background detection for the Nyquist ghosting measurement and an error metric reflecting the contribution of EPI instability to the eddy current induced shape changes observed for DWIs. Copyright © 2017 Elsevier

Field Enhancement in a Grounded Dielectric Slab by Using a Single Superstrate Layer

Directory of Open Access Journals (Sweden)

Constantinos A. Valagiannopoulos

2012-01-01

Full Text Available The addition of a dielectric layer on a slab configuration is frequently utilized in various electromagnetic devices in order to give them certain desired operational characteristics. In this work, we consider a grounded dielectric film-slab, which is externally excited by a normally-incident Gaussian beam. On top of the film-slab, we use an additional suitably selected single isotropic superstrate layer in order to increase the field concentration inside the slab and hence achieve optimal power transfer from the external source to the internal region. We define a quantity of interest, called “enhancement factor,” expressing the increase of the field concentration in the film-slab when the superstrate is present compared to the case that it is absent. It is shown that large enhancement factor values may be achieved by choosing properly the permittivity, the permeability, and the thickness of the superstrate. In particular, it is demonstrated that the field in the film-slab is significantly enhanced when the slab is composed by an ϵ-near-zero (ENZ or low-index metamaterial.

Slab replacement maturity guidelines : [summary].

Science.gov (United States)

2014-04-01

Concrete sets in hours at moderate temperatures, : but the bonds that make concrete strong continue : to mature over days to years. However, for : replacement concrete slabs on highways, it is : crucial that concrete develop enough strength : within ...

Why and Where do Large Shallow Slab Earthquakes Occur?

Science.gov (United States)

Seno, T.; Yoshida, M.

2001-12-01

Within a shallow portion (20-60 km depth) of subducting slabs, it has been believed that large earthquakes seldom occur because the differential stress is generally expected to be low between bending at the trench-outer rise and unbending at the intermediate-depth. However, there are several regions in which large ( M>=7.0 ) earthquakes, including three events early in this year, have occurred in this portion. Searching such events from published individual studies and Harvard University centroid moment tensor catalogue, we find nineteen events in eastern Hokkaido, Kyushu-SW Japan, Mariana, Manila, Sumatra, Vanuatu, Chile, Peru, El Salvador, Mexico, and Cascadia. Slab stresses revealed from the mechanism solutions of those large events and smaller events are tensional in a slab dip direction. However, ages of the subducting oceanic plates are generally young, which denies a possibility that the slab pull works as a cause. Except for Manila and Sumatra, the stresses in the overriding plates are characterized by the change in {σ }Hmax direction from arc-parallel in the back-arc to arc-perpendicular in the fore-arc, which implies that a horizontal stress gradient exists in the across-arc direction. Peru and Chile, where the back-arc is compressional, can be categorized into this type, because a horizontal stress gradient exists over the continent from tension in east to compression in the west. In these regions, it is expected that mantle drag forces are operating beneath the upper plates, which drive the upper plates to the trenchward overriding the subducting oceanic plates. Assuming that the mantle drag forces beneath the upper plates originate from the mantle convection currents or upwelling plumes, we infer that the upper plates driven by the convection suck the oceanic plates, making the shallow portion of the slabs in extra-tension, thus resulting in the large shallow slab earthquakes in this tectonic regime.

Reliability of Plastic Slabs

DEFF Research Database (Denmark)

Thoft-Christensen, Palle

1989-01-01

In the paper it is shown how upper and lower bounds for the reliability of plastic slabs can be determined. For the fundamental case it is shown that optimal bounds of a deterministic and a stochastic analysis are obtained on the basis of the same failure mechanisms and the same stress fields....

Dosimetry audit of radiotherapy treatment planning systems

International Nuclear Information System (INIS)

Bulski, Wojciech; Chelminski, Krzysztof; Rostkowska, Joanna

2015-01-01

In radiotherapy Treatment Planning Systems (TPS) various calculation algorithms are used. The accuracy of dose calculations has to be verified. Numerous phantom types, detectors and measurement methodologies are proposed to verify the TPS calculations with dosimetric measurements. A heterogeneous slab phantom has been designed within a Coordinated Research Project (CRP) of the IAEA. The heterogeneous phantom was developed in the frame of the IAEA CRP. The phantom consists of frame slabs made with polystyrene and exchangeable inhomogeneity slabs equivalent to bone or lung tissue. Special inserts allow to position thermoluminescent dosimeters (TLD) capsules within the polystyrene slabs below the bone or lung equivalent slabs and also within the lung equivalent material. Additionally, there are inserts that allow to position films or ionisation chamber in the phantom. Ten Polish radiotherapy centres (of 30 in total) were audited during on-site visits. Six different TPSs and five calculation algorithms were examined in the presence of inhomogeneities. Generally, most of the results from TLD were within 5 % tolerance. Differences between doses calculated by TPSs and measured with TLD did not exceed 4 % for bone and polystyrene equivalent materials. Under the lung equivalent material, on the beam axis the differences were lower than 5 %, whereas inside the lung equivalent material, off the beam axis, in some cases they were of around 7 %. The TLD results were confirmed with the ionisation chamber measurements. The comparison results of the calculations and the measurements allow to detect limitations of TPS calculation algorithms. The audits performed with the use of heterogeneous phantom and TLD seem to be an effective tool for detecting the limitations in the TPS performance or beam configuration errors at audited radiotherapy departments. (authors)

Structural behavior of lightweight bamboo reinforced concrete slab with EPS infill panel

Science.gov (United States)

Wibowo, Ari; Wijatmiko, Indradi; Nainggolan, Christin Remayanti

2017-09-01

Eco-friendly, green, and natural materials have become increasingly important issues in supporting sustainable development, for the substitution of nonrenewable materials such as steel. Bamboo has been considered in many studies to replace steel in reinforced concrete elements. Further investigation has been carried out to obtain lightweight and eco-friendly reinforced concrete slabs by using bamboo bars as reinforcement and recycled materials such as EPS (expanded polystyrene) as infill panel. The flexural loading test on full scale one-way slabs test has been conducted. The results showed that the flexural strength of specimens decreased marginally of about 6% but with the weight advantage of 27% less compared with those of steel rebar reinforced concrete slab with the same dimension. Two type shear-connectors comprising of concrete and bamboo studs were also investigated which showed that the bamboo stud provided better ductility compared to that of slab with concrete as shear connector. Overall, the reinforced concrete slab with bamboo reinforcement and EPS infill panel showed reasonably good performance compared to slabs with steel rebar.

Criticality Benchmark Analysis of Water-Reflected Uranium Oxyfluoride Slabs

International Nuclear Information System (INIS)

Marshall, Margaret A.; Bess, John D.

2009-01-01

A series of twelve experiments were conducted in the mid 1950's at the Oak Ridge National Laboratory Critical Experiments Facility to determine the critical conditions of a semi-infinite water-reflected slab of aqueous uranium oxyfluoride (UO2F2). A different slab thickness was used for each experiment. Results from the twelve experiment recorded in the laboratory notebook were published in Reference 1. Seven of the twelve experiments were determined to be acceptable benchmark experiments for the inclusion in the International Handbook of Evaluated Criticality Safety Benchmark Experiments. This evaluation will not only be available to handbook users for the validation of computer codes and integral cross-section data, but also for the reevaluation of experimental data used in the ANSI/ANS-8.1 standard. This evaluation is important as part of the technical basis of the subcritical slab limits in ANSI/ANS-8.1. The original publication of the experimental results was used for the determination of bias and bias uncertainties for subcritical slab limits, as documented by Hugh Clark's paper 'Subcritical Limits for Uranium-235 Systems'.

Flexural performance of steel fiber reinforced concrete (SFRC) ribbed slab with various topping thicknesses

Science.gov (United States)

Rahman, Fadhillah Abdul; Bakar, Afidah Abu; Hashim, Mohd Hisbany Mohd; Ahmad, Hazrina

2017-11-01

Ribbed slab provides lighter slab than an equivalent solid slab which helps in reducing the weight with its voids. However, in order to overcome the drawbacks in the construction process, the application of steel fibre reinforcement concrete (SFRC) is seen as an alternative material to be used in the slab. This study is performed to investigate the behaviour of SFRC as the main material in ribbed slab, omitting the conventional reinforcements, under four-point bending test. Three equivalent samples of ribbed slabs were prepared for this study with variations in the topping thickness of 100, 75 and 50 mm. The flexural strength of ribbed slab with 100 mm topping shows similar loading carrying capacity with the 75mm topping while 50 mm gave the lowest ultimate loading. First cracks for all slabs occurred at the topping. The cracks began from the external ribs and propagates toward the internal rib. Incorporation of steel fibres help in giving a longer deflection softening than a sudden brittle failure, thus proves its ability to increase energy absorption capacity and improving cracking behaviour.

Benchmarks on neutron leakage from iron and beryllium slabs and spheres

International Nuclear Information System (INIS)

Belousov, S.; Ilieva, K.; Popova, I.; Antonov, S.

1998-01-01

Five benchmarks, recommended by the IAEA for nuclear power engineering have been calculated for assessment of Iron and Beryllium neutron data from the recent FENDL version. The FENDL multigroup data processed in IAEA by NJOY code are in VITAMIN-J energy structure in MATXS format. These data have been converted to ANISN format by TRANSX code, ported to PC version and collected to binary library by LIBFENDL code, that we have created especially for this purpose. Neutron transport calculations have been carried out by the codes ANISN, GRTUNCL and DORT. The benchmark for neutron leakage from 25 cm radius Iron sphere with 252 Cf source posses to test FENDL Iron data for LWRs application. Other two benchmarks important for fusion application correspond to the 14 MeV neutron transmission through Iron sphere shell (Simakov S.P. et al., IPPE, Obninsk) and Iron slabs (Y. Oyama, H. Maekawa, FNS/ JAERI). The comparison of measured and calculation results demonstrates discouraged inconsistency when material thickness exceeds 20 cm. Modelling of the angular neutron leakage from 14 MeV source transmitted through Beryllium slabs (H. Maekawa and Y. Oyama at FNS/JAERI) and scalar neutron leakage spectra through sphere shell (Simakov S.P. at al in IPPE, Obninsk) is important for studding the multiplication properties of Beryllium as a fusion blanket material. The measured and calculated results are in relatively good consistency

Failure analysis of edge flat-slab column connections with shear reinforcement

OpenAIRE

Bompa, Dan V.; Muttoni, Aurelio

2013-01-01

Flat-slab column connections are susceptible to brittle failure, which lead to the necessity of improving ductility and ultimate strength. In case of edge connections, the behaviour at ultimate state is highly influenced by nonsymmetrical distribution of stresses originated by a moment transfer between the slab and the column. The paper presents the test results of three full-scale reinforced concrete flat-slab edge connections with stud-rail shear reinforcement subjected to concentrated load...

MOSFET dosimeter depth-dose measurements in heterogeneous tissue-equivalent phantoms at diagnostic x-ray energies

International Nuclear Information System (INIS)

Jones, A.K.; Pazik, F.D.; Hintenlang, D.E.; Bolch, W.E.

2005-01-01

The objective of the present study was to explore the use of the TN-1002RD metal-oxide-semiconductor field effect transistor (MOSFET) dosimeter for measuring tissue depth dose at diagnostic photon energies in both homogeneous and heterogeneous tissue-equivalent materials. Three cylindrical phantoms were constructed and utilized as a prelude to more complex measurements within tomographic physical phantoms of pediatric patients. Each cylindrical phantom was constructed as a stack of seven 5-cm-diameter and 1-cm-thick discs of materials radiographically representative of either soft tissue (S), bone (B), or lung tissue (L) at diagnostic photon energies. In addition to a homogeneous phantom of soft tissue (SSSSSSS), two heterogeneous phantoms were constructed: SSBBSSS and SBLLBSS. MOSFET dosimeters were then positioned at the interface of each disc, and the phantoms were then irradiated at 66 kVp and 200 mAs. Measured values of absorbed dose at depth were then compared to predicated values of point tissue dose as determined via Monte Carlo radiation transport modeling. At depths exceeding 2 cm, experimental results matched the computed values of dose with high accuracy regardless of the dosimeter orientation (epoxy bubble facing toward or away from the x-ray beam). Discrepancies were noted, however, between measured and calculated point doses near the surface of the phantom (surface to 2 cm depth) when the dosimeters were oriented with the epoxy bubble facing the x-ray beam. These discrepancies were largely eliminated when the dosimeters were placed with the flat side facing the x-ray beam. It is therefore recommended that the MOSFET dosimeters be oriented with their flat sides facing the beam when they are used at shallow depths or on the surface of either phantoms or patients

A study on depth-scaling of plastic phantom in electron beam dosimetry

International Nuclear Information System (INIS)

Kojima, T.; Saitoh, H.; Kawachi, T.; Katayose, T.; Myojyoyama, A.

2005-01-01

In recommendations of several standard dosimetry, water is defined as the reference medium, however, the water substitute plastic phantoms are highly discouraged. Nevertheless, in the case of accurate chamber positioning in water is not possible, or no waterproof chamber is available, their use is permitted at beam qualities R 50 2 (E 0 pl obtained from a ratio of electron average penetration depth; z av , half value depth ratio; (R 50 ) w,m from Monte Carlo dose calculation and that from measurements, are compared each other. As a result, there are slight differences in depth-scaling factor between obtained from simulation results and from measurements. These results indicate that c pl has to be studied more detail for the sake of precise electron dosimetry in plastic phantoms. (author)

Kinetic theory of neutrals in a bounded plasma slab with inhomogeneous temperature and density profile

International Nuclear Information System (INIS)

Tendler, M.B.; Agren, O.

1982-01-01

The transport of neutral hydrogen atoms in a hydrogen plasma slab is considered. The influence of the inhomogeneous ion temperature profile on the neutral density and distribution is discussed as well as the influence of the neutral edge energy, charge exchange, and ionization rates. The analytical solutions for the neutral density and distribution function are obtained and compared with the numerical results. The effects due to the inhomogeneous temperature profile are discussed. The recommen-dations from the viewpoint of the effects mentioned previously for the purposes of the cold-gas mantle system have been given

Field Enhancement in a Grounded Dielectric Slab by Using a Single Superstrate Layer

OpenAIRE

Valagiannopoulos, Constantinos A.; Tsitsas, Nikolaos L.

2012-01-01

The addition of a dielectric layer on a slab configuration is frequently utilized in various electromagnetic devices in order to give them certain desired operational characteristics. In this work, we consider a grounded dielectric film-slab, which is externally excited by a normally-incident Gaussian beam. On top of the film-slab, we use an additional suitably selected single isotropic superstrate layer in order to increase the field concentration inside the slab and hence achieve optimal po...

A computer-simulated liver phantom (virtual liver phantom) for multidetector computed tomography evaluation

Energy Technology Data Exchange (ETDEWEB)

Funama, Yoshinori [Kumamoto University, Department of Radiological Sciences, School of Health Sciences, Kumamoto (Japan); Awai, Kazuo; Nakayama, Yoshiharu; Liu, Da; Yamashita, Yasuyuki [Kumamoto University, Department of Diagnostic Radiology, Graduate School of Medical Sciences, Kumamoto (Japan); Miyazaki, Osamu; Goto, Taiga [Hitachi Medical Corporation, Tokyo (Japan); Hori, Shinichi [Gate Tower Institute of Image Guided Therapy, Osaka (Japan)

2006-04-15

The purpose of study was to develop a computer-simulated liver phantom for hepatic CT studies. A computer-simulated liver phantom was mathematically constructed on a computer workstation. The computer-simulated phantom was calibrated using real CT images acquired by an actual four-detector CT. We added an inhomogeneous texture to the simulated liver by referring to CT images of chronically damaged human livers. The mean CT number of the simulated liver was 60 HU and we added numerous 5-to 10-mm structures with 60{+-}10 HU/mm. To mimic liver tumors we added nodules measuring 8, 10, and 12 mm in diameter with CT numbers of 60{+-}10, 60{+-}15, and 60{+-}20 HU. Five radiologists visually evaluated similarity of the texture of the computer-simulated liver phantom and a real human liver to confirm the appropriateness of the virtual liver images using a five-point scale. The total score was 44 in two radiologists, and 42, 41, and 39 in one radiologist each. They evaluated that the textures of virtual liver were comparable to those of human liver. Our computer-simulated liver phantom is a promising tool for the evaluation of the image quality and diagnostic performance of hepatic CT imaging. (orig.)

Tomography of the subducting Pacific slab and the 2015 Bonin deepest earthquake (Mw 7.9)

Science.gov (United States)

Zhao, Dapeng; Fujisawa, Moeto; Toyokuni, Genti

2017-03-01

On 30 May 2015 an isolated deep earthquake (~670 km, Mw 7.9) occurred to the west of the Bonin Islands. To clarify its causal mechanism and its relationship to the subducting Pacific slab, we determined a detailed P-wave tomography of the deep earthquake source zone using a large number of arrival-time data. Our results show that this large deep event occurred within the subducting Pacific slab which is penetrating into the lower mantle. In the Izu-Bonin region, the Pacific slab is split at ~28° north latitude, i.e., slightly north of the 2015 deep event hypocenter. In the north the slab becomes stagnant in the mantle transition zone, whereas in the south the slab is directly penetrating into the lower mantle. This deep earthquake was caused by joint effects of several factors, including the Pacific slab’s fast deep subduction, slab tearing, slab thermal variation, stress changes and phase transformations in the slab, and complex interactions between the slab and the ambient mantle.

Lateral force resisting mechanisms in slab-column connections: An analytical approach

OpenAIRE

Drakatos, Iaonnis; Beyer, Katrin; Muttoni, Aurelio

2014-01-01

In many countries reinforced concrete (RC) flat slabs supported on columns is one of the most commonly used structural systems for office and industrial buildings. To increase the lateral stiffness and strength of the structure, RC walls are typically added and carry the largest portion of the horizontal loads generated during earthquakes. While the slab-column system is typically not relevant with regard to the lateral stiffness and strength of the structure, each slab-column connection has ...

Evolution and diversity of subduction zones controlled by slab width

NARCIS (Netherlands)

Schellart, W. P.; Freeman, J.A.; Stegman, D. R.; Moresi, L.; May, D.

2007-01-01

Subducting slabs provide the main driving force for plate motion and flow in the Earth's mantle, and geodynamic, seismic and geochemical studies offer insight into slab dynamics and subduction-induced flow. Most previous geodynamic studies treat subduction zones as either infinite in trench-parallel

Behavior of one-way reinforced concrete slabs subjected to fire

Directory of Open Access Journals (Sweden)

Said M. Allam

2013-12-01

Full Text Available A finite difference analysis was performed to investigate the behavior of one-way reinforced concrete slabs exposed to fire. The objective of the study was to investigate the fire resistance and the fire risk after extinguishing the fire. Firstly, the fire resistance was obtained using the ISO834 standard fire without cooling phase. Secondly, the ISO834 parametric fire with cooling phase was applied to study the effect of cooling time. Accordingly, the critical time for cooling was identified and the corresponding failure time was calculated. Moreover, the maximum risk time which is the time between the fire extinguishing and the collapse of slab was obtained. Sixteen one-way reinforced concrete slabs were considered to study the effect of important parameters namely: the concrete cover thickness; the plaster; and the live load ratio. Equations for heat transfer through the slab thickness were used in the fire resistance calculations. Studying the cooling time revealed that the slabs are still prone to collapse although they were cooled before their fire resistance. Moreover, increasing the concrete cover thickness and the presence of plaster led to an increase in the maximum risk time. However, the variation in the live load ratio has almost no effect on such time.

Retrieving the characteristics of slab ice covering snow by remote sensing

Directory of Open Access Journals (Sweden)

F. Andrieu

2016-09-01

Full Text Available We present an effort to validate a previously developed radiative transfer model, and an innovative Bayesian inversion method designed to retrieve the properties of slab-ice-covered surfaces. This retrieval method is adapted to satellite data, and is able to provide uncertainties on the results of the inversions. We focused on surfaces composed of a pure slab of water ice covering an optically thick layer of snow in this study. We sought to retrieve the roughness of the ice–air interface, the thickness of the slab layer and the mean grain diameter of the underlying snow. Numerical validations have been conducted on the method, and showed that if the thickness of the slab layer is above 5 mm and the noise on the signal is above 3 %, then it is not possible to invert the grain diameter of the snow. In contrast, the roughness and the thickness of the slab can be determined, even with high levels of noise up to 20 %. Experimental validations have been conducted on spectra collected from laboratory samples of water ice on snow using a spectro-radiogoniometer. The results are in agreement with the numerical validations, and show that a grain diameter can be correctly retrieved for low slab thicknesses, but not for bigger ones, and that the roughness and thickness are correctly inverted in every case.

Cost Effectiveness of Precast Reinforced Concrete Roof Slabs

Science.gov (United States)

Parskiy, N. D.; Molodtsov, M. V.; Molodtsova, V. E.

2017-11-01

Engineers always seek to free interior space from intermediate supporting elements. Nowadays plants, being at the forefront of technology, produce a new generation of exclusive patented prefabricated reinforced concrete elements with a high load-bearing capacity, excellent heat resistance characteristics combined with the aesthetics and beauty. It is a system of Seagull Gabbiano prestressed roof slabs for the spans of 12m - 40m. The article shows the advantages of the Seagull slabs over conventional precast reinforced concrete and metal roof trusses. It also gives the analysis of the technical and economic indices of design and construction of a building with the Seagull slabs depending on the size of spans to cover. The use of structural systems with increased spans allows for the modern buildings and structures of prefabricated reinforced concrete with enhanced functionality and aesthetics alongside with a wide range of planning solutions.

330 mJ single-frequency Ho:YLF slab amplifier

CSIR Research Space (South Africa)

Strauss, HJ

2013-04-01

Full Text Available We report on a double-pass Ho:YLF slab amplifier which delivered 350 ns long single-frequency pulses of up to 330 mJ at 2064 nm, with a maximum M(sup2) of 1.5 at 50 Hz. It was end pumped with a diode-pumped Tm:YLF slab laser and seeded with up to 50...

Evaluation of anterior urethral stricture using thick slab SSFSE MR urethrography

Energy Technology Data Exchange (ETDEWEB)

Park, Byung Kwan; Kim, Chan Kyo (Dept. of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan Univ. School of Medicine, Seoul (Korea)), e-mail: rapark@skku.edu; Lee, Sung Won (Dept. of Urology, Samsung Medical Center, Sungkyunkwan Univ. School of Medicine, Seoul (Korea))

2010-12-15

Background: Magnetic resonance urethrography (MRU) can be used for depicting not only anterior urethral strictures but also periurethral anatomy in order to produce a management plan. Purpose: To determine if thick slab single-shot fast spin echo (SSFSE) MRU is useful for evaluating anterior urethral stricture compared to fast recovery fast spin echo (FRFSE) MRU. Material and Methods: Ten patients with benign anterior urethral stricture underwent both thick slab SSFSE MRU and FRFSE MRU using sterile jelly for urethral distension before retrograde urethrography. The glans penis was tied at the time of MRU. The two types of MR image were compared regarding stricture length, scan time, and image quality. We also determined whether or not both of the two MR sequences could display an entire anterior urethra on one image. Results: The stricture length on thick slab SSFSE and FRFSE MRU ranged from 4.0 to 71.3 mm (36.4 {+-} 21.8 mm) and from 4.0 to 67.5 mm (35.7 {+-} 20.8 mm), respectively (P > 0.05). The mean scan time for thick slab SSFSE and FRFSE sequences was 2 s and 194 s, respectively (P < 0.05). However, regarding image quality, thick slab SSFSE MRU was inferior to FRFSE MRU (P < 0.05). All the thick slab SSFSE MRU displayed the entire anterior urethra on one image, while only five FRFSE MRU did so (P < 0.05). Conclusion: Thick slab SSFSE MRU can provide a concordant stricture length when compared to the FRFSE MRU and imaging of the entire length of the anterior urethral stricture with subjective reduced image quality and scan time.

Evaluation of anterior urethral stricture using thick slab SSFSE MR urethrography

International Nuclear Information System (INIS)

Park, Byung Kwan; Kim, Chan Kyo; Lee, Sung Won

2010-01-01

Background: Magnetic resonance urethrography (MRU) can be used for depicting not only anterior urethral strictures but also periurethral anatomy in order to produce a management plan. Purpose: To determine if thick slab single-shot fast spin echo (SSFSE) MRU is useful for evaluating anterior urethral stricture compared to fast recovery fast spin echo (FRFSE) MRU. Material and Methods: Ten patients with benign anterior urethral stricture underwent both thick slab SSFSE MRU and FRFSE MRU using sterile jelly for urethral distension before retrograde urethrography. The glans penis was tied at the time of MRU. The two types of MR image were compared regarding stricture length, scan time, and image quality. We also determined whether or not both of the two MR sequences could display an entire anterior urethra on one image. Results: The stricture length on thick slab SSFSE and FRFSE MRU ranged from 4.0 to 71.3 mm (36.4 21.8 mm) and from 4.0 to 67.5 mm (35.7 20.8 mm), respectively (P > 0.05). The mean scan time for thick slab SSFSE and FRFSE sequences was 2 s and 194 s, respectively (P < 0.05). However, regarding image quality, thick slab SSFSE MRU was inferior to FRFSE MRU (P < 0.05). All the thick slab SSFSE MRU displayed the entire anterior urethra on one image, while only five FRFSE MRU did so (P < 0.05). Conclusion: Thick slab SSFSE MRU can provide a concordant stricture length when compared to the FRFSE MRU and imaging of the entire length of the anterior urethral stricture with subjective reduced image quality and scan time.

A vibrating wire parallel to a high temperature superconducting slab. Vol. 2

Energy Technology Data Exchange (ETDEWEB)

Saif, A G; El-sabagh, M A [Department of Mathematic and Theoretical physics, Nuclear Research Center, Atomic Energy Authority, Cairo (Egypt)

1996-03-01

The power losses problem for an idealized high temperature type II superconducting system of a simple geometry is studied. This system is composed of a vibrating normal conducting wire (two wires) carrying a direct current parallel to an uniaxial anisotropic type II superconducting slab (moving slab). First, the electromagnetic equation governing the dynamics of this system, and its solutions are obtained. Secondly, a modified anisotropic london equation is developed to study these systems in the case of the slab moving. Thirdly, it is found that, the power losses is dependent on the frequency, london penetration depth, permeability, conductivity, velocity, and the distance between the normal conductors and the surfaces of the superconducting slab. Moreover, the power losses decreases as the distance between the normal conductors and the surface of the superconducting slab decreases; and increases as the frequency, the london penetration depth, permeability, conductivity, and velocity are increased. These losses along the versor of the anisotropy axis is increased as {lambda}{sub |}| increases. Moreover, it is greater than the power losses along the crystal symmetry direction. In the isotropic case as well as the slab thickness tends to infinity, agreement with previous results are obtained. 2 figs.

Active isotropic slabs: conditions for amplified reflection

Science.gov (United States)

Perez, Liliana I.; Matteo, Claudia L.; Etcheverry, Javier; Duplaá, María Celeste

2012-12-01

We analyse in detail the necessary conditions to obtain amplified reflection (AR) in isotropic interfaces when a plane wave propagates from a transparent medium towards an active one. First, we demonstrate analytically that AR is not possible if a single interface is involved. Then, we study the conditions for AR in a very simple configuration: normal incidence on an active slab immersed in transparent media. Finally, we develop an analysis in the complex plane in order to establish a geometrical method that not only describes the behaviour of active slabs but also helps to simplify the calculus.

Active isotropic slabs: conditions for amplified reflection

International Nuclear Information System (INIS)

Perez, Liliana I; Duplaá, María Celeste; Matteo, Claudia L; Etcheverry, Javier

2012-01-01

We analyse in detail the necessary conditions to obtain amplified reflection (AR) in isotropic interfaces when a plane wave propagates from a transparent medium towards an active one. First, we demonstrate analytically that AR is not possible if a single interface is involved. Then, we study the conditions for AR in a very simple configuration: normal incidence on an active slab immersed in transparent media. Finally, we develop an analysis in the complex plane in order to establish a geometrical method that not only describes the behaviour of active slabs but also helps to simplify the calculus. (paper)

Cross-field flow and electric potential in a plasma slab

Directory of Open Access Journals (Sweden)

J. De Keyser

2013-08-01

Full Text Available We consider cross-field plasma flow inside a field-aligned plasma slab embedded in a uniform background in a 1-dimensional geometry. This situation may arise, for instance, when long-lasting reconnection pulses inject plasma into the inner magnetosphere. The present paper presents a detailed analysis of the structure of the interfaces that separate the slab from the background plasma on either side; a fully kinetic model is used to do so. Since the velocity shear across both interfaces has opposite signs, and given the typical gyroradius differences between injected and background ions and electrons, the structure of both interfaces can be very different. The behaviour of the slab and its interfaces depends critically on the flow of the plasma transverse to the magnetic field; in particular, it is shown that there are bounds to the flow speed that can be supported by the magnetised plasma. Further complicating the picture is the effect of the potential difference between the slab and its environment.

Slab Geometry and Stress State of the Southwestern Colombia Subduction Zone

Science.gov (United States)

Chang, Ying

A high rate of intermediate-depth earthquakes is concentrates in the Cauca cluster (3.5°N-5.5°N) and isolated from nearby seismicity in the southwestern Colombia subduction zone. Previously-studied nests of intermediate-depth earthquakes show that a high seismicity rate is often associated with a slab tear, detachment, or contortion. The cause of the less-studied Cauca cluster is unknown. To investigate the cause, we image the slab geometry using precise relative locations of intermediate-depth earthquakes. We use the earthquake catalog produced and seismic waveforms recorded by the Colombian National Seismic Network from January 2010 to March 2014. We calculate the focal mechanisms to examine whether the earthquakes reactivate pre-existing faults or form new fractures. The focal mechanisms are inverted for the intraslab stress field to check the stress guide hypothesis and to evaluate the stress orientations with regard to the change in the slab geometry. The earthquake relocations indicate that the Cauca segment has a continuous 20 km thick seismic zone and increases in dip angle from north to south. Two 40-km-tall fingers of earthquakes extend out of the slab and into the mantle wedge. Different from the previously-studied nests, the Cauca cluster does not correspond to slab contortions or tearing. The cluster may be associated with a high amount of dehydrated fluid. The determined focal mechanisms of 69 earthquakes have various types and variably-oriented nodal planes, corresponding to the reactivation of pre-existing faults and the formation of new fractures. The results of stress inversion show that the extensional axis in the northern Cauca segment is in the plane of the slab and 25° from the downdip direction, and the southern part has along-strike extension. The compression is subnormal to the plane of the slab. The stress field supports the stress guide hypothesis and shows a consistent rotation with increase in slab dip angle.

Effect of phantom voxelization in CT simulations

International Nuclear Information System (INIS)

Goertzen, Andrew L.; Beekman, Freek J.; Cherry, Simon R.

2002-01-01

In computer simulations of x-ray CT systems one can either use continuous geometrical descriptions for phantoms or a voxelized representation. The voxelized approach allows arbitrary phantoms to be defined without being confined to geometrical shapes. The disadvantage of the voxelized approach is that inherent errors are introduced due to the phantom voxelization. To study effects of phantom discretization, analytical CT simulations were run for a fan-beam geometry with phantom voxel sizes ranging from 0.0625 to 2 times the reconstructed pixel size and noise levels corresponding to 10 3 -10 7 photons per detector pixel prior to attenuation. The number of rays traced per detector element was varied from 1 to 16. Differences in the filtered backprojection images caused by changing the phantom matrix sizes and number of rays traced were assessed by calculating the difference between reconstructions based on the finest matrix and coarser matrix simulations. In noise free simulations, all phantom matrix sizes produced a measurable difference in comparison with the finest phantom matrix used. When even a small amount of noise was added to the projection data, the differences due to the phantom discretization were masked by the noise, and in all cases there was almost no improvement by using a phantom matrix that was more than twice as fine as the reconstruction matrix. No substantial improvement was achieved by tracing more than 4 rays per detector pixel

Vibration Analysis of Beam and Block Precast Slab System due to Human Vibrations

Science.gov (United States)

Chik, T. N. T.; Kamil, M. R. H.; Yusoff, N. A.

2018-04-01

Beam and block precast slabs system are very efficient which generally give maximum structural performance where their voids based on the design of the unit soffit block allow a significant reduction of the whole slab self-weight. Initially for some combinations of components or the joint connection of the structural slab, this structural system may be susceptible to excessive vibrations that could effects the performance and also serviceability. Dynamic forces are excited from people walking and jumping which produced vibrations to the slab system in the buildings. Few studies concluded that human induced vibration on precast slabs system may be harmful to structural performance and mitigate the human comfort level. This study will investigate the vibration analysis of beam and block precast slab by using finite element method at the school building. Human activities which are excited from jumping and walking will induce the vibrations signal to the building. Laser Doppler Vibrometer (LDV) was used to measure the dynamic responses of slab towards the vibration sources. Five different points were assigned specifically where each of location will determine the behaviour of the entire slabs. The finite element analyses were developed in ABAQUS software and the data was further processed in MATLAB ModalV to assess the vibration criteria. The results indicated that the beam and block precast systems adequate enough to the vibration serviceability and human comfort criteria. The overall vibration level obtained was fell under VC-E curve which it is generally under the maximum permissible level of vibrations. The vibration level on the slab is acceptable within the limit that have been used by Gordon.

Quantitative analysis of multiple biokinetic models using a dynamic water phantom: A feasibility study

Science.gov (United States)

Chiang, Fu-Tsai; Li, Pei-Jung; Chung, Shih-Ping; Pan, Lung-Fa; Pan, Lung-Kwang

2016-01-01

ABSTRACT This study analyzed multiple biokinetic models using a dynamic water phantom. The phantom was custom-made with acrylic materials to model metabolic mechanisms in the human body. It had 4 spherical chambers of different sizes, connected by 8 ditches to form a complex and adjustable water loop. One infusion and drain pole connected the chambers to an auxiliary silicon-based hose, respectively. The radio-active compound solution (TC-99m-MDP labeled) formed a sealed and static water loop inside the phantom. As clean feed water was infused to replace the original solution, the system mimicked metabolic mechanisms for data acquisition. Five cases with different water loop settings were tested and analyzed, with case settings changed by controlling valve poles located in the ditches. The phantom could also be changed from model A to model B by transferring its vertical configuration. The phantom was surveyed with a clinical gamma camera to determine the time-dependent intensity of every chamber. The recorded counts per pixel in each chamber were analyzed and normalized to compare with theoretical estimations from the MATLAB program. Every preset case was represented by uniquely defined, time-dependent, simultaneous differential equations, and a corresponding MATLAB program optimized the solutions by comparing theoretical calculations and practical measurements. A dimensionless agreement (AT) index was recommended to evaluate the comparison in each case. ATs varied from 5.6 to 48.7 over the 5 cases, indicating that this work presented an acceptable feasibility study. PMID:27286096

Review of Punching Shear Behaviour of Flat Slabs Reinforced with FRP Bars

Science.gov (United States)

Mohamed, Osama A.; Khattab, Rania

2017-10-01

Using Fibre Reinforced Polymer (FRP) bars to reinforce two-way concrete slabs can extend the service life, reduce maintenance cost and improve-life cycle cost efficiency. FRP reinforcing bars are more environmentally friendly alternatives to traditional reinforcing steel. Shear behaviour of reinforced concrete structural members is a complex phenomenon that relies on the development of internal load-carrying mechanisms, the magnitude and combination of which is still a subject of research. Many building codes and design standards provide design formulas for estimation of punching shear capacity of FRP reinforced flat slabs. Building code formulas take into account the effects of the axial stiffness of main reinforcement bars, the ratio of the perimeter of the critical section to the slab effective depth, and the slab thickness on the punching shear capacity of two-way slabs reinforced with FRP bars or grids. The goal of this paper is to compare experimental data published in the literature to the equations offered by building codes for the estimation of punching shear capacity of concrete flat slabs reinforced with FRP bars. Emphasis in this paper is on two North American codes, namely, ACI 440.1R-15 and CSA S806-12. The experimental data covered in this paper include flat slabs reinforced with GFRP, BFRP, and CFRP bars. Both ACI 440.1R-15 and CSA S806-12 are shown to be in good agreement with test results in terms of predicting the punching shear capacity.

MRI quality assurance using the ACR phantom in a multi-unit imaging center

International Nuclear Information System (INIS)

Ihalainen, Toni M.; Kuusela, Linda J.; Savolainen, Sauli E.; Loennroth, Nadja T.; Peltonen, Juha I.; Uusi-Simola, Jouni K.; Timonen, Marjut H.; Sipilae, Outi E.

2011-01-01

Background. Magnetic resonance imaging (MRI) instrumentation is vulnerable to technical and image quality problems, and quality assurance is essential. In the studied regional imaging center the long-term quality assurance has been based on MagNET phantom measurements. American College of Radiology (ACR) has an accreditation program including a standardized image quality measurement protocol and phantom. The ACR protocol includes recommended acceptance criteria for clinical sequences and thus provides possibility to assess the clinical relevance of quality assurance. The purpose of this study was to test the ACR MRI phantom in quality assurance of a multi-unit imaging center. Material and methods. The imaging center operates 11 MRI systems of three major manufacturers with field strengths of 3.0 T, 1.5 T and 1.0 T. Images of the ACR phantom were acquired using a head coil following the ACR scanning instructions. Both ACR T1- and T2-weighted sequences as well as T1- and T2-weighted brain sequences in clinical use at each site were acquired. Measurements were performed twice. The images were analyzed and the results were compared with the ACR acceptance levels. Results. The acquisition procedure with the ACR phantom was faster than with the MagNET phantoms. On the first and second measurement rounds 91% and 73% of the systems passed the ACR test. Measured slice thickness accuracies were not within the acceptance limits in site T2 sequences. Differences in the high contrast spatial resolution between the ACR and the site sequences were observed. In 3.0 T systems the image intensity uniformity was slightly lower than the ACR acceptance limit. Conclusion. The ACR method was feasible in quality assurance of a multi-unit imaging center and the ACR protocol could replace the MagNET phantom tests. An automatic analysis of the images will further improve cost-effectiveness and objectiveness of the ACR protocol

Study on quantities of radiation protection in medical X-rays radiation field with polyhedron phantom

International Nuclear Information System (INIS)

Yuan Shuyu; Dai Guangfu; Zhang Liangan

1997-01-01

The author have studied tissue-equivalent material with the elemental composition recommended by report No.44 of ICRU. Three different calibration phantoms in shape have been prepared with the tissue-equivalent material in order to study the influence of the angular dependence factor R(d,α) in the radiation field of X-rays on the calibration of individual dose equivalent Hp(d). The requirement of mono-genous radiation field to calibrate several dosimeters on one phantom at the same time can be met by application of dodecahedron phantom, which is difficult on ICRU sphere. Angular dependence factor R(d,α) of 0 degree∼90 degree and conversion coefficients between individual dose equivalent Hp(0.07, α) and the exposure of radiation of different energies and different angles have been established by taking advantage of the dodecahedron. Besides, the authors have studied the variation relation between the individual dose equivalent Hp (10,α) and Hp(0.07,α) in the medical X-rays radiation field

Novel biometric flow slab design for improvement of PEMFC performance

Energy Technology Data Exchange (ETDEWEB)

Wang, Chin-Tsan; Hu, Yuh-Chung; Zheng, Pei-Lun [Department of Mechanical and Electro-Mechanical Engineering, Center of Green Technology, National I Lan University, I Lan 26047 (China)

2010-04-15

Designing a better flow slab is important to cell performance because of its significant influence on the total pressure drop and flow uniformity. Two novel biometric flow slabs, BFF1 and BFF2, which are addressed in this study, are believed to enhance the capability of oxygen transportation and promote the liquid water removal. Hence, its possession of a higher flow uniformity and lower pressure drop would produce a better power performance than the serpentine and parallel flow. These findings with respect to the design of biometric flow slab could be useful to promote the cell performance of PEMFC, and could even be expanded to other cell types. (author)

Study on the electromagnetic waves propagation characteristics in partially ionized plasma slabs

Directory of Open Access Journals (Sweden)

Zhi-Bin Wang

2016-05-01

Full Text Available Propagation characteristics of electromagnetic (EM waves in partially ionized plasma slabs are studied in this paper. Such features are significant to applications in plasma antennas, blackout of re-entry flying vehicles, wave energy injection to plasmas, and etc. We in this paper developed a theoretical model of EM wave propagation perpendicular to a plasma slab with a one-dimensional density inhomogeneity along propagation direction to investigate essential characteristics of EM wave propagation in nonuniform plasmas. Particularly, the EM wave propagation in sub-wavelength plasma slabs, where the geometric optics approximation fails, is studied and in comparison with thicker slabs where the geometric optics approximation applies. The influences of both plasma and collisional frequencies, as well as the width of the plasma slab, on the EM wave propagation characteristics are discussed. The results can help the further understanding of propagation behaviours of EM waves in nonuniform plasma, and applications of the interactions between EM waves and plasmas.

Effects of Metamaterial Slabs Applied to Wireless Power Transfer at 13.56 MHz

Directory of Open Access Journals (Sweden)

Gunyoung Kim

2015-01-01

Full Text Available This paper analyzes the effects of a metamaterial slab (or a practical “perfect lens” with negative permeability applied to a two loop magnetically coupled wireless power transfer (WPT system at 13.56 MHz, based on theory, full-wave electromagnetic- (EM- simulations, and measurements. When using lossless slabs with ideal negative permeability in EM-simulations, the WPT efficiencies have been found to be enhanced close to 100% due to the magnetic field focusing. For the case of using a realistic slab made of ring resonators (RR μr=-1-j0.23 with s/d=0.5 (s: slab width, d: distance between the transmitting and receiving loops, the WPT efficiency has been found to significantly decrease to about 20%, even lower than that of a free space case (32% due to the heavy power absorption in the slab. However, some efficiency enhancement can be achieved when s/d is optimized between 0.1 and 0.3. Overall, the significant enhancement of efficiencies when using a lossless slab becomes moderate or only marginal when employing a realistic slab.

The Green's function method for critical heterogeneous slabs

International Nuclear Information System (INIS)

Kornreich, D.E.

1996-01-01

Recently, the Green's Function Method (GFM) has been employed to obtain benchmark-quality results for nuclear engineering and radiative transfer calculations. This was possible because of fast and accurate calculations of the Green's function and the associated Fourier and Laplace transform inversions. Calculations have been provided in one-dimensional slab geometries for both homogeneous and heterogeneous media. A heterogeneous medium is analyzed as a series of homogeneous slabs, and Placzek's lemma is used to extend each slab to infinity. This allows use of the infinite medium Green's function (the anisotropic plane source in an infinite homogeneous medium) in the solution. To this point, a drawback of the GFM has been the limitation to media with c 1; however, mathematical solutions exist which result in oscillating Green's functions. Such calculations are briefly discussing. The limitation to media with c < 1 has been relaxed so that the Green's function may also be calculated for media with c ≥ 1. Thus, materials that contain fissionable isotopes may be modeled

Dosimetry audit of radiotherapy treatment planning systems.

Science.gov (United States)

Bulski, Wojciech; Chełmiński, Krzysztof; Rostkowska, Joanna

2015-07-01

In radiotherapy Treatment Planning Systems (TPS) various calculation algorithms are used. The accuracy of dose calculations has to be verified. Numerous phantom types, detectors and measurement methodologies are proposed to verify the TPS calculations with dosimetric measurements. A heterogeneous slab phantom has been designed within a Coordinated Research Project (CRP) of the IAEA. The heterogeneous phantom was developed in the frame of the IAEA CRP. The phantom consists of frame slabs made with polystyrene and exchangeable inhomogeneity slabs equivalent to bone or lung tissue. Special inserts allow to position thermoluminescent dosimeters (TLD) capsules within the polystyrene slabs below the bone or lung equivalent slabs and also within the lung equivalent material. Additionally, there are inserts that allow to position films or ionisation chamber in the phantom. Ten Polish radiotherapy centres (of 30 in total) were audited during on-site visits. Six different TPSs and five calculation algorithms were examined in the presence of inhomogeneities. Generally, most of the results from TLD were within 5 % tolerance. Differences between doses calculated by TPSs and measured with TLD did not exceed 4 % for bone and polystyrene equivalent materials. Under the lung equivalent material, on the beam axis the differences were lower than 5 %, whereas inside the lung equivalent material, off the beam axis, in some cases they were of around 7 %. The TLD results were confirmed with the ionisation chamber measurements. The comparison results of the calculations and the measurements allow to detect limitations of TPS calculation algorithms. The audits performed with the use of heterogeneous phantom and TLD seem to be an effective tool for detecting the limitations in the TPS performance or beam configuration errors at audited radiotherapy departments. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Phantom cosmologies and fermions

International Nuclear Information System (INIS)

Chimento, Luis P; Forte, Monica; Devecchi, Fernando P; Kremer, Gilberto M

2008-01-01

Form invariance transformations can be used for constructing phantom cosmologies starting with conventional cosmological models. In this work we reconsider the scalar field case and extend the discussion to fermionic fields, where the 'phantomization' process exhibits a new class of possible accelerated regimes. As an application we analyze the cosmological constant group for a fermionic seed fluid

Performance of two commercial electron beam algorithms over regions close to the lung-mediastinum interface, against Monte Carlo simulation and point dosimetry in virtual and anthropomorphic phantoms.

Science.gov (United States)

Ojala, J; Hyödynmaa, S; Barańczyk, R; Góra, E; Waligórski, M P R

2014-03-01

Electron radiotherapy is applied to treat the chest wall close to the mediastinum. The performance of the GGPB and eMC algorithms implemented in the Varian Eclipse treatment planning system (TPS) was studied in this region for 9 and 16 MeV beams, against Monte Carlo (MC) simulations, point dosimetry in a water phantom and dose distributions calculated in virtual phantoms. For the 16 MeV beam, the accuracy of these algorithms was also compared over the lung-mediastinum interface region of an anthropomorphic phantom, against MC calculations and thermoluminescence dosimetry (TLD). In the phantom with a lung-equivalent slab the results were generally congruent, the eMC results for the 9 MeV beam slightly overestimating the lung dose, and the GGPB results for the 16 MeV beam underestimating the lung dose. Over the lung-mediastinum interface, for 9 and 16 MeV beams, the GGPB code underestimated the lung dose and overestimated the dose in water close to the lung, compared to the congruent eMC and MC results. In the anthropomorphic phantom, results of TLD measurements and MC and eMC calculations agreed, while the GGPB code underestimated the lung dose. Good agreement between TLD measurements and MC calculations attests to the accuracy of "full" MC simulations as a reference for benchmarking TPS codes. Application of the GGPB code in chest wall radiotherapy may result in significant underestimation of the lung dose and overestimation of dose to the mediastinum, affecting plan optimization over volumes close to the lung-mediastinum interface, such as the lung or heart. Copyright © 2013 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

A statistically defined anthropomorphic software breast phantom

International Nuclear Information System (INIS)

Lau, Beverly A.; Reiser, Ingrid; Nishikawa, Robert M.; Bakic, Predrag R.

2012-01-01

Purpose: Digital anthropomorphic breast phantoms have emerged in the past decade because of recent advances in 3D breast x-ray imaging techniques. Computer phantoms in the literature have incorporated power-law noise to represent glandular tissue and branching structures to represent linear components such as ducts. When power-law noise is added to those phantoms in one piece, the simulated fibroglandular tissue is distributed randomly throughout the breast, resulting in dense tissue placement that may not be observed in a real breast. The authors describe a method for enhancing an existing digital anthropomorphic breast phantom by adding binarized power-law noise to a limited area of the breast. Methods: Phantoms with (0.5 mm) 3 voxel size were generated using software developed by Bakic et al. Between 0% and 40% of adipose compartments in each phantom were replaced with binarized power-law noise (β = 3.0) ranging from 0.1 to 0.6 volumetric glandular fraction. The phantoms were compressed to 7.5 cm thickness, then blurred using a 3 × 3 boxcar kernel and up-sampled to (0.1 mm) 3 voxel size using trilinear interpolation. Following interpolation, the phantoms were adjusted for volumetric glandular fraction using global thresholding. Monoenergetic phantom projections were created, including quantum noise and simulated detector blur. Texture was quantified in the simulated projections using power-spectrum analysis to estimate the power-law exponent β from 25.6 × 25.6 mm 2 regions of interest. Results: Phantoms were generated with total volumetric glandular fraction ranging from 3% to 24%. Values for β (averaged per projection view) were found to be between 2.67 and 3.73. Thus, the range of textures of the simulated breasts covers the textures observed in clinical images. Conclusions: Using these new techniques, digital anthropomorphic breast phantoms can be generated with a variety of glandular fractions and patterns. β values for this new phantom are comparable

Convection in Slab and Spheroidal Geometries

Science.gov (United States)

Porter, David H.; Woodward, Paul R.; Jacobs, Michael L.

2000-01-01

Three-dimensional numerical simulations of compressible turbulent thermally driven convection, in both slab and spheroidal geometries, are reviewed and analyzed in terms of velocity spectra and mixing-length theory. The same ideal gas model is used in both geometries, and resulting flows are compared. The piecewise-parabolic method (PPM), with either thermal conductivity or photospheric boundary conditions, is used to solve the fluid equations of motion. Fluid motions in both geometries exhibit a Kolmogorov-like k(sup -5/3) range in their velocity spectra. The longest wavelength modes are energetically dominant in both geometries, typically leading to one convection cell dominating the flow. In spheroidal geometry, a dipolar flow dominates the largest scale convective motions. Downflows are intensely turbulent and up drafts are relatively laminar in both geometries. In slab geometry, correlations between temperature and velocity fluctuations, which lead to the enthalpy flux, are fairly independent of depth. In spheroidal geometry this same correlation increases linearly with radius over the inner 70 percent by radius, in which the local pressure scale heights are a sizable fraction of the radius. The effects from the impenetrable boundary conditions in the slab geometry models are confused with the effects from non-local convection. In spheroidal geometry nonlocal effects, due to coherent plumes, are seen as far as several pressure scale heights from the lower boundary and are clearly distinguishable from boundary effects.

Seismic evidence for hydration of the Central American slab: Guatemala through Costa Rica

Science.gov (United States)

Syracuse, E. M.; Thurber, C. H.

2011-12-01

The Central American subduction zone exhibits a wide variability in along-arc slab hydration as indicated by geochemical studies. These studies generally show maximum slab contributions to magma beneath Nicaragua and minimum contributions beneath Costa Rica, while intermediate slab fluid contributions are found beneath El Salvador and Guatemala. Geophysical studies suggest strong slab serpentinization and fluid release beneath Nicaragua, and little serpentinization beneath Costa Rica, but the remainder of the subduction zone is poorly characterized seismically. To obtain an integrated seismic model for the Central American subduction zone, we combine 250,000 local seismic arrivals and 1,000,000 differential arrivals for 6,500 shallow and intermediate-depth earthquakes from the International Seismic Centre, the Central American Seismic Center, and the temporary PASSCAL TUCAN array. Using this dataset, we invert for Vp, Vs, and hypocenters using a variable-mesh double-difference tomography algorithm. By observing low-Vp areas within the normally high-Vp slab, we identify portions of the slab that are likely to contain serpentinized mantle, and thus contribute to higher degrees of melting and higher volatile components observable in arc lavas.

SU-C-213-02: Characterizing 3D Printing in the Fabrication of Variable Density Phantoms

Energy Technology Data Exchange (ETDEWEB)

Madamesila, J; McGeachy, P; Villarreal-Barajas, J; Khan, R [The University of Calgary, Calgary, AB (Canada)

2015-06-15

Purpose: In this work, we present characterization, process flow, quality control and application of 3D fabricated low density phantoms for radiotherapy quality assurance. Methods: A Rostock delta 3D printer using polystyrene filament of diameter 1.75 mm was used to print geometric volumes of 2×2×1 cm{sup 3} of varying densities. The variable densities of 0.1 to 0.75 g/cm {sup 3} were created by modulating the infill. A computed tomography (CT) scan was performed to establish an infill-density calibration curve as well as characterize the quality of the print such as uniformity and the infill pattern. The time required to print these volumes was also recorded. Using the calibration, two low density cones (0.19, 0.52 g/cm{sup 3}) were printed and benchmarked against commercially available phantoms. The dosimetric validation of the low density scaling of Anisotropic Analytical Algorithm (AAA) was performed by using a 0.5 g/cm{sup 3} slab of 10×10×2.4 cm{sup 3} with EBT3 GafChromic film. The gamma analysis at 3%/3mm criteria were compared for the measured and computed dose planes. Results: Analysis of the volume of air pockets in the infill resulted in a reasonable uniformity for densities 0.4 to 0.75 g/cm{sup 3}. Printed phantoms with densities below 0.4 g/cm{sup 3} exhibited a higher ratio of air to polystyrene resulting in large non-uniformity. Compared to the commercial inserts, good agreement was observed only for the printed 0.52 g/cm{sup 3} cone. Dosimetric comparison for a printed low density volume placed in-between layers of solid water resulted in >95% gamma agreement between AAA calculated dose planes and measured EBT3 films for a 6MV 5×5 cm{sup 2} clinical beam. The comparison showed disagreement in the penumbra region. Conclusion: In conclusion, 3D printing technology opens the door to desktop fabrication of variable density phantoms at economical prices in an efficient manner for the quality assurance needs of a small clinic.

Simulation of curing of a slab of rubber

International Nuclear Information System (INIS)

Abhilash, P.M.; Kannan, K.; Varkey, Bijo

2010-01-01

The objective of the present work is to predict the degree of curing for a rectangular slab of rubber, which was subjected to non-uniform thermal history. As the thermal conductivity of rubber is very low, the temperature gradient across a slab is quite large, which leads to non-uniform vulcanization, and hence non-uniform mechanical properties-an inhomogeneous material. Since curing is an exothermic reaction, heat transfer and chemical reactions are solved in a coupled manner. The effect of heat generation on curing is also discussed.

Simulation of curing of a slab of rubber

Energy Technology Data Exchange (ETDEWEB)

Abhilash, P.M. [Department of Mechanical Engineering, IIT Madras, Chennai 600036 (India); Kannan, K., E-mail: krishnakannan@iitm.ac.i [Department of Mechanical Engineering, IIT Madras, Chennai 600036 (India); Varkey, Bijo [Advanced Design Department, MRF Ltd., Chennai 600019 (India)

2010-04-15

The objective of the present work is to predict the degree of curing for a rectangular slab of rubber, which was subjected to non-uniform thermal history. As the thermal conductivity of rubber is very low, the temperature gradient across a slab is quite large, which leads to non-uniform vulcanization, and hence non-uniform mechanical properties-an inhomogeneous material. Since curing is an exothermic reaction, heat transfer and chemical reactions are solved in a coupled manner. The effect of heat generation on curing is also discussed.

An improved Virtual Torso phantom

International Nuclear Information System (INIS)

Kramer, Gary H; Crowley, Paul

2000-01-01

The virtual phantom that was previously designed by the Human Monitoring Laboratory had some limitations. It contained no sternum and the ribs extended all the way round the torso, whereas in reality the central part of the chest is covered with a mixture of cartilage (ribs) and bone (sternum). The ribs were located below the chest wall which added to the thickness of the chest wall. The lungs did not touch the inner surface of the chest wall along their length due to the differences in curvature between the ellipsoidal lungs and the ellipsoidal cylinder that defined the torso. As a result there was extra intervening tissue between the lungs and the chest wall. This was shown to have a noticeable effect on the simulation of low energy photons. The virtual phantom has been redesigned and comparison of measured and calculated counting efficiencies shows that it is a good representation of both of LLNL or JAERI at all photon energies measured. The redesigned virtual phantom agrees to within 11% of the torsos' counting efficiency over the energy range 17 - 240 keV. Before modification, the virtual phantom's counting efficiency was a of factor three lower at 17 keV and a factor of two lower at 20 keV; now it is within 5% at 17 keV and within 10% at 20 keV. This phantom can now be reliably used to simulate lung counting. The virtual phantom still contains no sternum and the ribs extend all the way round the torso, whereas in reality the central part of the chest is covered with cartilage (ribs) and bone (sternum). However, the above results indicate that this is not a major flaw in the design of the virtual phantom, as agreement between the Monte Carlo results and experimental data is good. (author)

Ocular MR imaging. Evaluation of different coil setups in a phantom study

International Nuclear Information System (INIS)

Erb-Eigner, Katharina; Warmuth, Carsten; Taupitz, Matthias; Bertelmann, Eckart; Hamm, Bernd; Asbach, Patrick

2013-01-01

Small loop surface coils are generally recommended for ocular magnetic resonance (MR) imaging, but the optimal coil setup has not been systematically investigated. In this phantom study, we investigated which coil setup of those coils available for our MR imaging system provides the highest signal-to-noise ratio (SNR) in ocular MR imaging at 1.5 tesla. Using a phantom to simulate the eyeball and the orbital fat, we employed loop surface coils of 4- and 6-cm diameter and a multi-channel head coil to obtain images using a T 1 -weighted spin-echo sequence and then measured the SNR for each coil and coil combination. Use of the 6-cm loop coil alone yielded the highest mean SNR (27.5). Even in superficial regions (mesial and temporal), the SNR was higher using the 6-cm loop coil (33.6 and 45.5) than the 4-cm loop coil (28.0 and 33.8). Additional use of the head coil reduced the mean SNR to 10.4. This quantitative analysis suggests that use of a 6-cm loop surface coil offers the best results in ocular MR imaging. Combinations of loop coils or additional use of a head coil cannot be recommended because higher noise degrades image quality. (author)

Juan de Fuca slab geometry and its relation to Wadati-Benioff zone seismicity

Science.gov (United States)

McCrory, Patricia A.; Blair, J. Luke; Waldhause, Felix; Oppenheimer, David H.

2012-01-01

A new model of the subducted Juan de Fuca plate beneath western North America allows first-order correlations between the occurrence of Wadati-Benioff zone earthquakes and slab geometry, temperature, and hydration state. The geo-referenced 3D model, constructed from weighted control points, integrates depth information from earthquake locations and regional seismic velocity studies. We use the model to separate earthquakes that occur in the Cascadia forearc from those that occur within the underlying Juan de Fuca plate and thereby reveal previously obscured details regarding the spatial distribution of earthquakes. Seismicity within the slab is most prevalent where the slab is warped beneath northwestern California and western Washington suggesting that slab flexure, in addition to expected metamorphic dehydration processes, promotes earthquake occurrence within the subducted oceanic plate. Earthquake patterns beneath western Vancouver Island are consistent with slab dehydration processes. Conversely, the lack of slab earthquakes beneath western Oregon is consistent with an anhydrous slab. Double-differenced relocated seismicity resolves a double seismic zone within the slab beneath northwestern California that strongly constrains the location of the plate interface and delineates a cluster of seismicity 10 km above the surface that includes the 1992 M7.1 Mendocino earthquake. We infer that this earthquake ruptured a surface within the Cascadia accretionary margin above the Juan de Fuca plate. We further speculate that this earthquake is associated with a detached fragment of former Farallon plate. Other subsurface tectonic elements within the forearc may have the potential to generate similar damaging earthquakes.

Unusually deep Bonin earthquake of 30 May 2015: A precursory signal to slab penetration?

Science.gov (United States)

Obayashi, Masayuki; Fukao, Yoshio; Yoshimitsu, Junko

2017-02-01

An M7.9 earthquake occurred on 30 May 2015 at an unusual depth of 680 km downward and away from the well-defined Wadati-Benioff (WB) zone of the southern Bonin arc. To the north (northern Bonin), the subducted slab is stagnant above the upper-lower mantle boundary at 660-km depth, where the WB zone bends forward to sub-horizontal. To the south (northern Mariana), it penetrates the boundary, where the WB zone extends near-vertically down to the boundary. Thus, the southern Bonin slab can be regarded as being in a transitional state from slab stagnation to penetration. The transition is shown to happen rapidly within the northern half of the southern Bonin slab where the heel part of the shoe-like configured stagnant slab hits the significantly depressed 660-km discontinuity. The mainshock and aftershocks took place in this heel part where they are sub-vertically aligned in approximate parallel to their maximum compressional axes. Here, the dips of the compressional axes of WB zone earthquakes change rapidly across the thickness of the slab from the eastern to western side and along the strike of the slab from the northern to southern side, suggesting rapid switching of the downdip compression axis in the shoe-shaped slab. Elastic deformation associated with the WB zone seismicity is calculated by viewing it as an integral part of the slab deformation process. With this deformation, the heel part is deepened relative to the arch part and is compressed sub-vertically and stretched sub-horizontally, a tendency consistent with the idea of progressive decent of the heel part in which near-vertical compressional stress is progressively accumulated to generate isolated shocks like the 2015 event and eventually to initiate slab penetration.

Development of a Leave-in-Place Slab Edge Insulating Form System

Energy Technology Data Exchange (ETDEWEB)

Marc Hoeschele; Eric Lee

2009-08-31

Concrete slabs represent the primary foundation type in residential buildings in the fast-growing markets throughout the southern and southwestern United States. Nearly 75% of the 2005 U.S. population growth occurred in these southern tier states. Virtually all of these homes have uninsulated slab perimeters that transfer a small, but steady, flow of heat from conditioned space to outdoors during the heating season. It is estimated that new home foundations constructed each year add 0.016 quads annually to U.S. national energy consumption; we project that roughly one quarter of this amount can be attributed to heat loss through the slab edge and the remaining three quarters to deep ground transfers, depending upon climate. With rising concern over national energy use and the impact of greenhouse gas emissions, it is becoming increasingly imperative that all cost-effective efforts to improve building energy efficiency be implemented. Unlike other building envelope components that have experienced efficiency improvements over the years, slab edge heat loss has largely been overlooked. From our vantage point, a marketable slab edge insulation system would offer significant benefits to homeowners, builders, and the society as a whole. Conventional slab forming involves the process of digging foundation trenches and setting forms prior to the concrete pour. Conventional wood form boards (usually 2 x 10's) are supported by vertical stakes on the outer form board surface, and by supporting 'kickers' driven diagonally from the top of the form board into soil outside the trench. Typically, 2 x 10's can be used only twice before they become waste material, contributing to an additional 400 pounds of construction waste per house. Removal of the form boards and stakes also requires a follow-up trip to the jobsite by the concrete subcontractor and handling (storage/disposal) of the used boards. In the rare cases where the slab is insulated (typically custom

Prediction of punching shear capacities of two-way concrete slabs reinforced with FRP bars

Directory of Open Access Journals (Sweden)

Ibrahim M. Metwally

2013-08-01

Full Text Available Where corrosion of steel reinforcement is a concern, fiber-reinforced polymer (FRP reinforcing bar or grid reinforcement provides an alternative reinforcement for concrete flat slabs. The existing provisions for punching of slabs in most international design standards for reinforced concrete are based on tests of steel reinforced slabs. The elastic stiffness and bonding characteristics of FRP reinforcement are sufficiently different from those of steel to affect punching strength [1]. This paper evaluates the punching shear strength of concrete flat slabs reinforced with different types of fiber-reinforced polymer (FRP. A total of 59 full-size slabs were constructed and tested collected from the literature of FRP bars reinforced concrete slabs. The test parameters were the amount of FRP reinforcing bars, Young’s modulus of FRP bars, slab thickness, loaded areas and concrete compressive strength. The experimental punching shear strengths were compared with the available theoretical predictions, including the ACI 318 Code, BS 8110 Code, ACI 440 design guidelines, and a number of models proposed by some researchers in the literature. Two approaches for predicting the punching strength of FRP-reinforced slabs are examined. The first is an empirical new model which is considered as a modification of El-Gamal et al. [2] model. The second is a Neural Networks Technique; which has been developed to predict the punching shear capacity of FRP reinforced concrete slabs. The accuracies of both methods were evaluated against the experimental test data. They attained excellent agreement with available test results compared to the existing design formulas.

Phantom measurements and computed estimates of breast dose with radiotherapy for Hodgkin's lymphoma: dose reduction with the use of the involved field

International Nuclear Information System (INIS)

Wirth, A.; Kron, T.; Sorell, G.; Cramb, J.; Wittwer, H.; Sullivan, K.

2008-01-01

Full text: The risk of breast cancer following radiotherapy for Hodgkin's lymphoma appears to be dose related. In this study we compared breast dose in an anthropomorphic phantom for conventional 'mantle'; upper mediastinal/bilateral neck (minimantle) and unilateral neck fields, and evaluated the accuracy of computer planned dose estimates for out-of-field doses. For each field, computer-planned breast dose (CPD) estimates were compared with thermolu-minescence dosimetry measurements in five locations within 'breast tissue'. CPD were also compared with ion chamber measurements in a slab phantom. Measured dose and CPD were within 20% of each other up to approximately 10 cm from the field edge. Beyond 10 cm, the CPD underestimated dose by a factor of 2 or more. The minimantle reduced the breast dose by a factor of approximately 10 compared with the mantle treatment. Treating the neck field lowered the breast dose by a further 50% or more. Modern involved-field radiotherapy for lymphoma substantially reduces breast dose compared with mantle fields. Computer dosimetery underestimated dose at larger distances from the field. This needs to be considered if computer dosimetery is used to estimate breast dose and, by extrapolation, breast cancer risk.

Comparison of methods for individualized astronaut organ dosimetry: Morphometry-based phantom library versus body contour autoscaling of a reference phantom

Science.gov (United States)

Sands, Michelle M.; Borrego, David; Maynard, Matthew R.; Bahadori, Amir A.; Bolch, Wesley E.

2017-11-01

One of the hazards faced by space crew members in low-Earth orbit or in deep space is exposure to ionizing radiation. It has been shown previously that while differences in organ-specific and whole-body risk estimates due to body size variations are small for highly-penetrating galactic cosmic rays, large differences in these quantities can result from exposure to shorter-range trapped proton or solar particle event radiations. For this reason, it is desirable to use morphometrically accurate computational phantoms representing each astronaut for a risk analysis, especially in the case of a solar particle event. An algorithm was developed to automatically sculpt and scale the UF adult male and adult female hybrid reference phantom to the individual outer body contour of a given astronaut. This process begins with the creation of a laser-measured polygon mesh model of the astronaut's body contour. Using the auto-scaling program and selecting several anatomical landmarks, the UF adult male or female phantom is adjusted to match the laser-measured outer body contour of the astronaut. A dosimetry comparison study was conducted to compare the organ dose accuracy of both the autoscaled phantom and that based upon a height-weight matched phantom from the UF/NCI Computational Phantom Library. Monte Carlo methods were used to simulate the environment of the August 1972 and February 1956 solar particle events. Using a series of individual-specific voxel phantoms as a local benchmark standard, autoscaled phantom organ dose estimates were shown to provide a 1% and 10% improvement in organ dose accuracy for a population of females and males, respectively, as compared to organ doses derived from height-weight matched phantoms from the UF/NCI Computational Phantom Library. In addition, this slight improvement in organ dose accuracy from the autoscaled phantoms is accompanied by reduced computer storage requirements and a more rapid method for individualized phantom generation

Initial quality performance results using a phantom to simulate chest computed radiography

Directory of Open Access Journals (Sweden)

Muhogora Wilbroad

2011-01-01

Full Text Available The aim of this study was to develop a homemade phantom for quantitative quality control in chest computed radiography (CR. The phantom was constructed from copper, aluminium, and polymenthylmethacrylate (PMMA plates as well as Styrofoam materials. Depending on combinations, the literature suggests that these materials can simulate the attenuation and scattering characteristics of lung, heart, and mediastinum. The lung, heart, and mediastinum regions were simulated by 10 mm x 10 mm x 0.5 mm, 10 mm x 10 mm x 0.5 mm and 10 mm x 10 mm x 1 mm copper plates, respectively. A test object of 100 mm x 100 mm and 0.2 mm thick copper was positioned to each region for CNR measurements. The phantom was exposed to x-rays generated by different tube potentials that covered settings in clinical use: 110-120 kVp (HVL=4.26-4.66 mm Al at a source image distance (SID of 180 cm. An approach similar to the recommended method in digital mammography was applied to determine the CNR values of phantom images produced by a Kodak CR 850A system with post-processing turned off. Subjective contrast-detail studies were also carried out by using images of Leeds TOR CDR test object acquired under similar exposure conditions as during CNR measurements. For clinical kVp conditions relevant to chest radiography, the CNR was highest over 90-100 kVp range. The CNR data correlated with the results of contrast detail observations. The values of clinical tube potentials at which CNR is the highest are regarded to be optimal kVp settings. The simplicity in phantom construction can offer easy implementation of related quality control program.

Studi Komparasi Antara Pracetak Masif Dan Fly Slab Studi Kasus : Struktur Gedung Rusunawa Surakarta

OpenAIRE

Wirawan, Aria; Wicaksono, Budi; Nuroji, Nuroji; Partono, Windu

2013-01-01

Fly slab is one of the precast concrete slab technological development that has been researched and patented by Ir . Sulistyana in 2011. The concept is how to reduce the mass of precast concrete slab with makes ribs on the concrete slab. To minimize the volume of concrete plate and while maintaining tensile area to makes the style transfer mechanism of concrete to reinforcement or otherwise, are expected to reduce the mass of the structure without reducing strength.Comparative study will be c...

Transport of radon through cracks in a concrete slab

Energy Technology Data Exchange (ETDEWEB)

Landman, K A; Cohen, D S

1983-03-01

A model involving the use of line sources is developed to describe the transport of radon through the cracks or gaps which appear in concrete slabs used in building foundations. The strength of these sources is determined from the results of the diffusion model proposed by Landman in a previous work. Once the strength of the source is known, additional transport mechanisms can be treated in a simple manner. Pressure differences across the slab and in the underlying soil are discussed. The rate of exhalation through a portion of the cracked slab is determined and compared to the rate of exhalation from the same surface area of bare soil. In typical cases, their ratios vary from 0.25 to 0.50. Therefore, these transport mechanisms account for a larger portion of the levels of radon found in many houses than do previous models.

First wall fusion blanket temperature variation - slab geometry

International Nuclear Information System (INIS)

Fillo, J.A.

1978-01-01

The first wall of a fusion blanket is approximated by a slab, with the surface facing the plasma subjected to an applied heat flux, while the rear surface is convectively cooled. The relevant parameters affecting the heat transfer during the early phases of heating as well as for large times are established. Analytical solutions for the temperature variation with time and space are derived. Numerical calculations for an aluminum and stainless steel slab are performed for a wall loading of 1 MW(th)/m 2 . Both helium and water cooling are considered. (Auth.)

Verification of a table of phantom scatter factors for radiotherapy treatment planning

International Nuclear Information System (INIS)

Arts, J.K.; Bailey, M.J.; Hill, R.

2004-01-01

referenced from the XiO training guide manual. Comparison of the phantom scatter factors results show agreement within ± 1.2% for the Primus machine for both 6MV and 18MV X-rays. For the KD Mevatron linear accelerator, the 18MV data matched within 1.3% except at the 4x4cm field size. For the 6MV X-rays, the match was and within ± 2.5% for the KD and MX machines at the largest field sizes. The results of these comparisons indicate that the table of phantom scatter factors as described by Storchi et al is a useful QA tool for checking of beam data. These results suggest that it would not be recommended to rely upon the published data alone when calculating phantom scatter factors for treatment planning in radiotherapy. Copyright (2004) Australasian College of Physical Scientists and Engineers in Medicine

Slab melting and magma formation beneath the southern Cascade arc

Science.gov (United States)

Walowski, Kristina J.; Wallace, Paul J.; Clynne, Michael A.; Rasmussen, D.J.; Weis, D.

2016-01-01

The processes that drive magma formation beneath the Cascade arc and other warm-slab subduction zones have been debated because young oceanic crust is predicted to largely dehydrate beneath the forearc during subduction. In addition, geochemical variability along strike in the Cascades has led to contrasting interpretations about the role of volatiles in magma generation. Here, we focus on the Lassen segment of the Cascade arc, where previous work has demonstrated across-arc geochemical variations related to subduction enrichment, and H-isotope data suggest that H2O in basaltic magmas is derived from the final breakdown of chlorite in the mantle portion of the slab. We use naturally glassy, olivine-hosted melt inclusions (MI) from the tephra deposits of eight primitive (MgO>7 wt%) basaltic cinder cones to quantify the pre-eruptive volatile contents of mantle-derived melts in this region. The melt inclusions have B concentrations and isotope ratios that are similar to mid-ocean ridge basalt (MORB), suggesting extensive dehydration of the downgoing plate prior to reaching sub-arc depths and little input of slab-derived B into the mantle wedge. However, correlations of volatile and trace element ratios (H2O/Ce, Cl/Nb, Sr/Nd) in the melt inclusions demonstrate that geochemical variability is the result of variable addition of a hydrous subduction component to the mantle wedge. Furthermore, correlations between subduction component tracers and radiogenic isotope ratios show that the subduction component has less radiogenic Sr and Pb than the Lassen sub-arc mantle, which can be explained by melting of subducted Gorda MORB beneath the arc. Agreement between pMELTS melting models and melt inclusion volatile, major, and trace element data suggests that hydrous slab melt addition to the mantle wedge can produce the range in primitive compositions erupted in the Lassen region. Our results provide further evidence that chlorite-derived fluids from the mantle portion of the

Composition of MRI phantom equivalent to human tissues

International Nuclear Information System (INIS)

Kato, Hirokazu; Kuroda, Masahiro; Yoshimura, Koichi; Yoshida, Atsushi; Hanamoto, Katsumi; Kawasaki, Shoji; Shibuya, Koichi; Kanazawa, Susumu

2005-01-01

We previously developed two new MRI phantoms (called the CAG phantom and the CAGN phantom), with T1 and T2 relaxation times equivalent to those of any human tissue at 1.5 T. The conductivity of the CAGN phantom is equivalent to that of most types of human tissue in the frequency range of 1 to 130 MHz. In this paper, the relaxation times of human tissues are summarized, and the composition of the corresponding phantoms are provided in table form. The ingredients of these phantoms are carrageenan as the gelling agent, GdCl 3 as a T1 modifier, agarose as a T2 modifier, NaCl (CAGN phantom only) as a conductivity modifier, NaN 3 as an antiseptic, and distilled water. The phantoms have T1 values of 202-1904 ms and T2 values of 38-423 ms when the concentrations of GdCl 3 and agarose are varied from 0-140 μmol/kg, and 0%-1.6%, respectively, and the CAGN phantom has a conductivity of 0.27-1.26 S/m when the NaCl concentration is varied from 0%-0.7%. These phantoms have sufficient strength to replicate a torso without the use of reinforcing agents, and can be cut by a knife into any shape. We anticipate the CAGN phantom to be highly useful and practical for MRI and hyperthermia-related research

Double seismic zone in downgoing slabs and the viscosity of the mesosphere

International Nuclear Information System (INIS)

Sleep, N.H.

1979-01-01

The seismic zone beneath several island arcs between about 100 and 200 km depth consists of an upper zone having down-dip compression and a lower zone having down-dip tension. Several numerical models of the Aleutina arc were computed to test the hypothesis that these double seismic zones are due to sagging of the slab under its own weight. This sagging occurs because the asthenosphere (between about 100 and 200 km) provides little support or resistance to the slab, which is supported from below by the more viscous mesosphere and from above by the lithosphere. The viscosity of the mesosphere was constrained to the interval between 0.25 x 10 22 and 0.5 x 10 22 P by noting that the slab would have mainly down-dip compression at higher viscosities and mainly down-dip tension at lower viscosities. The deviatoric stress in the slab and the fault plane between the slab and the island arc is about 200--300 bars (expressed as shear stress). The models were calibrated to the observed depth and gravity anomalies in the trench

Impact of patient weight on tumor visibility based on human-shaped phantom simulation study in PET imaging system

International Nuclear Information System (INIS)

Musarudin, M.; Saripan, M.I.; Mashohor, S.; Saad, W.H.M.; Nordin, A.J.; Hashim, S.

2015-01-01

Energy window technique has been implemented in all positron emission tomography (PET) imaging protocol, with the aim to remove the unwanted low energy photons. Current practices in our institution however are performed by using default energy threshold level regardless of the weight of the patient. Phantom size, which represents the size of the patient's body, is the factor that determined the level of scatter fraction during PET imaging. Thus, the motivation of this study is to determine the optimum energy threshold level for different sizes of human-shaped phantom, to represent underweight, normal, overweight and obese patients. In this study, the scanner was modeled by using Monte Carlo code, version MCNP5. Five different sizes of elliptical-cylinder shaped of human-sized phantoms with diameter ranged from 15 to 30 cm were modeled. The tumor was modeled by a cylindrical line source filled with 1.02 MeV positron emitters at the center of the phantom. Various energy window widths, in the ranged of 10–50% were implemented to the data. In conclusion, the phantom mass volume did influence the scatter fraction within the volume. Bigger phantom caused more scattering events and thus led to coincidence counts lost. We evaluated the impact of phantom sizes on the sensitivity and visibility of the simulated models. Implementation of wider energy window improved the sensitivity of the system and retained the coincidence photons lost. Visibility of the tumor improved as an appropriate energy window implemented for the different sizes of phantom. - Highlights: • Optimizing the energy window improved the sensitivity of the PET system. • Improving the visibility of the tumors using the optimized energy window. • Recommendations on the optimized energy windows for different body sizes. • Using simulated phantom using MCNP to determine various body sizes

Influence of transverse reinforcement on perforation resistance of reinforced concrete slabs under hard missile impact

International Nuclear Information System (INIS)

Orbovic, Nebojsa; Sagals, Genadijs; Blahoianu, Andrei

2015-01-01

This paper describes the work conducted by the Canadian Nuclear Safety Commission (CNSC) related to the influence of transverse reinforcement on perforation capacity of reinforced concrete (RC) slabs under “hard” missile impact (impact with negligible missile deformations). The paper presents the results of three tests on reinforced concrete slabs conducted at VTT Technical Research Centre (Finland), along with the numerical simulations as well as a discussion of the current code provisions related to impactive loading. Transverse reinforcement is widely used for improving the shear and punching strength of concrete structures. However, the effect of this reinforcement on the perforation resistance under localized missile impact is still unclear. The goal of this paper is to fill the gap in the current literature related to this topic. Based on similar tests designed by the authors with missile velocity below perforation velocity, it was expected that transverse reinforcement would improve the perforation resistance. Three slabs were tested under almost identical conditions with the only difference being the transverse reinforcement. One slab was designed without transverse reinforcement, the second one with the transverse reinforcement in form of conventional stirrups with hooks and the third one with the transverse reinforcement in form of T-headed bars. Although the transverse reinforcement reduced the overall damage of the slabs (the rear face scabbing), the conclusion from the tests is that the transverse reinforcement does not have important influence on perforation capacity of concrete slabs under rigid missile impact. The slab with T-headed bars presented a slight improvement compared to the baseline specimen without transverse reinforcement. The slab with conventional stirrups presented slightly lower perforation capacity (higher residual missile velocity) than the slab without transverse reinforcement. In conclusion, the performed tests show slightly

Calculation of spin and orbital magnetizations in Fe slab systems at finite temperature

Energy Technology Data Exchange (ETDEWEB)

Garibay-Alonso, R [Facultad de Ciencias FIsico Matematicas, Universidad Autonoma de Coahuila, Conjunto Universitario Camporredondo, Edificio ' D' , 25000 Saltillo (Mexico); Reyes-Reyes, M [Instituto de Investigacion en Comunicacion Optica, Universidad Autonoma de San Luis PotosI, Alvaro Obregon 64, San Luis PotosI (Mexico); Urrutia-Banuelos, EfraIn [Departamento de Investigacion en Fisica, Universidad de Sonora, Apartado Postal 5-088, Hermosillo, Sonora 83190 (Mexico); Lopez-Sandoval, R [Instituto Potosino de Investigacion CientIfica y Tecnologica, Camino a la presa San Jose 2055, CP 78216, San Luis PotosI (Mexico)

2010-02-10

The temperature dependence of spin and orbital local magnetizations is theoretically determined for the non-bulk atomic region of (001) and (110) Fe slab systems. A d band Hamiltonian, including spin-orbit coupling terms, was used to model the slabs, which were emulated by using Fe films of sufficient thickness to reach a bulk behavior at their most inner atomic layers. The temperature effects were considered within the static approximation and a simple mean field theory was used to integrate the local magnetic moment and charge thermal fluctuations. The results reflect a clear interplay between electronic itinerancy and the local atomic environment and they can be physically interpreted from the local small charge transfers occurring in the superficial region of the slabs. For recovering the experimental behavior on the results for the (001) slab system, the geometrical relaxations at its non-bulk atomic layers and a d band filling variation are required. A study on the magnetic anisotropy aspects in the superficial region of the slabs is additionally performed by analyzing the results for the orbital local magnetization calculated along two different magnetization directions in both slab systems.

Interim report of the JHPS expert committee on radiation protection of the lens of the eye (4). Current activities of ICRP and ICU: External dosimetric concepts for the lens of the eye

International Nuclear Information System (INIS)

Akahane, Keiichi; Tatsuzaki, Hideo; Iimoto, Takeshi; Ichiji, Takeshi; Hamada, Nobuyuki; Fujimichi, Yuki; Iwai, Satoshi; Ohguchi, Hiroyuki; Ohno, Kazuko; Yamauchi-Kawaura, Chiyo; Tsujimura, Norio; Hotta, Yutaka; Yamasaki, Tadashi; Yokoyama, Sumi

2015-01-01

The International Commission on Radiological Protection (ICRP) and the International Commission on Radiation Units and Measurements (ICRU) have been defined operational quantities and protection quantities. Dose limits have been also recommended by the ICRP using protection quantities. These quantities and some related values for main radiation such as photons, electrons, and neutrons, are summarized in this article with some historical considerations. The ICRP indicated conversion coefficients for the lens of the eye as absorbed dose per fluence as protection quantities. equivalent dose is not used because a protection quantity that uses radiation weighting factors is not intended to be calculated for tissue reactions. So far, the ICRP has not indicated a specific RBE value for cataract formation. Operational quantities are used for measurements. There have been three types of phantoms, namely a slab phantom, a reduced phantom, and a cylindrical phantom, but none of them has been definitely recommended for the lens of the eye by the ICRP or the ICRU. Although conversion coefficients to personal dose equivalent, H p (3), for electrons have been recommended, no other conversion coefficients to personal dose equivalent for the lens of the eye has been indicated by the ICRP or the ICRU. However, there have been several studies described personal dose equivalent. Ambient dose equivalent, H * (3), and directional dose equivalent, H(3, α), have been indicated in several limited conditions by the ICRP and the ICRU. These status are overviewed in this article. (author)

Characterization of the phantom material virtual water in high-energy photon and electron beams.

Science.gov (United States)

McEwen, M R; Niven, D

2006-04-01

The material Virtual Water has been characterized in photon and electron beams. Range-scaling factors and fluence correction factors were obtained, the latter with an uncertainty of around 0.2%. This level of uncertainty means that it may be possible to perform dosimetry in a solid phantom with an accuracy approaching that of measurements in water. Two formulations of Virtual Water were investigated with nominally the same elemental composition but differing densities. For photon beams neither formulation showed exact water equivalence-the water/Virtual Water dose ratio varied with the depth of measurement with a difference of over 1% at 10 cm depth. However, by using a density (range) scaling factor very good agreement (water and Virtual Water at all depths was obtained. In the case of electron beams a range-scaling factor was also required to match the shapes of the depth dose curves in water and Virtual Water. However, there remained a difference in the measured fluence in the two phantoms after this scaling factor had been applied. For measurements around the peak of the depth-dose curve and the reference depth this difference showed some small energy dependence but was in the range 0.1%-0.4%. Perturbation measurements have indicated that small slabs of material upstream of a detector have a small (<0.1% effect) on the chamber reading but material behind the detector can have a larger effect. This has consequences for the design of experiments and in the comparison of measurements and Monte Carlo-derived values.

Seismic Behaviour of Masonry Vault-Slab Structures

International Nuclear Information System (INIS)

Chesi, Claudio; Butti, Ferdinando; Ferrari, Marco

2008-01-01

Spandrel walls typically play a structural role in masonry buildings, transferring load from a slab to the supporting vault. Some indications are given in the literature on the behaviour of spandrels under the effect of vertical loads, but little attention is given to the effect coming from lateral forces acting on the building. An opportunity to investigate this problem has come from the need of analyzing a monumental building which was damaged by the Nov. 24, 2004 Val Sabbia earthquake in the north of Italy. The finite element model set up for the analysis of the vault-spandrel-slab system is presented and the structural role resulting for the spandrels is discussed

Transcutaneous electrical nerve stimulation (TENS) for phantom pain and stump pain following amputation in adults.

Science.gov (United States)

Johnson, Mark I; Mulvey, Matthew R; Bagnall, Anne-Marie

2015-08-18

This is the first update of a Cochrane review published in Issue 5, 2010 on transcutaneous electrical nerve stimulation (TENS) for phantom pain and stump pain following amputation in adults. Pain may present in a body part that has been amputated (phantom pain) or at the site of amputation (stump pain), or both. Phantom pain and stump pain are complex and multidimensional and the underlying pathophysiology remains unclear. The condition remains a severe burden for those who are affected by it. The mainstay treatments are predominately pharmacological, with increasing acknowledgement of the need for non-drug interventions. TENS has been recommended as a treatment option but there has been no systematic review of available evidence. Hence, the effectiveness of TENS for phantom pain and stump pain is currently unknown. To assess the analgesic effectiveness of TENS for the treatment of phantom pain and stump pain following amputation in adults. For the original version of the review we searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, PsycINFO, AMED, CINAHL, PEDRO and SPORTDiscus (February 2010). For this update, we searched the same databases for relevant randomised controlled trials (RCTs) from 2010 to 25 March 2015. We only included RCTs investigating the use of TENS for the management of phantom pain and stump pain following an amputation in adults. Two review authors independently assessed trial quality and extracted data. We planned that where available and appropriate, data from outcome measures were to be pooled and presented as an overall estimate of the effectiveness of TENS. In the original review there were no RCTs that examined the effectiveness of TENS for the treatment of phantom pain and stump pain in adults. For this update, we did not identify any additional RCTs for inclusion. There were no RCTs to judge the effectiveness of TENS for the management of phantom pain and stump pain. The published literature on TENS

Experimental research of slab cast over precast joists with prestressed reinforcement

Directory of Open Access Journals (Sweden)

Koyankin Aleksandr Aleksandrovich

2016-03-01

Full Text Available At the present time reinforced concrete is the main construction material in civil and industrial construction. Cast-in-place and precast construction is gradually becoming a more widespread type of house-building, but still there is a lack of data, including experimental data, which allows evaluating the stress and strain state of a construction of a slab cast over precast joists. Experimental research of stress and strain state of slab cast over precast joists with prestressed reinforcement was carried out. An experimental model of a fragment of a hybrid precast/cast-in-place building was produced and tested (reduction scale 1:6. The experimental investigations of slab cast over precast joists with prestressed reinforcement proved that the construction solution of the framework offered in the previous works of the authors possess good stiffness, crack-resistance and bearing capacity. It well fits for constructing the slabs of long spans in residential and public buildings.

Phantom motor execution facilitated by machine learning and augmented reality as treatment for phantom limb pain: a single group, clinical trial in patients with chronic intractable phantom limb pain.

Science.gov (United States)

Ortiz-Catalan, Max; Guðmundsdóttir, Rannveig A; Kristoffersen, Morten B; Zepeda-Echavarria, Alejandra; Caine-Winterberger, Kerstin; Kulbacka-Ortiz, Katarzyna; Widehammar, Cathrine; Eriksson, Karin; Stockselius, Anita; Ragnö, Christina; Pihlar, Zdenka; Burger, Helena; Hermansson, Liselotte

2016-12-10

Phantom limb pain is a debilitating condition for which no effective treatment has been found. We hypothesised that re-engagement of central and peripheral circuitry involved in motor execution could reduce phantom limb pain via competitive plasticity and reversal of cortical reorganisation. Patients with upper limb amputation and known chronic intractable phantom limb pain were recruited at three clinics in Sweden and one in Slovenia. Patients received 12 sessions of phantom motor execution using machine learning, augmented and virtual reality, and serious gaming. Changes in intensity, frequency, duration, quality, and intrusion of phantom limb pain were assessed by the use of the numeric rating scale, the pain rating index, the weighted pain distribution scale, and a study-specific frequency scale before each session and at follow-up interviews 1, 3, and 6 months after the last session. Changes in medication and prostheses were also monitored. Results are reported using descriptive statistics and analysed by non-parametric tests. The trial is registered at ClinicalTrials.gov, number NCT02281539. Between Sept 15, 2014, and April 10, 2015, 14 patients with intractable chronic phantom limb pain, for whom conventional treatments failed, were enrolled. After 12 sessions, patients showed statistically and clinically significant improvements in all metrics of phantom limb pain. Phantom limb pain decreased from pre-treatment to the last treatment session by 47% (SD 39; absolute mean change 1·0 [0·8]; p=0·001) for weighted pain distribution, 32% (38; absolute mean change 1·6 [1·8]; p=0·007) for the numeric rating scale, and 51% (33; absolute mean change 9·6 [8·1]; p=0·0001) for the pain rating index. The numeric rating scale score for intrusion of phantom limb pain in activities of daily living and sleep was reduced by 43% (SD 37; absolute mean change 2·4 [2·3]; p=0·004) and 61% (39; absolute mean change 2·3 [1·8]; p=0·001), respectively. Two of four

Toxicology Analysis of Tissue-Mimicking Phantom Made From Gelatin

Science.gov (United States)

Dolbashid, A. S.; Hamzah, N.; Zaman, W. S. W. K.; Mokhtar, M. S.

2017-06-01

Skin phantom mimics the biological skin tissues as it have the ability to respond to changes in its environment. The development of tissue-mimicking phantom could contributes towards the reduce usage of animal in cosmetics and pharmacokinetics. In this study, the skin phantoms made from gelatin were tested with four different commonly available cosmetic products to determine the toxicity of each substance. The four substances used were; mercury-based whitening face cream, carcinogenic liquid make-up foundation, paraben-based acne cleanser, and organic lip balm. Toxicity test were performed on all of the phantoms. For toxicity testing, topographical and electrophysiological changes of the phantoms were evaluated. The ability of each respective phantom to react with mild toxic substances and its electrical resistance were analysed in to determine the toxicity of all the phantom models. Four-electrode method along with custom made electrical impedance analyser was used to differentiate electrical resistance between intoxicated phantom and non-intoxicated phantom in this study. Electrical resistance values obtained from the phantom models were significantly higher than the control group. The result obtained suggests the phantom as a promising candidate to be used as alternative for toxicology testing in the future.

A Software Phantom : Application in Digital Tomosynthesis

Energy Technology Data Exchange (ETDEWEB)

Lazos, D; Kolitsi, Z; Badea, C; Pallikarakis, N [Medical Physics Laboratory, School of Medicine, Univercity of Patras (Greece)

1999-12-31

A software phantom intended to be used in radiographic applications has been developed. The application was used for research in the field of Digital Tomosynthesis and specifically for studying tomographic noise removal methods. The application consists of a phantom design and a phantom imaging module. The radiation-matter interaction is based on the exponential relation of attenuation. Projections are formed by simulated irradiation with selectable geometrical parameters, source spectrum and detector response. Phantoms are defined either as sets containing certain geometrical objects or as groups of voxels. Comparison with real projections taken from a physical phantom with identical geometry and composition with the simulated one, showed good approximation with improved contrast due to the absence of scatter in the simulated projections. The software phantom proved to be a very useful tool for DTS investigations. Further development to include scatter is expected to expand the use of the application to more areas in radiological imaging research. (author) 4 refs., 3 figs

A Software Phantom : Application in Digital Tomosynthesis

International Nuclear Information System (INIS)

Lazos, D.; Kolitsi, Z.; Badea, C.; Pallikarakis, N.

1998-01-01

A software phantom intended to be used in radiographic applications has been developed. The application was used for research in the field of Digital Tomosynthesis and specifically for studying tomographic noise removal methods. The application consists of a phantom design and a phantom imaging module. The radiation-matter interaction is based on the exponential relation of attenuation. Projections are formed by simulated irradiation with selectable geometrical parameters, source spectrum and detector response. Phantoms are defined either as sets containing certain geometrical objects or as groups of voxels. Comparison with real projections taken from a physical phantom with identical geometry and composition with the simulated one, showed good approximation with improved contrast due to the absence of scatter in the simulated projections. The software phantom proved to be a very useful tool for DTS investigations. Further development to include scatter is expected to expand the use of the application to more areas in radiological imaging research. (author)

Conjecture with water and rheological control for subducting slab in the mantle transition zone

Directory of Open Access Journals (Sweden)

Fumiko Tajima

2015-01-01

Full Text Available Seismic observations have shown structural variation near the base of the mantle transition zone (MTZ where subducted cold slabs, as visualized with high seismic speed anomalies (HSSAs, flatten to form stagnant slabs or sink further into the lower mantle. The different slab behaviors were also accompanied by variation of the “660 km” discontinuity depths and low viscosity layers (LVLs beneath the MTZ that are suggested by geoid inversion studies. We address that deep water transport by subducted slabs and dehydration from hydrous slabs could affect the physical properties of mantle minerals and govern slab dynamics. A systematic series of three-dimensional numerical simulation has been conducted to examine the effects of viscosity reduction or contrast between slab materials on slab behaviors near the base of the MTZ. We found that the viscosity reduction of subducted crustal material leads to a separation of crustal material from the slab main body and its transient stagnation in the MTZ. The once trapped crustal materials in the MTZ eventually sink into the lower mantle within 20–30 My from the start of the plate subduction. The results suggest crustal material recycle in the whole mantle that is consistent with evidence from mantle geochemistry as opposed to a two-layer mantle convection model. Because of the smaller capacity of water content in lower mantle minerals than in MTZ minerals, dehydration should occur at the phase transformation depth, ∼660 km. The variation of the discontinuity depths and highly localized low seismic speed anomaly (LSSA zones observed from seismic P waveforms in a relatively high frequency band (∼1 Hz support the hypothesis of dehydration from hydrous slabs at the phase boundary. The LSSAs which correspond to dehydration induced fluids are likely to be very local, given very small hydrogen (H+ diffusivity associated with subducted slabs. The image of such local LSSA zones embedded in HSSAs may not

Performance and damages of R.C. slabs in fire

DEFF Research Database (Denmark)

Giuliani, Luisa; Gentili, Filippo

2015-01-01

Contrary to a common misconception, concrete structures are particularly vulnerable to fire, as witnesses by several cases of fire-induced collapses of buildings with a primary concrete structural system. Even when no collapse occurs, concrete elements are permanently damaged by the fire and may...... on the vulnerability of the slab to the fire action and can be used for optimizing the design on the basis of the required class of resistance or for choosing between different slab alternatives....

Ultrasonographic Quantification of Fat Content in Fatty Liver Phantoms

International Nuclear Information System (INIS)

Kim, Il Young; Kim, Pyo Nyun; Joo, Gyung Soo; Kim, Ho Jung; Kim, Young Beom; Lee, Byoung Ho

1995-01-01

Assuming that the fat content of certain tissue might be quantified by measurirrg the ultrasound echo level, we analyzed the ultrasound histograms obtained from the fatty liver phantoms that contained various amount of fat. Various amount of margarine(Mazola. Cliff wood. USA) was mixed with 2% of agarin solution state to produce fatty liver phantoms that contained 5, 10, 20, 30 and 40% of fat. We obtained ultrasound histogram from each fatty liver phantom in gel state. We used 2% agar gel as a control. The ultrasound histograms from the control phantom showed gradual increase in echo level as the depth from the surface increased. The echo level from the phantom that contained 5% of fat showed gradual increase and subsequent decrease with the peak echo level at the depth of 3cm. The echo levels from the phantoms that contained more in 5% of fat gradually decreased as the depth from the surface increased; the change becoming more pronounced as the fat content of the phantom increased. The echo levels measured at the depth of 1cm were 9.3(control), 29.6(5%phantom), 3l.3 (10% phantom), 26.3 (20% phantom), l8.8 (30% phantom), and l6dB (40% phantom). Fat content of fatty phantoms can not be quantified by measuring only echo level. Simultaneous measurement of attenuation of ultrasound, which is not easy to do and not done in this study, is prerequisite to quantify fat content

Microinstabilities in a radially contracting inhomogeneous cylindrical plasma slab

International Nuclear Information System (INIS)

Deutsch, R.; Kaeppeler, H.J.

1980-07-01

In order to study the development of microinstabilities in a collapsing cylindrical plasma sheath, corresponding to the situations in a z-pinch or a plasma focus, the dispersion relation for electromagnetic perturbations is derived with the aid of a newly established slab-model for an inhomogeneous, radially contracting plasma. In contrast to previously used slab-models, the orientation of the electric field is in direction of the cylinder axis and the azimuthal magnetic field is induced by the current flowing through the cylindrical plasma slab. The Vlasov equation is used together with the Krook collision term in order to include the influence of collisions. The results of this theory presented in this report will be used to calculate the growth of drift instabilities in the compression phase of a plasma focus, and shall serve as a basis for further development of a more general dispersion relation including runaway-effects. (orig.)

A phantom for quality control in mammography

International Nuclear Information System (INIS)

Gambaccini, M.; Rimondi, O.; Marziani, M.; Toti, A.

1989-01-01

A phantom for evaluating image quality in mammography has been designed and will be used in the Italian national programme ''Dose and Quality in Mammography''. The characteristics of the phantom are (a) about the same X-ray transmission as a 5 cm 50% fat and 50% water breast for energies between 15 and 50 keV and (b) optimum energies for imaging of the test objects (included in the phantom) in very close agreement with the optimum energies for imaging of calcifications and tumours in a 5 cm 50% fat and 50% water breast. An experimental comparison between the prototype and some commercial phantoms was carried out. Measurements are in progress to test the phantom's ability to evaluate the performances of mammographic systems quantitatively. (author)

Quality of Slab Track Construction - Track Alignment Design and Track Geometry

Science.gov (United States)

Šestáková, Janka

2015-05-01

The slab track superstructure design (without ballast) is a perspective construction especially for building tunnels and bridges in the modernized sections of railway tracks in Slovakia. Monitoring of the structure described in this article is focused on the transition areas between standard structure with ballast and slab track construction.

Disorders influences on the focusing effect of all-dielectric photonic crystal slab superlens

Energy Technology Data Exchange (ETDEWEB)

Hu Xiaoyong; Xin Cheng [State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871 (China); Gong Qihuang [State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871 (China)], E-mail: qhgong@pku.edu.cn

2009-04-13

The influences of structure disorders on the subwavelength focusing properties of an all-dielectric photonic crystal slab superlens are theoretically studied. The structure disorders are considered as randomly perturbing the position or diameter of air holes of the photonic crystal slab. The results show that the photonic crystal slab superlens can tolerate within 10% degree of positional disorder or 15% degree of diameter disorder without destroying the focusing function.

Disorders influences on the focusing effect of all-dielectric photonic crystal slab superlens

International Nuclear Information System (INIS)

Hu Xiaoyong; Xin Cheng; Gong Qihuang

2009-01-01

The influences of structure disorders on the subwavelength focusing properties of an all-dielectric photonic crystal slab superlens are theoretically studied. The structure disorders are considered as randomly perturbing the position or diameter of air holes of the photonic crystal slab. The results show that the photonic crystal slab superlens can tolerate within 10% degree of positional disorder or 15% degree of diameter disorder without destroying the focusing function.

Study of entropy generation in a slab with non-uniform internal heat generation

Directory of Open Access Journals (Sweden)

El Haj Assad Mamdouh

2013-01-01

Full Text Available Analysis of entropy generation in a rectangular slab with a nonuniform internal heat generation is presented. Dimensionless local and total entropy generation during steady state heat conduction through the slab are obtained. Two different boundary conditions have been considered in the analysis, the first with asymmetric convection and the second with constant slab surface temperature. Temperature distribution within the slab is obtained analytically. The study investigates the effect of some relevant dimensionless heat transfer parameters on entropy generation. The results show that there exists a minimum local entropy generation but there does not exist a minimum total entropy generation for certain combinations of the heat transfer parameters. The results of calculations are presented graphically.

Phantom cosmology without Big Rip singularity

Energy Technology Data Exchange (ETDEWEB)

Astashenok, Artyom V. [Baltic Federal University of I. Kant, Department of Theoretical Physics, 236041, 14, Nevsky st., Kaliningrad (Russian Federation); Nojiri, Shin' ichi, E-mail: nojiri@phys.nagoya-u.ac.jp [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan); Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan); Odintsov, Sergei D. [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan); Institucio Catalana de Recerca i Estudis Avancats - ICREA and Institut de Ciencies de l' Espai (IEEC-CSIC), Campus UAB, Facultat de Ciencies, Torre C5-Par-2a pl, E-08193 Bellaterra (Barcelona) (Spain); Tomsk State Pedagogical University, Tomsk (Russian Federation); Yurov, Artyom V. [Baltic Federal University of I. Kant, Department of Theoretical Physics, 236041, 14, Nevsky st., Kaliningrad (Russian Federation)

2012-03-23

We construct phantom energy models with the equation of state parameter w which is less than -1, w<-1, but finite-time future singularity does not occur. Such models can be divided into two classes: (i) energy density increases with time ('phantom energy' without 'Big Rip' singularity) and (ii) energy density tends to constant value with time ('cosmological constant' with asymptotically de Sitter evolution). The disintegration of bound structure is confirmed in Little Rip cosmology. Surprisingly, we find that such disintegration (on example of Sun-Earth system) may occur even in asymptotically de Sitter phantom universe consistent with observational data. We also demonstrate that non-singular phantom models admit wormhole solutions as well as possibility of Big Trip via wormholes.

Phantom cosmology without Big Rip singularity

International Nuclear Information System (INIS)

Astashenok, Artyom V.; Nojiri, Shin'ichi; Odintsov, Sergei D.; Yurov, Artyom V.

2012-01-01

We construct phantom energy models with the equation of state parameter w which is less than -1, w<-1, but finite-time future singularity does not occur. Such models can be divided into two classes: (i) energy density increases with time (“phantom energy” without “Big Rip” singularity) and (ii) energy density tends to constant value with time (“cosmological constant” with asymptotically de Sitter evolution). The disintegration of bound structure is confirmed in Little Rip cosmology. Surprisingly, we find that such disintegration (on example of Sun-Earth system) may occur even in asymptotically de Sitter phantom universe consistent with observational data. We also demonstrate that non-singular phantom models admit wormhole solutions as well as possibility of Big Trip via wormholes.

Gaps, tears and seismic anisotropy around the subducting slabs of the Antilles

Science.gov (United States)

Schlaphorst, David; Kendall, J.-Michael; Baptie, Brian; Latchman, Joan L.; Tait, Steve

2017-02-01

Seismic anisotropy in and beneath the subducting slabs of the Antilles is investigated using observations of shear-wave splitting. We use a combination of teleseismic and local events recorded at three-component broadband seismic stations on every major island in the area to map anisotropy in the crust, the mantle wedge and the slab/sub-slab mantle. To date this is the most comprehensive study of anisotropy in this region, involving 52 stations from 8 seismic networks. Local event delay times (0.21 ± 0.12 s) do not increase with depth, indicating a crustal origin in anisotropy and an isotropic mantle wedge. Teleseismic delay times are much larger (1.34 ± 0.47 s), with fast shear-wave polarisations that are predominantly parallel to trend of the arc. These observations can be interpreted three ways: (1) the presence of pre-existing anisotropy in the subducting slab; (2) anisotropy due to sub-slab mantle flow around the eastern margin of the nearly stationary Caribbean plate; (3) some combination of both mechanisms. However, there are two notable variations in the trench-parallel pattern of anisotropy - trench-perpendicular alignment is observed in narrow regions east of Puerto Rico and south of Martinique. These observations support previously proposed ideas of eastward sublithospheric mantle flow through gaps in the slab. Furthermore, the pattern of anisotropy south of Martinique, near Saint Lucia is consistent with a previously proposed location for the boundary between the North and South American plates.

Slab Geometry and Segmentation on Seismogenic Subduction Zone; Insight from gravity gradients

Science.gov (United States)

Saraswati, A. T.; Mazzotti, S.; Cattin, R.; Cadio, C.

2017-12-01

Slab geometry is a key parameter to improve seismic hazard assessment in subduction zones. In many cases, information about structures beneath subduction are obtained from geophysical dedicated studies, including geodetic and seismic measurements. However, due to the lack of global information, both geometry and segmentation in seismogenic zone of many subductions remain badly-constrained. Here we propose an alternative approach based on satellite gravity observations. The GOCE (Gravity field and steady-state Ocean Circulation Explorer) mission enables to probe Earth deep mass structures from gravity gradients, which are more sensitive to spatial structure geometry and directional properties than classical gravitational data. Gravity gradients forward modeling of modeled slab is performed by using horizontal and vertical gravity gradient components to better determine slab geophysical model rather than vertical gradient only. Using polyhedron method, topography correction on gravity gradient signal is undertaken to enhance the anomaly signal of lithospheric structures. Afterward, we compare residual gravity gradients with the calculated signals associated with slab geometry. In this preliminary study, straightforward models are used to better understand the characteristic of gravity gradient signals due to deep mass sources. We pay a special attention to the delineation of slab borders and dip angle variations.

Development of digital phantom for DRR evaluation

International Nuclear Information System (INIS)

Ikeda, Tsuyoshi; Katsuta, Shoichi; Oyama, Masaya; Ogino, Takashi

2009-01-01

Generally, digitally reconstructed radiograph (DRR) is evaluated by physical phantom. The CT image is camouflaged by the performance of the radiation treatment planning system and contains a variety of error factors. The CT image (as follows the digital phantom), where an arbitrary CT value is arranged in the matrix, is necessary to evaluate the pure performance of the radiation treatment planning system. In this study, the development of a digital phantom is described, and the utility is discussed. CTport and the radiation treatment planning system are evaluated with the use of a digital phantom as follows: geometrical accuracy evaluation of DRR, consisting of the center position, size of irradiation field, distortion, extension of X-ray, and beam axis, and the image quality evaluation of DRR, which consists of the contrast resolution. As for DRR made with CTport and the treatment planning system, the part that shifted geometrically was confirmed. In the image quality evaluation, there was a remarkable difference. Because the making accuracy and the installation accuracy of the phantom do not influence the digital phantom, the geometrical accuracy of the DRR is reliable. Because the CT conditions and the phantom factor have no influence, the peculiar DRR image quality can be evaluated and used to evaluate the best image processing parameters. (author)

Evaluation of the possibility to use thick slabs of reconstructed outer breast tomosynthesis slice images

Science.gov (United States)

Petersson, Hannie; Dustler, Magnus; Tingberg, Anders; Timberg, Pontus

2016-03-01

The large image volumes in breast tomosynthesis (BT) have led to large amounts of data and a heavy workload for breast radiologists. The number of slice images can be decreased by combining adjacent image planes (slabbing) but the decrease in depth resolution can considerably affect the detection of lesions. The aim of this work was to assess if thicker slabbing of the outer slice images (where lesions seldom are present) could be a viable alternative in order to reduce the number of slice images in BT image volumes. The suggested slabbing (an image volume with thick outer slabs and thin slices between) were evaluated in two steps. Firstly, a survey of the depth of 65 cancer lesions within the breast was performed to estimate how many lesions would be affected by outer slabs of different thicknesses. Secondly, a selection of 24 lesions was reconstructed with 2, 6 and 10 mm slab thickness to evaluate how the appearance of lesions located in the thicker slabs would be affected. The results show that few malignant breast lesions are located at a depth less than 10 mm from the surface (especially for breast thicknesses of 50 mm and above). Reconstruction of BT volumes with 6 mm slab thickness yields an image quality that is sufficient for lesion detection for a majority of the investigated cases. Together, this indicates that thicker slabbing of the outer slice images is a promising option in order to reduce the number of slice images in BT image volumes.

Optics of turbid slabs

International Nuclear Information System (INIS)

Kokhanovsky, A.A.

2002-01-01

This paper is devoted to an alternative derivation of the asymptotic equations for the reflection and transmission functions of turbid slabs. The derivation is based on the reciprocity principle and the law of conservation of energy. Thus it is very general. This allows us to apply the obtained equations even in cases where the foundations of the radiative transfer theory are in question (e.g. for highly concentrated suspensions and pastes). (author)

Development of the Reference Korean Female Voxel Phantom

International Nuclear Information System (INIS)

Ham, Bo Kyoung; Cho, Kun Woo; Yeom, Yoen Soo; Jeong, Jong Hwi; Kim, Chan Hyeong; Han, Min Cheol

2012-01-01

The objective of this study is for development of the reference Korean female phantom, HDRK-Woman. The phantom was constructed by adjusting a Korean woman voxel phantom to the Reference Korean data. The Korean woman phantom had been developed based on the high-resolution color slice images obtained from an adult Korean female cadaver. There were a total of 39 organs including the 27 organs specified in ICRP 103 for effective dose calculation. The voxel resolution of the phantom was 1.967 X 1.967 X X 2.0619 mm 3 and the voxel array size is 261 X 109 X 825 in the x, y and z directions. Then, the voxel resolution was changed to 2.0351 X 2.0351 X 2.0747 mm 3 for adjustment of the height and total bone mass of the phantom to the Reference Korean data. Finally, the internal organs and tissue were adjusted using in-house software program developed for 3D volume adjustment of the organs and tissue. The effective dose values of HDRK phantoms were calculated for broad parallel photon beams using MCNPX Monte Carlo code and compared with those of ICRP phantoms.

Development of the Reference Korean Female Voxel Phantom

Energy Technology Data Exchange (ETDEWEB)

Ham, Bo Kyoung; Cho, Kun Woo [University of Science and Technology, Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of); Yeom, Yoen Soo; Jeong, Jong Hwi; Kim, Chan Hyeong; Han, Min Cheol [Hanyang University, Seoul (Korea, Republic of)

2012-03-15

The objective of this study is for development of the reference Korean female phantom, HDRK-Woman. The phantom was constructed by adjusting a Korean woman voxel phantom to the Reference Korean data. The Korean woman phantom had been developed based on the high-resolution color slice images obtained from an adult Korean female cadaver. There were a total of 39 organs including the 27 organs specified in ICRP 103 for effective dose calculation. The voxel resolution of the phantom was 1.967 X 1.967 X X 2.0619 mm{sup 3} and the voxel array size is 261 X 109 X 825 in the x, y and z directions. Then, the voxel resolution was changed to 2.0351 X 2.0351 X 2.0747 mm{sup 3} for adjustment of the height and total bone mass of the phantom to the Reference Korean data. Finally, the internal organs and tissue were adjusted using in-house software program developed for 3D volume adjustment of the organs and tissue. The effective dose values of HDRK phantoms were calculated for broad parallel photon beams using MCNPX Monte Carlo code and compared with those of ICRP phantoms.

Development of a physical 3D anthropomorphic breast phantom

Energy Technology Data Exchange (ETDEWEB)

Carton, Ann-Katherine; Bakic, Predrag; Ullberg, Christer; Derand, Helen; Maidment, Andrew D. A. [Department of Radiology, University of Pennsylvania, 1 Silverstein Building, 3400 Spruce Street, Philadelphia, Pennsylvania 19104-4206 (United States); XCounter AB, Svaerdvaegen 11, SE-182 33 Danderyd (Sweden); Department of Radiology, University of Pennsylvania, 1 Silverstein Building, 3400 Spruce Street, Philadelphia, Pennsylvania 19104-4206 (United States)

2011-02-15

Purpose: Develop a technique to fabricate a 3D anthropomorphic breast phantom with known ground truth for image quality assessment of 2D and 3D breast x-ray imaging systems. Methods: The phantom design is based on an existing computer model that can generate breast voxel phantoms of varying composition, size, and shape. The physical phantom is produced in two steps. First, the portion of the voxel phantom consisting of the glandular tissue, skin, and Cooper's ligaments is separated into sections. These sections are then fabricated by high-resolution rapid prototyping using a single material with 50% glandular equivalence. The remaining adipose compartments are then filled using an epoxy-based resin (EBR) with 100% adipose equivalence. The phantom sections are stacked to form the physical anthropomorphic phantom. Results: The authors fabricated a prototype phantom corresponding to a 450 ml breast with 45% dense tissue, deformed to a 5 cm compressed thickness. Both the rapid prototype (RP) and EBR phantom materials are radiographically uniform. The coefficient of variation (CoV) of the relative attenuation between RP and EBR phantom samples was <1% and the CoV of the signal intensity within RP and EBR phantom samples was <1.5% on average. Digital mammography and reconstructed digital breast tomosynthesis images of the authors' phantom were reviewed by two radiologists; they reported that the images are similar in appearance to clinical images, noting there are still artifacts from air bubbles in the EBR. Conclusions: The authors have developed a technique to produce 3D anthropomorphic breast phantoms with known ground truth, yielding highly realistic x-ray images. Such phantoms may serve both qualitative and quantitative performance assessments for 2D and 3D breast x-ray imaging systems.

A device for heat-proofing the closing slab of a fast neutron nuclear reactor

International Nuclear Information System (INIS)

Lemercier, Guy.

1973-01-01

A device proofing the closing-slab comprising a metal-shoe against which is applied said device, the latter being constituted by a plurality of panels, each of which is formed by a padding of superimposed metal-cloths arranged in parallel relationship to the slab to be heat-proofed. Said device is characterized in that each panel is contained in a casing applied against the slab, constituted by two metal half-boxes of parallelepipedic shape embedded into each other. This can be applied to high-power reactors for protecting the slab against the aerosols of the coolant liquid-metal [fr

IMPROVEMENT OF SLAB REHEATING PROCESS AT USIMINAS THROUGH MATHEMATICAL SIMULATION

Directory of Open Access Journals (Sweden)

Antônio Adel dos Santos

2012-09-01

Full Text Available Basic characteristics and application examples of the mathematical simulator for reheating process in walking-beam type furnaces, that has been developed and applied to Usiminas plate mill line at Ipatinga, are shown in this paper. This is a bi-dimensional mathematical model solved by the finite volume method, validated by temperature measurements inside the slab during heating and coded as a visual tool. Among these applications, the following can be highlighted: (i determination of suitable furnace zone temperatures and residence times for processing steels by accelerated cooling technology; (ii determination of slab average temperature at discharging as well as at each zone exit, supplying data to be fed to the automation system at the comissioning stage; (iii analyses of slab thermal distribution through the reheating process, enabling operational optimization

Computational anthropomorphic phantoms for radiation protection dosimetry: evolution and prospects

International Nuclear Information System (INIS)

Lee, Choonsik; Lee, Jaiki

2006-01-01

Computational anthropomorphic phantoms are computer models of human anatomy used in the calculation of radiation dose distribution in the human body upon exposure to a radiation source. Depending on the manner to represent human anatomy, they are categorized into two classes: stylized and tomographic phantoms. Stylized phantoms, which have mainly been developed at the Oak Ridge National Laboratory (ORNL), describe human anatomy by using simple mathematical equations of analytical geometry. Several improved stylized phantoms such as male and female adults, pediatric series, and enhanced organ models have been developed following the first hermaphrodite adult stylized phantom, Medical Internal Radiation Dose (MIRD)-5 phantom. Although stylized phantoms have significantly contributed to dosimetry calculation, they provide only approximations of the true anatomical features of the human body and the resulting organ dose distribution. An alternative class of computational phantom, the tomographic phantom, is based upon three-dimensional imaging techniques such as Magnetic Resonance (MR) imaging and Computed Tomography (CT). The tomographic phantoms represent the human anatomy with a large number of voxels that are assigned tissue type and organ identity. To date, a total of around 30 tomographic phantoms including male and female adults, pediatric phantoms, and even a pregnant female, have been developed and utilized for realistic radiation dosimetry calculation. They are based on MRI/CT images or sectional color photos from patients, volunteers or cadavers. Several investigators have compared tomographic phantoms with stylized phantoms, and demonstrated the superiority of tomographic phantoms in terms of realistic anatomy and dosimetry calculation. This paper summarizes the history and current status of both stylized and tomographic phantoms, including Korean computational phantoms. Advantages, limitations, and future prospects are also discussed

On the operational quantity Hp(3) for eye lens dosimetry

International Nuclear Information System (INIS)

Behrens, R

2012-01-01

In the past the operational quantity H p (3) has been defined for calibration purposes in a slab phantom. Recently, an additional phantom in the form of a cylinder was suggested for eye lens dosimetry as a cylinder much better approximates the shape of a head than a slab. Therefore, this work investigates whether the quantity H p (3), when defined in the respective calibration phantom, adequately estimates the eye lens dose (or is at least conservative) depending on the phantom: it turns out that in most cases both calibration phantoms are similarly well suited. Finally, the definition of the eye lens dose is discussed together with possible consequences on the definition of H p (3): the consideration of only the radiation sensitive volume of the lens causes H p (3) not to be conservative in beta radiation fields. (paper)

WE-D-303-00: Computational Phantoms

Energy Technology Data Exchange (ETDEWEB)

Lewis, John [Duke University Medical Center, Durham, NC (United States); Brigham and Women’s Hospital and Dana-Farber Cancer Institute, Boston, MA (United States)

2015-06-15

Modern medical physics deals with complex problems such as 4D radiation therapy and imaging quality optimization. Such problems involve a large number of radiological parameters, and anatomical and physiological breathing patterns. A major challenge is how to develop, test, evaluate and compare various new imaging and treatment techniques, which often involves testing over a large range of radiological parameters as well as varying patient anatomies and motions. It would be extremely challenging, if not impossible, both ethically and practically, to test every combination of parameters and every task on every type of patient under clinical conditions. Computer-based simulation using computational phantoms offers a practical technique with which to evaluate, optimize, and compare imaging technologies and methods. Within simulation, the computerized phantom provides a virtual model of the patient’s anatomy and physiology. Imaging data can be generated from it as if it was a live patient using accurate models of the physics of the imaging and treatment process. With sophisticated simulation algorithms, it is possible to perform virtual experiments entirely on the computer. By serving as virtual patients, computational phantoms hold great promise in solving some of the most complex problems in modern medical physics. In this proposed symposium, we will present the history and recent developments of computational phantom models, share experiences in their application to advanced imaging and radiation applications, and discuss their promises and limitations. Learning Objectives: Understand the need and requirements of computational phantoms in medical physics research Discuss the developments and applications of computational phantoms Know the promises and limitations of computational phantoms in solving complex problems.

WE-D-303-00: Computational Phantoms

International Nuclear Information System (INIS)

Lewis, John

2015-01-01

Modern medical physics deals with complex problems such as 4D radiation therapy and imaging quality optimization. Such problems involve a large number of radiological parameters, and anatomical and physiological breathing patterns. A major challenge is how to develop, test, evaluate and compare various new imaging and treatment techniques, which often involves testing over a large range of radiological parameters as well as varying patient anatomies and motions. It would be extremely challenging, if not impossible, both ethically and practically, to test every combination of parameters and every task on every type of patient under clinical conditions. Computer-based simulation using computational phantoms offers a practical technique with which to evaluate, optimize, and compare imaging technologies and methods. Within simulation, the computerized phantom provides a virtual model of the patient’s anatomy and physiology. Imaging data can be generated from it as if it was a live patient using accurate models of the physics of the imaging and treatment process. With sophisticated simulation algorithms, it is possible to perform virtual experiments entirely on the computer. By serving as virtual patients, computational phantoms hold great promise in solving some of the most complex problems in modern medical physics. In this proposed symposium, we will present the history and recent developments of computational phantom models, share experiences in their application to advanced imaging and radiation applications, and discuss their promises and limitations. Learning Objectives: Understand the need and requirements of computational phantoms in medical physics research Discuss the developments and applications of computational phantoms Know the promises and limitations of computational phantoms in solving complex problems

Novel Radon Sub-Slab Suctioning System

DEFF Research Database (Denmark)

Rasmussen, Torben Valdbjørn

2013-01-01

A new principle for radon protection is currently presented which makes use of a system of horizontal pressurised air ducts located within the lower part of the rigid insulation layer of the ground-floor slab. The function of this system is based on the principles of pressure reduction within...... a grid of horizontal air ducts with low pressure which are able to remove air and radon from the ground. Results showed the system to be effective in preventing radon infiltrating from the ground through the ground-floor slab, avoiding high concentrations of radon being accumulated inside houses....... For the system to be effective, the pressure within the ducts must be lower than the pressure inside the house. The new principle was shown to be effective in preventing radon from polluting the indoor air by introducing low pressure in the horizontal grid of air ducts. A lower pressure than the pressure inside...

Quality control of portal imaging with PTW EPID QC PHANTOM registered

International Nuclear Information System (INIS)

Pesznyak, Csilla; Kiraly, Reka; Polgar, Istvan; Zarand, Pal; Mayer, Arpad; Fekete, Gabor; Mozes, Arpad; Kiss, Balazs

2009-01-01

Purpose: quality assurance (QA) and quality control (QC) of different electronic portal imaging devices (EPID) and portal images with the PTW EPID QC PHANTOM registered . Material and methods: characteristic properties of images of different file formats were measured on Siemens OptiVue500aSi registered , Siemens BeamView Plus registered , Elekta iView registered , and Varian PortalVision trademark and analyzed with the epidSoft registered 2.0 program in four radiation therapy centers. The portal images were taken with Kodak X-OMAT V registered and the Kodak Portal Localisation ReadyPack registered films and evaluated with the same program. Results: the optimal exposition both for EPIDs and portal films of different kind was determined. For double exposition, the 2+1 MU values can be recommended in the case of Siemens OptiVue500aSi registered , Elekta iView registered and Kodak Portal Localisation ReadyPack registered films, while for Siemens BeamView Plus registered , Varian PortalVision trademark and Kodak X-OMAT V registered film 7+7 MU is recommended. Conclusion: the PTW EPID QC PHANTOM registered can be used not only for amorphous silicon EPIDs but also for images taken with a video-based system or by using an ionization chamber matrix or for portal film. For analysis of QC tests, a standardized format (used at the acceptance test) should be applied, as the results are dependent on the file format used. (orig.)

[Mirror, mirror of the wall: mirror therapy in the treatment of phantom limbs and phantom limb pain].

Science.gov (United States)

Casale, Roberto; Furnari, Anna; Lamberti, Raul Coelho; Kouloulas, Efthimios; Hagenberg, Annegret; Mallik, Maryam

2015-01-01

Phantom limb and phantom limb pain control are pivotal points in the sequence of intervention to bring the amputee to functional autonomy. The alterations of perception and sensation, the pain of the residual limb and the phantom limb are therefore aspects of amputation that should be taken into account in the "prise en charge" of these patients. Within the more advanced physical therapies to control phantom and phantom limb pain there is the use of mirrors (mirror therapy). This article willfocus on its use and on the possible side effects induced by the lack of patient selection and a conflict of body schema restoration through mirror therapy with concurrent prosthetic training and trauma acceptance. Advice on the need to select patients before treatment decisions, with regard to their psychological as well as clinical profile (including time since amputation and clinical setting), and the need to be aware of the possible adverse effects matching different and somehow conflicting therapeutic approaches, are put forward. Thus a coordinated sequence of diagnostic, prognostic and therapeutic procedures carried out by an interdisciplinary rehabilitation team that works globally on all patients' problems is fundamental in the management of amputees and phantom limb pain. Further studies and the development of a multidisciplinary network to study this and other applications of mirror therapy are needed.

Internal slab-column connections under monotonic and cyclic imposed rotations

OpenAIRE

Drakatos, Ioannis-Sokratis; Muttoni, Aurelio; Beyer, Katrin

2016-01-01

Reinforced concrete flat slabs supported by slender columns are often used as gravity load resisting system for buildings in regions of moderate seismicity. Current codes of practice determine the displacement capacity of slab-column connections using empirical formulas which were calibrated against experimental studies. This article reviews and compares test configurations used in past experimental studies and presents the adopted configuration for an experimental investigation on 13 full-sc...

Contrast detail phantom for SPECT

Energy Technology Data Exchange (ETDEWEB)

Cabrejas, M.L. de; Arashiro, J G; Giannone, C. [Comision Nacional de Energia Atomica, Buenos Aires (Argentina); Camuyrano, M; Nohara, G [Universidad de Buenos Aires, Buenos Aires (Argentina). Facultad Ciencias Exactas

1996-06-01

A new low variable contrast phantom for single photon emission computed tomography (SPECT) was constructed, tested and compared with other existing phantoms. It contains simulated cylindrical lesions of four different diameters (D{sub i}), embedded in a cylindrical scattering medium and a uniform section to evaluate tomographic uniformity. The concentration of tracer in the simulated lesions and the scattering medium (background) can be varied to simulate hot and cold lesions. Different applications of the phantom were tested, including determination of the minimum object contrast (OCm) necessary to detect lesions as a function of lesion size, lesion type (hot or cold) and acquisition and processing protocols by visual inspection. This parameter allows categorization of instruments comparing an `image quality index` (IQI). Preliminary comparison with the Britten contrast processing method showed that the detectable OCm was of the same order of magnitude, but the presented device seems more suitable for training and intercomparison purposes. The constructed phantom, of simple design, has proved to be useful for acquisition and processing condition evaluation, OCm estimation and external quality control. (author). 11 refs, 4 figs.

Design and development of a phantom for tomosynthesis with potential for automated analysis via the cloud.

Science.gov (United States)

Goodenough, David; Levy, Josh; Olafsdottir, Hildur; Olafsson, Ingvi

2018-03-06

This paper describes Development of a Phantom for Tomosynthesis with Potential for Automated Analysis via the Cloud. Several studies are underway to investigate the effectiveness of Tomosynthesis Mammographic Image Screening, including the large TMIST project as funded by the National Cancer Institute https://www.cancer.gov/about-cancer/treatment/clinical-trials/nci-supported/tmist. The development of the phantom described in this paper follows initiatives from the FDA, the AAPM TG245 task group, and European Reference Organization (EUREF) for Quality Assured Breast Screening and Diagnostic Services Committee report noting, that no formal endorsement nor recommendation for use has been sought, or granted by any of these groups. This paper reports on the possibility of using this newly developed Tomosynthesis Phantom for Quality Assurance, field testing of image performance, including remote monitoring of DBT system performance, e.g., via transmission over the cloud. The phantom includes tests for: phantom positioning and alignment (important for remote analysis), scan geometry (x and y), chest wall offset, scan slice width and Slice Sensitivity Profile (SSP(z)) slice geometry (slice width), scan slice incrementation (z), z axis geometry bead, low contrast detectability using low contrast spheres, spatial resolution via Point Spread Function (PSF), Image uniformity, Signal to Noise Ratio (SNR), and Contrast to Noise Ratio (CNR) via readings over an Aluminum square. The phantom is designed for use with automated analysis via transmission of images over the cloud and the analysis package includes test of positioning accuracy (roll, pitch, and yaw). Data are shown from several commercial Tomosynthesis Scanners including Fuji, GE, Hologic, IMS-Giotti, and Siemens; however, the focus of this paper is on phantom design, and not in general aimed at direct commercial comparisons, and wherever possible the identity of the data is anonymized. Results of automated analysis of

Characterization of the phantom material Virtual WaterTM in high-energy photon and electron beams

International Nuclear Information System (INIS)

McEwen, M.R.; Niven, D.

2006-01-01

The material Virtual Water TM has been characterized in photon and electron beams. Range-scaling factors and fluence correction factors were obtained, the latter with an uncertainty of around 0.2%. This level of uncertainty means that it may be possible to perform dosimetry in a solid phantom with an accuracy approaching that of measurements in water. Two formulations of Virtual Water TM were investigated with nominally the same elemental composition but differing densities. For photon beams neither formulation showed exact water equivalence--the water/Virtual Water TM dose ratio varied with the depth of measurement with a difference of over 1% at 10 cm depth. However, by using a density (range) scaling factor very good agreement ( TM at all depths was obtained. In the case of electron beams a range-scaling factor was also required to match the shapes of the depth dose curves in water and Virtual Wate TM . However, there remained a difference in the measured fluence in the two phantoms after this scaling factor had been applied. For measurements around the peak of the depth-dose curve and the reference depth this difference showed some small energy dependence but was in the range 0.1%-0.4%. Perturbation measurements have indicated that small slabs of material upstream of a detector have a small (<0.1% effect) on the chamber reading but material behind the detector can have a larger effect. This has consequences for the design of experiments and in the comparison of measurements and Monte Carlo-derived values

Convergence analysis of the rebalance methods in multiplying finite slab having periodic boundary conditions

International Nuclear Information System (INIS)

Hong, Ser Gi; Lee, Young Ouk; Song, Jae Seung

2009-01-01

This paper analyzes the convergence of the rebalance iteration methods for the discrete ordinates transport equation in the multiplying finite slab problem. The finite slab is assumed to be homogeneous and it has the periodic boundary conditions. A general formulation is used to include three well-known rebalance methods of the linearized form in a unified way. The rebalance iteration methods considered in this paper are the CMR (Coarse-Mesh Rebalance), the CMFD (Coarse-Mesh Finite Difference), and p-CMFD (Partial Current-Based Coarse Mesh Finite Difference) methods which have been popularly used in the reactor physics. The convergence analysis is performed with the well-known Fourier analysis through a linearization. The analyses are applied for one-group problems. The theoretical analysis shows that there are one fundamental mode and N-1 Eigen-modes which determine the convergence if the finite slab is divided into N uniform meshes. The numerical tests show that the Fourier convergence analysis provides the reasonable estimate of the numerical spectral radii for the model problems and the spectral radius for the finite slab approaches the one for the infinite slab as the thickness of the slab increases. (author)

Mathematical human phantoms and their application to radiation protection

International Nuclear Information System (INIS)

Yamaguchi, Yasuhiro

1998-01-01

This review described the characteristics of mathematical phantoms, their history over 30 years and their application. Mathematical phantoms are classified into two models of formula and voxel types. In the former, human body and organs are described by 2- and/or 3-D mathematical formula and can be seen as a combination of solid bodies like spheres, cubes and ovals. The phantom is composed from three tissue components (bone, lung and soft tissue) and made on data on Reference Man in ICRP Publ. 23. The latter voxel (volume pixel) phantom consists from a number of small cubes based on CT and MRI images of a certain man. For instance, the phantom CHILD, 1.54 x 1.54 x 8.00 mm 3 in size, is based on a 7-year old child, which consisting from about one million voxels. The mathematical phantom was first made in Oak Ridge National Laboratory in the middle of the nineteen-sixties, which have undergone various improvements to reach MIRD-5 phantom. Thereafter, many similitude phantoms have been made as a variation of MIRD-5, depending on age and sex (e.g., ADAM and EVA). Voxel phantom was made in the middle of nineteen-eighties and have undergone improvements which are continued even currently in Japan, U.S. etc. The mathematical phantoms are used for calculation of radiation transport program by Monte Carlo method in the field of radiation protection. Also in the field of medicine, the phantom is used for calculation of internal and external exposure doses, of correction constants of externally measuring instruments, of doses for neutron capture therapy and of A-bomb exposure doses in Hiroshima and Nagasaki for reevaluation. Recently, the development of phantom is in the current from formula phantom to voxel one due to the purpose of precision and standardization. (K.H.)

Study of global stability of tall buildings with prestressed slabs

Directory of Open Access Journals (Sweden)

L. A. Feitosa

Full Text Available The use of prestressed concrete flat slabs in buildings has been increasing in recent years in the Brazilian market. Since the implementation of tall and slender buildings a trend in civil engineering and architecture fields, arises from the use of prestressed slabs a difficulty in ensuring the overall stability of a building without beams. In order to evaluate the efficiency of the main bracing systems used in this type of building, namely pillars in formed "U" in elevator shafts and stairs, and pillars in which the lengths are significantly larger than their widths, was elaborated a computational models of fictional buildings, which were processed and analyzed using the software CAD/TQS. From the variation of parameters such as: geometry of the pillars, thick slabs, characteristic strength of the concrete, reduceofthe coefficient of inertia for consideration of non-linearities of the physical elements, stiffness of the connections between slabs and pillars, among others, to analyze the influence of these variables on the overall stability of the building from the facing of instability parameter Gama Z, under Brazilian standard NBR 6118, in addition to performing the processing of building using the P-Delta iterative calculation method for the same purpose.

A differentiated plane wave: its passage through a slab

International Nuclear Information System (INIS)

Hannay, J H; Nye, J F

2013-01-01

Differentiating a monochromatic uniform plane electromagnetic wavefield with respect to its direction produces, from a field that is completely lacking in localized specific features, one that contains a straight vortex-like line, a ‘C-line’ of defined circular polarization. There is also a second separate C-line of opposite handedness; indeed, in a sense, a straight line of every polarization is realized. Because of its primitive construction it is analytically simple to study the passage of a differentiated wave obliquely through a plane interface into a medium of different refractive index, to trace its C-line. This was done in an earlier paper. Here we extend the method to passage through a parallel-sided transparent slab. There are multiple reflections within the slab, as in a Fabry–Pérot interferometer. The exiting wave, as a single differentiated plane wave, has a straight oblique C-line. Inside the slab, and in front of it, there is wave interference. The result is a coiled, helix-like, C-line in front of the slab and another inside it. The two coils wrap around separate hyperboloids of one sheet, like cooling towers. The emerging straight C-line is shifted (with respect to a C-line in a notional undisturbed incident plane wave) both in the plane of incidence and transversely to it, and the second C-line behaves similarly. The analysis is exact and could be extended in a straightforward way to a general stratified medium. (paper)

Structural response of reinforced concrete slabs to impulsive loads

International Nuclear Information System (INIS)

Florence, A.L.

1977-01-01

The structure treated here is a clamped circular slab of reinforced concrete. The loading is a rectangular pulse uniformly distributed over a central area. The practical value of this problem is that it probably represents a most severe loading case for bending response among more realistic cases, because it replaces the local loaded area with a circular area at the slab center, and because it replaces the pulse with a rectangular pulse of the same peak pressure and impulse. In the theoretical treatment the pulse is assumed to produce plastic deformations large enough to neglect elastic deformation but small enough to neglect membrane action. Yielding of the reinforced concrete slab is assumed to be governed by the Johansen criterion and the associated flow rule. For simplicity, the analysis is restricted to isotropic slabs with top and bottom steel reinforcement arranged to provide the same yield moment magnitude for positive and negative curvature changes. A consequence of the assumed rigid-perfectly plastic behavior is that the deformation modes may be considered as simple mechanism governed by a yield circle. Moreover, the yield circle is stationary while the constant pressure is being applied and expands to the support once the pressure is removed. After the yield circle has arrived at the support, the remaining deformation occurs in the static collapse mode. The principal results are explicit simple formulas for permanent central deflection in terms of pressure, duration, loaded area radius, and plate properties (radius, density, yield moment)

An approximate solution of the two-group critical problem for reflected slabs

International Nuclear Information System (INIS)

Ishiguro, Y.; Garcia, R.D.M.

1977-01-01

A new approximation is developed to solve two group slab problems involving two media where one of the media is infinite. The method consists in combining the P sub(L) approximation with invariance principles. Several numerical results are reported for the critical slab problem [pt

A dynamic phantom for radionuclide renography

International Nuclear Information System (INIS)

Heikkinen, J.O.

1999-01-01

The aim of the study was to develop and test a dynamic phantom simulating radionuclide renography. The phantom consisted of five partly lead covered plastic containers simulating kidneys, heart, bladder and background (soft tissues, liver and spleen). Dynamics were performed with multiple movable steel plates between containers and a gamma camera. Control of the plates is performed manually with a stopwatch following exact time schedules. The containers were filled with activities ( 99m Tc) which produce count rates close to clinical situations. Count rates produced by the phantom were compared with ten clinical renography cases: five 99m Tc MAG3 and five 99m Tc DTPA examinations. Two phantom simulations were repeated three times with separate fillings, acquisitions and analyses. Precision errors as a coefficient of variation (CV) of repeated measurements were calculated and theoretical values were compared with the corresponding measured ones. A multicentre comparison was made between 19 nuclear medicine laboratories and three clinical cases were simulated with the phantom. Correlations between count rates produced by the phantom and clinical studies were r=0.964 for 99m Tc MAG3 (p 99m Tc DTPA (p max was 4.0±1.6%. Images and curves of the scanned phantom were close to a real patient in all 19 laboratories but calculated parameters varied: the difference between theoretical and measured values for T max was 6.8±6.2%. The difference between laboratories is most probably due to variations in acquisition protocols and analysis programs: 19 laboratories with 18 different protocols and 8 different programs. The dynamics were found to be repeatable and suitable for calibration purposes for radionuclide renography programs and protocols as well as for multicentre comparisons. (author)

Exact solution of thermal energy storage system using PCM flat slabs configuration

International Nuclear Information System (INIS)

Bechiri, Mohammed; Mansouri, Kacem

2013-01-01

Highlights: • An exact solution of a latent heat storage unit (LHSU) consisting of several flat slabs was obtained. • The working fluid (HTF) circulating by forced convection between the slabs charges and discharges the storage unit. • The charging/discharging process is investigated for various HTF working conditions and different design parameters. - Abstract: An analytical investigation of thermal energy storage system (TESS) consisting of several flat slabs of phase change material (PCM) is presented. The working fluid (HTF) circulating on laminar forced convection between the slabs charges and discharges the storage unit. The melting and solidification of the PCM was treated as a radial one dimensional conduction problem. The forced convective heat transfer inside the channels is analyzed by solving the energy equation, which is coupled with the heat conduction equation in the PCM container. The comparison between the present exact solution with the numerical predictions and experimental data available in literature shows good agreement. The charging/discharging process is investigated in terms of liquid–solid interface position, liquid fraction, total heat transmitted to the PCM and thermal storage efficiency for various HTF working conditions and different design parameters such as PCM slab length, fluid passage gap and thickness of PCM duct container

Phantom inflation and the 'Big Trip'

International Nuclear Information System (INIS)

Gonzalez-Diaz, Pedro F.; Jimenez-Madrid, Jose A.

2004-01-01

Primordial inflation is regarded to be driven by a phantom field which is here implemented as a scalar field satisfying an equation of state p=ωρ, with ω-1. Being even aggravated by the weird properties of phantom energy, this will pose a serious problem with the exit from the inflationary phase. We argue, however, in favor of the speculation that a smooth exit from the phantom inflationary phase can still be tentatively recovered by considering a multiverse scenario where the primordial phantom universe would travel in time toward a future universe filled with usual radiation, before reaching the big rip. We call this transition the 'Big Trip' and assume it to take place with the help of some form of anthropic principle which chooses our current universe as being the final destination of the time transition

Charged black holes in phantom cosmology

Energy Technology Data Exchange (ETDEWEB)

Jamil, Mubasher; Qadir, Asghar; Rashid, Muneer Ahmad [National University of Sciences and Technology, Center for Advanced Mathematics and Physics, Rawalpindi (Pakistan)

2008-11-15

In the classical relativistic regime, the accretion of phantom-like dark energy onto a stationary black hole reduces the mass of the black hole. We have investigated the accretion of phantom energy onto a stationary charged black hole and have determined the condition under which this accretion is possible. This condition restricts the mass-to-charge ratio in a narrow range. This condition also challenges the validity of the cosmic-censorship conjecture since a naked singularity is eventually produced due to accretion of phantom energy onto black hole. (orig.)

Phantoms for IMRT dose distribution measurement and treatment verification

International Nuclear Information System (INIS)

Low, Daniel A.; Gerber, Russell L.; Mutic, Sasa; Purdy, James A.

1998-01-01

Background: The verification of intensity-modulated radiation therapy (IMRT) patient treatment dose distributions is currently based on custom-built or modified dose measurement phantoms. The only commercially available IMRT treatment planning and delivery system (Peacock, NOMOS Corp.) is supplied with a film phantom that allows accurate spatial localization of the dose distribution using radiographic film. However, measurements using other dosimeters are necessary for the thorough verification of IMRT. Methods: We have developed a phantom to enable dose measurements using a cylindrical ionization chamber and the localization of prescription isodose curves using a matrix of thermoluminescent dosimetry (TLD) chips. The external phantom cross-section is identical to that of the commercial phantom, to allow direct comparisons of measurements. A supplementary phantom has been fabricated to verify the IMRT dose distributions for pelvis treatments. Results: To date, this phantom has been used for the verification of IMRT dose distributions for head and neck and prostate cancer treatments. Designs are also presented for a phantom insert to be used with polymerizing gels (e.g., BANG-2) to obtain volumetric dose distribution measurements. Conclusion: The phantoms have proven useful in the quantitative evaluation of IMRT treatments

Heat transfer performance of multi-layer insulation structure under roof-slab of pool-type LMFBR

International Nuclear Information System (INIS)

Kinoshita, I.; Yoshida, K.; Uotani, M.; Fukada, T.

1988-01-01

At the normal operation of the pool-type LMFBR, the free surface of liquid sodium at about 500 0 C is present below the roof-slab, separated by a space of the argon cover gas. The temperature of the roof-slab has to be maintained low and uniform in the horizontal direction for sufficient strength of the structure. Therefore, thermal insulation structures must be installed on the lower surface of the roof-slab. In addition to the installation of thermal insulator, forced cooling of the roof-slab is required for assured structural integrity of the roof-slab. The capacity of cooling equipment can be reduced by installation of structures with high thermal insulating performance. The objective of this study is to evaluate the thermal insulation characteristics of multi-layer type insulator installed below the roof-slab by analytically and experimentally. The analytical study is intended to evaluate the effect of number, distance and emissivity of layers on the heat transfer performances. This is treated as the one-dimensional heat transfer with natural convection, conduction and thermal radiation. In the experiments, we have evaluated effects of gap distances between adjacent thermal insulators placed below the roof-slab on the thermal insulation performances

Using the MDCT thick slab MinIP method for the follow-up of pulmonary emphysema.

Science.gov (United States)

Lan, Hai; Nishitani, Hiromu; Nishihara, Sadamitsu; Ueno, Junji; Takao, Shoichiro; Iwamoto, Seiji; Kawanaka, Takashi; Mahmut, Mawlan; Qingge, Si

2011-08-01

The purpose of this study was to evaluate the usefulness of thick slab minimum intensity projection (MinIP) as a follow-up method in patients with pulmonary emphysema. This method was used to determine the presence or absence of changes over time in the lung field based on multi-detector-row CT (MDCT) data. Among patients diagnosed with pulmonary emphysema who underwent 16-MDCT (slice thickness, 1 mm) twice at an interval of 6 months or more, 12 patients without changes in the lung field and 14 with clear changes in the lung field were selected as subjects. An image interpretation experiment was performed by five image interpreters. Pulmonary emphysema was followed up using two types of thick slab MinIP (thick slab MinIP 1 and 2) and multi-planar reformation (MPR), and the results of image interpretation were evaluated by receiver operating characteristic (ROC) analysis. In addition, the time required for image interpretation was compared among the three follow-up methods. The area under the ROC curve (Az) was 0.794 for thick slab MinIP 1, 0.778 for the thick slab MinIP 2, and 0.759 for MPR, showing no significant differences among the three methods. Individual differences in each item were significantly more marked for MPR than for thick slab MinIP. The time required for image interpretation was around 18 seconds for thick slab MinIP 1, 11 seconds for thick slab MinIP 2, and approximately 127 seconds for MPR, showing significant differences among the three methods. There were no significant differences in the results of image interpretation regarding the presence or absence of changes in the lung fields between thick slab MinIP and MPR. However, thick slab MinIP showed a shorter image interpretation time and smaller individual differences in the results among image interpreters than MPR, suggesting the usefulness of this method for determining the presence or absence of changes with time in the lung fields of patients with pulmonary emphysema.

The study of carrying capacity of timber slabs with use the finite elements method

Directory of Open Access Journals (Sweden)

Demeshok Vitalii

2017-01-01

Full Text Available In the article, the results of the study of behavior of timber slab under influence of fire with the standard “time-temperature” curve are presented. The finite element method was used for it. For the calculation we constructed a grid models of timber slabs. As a result of solution of the thermal problem was obtained temperature distribution and the graphs of maximum deflection of timber slabs and its slew rate depending on the time of the test. The obtained graphs allow to obtain data on the occurrence of the limit state of loss of bearing capacity by comparing current values of displacements and velocities with the maximum allowable. Analysis of the graphs shows that the criteria limit state of loss of bearing capacity does not occur. Calculation method of evaluating the fire resistance of timber slabs was developed. For it use database about strain-stress state of this slabs in conditions of influence of the fire.

Experimental phantom verification studies for simulations of light interactions with skin: liquid phantoms

CSIR Research Space (South Africa)

Karsten, A

2010-09-01

Full Text Available stream_source_info Karsten_2010_P.pdf.txt stream_content_type text/plain stream_size 5080 Content-Encoding UTF-8 stream_name Karsten_2010_P.pdf.txt Content-Type text/plain; charset=UTF-8 Experimental phantom verification... studies for simulations of light interactions with skin: Solid Phantoms Aletta E Karsten, A Singh Presented by: J E Smit National Laser Center CSIR South Africa akarsten@csir.co.za Slide 2 © CSIR 2009 www.csir.co.za Where...

SU-F-T-259: GPR Tables for the Estimation of Mid-Plane Dose Using EPID

International Nuclear Information System (INIS)

Annamalai, Gopiraj; Watanabe, Yoichi

2016-01-01

Purpose: To develop a simple method for estimating the mid-plane dose (MPD) of a patient using Electronic Portal imaging Device (EPID). Methods: A Varian TrueBeam with aSi100 EPID was used in this study. The EPID images were acquired for a 30 cm × 30 cm homogeneous slab phantom and a 30 cm diameter 20 cm thick cylindrical phantom in the continuous dosimetry mode. The acquired EPID images in XIM format were imported into in-house MATLAB program for the data analysis. First, the dosimetric characteristics of EPID were studied for dose-response linearity, dose-rate dependence, and field size dependence. Next, the average pixels values of the EPID images were correlated with the MPD measured by an ionisation chamber for various thicknesses of the slab phantom (8 cm – 30 cm) and for various square field sizes (3×3 cm 2 – 25×25 cm 2 at the isocenter). Look-up tables called as GPR tables were then generated for both SSD and SAD setup by taking the ratio of MPD measured by the ionisation chamber and the corresponding EPID pixel values. The accuracy of the GPR tables was evaluated by varying the field size, phantom thickness, and wedge angles with the slab and cylindrical phantoms. Results: The dose response of EPID was linear from 20 MU to 300 MU. The EPID response for different dose rates from 40 MU/min to 600 MU/min was within ±1%. The difference in the doses from the GPR tables and the doses measured by the ionization chambers were within 2% for slab phantoms, and 3% for the cylindrical phantom for various field sizes, phantom thickness, and wedge angles. Conclusion: GPR tables are a ready reckoner for in-vivo dosimetry and it can be used to quickly estimate the MPD value from the EPID images with an accuracy of ±3% for common clinical treatment. project work funded by Union for International cancer control(UICC) under ICRETT fellowship

SU-F-T-259: GPR Tables for the Estimation of Mid-Plane Dose Using EPID

Energy Technology Data Exchange (ETDEWEB)

Annamalai, Gopiraj [Government Arignar Anna Memorial Cancer Hospital & Research Institute, Kanchipuram, TAMILNADU (India); Watanabe, Yoichi [University of Minnesota, Minneapolis, MN (United States)

2016-06-15

Purpose: To develop a simple method for estimating the mid-plane dose (MPD) of a patient using Electronic Portal imaging Device (EPID). Methods: A Varian TrueBeam with aSi100 EPID was used in this study. The EPID images were acquired for a 30 cm × 30 cm homogeneous slab phantom and a 30 cm diameter 20 cm thick cylindrical phantom in the continuous dosimetry mode. The acquired EPID images in XIM format were imported into in-house MATLAB program for the data analysis. First, the dosimetric characteristics of EPID were studied for dose-response linearity, dose-rate dependence, and field size dependence. Next, the average pixels values of the EPID images were correlated with the MPD measured by an ionisation chamber for various thicknesses of the slab phantom (8 cm – 30 cm) and for various square field sizes (3×3 cm{sup 2} – 25×25 cm{sup 2} at the isocenter). Look-up tables called as GPR tables were then generated for both SSD and SAD setup by taking the ratio of MPD measured by the ionisation chamber and the corresponding EPID pixel values. The accuracy of the GPR tables was evaluated by varying the field size, phantom thickness, and wedge angles with the slab and cylindrical phantoms. Results: The dose response of EPID was linear from 20 MU to 300 MU. The EPID response for different dose rates from 40 MU/min to 600 MU/min was within ±1%. The difference in the doses from the GPR tables and the doses measured by the ionization chambers were within 2% for slab phantoms, and 3% for the cylindrical phantom for various field sizes, phantom thickness, and wedge angles. Conclusion: GPR tables are a ready reckoner for in-vivo dosimetry and it can be used to quickly estimate the MPD value from the EPID images with an accuracy of ±3% for common clinical treatment. project work funded by Union for International cancer control(UICC) under ICRETT fellowship.

Prediction of qualitative parameters of slab steel ingot using numerical modelling

Directory of Open Access Journals (Sweden)

M. Tkadlečková

2016-07-01

Full Text Available The paper describes the verification of casting and solidification of heavy slab ingot weighing 40 t from tool steel by means of numerical modelling with use of a finite element method. The pre-processing, processing and post-processing phases of numerical modelling are outlined. Also, the problems with determination of the thermodynamic properties of materials and with determination of the heat transfer between the individual parts of the casting system are discussed. The final porosity, macrosegregation and the risk of cracks were predicted. The results allowed us to use the slab ingot instead of the conventional heavy steel ingot and to improve the ratio, the chamfer and the external shape of the wall of the new design of the slab ingot.

Theoretical Investigations on the Structural Behavior of Biaxial Hollow Concrete Slabs

Directory of Open Access Journals (Sweden)

Nazar Kamel Ali Oukaili

2015-06-01

Full Text Available This paper presents a numerical analysis using ANSYS finite element program to simulate the reinforced concrete slabs with spherical voids. Six full-scale one way bubbled slabs of (3000mm length with rectangular cross-sectional area of (460mm width and (150mm depth are tested as simply supported under two-concentrated load. The results of the finite element model are presented and compared with the experimental data of the tested slabs. Material nonlinearities due to cracking and crushing of concrete and yielding of reinforcement are considered. The general behavior of the finite element models represented by the load-deflection curves at midspan, crack pattern, ultimate load, load-concrete strain curves and failure modes shows good agreement with the experimental data.

Simulation of a Quality Control Jaszczak Phantom with SIMIND Monte Carlo and Adding the Phantom as an Accessory to the Program

International Nuclear Information System (INIS)

Pirayesh Islamian, J.; Bahreyni Toosi, M. T.; Momennezhad, M.; Naseri, Sh.; Ljungberg, M.

2012-01-01

Quality control is an important phenomenon in nuclear medicine imaging. A Jaszczak SPECT Phantom provides consistent performance information for any SPECT or PET system. This article describes the simulation of a Jaszczak phantom and creating an executable phantom file for comparing assessment of SPECT cameras using SIMIND Monte Carlo simulation program which is well-established for SPECT. The simulation was based on a Deluxe model of Jaszczak Phantom with defined geometry. Quality control tests were provided together with initial imaging example and suggested use for the assessment of parameters such as spatial resolution, limits of lesion detection, and contrast comparing with a Siemens E.Cam SPECT system. The phantom simulation was verified by matching tomographic spatial resolution, image contrast, and also uniformity compared with the experiment SPECT of the phantom from filtered backprojection reconstructed images of the spheres and rods. The calculated contrasts of the rods were 0.774, 0.627, 0.575, 0.372, 0.191, and 0.132 for an experiment with the rods diameters of 31.8, 25.4, 19.1, 15.9, 12.7, and 9.5 mm, respectively. The calculated contrasts of simulated rods were 0.661, 0.527, 0.487, 0.400, 0.23, and 0.2 for cold rods and also 0.92, 0.91, 0.88, 0.81, 0.76, and 0.56 for hot rods. Reconstructed spatial tomographic resolution of both experiment and simulated SPECTs of the phantom obtained about 9.5 mm. An executable phantom file and an input phantom file were created for the SIMIND Monte Carlo program. This phantom may be used for simulated SPECT systems and would be ideal for verification of the simulated systems with real ones by comparing the results of quality control and image evaluation. It is also envisaged that this phantom could be used with a range of radionuclide doses in simulation situations such as cold, hot, and background uptakes for the assessment of detection characteristics when a new similar clinical SPECT procedure is being simulated.

Simulation of a Quality Control Jaszczak Phantom with SIMIND Monte Carlo and Adding the Phantom as an Accessory to the Program

Directory of Open Access Journals (Sweden)

Jalil Pirayesh Islamian

2012-03-01

Full Text Available Introduction Quality control is an important phenomenon in nuclear medicine imaging. A Jaszczak SPECT Phantom provides consistent performance information for any SPECT or PET system. This article describes the simulation of a Jaszczak phantom and creating an executable phantom file for comparing assessment of SPECT cameras using SIMIND Monte Carlo simulation program which is well-established for SPECT. Materials and Methods The simulation was based on a Deluxe model of Jaszczak Phantom with defined geometry. Quality control tests were provided together with initial imaging example and suggested use for the assessment of parameters such as spatial resolution, limits of lesion detection, and contrast comparing with a Siemens E.Cam SPECT system. Results The phantom simulation was verified by matching tomographic spatial resolution, image contrast, and also uniformity compared with the experiment SPECT of the phantom from filtered backprojection reconstructed images of the spheres and rods. The calculated contrasts of the rods were 0.774, 0.627, 0.575, 0.372, 0.191, and 0.132 for an experiment with the rods diameters of 31.8, 25.4, 19.1, 15.9, 12.7, and 9.5 mm, respectively. The calculated contrasts of simulated rods were 0.661, 0.527, 0.487, 0.400, 0.23, and 0.2 for cold rods and also 0.92, 0.91, 0.88, 0.81, 0.76, and 0.56 for hot rods. Reconstructed spatial tomographic resolution of both experiment and simulated SPECTs of the phantom obtained about 9.5 mm. An executable phantom file and an input phantom file were created for the SIMIND Monte Carlo program. Conclusion This phantom may be used for simulated SPECT systems and would be ideal for verification of the simulated systems with real ones by comparing the results of quality control and image evaluation. It is also envisaged that this phantom could be used with a range of radionuclide doses in simulation situations such as cold, hot, and background uptakes for the assessment of detection

Usage of prestressed vertical bolts for retrofitting flat slabs damaged due to punching shear

Directory of Open Access Journals (Sweden)

Hamed S. Askar

2015-09-01

An experimental investigation with the objective of retrofitting flat slabs damaged due to punching shear using prestressed vertical bolts is presented in this paper. The parameters examined in this study are vertical prestressed bolts with different ratios within the slab thickness, slab thickness and central column size. Through the experimental tests the load carrying capacity, deformation characteristics and the cracking behavior have been investigated. A comparison between the behavior of retrofitted slabs and their references showed that the proposed system of repair is effective and could be used in practice. A comparison between the experimental results and calculated punching failure load based on the formulas adopted by different codes, showed a reasonable agreement.

External Auditing on Absorbed Dose Using a Solid Water Phantom for Domestic Radiotherapy Facilities

Energy Technology Data Exchange (ETDEWEB)

Choi, Chang Heon; Kim, Jung In; Park, Jong Min; Park, Yang Kyun; Ye, Sung Joon [Medical Research Center, Seoul National University College of Medicine, Seoul (Korea, Republic of); Cho, Kun Woo; Cho, Woon Kap [Radiation Research, Korean Institute of Nuclear Safety, Daejeon (Korea, Republic of); Lim, Chun Il [Korea Food and Drug Administration, Seoul (Korea, Republic of)

2010-11-15

We report the results of an external audit on the absorbed dose of radiotherapy beams independently performed by third parties. For this effort, we developed a method to measure the absorbed dose to water in an easy and convenient setup of solid water phantom. In 2008, 12 radiotherapy centers voluntarily participated in the external auditing program and 47 beams of X-ray and electron were independently calibrated by the third party's American Association of Physicists in Medicine (AAPM) task group (TG)-51 protocol. Even though the AAPM TG-51 protocol recommended the use of water, water as a phantom has a few disadvantages, especially in a busy clinic. Instead, we used solid water phantom due to its reproducibility and convenience in terms of setup and transport. Dose conversion factors between solid water and water were determined for photon and electron beams of various energies by using a scaling method and experimental measurements. Most of the beams (74%) were within {+-}2% of the deviation from the third party's protocol. However, two of 20 X-ray beams and three of 27 electron beams were out of the tolerance ({+-}3%), including two beams with a >10% deviation. X-ray beams of higher than 6 MV had no conversion factors, while a 6 MV absorbed dose to a solid water phantom was 0.4% less than the dose to water. The electron dose conversion factors between the solid water phantom and water were determined: The higher the electron energy, the less is the conversion factor. The total uncertainty of the TG-51 protocol measurement using a solid water phantom was determined to be {+-}1.5%. The developed method was successfully applied for the external auditing program, which could be evolved into a credential program of multi-institutional clinical trials. This dosimetry saved time for measuring doses as well as decreased the uncertainty of measurement possibly resulting from the reference setup in water.

Puzzles of dark energy in the Universe—phantom

International Nuclear Information System (INIS)

Dabrowski, Mariusz P

2015-01-01

This paper is devoted to some simple approach based on general physics tools to describe the physical properties of a hypothetical particle which can be the source of dark energy in the Universe known as phantom. Phantom is characterized by the fact that it possesses negative momentum and kinetic energy and that it gives dominant negative pressure which acts as antigravity. We consider a phantom harmonic oscillator in comparison to a standard harmonic oscillator. By using the first law of thermodynamics we explain why the energy density of the Universe grows when it is filled with phantom. We also show how the collision of phantom with a standard particle leads to extraction of energy from the former by the latter (i.e. from phantom to the standard) if their masses are different. The most striking of our conclusions is that the collision of phantom and standard particles of the same mass is impossible unless both of them are at rest and suddenly start moving with opposite velocities and kinetic energies. This effect is a classic analog of quantum mechanical particle pair creation in a strong electric field or physical vacuum. (paper)

Slab1.0: A three-dimensional model of global subduction zone geometries

Science.gov (United States)

Hayes, Gavin P.; Wald, David J.; Johnson, Rebecca L.

2012-01-01

We describe and present a new model of global subduction zone geometries, called Slab1.0. An extension of previous efforts to constrain the two-dimensional non-planar geometry of subduction zones around the focus of large earthquakes, Slab1.0 describes the detailed, non-planar, three-dimensional geometry of approximately 85% of subduction zones worldwide. While the model focuses on the detailed form of each slab from their trenches through the seismogenic zone, where it combines data sets from active source and passive seismology, it also continues to the limits of their seismic extent in the upper-mid mantle, providing a uniform approach to the definition of the entire seismically active slab geometry. Examples are shown for two well-constrained global locations; models for many other regions are available and can be freely downloaded in several formats from our new Slab1.0 website, http://on.doi.gov/d9ARbS. We describe improvements in our two-dimensional geometry constraint inversion, including the use of ‘average’ active source seismic data profiles in the shallow trench regions where data are otherwise lacking, derived from the interpolation between other active source seismic data along-strike in the same subduction zone. We include several analyses of the uncertainty and robustness of our three-dimensional interpolation methods. In addition, we use the filtered, subduction-related earthquake data sets compiled to build Slab1.0 in a reassessment of previous analyses of the deep limit of the thrust interface seismogenic zone for all subduction zones included in our global model thus far, concluding that the width of these seismogenic zones is on average 30% larger than previous studies have suggested.

A 526 W Diode-Pumped Nd:YAG Ceramic Slab Laser

International Nuclear Information System (INIS)

Chen Yan-Zhong; Bo Yong; Xu Jian; Xu Yi-Ting; Xu Jia-Lin; Guo Ya-Ding; Yang Feng-Tu; Peng Qin-Jun; Cui Da-Fu; Xu Zu-Yan; Liu Wen-Bin; Jiang Ben-Xue; Kou Hua-Min; Pan Yu-Bai; Jiang Dong-Liang

2011-01-01

A diode-side-pumped Nd:YAG ceramic slab laser with a high power output is presented. An average power of 526 W is achieved at 1064 nm with a repetition rate of 120 Hz and a pulse width of 180 μs from a 93mm × 52mm × 8 mm ceramic slab at a pump power of 1928 W, corresponding to an optical-to-optical efficiency of 27.3%. (fundamental areas of phenomenology(including applications))

CAISSON TYPE HOLLOW FLOOR SLABS OF MONOLITHIC MULTI-STOREYED BUILDINGS

OpenAIRE

Malakhova Anna Nikolaevna

2016-01-01

One of the disadvantages of building structures made of reinforced concrete is their considerable weight. One of the trends to decrease the weight of concrete structures, including floor slabs, is the arrangement of voids in the cross-sectional building structures. In Russian and foreign practice paper, cardboard and plastic tubes has been used for creation of voids in the construction of monolithic floor slabs. Lightweight concretes were also used for production of precast hollow core floor ...

Surface correlation effects in two-band strongly correlated slabs.

Science.gov (United States)

Esfahani, D Nasr; Covaci, L; Peeters, F M

2014-02-19

Using an extension of the Gutzwiller approximation for an inhomogeneous system, we study the two-band Hubbard model with unequal band widths for a slab geometry. The aim is to investigate the mutual effect of individual bands on the spatial distribution of quasi-particle weight and charge density, especially near the surface of the slab. The main effect of the difference in band width is the presence of two different length scales corresponding to the quasi-particle profile of each band. This is enhanced in the vicinity of the critical interaction of the narrow band where an orbitally selective Mott transition occurs and a surface dead layer forms for the narrow band. For the doped case, two different regimes of charge transfer between the surface and the bulk of the slab are revealed. The charge transfer from surface/center to center/surface depends on both the doping level and the average relative charge accumulated in each band. Such effects could also be of importance when describing the accumulation of charges at the interface between structures made of multi-band strongly correlated materials.

ICRU activity in the field of phantoms in diagnostic radiology

International Nuclear Information System (INIS)

Wambersie, A.

1992-01-01

The ICRU Report on 'Phantoms and Computational Models in Radiation Therapy, Diagnosis and Protection' is presented. Different types of phantoms may be defined. They may be broadly categorized according to their primary function: dosimetry, calibration and imaging. Within each functional category, there are 3 types or designs of phantoms: body phantoms (anthropomorphic), standard phantoms and reference phantoms (used in the definition and specification of certain radiation quantities). In radiological imaging, anthropomorphic body phantoms are used for measuring the absorbed dose distribution resulting from imaging procedures. Standard phantoms have simple reproducible geometry and are used for comparing measurements under standard conditions of exposure. Imaging phantoms are useful for evaluating a given imaging system; they contain different types of test pieces. The report contains a major section on human anatomy, from fetus to adult with the variations due to ethnic origin. Tolerance levels for the phantoms (composition, dimensions) are proposed and quality assurance programs are outlined. The report contains extensive appendices; human anatomical data and full specification of over 80 phantoms and computational models. ICRU Report 46 on 'Photon, electron, proton and neutron interaction data for body tissues' is closely related to the field of phantoms. It is a logical continuation on ICRU Report 44 (1989) on 'Tissue substitutes in radiation dosimetry and measurements' and contains the interaction data for more than 100 tissues, from fetal to adult, including some diseased tissues

Criticality of neutron transport in a slab with finite reflectors

International Nuclear Information System (INIS)

Pao, C.V.

1978-01-01

The purpose of this paper is to investigate the subcriticality and the supercriticality for the neutron transport in a slab which is surrounded by two finite reflectors. The mathematical problem is to determine when the coupled boundary-value problem has or has no positive solution. It is shown under some explicit conditions on the material properties of the transport mediums and the size of the slab length that the coupled problem has a unique solution which insures the subcriticality of the system. It is also shown under some different conditions on the same physical quantities that the system cannot have a nonnegative solution when there is an external source, and it only has the trivial solution when there is no source in the system. This conclusion leads to the supercriticality of the system. Both upper and lower bounds for the critical length of the slab are explicitly given

Surface wave propagation in steady ideal Hall-magnetohydrodynamic magnetic slabs

International Nuclear Information System (INIS)

Miteva, Rossitsa; Zhelyazkov, Ivan; Erdelyi, Robert

2003-01-01

This paper studies the dispersion characteristics of sausage and kink surface waves traveling along a plasma layer within the framework of Hall magnetohydrodynamics in steady state. While in a static plasma slab these waves are Alfven ones (their phase velocities are close to the Alfven speed in the layer); in a slab with steady flows they may become super Alfvenic waves. Moreover, there exist two types of waves: forward and backward ones bearing in mind that the flow velocity defines the positive (forward) direction. As a typical representative of a magnetic slab in steady state here is considered a solar wind flux rope with a finite β plasma flow (typically β∼1).The forward sausage surface mode exhibits an increased dispersion at small wave numbers while the forward kink waves become practically non-dispersive. Both backward propagating sausage and kink surface modes show an increased dispersion for large wave numbers

Seismicity Structure of the Downgoing Nazca Slab in Northern Chile

Science.gov (United States)

Sippl, C.; Schurr, B.

2017-12-01

We applied an automatized earthquake detection and location algorithm to 8 years of continuous seismic data from the IPOC network in Northern Chile, located in the forearc between about 18.5°S and 24°S. The resulting seismicity catalog contains more than 113k double-difference relocated earthquake hypocenters and features a completeness magnitude around 2.8. Despite the occurrence of two megathrust earthquakes with vigorous aftershock seismicity in the studied time period (the 2007 Tocopilla and the 2014 Iquique earthquakes), >60% of the retrieved seismicity is located in a highly active band of intermediate-depth earthquakes (80-120 km deep) within the downgoing Nazca slab.We obtain a triple seismic zone in the updip part of the slab, with the three parallel dipping planes corresponding to the plate interface, the oceanic Moho (ca. 8 km below the interface) and a third band in the mantle lithosphere 26-28 km beneath the slab top. The plate interface seismicity terminates abruptly at a depth of 55 km. At about 80-90 km depth, the remaining two planes of seismicity then merge into the single, 20 km thick cluster of vigorous seismicity mentioned above, which terminates at 120 km depth. This cluster is located directly beneath the volcanic arc and shows a pronounced kink in the slab dipping angle. Intra-slab seismicity is most likely related to metamorphic dehydration reactions, hence our high-resolution earthquake distribution can be considered a map of metamorphic reactions (although a possibly incomplete one, since not all reactions necessarily invoke seismicity). By correlating this distribution with isotherms from thermal models as well as geophysical imaging results from previous studies, we attempt to get a glimpse at the processes that produce the different patches of intraslab seismicity at intermediate depths.

Optimization of a slab heating pattern for minimum energy consumption in a walking-beam type reheating furnace

International Nuclear Information System (INIS)

Jang, Jiin-Yuh; Huang, Jun-Bo

2015-01-01

A two-dimensional mathematical heat transfer model for the prediction of the temperature history of steel slabs was performed in order to obtain the optimal heating pattern of these slabs with minimum energy consumption in a walking-beam type reheating furnace. An algorithm developed with a simplified conjugated-gradient method combined with a shooting method, was used as an optimizer to design the furnace temperature distribution, including the preheating zone, heating zone and soaking zone temperatures. Comparison with the in-situ experimental data indicated that the present heat transfer model works well for the prediction of the thermal behavior of a slab in the reheating furnace. The effect of the furnace temperature distribution on the design requirements, such as energy required for heating a slab, slab temperature uniformity at the furnace exit and slab discharging temperature, were investigated. The parametric study results indicated that energy consumption significantly decreases with reductions in the preheating zone temperature. The optimal design also resulted in lower energy consumption for heating a slab as compared to the original operational conditions in the steel plant. - Highlights: • The heating process of steel slabs in a reheating furnace is numerically simulated. • An algorithm is developed to search for the optimal heating pattern of a slab. • Energy consumption decreases with reductions in the preheating zone temperature

Hydrodynamic electron flow in a Weyl semimetal slab: Role of Chern-Simons terms

Science.gov (United States)

Gorbar, E. V.; Miransky, V. A.; Shovkovy, I. A.; Sukhachov, P. O.

2018-05-01

The hydrodynamic flow of the chiral electron fluid in a Weyl semimetal slab of finite thickness is studied by using the consistent hydrodynamic theory. The latter includes viscous, anomalous, and vortical effects, as well as accounts for dynamical electromagnetism. The energy and momentum separations between the Weyl nodes are taken into account via the topological Chern-Simons contributions in the electric current and charge densities in Maxwell's equations. When an external electric field is applied parallel to the slab, it is found that the electron fluid velocity has a nonuniform profile determined by the viscosity and the no-slip boundary conditions. Most remarkably, the fluid velocity field develops a nonzero component across the slab that gradually dissipates when approaching the surfaces. This abnormal component of the flow arises due to the anomalous Hall voltage induced by the topological Chern-Simons current. Another signature feature of the hydrodynamics in Weyl semimetals is a strong modification of the anomalous Hall current along the slab in the direction perpendicular to the applied electric field. Additionally, it is found that the topological current induces an electric potential difference between the surfaces of the slab that is strongly affected by the hydrodynamic flow.

Effect of CFRP and TRM Strengthening of RC Slabs on Punching Shear Strength

Directory of Open Access Journals (Sweden)

Husain Abbas

Full Text Available Abstract The paper presents experiments involving punching of RC slabs strengthened using externally bonded carbon fiber reinforced polymer (CFRP sheet and textile reinforced mortar (TRM. Twelve RC slab specimens of two concrete grades (39.9 and 63.2 MPa and employing two strengthening schemes (CFRP and TRM were tested. Specimens were supported on two opposite edges. Experimental load-displacement variations show two peak loads in strengthened slabs and one peak followed by a plateau in control. Second peak or the plateau corresponds to the combined action of aggregate interlock and the dowel action of back face rebars and strengthening layers. The dowel action of back face rebars and strengthening layers had no role in ultimate punching load (i.e. first peak. Strengthened slabs showed 9-18% increase in ultimate punching load (i.e. first peak whereas there was significant increase in the second peak load (190-276% for CFRP; 55-136% for TRM and energy absorption (~66% for CFRP and 22-56% for TRM. An analytical model was also developed for predicting the punching shear strength (first and second peaks of strengthened slabs showing good comparison with experiments.

Experimental and numerical investigation of slabs on ground subjected to concentrated loads

Science.gov (United States)

Øverli, Jan

2014-09-01

An experimental program is presented where a slab on ground is subjected to concentrated loading at the centre, the edges and at the corners. Analytical solutions for the ultimate load capacity fit well with the results obtained in the tests. The non-linear behaviour of the slab is captured by performing nonlinear finite element analyses. The soil is modelled as a no-tension bedding and a smeared crack approach is employed for the concrete. Through a parametric study, the finite element model has been used to assess the influence of subgrade stiffness and shrinkage. The results indicate that drying shrinkage can cause severe cracking in slabs on grade.

Experimental Study on the Structural Behavior of HSC Slab under out of plane load

International Nuclear Information System (INIS)

Ham, K. W.; Lee, K. J.; Park, D. S.

2009-01-01

HSC(Half Steel plate Concrete) Slab is a kind of SC(Steel plate Concrete) structure, so it has a similar advantage of SC structures (short construction period, lower cost and good quality control compared to RC). To apply HSC to the slab of containment building of NPP, several test with different test condition (shear span ratio, shear bar, loading type) were conducted to verify structural behavior of HSC slab structure under out of plane loading

Development and test of sets of 3D printed age-specific thyroid phantoms for 131I measurements

Science.gov (United States)

Beaumont, Tiffany; Caldeira Ideias, Pedro; Rimlinger, Maeva; Broggio, David; Franck, Didier

2017-06-01

In the case of a nuclear reactor accident the release contains a high proportion of iodine-131 that can be inhaled or ingested by members of the public. Iodine-131 is naturally retained in the thyroid and increases the thyroid cancer risk. Since the radiation induced thyroid cancer risk is greater for children than for adults, the thyroid dose to children should be assessed as accurately as possible. For that purpose direct measurements should be carried out with age-specific calibration factors but, currently, there is no age-specific thyroid phantoms allowing a robust measurement protocol. A set of age-specific thyroid phantoms for 5, 10, 15 year old children and for the adult has been designed and 3D printed. A realistic thyroid shape has been selected and material properties taken into account to simulate the attenuation of biological tissues. The thyroid volumes follow ICRP recommendations and the phantoms also include the trachea and a spine model. Several versions, with or without spine, with our without trachea, with or without age-specific neck have been manufactured, in order to study the influence of these elements on calibration factors. The calibration factor obtained with the adult phantom and a reference phantom are in reasonable agreement. In vivo calibration experiments with germanium detectors have shown that the difference in counting efficiency, the inverse of the calibration factor, between the 5 year and adult phantoms is 25% for measurement at contact. It is also experimentally evidenced that the inverse of the calibration factor varies linearly with the thyroid volume. The influence of scattering elements like the neck or spine is not evidenced by experimental measurements.

Patient specific 3D printed phantom for IMRT quality assurance

International Nuclear Information System (INIS)

Ehler, Eric D; Higgins, Patrick D; Dusenbery, Kathryn E; Barney, Brett M

2014-01-01

The purpose of this study was to test the feasibility of a patient specific phantom for patient specific dosimetric verification. Using the head and neck region of an anthropomorphic phantom as a substitute for an actual patient, a soft-tissue equivalent model was constructed with the use of a 3D printer. Calculated and measured dose in the anthropomorphic phantom and the 3D printed phantom was compared for a parallel-opposed head and neck field geometry to establish tissue equivalence. A nine-field IMRT plan was constructed and dose verification measurements were performed for the 3D printed phantom as well as traditional standard phantoms. The maximum difference in calculated dose was 1.8% for the parallel-opposed configuration. Passing rates of various dosimetric parameters were compared for the IMRT plan measurements; the 3D printed phantom results showed greater disagreement at superficial depths than other methods. A custom phantom was created using a 3D printer. It was determined that the use of patient specific phantoms to perform dosimetric verification and estimate the dose in the patient is feasible. In addition, end-to-end testing on a per-patient basis was possible with the 3D printed phantom. Further refinement of the phantom construction process is needed for routine use. (paper)

Influence of Manufacturing Processes on the Performance of Phantom Lungs

International Nuclear Information System (INIS)

Traub, Richard J.

2008-01-01

Chest counting is an important tool for estimating the radiation dose to individuals who have inhaled radioactive materials. Chest counting systems are calibrated by counting the activity in the lungs of phantoms where the activity in the phantom lungs is known. In the United States a commonly used calibration phantom was developed at the Lawrence Livermore National Laboratory and is referred to as the Livermore Torso Phantom. An important feature of this phantom is that the phantom lungs can be interchanged so that the counting system can be challenged by different combinations of radionuclides and activity. Phantom lungs are made from lung tissue substitutes whose constituents are foaming plastics and various adjuvants selected to make the lung tissue substitute similar to normal healthy lung tissue. Some of the properties of phantom lungs cannot be readily controlled by phantom lung manufacturers. Some, such as density, are a complex function of the manufacturing process, while others, such as elemental composition of the bulk plastic are controlled by the plastics manufacturer without input, or knowledge of the phantom manufacturer. Despite the fact that some of these items cannot be controlled, they can be measured and accounted for. This report describes how manufacturing processes can influence the performance of phantom lungs. It is proposed that a metric that describes the brightness of the lung be employed by the phantom lung manufacturer to determine how well the phantom lung approximates the characteristics of a human lung. For many purposes, the linear attenuation of the lung tissue substitute is an appropriate surrogate for the brightness

Assessing the role of slab rheology in coupled plate-mantle convection models

Science.gov (United States)

Bello, Léa; Coltice, Nicolas; Tackley, Paul J.; Dietmar Müller, R.; Cannon, John

2015-11-01

Reconstructing the 3D structure of the Earth's mantle has been a challenge for geodynamicists for about 40 yr. Although numerical models and computational capabilities have substantially progressed, parameterizations used for modeling convection forced by plate motions are far from being Earth-like. Among the set of parameters, rheology is fundamental because it defines in a non-linear way the dynamics of slabs and plumes, and the organization of lithosphere deformation. In this study, we evaluate the role of the temperature dependence of viscosity (variations up to 6 orders of magnitude) and the importance of pseudo-plasticity on reconstructing slab evolution in 3D spherical models of convection driven by plate history models. Pseudo-plasticity, which produces plate-like behavior in convection models, allows a consistent coupling between imposed plate motions and global convection, which is not possible with temperature-dependent viscosity alone. Using test case models, we show that increasing temperature dependence of viscosity enhances vertical and lateral coherence of slabs, but leads to unrealistic slab morphologies for large viscosity contrasts. Introducing pseudo-plasticity partially solves this issue, producing thin laterally and vertically more continuous slabs, and flat subduction where trench retreat is fast. We evaluate the differences between convection reconstructions employing different viscosity laws to be very large, and similar to the differences between two models with the same rheology but using two different plate histories or initial conditions.

Modified creep and shrinkage prediction model B3 for serviceability limit state analysis of composite slabs

Science.gov (United States)

Gholamhoseini, Alireza

2016-03-01

Relatively little research has been reported on the time-dependent in-service behavior of composite concrete slabs with profiled steel decking as permanent formwork and little guidance is available for calculating long-term deflections. The drying shrinkage profile through the thickness of a composite slab is greatly affected by the impermeable steel deck at the slab soffit, and this has only recently been quantified. This paper presents the results of long-term laboratory tests on composite slabs subjected to both drying shrinkage and sustained loads. Based on laboratory measurements, a design model for the shrinkage strain profile through the thickness of a slab is proposed. The design model is based on some modifications to an existing creep and shrinkage prediction model B3. In addition, an analytical model is developed to calculate the time-dependent deflection of composite slabs taking into account the time-dependent effects of creep and shrinkage. The calculated deflections are shown to be in good agreement with the experimental measurements.

Research and application of active hollow core slabs in building systems for utilizing low energy sources

International Nuclear Information System (INIS)

Xu, Xinhua; Yu, Jinghua; Wang, Shengwei; Wang, Jinbo

2014-01-01

Highlights: • A review on the development and modeling of active hollow core slab is presented. • The applications and performance evaluation of the slab in building are reviewed. • Finite element or finite difference method is often used in multidimensional model. • Performance evaluations of building using active slabs for ventilation are limited. • More works on the active hollow core slab are worthwhile. - Abstract: The society and the building professionals have paid much concern in recent years on building energy efficiency and the development and applications of low energy technologies for buildings/green buildings allowing the elimination, or at least reduction of dependence on electricity or fossil fuel while maintaining acceptable indoor environment. Utilizations of favorable diurnal temperature difference and ground thermal source for air conditioning are among these low energy technologies. Utilization of the hollow cores in the prefabricated slab for ventilation and the mass of the slab for thermal storage is widely used in building systems in Europe by exploiting the low energy source of the ambient air. These hollow core slabs aim at enlarging the heat transfer surface between the slab mass and the air in the core, which permits substantial heat flows even for relatively small temperature differences. This, in turn, allows the use of low energy cooling or heating sources, such as the ground, outside air or recovered process heat. In this paper, we present a comprehensive review of the research and application of active hollow core slabs in building systems for utilizing low energy sources. The principle and development of active hollow core slabs in building systems for leveling the indoor temperature fluctuation by ventilation air passing the cores are described. Calculation models of the active hollow core concrete slab as well as the practical applications and performance evaluation of the slab applied in building systems for air

Mathematical phantoms for evaluation of age-specific internal dose

International Nuclear Information System (INIS)

Cristy, M.

1980-01-01

A series of mathematical phantoms representing children has been developed for use with photon transport codes. These phantoms, patterned after the Fisher-Snyder adult phantom, consist of simple mathematical expressions for the boundaries of the major organs and body sections. The location and shape of the organs are consistent with drawings depicting developmental anatomy, with the organ volumes assigned such that the masses at the various ages conform closely with the data presented in Reference Man. The explicit mathematical expressions for the various ages overcome the potential misrepresentation of organ sizes that occurred in phantoms derived from simple mathematical transformations of the adult phantom. Female breast tissue has been added to the phantoms, including the adult, now allowing assessment of doses to this organ

Quality of Slab Track Construction – Track Alignment Design and Track Geometry

Directory of Open Access Journals (Sweden)

Šestáková Janka

2015-05-01

Full Text Available The slab track superstructure design (without ballast is a perspective construction especially for building tunnels and bridges in the modernized sections of railway tracks in Slovakia. Monitoring of the structure described in this article is focused on the transition areas between standard structure with ballast and slab track construction.

Resonance-enhanced optical forces between coupled photonic crystal slabs.

Science.gov (United States)

Liu, Victor; Povinelli, Michelle; Fan, Shanhui

2009-11-23

The behaviors of lateral and normal optical forces between coupled photonic crystal slabs are analyzed. We show that the optical force is periodic with displacement, resulting in stable and unstable equilibrium positions. Moreover, the forces are strongly enhanced by guided resonances of the coupled slabs. Such enhancement is particularly prominent near dark states of the system, and the enhancement effect is strongly dependent on the types of guided resonances involved. These structures lead to enhancement of light-induced pressure over larger areas, in a configuration that is directly accessible to externally incident, free-space optical beams.

Composite slab behavior and strength analysis under static and dynamic loads

Directory of Open Access Journals (Sweden)

Florin Radu HARIGA

2012-07-01

Full Text Available Steel-framed buildings are typically constructed using steel-deck-reinforced concrete floor slabs. The in-plane (or diaphragm strength and stiffness of the floor system are frequently utilized in the lateral load-resisting system design. This paper presents the results of an experimental research program in which four full size composite diaphragms were vertically loaded to the limit state, under static or dynamic loads. Two test specimens were provided with longitudinal steel-deck ribs, and the other two specimens with cross steel-deck ribs. Typical composite diaphragm limit states are described, and the controlling limit state for each of the full size tests is indicated. The interaction effects between the reinforced concrete slab and the steel girder on the composite slab strength and stiffness were mainly studied.

Usefulness of a functional tracheobronchial phantom for interventional procedure

International Nuclear Information System (INIS)

Kim, Tae Hyung; Lim, Cheong Hwan; Kim, Jeong Koo

2003-01-01

To evaluate usefulness of a functional tracheobronchial phantom for interventional procedure. The functional phantom was made as a actual size with human normal anatomy used silicone and a paper clay mold. A tracheobronchial-shape clay mold was placed inside a square box and liquid silicone was poured. After the silicone was formed, the clay was removed. We measured film density and tracheobronchial angle at the human, animal and phantom respectively. The film density of trachea part were 0.76 (± 0.011) in human, 0.97 (± 0.015) in animal, 0.45 (± 0.016) in phantom. The tracheobronchial bifurcation part measured 0.51 (± 0.006) in human, 0.65 (± 0.005) in animal, 0.65 (± 0.008) in phantom. The right bronchus part measured 0.14 (± 0.008) in human, 0.59 (± 0.014) in animal and 0.04 (± 0.007) in phantom. The left bronchus were 0.54 (± 0.004) in human, 0.54 (± 0.008) in animal and 0.08 (± 0.008) in phantom. At the stent part were 0.54 (± 0.004) in human, 0.59 (± 0.011) in animal and 0.04 (± 0.007) in phantom, respectively. The tracheobronchial angle of the left bronchus site were 42.6 (± 2.07).deg. in human, 43.4 (± 2.40).deg. in animal and 35 (± 2.00).deg. in phantom, respectively. The right bronchus site were 32.8 (± 2.77).deg. in human, 34.6 (± 1.94).deg. in animal and 50.2 (± 1.30).deg. in phantom, respectively. The phantom was useful for in-vitro testing of tracheobronchial interventional procedure, since it was easy to reproduce

Collision-induced light scattering in a thin xenon layer between graphite slabs - MD study.

Science.gov (United States)

Dawid, A; Górny, K; Wojcieszyk, D; Dendzik, Z; Gburski, Z

2014-08-14

The collision-induced light scattering many-body correlation functions and their spectra in thin xenon layer located between two parallel graphite slabs have been investigated by molecular dynamics computer simulations. The results have been obtained at three different distances (densities) between graphite slabs. Our simulations show the increased intensity of the interaction-induced light scattering spectra at low frequencies for xenon atoms in confined space, in comparison to the bulk xenon sample. Moreover, we show substantial dependence of the interaction-induced light scattering correlation functions of xenon on the distances between graphite slabs. The dynamics of xenon atoms in a confined space was also investigated by calculating the mean square displacement functions and related diffusion coefficients. The structural property of confined xenon layer was studied by calculating the density profile, perpendicular to the graphite slabs. Building of a fluid phase of xenon in the innermost part of the slot was observed. The nonlinear dependence of xenon diffusion coefficient on the separation distance between graphite slabs has been found. Copyright © 2014. Published by Elsevier B.V.

Quality factor enhancement in photonic crystal slabs by manipulation of the ring of exceptional points

DEFF Research Database (Denmark)

Kaminski, Piotr Marek; Taghizadeh, Alireza; Breinbjerg, Olav

2017-01-01

Presently, we investigate the influence of the extent of a ring of exceptional points on the Q-factor of three-dimensional photonic crystal slabs. By changing the thickness of the slab, the extent of the ring of exceptional points is varied, allowing us to recover the Dirac cones in open, non......-Hermitian systems. In this case, three bound states in the continuum are exhibited close to the Gamma-point. For an optimized thickness of the slab, the associated Q-factors are found to grow rapidly with the size of the slab. The present results may lead to novel, small area and high Q-factor photonic crystal...

Comparison of effective doses using tissue-weighting factors in the 1977, 1990, and 2007 recommendations of the ICRP

International Nuclear Information System (INIS)

Matsunaga, Yuta; Kawaguchi, Ai; Suzuki, Shoichi

2013-01-01

The International Commission on Radiological Protection (ICRP) has established recommended tissue-weighting factors. Although there have been international reports on effective doses using the factors listed in the 1977, 1990, and 2007 recommendations of the ICRP, there have been no papers in Japan. The aim of this study was to evaluate effective doses using the tissue-weighting factors listed in each recommendation of the ICRP under 2011 exposure conditions in Japan. We used a human body phantom to estimate patient exposure doses during chest, abdomen, lumbar spine (anteroposterior and lateral), and head radiographs. With thermoluminescence dosimeters placed at various positions on and in the phantom, radiation doses were determined. There was little change in the effective doses to the chest and head from each recommendation. However, the effective doses recommended in 1977 were 0.2 mSv to the abdomen, 0.1 mSv to the lumbar spine anteroposteriorally, and 0.1 mSv to the lumbar spine laterally; these values are lower than those recommended in 1990 and 2007, which were 0.5 mSv to the abdomen, 0.4 mSv to the lumbar spine anteroposteriorally, and 0.6 mSv to the lumbar spine laterally. We could evaluate the effective doses using each recommendation and 2011 exposure conditions in Japan. (author)

Using thermal and compositional modeling to assess the role of water in Alaskan flat slab subduction

Science.gov (United States)

Robinson, S. E.; Porter, R. C.; Hoisch, T. D.

2017-12-01

Although plate tectonic theory is well established in the geosciences, the mechanisms and details of various plate-tectonics related phenomena are not always well understood. In some ( 10%) convergent plate boundaries, subduction of downgoing oceanic plates is characterized by low angle geometries and is termed "flat slab subduction." The mechanism(s) driving this form of subduction are not well understood. The goal of this study is to explore the role that water plays in these flat slab subduction settings. This is important for a better understanding of the behavior of these systems and for assessing volcanic hazards associated with subduction and slab rollback. In southern Alaska, the Pacific Plate is subducting beneath the North American plate at a shallow angle. This low-angle subduction within the region is often attributed to the subduction of the Yakutat block, a terrane accreting to the south-central coast of Alaska. This flat slab region is bounded by the Aleution arc to the west and the strike-slip Queen Charlotte fault to the east. Temperature and compositional models for a 500-km transect across this subduction zone in Alaska were run for ten million years (the length of time that flat slab subduction has been ongoing in Alaska) and allow for interpretation of present-day conditions at depth. This allows for an evaluation of two hypotheses regarding the role of water in flat-slab regions: (1) slab hydration and dehydration help control slab buoyancy which influences whether flat slab subduction will be maintained or ended. (2) slab hydration/dehydration of the overlying lithosphere impacts deformation within the upper plate as water encourages plate deformation. Preliminary results from thermal modeling using Thermod8 show that cooling of the mantle to 500 °C is predicted down to 100 km depth at 10 million years after the onset of low-angle subduction (representing present-day). Results from compositional modeling in Perple_X show the maximum amount

Surface behaviour of the pairing gap in a slab of nuclear matter

International Nuclear Information System (INIS)

Baldo, M.; Farine, M.; Lombardo, U.; Saperstein, E.E.; Zverev, M.V.; Schuck, P.

2003-01-01

The surface behavior of the pairing gap previously studied for semi-infinite nuclear matter is analyzed in the slab geometry. The gap-shape function is calculated in two cases: a) pairing with the Gogny force in a hard-wall potential and b) pairing with the separable Paris interaction in a Saxon-Woods mean-field potential. It is shown that the surface features are preserved in the case of slab geometry, being almost independent of the width of the slab. It is also demonstrated that the surface enhancement is strengthened as the absolute value of chemical potential vertical stroke μvertical stroke decreases which simulates the approach to the nucleon drip line. (orig.)

Energy penalties associated with the use of a sub-slab depressurization system

International Nuclear Information System (INIS)

Clarkin, M.; Brennan, T.; Osborne, M.C.

1990-01-01

One of the primary radon mitigation techniques used to reduce indoor radon concentrations in houses is a sub-slab depressurization system. In this type of system, a fan removes soil gases containing radon from beneath the floor slab and exhausts the gases to the outdoors by creating a pressure field beneath the slab that is negative relative to the basement air pressure. Because of this negative pressure, indoor conditioned air can be drawn through the floor penetrations and exhausted outdoors. In order to determine the amount of conditioned air that is being lost, a series of experiments utilizing tracer gases were performed in three houses. This paper presents the results of these experiments

Reproducibility of phantom-based quality assurance parameters in real-time ultrasound imaging.

Science.gov (United States)

Sipilä, Outi; Blomqvist, Päivi; Jauhiainen, Mervi; Kilpeläinen, Tiina; Malaska, Paula; Mannila, Vilma; Vinnurva-Jussila, Tuula; Virsula, Sari

2011-07-01

In a large radiological center, the ultrasound (US) quality assurance (QA) program involves several professionals. Although the operator and the parameters utilized can contribute to the results, the selected QA parameters should still reflect the quality of the US scanner, not the measuring process. To evaluate the reproducibility of recommended phantom-based US QA parameters in a realistic environment. Six sonographers measured six high-end US scanners with 20 transducers using a general purpose phantom. Every transducer was measured altogether seven times, using one frequency per transducer. The QA parameters studied were homogeneity, visualization depth, vertical and horizontal distance measurements, axial and lateral resolution, and the correct visibility of anechoic and high-contrast masses. The evaluation of the homogeneity was based on visual observations. Inter-observer interquartile ranges were computed for the grading of the masses. For the other QA parameters, the mean inter- and intra-observer coefficients of variation (CoV) were calculated. In addition, the symmetry of the reverberations when imaging air with a clean transducer was checked. The mean inter-observer CoVs were: visualization depth 11 ± 4%, vertical distance 1.7 ± 0.4%, horizontal distance 1.4 ± 0.6%, axial resolution 22 ± 7%, and lateral resolution 16 ± 8%. The mean intra-observer values were about half of these values with similar standard deviations. The visual evaluation of the homogeneity and the symmetry of the reverberations produced false-positive findings in 5% of the cases, but were found useful in detecting a defective transducer. The grading of the masses had mean interquartile ranges of 20-30% of the grading scale. The inter-observer variability in measuring phantom-based QA parameters can be relatively high. This should be considered when implementing a phantom-based QA protocol and evaluating the results.

Evaluation of effective dose in an anthropomorphic phantom in radiological emergencies situations

International Nuclear Information System (INIS)

Silva, Livia K. da; Ribeiro, Rosane M.; Santos, Denison de S.

2013-01-01

This work aims to implement the code of Monte Carlo Geant4 in a male and female phantom, ADAM and EVA, to be able to evaluate the dose in individuals who have been exposed externally to ionizing radiation sources so that in the future be made a review within the limits of validity of the terms contained in TECDOC-1162, published by the International Atomic Energy Agency (IAEA), which recommends formulas for the effective dose assessment in individuals who have been exposed to external radiation sources in various geometric configurations and for various radionuclides

Integral equation solution for truncated slab structures by using a fringe current formulation

DEFF Research Database (Denmark)

Jørgensen, Erik; Toccafondi, A.; Maci, S.

1999-01-01

Full-wave solutions of truncated dielectric slab problems are interesting for a variety of engineering applications, in particular patch antennas on finite ground planes. For this application a canonical reference solution is that of a semi-infinite slab illuminated by a line source. Standard int...

Near-field imaging of out-of-plane light scattering in photonic crystal slabs

DEFF Research Database (Denmark)

Volkov, Valentyn; Bozhevolnyi, Sergey; Taillaert, Dirk

2003-01-01

A collection scanning near-field optical microscope (SNOM) is used to image the propagating of light at telecommunication wavelengths (1520-1570 nm) along photonic crystal (PC) slabs, which combine slab waveguides with in-plane PCs consisting of one- and two-dimensional gratings. The efficient out...

Analytical model for shear strength of end slabs of prestressed concrete nuclear reactor vessels

International Nuclear Information System (INIS)

Abdulrahman, H.O.; Sozen, M.A.; Schnobrich, W.C.

1979-04-01

The results are presented of an investigation of the behavior and strength of flat end slabs of cylindrical prestressed concrete nuclear reactor vessels. The investigation included tests of ten small-scale pressure vessels and development of a nonlinear finite-element model to simulate the deformation response and strength of the end slabs. Because earlier experimental studies had shown that the flexural strength of the end slab could be calculated using intelligible procedures, the emphasis of this investigation was on shear strength

Phantom Pain

Science.gov (United States)

... Because this is yet another version of tangled sensory wires, the result can be pain. A number of other factors are believed to contribute to phantom pain, including damaged nerve endings, scar tissue at the site of the amputation and the physical memory of pre-amputation pain in the affected area. ...

Response of CR-39 based personnel neutron dosemeter in terms of directional dose equivalent, in free air and on phantom

International Nuclear Information System (INIS)

Pal, Rupali R.; Sathian, Deepa; Jayalakshmi, V.; Chougaonkar, M.P.

2011-01-01

CR-39 is the most sensitive of nuclear track detectors for protons and is recommended as an effective neutron dosimeter because of it's low threshold energy of 100 keV neutrons. The fraction of protons that gives detectable tracks in CR-39 depends on the energy of the proton angle of incidence and etching conditions. As a consequence the registration efficiency of neutrons in the CR-39 plastics used for neutron personnel monitoring is strongly influenced by the direction of radiation incidence. This paper presents the relative response of CR-39 at varying neutron incident angles, for 241 Am-Be neutron source spectra in free air and on ISO phantom, in terms of operational quantities. It is observed that the angular dependence of CR-39 for irradiations in air and on phantom is essentially the same indicating that the phantom does not affect the directional response of CR-39. (author)

Alternative and cost-effective bridge approach slabs.

Science.gov (United States)

2010-10-01

The primary objectives of the proposed project are to investigate the causes for any bumps at the end of the bridge approach slab : and to develop remedial measures or alternative designs for a replacement. It is clear that the problem stems from geo...

Design of energy efficient building with radiant slab cooling

Science.gov (United States)

Tian, Zhen

2007-12-01

Air-conditioning comprises a substantial fraction of commercial building energy use because of compressor-driven refrigeration and fan-driven air circulation. Core regions of large buildings require year-round cooling due to heat gains from people, lights and equipment. Negative environmental impacts include CO2 emissions from electric generation and leakage of ozone-depleting refrigerants. Some argue that radiant cooling simultaneously improves building efficiency and occupant thermal comfort, and that current thermal comfort models fail to reflect occupant experience with radiant thermal control systems. There is little field evidence to test these claims. The University of Calgary's Information and Communications Technology (ICT) Building, is a pioneering radiant slab cooling installation in North America. Thermal comfort and energy performance were evaluated. Measurements included: (1) heating and cooling energy use, (2) electrical energy use for lighting and equipment, and (3) indoor temperatures. Accuracy of a whole building energy simulation model was evaluated with these data. Simulation was then used to compare the radiant slab design with a conventional (variable air volume) system. The radiant system energy performance was found to be poorer mainly due to: (1) simultaneous cooling by the slab and heating by other systems, (2) omission of low-exergy (e.g., groundwater) cooling possible with the high cooling water temperatures possible with radiant slabs and (3) excessive solar gain and conductive heat loss due to the wall and fenestration design. Occupant thermal comfort was evaluated through questionnaires and concurrent measurement of workstation comfort parameters. Analysis of 116 sets of data from 82 occupants showed that occupant assessment was consistent with estimates based on current thermal comfort models. The main thermal comfort improvements were reductions in (1) local discomfort from draft and (2) vertical air temperature stratification. The

Strong suppression of radiation states in a slab waveguide sandwiched between omnidirectional mirrors

NARCIS (Netherlands)

Hoekstra, Hugo; Yudistira, D.; Stoffer, Remco

2005-01-01

Structures in channel or slab waveguides, applied deliberately or due to imperfections, may lead to strong modal losses, corresponding to the excitation of radiation modes. As an example, losses are generally very large in slab photonic crystal (PhC) impurity waveguides (WGs) due to the combined

Experimental IMRT breast dosimetry in a thorax phantom

International Nuclear Information System (INIS)

Pimenta, Elsa B.; Campos, Tarcisio P.R.; Nogueira, Luciana B.; Lima, Andre C.S.

2017-01-01

Radiation therapy (RT) is an essential therapeutic method. RT is often used as adjuvant therapy in the treatment of breast cancer. The dose-volume restrictions of the organs at risk limit the prescribed dose to the target volume and biological and clinical effects may influence the final treatment outcome. The breast RT provides large risks to the adjacent organs and consequently the recommended dosimetry to the prescribed dose volume (PTV) is 50 Gy, lower than the most prescribed dose in other treatments (70-85 Gy). Such values implies in less tumor control compared to other sites. The present research proposal aimed to measure absorbed dose in a thorax phantom with synthetic breasts provided by an Intensity-Modulate Radiation Therapy (IMRT) protocol in a RT center. On the methodology, IMRT protocol was selected following recommendations from the Radiation Therapy Oncology Group (RTOG). Radiochromic films and a thorax simulator were prepared by the Ionizing Radiation Research Group (NRI). Dosimeters were calibrated on a selected linear accelerator (LINAC). The comparison of the dosimetry from treatment planning system (TPS), Xio (Elekta) and from experimental data was performed. The spatial distribution of the breast internal dose and in the adjacent organs was depicted by the experimental data. In the film's calibration, the quadratic polynomial fit presented a satisfactory coefficient. Two-dimensional dose profiles were obtained in the breast suggesting that films can supply details and information that TPS does not provide. At the phantom's dosimetry, the internal mean doses taken at the synthetic breast presented usual values above the prescribed dose, besides overall values were within the dosimetric MSKCC criterion. The non full reproduction of the build-up region in the films had occurred due to the asymmetrical positioning of the films in the inner breast, in addition to their non constant distance from the skin. The hot regions were present may be due to

Effect of reflecting modes on combined heat transfer within an anisotropic scattering slab

International Nuclear Information System (INIS)

Yi Hongliang; Tan Heping; Lu Yiping

2005-01-01

Under various interface reflecting modes, different transient thermal responses will occur in the media. Combined radiative-conductive heat transfer is investigated within a participating, anisotropic scattering gray planar slab. The two interfaces of the slab are considered to be diffuse and semitransparent. Using the ray tracing method, an anisotropic scattering radiative transfer model for diffuse reflection at boundaries is set up, and with the help of direct radiative transfer coefficients, corresponding radiative transfer coefficients (RTCs) are deduced. RTCs are used to calculate the radiative source term in energy equation. Transient energy equation is solved by the full implicit control-volume method under the external radiative-convective boundary conditions. The influences of two reflecting modes including both specular reflection and diffuse reflection on transient temperature fields and steady heat flux are examined. According to numerical results obtained in this paper, it is found that there exits great difference in thermal behavior between slabs with diffuse interfaces and that with specular interfaces for slabs with big refractive index

Propagation Properties of Airy Beam through Periodic Slab System with Negative Index Materials

Directory of Open Access Journals (Sweden)

Long Jin

2018-01-01

Full Text Available Based on light transfer matrix and electric field vector equation, the evolution of Airy beam propagating in periodic slab system with three negative index materials (NIMs and its transmission mechanism are investigated. The intensity profiles on emergent surface of periodic slab system and side view of Airy beam propagating in each right handed material (RHM and double negative material (DNM unit including lossless and losses DNMs are discussed. It is revealed that the self-recovery Airy beam can be achieved in long distance by using lossless periodic slab system as long as the negative refractive index nl=-nr and each unit length L=Z. As to losses slab system contained DNMs, the smaller the collision frequencies are, the better the Airy beam quality is formed. It is expected that the proposed manner of beam transmission and corresponding conclusions can be useful for extension applications of optical control, especially for optical communication and optical encryption technique.

All-polymer photonic crystal slab sensor

DEFF Research Database (Denmark)

Hermannsson, Pétur Gordon; Sørensen, Kristian Tølbøl; Vannahme, Christoph

2015-01-01

An all-polymer photonic crystal slab sensor is presented, and shown to exhibit narrow resonant reflection with a FWHM of less than 1 nm and a sensitivity of 31 nm/RIU when sensing media with refractive indices around that of water. This results in a detection limit of 4.5x10-6 RIU when measured...

Geometrical optics of dense aerosols: forming dense plasma slabs.

Science.gov (United States)

Hay, Michael J; Valeo, Ernest J; Fisch, Nathaniel J

2013-11-01

Assembling a freestanding, sharp-edged slab of homogeneous material that is much denser than gas, but much more rarefied than a solid, is an outstanding technological challenge. The solution may lie in focusing a dense aerosol to assume this geometry. However, whereas the geometrical optics of dilute aerosols is a well-developed field, the dense aerosol limit is mostly unexplored. Yet controlling the geometrical optics of dense aerosols is necessary in preparing such a material slab. Focusing dense aerosols is shown here to be possible, but the finite particle density reduces the effective Stokes number of the flow, a critical result for controlled focusing.

An eye model for computational dosimetry using a multi-scale voxel phantom

International Nuclear Information System (INIS)

Caracappa, P.F.; Rhodes, A.; Fiedler, D.

2013-01-01

The lens of the eye is a radiosensitive tissue with cataract formation being the major concern. Recently reduced recommended dose limits to the lens of the eye have made understanding the dose to this tissue of increased importance. Due to memory limitations, the voxel resolution of computational phantoms used for radiation dose calculations is too large to accurately represent the dimensions of the eye. A revised eye model is constructed using physiological data for the dimensions of radiosensitive tissues, and is then transformed into a high-resolution voxel model. This eye model is combined with an existing set of whole body models to form a multi-scale voxel phantom, which is used with the MCNPX code to calculate radiation dose from various exposure types. This phantom provides an accurate representation of the radiation transport through the structures of the eye. Two alternate methods of including a high-resolution eye model within an existing whole body model are developed. When the Lattice Overlay method, the simpler of the two to define, is utilized, the computational penalty in terms of speed is noticeable and the figure of merit for the eye dose tally decreases by as much as a factor of two. When the Voxel Substitution method is applied, the penalty in speed is nearly trivial and the impact on the tally figure of merit is comparatively smaller. The origin of this difference in the code behavior may warrant further investigation

The exact solution of a three-dimensional lattice polymer confined in a slab with sticky walls

Energy Technology Data Exchange (ETDEWEB)

Brak, R; Iliev, G K; Owczarek, A L [Department of Mathematics and Statistics, University of Melbourne, Parkville, Vic 3010 (Australia); Whittington, S G [Department of Chemistry, University of Toronto, Toronto M5S 3H6 (Canada)

2010-04-02

We present the exact solution of a three-dimensional lattice model of a polymer confined between two sticky walls, that is within a slab. We demonstrate that the model behaves in a similar way to its two-dimensional analogues and agrees with Monte Carlo evidence based upon simulations of self-avoiding walks in slabs. The model on which we focus is a variant of the partially directed walk model on the cubic lattice. We consider both the phase diagram of relatively long polymers in a macroscopic slab and the effective force of the polymer on the walls of the slab.

Energy Efficient Resource Allocation for Phantom Cellular Networks

KAUST Repository

Abdelhady, Amr

2016-04-01

Multi-tier heterogeneous networks have become an essential constituent for next generation cellular networks. Meanwhile, energy efficiency (EE) has been considered a critical design criterion along with the traditional spectral efficiency (SE) metric. In this context, we study power and spectrum allocation for the recently proposed two-tier network architecture known as phantom cellular networks. The optimization framework includes both EE and SE. First, we consider sparsely deployed cells experiencing negligible interference and assume perfect channel state information (CSI). For this setting, we propose an algorithm that finds the SE and EE resource allocation strategies. Then, we compare the performance of both design strategies versus number of users, and phantom cells share of the total available resource units (RUs). We aim to investigate the effect of some system parameters to achieve improved SE performance at a non-significant loss in EE performance, or vice versa. It is found that increasing phantom cells share of RUs decreases the SE performance loss due to EE optimization when compared with the optimized SE performance. Second, we consider the densely deployed phantom cellular networks and model the EE optimization problem having into consideration the inevitable interference and imperfect channel estimation. To this end, we propose three resource allocation strategies aiming at optimizing the EE performance metric of this network. Furthermore, we investigate the effect of changing some of the system parameters on the performance of the proposed strategies, such as phantom cells share of RUs, number of deployed phantom cells within a macro cell coverage, number of pilots and the maximum power available for transmission by the phantom cells BSs. It is found that increasing the number of pilots deteriorates the EE performance of the whole setup, while increasing maximum power available for phantom cells transmissions reduces the EE of the whole setup in a

[Psychotherapies for the Treatment of Phantom Limb Pain].

Science.gov (United States)

Cárdenas, Katherine; Aranda, Mariana

The phantom limb pain has been described as a condition in which patients experience a feeling of itching, spasm or pain in a limb or body part that has been previously amputated. Such pain can be induced by a conflict between the representation of the visual and proprioceptive feedback of the previously healthy limb. The phantom limb pain occurs in at least 42 to 90% of amputees. Regular drug treatment of phantom limb pain is almost never effective. A systematic review of the literature was conducted in Medline and Cochrane using the MESH terms "phantom limb pain" and "psychotherapy", published in the last 10 years, in English and Spanish, finding 49 items. After reviewing the abstracts, 25 articles were excluded for not being related to the objective of the research. Additionally cross references of included articles and literature were reviewed. To describe the psychotherapies used in the management of phantom limb pain, their effectiveness and clinical application reported in the literature. The mechanisms underlying phantom limb pain were initially explained, as were the published studies on the usefulness of some psychotherapies such as mirror visual feedback and immersive virtual reality, visual imagery, desensitization and reprocessing eye movements and hypnosis. The phantom limb pain is a complex syndrome that requires pharmacological and psychotherapeutic intervention. The psychotherapies that have been used the most as adjuvants in the treatment of phantom limb pain are mirror visual feedback, desensitization and reprocessing eye movements, imagery and hypnosis. Studies with more representative samples, specifically randomized trials are required. Copyright © 2016 Asociación Colombiana de Psiquiatría. Publicado por Elsevier España. All rights reserved.

Suspended HfO2 photonic crystal slab on III-nitride/Si platform

International Nuclear Information System (INIS)

Wang, Yongjin; Feng, Jiao; Cao, Ziping; Zhu, Hongbo

2014-01-01

We present here the fabrication of suspended hafnium oxide (HfO 2 ) photonic crystal slab on a III-nitride/Si platform. The calculations are performed to model the suspended HfO 2 photonic crystal slab. Aluminum nitride (AlN) film is employed as the sacrificial layer to form air gap. Photonic crystal patterns are defined by electron beam lithography and transferred into HfO 2 film, and suspended HfO 2 photonic crystal slab is achieved on a III-nitride/Si platform through wet-etching of AlN layer in the alkaline solution. The method is promising for the fabrication of suspended HfO 2 nanostructures incorporating into a III-nitride/Si platform, or acting as the template for epitaxial growth of III-nitride materials. (orig.)

Wet plume atop of the flattening slab: Insight into intraplate volcanism in East Asia

Science.gov (United States)

He, Lijuan

2017-08-01

Geophysical observations imply the intraplate volcanism in East Asia is related to dehydration of slab stagnating in the transition zone. To better understand the dynamics of such process, a thermochemical mantle convection model is constructed to simulate numerically the thermal evolution of slab and the transportation of water in the process of slab downgoing, flattening and stagnation. Equation of water transfer is included, and water effects on density and viscosity are considered. Model results indicate the warming of slab by surrounding mantle is rather slow. Water could be successfully dragged into the transition zone if the reference viscosity of the hydrous layer (with initial water of 2 wt%) is higher than 1017 Pa s and that of mantle is 1021 Pa s. Wet plumes could then originate in the flat-lying part of the slab, relatively far from the trench. Generally, the viscosity of the hydrous layer governs the initiation of wet plume, whereas the viscosity of the overlying mantle wedge controls the activity of the ascending wet plumes - they are more active in the weaker wedge. The complex fluid flow superposed by corner flow and free thermal convection influences greatly the water transport pattern in the upper mantle. Modeling results together with previous modeling infer three stages of water circulation in the big mantle wedge: 1) water is brought into the mantle transition zone by downward subducting slab under some specific thermo-rheological conditions, otherwise water is released at shallow depth near wedge tip; 2) wet plume generates from surface of the flattening slab warmed by surrounding mantle, and 3) water spreads over the big mantle wedge. Wet plume from the flattening Pacific Plate arrives at the lithospheric base and induces melting, which can explain the intraplate Cenozoic volcanoes in East Asia.

Exact exchange plane-wave-pseudopotential calculations for slabs: Extending the width of the vacuum

Science.gov (United States)

Engel, Eberhard

2018-04-01

Standard plane-wave pseudopotential (PWPP) calculations for slabs such as graphene become extremely demanding, as soon as the exact exchange (EXX) of density functional theory is applied. Even if the Krieger-Li-Iafrate (KLI) approximation for the EXX potential is utilized, such EXX-PWPP calculations suffer from the fact that an accurate representation of the occupied states throughout the complete vacuum between the replicas of the slab is required. In this contribution, a robust and efficient extension scheme for the PWPP states is introduced, which ensures the correct exponential decay of the slab states in the vacuum for standard cutoff energies and therefore facilitates EXX-PWPP calculations for very wide vacua and rather thick slabs. Using this scheme, it is explicitly verified that the Slater component of the EXX/KLI potential decays as -1 /z over an extended region sufficiently far from the surface (assumed to be perpendicular to the z direction) and from the middle of the vacuum, thus reproducing the asymptotic behavior of the exact EXX potential of a single slab. The calculations also reveal that the orbital-shift component of the EXX/KLI potential is quite sizable in the asymptotic region. In spite of the long-range exchange potential, the replicas of the slab decouple rather quickly with increasing width of the vacuum. Relying on the identity of the work function with the Fermi energy obtained with a suitably normalized total potential, the present EXX/KLI calculations predict work functions for both graphene and the Si(111) surface which are substantially larger than the corresponding experimental data. Together with the size of the orbital-shift potential in the asymptotic region, the very large EXX/KLI work functions indicate a failure of the KLI approximation for nonmetallic slabs.

Primary motor cortex changes after amputation correlate with phantom limb pain and the ability to move the phantom limb

DEFF Research Database (Denmark)

Raffin, Estelle; Richard, Nathalie; Giraux, Pascal

2016-01-01

A substantial body of evidence documents massive reorganization of primary sensory and motor cortices following hand amputation, the extent of which is correlated with phantom limb pain. Many therapies for phantom limb pain are based upon the idea that plastic changes after amputation...... for the maladaptative plasticity model, we demonstrate for the first time that motor capacities of the phantom limb correlate with post-amputation reorganization, and that this reorganization is not limited to the face and hand representations but also includes the proximal upper-limb....

Studies of imaging characteristics for a slab of a lossy left-handed material

International Nuclear Information System (INIS)

Shen Linfang; He Sailing

2003-01-01

The characteristics of an imaging system formed by a slab of a lossy left-handed material (LHM) are studied. The transfer function of the LHM imaging system is written in an appropriate product form with each term having a clear physical interpretation. A tiny loss of the LHM may suppress the transmission of evanescent waves through the LHM slab and this is explained physically. An analytical expression for the resolution of the imaging system is derived. It is shown that it is impossible to make a subwavelength imaging by using a realistic LHM imaging system unless the LHM slab is much thinner than the wavelength

MEMBRANE ACTION IN PROFILED STEEL SHEETING DRY BOARD (PSSDB FLOOR SLAB SYSTEM

Directory of Open Access Journals (Sweden)

MAHMOOD SERAJI

2013-02-01

Full Text Available Profiled steel sheeting dry board (PSSDB system is a lightweight composite structural system that made of the profiled steel sheeting (PSS connected to the dry board (DB by self-drilling and self-tapping screws. The objective of this paper is to study the effect of membrane action in improving the flexural capacities of the PSSDB system. According to the literatures, common failure of the PSSDB floor is due to local buckling in the top flanges of steel sheeting at the centre of a simply supported slab. Restraining the horizontal movement at supports may develop the membrane action (MA in the slab that can remarkably enhance the flexural rigidities of the floor. Experimental tests were conducted along with developing nonlinear finite element model to explore the effect of MA in the PSSDB floor. Experimental results of the PSSDB panel with simply end support were exploited to verify the nonlinear finite element results. The developed finite element model was then modified by restraining the horizontal movement of the slab at the supports. The obtained results disclosed that the developed compressive membrane action enhanced the stiffness of the slab at serviceability load by about 240%.

A dynamic model for slab development associated with the 2015 Mw 7.9 Bonin Islands deep earthquak

Science.gov (United States)

Zhan, Z.; Yang, T.; Gurnis, M.

2016-12-01

The 680 km deep May 30, 2015 Mw 7.9 Bonin Islands earthquake is isolated from the nearest earthquakes by more than 150 km. The geodynamic context leading to this isolated deep event is unclear. Tomographic models and seismicity indicate that the morphology of the west-dipping Pacific slab changes rapidly along the strike of the Izu-Bonin-Mariana trench. To the north, the Izu-Bonin section of the Pacific slab lies horizontally above the 660 km discontinuity and extends more than 500 km westward. Several degrees south, the Mariana section dips vertically and penetrates directly into the lower mantle. The observed slab morphology is consistent with plate reconstructions suggesting that the northern section of the IBM trench retreated rapidly since the late Eocene while the southern section of the IBM trench was relatively stable during the same period. We suggest that the location of the isolated 2015 Bonin Islands deep earthquake can be explained by the buckling of the Pacific slab beneath the Bonin Islands. We use geodynamic models to investigate the slab morphology, temperature and stress regimes under different trench motion histories. Models confirm previous results that the slab often lies horizontally within the transition zone when the trench retreats, but buckles when the trench position becomes fixed with respect to the lower mantle. We show that a slab-buckling model is consistent with the observed deep earthquake P-axis directions (assumed to be the axis of principal compressional stress) regionally. The influences of various physical parameters on slab morphology, temperature and stress regime are investigated. In the models investigated, the horizontal width of the buckled slab is no more than 400 km.

The UF family of reference hybrid phantoms for computational radiation dosimetry

International Nuclear Information System (INIS)

Lee, Choonsik; Lodwick, Daniel; Hurtado, Jorge; Pafundi, Deanna; Williams, Jonathan L; Bolch, Wesley E

2010-01-01

Computational human phantoms are computer models used to obtain dose distributions within the human body exposed to internal or external radiation sources. In addition, they are increasingly used to develop detector efficiencies for in vivo whole-body counters. Two classes of computational human phantoms have been widely utilized for dosimetry calculation: stylized and voxel phantoms that describe human anatomy through mathematical surface equations and 3D voxel matrices, respectively. Stylized phantoms are flexible in that changes to organ position and shape are possible given avoidance of region overlap, while voxel phantoms are typically fixed to a given patient anatomy, yet can be proportionally scaled to match individuals of larger or smaller stature, but of equivalent organ anatomy. Voxel phantoms provide much better anatomical realism as compared to stylized phantoms which are intrinsically limited by mathematical surface equations. To address the drawbacks of these phantoms, hybrid phantoms based on non-uniform rational B-spline (NURBS) surfaces have been introduced wherein anthropomorphic flexibility and anatomic realism are both preserved. Researchers at the University of Florida have introduced a series of hybrid phantoms representing the ICRP Publication 89 reference newborn, 15 year, and adult male and female. In this study, six additional phantoms are added to the UF family of hybrid phantoms-those of the reference 1 year, 5 year and 10 year child. Head and torso CT images of patients whose ages were close to the targeted ages were obtained under approved protocols. Major organs and tissues were segmented from these images using an image processing software, 3D-DOCTOR(TM). NURBS and polygon mesh surfaces were then used to model individual organs and tissues after importing the segmented organ models to the 3D NURBS modeling software, Rhinoceros(TM). The phantoms were matched to four reference datasets: (1) standard anthropometric data, (2) reference

Development of thyroid anthropomorphic phantoms for use in nuclear medicine

International Nuclear Information System (INIS)

Cerqueira, R.A.D.; Maia, A.F.

2014-01-01

The objective of this study was to develop thyroid anthropomorphic phantoms to be used in control tests of medical images in scintillation cameras. The main difference among the phantoms was the neck shape: in the first, called OSCT, it was geometrically shaped, while in the second, called OSAP, it was anthropomorphically shaped. In both phantoms, thyroid gland prototypes, which were made of acrylic and anthropomorphically shaped, were constructed to allow the simulation of a healthy thyroid and of thyroids with hyperthyroidism and hypothyroidism. Images of these thyroid anthropomorphic phantoms were obtained using iodine 131 with an activity of 8.695 MBq. The iodine 131 was chosen because it is widely used in studies of thyroid scintigraphy. The images obtained proved the effectiveness of the phantoms to simulate normal or abnormal thyroids function. These phantoms can be used in medical imaging quality control programs and, also in the training of professionals involved in the analysis of images in nuclear medicine centers. - Highlights: ► Two thyroid phantoms were developed (OSCT and OSAP) with different types of acrylics. ► Thyroid glands were represented anthropomorphically in the both phantoms. ► Different prototypes of thyroid were built of simulate healthy or unhealthy glands. ► Images indicate that anthropomorphic phantoms correctly simulate the thyroid gland

Slab Penetration vs. Slab Stagnation: Mantle Reflectors as an Indicator

Science.gov (United States)

Okeler, A.; Gu, Y. J.; Schultz, R.; Contenti, S. M.

2011-12-01

Subducting oceanic lithosphere along convergent margins may stagnate near the base of the upper mantle or penetrate into the lower mantle. These dynamic processes cause extensive thermal and compositional variations, which can be observed in terms of impedance contrast (reflectivity) and topography of mantle transition zone (MTZ) discontinuities, i.e., 410- and 660-km discontinuities. In this study, we utilize ~ 15000 surface-reflected shear waves (SS) and their precursory arrivals (S410S and S660S) to analyze subduction related deformations on mantle reflectivity structure. We apply pre-stack, time-to-depth migration technique to SS precursors, and move weak underside reflections using PREM-predicted travel-time curves. Common Mid-point gathers are formed to investigate structure under the western Pacific, south America, and Mediterranean convergent boundaries. In general, mantle reflectivity structures are consistent with previous seismic tomography models. In regions of slab penetration (e.g., southern Kurile arc, Aegean Sea), our results show 1) a substantial decrease in S660S amplitude, and 2) strong lower mantle reflector(s) at ~ 900 km depth. These reflective structures are supported by zones of high P and S velocities extending into the lower mantle. Our 1-D synthetic simulations suggest that the decreasing S660S amplitudes are, at least partially, associated with shear wave defocusing due to changes in reflector depth (by ±20 km) within averaging bin. Assuming a ~500 km wide averaging area, a dipping reflector with 6-8 % slope can reduce the amplitude of a SS precursor by ~50%. On the other hand, broad depressions with strong impedance contrast at the base of the MTZ characterize the regions of slab stagnation, such as beneath the Tyrrhenian Sea and northeastern China. For the latter region, substantial topography on the 660-km discontinuity west of the Wadati-Benioff zone suggests that the stagnant part of the Pacific plate across Honshu arc is not

3-D Transient Heat Transfer Analysis of Slab Heating Characteristics in a Reheating Furnace in Hot Strip Mills

Science.gov (United States)

Jang, J. Y.; Lee, Y. W.; Lin, C. N.; Wang, C. H.

2016-05-01

A three-dimensional mathematical transient heat transfer model for the prediction of temperature distribution within the slab has been developed by considering the thermal radiation in the walking-beam-type reheating furnace chamber. The steel slabs are heated up through the non-firing, preheating, 1st-heating, 2nd-heating, and soaking zones in the furnace, respectively, where the furnace wall temperature is function of time. Comparison with the in-situ experimental data from Steel Company in Taiwan shows that the present heat transfer model works well for the prediction of thermal behavior of the slab in the reheating furnace. The effects of different skid button height (H=60mm, 90mm, and 120mm) and different gap distance between two slabs (S=50mm, 75mm, and 100mm) on the slab skid mark formation and temperature profiles are investigated. It is found that the skid mark severity decreases with an increase in the skid button height. The effect of gap distance is important only for the slab edge planes, while it is insignificant for the slab central planes.

Agency over Phantom Limb Enhanced by Short-Term Mirror Therapy.

Science.gov (United States)

Imaizumi, Shu; Asai, Tomohisa; Koyama, Shinichi

2017-01-01

Most amputees experience phantom limb, whereby they feel that the amputated limb is still present. In some cases, these experiences include pain that can be alleviated by "mirror therapy." Mirror therapy consists of superimposing a mirrored image of the moving intact limb onto the phantom limb. This therapy provides a closed loop between the motor command to the amputated limb and its predicted visual feedback. This loop is also involved in the sense of agency, a feeling of controlling one's own body. However, it is unclear how mirror therapy is related to the sense of agency over a phantom limb. Using mirror therapy, we investigated phantom limb pain and the senses of agency and ownership (i.e., a feeling of having one's own body) of the phantom limb. Nine upper-limb amputees, five of whom reported recent phantom limb pain, underwent a single 15-min trial of mirror therapy. Before and after the trial, the participants completed a questionnaire regarding agency, ownership, and pain related to their phantom limb. They reported that the sense of agency over the phantom limb increased following the mirror therapy trial, while the ownership slightly increased but not as much as did the agency. The reported pain did not change; that is, it was comparably mild before and after the trial. These results suggest that short-term mirror therapy can, at least transiently, selectively enhance the sense of agency over a phantom limb, but may not alleviate phantom limb pain.

Topological superfluids confined in a regular nano-scale slab geometry

Energy Technology Data Exchange (ETDEWEB)

Saunders, John; Bennett, Robert; Levitin, Lev; Casey, Andrew; Cowan, Brian [Department of Physics, Royal Holloway University of London, Egham, Surrey, TW20 0EX (United Kingdom); Parpia, Jeevak [Department of Physics, Cornell University, Ithaca, NY 14853 (United States); Drung, Dietmar; Schurig, Thomas [Physikalisch-Technische Bundesanstalt, Abbestrasse 2-12, D-19587, Berlin (Germany)

2012-07-01

Superfluid 3He confined in a regular nano-fabricated slab geometry provides a model system for the investigation of surface and thin film effects in a p-wave superfluid. We have fabricated and cooled such samples to well below 1 mK for the first time, and investigated their NMR response, exploiting a SQUID NMR spectrometer of exquisite sensitivity. We have used NMR on a 650 nm thick superfluid slab to identify the profound effect of confinement on the relative stability of the A and B phases and to make quantitative measurements of the suppression and surface induced distortion of the order parameter. In these systems the effective confinement length scale (slab thickness/superfluid coherence length) is the new tuning parameter. Increasing confinement should stabilize new p-wave superfluid states of matter, such as the quasi-2D gapped A phase or the planar phase. Nanofluidic samples of superfluid 3He promise a route to explore topological superfluids and their surface, edge and defect-bound excitations under well controlled conditions.

Calibrating a large slab vessel: A battle of the bulge

International Nuclear Information System (INIS)

Thomas, I.R.

1993-01-01

Slab tanks (critically-safe-by-geometry vessels) were proposed for the storage of concentrated, highly-enriched uranium solution in the design of the Fuel Processing Restoration (FPR) Facility at the Idaho Chemical Processing Plant (ICPP). Currently, measurements of bulk mass in ICPP annular vessels have standard deviations on the order of 0.2%, or less. ICPP personnel felt that their inexperience with the aforementioned expansions would prevent them from attaining comparable precision with slab tanks. To help assess the measurement accuracy of slab vessels, a full-scale mockup of those proposed for the FPR Facility was installed for test calibrations. These calibrations were designed to detect vessel expansion under differing conditions. This paper will compare the base-line, water calibrations with those of the higher-density aluminum nitrate, and any observed deflection will be described using vessel calibration techniques. The calibration using water at an elevated temperature was not performed due to the difficulty of maintaining the elevated temperature. This calibration probably will not be conducted because the construction of the FPR Facility has been halted

Casimir-type effects for scalar fields interacting with material slabs

International Nuclear Information System (INIS)

Fialkovsky, I V; Pis'mak, Yu M; Markov, V N

2010-01-01

We study the field theoretical model of a scalar field in the presence of spacial inhomogeneities in the form of one and two finite-width mirrors (material slabs). The interaction of the scalar field with the defect is described with a position-dependent mass term. For a single-layer system we develop a rigorous calculation method and derive explicitly the propagator of the theory, the S-matrix elements and the Casimir self-energy of the slab. Detailed investigation of particular limits of self-energy is presented, and the connection to known cases is discussed. The calculation method is also found applicable to the two-mirror case. With its help we derive the corresponding Casimir energy and analyze it. For particular values of parameters of the model an obtained result recovers the Lifshitz formula. We also propose a procedure to unambiguously obtain the finite Casimir self-energy of a single slab without reference to any renormalization conditions. We hope that our approach can be applied to the calculation of Casimir self-energies in other demanded cases (such as a dielectric ball, etc).

Technical Note: Characterization of custom 3D printed multimodality imaging phantoms

International Nuclear Information System (INIS)

Bieniosek, Matthew F.; Lee, Brian J.; Levin, Craig S.

2015-01-01

Purpose: Imaging phantoms are important tools for researchers and technicians, but they can be costly and difficult to customize. Three dimensional (3D) printing is a widely available rapid prototyping technique that enables the fabrication of objects with 3D computer generated geometries. It is ideal for quickly producing customized, low cost, multimodal, reusable imaging phantoms. This work validates the use of 3D printed phantoms by comparing CT and PET scans of a 3D printed phantom and a commercial “Micro Deluxe” phantom. This report also presents results from a customized 3D printed PET/MRI phantom, and a customized high resolution imaging phantom with sub-mm features. Methods: CT and PET scans of a 3D printed phantom and a commercial Micro Deluxe (Data Spectrum Corporation, USA) phantom with 1.2, 1.6, 2.4, 3.2, 4.0, and 4.8 mm diameter hot rods were acquired. The measured PET and CT rod sizes, activities, and attenuation coefficients were compared. A PET/MRI scan of a custom 3D printed phantom with hot and cold rods was performed, with photon attenuation and normalization measurements performed with a separate 3D printed normalization phantom. X-ray transmission scans of a customized two level high resolution 3D printed phantom with sub-mm features were also performed. Results: Results show very good agreement between commercial and 3D printed micro deluxe phantoms with less than 3% difference in CT measured rod diameter, less than 5% difference in PET measured rod diameter, and a maximum of 6.2% difference in average rod activity from a 10 min, 333 kBq/ml (9 μCi/ml) Siemens Inveon (Siemens Healthcare, Germany) PET scan. In all cases, these differences were within the measurement uncertainties of our setups. PET/MRI scans successfully identified 3D printed hot and cold rods on PET and MRI modalities. X-ray projection images of a 3D printed high resolution phantom identified features as small as 350 μm wide. Conclusions: This work shows that 3D printed

Technical Note: Characterization of custom 3D printed multimodality imaging phantoms

Energy Technology Data Exchange (ETDEWEB)

Bieniosek, Matthew F. [Department of Electrical Engineering, Stanford University, 350 Serra Mall, Stanford, California 94305 (United States); Lee, Brian J. [Department of Mechanical Engineering, Stanford University, 440 Escondido Mall, Stanford, California 94305 (United States); Levin, Craig S., E-mail: cslevin@stanford.edu [Departments of Radiology, Physics, Bioengineering and Electrical Engineering, Stanford University, 300 Pasteur Dr., Stanford, California 94305-5128 (United States)

2015-10-15

Purpose: Imaging phantoms are important tools for researchers and technicians, but they can be costly and difficult to customize. Three dimensional (3D) printing is a widely available rapid prototyping technique that enables the fabrication of objects with 3D computer generated geometries. It is ideal for quickly producing customized, low cost, multimodal, reusable imaging phantoms. This work validates the use of 3D printed phantoms by comparing CT and PET scans of a 3D printed phantom and a commercial “Micro Deluxe” phantom. This report also presents results from a customized 3D printed PET/MRI phantom, and a customized high resolution imaging phantom with sub-mm features. Methods: CT and PET scans of a 3D printed phantom and a commercial Micro Deluxe (Data Spectrum Corporation, USA) phantom with 1.2, 1.6, 2.4, 3.2, 4.0, and 4.8 mm diameter hot rods were acquired. The measured PET and CT rod sizes, activities, and attenuation coefficients were compared. A PET/MRI scan of a custom 3D printed phantom with hot and cold rods was performed, with photon attenuation and normalization measurements performed with a separate 3D printed normalization phantom. X-ray transmission scans of a customized two level high resolution 3D printed phantom with sub-mm features were also performed. Results: Results show very good agreement between commercial and 3D printed micro deluxe phantoms with less than 3% difference in CT measured rod diameter, less than 5% difference in PET measured rod diameter, and a maximum of 6.2% difference in average rod activity from a 10 min, 333 kBq/ml (9 μCi/ml) Siemens Inveon (Siemens Healthcare, Germany) PET scan. In all cases, these differences were within the measurement uncertainties of our setups. PET/MRI scans successfully identified 3D printed hot and cold rods on PET and MRI modalities. X-ray projection images of a 3D printed high resolution phantom identified features as small as 350 μm wide. Conclusions: This work shows that 3D printed

Technical Note: Characterization of custom 3D printed multimodality imaging phantoms.

Science.gov (United States)

Bieniosek, Matthew F; Lee, Brian J; Levin, Craig S

2015-10-01

Imaging phantoms are important tools for researchers and technicians, but they can be costly and difficult to customize. Three dimensional (3D) printing is a widely available rapid prototyping technique that enables the fabrication of objects with 3D computer generated geometries. It is ideal for quickly producing customized, low cost, multimodal, reusable imaging phantoms. This work validates the use of 3D printed phantoms by comparing CT and PET scans of a 3D printed phantom and a commercial "Micro Deluxe" phantom. This report also presents results from a customized 3D printed PET/MRI phantom, and a customized high resolution imaging phantom with sub-mm features. CT and PET scans of a 3D printed phantom and a commercial Micro Deluxe (Data Spectrum Corporation, USA) phantom with 1.2, 1.6, 2.4, 3.2, 4.0, and 4.8 mm diameter hot rods were acquired. The measured PET and CT rod sizes, activities, and attenuation coefficients were compared. A PET/MRI scan of a custom 3D printed phantom with hot and cold rods was performed, with photon attenuation and normalization measurements performed with a separate 3D printed normalization phantom. X-ray transmission scans of a customized two level high resolution 3D printed phantom with sub-mm features were also performed. Results show very good agreement between commercial and 3D printed micro deluxe phantoms with less than 3% difference in CT measured rod diameter, less than 5% difference in PET measured rod diameter, and a maximum of 6.2% difference in average rod activity from a 10 min, 333 kBq/ml (9 μCi/ml) Siemens Inveon (Siemens Healthcare, Germany) PET scan. In all cases, these differences were within the measurement uncertainties of our setups. PET/MRI scans successfully identified 3D printed hot and cold rods on PET and MRI modalities. X-ray projection images of a 3D printed high resolution phantom identified features as small as 350 μm wide. This work shows that 3D printed phantoms can be functionally equivalent to

Negotiating Multicollinearity with Spike-and-Slab Priors.

Science.gov (United States)

Ročková, Veronika; George, Edward I

2014-08-01

In multiple regression under the normal linear model, the presence of multicollinearity is well known to lead to unreliable and unstable maximum likelihood estimates. This can be particularly troublesome for the problem of variable selection where it becomes more difficult to distinguish between subset models. Here we show how adding a spike-and-slab prior mitigates this difficulty by filtering the likelihood surface into a posterior distribution that allocates the relevant likelihood information to each of the subset model modes. For identification of promising high posterior models in this setting, we consider three EM algorithms, the fast closed form EMVS version of Rockova and George (2014) and two new versions designed for variants of the spike-and-slab formulation. For a multimodal posterior under multicollinearity, we compare the regions of convergence of these three algorithms. Deterministic annealing versions of the EMVS algorithm are seen to substantially mitigate this multimodality. A single simple running example is used for illustration throughout.

3-D Transient Heat Transfer Analysis of Slab Heating Characteristics in a Reheating Furnace in Hot Strip Mills

OpenAIRE

J. Y. Jang; Y. W. Lee; C. N. Lin; C. H. Wang

2015-01-01

The reheating furnace is used to reheat the steel slabs before the hot-rolling process. The supported system includes the stationary/moving beams, and the skid buttons which block some thermal radiation transmitted to the bottom of the slabs. Therefore, it is important to analyze the steel slab temperature distribution during the heating period. A three-dimensional mathematical transient heat transfer model for the prediction of temperature distribution within the slab ha...

Subducted slabs and lateral viscosity variations: effects on the long-wavelength geoid

Science.gov (United States)

Tosi, Nicola; Čadek, Ondřej; Martinec, Zdeněk

2009-11-01

The characteristic broad local maxima exhibited by the long-wavelength geoid over subduction zones are investigated with a numerical model of mantle flow. In a spherical axisymmetric geometry, a synthetic model of buoyancy driven subduction is used to test the effects on the geoid caused by the depth of penetration of the lithosphere into the mantle, by the viscosity stratification and by lateral viscosity variations (LVV) in the lithosphere, upper and lower mantle. The presence of anomalous slab density in the lower mantle guarantees geoid amplitudes comparable with the observations, favouring the picture of slabs that penetrate the transition zone and sink into the deep mantle. The viscosity of the lower mantle controls the long-wavelength geoid to the first order, ensuring a clear positive signal when it is at least 30-times greater than the upper-mantle viscosity. The presence of LVV in the lithosphere, in the form of weak plate margins, helps to increase the contribution of the surface topography, causing a pronounced reduction of the geoid. Localized LVV associated with the cold slab play a secondary role if they are in the upper mantle. On the other hand, highly viscous slabs in the lower mantle exert a large influence on the geoid. They cause its amplitude to increase dramatically, way beyond the values typically observed over subduction zones. Long-wavelength flow becomes less vigorous as the slab viscosity increases. Deformation in the upper mantle becomes more localized and power is transferred to short wavelengths, causing the long-wavelength surface topography to diminish and the total geoid to increase. Slabs may be then weakened in the lower mantle or retain their high viscosity while other mechanisms act to lower the geoid. It is shown that a phase change from perovskite to post-perovskite above the core-mantle boundary can cause the geoid to reduce significantly, thereby helping to reconcile models and observations.

Quality control of portal imaging with PTW EPID QC PHANTOM {sup registered}

Energy Technology Data Exchange (ETDEWEB)

Pesznyak, Csilla; Kiraly, Reka; Polgar, Istvan; Zarand, Pal; Mayer, Arpad [Inst. of Oncoradiology, Uzsoki Hospital, Budapest (Hungary); Fekete, Gabor [Dept. of Oncotherapy, Univ. of Szeged (Hungary); Mozes, Arpad [Oncology Center, Kalman Pandy County Hospital, Gyula (Hungary); Kiss, Balazs [Dept. of Radiation Oncology, Markusovszky County Hospital, Szombathely (Hungary)

2009-01-15

Purpose: quality assurance (QA) and quality control (QC) of different electronic portal imaging devices (EPID) and portal images with the PTW EPID QC PHANTOM {sup registered}. Material and methods: characteristic properties of images of different file formats were measured on Siemens OptiVue500aSi {sup registered}, Siemens BeamView Plus {sup registered}, Elekta iView {sup registered}, and Varian PortalVision trademark and analyzed with the epidSoft {sup registered} 2.0 program in four radiation therapy centers. The portal images were taken with Kodak X-OMAT V {sup registered} and the Kodak Portal Localisation ReadyPack {sup registered} films and evaluated with the same program. Results: the optimal exposition both for EPIDs and portal films of different kind was determined. For double exposition, the 2+1 MU values can be recommended in the case of Siemens OptiVue500aSi {sup registered}, Elekta iView {sup registered} and Kodak Portal Localisation ReadyPack {sup registered} films, while for Siemens BeamView Plus {sup registered}, Varian PortalVision trademark and Kodak X-OMAT V {sup registered} film 7+7 MU is recommended. Conclusion: the PTW EPID QC PHANTOM {sup registered} can be used not only for amorphous silicon EPIDs but also for images taken with a video-based system or by using an ionization chamber matrix or for portal film. For analysis of QC tests, a standardized format (used at the acceptance test) should be applied, as the results are dependent on the file format used. (orig.)

Slab cooling system design using computer simulation

NARCIS (Netherlands)

Lain, M.; Zmrhal, V.; Drkal, F.; Hensen, J.L.M.

2007-01-01

For a new technical library building in Prague computer simulations were carried out to help design of slab cooling system and optimize capacity of chillers. In the paper is presented concept of new technical library HVAC system, the model of the building, results of the energy simulations for

Design of a tracked ultrasound calibration phantom made of LEGO bricks

Science.gov (United States)

Walsh, Ryan; Soehl, Marie; Rankin, Adam; Lasso, Andras; Fichtinger, Gabor

2014-03-01

PURPOSE: Spatial calibration of tracked ultrasound systems is commonly performed using precisely fabricated phantoms. Machining or 3D printing has relatively high cost and not easily available. Moreover, the possibilities for modifying the phantoms are very limited. Our goal was to find a method to construct a calibration phantom from affordable, widely available components, which can be built in short time, can be easily modified, and provides comparable accuracy to the existing solutions. METHODS: We designed an N-wire calibration phantom made of LEGO® bricks. To affirm the phantom's reproducibility and build time, ten builds were done by first-time users. The phantoms were used for a tracked ultrasound calibration by an experienced user. The success of each user's build was determined by the lowest root mean square (RMS) wire reprojection error of three calibrations. The accuracy and variance of calibrations were evaluated for the calibrations produced for various tracked ultrasound probes. The proposed model was compared to two of the currently available phantom models for both electromagnetic and optical tracking. RESULTS: The phantom was successfully built by all ten first-time users in an average time of 18.8 minutes. It cost approximately $10 CAD for the required LEGO® bricks and averaged a 0.69mm of error in the calibration reproducibility for ultrasound calibrations. It is one third the cost of similar 3D printed phantoms and takes much less time to build. The proposed phantom's image reprojections were 0.13mm more erroneous than those of the highest performing current phantom model The average standard deviation of multiple 3D image reprojections differed by 0.05mm between the phantoms CONCLUSION: It was found that the phantom could be built in less time, was one third the cost, compared to similar 3D printed models. The proposed phantom was found to be capable of producing equivalent calibrations to 3D printed phantoms.

Interaction of the Cyprus/Tethys Slab With the Mantle Transition Zone Beneath Anatolia

Science.gov (United States)

Thompson, D. A.; Rost, S.; Taylor, G.; Cornwell, D. G.

2017-12-01

The geodynamics of the eastern Mediterranean are dominated by northward motion of the Arabian/African continents and subduction of the oldest oceanic crust on the planet along the Aegean and Cyprean trenches. These slabs have previously been imaged using seismic tomography on a continental scale, but detailed information regarding their descent from upper to lower mantle and how they interact with the mantle transition zone have been severely lacking. The Dense Array for North Anatolia (DANA) was a 73 station passive seismic deployment active between 2012-2013 with the primary aim of imaging shallow structure beneath the North Anatolian Fault. However, we exploit the exceptional dataset recorded by DANA to characterise a region where the Cyprus Slab impinges upon the mantle transition zone beneath northern Turkey, providing arguably the most detailed view of a slab as it transits from the upper to lower mantle. We map varying depths and amplitudes of the transition zone seismic discontinuities (`410', `520' and `660') in 3D using over 1500 high quality receiver functions over an area of approximately 200km x 300km. The `410' is observed close to its predicted depth, but the `660' is depressed to >670 km across the entirety of the study region. This is consistent with an accumulation of cold subducted material at the base of the upper mantle, and the presence of a `520' discontinuity in the vicinity of the slab surface also suggests that the slab is present deep within the transition zone. Anomalous low velocity layers above and within the transition zone are constrained and may indicate hydration and ongoing mass/fluid flux between upper and lower mantle in the presence of subduction. The results of the study have implications not only for the regional geodynamics of Anatolia, but also for slab dynamics globally.

Numerical analysis of the shifting slabs applied in a wireless power transfer system to enhance magnetic coupling

Science.gov (United States)

Dong, Yayun; Yang, Xijun; Jin, Nan; Li, Wenwen; Yao, Chen; Tang, Houjun

2017-05-01

Shifting medium is a kind of metamaterial, which can optically shift a space or an object a certain distance away from its original position. Based on the shifting medium, we propose a concise pair of shifting slabs covering the transmitting or receiving coil in a two-coil wireless power transfer system to decrease the equivalent distance between the coils. The electromagnetic parameters of the shifting slabs are calculated by transformation optics. Numerical simulations validate that the shifting slabs can approximately shift the electromagnetic fields generated by the covered coil; thus, the magnetic coupling and the efficiency of the system are enhanced while remaining the physical transmission distance unchanged. We also verify the advantages of the shifting slabs over the magnetic superlens. Finally, we provide two methods to fabricate shifting slabs based on split-ring resonators.

Wood slabs as a proposed solution to the design and construction of pavement

Directory of Open Access Journals (Sweden)

Carlos Alfonso Devia Castillo

2016-01-01

Full Text Available Alternatives to replace concrete slabs for prefabricated wood as structure of pavement with wearing course was evaluated, ensuring that these prefabrications work as a single element using finger joints. The mechanical behavior of two types of wood identified through simulations implementing a method of finite elements was evaluated, to subsequently determined optimal configuration for the alternative design with wood pavements and finally verified in the laboratory with the optimal configuration determined with simulation for a design of 440 000 vehicles shafts, with the use of the MTS machine and a load of 6.50 tons equivalent to a load of a single axle shaft with two wheels, found that for different traffic design the thickness of the slab of wood to resist this load varies between 0.125 and 0.24 meters. This research shows that prefabricated wood building systems are a viable alternative in the market for pavement construction in the structural sense; additionally, they are an innovation since they modify the structural system of slabs, conventionally built on concrete slabs and reduce environmental impact.

Radiation dose verification using real tissue phantom in modern radiotherapy techniques

International Nuclear Information System (INIS)

Gurjar, Om Prakash; Mishra, S.P.; Bhandari, Virendra; Pathak, Pankaj; Patel, Prapti; Shrivastav, Garima

2014-01-01

In vitro dosimetric verification prior to patient treatment has a key role in accurate and precision radiotherapy treatment delivery. Most of commercially available dosimetric phantoms have almost homogeneous density throughout their volume, while real interior of patient body has variable and varying densities inside. In this study an attempt has been made to verify the physical dosimetry in actual human body scenario by using goat head as 'head phantom' and goat meat as 'tissue phantom'. The mean percentage variation between planned and measured doses was found to be 2.48 (standard deviation (SD): 0.74), 2.36 (SD: 0.77), 3.62 (SD: 1.05), and 3.31 (SD: 0.78) for three-dimensional conformal radiotherapy (3DCRT) (head phantom), intensity modulated radiotherapy (IMRT; head phantom), 3DCRT (tissue phantom), and IMRT (tissue phantom), respectively. Although percentage variations in case of head phantom were within tolerance limit (< ± 3%), but still it is higher than the results obtained by using commercially available phantoms. And the percentage variations in most of cases of tissue phantom were out of tolerance limit. On the basis of these preliminary results it is logical and rational to develop radiation dosimetry methods based on real human body and also to develop an artificial phantom which should truly represent the interior of human body. (author)

Radiation dose verification using real tissue phantom in modern radiotherapy techniques

Directory of Open Access Journals (Sweden)

Om Prakash Gurjar

2014-01-01

Full Text Available In vitro dosimetric verification prior to patient treatment has a key role in accurate and precision radiotherapy treatment delivery. Most of commercially available dosimetric phantoms have almost homogeneous density throughout their volume, while real interior of patient body has variable and varying densities inside. In this study an attempt has been made to verify the physical dosimetry in actual human body scenario by using goat head as "head phantom" and goat meat as "tissue phantom". The mean percentage variation between planned and measured doses was found to be 2.48 (standard deviation (SD: 0.74, 2.36 (SD: 0.77, 3.62 (SD: 1.05, and 3.31 (SD: 0.78 for three-dimensional conformal radiotherapy (3DCRT (head phantom, intensity modulated radiotherapy (IMRT; head phantom, 3DCRT (tissue phantom, and IMRT (tissue phantom, respectively. Although percentage variations in case of head phantom were within tolerance limit (< ± 3%, but still it is higher than the results obtained by using commercially available phantoms. And the percentage variations in most of cases of tissue phantom were out of tolerance limit. On the basis of these preliminary results it is logical and rational to develop radiation dosimetry methods based on real human body and also to develop an artificial phantom which should truly represent the interior of human body.

Semi-analytical model for a slab one-dimensional photonic crystal

Science.gov (United States)

Libman, M.; Kondratyev, N. M.; Gorodetsky, M. L.

2018-02-01

In our work we justify the applicability of a dielectric mirror model to the description of a real photonic crystal. We demonstrate that a simple one-dimensional model of a multilayer mirror can be employed for modeling of a slab waveguide with periodically changing width. It is shown that this width change can be recalculated to the effective refraction index modulation. The applicability of transfer matrix method of reflection properties calculation was demonstrated. Finally, our 1-D model was employed to analyze reflection properties of a 2-D structure - a slab photonic crystal with a number of elliptic holes.

Research and Development of the Solidification of Slab Ingots from Special Tool Steels

Directory of Open Access Journals (Sweden)

Tkadlečková M.

2017-09-01

Full Text Available The paper describes the research and development of casting and solidification of slab ingots from special tool steels by means of numerical modelling using the finite element method. The pre-processing, processing and post-processing phases of numerical modelling are outlined. Also, problems with determining the thermophysical properties of materials and heat transfer between the individual parts of the casting system are discussed. Based on the type of grade of tool steel, the risk of final porosity is predicted. The results allowed to improve the production technology of slab ingots, and also to verify the ratio, the chamfer and the external/ internal shape of the wall of the new designed slab ingots.

NURBS-based 3-d anthropomorphic computational phantoms for radiation dosimetry applications

International Nuclear Information System (INIS)

Lee, Choonsik; Lodwick, Daniel; Lee, Choonik; Bolch, Wesley E.

2007-01-01

Computational anthropomorphic phantoms are computer models used in the evaluation of absorbed dose distributions within the human body. Currently, two classes of the computational phantoms have been developed and widely utilised for dosimetry calculation: (1) stylized (equation-based) and (2) voxel (image-based) phantoms describing human anatomy through the use of mathematical surface equations and 3-D voxel matrices, respectively. However, stylized phantoms have limitations in defining realistic organ contours and positioning as compared to voxel phantoms, which are themselves based on medical images of human subjects. In turn, voxel phantoms that have been developed through medical image segmentation have limitations in describing organs that are presented in low contrast within either magnetic resonance or computed tomography image. The present paper reviews the advantages and disadvantages of these existing classes of computational phantoms and introduces a hybrid approach to a computational phantom construction based on non-uniform rational B-Spline (NURBS) surface animation technology that takes advantage of the most desirable features of the former two phantom types. (authors)

Cohesive cracked-hinge model for simulation of fracture in one-way slabs on grade

DEFF Research Database (Denmark)

Skar, Asmus; Poulsen, Peter Noe; Olesen, John Forbes

2017-01-01

Numerical analysis of slab on grade structures subjected to mechanical loads is a complex matter often requiring computationally expensive models. In order to develop a simplified and general concept for non-linear analysis of slab on grade structures, this paper presents a cohesive cracked-hinge...

Regional heating patterns of RF hyperthermia applicators in phantoms

International Nuclear Information System (INIS)

Kantor, G.; Ruggera, P.S.; Samulski, T.V.

1984-01-01

An elliptical phantom (20 cm by 30 cm cross-section and 40 cm long) with a 1 cm fat layer filled with muscle material was used to compare the induced heating patterns of the NCDRH helical coil, a Henry Medical Magnetrode coil, both with a diameter of 35.6 cm, and the BSD Annular Phased Array System (APAS). Temperature profiles were taken in the midplane cross-sectional slice along the major and minor axes of the phantom. These profiles were measured with a Vitek thermistor probe and the associated specific absorption rates (SAR) were determined from this data. SAR curves for each applicator were obtained along the major and minor axes of the phantom. The depths of heating of the Magnetrode applicator are considerably smaller than those for the helical applicator. Heating patterns for the APAS can be highly variable and asymmetric depending on the frequency of operation and the location of the phantom within the APAS aperture. While the APAS requires a water bolus for good coupling, the NCDRH and Magnetrode coils need only to be air coupled for good phantom coupling. Both the helical applicator and APAS can provide significant heating in the central region of the phantom. However, the heating of the helical coil does not critically depend on the phantom loading

Cellular Neural Network Method for Critical Slab with Albedo Boundary Condition

International Nuclear Information System (INIS)

Pirouzmanda, A.; Hadada, K.; Suh, K. Y.

2010-01-01

The neutron transport problems have been studied theoretically and numerically for years. A number of researchers have studied the criticality problems of one-speed neutrons in homogeneous slabs and spheres using various methods. The Chebyshev polynomial approximation method (T N method) has lately been developed and improved for the neutron transport equation in slab geometry. The one-speed time-dependent neutron transport equation using the Cellular Neural Network (CNN) for the vacuum boundary condition has previously been solved. In this paper, we demonstrate the capacity of CNN in calculating the critical slab thickness for different boundary conditions and its variation with moments N. The architecture of the CNN has already been dealt with thoroughly. Essentially, the CNN is used to model a first-order system of the partial differential equations (PDEs). The original equations in the T N approximation are also a set of PDEs. The CNN approach lends itself to analog VLSI implementation. In this study, the CNN model is implemented using the HSpice software package

High Performance Slab-on-Grade Foundation Insulation Retrofits

Energy Technology Data Exchange (ETDEWEB)

Goldberg, Louise F. [NorthernSTAR, St. Paul, MN (United States); Mosiman, Garrett E. [NorthernSTAR, St. Paul, MN (United States)

2015-09-01

?A more accurate assessment of SOG foundation insulation energy savings than traditionally possible is now feasible. This has been enabled by advances in whole building energy simulation with 3-dimensional foundation modelling integration at each time step together with an experimental measurement of the site energy savings of SOG foundation insulation. Ten SOG insulation strategies were evaluated on a test building to identify an optimum retrofit insulation strategy in a zone 6 climate (Minneapolis, MN). The optimum insulation strategy in terms of energy savings and cost effectiveness consisted of two components: (a) R-20 XPS insulation above grade, and, (b) R-20 insulation at grade (comprising an outer layer of R-10 insulation and an interior layer of R-12 poured polyurethane insulation) tapering to R-10 XPS insulation at half the below-grade wall height (the lower half of the stem wall was uninsulated). The optimum insulation strategy was applied to single and multi-family residential buildings in climate zone 4 - 7. The highest site energy savings of 5% was realized for a single family home in Duluth, MN, and the lowest savings of 1.4 % for a 4-unit townhouse in Richmond, VA. SOG foundation insulation retrofit simple paybacks ranged from 18 to 47 years. There are other benefits of SOG foundation insulation resulting from the increase in the slab surface temperatures. These include increased occupant thermal comfort, and a decrease in slab surface condensation particularly around the slab perimeter.

Tomographically-imaged subducted slabs and magmatic history of Caribbean and Pacific subduction beneath Colombia

Science.gov (United States)

Bernal-Olaya, R.; Mann, P.; Vargas, C. A.; Koulakov, I.

2013-12-01

We define the length and geometry of eastward and southeastward-subducting slabs beneath northwestern South America in Colombia using ~100,000 earthquake events recorded by the Colombian National Seismic Network from 1993 to 2012. Methods include: hypocenter relocation, compilation of focal mechanisms, and P and S wave tomographic calculations performed using LOTOS and Seisan. The margins of Colombia include four distinct subduction zones based on slab dip: 1) in northern Colombia, 12-16-km-thick oceanic crust subducts at a modern GPS rate of 20 mm/yr in a direction of 110 degrees at a shallow angle of 8 degrees; as a result of its low dip, Pliocene-Pleistocene volcanic rocks are present 400 km from the frontal thrust; magmatic arc migration to the east records 800 km of subduction since 58 Ma ago (Paleocene) with shallow subduction of the Caribbean oceanic plateau starting ~24-33 Ma (Miocene); at depths of 90-150 km, the slab exhibits a negative velocity anomaly we associate with pervasive fracturing; 2) in the central Colombia-Panama area, we define an area of 30-km-thick crust of the Panama arc colliding/subducting at a modern 30/mm in a direction of 95 degrees; the length of this slab shows subduction/collision initiated after 20 Ma (Middle Miocene); we call this feature the Panama indenter since it has produced a V-shaped indentation of the Colombian margin and responsible for widespread crustal deformation and topographic uplift in Colombia; an incipient subduction area is forming near the Panama border with intermediate earthquakes at an eastward dip of 70 degrees to depths of ~150 km; this zone is not visible on tomographic images; 3) a 250-km-wide zone of Miocene oceanic crust of the Nazca plate flanking the Panama indenter subducts at a rate of 25 mm/yr in a direction of 55 degrees and at a normal dip of 40 degrees; the length of this slab suggests subduction began at ~5 Ma; 4) the Caldas tear defines a major dip change to the south where a 35 degrees

Phantom dark ghost in Einstein-Cartan gravity

Energy Technology Data Exchange (ETDEWEB)

Chang, Yu-Chiao [National Taiwan University, Department of Physics, Taipei (China); National Taiwan University, LeCosPA, Taipei (China); Bouhmadi-Lopez, Mariam [University of the Basque Country UPV/EHU, Department of Theoretical Physics, P.O. Box 644, Bilbao (Spain); Basque Foundation for Science, IKERBASQUE, Bilbao (Spain); Chen, Pisin [National Taiwan University, Department of Physics, Taipei (China); National Taiwan University, LeCosPA, Taipei (China); National Taiwan University, Graduate Institute of Astrophysics, Taipei (China); SLAC National Accelerator Laboratory, Stanford University, Kavli Institute for Particle Astrophysics and Cosmology, Stanford, CA (United States)

2017-05-15

A class of dynamical dark energy models is constructed through an extended version of fermion fields corresponding to phantom dark ghost spinors, which are spin 1/2 with mass dimension 1. We find that if these spinors interact with torsion fields in a homogeneous and isotropic universe, then it does not imply any future dark energy singularity or any abrupt event, though the fermion has a negative kinetic energy. In fact, the equation of state of this dark energy model will asymptotically approach the value w = -1 from above without crossing the phantom divide and inducing therefore a de Sitter state. Consequently, we expect the model to be stable because no real phantom fields will be created. At late time, the torsion fields will vanish as the corresponding phantom dark ghost spinors dilute. As would be expected, intuitively, this result is unaffected by the presence of cold dark matter although the proof is not as straightforward as in general relativity. (orig.)

Exposure buildup factors for a cobalt-60 point isotropic source for single and two layer slabs

International Nuclear Information System (INIS)

Chakarova, R.

1992-01-01

Exposure buildup factors for point isotropic cobalt-60 sources are calculated by the Monte Carlo method with statistical errors ranging from 1.5 to 7% for 1-5 mean free paths (mfp) thick water and iron single slabs and for 1 and 2 mfp iron layers followed by water layers 1-5 mfp thick. The computations take into account Compton scattering. The Monte Carlo data for single slab geometries are approximated by Geometric Progression formula. Kalos's formula using the calculated single slab buildup factors may be applied to reproduce the data for two-layered slabs. The presented results and discussion may help when choosing the manner in which the radiation field gamma irradiation units will be described. (author)

Engineering the near-field imaging of a rectangular-lattice photonic-crystal slab in the second band

Institute of Scientific and Technical Information of China (English)

无

2009-01-01

Imaging properties of a two-dimensional rectangular-lattice photonic crystal (PC) slab consisting of air holes immersed in a dielectric are studied in this work. The field patterns of electromagnetic waves radiated from a point source through the PC slab are calculated with the finite-difference time-domain method. Comparing the field patterns with the corresponding equifrequency-surface contours simulated by the plane-wave expansion method, we find that an excellent-quality near-field image may be formed through the PC slab by the mechanisms of the simultaneous action of the self-collimation effect and the negative-refraction effect. Near-field imaging may be obtained within two different frequency regions in two vertical directions of the PC slab.