Reduced abrasion drilling fluid

NARCIS (Netherlands)

2010-01-01

A reduced abrasion drilling fluid system and method of drilling a borehole by circulating the reduced abrasion drilling fluid through the borehole is disclosed. The reduced abrasion drilling fluid comprises a drilling fluid, a first additive and a weighting agent, wherein the weighting agent has a

Reduced abrasion drilling fluid

NARCIS (Netherlands)

2012-01-01

A reduced abrasion drilling fluid system and method of drilling a borehole by circulating the reduced abrasion drilling fluid through the borehole is disclosed. The reduced abrasion drilling fluid comprises a drilling fluid, a first additive and a weighting agent, wherein the weighting agent has a

The model of the dependence of the abrasive wear value on the maximal linear wear

Directory of Open Access Journals (Sweden)

О.А. Вишневський

2004-01-01

Full Text Available  The relation of the contact area of the rubber roll with a sample and the maximal linear wear value is found. The mathematical model of the dependence of the wear volume weight value on the maximal dimple depth is presented with the friction on abrasive particles fixed nonrigidly. The relation of volume weight wear with the rubber roll contact surface area with a sample with the friction on abrasive particles fixed nonrigidly is established.

Computational modeling of ultra-short-pulse ablation of enamel

Energy Technology Data Exchange (ETDEWEB)

London, R.A.; Bailey, D.S.; Young, D.A. [and others

1996-02-29

A computational model for the ablation of tooth enamel by ultra-short laser pulses is presented. The role of simulations using this model in designing and understanding laser drilling systems is discussed. Pulses of duration 300 sec and intensity greater than 10{sup 12} W/cm{sup 2} are considered. Laser absorption proceeds via multi-photon initiated plasma mechanism. The hydrodynamic response is calculated with a finite difference method, using an equation of state constructed from thermodynamic functions including electronic, ion motion, and chemical binding terms. Results for the ablation efficiency are presented. An analytic model describing the ablation threshold and ablation depth is presented. Thermal coupling to the remaining tissue and long-time thermal conduction are calculated. Simulation results are compared to experimental measurements of the ablation efficiency. Desired improvements in the model are presented.

Synthesis CNTs Particle Based Abrasive Media for Abrasive Flow Machining Process

International Nuclear Information System (INIS)

Kumar, Sonu; Walia, R.S; Dhull, S.; Murtaza, Q.; Tyagi, P. K.

2016-01-01

Abrasive flow machining (AFM) is a modem fine finishing process used for intricate and internal finishing of components or parts. It is based on flowing of viscoelastic abrasive media over the surface to be fine finished. The abrasive media is the important parameter in the AFM process because of its ability to accurately abrade the predefined area along it flow path. In this study, an attempt is made to develop a new abrasive, alumina with Carbon nanotubes (CNTs) in viscoelastic medium. CNT s in house produced through chemical vapour deposition technique and characterize through TEM. Performance evaluation of the new abrasive media is carried out by increasing content of CNT s with fixed extrusion pressure, viscosity of media and media flow rate as process parameters and surface finish improvement and material removal as process responses in AFM setup. Significantly improvement has been observed in material removal and maximum improvement of 100% has been observed in the surface finish on the inner cylindrical surface of the cast iron work piece. (paper)

Neutral and plasma shielding model for pellet ablation

International Nuclear Information System (INIS)

Houlberg, W.A.; Milora, S.L.; Attenberger, S.E.

1987-10-01

The neutral gas shielding model for ablation of frozen hydrogenic pellets is extended to include the effects of an initial Maxwelliam distribution of incident electron energies; a cold plasma shield outside the neutral shield and extended along the magnetic field; energetic neutral beam ions and alpha particles; and self-limiting electron ablation in the collisionless plasma limit. Including the full electron distribution increases ablation, but adding the cold ionized shield reduces ablation; the net effect is a modest reduction in pellet penetration compared with the monoenergetic electron neutral shielding model with no plasma shield. Unlike electrons, fast ions can enter the neutral shield directly without passing through the cold ionized shield because their gyro-orbits are typically larger than the diameter of the cold plasma tube. Fast alpha particles should not enhance the ablation rate unless their population exceeds that expected from local classical thermalization. Fast beam ions, however, may enhance ablation in the plasma periphery if their population is high enough. Self-limiting ablation in the collisionless limit leads to a temporary distortion of the original plasma electron Maxwellian distribution function through preferential depopulation of the higher-energy electrons. 23 refs., 9 figs

Machining with abrasives

CERN Document Server

Jackson, Mark J

2011-01-01

Abrasive machining is key to obtaining the desired geometry and surface quality in manufacturing. This book discusses the fundamentals and advances in the abrasive machining processes. It provides a complete overview of developing areas in the field.

Desorption/ablation of lithium fluoride induced by extreme ultraviolet laser radiation

Directory of Open Access Journals (Sweden)

Blejchař Tomáš

2016-06-01

Full Text Available The availability of reliable modeling tools and input data required for the prediction of surface removal rate from the lithium fluoride targets irradiated by the intense photon beams is essential for many practical aspects. This study is motivated by the practical implementation of soft X-ray (SXR or extreme ultraviolet (XUV lasers for the pulsed ablation and thin film deposition. Specifically, it is focused on quantitative description of XUV laser-induced desorption/ablation from lithium fluoride, which is a reference large band-gap dielectric material with ionic crystalline structure. Computational framework was proposed and employed here for the reconstruction of plume expansion dynamics induced by the irradiation of lithium fluoride targets. The morphology of experimentally observed desorption/ablation craters were reproduced using idealized representation (two-zone approximation of the laser fluence profile. The calculation of desorption/ablation rate was performed using one-dimensional thermomechanic model (XUV-ABLATOR code taking into account laser heating and surface evaporation of the lithium fluoride target occurring on a nanosecond timescale. This step was followed by the application of two-dimensional hydrodynamic solver for description of laser-produced plasma plume expansion dynamics. The calculated plume lengths determined by numerical simulations were compared with a simple adiabatic expansion (blast-wave model.

Abrasive slurry jet cutting model based on fuzzy relations

Science.gov (United States)

Qiang, C. H.; Guo, C. W.

2017-12-01

The cutting process of pre-mixed abrasive slurry or suspension jet (ASJ) is a complex process affected by many factors, and there is a highly nonlinear relationship between the cutting parameters and cutting quality. In this paper, guided by fuzzy theory, the fuzzy cutting model of ASJ was developed. In the modeling of surface roughness, the upper surface roughness prediction model and the lower surface roughness prediction model were established respectively. The adaptive fuzzy inference system combines the learning mechanism of neural networks and the linguistic reasoning ability of the fuzzy system, membership functions, and fuzzy rules are obtained by adaptive adjustment. Therefore, the modeling process is fast and effective. In this paper, the ANFIS module of MATLAB fuzzy logic toolbox was used to establish the fuzzy cutting model of ASJ, which is found to be quite instrumental to ASJ cutting applications.

Kinetic depletion model for pellet ablation

International Nuclear Information System (INIS)

Kuteev, Boris V.

2001-11-01

A kinetic model for depletion effect, which determines pellet ablation when the pellet passes a rational magnetic surface, is formulated. The model predicts a moderate decrease of the ablation rate compared with the earlier considered monoenergy versions [1, 2]. For typical T-10 conditions the ablation rate reduces by a reactor of 2.5 when the 1-mm pellet penetrates through the plasma center. A substantial deceleration of pellets -about 15% per centimeter of low shire rational q region; is predicted. Penetration for Low Field Side and High Field Side injections is considered taking into account modification of the electron distribution function by toroidal magnetic field. It is shown that Shafranov shift and toroidal effects yield the penetration length for HFS injection higher by a factor of 1.5. This fact should be taken into account when plasma-shielding effects on penetration are considered. (author)

Abrasives and possibilities of increase in efficiency of abrasive waterjets

Czech Academy of Sciences Publication Activity Database

Sitek, Libor; Martinec, Petr

2016-01-01

Roč. 9, March 2016 (2016), s. 877-881 ISSN 1805-0476 R&D Projects: GA MŠk(CZ) LO1406; GA MŠk ED2.1.00/03.0082 Institutional support: RVO:68145535 Keywords : high-speed waterjets * abrasive waterjets * abrasives * garnet * zirconia Subject RIV: JQ - Machines ; Tools http://www.mmscience.eu/content/file/archives/MM_Science_201603.pdf

Microwave Ablation Compared with Radiofrequency Ablation for Breast Tissue in an Ex Vivo Bovine Udder Model

International Nuclear Information System (INIS)

Tanaka, Toshihiro; Westphal, Saskia; Isfort, Peter; Braunschweig, Till; Penzkofer, Tobias; Bruners, Philipp; Kichikawa, Kimihiko; Schmitz-Rode, Thomas; Mahnken, Andreas H.

2012-01-01

Purpose: To compare the effectiveness of microwave (MW) ablation with radiofrequency (RF) ablation for treating breast tissue in a nonperfused ex vivo model of healthy bovine udder tissue. Materials and Methods: MW ablations were performed at power outputs of 25W, 35W, and 45W using a 915-MHz frequency generator and a 2-cm active tip antenna. RF ablations were performed with a bipolar RF system with 2- and 3-cm active tip electrodes. Tissue temperatures were continuously monitored during ablation. Results: The mean short-axis diameters of the coagulation zones were 1.34 ± 0.14, 1.45 ± 0.13, and 1.74 ± 0.11 cm for MW ablation at outputs of 25W, 35W, and 45W. For RF ablation, the corresponding values were 1.16 ± 0.09 and 1.26 ± 0.14 cm with electrodes having 2- and 3-cm active tips, respectively. The mean coagulation volumes were 2.27 ± 0.65, 2.85 ± 0.72, and 4.45 ± 0.47 cm 3 for MW ablation at outputs of 25W, 35W, and 45W and 1.18 ± 0.30 and 2.29 ± 0.55 cm 3 got RF ablation with 2- and 3-cm electrodes, respectively. MW ablations at 35W and 45W achieved significantly longer short-axis diameters than RF ablations (P < 0.05). The highest tissue temperature was achieved with MW ablation at 45W (P < 0.05). On histological examination, the extent of the ablation zone in MW ablations was less affected by tissue heterogeneity than that in RF ablations. Conclusion: MW ablation appears to be advantageous with respect to the volume of ablation and the shape of the margin of necrosis compared with RF ablation in an ex vivo bovine udder.

Small-Scale Morphological Features on a Solid Surface Processed by High-Pressure Abrasive Water Jet

Directory of Open Access Journals (Sweden)

Can Kang

2013-08-01

Full Text Available Being subjected to a high-pressure abrasive water jet, solid samples will experience an essential variation of both internal stress and physical characteristics, which is closely associated with the kinetic energy attached to the abrasive particles involved in the jet stream. Here, experiments were performed, with particular emphasis being placed on the kinetic energy attenuation and turbulent features in the jet stream. At jet pressure of 260 MPa, mean velocity and root-mean-square (RMS velocity on two jet-stream sections were acquired by utilizing the phase Doppler anemometry (PDA technique. A jet-cutting experiment was then carried out with Al-Mg alloy samples being cut by an abrasive water jet. Morphological features and roughness on the cut surface were quantitatively examined through scanning electron microscopy (SEM and optical profiling techniques. The results indicate that the high-pressure water jet is characterized by remarkably high mean flow velocities and distinct velocity fluctuations. Those irregular pits and grooves on the cut surfaces indicate both the energy attenuation and the development of radial velocity components in the jet stream. When the sample is positioned with different distances from the nozzle outlet, the obtained quantitative surface roughness varies accordingly. A descriptive model highlighting the behaviors of abrasive particles in jet-cutting process is established in light of the experimental results and correlation analysis.

Small-Scale Morphological Features on a Solid Surface Processed by High-Pressure Abrasive Water Jet.

Science.gov (United States)

Kang, Can; Liu, Haixia

2013-08-14

Being subjected to a high-pressure abrasive water jet, solid samples will experience an essential variation of both internal stress and physical characteristics, which is closely associated with the kinetic energy attached to the abrasive particles involved in the jet stream. Here, experiments were performed, with particular emphasis being placed on the kinetic energy attenuation and turbulent features in the jet stream. At jet pressure of 260 MPa, mean velocity and root-mean-square (RMS) velocity on two jet-stream sections were acquired by utilizing the phase Doppler anemometry (PDA) technique. A jet-cutting experiment was then carried out with Al-Mg alloy samples being cut by an abrasive water jet. Morphological features and roughness on the cut surface were quantitatively examined through scanning electron microscopy (SEM) and optical profiling techniques. The results indicate that the high-pressure water jet is characterized by remarkably high mean flow velocities and distinct velocity fluctuations. Those irregular pits and grooves on the cut surfaces indicate both the energy attenuation and the development of radial velocity components in the jet stream. When the sample is positioned with different distances from the nozzle outlet, the obtained quantitative surface roughness varies accordingly. A descriptive model highlighting the behaviors of abrasive particles in jet-cutting process is established in light of the experimental results and correlation analysis.

Projectile Nose Mass Abrasion of High-Speed Penetration into Concrete

Directory of Open Access Journals (Sweden)

Haijun Wu

2012-01-01

Full Text Available Based on the dynamic spherical cavity expansion theory of concrete and the analysis of experimental data, a mass abrasion model of projectile considering the hardness of aggregates, the relative strength of target and projectile, and the initial impact velocity is constructed in this paper. Furthermore, the effect of mass abrasion on the penetration depth of projectile and the influence of hardness of aggregates and strength of projectile on penetration depth and mass loss are also analyzed. The results show that, for the ogive-nose projectile with the CRH of 3 and aspect ratio of 7 penetrating the concrete of 35 MPa, the “rigid-body penetration” model is available when the initial impact velocity is lower than 800 m/s. However, when the initial impact velocity is higher than 800 m/s, the “deforming/eroding body penetration” model should be adopted. Through theoretical analysis and numerical calculation, the results indicate that the initial impact velocity is the most important factor of mass abrasion. The hardness of aggregates and the strength of projectile are also significant factors. But relatively speaking, the sensitivity of strength of projectile to mass abrasion is higher, which indicates that the effect of projectile material on mass abrasion is more dramatic than the hardness of aggregates.

Self-modified quasi-stationary model for the radiation ablation

International Nuclear Information System (INIS)

Zhang Jun; Pei Wenbing; Gu Peijun; Sui Chengzhi; Chang Tieqiang

1996-01-01

The self-modified quasi-stationary model for radiation ablation has been established based on physical picture of numerical simulations. The objective of the model is to predict quantitatively the scaling laws of various ablation parameters driven by soft-X-ray, such as the dependence of ablation depth, pressure on radiation temperature, energy, pulse width, without resorting to complex computer simulations. The computational results are given for some interesting materials in ICF. Scaling laws obtained are simple and effective in target design and analysis of experimental results

Hydrodynamic model for ultra-short pulse ablation of hard dental tissue

Energy Technology Data Exchange (ETDEWEB)

London, R.A.; Bailey, D.S.; Young, D.A.; Alley, W.E.; Feit, M.D.; Rubenchik, A.M. [Lawrence Livermore National Lab., CA (United States); Neev, J. [Beckman Laser Inst., Irvine, CA (United States)

1996-02-29

A computational model for the ablation of tooth enamel by ultra-short laser pulses is presented. The role of simulations using this model in designing and understanding laser drilling systems is discussed. Pulses of duration 300 fsec and intensity greater than 10{sup 12} W/cm{sup 2} are considered. Laser absorption proceeds via multi-photon initiated plasma mechanism. The hydrodynamic response is calculated with a finite difference method, using an equation of state constructed from thermodynamic functions including electronic, ion motion, and chemical binding terms. Results for the ablation efficiency are presented. An analytic model describing the ablation threshold and ablation depth is presented. Thermal coupling to the remaining tissue and long-time thermal conduction are calculated. Simulation results are compared to experimental measurements of the ablation efficiency. Desired improvements in the model are presented.

Abrasion of Polymeric Composites on Basis of Machining Splinters from Hardfacing Alloys – Usable in Agrocomplex

Directory of Open Access Journals (Sweden)

Petr Valášek

2014-01-01

Full Text Available A paper focuses on a description of two-body and three-body abrasion wear of polymeric particle composites with fillers on a basis of machining splinters from hardfacing alloys. The abrasive wear is typical for functional surfaces of agricultural machines processing the soil. One of possibilities of the functional surface renovation is an application of resistant layers in a form of composite systems. Just the inclusion of hard inorganic particles into a polymeric matrix significantly increases its wear resistance. So long as the primary filler is replaced by the waste – by particles from the material machining – the matrix in which the filler is dispersed is a bearer of a material recyclation. This way of the recyclation is inexpensive, economic and sensitive to environment. The paper focuses on the experimental description of the two-body and three-body abrasion and the composites hardness, it describes a production of a prototype for field tests with the functional surface on the basis of the investigated composite system at the same time.

Abrasion Properties of Steel Fiber Reinforced Silica Fume Concrete According to Los Angeles and Water Abrasion Tests

Directory of Open Access Journals (Sweden)

Tsan-Ching CHENG

2014-12-01

Full Text Available The current study mainly investigated the influence of different tests on the abrasion resistance of concrete mixed with steel fibers and silica fume. The abrasion resistance was assessed at 28, 56 and 91 days on concretes with water-binder ratios of 0.35 and 0.55 where in some mixes silica fume was substituted by 5 % of cement by weight. Steel fibers of 0.5 % and 1.0 % of concrete volume were also added into the test concrete by replacement of coarse and fine aggregates. The results showed that concrete with higher compressive strength in Los Angeles abrasion tests also had better abrasion resistance. The inclusion of steel fibers into test concrete with a water-binder ratio of 0.35 resulted in a significant increase in compressive strength. This concrete also displayed better abrasion resistance and splitting tensile strength than reference concrete; in the test sample with a water-binder ratio of 0.55, the added steel fibers was unable to effectively produce cementation with the concrete. The inclusion of silica fume improved the abrasion resistance of concretes. In water abrasion testing, the abrasion resistance of concrete containing steel fiber was worse than that of concrete without steel fibers. In the water abrasion testing, the surface of steel fiber reinforced concrete was eroded by water and steel balls, and the impact caused the steel fibers to separate from the concrete and led to higher wear loss. DOI: http://dx.doi.org/10.5755/j01.ms.20.4.6460

Abrasive Wear of Four Direct Restorative Materials by Standard and Whitening Dentifrices

Science.gov (United States)

2013-06-01

Weader, E., Liscombe, C., & Holt, J.S. (2005). The measurement of enamel and dentine abrasion by tooth - whitening products using an in situ model...ABRASION OF TOOTH STRUCTURE Hard tissue abrasion is a familiar consequence of toothbrushing. Enamel , dentin, and cementum differ in their...LESIONS Cervical enamel wear is common; however, relatively few epidemiologic studies have distinguished between cervical enamel wear and tooth wear in

Usage of abrasion-resistant materials in agriculture

Directory of Open Access Journals (Sweden)

J Votava

2014-06-01

Full Text Available Agricultural soil-processing machines are subject to an extensive abrasive wear. This paper analyses technical materials and their fitness to exchangeable parts of plough bottoms, such as edge-tools and whole plough cutting edges. There were tested abrasion-resistant steels with different microstructures: austenite, martensite-bainite, and carbide. Steel with the pearlite-ferrite structure was used as an etalon. Abrasion resistance tests were processed in compliance with the norm CSN 01 5084, which is a test of abrasion wear on abrasive cloth.

Sustainability of abrasive processes

DEFF Research Database (Denmark)

Aurich, J.C.; Linke, B.; Hauschild, Michael Zwicky

2013-01-01

, the content of technical presentations in STC G, and the results of a comprehensive literature study. The approach to sustainability includes environmental, social, and economic sustainability in accordance with the definition proposed in the Brundtland Report of the United Nations [156]. The main focus......This paper presents an overview of research on sustainability of abrasive processes. It incorporates results from a round robin study on ‘‘energy-efficiency of abrasive processes’’ which has been carried out within the scientific technical committee ‘‘abrasive processes’’ (STC G) of CIRP...... is on environmental and social sustainability. Economic sustainability will be considered as manufacturing productivity. © 2013 CIRP....

Progress in abrasive and grinding technology

CERN Document Server

Xu, Xipeng

2009-01-01

The grinding and abrasive processing of materials are machining techniques which use bonded or loose abrasives to remove material from workpieces. Due to the well-known advantages of grinding and abrasive processes, advances in abrasive and grinding technology are always of great import in enhancing both productivity and component quality. In order to highlight the recent progress made in this field, the editor invited 21 world-wide contributions with the aim of gathering together all of the achievements of leading researchers into a single publication. The authors of the 21 invited papers, of

Properties, structure and machnining capabilities sintered corundum abrasives

Directory of Open Access Journals (Sweden)

Cz.J. Niżankowski

2010-07-01

Full Text Available The diversity of sintered corundum abrasives used in both bonded and in the embankment of abrasive tools currently poses substantialproblems for their choice of technology to specific tasks. Therefore performed a comparative study of ownership structures and capacitiesof elected representatives machnining sintered corundum abrasives of different generations, and this is normal sintered alumina,submicrocrystalline alumina sintered and nanocrystalline alumina sintered. Were studied some properties of a set of abrasive particles,physicochemical properties and structural and mechanical and technological properties. The studies used the method of microscopicmeasurement to determine the shape of abrasive particles, the pycnometer to determine the density of abrasive, a spectrometer todetermine the chemical composition of the magnetic analyzer for determining the magnetic fraction, scanning electron microscope toanalysis of abrasive grains and a special position to designate the machining capacity abrasive grains. The results showed a significantincrease in machining capacity sintered corundum abrasives with increasing degree of fragmentation of the crystallites sintered corundum abrasives and distinctive bands in the emerging microchip. The originality of the development provides a comparative summary ofproperties of sintered corundum abrasives of different generations and functions obtained by the author making the change in value indexof machininhcapacity grit from cutting speeds for different generations of sintered corundum.

Numerical analysis of special-shaped surface in abrasive flow machining

Science.gov (United States)

Li, Junye; Zhou, Zengwei; Wu, Guiling; Lu, Hui; Sun, Zhihuai

2018-03-01

Solid-liquid two-phase abrasive flow machining is a method to effectively polish the surface of Special-shaped surface parts. Based on the processing characteristics of the abrasive flow machining. The standard model and the pressure-coupled SIMPLEC algorithm are used. The shear force and velocity of the near-wall surface of the runner of the solid-liquid two-phase abrasive machining with different inlet pressure are analyzed. The numerical simulation results show that the inlet pressure has little effect on the velocity, and the shear force has a linear relationship with the inlet pressure. To obtain a better polishing effect, the outlet pressure can be appropriately increased.

Benign thyroid nodule unresponsive to radiofrequency ablation treated with laser ablation: a case report.

Science.gov (United States)

Oddo, Silvia; Balestra, Margherita; Vera, Lara; Giusti, Massimo

2018-05-11

Radiofrequency ablation and laser ablation are safe and effective techniques for reducing thyroid nodule volume, neck symptoms, and cosmetic complaints. Therapeutic success is defined as a nodule reduction > 50% between 6 and 12 months after the procedure, but a percentage of nodules inexplicably do not respond to thermal ablation. We describe the case of a young Caucasian woman with a solid benign thyroid nodule who refused surgery and who had undergone radiofrequency ablation in 2013. The nodule did not respond in terms of either volume reduction or improvement in neck symptoms. After 2 years, given the patient's continued refusal of thyroidectomy, we proposed laser ablation. The nodule displayed a significant volume reduction (- 50% from radiofrequency ablation baseline volume, - 57% from laser ablation baseline), and the patient reported a significant improvement in neck symptoms (from 6/10 to 1/10 on a visual analogue scale). We conjecture that some benign thyroid nodules may be intrinsically resistant to necrosis when one specific ablation technique is used, but may respond to another technique. To the best of our knowledge, this is the first description of the effect of performing a different percutaneous ablation technique in a nodule that does not respond to radiofrequency ablation.

Study on design of light-weight super-abrasive wheel

Science.gov (United States)

Nohara, K.; Yanagihara, K.; Ogawa, M.

2018-01-01

Fixed-abrasive tool, also called a grinding wheel, is produced by furnacing abrasive compound which contains abrasive grains and binding powder such as vitrified materials or resins. Fixed-abrasive tool is installed on spindle of grinding machine. And it is given 1,800-2,000 min-1 of spindle rotation for the usage. The centrifugal fracture of the compound of fixed- abrasive tool is one of the careful respects in designing. In recent years, however, super-abrasive wheel as a fixed-abrasive tool has been developed and applied widely. One of the most characteristic respects is that metal is applied for the body of grinding-wheel. The strength to hold abrasive grain and the rigidity of wheel become stronger than those of general grinding wheel, also the lifespan of fixed-abrasive tool becomes longer. The weight of fixed-abrasive tool, however, becomes heavier. Therefore, when the super-abrasive wheel is used, the power consumption of spindle motor becomes larger. It also becomes difficult for the grinding-wheel to respond to sudden acceleration or deceleration. Thus, in order to reduce power consumption in grinding and to obtain quicker frequency response of super-abrasive wheel, the new wheel design is proposed. The design accomplishes 46% weight reduction. Acceleration that is one second quicker than that of conventional grinding wheel is obtained.

A thermal model for nanosecond pulsed laser ablation of aluminum

Directory of Open Access Journals (Sweden)

Yu Zhang

2017-07-01

Full Text Available In order to simulate the nanosecond pulsed laser ablation of aluminum, a novel model was presented for the target ablation and plume expansion. The simulation of the target ablation was based on one-dimensional heat conduction, taking into account temperature dependent material properties, phase transition, dielectric transition and phase explosion. While the simulation of the plume expansion was based on one-dimensional gas-dynamical equation, taking into account ionization, plume absorption and shielding. By coupling the calculations of the target ablation and plume expansion, the characteristics of the target and plume were obtained. And the calculated results were in good agreement with the experimental data, in terms of ablation threshold and depth within the fluence range of the tested laser. Subsequently, investigations were carried out to analyze the mechanisms of nanosecond pulsed laser ablation. The calculated results showed that the maximum surface temperature remained at about 90% of the critical temperature (0.9Tc due to phase explosion. Moreover, the plume shielding has significant effects on the laser ablation, and the plume shielding proportion increase as the laser fluence increasing. The ambient pressure belows 100 Pa is more suitable for laser ablation, which can obtained larger ablation depth.

On the abrasion of heat-treated 2.8C21Cr1Mo white cast iron

Energy Technology Data Exchange (ETDEWEB)

Al-Rubaie, Kassim S.; Preti, Orlando [Centro Universitario SOCIESC, Joinville (Brazil). Engenharia Mecanica; Pohl, Michael [Bochum Univ. (Germany). Inst. fuer Werkstoffe

2016-09-15

The abrasion behaviour of heat-treated 2.8C21Cr1Mo cast iron was studied. The specimens were destabilised at two temperatures, 980 and 1050 C, for 4 h, air hardened, and then tempered at five temperatures, 220, 320, 400, 500, and 620 C, for 2 h followed by air cooling. Using a pin-on-plate abrasion apparatus, the specimens were abraded on four types of bonded abrasives (silicon carbide, corundum, flint, and glass). The effect of work hardening on the abrasion resistance was investigated. It was found that the increase in alloy hardness produced by heat treatment had little effect on the abrasion resistance against silicon carbide or corundum; the inverse was true against flint or glass. The as-hardened structure containing 40% retained austenite gave the best abrasion resistance, whereas the hardened and tempered at 620 C showed the worst. Both bulk hardness and matrix hardness before wear correlated poorly with the abrasion resistance. Therefore, a general model ''equivalent hardness'' was developed, in which the hardness of the abraded matrix was considered. With this model, the abrasion behaviour can be clearly analysed.

Effect of nanofillers' size on surface properties after toothbrush abrasion.

Science.gov (United States)

Cavalcante, Larissa M; Masouras, Konstantinos; Watts, David C; Pimenta, Luiz A; Silikas, Nick

2009-02-01

To investigate the effect of filler-particle size of experimental and commercial resin composites, undergoing toothbrush abrasion, on three surface properties: surface roughness (SR), surface gloss (G) and color stability (CS). Four model (Ivoclar/Vivadent) and one commercial resin composite (Tokuyama) with varying filler-size from 100-1000 nm were examined. Six discs (10 mm x 2 mm) from each product were prepared and mechanically polished. The samples were then submitted to 20,000 brushing strokes in a toothbrush abrasion machine. SR parameters (Ra, Rt and RSm), G, and CS were measured before and after toothbrush abrasion. Changes in SR and G were analyzed by 2-way ANOVA, with Bonferroni post hoc test. CS values were submitted to one-way ANOVA and Bonferroni post hoc test (alpha=0.05). Initial G values ranged between 73-87 gloss units (GU) and were reduced after toothbrush abrasion to a range of 8-64 GU. Toothbrush abrasion resulted in significant modifications in SR and G amongst the materials tested, attributed to filler sizes. There was statistically significant difference in color (delta E* ranged from 0.38-0.88). Filler size did not affect color stability. Toothbrush abrasion resulted in rougher and matte surfaces for all materials tested. Although the individual differences in surface roughness among filler sizes were not always significant, the correlation showed a trend that larger filler sizes resulted in higher surface roughness after abrasion for the SR parameters Ra and Rt (r = 0.95; r = 0.93, respectively). RSm showed an increase after toothbrush abrasion for all resin composites, however no significant correlation was detected (r = 0.21).There was a significant correlation between G and Ra ratios (r = - 0.95).

Modeling of plasma distortions by laser-induced ablation spectroscopy (LIAS) and implications for the interpretation of LIAS measurements

Science.gov (United States)

Tokar, M. Z.; Gierse, N.; Philipps, V.; Samm, U.

2015-09-01

For the interpretation of the line radiation observed from laser induced ablation spectroscopy (LIAS) such parameters as the density and temperature of electrons within very compact clouds of atoms and singly charged ions of ablated material have to be known. Compared to the local plasma conditions prior to the laser pulse, these can be strongly changed during LIAS since new electrons are generated by the ionisation of particles ejected from the irradiated target. Because of their transience and spatial inhomogeneity it is technically difficult to measure disturbances induced in the plasma by LIAS. To overcome this uncertainty a numerical model has been elaborated, providing a self-consistent description for the spreading of ablated particles and accompanying modifications in the plasma. The results of calculations for LIAS performed on carbon-containing targets in Ohmic and additionally heated discharges in the tokamak TEXTOR are presented. Due to the increase in the electron density the ‘ionisation per photon’ ratio, S/XB factor, is significantly enhanced compared to unperturbed plasma conditions. The impact of the amount of material ablated and of the plasma conditions before LIAS on the level of the S/XB-enhancement is investigated.

Implementation of Radiation, Ablation, and Free Energy Minimization Modules for Coupled Simulations of Hypersonic Flow

Science.gov (United States)

Gnoffo, Peter A.; Johnston, Christopher O.; Thompson, Richard A.

2009-01-01

A description of models and boundary conditions required for coupling radiation and ablation physics to a hypersonic flow simulation is provided. Chemical equilibrium routines for varying elemental mass fraction are required in the flow solver to integrate with the equilibrium chemistry assumption employed in the ablation models. The capability also enables an equilibrium catalytic wall boundary condition in the non-ablating case. The paper focuses on numerical implementation issues using FIRE II, Mars return, and Apollo 4 applications to provide context for discussion. Variable relaxation factors applied to the Jacobian elements of partial equilibrium relations required for convergence are defined. Challenges of strong radiation coupling in a shock capturing algorithm are addressed. Results are presented to show how the current suite of models responds to a wide variety of conditions involving coupled radiation and ablation.

Cleaning power and abrasivity of European toothpastes.

Science.gov (United States)

Wülknitz, P

1997-11-01

For 41 toothpastes available to European consumers in 1995, the cleaning efficacy was evaluated in comparison with abrasivity on dentin (RDA value). For cleaning power assessment, a modified pellicle cleaning ratio (PCR) measurement method was developed. The method is characterized by a five-day tea-staining procedure on bovine front teeth slabs on a rotating wheel, standardized brushing of the slabs in a V8 cross-brushing machine, and brightness measurement by a chromametric technique. All tested products were in accordance with the new DIN/ISO standard 11,609 for toothpastes in terms of dentin abrasivity. Not a single product exceeded an RDA value of 200. The majority of toothpastes (80%) had an RDA value below 100. Only three products surpassed the reference in cleaning power. Most products (73%) had a cleaning power (PCR value) between 20 and 80. The correlation between cleaning power and dentin abrasion was low (r = 0.66), which can be explained with the different influence on dentin and stains by factors like abrasive type, particle surface and size, as well as the chemical influence of other toothpaste ingredients. Some major trends could be shown on the basis of abrasive types. The ratio PCR to RDA was rather good in most silica-based toothpastes. A lower ratio was found in some products containing calcium carbonate or aluminum trihydrate as the only abrasive. The addition of other abrasives, such as polishing alumina, showed improved cleaning power. Some active ingredients, especially sequenstrants such as sodium tripolyphosphate or AHBP, also improve the PCR/RDA ratio by stain-dissolving action without being abrasive. The data for some special anti-stain products did not differ significantly from standard products. Compared with data measured in 1988, a general trend toward reduced abrasivity without loss of cleaning efficacy could be noticed on the European toothpaste market. This may be mostly due to the increased use of high-performance abrasives such

Ceramic-bonded abrasive grinding tools

Science.gov (United States)

Holcombe, Jr., Cressie E.; Gorin, Andrew H.; Seals, Roland D.

1994-01-01

Abrasive grains such as boron carbide, silicon carbide, alumina, diamond, cubic boron nitride, and mullite are combined with a cement primarily comprised of zinc oxide and a reactive liquid setting agent and solidified into abrasive grinding tools. Such grinding tools are particularly suitable for grinding and polishing stone, such as marble and granite.

Ceramic-bonded abrasive grinding tools

Science.gov (United States)

Holcombe, C.E. Jr.; Gorin, A.H.; Seals, R.D.

1994-11-22

Abrasive grains such as boron carbide, silicon carbide, alumina, diamond, cubic boron nitride, and mullite are combined with a cement primarily comprised of zinc oxide and a reactive liquid setting agent and solidified into abrasive grinding tools. Such grinding tools are particularly suitable for grinding and polishing stone, such as marble and granite.

Microwave Ablation: Comparison of Simultaneous and Sequential Activation of Multiple Antennas in Liver Model Systems.

Science.gov (United States)

Harari, Colin M; Magagna, Michelle; Bedoya, Mariajose; Lee, Fred T; Lubner, Meghan G; Hinshaw, J Louis; Ziemlewicz, Timothy; Brace, Christopher L

2016-01-01

To compare microwave ablation zones created by using sequential or simultaneous power delivery in ex vivo and in vivo liver tissue. All procedures were approved by the institutional animal care and use committee. Microwave ablations were performed in both ex vivo and in vivo liver models with a 2.45-GHz system capable of powering up to three antennas simultaneously. Two- and three-antenna arrays were evaluated in each model. Sequential and simultaneous ablations were created by delivering power (50 W ex vivo, 65 W in vivo) for 5 minutes per antenna (10 and 15 minutes total ablation time for sequential ablations, 5 minutes for simultaneous ablations). Thirty-two ablations were performed in ex vivo bovine livers (eight per group) and 28 in the livers of eight swine in vivo (seven per group). Ablation zone size and circularity metrics were determined from ablations excised postmortem. Mixed effects modeling was used to evaluate the influence of power delivery, number of antennas, and tissue type. On average, ablations created by using the simultaneous power delivery technique were larger than those with the sequential technique (P Simultaneous ablations were also more circular than sequential ablations (P = .0001). Larger and more circular ablations were achieved with three antennas compared with two antennas (P simultaneous power delivery creates larger, more confluent ablations with greater temperatures than those created with sequential power delivery. © RSNA, 2015.

Determination of vibration frequency depending on abrasive mass flow rate during abrasive water jet cutting

Czech Academy of Sciences Publication Activity Database

Hreha, P.; Radvanská, A.; Hloch, Sergej; Peržel, V.; Krolczyk, G.; Monková, K.

2014-01-01

Roč. 77, 1-4 (2014), s. 763-774 ISSN 0268-3768 Institutional support: RVO:68145535 Keywords : Abrasive water jet * Abrasive mass flow rate * Vibration Subject RIV: JQ - Machines ; Tools Impact factor: 1.458, year: 2014 http://link.springer.com/article/10.1007%2Fs00170-014-6497-9#page-1

Modeling of beam-target interaction during pulsed electron beam ablation of graphite: Case of melting

Energy Technology Data Exchange (ETDEWEB)

Ali, Muddassir, E-mail: mx1_ali@laurentian.ca; Henda, Redhouane

2017-02-28

Highlights: • Modeling of ablation stage induced during pulsed electron beam ablation (PEBA). • Thermal model to describe heating, melting and vaporization of a graphite target. • Model results show good accordance with reported data in the literature. - Abstract: A one-dimensional thermal model based on a two-stage heat conduction equation is employed to investigate the ablation of graphite target during nanosecond pulsed electron beam ablation. This comprehensive model accounts for the complex physical phenomena comprised of target heating, melting and vaporization upon irradiation with a polyenergetic electron beam. Melting and vaporization effects induced during ablation are taken into account by introducing moving phase boundaries. Phase transition induced during ablation is considered through the temperature dependent thermodynamic properties of graphite. The effect of electron beam efficiency, power density, and accelerating voltage on ablation is analyzed. For an electron beam operating at an accelerating voltage of 15 kV and efficiency of 0.6, the model findings show that the target surface temperature can reach up to 7500 K at the end of the pulse. The surface begins to melt within 25 ns from the pulse start. For the same process conditions, the estimated ablation depth and ablated mass per unit area are about 0.60 μm and 1.05 μg/mm{sup 2}, respectively. Model results indicate that ablation takes place primarily in the regime of normal vaporization from the surface. The results obtained at an accelerating voltage of 15 kV and efficiency factor of 0.6 are satisfactorily in good accordance with available experimental data in the literature.

Laser ablation under different electron heat conduction models in inertial confinement fusion

Science.gov (United States)

Li, Shuanggui; Ren, Guoli; Huo, Wen Yi

2018-06-01

In this paper, we study the influence of three different electron heat conduction models on the laser ablation of gold plane target. Different from previous studies, we concentrate on the plasma conditions, the conversion efficiency from laser into soft x rays and the scaling relation of mass ablation, which are relevant to hohlraum physics study in indirect drive inertial confinement fusion. We find that the simulated electron temperature in corona region is sensitive to the electron heat conduction models. For different electron heat conduction models, there are obvious differences in magnitude and spatial profile of electron temperature. For the flux limit model, the calculated conversion efficiency is sensitive to flux limiters. In the laser ablation of gold, most of the laser energies are converted into x rays. So the scaling relation of mass ablation rate is quite different from that of low Z materials.

Mathematical model of temperature field distribution in thin plates during polishing with a free abrasive

Directory of Open Access Journals (Sweden)

Avilov Alex

2017-01-01

Full Text Available The purpose of this paper is to estimate the dynamic characteristics of the heating process of thin plates during polishing with a free abrasive. A mathematical model of the temperature field distribution in space and time according to the plate thickness is based on Lagrange equation of the second kind in the thermodynamics of irreversible processes (variation principle Bio. The research results of thermo elasticity of thin plates (membranes will allow to correct the modes of polishing with a free abrasive to receive the exact reflecting surfaces of satellites reflector, to increase temperature stability and the ability of radio signal reflection, satellite precision guidance. Calculations of temperature fields in thin plates of different thicknesses (membranes is held in the Excel, a graphical characteristics of temperature fields in thin plates (membranes show non-linearity of temperature distribution according to the thickness of thin plates (membranes.

Modelling detrital coral grain-size and age: Insights from sediment abrasion process of Yongle Atoll of South China Sea

Science.gov (United States)

Li, Y.; Zou, X.; Ge, C.; Tan, M.; Wang, C.

2017-12-01

Reef islands situated on the rims of atolls are composed almost exclusively of bioclastic materials locally supplied from adjacent coral reefs. Major skeletal component of these islands include coral, coralline algae, mollusks and foraminifera, produced in adjacent reefs. As the island builder, the bioclastic material is the sedimentary products, which also is the point of penetration to decipher the process. The bioclast of coral islands decrease in size with the transportation process. The grain-size provides a proxy record for the abrasion history of the unconsolidated sediment. The 230Th age of coral record the abrasion time. We hereby present a model to calculate the abrasion rate based on the data of 230Th age and grain-size of Yongle Atoll of Xisha Island, South China Sea. The grain size pattern in Yongle Atoll environment have confirm that the coral article diminution behave exponentially. The sediment composition of Yongle Atoll is identified, coral is dominant sediment constituent and the Th230 age is shown to exert an age distribution characteristics of coral detritus. We illustrate this approach by calculate the coral debris age of Xude Atoll, which located near the Yongle Atoll and then by comparing actual measured age and calculated age and to explore the dependence of the model. Observed 230 Th ages are well matched by predicted ages for medium age sediment. A poorer match for young and old sediment may result from some combination of large analytical uncertainties in the detrital ages and inhomogeneous erosion rates within the atoll. Such mismatches emphasize the need for more accurate kinematic models and for sampling strategies that are adapted to atoll-specific geologic and geomorphic conditions. Results presented constitute important new insights into regional sediment abrasion processed and on the evolution of coral atoll islands.

Dynamics and stability of radiation-driven double ablation front structures

International Nuclear Information System (INIS)

Drean, V.; Olazabal-Loume, M.; Tikhonchuk, V. T.; Sanz, J.

2010-01-01

The dynamics of double ablation front (DAF) structures is studied for planar targets with moderate atomic number ablators. These structures are obtained in hydrodynamic simulations for various materials and laser intensities and are qualitatively characterized during the acceleration stage of the target. The importance of the radiative transport for the DAF dynamics is then demonstrated. Simulated hydrodynamic profiles are compared with a theoretical model, showing the consistency of the model and the relevant parameters for the dynamics description. The stability of DAF structures with respect to two-dimensional perturbations is studied using two different approaches: one considers the assumptions of the theoretical model and the other one a more complete physics. The numerical simulations performed with both approaches demonstrate good agreement of dispersion curves.

Ultrasonic Abrasive Removal Of EDM Recast

Science.gov (United States)

Mandel, Johnny L.; Jacobson, Marlowe S.

1990-01-01

Ultrasonic abrasive process removes layer of recast material generated during electrical-discharge machining (EDM) of damper pocket on turbine blade. Form-fitted tool vibrated ultrasonically in damper pocket from which material removed. Vibrations activate abrasive in pocket. Amount of material removed controlled precisely.

Computational Modeling of Ablation on an Irradiated Target

Science.gov (United States)

Mehmedagic, Igbal; Thangam, Siva

2017-11-01

Computational modeling of pulsed nanosecond laser interaction with an irradiated metallic target is presented. The model formulation involves ablation of the metallic target irradiated by pulsed high intensity laser at normal atmospheric conditions. Computational findings based on effective representation and prediction of the heat transfer, melting and vaporization of the targeting material as well as plume formation and expansion are presented along with its relevance for the development of protective shields. In this context, the available results for a representative irradiation from 1064 nm laser pulse is used to analyze various ablation mechanisms, variable thermo-physical and optical properties, plume expansion and surface geometry. Funded in part by U. S. Army ARDEC, Picatinny Arsenal, NJ.

Enthalpy model for heating, melting, and vaporization in laser ablation

OpenAIRE

Vasilios Alexiades; David Autrique

2010-01-01

Laser ablation is used in a growing number of applications in various areas including medicine, archaeology, chemistry, environmental and materials sciences. In this work the heat transfer and phase change phenomena during nanosecond laser ablation of a copper (Cu) target in a helium (He) background gas at atmospheric pressure are presented. An enthalpy model is outlined, which accounts for heating, melting, and vaporization of the target. As far as we know, this is the first model th...

A plasma model combined with an improved two-temperature equation for ultrafast laser ablation of dielectrics

International Nuclear Information System (INIS)

Jiang Lan; Tsai, H.-L.

2008-01-01

It remains a big challenge to theoretically predict the material removal mechanism in femtosecond laser ablation. To bypass this unresolved problem, many calculations of femtosecond laser ablation of nonmetals have been based on the free electron density distribution without the actual consideration of the phase change mechanism. However, this widely used key assumption needs further theoretical and experimental confirmation. By combining the plasma model and improved two-temperature model developed by the authors, this study focuses on investigating ablation threshold fluence, depth, and shape during femtosecond laser ablation of dielectrics through nonthermal processes (the Coulomb explosion and electrostatic ablation). The predicted ablation depths and shapes in fused silica, by using (1) the plasma model only and (2) the plasma model plus the two-temperature equation, are both in agreement with published experimental data. The widely used assumptions for threshold fluence, ablation depth, and shape in the plasma model based on free electron density are validated by the comparison study and experimental data

Experimental Evidence that Abrasion of Carbonate Sand is a Significant Source of Carbonate Mud

Science.gov (United States)

Trower, L.; Kivrak, L.; Lamb, M. P.; Fischer, W. W.

2017-12-01

Carbonate mud is a major sedimentary component of modern and ancient tropical carbonate environments, yet its enigmatic origin remains debated. Early views on the origin of carbonate mud considered the abrasion of carbonate sand during sediment transport as a possible mechanism. In recent decades, however, prevailing thought has generally settled on a binary explanation: 1) precipitation of aragonite needles within the water column, and 2) post-mortem dispersal of biological aragonite, in particular from algae, and perhaps aided by fish. To test these different hypotheses, we designed a model and a set of laboratory experiments to quantify the rates of mud production associated with sediment transport. We adapted a recent model of ooid abrasion rate to predict the rate of mud production by abrasion of carbonate sand as a function of grain size and sediment transport mode. This model predicts large mud production rates, ranging from 103 to 104 g CaCO3/m2/yr for typical grain sizes and transport conditions. These rate estimates are at least one order of magnitude more rapid than the 102 g CaCO3/m2/yr estimates for other mechanisms like algal biomineralization, indicating that abrasion could produce much larger mud fluxes per area as other mechanisms. We tested these estimates using wet abrasion mill experiments; these experiments generated mud through mechanical abrasion of both ooid and skeletal carbonate sand for grain sizes ranging from 250 µm to >1000 µm over a range of sediment transport modes. Experiments were run in artificial seawater, including a series of controls demonstrating that no mud was produced via homogenous nucleation and precipitation in the absence of sand. Our experimental rates match the model predictions well, although we observed small systematic differences in rates between abrasion ooid sand and skeletal carbonate sand that likely stems from innate differences in grain angularity. Electron microscopy of the experimental products revealed

New Rock Abrasivity Test Method for Tool Life Assessments on Hard Rock Tunnel Boring: The Rolling Indentation Abrasion Test (RIAT)

Science.gov (United States)

Macias, F. J.; Dahl, F.; Bruland, A.

2016-05-01

The tunnel boring machine (TBM) method has become widely used and is currently an important presence within the tunnelling industry. Large investments and high geological risk are involved using TBMs, and disc cutter consumption has a great influence on performance and cost, especially in hard rock conditions. Furthermore, reliable cutter life assessments facilitate the control of risk as well as avoiding delays and budget overruns. Since abrasive wear is the most common process affecting cutter consumption, good laboratory tests for rock abrasivity assessments are needed. A new abrasivity test method by rolling disc named Rolling Indentation Abrasion Test (RIAT) has been developed. The goal of the new test design and procedure is to reproduce wear behaviour on hard rock tunnel boring in a more realistic way than the traditionally used methods. Wear by rolling contact on intact rock samples is introduced and several rock types, covering a wide rock abrasiveness range, have been tested by RIAT. The RIAT procedure indicates a great ability of the testing method to assess abrasive wear on rolling discs. In addition and to evaluate the newly developed RIAT test method, a comprehensive laboratory testing programme including the most commonly used abrasivity test methods and the mineral composition were carried out. Relationships between the achieved results from conventional testing and RIAT results have been analysed.

A method for increase abrasive wear resistance parts by obtaining on methods casting on gasifying models

Science.gov (United States)

Sedukhin, V. V.; Anikeev, A. N.; Chumanov, I. V.

2017-11-01

Method optimizes hardening working layer parts’, working in high-abrasive conditions looks in this work: bland refractory particles WC and TiC in respect of 70/30 wt. % prepared by beforehand is applied on polystyrene model in casting’ mould. After metal poured in mould, withstand for crystallization, and then a study is carried out. Study macro- and microstructure received samples allows to say that thickness and structure received hardened layer depends on duration interactions blend harder carbides and liquid metal. Different character interactions various dispersed particles and matrix metal observed under the same conditions. Tests abrasive wear resistance received materials of method calculating residual masses was conducted in laboratory’ conditions. Results research wear resistance showed about that method obtaining harder coating of blend carbide tungsten and carbide titanium by means of drawing on surface foam polystyrene model before moulding, allows receive details with surface has wear resistance in 2.5 times higher, than details of analogy steel uncoated. Wherein energy costs necessary for transformation units mass’ substances in powder at obtained harder layer in 2.06 times higher, than materials uncoated.

Experimental Rock-on-Rock Abrasive Wear Under Aqueous Conditions: its Role in Subglacial Abrasion

Science.gov (United States)

Rutter, E. H.; Lee, A. G.

2003-12-01

We have determined experimentally the rate of abrasive wear of rock on rock for a range of rock types as a function of normal stress and shear displacement. Unlike abrasive wear in fault zones, where wear products accumulate as a thickening gouge zone, in our experiments wear particles were removed by flowing water. The experiments are thus directly pertinent to one of the most important processes in subglacial erosion, and to some extent in river incision. Wear was produced between rotating discs machined from rock samples and measured from the progressive approach of the disc axes towards each other under various levels of normal load. Shear displacements of several km were produced. Optical and scanning electron microscopy were used to study the worn rock surfaces, and particle size distributions in wear products were characterized using a laser particle size analyzer. Rock types studied were sandstones of various porosities and cement characteristics, schists and a granite. In all cases abrasion rate decreased logarithmically with displacement by up to 2 orders of magnitude until a steady state was approached, but only after at least 1 km displacement. The more porous, less-well cemented rocks wore fastest. Amount of abrasion could be characterized quantitatively using an exponentially decaying plus a steady-state term. Wear rate increased non-linearly with normal contact stress, apparently to an asymptote defined by the unconfined compressive strength. Microstructural study showed that the well-cemented and/or lowest porosity rocks wore by progressive abrasion of grains without plucking, whereas whole grains were plucked out of weakly-cemented and/or more porous rocks. This difference in behavior was reflected in wear-product particle size distributions. Where whole-grain plucking was possible, wear products were dominated by particles of the original grain size rather than finer rock flour. Comparison of our results to glacier basal abrasive wear estimated

Recent Developments in Abrasive Hybrid Manufacturing Processes

Directory of Open Access Journals (Sweden)

Ruszaj Adam

2017-06-01

Full Text Available Recent dynamic development of abrasive hybrid manufacturing processes results from application of a new difficult for machining materials and improvement of technological indicators of manufacturing processes already applied in practice. This tendency also occurs in abrasive machining processes which are often supported by ultrasonic vibrations, electrochemical dissolution or by electrical discharges. In the paper we present the review of new results of investigations and new practical applications of Abrasive Electrodischarge (AEDM and Electrochemical (AECM Machining.

An experimental modeling and acoustic emission monitoring of abrasive wear in a steel/diabase pair

Science.gov (United States)

Korchuganov, M. A.; Filippov, A. V.; Tarasov, S. Yu.; Podgornyh, O. A.; Shamarin, N. N.; Filippova, E. O.

2016-11-01

The earthmoving of permafrost soil is a critical task for excavation of minerals and construction on new territories. Failure by abrasive wear is the main reason for excavation parts of earthmoving and soil cutting machines. Therefore investigation of this type of wear is a challenge for developing efficient and wear resistant working parts. This paper is focused on conducting tribological experiments with sliding the steel samples over the surface of diabase stone sample where abrasive wear conditions of soil cutting are modeled experimentally. The worn surfaces of all samples have been examined and transfer of metal and stone particles revealed. The acoustic emission (AE) signals have been recorded and related to the results of worn surface analysis. he acoustic emission (AE) signals have been recorded and related to the results of worn surface analysis. As shown the wear intensity correlates to that of acoustic emission. Both acoustic emission signal median frequency and energy are found to be sensitive to the wear mode.

Sandstone Turning by Abrasive Waterjet

Czech Academy of Sciences Publication Activity Database

Hlaváček, Petr; Cárach, J.; Hloch, Sergej; Vasilko, K.; Klichová, Dagmar; Klich, Jiří; Lehocká, D.

2015-01-01

Roč. 48, č. 6 (2015), s. 2489-2493 ISSN 0723-2632 R&D Projects: GA MŠk ED2.1.00/03.0082; GA MŠk(CZ) LO1406 Institutional support: RVO:68145535 Keywords : turning away from the jet * conventional turning towards the jet * sandstone * abrasive water jet Subject RIV: JQ - Machines ; Tools Impact factor: 2.386, year: 2015 http://www.springerprofessional.de/sandstone-turning-by-abrasive-waterjet/6038028.html

Comparing the Air Abrasion Cutting Efficacy of Dentine Using a Fluoride-Containing Bioactive Glass versus an Alumina Abrasive: An In Vitro Study

Directory of Open Access Journals (Sweden)

Melissa H. X. Tan

2015-01-01

Full Text Available Air abrasion as a caries removal technique is less aggressive than conventional techniques and is compatible for use with adhesive restorative materials. Alumina, while being currently the most common abrasive used for cutting, has controversial health and safety issues and no remineralisation properties. The alternative, a bioactive glass, 45S5, has the advantage of promoting hard tissue remineralisation. However, 45S5 is slow as a cutting abrasive and lacks fluoride in its formulation. The aim of this study was to compare the cutting efficacy of dentine using a customised fluoride-containing bioactive glass Na0SR (38–80 μm versus the conventional alumina abrasive (29 μm in an air abrasion set-up. Fluoride was incorporated into Na0SR to enhance its remineralisation properties while strontium was included to increase its radiopacity. Powder outflow rate was recorded prior to the cutting tests. Principal air abrasion cutting tests were carried out on pristine ivory dentine. The abrasion depths were quantified and compared using X-ray microtomography. Na0SR was found to create deeper cavities than alumina (p<0.05 despite its lower powder outflow rate and predictably reduced hardness. The sharper edges of the Na0SR glass particles might improve the cutting efficiency. In conclusion, Na0SR was more efficacious than alumina for air abrasion cutting of dentine.

Life cycle and sustainability of abrasive tools

CERN Document Server

Linke, Barbara

2016-01-01

This monograph focuses on abrasive tools for grinding, polishing, honing, and lapping operations. The book describes the life cycle of abrasive tools from raw material processing of abrasive grits and bonding, manufacturing of monolithic or multi-layered tools, tool use to tool end-of-life. Moreover, this work highlights sustainability challenges including economic, environmental, social and technological aspects. The target audience primarily comprises research and industry experts in the field of manufacturing, but the book may also be beneficial for graduate students.

Anti-abrasive nanocoatings current and future applications

CERN Document Server

2015-01-01

This book provides an overview of the fabrication methods for anti-abrasive nanocoatings. The connections among fabrication parameters, the characteristics of nanocoatings and the resulting properties (i.e. nanohardness, toughness, wear rate, load-bearing ability, friction coefficient, and scratch resistance) are discussed. Size-affected mechanical properties of nanocoatings are examined, including their uses. Anti-abrasive nanocoatings, including metallic-, ceramic-, and polymeric-based layers, as well as different kinds of nanostructures, such as multi-layered nanocomposites and thin films, are reviewed. * Provides a comprehensive overview of the fabrication methods for anti-abrasive nanocoatings* Discusses the connections among fabrication parameters, the characteristics of nanocoatings and the resulting properties* Reviews advantages and drawbacks of fabrication methods for anti-abrasive nanocoatings and clarifies the place of these nanocoatings in the world of nanotechnology

Neural network approximation of tip-abrasion effects in AFM imaging

International Nuclear Information System (INIS)

Bakucz, Peter; Dziomba, Thorsten; Koenders, Ludger; Krüger-Sehm, Rolf; Yacoot, Andrew

2008-01-01

The abrasion (wear) of tips used in scanning force microscopy (SFM) directly influences SFM image quality and is therefore of great relevance to quantitative SFM measurements. The increasing implementation of automated SFM measurement schemes has become a strong driving force for increasing efforts towards the prediction of tip wear, as it needs to be ensured that the probe is exchanged before a level of tip wear is reached that adversely affects the measurement quality. In this paper, we describe the identification of tip abrasion in a system of SFM measurements. We attempt to model the tip-abrasion process as a concatenation of a mapping from the measured AFM data to a regression vector and a nonlinear mapping from the regressor space to the output space. The mapping is formed as a basis function expansion. Feedforward neural networks are used to approximate this mapping. The one-hidden layer network gave a good quality of fit for the training and test sets for the tip-abrasion system. We illustrate our method with AFM measurements of both fine periodic structures and randomly oriented sharp features and compare our neural network results with those obtained using other methods

Neural network approximation of tip-abrasion effects in AFM imaging

Science.gov (United States)

Bakucz, Peter; Yacoot, Andrew; Dziomba, Thorsten; Koenders, Ludger; Krüger-Sehm, Rolf

2008-06-01

The abrasion (wear) of tips used in scanning force microscopy (SFM) directly influences SFM image quality and is therefore of great relevance to quantitative SFM measurements. The increasing implementation of automated SFM measurement schemes has become a strong driving force for increasing efforts towards the prediction of tip wear, as it needs to be ensured that the probe is exchanged before a level of tip wear is reached that adversely affects the measurement quality. In this paper, we describe the identification of tip abrasion in a system of SFM measurements. We attempt to model the tip-abrasion process as a concatenation of a mapping from the measured AFM data to a regression vector and a nonlinear mapping from the regressor space to the output space. The mapping is formed as a basis function expansion. Feedforward neural networks are used to approximate this mapping. The one-hidden layer network gave a good quality of fit for the training and test sets for the tip-abrasion system. We illustrate our method with AFM measurements of both fine periodic structures and randomly oriented sharp features and compare our neural network results with those obtained using other methods.

Abrasive wear of intermetallics

International Nuclear Information System (INIS)

Hawk, J.A.; Alman, D.E.; Wilson, R.D.

1995-01-01

The US Bureau of Mines is investigating the wear behavior of a variety of advanced materials. Among the many materials under evaluation are intermetallic alloys based on the compounds: Fe 3 Al, Ti 3 Al, TiAl, Al 3 Ti, NiAl and MoSi 2 . The high hardness, high modulus, low density, and superior environmental stability of these compounds make them attractive for wear materials. This paper reports on the abrasive wear of alloys and composites based on the above compounds. The abrasive wear behavior of these alloys and composites are compared to other engineering materials used in wear applications

Abrasive water jet: a complementary tool

International Nuclear Information System (INIS)

Duarte, J.P.; Pecas, P.; Nunes, E.; Gouveia, H.

1998-01-01

The abrasive water jet is a powerful cutting tool, whose main advantages lie in the absence of thermal effects and the capability of cutting highly thick materials. Compared with Laser, the abrasive water jet allows the cutting of a larger range of thicknesses and a wider variety of materials such as: ornamental stones, metals, polymers, composites, wood, glass ceramics. The application of this technology has suffered and extensive growth, with successful applications in varied industrial sectors like the automotive, aerospace, textile, metalworking, ornamental stones, etc. The present communication aims at introducing the abrasive water jet as a complementary tool to laser cutting, presenting its advantages by showing some documented examples of pieces cut for different industries. (Author) 5 refs

Improved model for the angular dependence of excimer laser ablation rates in polymer materials

Science.gov (United States)

Pedder, J. E. A.; Holmes, A. S.; Dyer, P. E.

2009-10-01

Measurements of the angle-dependent ablation rates of polymers that have applications in microdevice fabrication are reported. A simple model based on Beer's law, including plume absorption, is shown to give good agreement with the experimental findings for polycarbonate and SU8, ablated using the 193 and 248 nm excimer lasers, respectively. The modeling forms a useful tool for designing masks needed to fabricate complex surface relief by ablation.

Numerical analysis of laser ablation using the axisymmetric two-temperature model

Science.gov (United States)

Dziatkiewicz, Jolanta; Majchrzak, Ewa

2018-01-01

Laser ablation of the axisymmetric micro-domain is analyzed. To describe the thermal processes occurring in the micro-domain the two-temperature hyperbolic model supplemented by the boundary and initial conditions is used. This model takes into account the phase changes of material (solid-liquid and liquid-vapour) and the ablation process. At the stage of numerical computations the finite difference method with staggered grid is used. In the final part the results of computations are shown.

Assessment of mechanical and three-body abrasive wear peculiarity ...

Indian Academy of Sciences (India)

The three-body abrasive wear characteristic of fabricated composites has been assessed under different operating conditions. For this, the three-body abrasion test is done on dry abrasion test rig (TR-50)and analysed using Taguchi's experimental design scheme and analysis of variance. The results obtained from these ...

Influence of the atomic mass of the background gas on laser ablation plume propagation

DEFF Research Database (Denmark)

Amoruso, Salvatore; Schou, Jørgen; Lunney, James G.

2008-01-01

A combination of time-of-flight ion probe measurements and gas dynamical modeling has been used to investigate the propagation of a laser ablation plume in gases of different atomic/molecular weight. The pressure variation of the ion time-of-flight was found to be well described by the gas...... dynamical model of Predtechensky and Mayorov (Appl. Supercond. 1:2011, 1993). In particular, the model describes how the pressure required to stop the plume in a given distance depends on the atomic/molecular weight of the gas, which is a feature that cannot be explained by standard point......-blast-wave descriptions of laser ablation plume expansion in gas....

Virtual In-Silico Modeling Guided Catheter Ablation Predicts Effective Linear Ablation Lesion Set for Longstanding Persistent Atrial Fibrillation: Multicenter Prospective Randomized Study.

Science.gov (United States)

Shim, Jaemin; Hwang, Minki; Song, Jun-Seop; Lim, Byounghyun; Kim, Tae-Hoon; Joung, Boyoung; Kim, Sung-Hwan; Oh, Yong-Seog; Nam, Gi-Byung; On, Young Keun; Oh, Seil; Kim, Young-Hoon; Pak, Hui-Nam

2017-01-01

Objective: Radiofrequency catheter ablation for persistent atrial fibrillation (PeAF) still has a substantial recurrence rate. This study aims to investigate whether an AF ablation lesion set chosen using in-silico ablation (V-ABL) is clinically feasible and more effective than an empirically chosen ablation lesion set (Em-ABL) in patients with PeAF. Methods: We prospectively included 108 patients with antiarrhythmic drug-resistant PeAF (77.8% men, age 60.8 ± 9.9 years), and randomly assigned them to the V-ABL ( n = 53) and Em-ABL ( n = 55) groups. Five different in-silico ablation lesion sets [1 pulmonary vein isolation (PVI), 3 linear ablations, and 1 electrogram-guided ablation] were compared using heart-CT integrated AF modeling. We evaluated the feasibility, safety, and efficacy of V-ABL compared with that of Em-ABL. Results: The pre-procedural computing time for five different ablation strategies was 166 ± 11 min. In the Em-ABL group, the earliest terminating blinded in-silico lesion set matched with the Em-ABL lesion set in 21.8%. V-ABL was not inferior to Em-ABL in terms of procedure time ( p = 0.403), ablation time ( p = 0.510), and major complication rate ( p = 0.900). During 12.6 ± 3.8 months of follow-up, the clinical recurrence rate was 14.0% in the V-ABL group and 18.9% in the Em-ABL group ( p = 0.538). In Em-ABL group, clinical recurrence rate was significantly lower after PVI+posterior box+anterior linear ablation, which showed the most frequent termination during in-silico ablation (log-rank p = 0.027). Conclusions: V-ABL was feasible in clinical practice, not inferior to Em-ABL, and predicts the most effective ablation lesion set in patients who underwent PeAF ablation.

21 CFR 872.6030 - Oral cavity abrasive polishing agent.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Oral cavity abrasive polishing agent. 872.6030... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6030 Oral cavity abrasive polishing agent. (a) Identification. An oral cavity abrasive polishing agent is a device in paste or powder form...

Energy balance of a laser ablation plume expanding in a background gas

DEFF Research Database (Denmark)

Amoruso, Salvatore; Schou, Jørgen; Lunney, James G.

2010-01-01

The energy balance of a laser ablation plume in an ambient gas for nanosecond pulses has been investigated on the basis of the model of Predtechensky and Mayorov (PM), which provides a relatively simple and clear description of the essential hydrodynamics. This approach also leads to an insightfu...

Developing a trend prediction model of subsurface damage for fixed-abrasive grinding of optics by cup wheels.

Science.gov (United States)

Dong, Zhichao; Cheng, Haobo

2016-11-10

Fixed-abrasive grinding by cup wheels plays an important role in the production of precision optics. During cup wheel grinding, we strive for a large removal rate while maintaining fine integrity on the surface and subsurface layers (academically recognized as surface roughness and subsurface damage, respectively). This study develops a theoretical model used to predict the trend of subsurface damage of optics (with respect to various grinding parameters) in fixed-abrasive grinding by cup wheels. It is derived from the maximum undeformed chip thickness model, and it successfully correlates the pivotal parameters of cup wheel grinding with the subsurface damage depth. The efficiency of this model is then demonstrated by a set of experiments performed on a cup wheel grinding machine. In these experiments, the characteristics of subsurface damage are inspected by a wedge-polishing plus microscopic inspection method, revealing that the subsurface damage induced in cup wheel grinding is composed of craterlike morphologies and slender cracks, with depth ranging from ∼6.2 to ∼13.2  μm under the specified grinding parameters. With the help of the proposed model, an optimized grinding strategy is suggested for realizing fine subsurface integrity as well as high removal rate, which can alleviate the workload of subsequent lapping and polishing.

Enthalpy model for heating, melting, and vaporization in laser ablation

Directory of Open Access Journals (Sweden)

Vasilios Alexiades

2010-09-01

Full Text Available Laser ablation is used in a growing number of applications in various areas including medicine, archaeology, chemistry, environmental and materials sciences. In this work the heat transfer and phase change phenomena during nanosecond laser ablation of a copper (Cu target in a helium (He background gas at atmospheric pressure are presented. An enthalpy model is outlined, which accounts for heating, melting, and vaporization of the target. As far as we know, this is the first model that connects the thermodynamics and underlying kinetics of this challenging phase change problem in a self-consistent way.

X-ray Micro-Tomography of Ablative Heat Shield Materials

Science.gov (United States)

Panerai, Francesco; Ferguson, Joseph; Borner, Arnaud; Mansour, Nagi N.; Barnard, Harold S.; MacDowell, Alastair A.; Parkinson, Dilworth Y.

2016-01-01

X-ray micro-tomography is a non-destructive characterization technique that allows imaging of materials structures with voxel sizes in the micrometer range. This level of resolution makes the technique very attractive for imaging porous ablators used in hypersonic entry systems. Besides providing a high fidelity description of the material architecture, micro-tomography enables computations of bulk material properties and simulations of micro-scale phenomena. This presentation provides an overview of a collaborative effort between NASA Ames Research Center and Lawrence Berkeley National Laboratory, aimed at developing micro-tomography experiments and simulations for porous ablative materials. Measurements are carried using x-rays from the Advanced Light Source at Berkeley Lab on different classes of ablative materials used in NASA entry systems. Challenges, strengths and limitations of the technique for imaging materials such as lightweight carbon-phenolic systems and woven textiles are discussed. Computational tools developed to perform numerical simulations based on micro-tomography are described. These enable computations of material properties such as permeability, thermal and radiative conductivity, tortuosity and other parameters that are used in ablator response models. Finally, we present the design of environmental cells that enable imaging materials under simulated operational conditions, such as high temperature, mechanical loads and oxidizing atmospheres.Keywords: Micro-tomography, Porous media, Ablation

Saphenous Venous Ablation with Hot Contrast in a Canine Model

International Nuclear Information System (INIS)

Prasad, Amit; Qian Zhong; Kirsch, David; Eissa, Marna; Narra, Pavan; Lopera, Jorge; Espinoza, Carmen G.; Castaneda, Wifrido

2008-01-01

Purpose. To determine the feasibility, efficacy, and safety of thermal ablation of the saphenous vein with hot contrast medium. Methods. Twelve saphenous veins of 6 dogs were percutaneously ablated with hot contrast medium. In all animals, ablation was performed in the vein of one leg, followed by ablation in the contralateral side 1 month later. An occlusion balloon catheter was placed in the infragenicular segment of the saphenous vein via a jugular access to prevent unwanted thermal effects on the non-target segment of the saphenous vein. After inflation of the balloon, 10 ml of hot contrast medium was injected under fluoroscopic control through a sheath placed in the saphenous vein above the ankle. A second 10 ml injection of hot contrast medium was made after 5 min in each vessel. Venographic follow-up of the ablated veins was performed at 1 month (n = 12) and 2 months (n = 6). Results. Follow-up venograms showed that all ablated venous segments were occluded at 1 month. In 6 veins which were followed up to 2 months, 4 (66%) remained occluded, 1 (16%) was partially patent, and the remaining vein (16%) was completely patent. In these latter 2 cases, an inadequate amount of hot contrast was delivered to the lumen due to a closed balloon catheter downstream which did not allow contrast to displace blood within the vessel. Discussion. Hot contrast medium thermal ablation of the saphenous vein appears feasible, safe, and effective in the canine model, provided an adequate amount of embolization agent is used

Abrasion of 6 dentifrices measured by vertical scanning interference microscopy.

Science.gov (United States)

Pascaretti-Grizon, Florence; Mabilleau, Guillaume; Chappard, Daniel

2013-01-01

The abrasion of dentifrices is well recognized to eliminate the dental plaque. The aims of this study were to characterize the abrasive powders of 6 dentifrices (3 toothpastes and 3 toothpowders) and to measure the abrasion on a test surface by Vertical Scanning Interference microscopy (VSI). Bright field and polarization microscopy were used to identify the abrasive particles on the crude dentifrices and after prolonged washes. Scanning electron microscopy and microanalysis characterized the shape and nature of the particles. Standardized and polished blocks of poly(methylmethacrylate) were brushed with a commercial electric toothbrush with the dentifrices. VSI quantified the mean roughness (Ra) and illustrated in 3D the abraded areas. Toothpastes induced a limited abrasion. Toothpowders induced a significantly higher roughness linked to the size of the abrasive particles. One powder (Gencix® produced a high abrasion when used with a standard testing weight. However, the powder is based on pumice particles covered by a plant homogenate that readily dissolves in water. When used in the same volume, or after dispersion in water, Ra was markedly reduced. Light and electron microscopy characterize the abrasive particles and VSI is a new tool allowing the analysis of large surface of abraded materials.

Basics of cutting and abrasive processes

CERN Document Server

Toenshoff, Hans Kurt

2013-01-01

Manufacturing is the basic industrial activity generating real value. Cutting and abrasive technologies are the backbone of precision production in machine, automotive and aircraft building as well as of production of consumer goods. We present the knowledge of modern manufacturing in these technologies on the basis of scientific research. The theory of cutting and abrasive processes and the knowledge about their application in industrial practice are a prerequisite for the studies of manufacturing science and an important part of the curriculum of the master study in German mechanical engineering. The basis of this book is our lecture “Basics of cutting and abrasive processes” (4 semester hours/3 credit hours) at the Leibniz University Hannover, which we offer to the diploma and master students specializing in manufacturing science.

Potassium titanyl phosphate laser tissue ablation: development and experimental validation of a new numerical model.

Science.gov (United States)

Elkhalil, Hossam; Akkin, Taner; Pearce, John; Bischof, John

2012-10-01

The photoselective vaporization of prostate (PVP) green light (532 nm) laser is increasingly being used as an alternative to the transurethral resection of prostate (TURP) for treatment of benign prostatic hyperplasia (BPH) in older patients and those who are poor surgical candidates. In order to achieve the goals of increased tissue removal volume (i.e., "ablation" in the engineering sense) and reduced collateral thermal damage during the PVP green light treatment, a two dimensional computational model for laser tissue ablation based on available parameters in the literature has been developed and compared to experiments. The model is based on the control volume finite difference and the enthalpy method with a mechanistically defined energy necessary to ablate (i.e., physically remove) a volume of tissue (i.e., energy of ablation E(ab)). The model was able to capture the general trends experimentally observed in terms of ablation and coagulation areas, their ratio (therapeutic index (TI)), and the ablation rate (AR) (mm(3)/s). The model and experiment were in good agreement at a smaller working distance (WD) (distance from the tissue in mm) and a larger scanning speed (SS) (laser scan speed in mm/s). However, the model and experiment deviated somewhat with a larger WD and a smaller SS; this is most likely due to optical shielding and heat diffusion in the laser scanning direction, which are neglected in the model. This model is a useful first step in the mechanistic prediction of PVP based BPH laser tissue ablation. Future modeling efforts should focus on optical shielding, heat diffusion in the laser scanning direction (i.e., including 3D effects), convective heat losses at the tissue boundary, and the dynamic optical, thermal, and coagulation properties of BPH tissue.

Performance Evaluation of Abrasive Grinding Wheel Formulated ...

African Journals Online (AJOL)

This paper presents a study on the formulation and manufacture of abrasive grinding wheel using locally formulated silicon carbide abrasive grains. Six local raw material substitutes were identified through pilot study and with the initial mix of the identified materials, a systematic search for an optimal formulation of silicon ...

Dentifrice fluoride and abrasivity interplay on artificial caries lesions.

Science.gov (United States)

Nassar, Hani M; Lippert, Frank; Eckert, George J; Hara, Anderson T

2014-01-01

Incipient caries lesions on smooth surfaces may be subjected to toothbrushing, potentially leading to remineralization and/or abrasive wear. The interplay of dentifrice abrasivity and fluoride on this process is largely unknown and was investigated on three artificially created lesions with different mineral content/distribution. 120 bovine enamel specimens were randomly allocated to 12 groups (n = 10), resulting from the association of (1) lesion type [methylcellulose acid gel (MeC); carboxymethylcellulose solution (CMC); hydroxyethylcellulose gel (HEC)], (2) slurry abrasive level [low (REA 4/ RDA 69); high (REA 7/RDA 208)], and (3) fluoride concentration [0/275 ppm (14.5 mM) F as NaF]. After lesion creation, specimens were brushed in an automated brushing machine with the test slurries (50 strokes 2×/day). Specimens were kept in artificial saliva in between brushings and overnight. Enamel surface loss (SL) was determined by optical profilometry after lesion creation, 1, 3 and 5 days. Two enamel sections (from baseline and post-brushing areas) were obtained and analyzed microradiographically. Data were analyzed by analysis of variance and Tukey's tests (α = 5%). Brushing with high-abrasive slurry caused more SL than brushing with low-abrasive slurry. For MeC and CMC lesions, fluoride had a protective effect on SL from day 3 on. Furthermore, for MeC and CMC, there was a significant mineral gain in the remaining lesions except when brushed with high-abrasive slurries and 0 ppm F. For HEC, a significant mineral gain took place when low-abrasive slurry was used with fluoride. The tested lesions responded differently to the toothbrushing procedures. Both slurry fluoride content and abrasivity directly impacted SL and mineral gain of enamel caries lesions.

29 CFR 1910.215 - Abrasive wheel machinery.

Science.gov (United States)

2010-07-01

... be securely fastened to the spindle and the bearing surface shall run true. When more than one wheel... 29 Labor 5 2010-07-01 2010-07-01 false Abrasive wheel machinery. 1910.215 Section 1910.215 Labor... OCCUPATIONAL SAFETY AND HEALTH STANDARDS Machinery and Machine Guarding § 1910.215 Abrasive wheel machinery. (a...

Modeling CO2 laser ablation impulse of polymers in vapor and plasma regimes

International Nuclear Information System (INIS)

Sinko, John E.; Phipps, Claude R.

2009-01-01

An improved model for CO 2 laser ablation impulse in polyoxymethylene and similar polymers is presented that describes the transition effects from the onset of vaporization to the plasma regime in a continuous fashion. Several predictions are made for ablation behavior.

Anisotropy abrasive wear behavior of bagasse fiber reinforced ...

African Journals Online (AJOL)

parallel orientation (APO) and normal orientation (NO) by using a two body abrasion wear tester. Three different types of abrasives wear behaviour have been observed in the composite in three orientations and follow the following trends: WNO ...

Characterization of tracked radiofrequency ablation in phantom

International Nuclear Information System (INIS)

Chen, Chun-Cheng R.; Miga, Michael I.; Galloway, Robert L.

2007-01-01

In radiofrequency ablation (RFA), successful therapy requires accurate, image-guided placement of the ablation device in a location selected by a predictive treatment plan. Current planning methods rely on geometric models of ablations that are not sensitive to underlying physical processes in RFA. Implementing plans based on computational models of RFA with image-guided techniques, however, has not been well characterized. To study the use of computational models of RFA in planning needle placement, this work compared ablations performed with an optically tracked RFA device with corresponding models of the ablations. The calibration of the tracked device allowed the positions of distal features of the device, particularly the tips of the needle electrodes, to be determined to within 1.4±0.6 mm of uncertainty. Ablations were then performed using the tracked device in a phantom system based on an agarose-albumin mixture. Images of the sliced phantom obtained from the ablation experiments were then compared with the predictions of a bioheat transfer model of RFA, which used the positional data of the tracked device obtained during ablation. The model was demonstrated to predict 90% of imaged pixels classified as being ablated. The discrepancies between model predictions and observations were analyzed and attributed to needle tracking inaccuracy as well as to uncertainties in model parameters. The results suggest the feasibility of using finite element modeling to plan ablations with predictable outcomes when implemented using tracked RFA

Transition metal carbide and boride abrasive particles

International Nuclear Information System (INIS)

Valdsaar, H.

1978-01-01

Abrasive particles and their preparation are discussed. The particles consist essentially of a matrix of titanium carbide and zirconium carbide, at least partially in solid solution form, and grains of crystalline titanium diboride dispersed throughout the carbide matrix. These abrasive particles are particularly useful as components of grinding wheels for abrading steel. 1 figure, 6 tables

Effect of ablatant composition on the ablation of a fuelling pellet

International Nuclear Information System (INIS)

Chang, C.T.; Thomsen, K.; Piret, S.

1988-01-01

The single species neutral-shielding model for the ablation of a hydrogenic pellet is extended by considering the ablatant as a mixture of four species: molecular and atomic hydrogen, protons and electrons. Compared with the results of the frozen flow, (i.e. the single species molecular hydrogen gas model), results of the analysis showed that the presence of dissociation and ionization effects caused a marked difference of the ablatant state. The attenuations of the incoming electron energy and energy flux, however, are very much similar irrespective of whether the ablated flow is in a frozen or an equilibrium state. The scaling law of the pellet ablation rate with respect to the plasma state of Te, ne and the pellet radius remains the same; the ablation rate is reduced by approximately 15%. To examine the possible existence of a spherical shell around the pellet where most of the incoming electron energy is absorbed, acodmparison is made between the local electron collisional mean free path and the electron Larmor radius. A critical field at the ionization radius is evaluated. An effective spherical energyabsorbing region exists when the local field strength is below the critical value. For a plasma state of low Te and ne, (where the ablatant is hardly ionized), and for one near the thermonuclear condition (where a highly dense ablatant exists near the pellet), the effective energy absorption region is nearly spherical. 20 refs. (author)

Abrasive water jet: a complementary tool

OpenAIRE

Duarte, J. P.; Peças, P.; Nunes, E.; Gouveia, H.

1998-01-01

The abrasive water jet is a powerful cutting tool, whose main advantages lie in the absence of thermal effects and the capability of cutting highly thick materials. Compared with Laser, the abrasive water jet allows the cutting of a larger range of thicknesses and a wider variety of materials such as: ornamental stones, metals, polymers, composites, wood, glass and ceramics. The application of this technology has suffered an extensive growth, with successful applications in varied industrial ...

Wear of dentine in vitro by toothpaste abrasives and detergents alone and combined.

Science.gov (United States)

Moore, C; Addy, M

2005-12-01

To measure in vitro the abrasion of dentine by toothpaste detergents and abrasives alone and combined. Detergents used were tego betain, sodium lauryl sulphate (SLS), adinol and pluronic diluted to 1% w/v. Abrasives were three artificial silicas, tixosil 73 and 123 and Zeodent 113, and calcium carbonate used at 2.5% w/v. Flat human dentine specimens were brushed with aqueous detergent solutions or abrasive slurries, detergent abrasive slurries and water for 20,000 brush strokes. Dentine loss was measured by non-contacting profilometry at 10,000 and 20,000 strokes. Silica particle size distribution was measured by laser deflection. Loss of dentine occurred with all detergents, abrasives and detergent abrasion combinations, but was not linear with number of brush strokes. Water appeared to remove the smear layer only, but all detergents exceeded the predicted smear layer thickness. The silica abrasives differed in abrasion properties despite similar particle size distribution. Different detergents modulated the abrasives actions in mainly positive or mainly negative directions. Detergents appear able to attack the dentine surface to produce wear. Abrasives vary considerably in wear produced under similar conditions. Detergents modulate the effect of abrasives in a way that may reflect the rheological properties of the mixture.

Black-box modeling to estimate tissue temperature during radiofrequency catheter cardiac ablation: feasibility study on an agar phantom model

International Nuclear Information System (INIS)

Blasco-Gimenez, Ramón; Lequerica, Juan L; Herrero, Maria; Hornero, Fernando; Berjano, Enrique J

2010-01-01

The aim of this work was to study linear deterministic models to predict tissue temperature during radiofrequency cardiac ablation (RFCA) by measuring magnitudes such as electrode temperature, power and impedance between active and dispersive electrodes. The concept involves autoregressive models with exogenous input (ARX), which is a particular case of the autoregressive moving average model with exogenous input (ARMAX). The values of the mode parameters were determined from a least-squares fit of experimental data. The data were obtained from radiofrequency ablations conducted on agar models with different contact pressure conditions between electrode and agar (0 and 20 g) and different flow rates around the electrode (1, 1.5 and 2 L min −1 ). Half of all the ablations were chosen randomly to be used for identification (i.e. determination of model parameters) and the other half were used for model validation. The results suggest that (1) a linear model can be developed to predict tissue temperature at a depth of 4.5 mm during RF cardiac ablation by using the variables applied power, impedance and electrode temperature; (2) the best model provides a reasonably accurate estimate of tissue temperature with a 60% probability of achieving average errors better than 5 °C; (3) substantial errors (larger than 15 °C) were found only in 6.6% of cases and were associated with abnormal experiments (e.g. those involving the displacement of the ablation electrode) and (4) the impact of measuring impedance on the overall estimate is negligible (around 1 °C)

Sensitivity of microwave ablation models to tissue biophysical properties: A first step toward probabilistic modeling and treatment planning.

Science.gov (United States)

Sebek, Jan; Albin, Nathan; Bortel, Radoslav; Natarajan, Bala; Prakash, Punit

2016-05-01

Computational models of microwave ablation (MWA) are widely used during the design optimization of novel devices and are under consideration for patient-specific treatment planning. The objective of this study was to assess the sensitivity of computational models of MWA to tissue biophysical properties. The Morris method was employed to assess the global sensitivity of the coupled electromagnetic-thermal model, which was implemented with the finite element method (FEM). The FEM model incorporated temperature dependencies of tissue physical properties. The variability of the model was studied using six different outputs to characterize the size and shape of the ablation zone, as well as impedance matching of the ablation antenna. Furthermore, the sensitivity results were statistically analyzed and absolute influence of each input parameter was quantified. A framework for systematically incorporating model uncertainties for treatment planning was suggested. A total of 1221 simulations, incorporating 111 randomly sampled starting points, were performed. Tissue dielectric parameters, specifically relative permittivity, effective conductivity, and the threshold temperature at which they transitioned to lower values (i.e., signifying desiccation), were identified as the most influential parameters for the shape of the ablation zone and antenna impedance matching. Of the thermal parameters considered in this study, the nominal blood perfusion rate and the temperature interval across which the tissue changes phase were identified as the most influential. The latent heat of tissue water vaporization and the volumetric heat capacity of the vaporized tissue were recognized as the least influential parameters. Based on the evaluation of absolute changes, the most important parameter (perfusion) had approximately 40.23 times greater influence on ablation area than the least important parameter (volumetric heat capacity of vaporized tissue). Another significant input parameter

Bio-active glass air-abrasion has the potential to remove resin composite restorative material selectively

International Nuclear Information System (INIS)

Milly, Hussam; Andiappan, Manoharan; Thompson, Ian; Banerjee, Avijit

2014-01-01

The aims of this study were to assess: (a) the chemistry, morphology and bioactivity of bio-active glass (BAG) air-abrasive powder, (b) the effect of three air-abrasion operating parameters: air pressure, powder flow rate (PFR) and the abrasive powder itself, on the selective removal of resin composite and (c) the required “time taken”. BAG abrasive particles were characterised using scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDX) and Fourier-transform infrared spectroscopy (FTIR). Standardised resin composite restorations created within an enamel analogue block (Macor™) in vitro, were removed using air-abrasion undersimulated clinical conditions. 90 standardised cavities were scanned before and after resin composite removal using laser profilometry and the volume of the resulting 3D images calculated. Multilevel linear model was used to identify the significant factors affecting Macor™ removal. BAG powder removed resin composite more selectively than conventional air-abrasion alumina powder using the same operating parameters (p < 0.001) and the effect of altering the unit's operating parameters was significant (p < 0.001). In conclusion, BAG powder is more efficient than alumina in the selective removal of resin composite particularly under specific operating parameters, and therefore may be recommended clinically as a method of preserving sound enamel structure when repairing and removing defective resin composite restorations.

Thermal-mechanical deformation modelling of soft tissues for thermal ablation.

Science.gov (United States)

Li, Xin; Zhong, Yongmin; Jazar, Reza; Subic, Aleksandar

2014-01-01

Modeling of thermal-induced mechanical behaviors of soft tissues is of great importance for thermal ablation. This paper presents a method by integrating the heating process with thermal-induced mechanical deformations of soft tissues for simulation and analysis of the thermal ablation process. This method combines bio-heat transfer theories, constitutive elastic material law under thermal loads as well as non-rigid motion dynamics to predict and analyze thermal-mechanical deformations of soft tissues. The 3D governing equations of thermal-mechanical soft tissue deformation are discretized by using the finite difference scheme and are subsequently solved by numerical algorithms. Experimental results show that the proposed method can effectively predict the thermal-induced mechanical behaviors of soft tissues, and can be used for the thermal ablation therapy to effectively control the delivered heat energy for cancer treatment.

Method of forming an abrasive compact of cubic boron nitride

International Nuclear Information System (INIS)

Bell, F.R.

1976-01-01

This patent concerns an abrasive compact comprising diamond or cubic boron nitride or mixtures thereof held in a matrix of a refractory substance and a substance which dissolves the abrasive particle to at least a limited extent. The compact may be made by subjecting a powdered mixture of the ingredients to conditions of temperature and pressure at which the abrasive particle is crystallographically stable and the solvent substance acts to dissolve the abrasive particle. The refractory substance and solvent substance are preferably so chosen that during compact manufacture there is interaction resulting in the formation of a hard material

LITERATURE SURVEY ON ABRASION PROBLEM IN CHENILLE YARNS

Directory of Open Access Journals (Sweden)

Erhan Kenan ÇEVEN

2006-01-01

Full Text Available Chenille yarns are traditionally used in the manufacture of furnishing fabrics, fashion knitwear, and as decorative threads in many types of broad and narrow fabrics. Chenille yarn has a very distinct weakness-it does not have very good inherent abrasion resistance. When the yarns are in use, clearly the abrasion resistance of the chenille yarn is crucially important. Either during further processing or during the eventual end-use, any removal of the effect yarn forming the beard will expose the ground yarns, which in turn will result in a bare appearance. To avoid this undesirable result, several options are available. Therefore, the studies on this area are about the investigation of the influences of some material types and machine parameters on the abrasion resistance of chenille yarns and fabrics produced with these yarns. In this paper, the experimental studies about the abrasion properties of chenille yarns in yarn, knitted and woven fabric forms are summarized.

Control technology for crystalline silica exposures in construction: wet abrasive blasting.

Science.gov (United States)

Golla, Vijay; Heitbrink, William

2004-03-01

This study was designed to document the effect that wet abrasive blasting has on reducing worker exposure to crystalline silica, which has been associated with silicosis and premature death. In this study, worker exposure to respirable crystalline silica was monitored during wet abrasive blasting on the exterior walls of a parking garage to remove surface concrete and expose the underlying aggregate. In this process a wet sand mix comprised of 80% dry sand and 20% water was used. Sampling and analysis revealed that the geometric mean respirable quartz concentration was 0.2 mg/m(3) for workers conducting abrasive blasting and 0.06 mg/m(3) for helpers. When abrasive blasting was conducted in areas that apparently had reduced natural ventilation, dust exposures appeared to increase. When compared with other published data, this case study suggests that wet abrasive blasting causes less exposure to crystalline silica than dry abrasive blasting.

Nanosecond laser ablation of target Al in a gaseous medium: explosive boiling

Science.gov (United States)

Mazhukin, V. I.; Mazhukin, A. V.; Demin, M. M.; Shapranov, A. V.

2018-03-01

An approximate mathematical description of the processes of homogeneous nucleation and homogeneous evaporation (explosive boiling) of a metal target (Al) under the influence of ns laser radiation is proposed in the framework of the hydrodynamic model. Within the continuum approach, a multi-phase, multi-front hydrodynamic model and a computational algorithm are designed to simulate nanosecond laser ablation of the metal targets immersed in gaseous media. The proposed approach is intended for modeling and detailed analysis of the mechanisms of heterogeneous and homogeneous evaporation and their interaction with each other. It is shown that the proposed model and computational algorithm allow modeling of interrelated mechanisms of heterogeneous and homogeneous evaporation of metals, manifested in the form of pulsating explosive boiling. Modeling has shown that explosive evaporation in metals is due to the presence of a near-surface temperature maximum. It has been established that in nanosecond pulsed laser ablation, such exposure regimes can be implemented in which phase explosion is the main mechanism of material removal.

Electrical resistivity measurements to predict abrasion resistance of ...

Indian Academy of Sciences (India)

WINTEC

increasing expansion of highway and other construction works and decreasing natural aggregate resources in the world, the demand for crushed stone aggregates has in- creased from day-to-day. One of the important properties of rock aggregates is abrasion resistance. The abrasion resistance of aggregates is generally ...

Ablation of Solid Hydrogen in a Plasma

DEFF Research Database (Denmark)

Jørgensen, L. W.; Sillesen, Alfred Hegaard

1979-01-01

Several hydrogen pellet ablation models based on the formation of a shielding neutral cloud have been reported by different authors. The predicted ablation rates are shown to follow almost the same scaling law and this is used to explain the authors' ablation experiment.......Several hydrogen pellet ablation models based on the formation of a shielding neutral cloud have been reported by different authors. The predicted ablation rates are shown to follow almost the same scaling law and this is used to explain the authors' ablation experiment....

Submerged cutting characteristics of abrasive suspension jet

International Nuclear Information System (INIS)

Shimizu, Seiji; Peng, Guoyi; Oguma, Yasuyuki; Nishikata, Hiroki

2015-01-01

An abrasive suspension jet (ASJ) formed by propelling abrasive suspension through a nozzle has a greater cutting capability than the conventional abrasive water jet. However the cutting capability of submerged ASJs decreases drastically with increasing the standoff distance and the pressure around the jet. A sheathed nozzle nozzle with ventilation for ASJs has been developed as a mean of extending the effective stand-off distance and improving the cutting capabilities under submerged condition. In the present investigation, cutting tests by ASJs in air and under submerged condition are conducted with specimens of aluminum alloy. Air coated ASJs are formed by using a sheathed nozzle with ventilation. The relative cutting depth is defined as the cutting depth is arranged effectually by the cavitation number based on the cavity pressure measured at the sheath. (author)

Abrasive wear of ceramic wear protection at ambient and high temperatures

Science.gov (United States)

Varga, M.; Adam, K.; Tumma, M.; Alessio, K. O.

2017-05-01

Ceramic wear protection is often applied in abrasive conditions due to their excellent wear resistance. This is especially necessary in heavy industries conveying large amounts of raw materials, e.g. in steel industry. Some plants also require material transport at high temperatures and velocities, making the need of temperature stable and abrasion resistant wear protection necessary. Various types and wear behaviour of ceramic protection are known. Hence, the goal of this study is to identify the best suitable ceramic materials for abrasive conditions in harsh environments at temperatures up to 950°C and severe thermal gradients. Chamottes, known for their excellent thermal shock resistance are compared to high abrasion resistant ceramic wear tiles and a cost efficient cement-bounded hard compound. Testing was done under high-stress three-body abrasion regime with a modified ASTM G65 apparatus enabling for investigations up to ~950°C. Thereto heated abrasive is introduced into the wear track and also preheated ceramic samples were used and compared to ambient temperature experiments. Results indicate a significant temperature influence on chamottes and the hard compound. While the chamottes benefit from temperature increase, the cement-bounded hard compound showed its limitation at abrasive temperatures of 950°C. The high abrasion resistant wear tiles represented the materials with the best wear resistance and less temperature influence in the investigated range.

Fringe-shifting single-projector moiré topography application for cotyle implantate abrasion measurement

Science.gov (United States)

Rössler, Tomáš; Hrabovský, Miroslav; Pluháček, František

2005-08-01

The cotyle implantate is abraded in the body of patient and its shape changes. Information about the magnitude of abrasion is contained in the result contour map of the implantate. The locations and dimensions of abraded areas can be computed from the contours deformation. The method called the single-projector moire topography was used for the contour lines determination. The theoretical description of method is given at first. The design of the experimental set-up follows. The light grating projector was developed to realize the periodic structure on the measured surface. The method of fringe-shifting was carried out to increase the data quantity. The description of digital processing applied to the moire grating images is introduced at the end together with the examples of processed images.

Influence of martensitic phase in abrasion behaviour of stainless steel 304 L

International Nuclear Information System (INIS)

Ruzzante, J.; Alvarez, P.; Hey, A.; Gestido, G.D.; Vosen, J.H.; Fernandez, H.A.

1986-01-01

Abrasion behaviour is studied in commercial stainless steels of different class compositions by standard. The work achieved guieds in structural analysis of superficial coat formed and its relation with abrasion variables, load and velocity. The abrasion is made in an equipment LF WK of high velocity with friction powers, abrasion velocity and temperature variation registered on the tested piece. The abrasion zone is studied with scanning electron microscope (SEM). The deformed superficial zone nature is studied relationing its microstructure with profile corresponding of microhardness. (C.M.C.T.R.) [pt

Ablation mass features in multi-pulses femtosecond laser ablate molybdenum target

Science.gov (United States)

Zhao, Dongye; Gierse, Niels; Wegner, Julian; Pretzler, Georg; Oelmann, Jannis; Brezinsek, Sebastijan; Liang, Yunfeng; Neubauer, Olaf; Rasinski, Marcin; Linsmeier, Christian; Ding, Hongbin

2018-03-01

In this study, the ablation mass features related to reflectivity of bulk Molybdenum (Mo) were investigated by a Ti: Sa 6 fs laser pulse at central wavelength 790 nm. The ablated mass removal was determined using Confocal Microscopy (CM) technique. The surface reflectivity was calibrated and measured by a Lambda 950 spectrophotometer as well as a CCD camera during laser ablation. The ablation mass loss per pulse increase with the increasing of laser shots, meanwhile the surface reflectivity decrease. The multi-pulses (100 shots) ablation threshold of Mo was determined to be 0.15 J/cm2. The incubation coefficient was estimated as 0.835. The reflectivity change of the Mo target surface following multi-pulses laser ablation were studied as a function of laser ablation shots at various laser fluences from 1.07 J/cm2 to 36.23 J/cm2. The results of measured reflectivity indicate that surface reflectivity of Mo target has a significant decline in the first 3-laser pulses at the various fluences. These results are important for developing a quantitative analysis model for laser induced ablation and laser induced breakdown spectroscopy for the first wall diagnosis of EAST tokamak.

Creation of a Tumor-Mimic Model Using a Muscle Paste for Radiofrequency Ablation of the Lung

International Nuclear Information System (INIS)

Kawai, T.; Kaminou, T.; Sugiura, K.; Hashimoto, M.; Ohuchi, Y.; Adachi, A.; Fujioka, S.; Ito, H.; Nakamura, K.; Ogawa, T.

2009-01-01

The purpose of this study was to develop an easily created tumor-mimic model and evaluate its efficacy for radiofrequency ablation (RFA) of the lung. The bilateral lungs of eight living adult swine were used. A tumor-mimic model was made by percutaneous injection of 1.0 ml muscle paste through the bone biopsy needle into the lung. An RFA probe was then inserted into the tumor mimics immediately after tumor creation. Ablation time, tissue impedance, and temperature were recorded. The tumor mimics and their coagulated regions were evaluated microscopically and macroscopically. The muscle paste was easily injected into the lung parenchyma through the bone biopsy needle and well visualized under fluoroscopy. In 10 of 12 sites the tumor mimics were oval shaped, localized, and homogeneous on gross specimens. Ten tumor mimics were successfully ablated, and four locations were ablated in the normal lung parenchyma as controls. In the tumor and normal lung parenchyma, ablation times were 8.9 ± 3.5 and 4.4 ± 1.6 min, respectively; tissue impedances at the start of ablation were 100.6 ± 16.6 and 145.8 ± 26.8 Ω, respectively; and temperatures at the end of ablation were 66.0 ± 7.9 and 57.5 ± 7.6 o C, respectively. The mean size of tumor mimics was 13.9 x 8.2 mm, and their coagulated area was 18.8 x 13.1 mm. In the lung parenchyma, the coagulated area was 15.3 x 12.0 mm. In conclusion, our tumor-mimic model using muscle paste can be easily and safely created and can be ablated using the ablation algorithm in the clinical setting.

High-Fidelity Modeling of Ablation and Coupled CFD-Material Response

Data.gov (United States)

National Aeronautics and Space Administration — This research proposal seeks to improve the state of the art in the modeling and simulation of ablating thermal protection systems (TPS). It will accomplish the...

Mechanical and abrasive wear characterization of bidirectional and chopped E-glass fiber reinforced composite materials

International Nuclear Information System (INIS)

Siddhartha,; Gupta, Kuldeep

2012-01-01

Highlights: ► Bi-directional and chopped E-glass fiber reinforced epoxy composites are fabricated. ► Three body abrasive wear behavior of fabricated composites has been assessed. ► Results are validated against existing microscopic models of Lancaster and Wang. ► Tensile strength of bi-directional E-glass fiber reinforced composites increases. ► Chopped glass fiber composites are found better in abrasive wear situations. -- Abstract: Bi-directional and chopped E-glass fiber reinforced epoxy composites are fabricated in five different (15, 20, 25, 30 and 35) wt% in an epoxy resin matrix. The mechanical characterization of these composites is performed. The three body abrasive wear behavior of fabricated composites has been assessed under different operating conditions. Abrasive wear characteristics of these composites are successfully analysed using Taguchi’s experimental design scheme and analysis of variance (ANOVA). The results obtained from these experiments are also validated against existing microscopic models of Ratner-Lancaster and Wang. It is observed that quite good linear relationships is held between specific wear rate and reciprocal of ultimate strength and strain at tensile fracture of these composites which is an indicative that the experimental results are in fair agreement with these existing models. Out of all composites fabricated it is found that tensile strength of bi-directional E-glass fiber reinforced composites increases because of interface strength enhancement. Chopped glass fiber reinforced composites are observed to perform better than bi-directional glass fiber reinforced composites under abrasive wear situations. The morphology of worn composite specimens has been examined by scanning electron microscopy (SEM) to understand about dominant wear mechanisms.

Bio-active glass air-abrasion has the potential to remove resin composite restorative material selectively

Energy Technology Data Exchange (ETDEWEB)

Milly, Hussam [Biomaterials, Biomimetics and Biophotonics Research Group, Kings College London Dental Institute at Guy' s Hospital, King' s Health Partners, London (United Kingdom); Andiappan, Manoharan [Unit of Dental Public Health, Kings College London Dental Institute at Guy' s Hospital, King' s Health Partners, London (United Kingdom); Thompson, Ian [Biomaterials, Biomimetics and Biophotonics Research Group, Kings College London Dental Institute at Guy' s Hospital, King' s Health Partners, London (United Kingdom); Banerjee, Avijit, E-mail: avijit.banerjee@kcl.ac.uk [Biomaterials, Biomimetics and Biophotonics Research Group, Kings College London Dental Institute at Guy' s Hospital, King' s Health Partners, London (United Kingdom); Unit of Conservative Dentistry, King' s College London Dental Institute at Guy' s Hospital, King' s Health Partners, London (United Kingdom)

2014-06-01

The aims of this study were to assess: (a) the chemistry, morphology and bioactivity of bio-active glass (BAG) air-abrasive powder, (b) the effect of three air-abrasion operating parameters: air pressure, powder flow rate (PFR) and the abrasive powder itself, on the selective removal of resin composite and (c) the required “time taken”. BAG abrasive particles were characterised using scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDX) and Fourier-transform infrared spectroscopy (FTIR). Standardised resin composite restorations created within an enamel analogue block (Macor™) in vitro, were removed using air-abrasion undersimulated clinical conditions. 90 standardised cavities were scanned before and after resin composite removal using laser profilometry and the volume of the resulting 3D images calculated. Multilevel linear model was used to identify the significant factors affecting Macor™ removal. BAG powder removed resin composite more selectively than conventional air-abrasion alumina powder using the same operating parameters (p < 0.001) and the effect of altering the unit's operating parameters was significant (p < 0.001). In conclusion, BAG powder is more efficient than alumina in the selective removal of resin composite particularly under specific operating parameters, and therefore may be recommended clinically as a method of preserving sound enamel structure when repairing and removing defective resin composite restorations.

Solidification structure and abrasion resistance of high chromium white irons

Science.gov (United States)

Doğan, Ö. N.; Hawk, J. A.; Laird, G.

1997-06-01

Superior abrasive wear resistance, combined with relatively low production costs, makes high Cr white cast irons (WCIs) particularly attractive for applications in the grinding, milling, and pumping apparatus used to process hard materials. Hypoeutectic, eutectic, and hypereutectic cast iron compositions, containing either 15 or 26 wt pct chromium, were studied with respect to the macrostructural transitions of the castings, solidification paths, and resulting microstructures when poured with varying superheats. Completely equiaxed macrostructures were produced in thick section castings with slightly hypereutectic compositions. High-stress abrasive wear tests were then performed on the various alloys to examine the influence of both macrostructure and microstructure on wear resistance. Results indicated that the alloys with a primarily austenitic matrix had a higher abrasion resistance than similar alloys with a pearlitic/bainitic matrix. Improvement in abrasion resistance was partially attributed to the ability of the austenite to transform to martensite at the wear surface during the abrasion process.

Neuro - Fuzzy Analysis for Silicon Carbide Abrasive Grains ...

African Journals Online (AJOL)

Grinding wheels are made of very small, sharp and hard abrasive materials or grits held together by strong porous bond. Abrasive materials are materials of extreme hardness that are used to shape other materials by a grinding or abrading action and they are used either as loose grains, as grinding wheels, or as coatings ...

Third abrasive wear mode: is it possible?

Directory of Open Access Journals (Sweden)

Ronaldo Câmara Cozza

2014-04-01

Full Text Available The objective of this paper is to propose an initial discussion on the characterization of a third abrasive wear mode. The results obtained in a previous work [1] under different test conditions revealed the occurrence of the superposition of the “rolling” and “grooving” abrasive wear modes. This phenomenon was denoted “micro-rolling abrasion” due to the observation that “rolling abrasion” was found to act on “grooving abrasion”.

Abrasive water jet cutting

International Nuclear Information System (INIS)

Leist, K.J.; Funnell, G.J.

1988-01-01

In the process of selecting a failed equipment cut-up tool for the process facility modifications (PFM) project, a system using an abrasive water jet (AWJ) was developed and tested for remote disassembly of failed equipment. It is presented in this paper

Atmospheric particulate emissions from dry abrasive blasting using coal slag

Energy Technology Data Exchange (ETDEWEB)

Bhaskar Kura; Kalpalatha Kambham; Sivaramakrishnan Sangameswaran; Sandhya Potana [University of New Orleans, New Orleans, LA (United States). Department of Civil and Environmental Engineering

2006-08-15

Coal slag is one of the widely used abrasives in dry abrasive blasting. Atmospheric emissions from this process include particulate matter (PM) and heavy metals, such as chromium, lead, manganese, nickel. Quantities and characteristics of PM emissions depend on abrasive characteristics and process parameters. Emission factors are key inputs to estimate emissions. Experiments were conducted to study the effect of blast pressure, abrasive feed rate, and initial surface contamination on total PM (TPM) emission factors for coal slag. Rusted and painted mild steel surfaces were used as base plates. Blasting was carried out in an enclosed chamber, and PM was collected from an exhaust duct using U.S. Environment Protection Agency source sampling methods for stationary sources. Results showed that there is significant effect of blast pressure, feed rate, and surface contamination on TPM emissions. Mathematical equations were developed to estimate emission factors in terms of mass of emissions per unit mass of abrasive used, as well as mass of emissions per unit of surface area cleaned. These equations will help industries in estimating PM emissions based on blast pressure and abrasive feed rate. In addition, emissions can be reduced by choosing optimum operating conditions. 40 refs., 5 figs., 2 tabs.

An improved three-dimensional two-temperature model for multi-pulse femtosecond laser ablation of aluminum

International Nuclear Information System (INIS)

Zhang, Jinping; Chen, Yuping; Hu, Mengning; Chen, Xianfeng

2015-01-01

In this paper, an improved three-dimensional two-temperature model for multi-pulse femtosecond laser ablation of aluminum was proposed and proved in our experiment. Aiming to achieve hole-drilling with a high ratio of depth/entrance diameter in vacuum, this model can predict the depth and radius of the drilled holes precisely when employing different laser parameters. Additionally, for multi-pulse laser ablation, we found that the laser fluence and number of pulses are the dominant parameters and the multi-pulse ablation threshold is much lower than the single-pulse one, which will help to obtain high-quality holes

An improved three-dimensional two-temperature model for multi-pulse femtosecond laser ablation of aluminum

Energy Technology Data Exchange (ETDEWEB)

Zhang, Jinping; Chen, Yuping, E-mail: ypchen@sjtu.edu.cn; Hu, Mengning; Chen, Xianfeng [State Key Laboratory of Advanced Optical Communication Systems and Networks, Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China)

2015-02-14

In this paper, an improved three-dimensional two-temperature model for multi-pulse femtosecond laser ablation of aluminum was proposed and proved in our experiment. Aiming to achieve hole-drilling with a high ratio of depth/entrance diameter in vacuum, this model can predict the depth and radius of the drilled holes precisely when employing different laser parameters. Additionally, for multi-pulse laser ablation, we found that the laser fluence and number of pulses are the dominant parameters and the multi-pulse ablation threshold is much lower than the single-pulse one, which will help to obtain high-quality holes.

Prediction Of Abrasive And Diffusive Tool Wear Mechanisms In Machining

Science.gov (United States)

Rizzuti, S.; Umbrello, D.

2011-01-01

Tool wear prediction is regarded as very important task in order to maximize tool performance, minimize cutting costs and improve the quality of workpiece in cutting. In this research work, an experimental campaign was carried out at the varying of cutting conditions with the aim to measure both crater and flank tool wear, during machining of an AISI 1045 with an uncoated carbide tool P40. Parallel a FEM-based analysis was developed in order to study the tool wear mechanisms, taking also into account the influence of the cutting conditions and the temperature reached on the tool surfaces. The results show that, when the temperature of the tool rake surface is lower than the activation temperature of the diffusive phenomenon, the wear rate can be estimated applying an abrasive model. In contrast, in the tool area where the temperature is higher than the diffusive activation temperature, the wear rate can be evaluated applying a diffusive model. Finally, for a temperature ranges within the above cited values an adopted abrasive-diffusive wear model furnished the possibility to correctly evaluate the tool wear phenomena.

Modeling snow accumulation and ablation processes in forested environments

Science.gov (United States)

Andreadis, Konstantinos M.; Storck, Pascal; Lettenmaier, Dennis P.

2009-05-01

The effects of forest canopies on snow accumulation and ablation processes can be very important for the hydrology of midlatitude and high-latitude areas. A mass and energy balance model for snow accumulation and ablation processes in forested environments was developed utilizing extensive measurements of snow interception and release in a maritime mountainous site in Oregon. The model was evaluated using 2 years of weighing lysimeter data and was able to reproduce the snow water equivalent (SWE) evolution throughout winters both beneath the canopy and in the nearby clearing, with correlations to observations ranging from 0.81 to 0.99. Additionally, the model was evaluated using measurements from a Boreal Ecosystem-Atmosphere Study (BOREAS) field site in Canada to test the robustness of the canopy snow interception algorithm in a much different climate. Simulated SWE was relatively close to the observations for the forested sites, with discrepancies evident in some cases. Although the model formulation appeared robust for both types of climates, sensitivity to parameters such as snow roughness length and maximum interception capacity suggested the magnitude of improvements of SWE simulations that might be achieved by calibration.

Self-organized pattern formation upon femtosecond laser ablation by circularly polarized light

International Nuclear Information System (INIS)

Varlamova, Olga; Costache, Florenta; Reif, Juergen; Bestehorn, Michael

2006-01-01

Surface ripples generation upon femtosecond laser ablation is attributed to self-organized structure formation from instability. We report that linear arrangements are observed not only for linearly polarized light but also for ablation with circularly polarized light. Long ordered chains of spherical nanoparticles, reminding of bead-strings are almost parallel but exhibit typical non-linear dynamics features such as bifurcations. In a first attempt to understand the self-assembly, we rely on models recently developed for the description of similar structures upon ion beam erosion and for the simulation of instabilities in thin liquid films. Our picture describes an unstable surface layer, non-uniformly eroded through Coulomb repulsion between individual positive charges

X-ray ablation measurements and modeling for ICF applications

International Nuclear Information System (INIS)

Anderson, A.T.

1996-09-01

X-ray ablation of material from the first wall and other components of an ICF (Inertial Confinement Fusion) chamber is a major threat to the laser final optics. Material condensing on these optics after a shot may cause damage with subsequent laser shots. To ensure the successful operation of the ICF facility, removal rates must be predicted accurately. The goal for this dissertation is to develop an experimentally validated x-ray response model, with particular application to the National Ignition Facility (NIF). Accurate knowledge of the x-ray and debris emissions from ICF targets is a critical first step in the process of predicting the performance of the target chamber system. A number of 1-D numerical simulations of NIF targets have been run to characterize target output in terms of energy, angular distribution, spectrum, and pulse shape. Scaling of output characteristics with variations of both target yield and hohlraum wall thickness are also described. Experiments have been conducted at the Nova laser on the effects of relevant x-ray fluences on various materials. The response was diagnosed using post-shot examinations of the surfaces with scanning electron microscope and atomic force microscope instruments. Judgments were made about the dominant removal mechanisms for each material. Measurements of removal depths were made to provide data for the modeling. The finite difference ablation code developed here (ABLATOR) combines the thermomechanical response of materials to x-rays with models of various removal mechanisms. The former aspect refers to energy deposition in such small characteristic depths (∼ micron) that thermal conduction and hydrodynamic motion are significant effects on the nanosecond time scale. The material removal models use the resulting time histories of temperature and pressure-profiles, along with ancillary local conditions, to predict rates of surface vaporization and the onset of conditions that would lead to spallation

Experimental investigations on vessel-hole ablation during severe accidents

International Nuclear Information System (INIS)

Sehgal, B.R.; Dinh, T.N.; Green, J.A.; Paladino, D.

1997-12-01

This report presents experimental results, and subsequent analyses, of scaled reactor pressure vessel (RPV) failure site ablation tests conducted at the Royal Institute of Technology, Division of Nuclear Power Safety (RIT/NPS). The goal of the test program is to reduce the uncertainty level associated with the phase-change-ablation process, and, thus, improve the characterization of the melt discharge loading on the containment. In a series of moderate temperature experiments, the corium melt is simulated by the binary oxide CaO-B 2 O 3 or the binary eutectic and non-eutectic salts NaNO 3 -KNO 3 , while the RPV head steel is represented by a Pb, Sn or metal alloys plate. A complementary set of experiments was conducted at lower temperatures, using water as melt and salted ice as plate material. These experiments scale well to the postulated prototypical conditions. The multidimensional code HAMISA, developed at RIT/NPS, is employed to analyze the experiments with good pre- and post-test predictions. The effects of melt viscosity and crust surface roughness, along with failure site entrance and exit frictional losses on the ablation characteristics are investigated. Theoretical concept was proposed to describe physical mechanisms which govern the vessel-hole ablation process during core melt discharge from RPV. Experimental data obtained from hole ablation tests and separate-effect tests performed at RIT/NPS were used to validate component physical models of the HAMISA code. It is believed that the hole ablation phenomenology is quite well understood. Detailed description of experiments and experimental data, as well as results of analyses are provided in the appendixes

Submerged cutting characteristics of abrasive suspension jet

International Nuclear Information System (INIS)

Shimizu, Seiji; Peng, Guoyi; Oguma, Yasuyuki; Nishikata, Hiroyuki

2015-01-01

An abrasive suspension jet (ASJ) formed by propelling abrasive suspension through a nozzle has a greater cutting capability than the conventional abrasive water jet. However the cutting capability of submerged ASJs decreases drastically with increasing the standoff distance and the pressure around the jet. A sheathed nozzle with ventilation for ASJs has been developed as a mean of extending the effective stand-off distance and improving the cutting capabilities under submerged condition. In the present investigation, cutting tests by ASJs in air and under submerged condition are conducted with specimens of aluminum alloy. Air coated ASJs are formed by using a sheathed nozzle with ventilation. The relative cutting depth is defined as the cutting depth under submerged condition divided by the cutting depth in air at the same standoff distance. The relative cutting depth is arranged effectually by the cavitation number based on the cavity pressure measured at the sheath. (author)

Laser ablation for analytical sampling: what can we learn from modeling?

International Nuclear Information System (INIS)

Bogaerts, Annemie; Chen Zhaoyang; Gijbels, Renaat; Vertes, Akos

2003-01-01

The paper is built up in two parts. First, a rather comprehensive introduction is given, with a brief overview of the different application fields of laser ablation, focusing mainly on the analytical applications, and an overview of the different modeling approaches available for laser ablation. Further, a discussion is presented here about the laser evaporated plume expansion in vacuum or in a background gas, as well as about the different mechanisms for particle formation in the laser ablation process, which is most relevant for laser ablation as solid sampling technique for inductively coupled plasma (ICP) spectrometry. In the second part, a model is presented that describes the interaction of an ns-pulsed laser with a Cu target, as well as the resulting plume expansion and plasma formation. The results presented here, include the temperature distribution in the target, the melting and evaporation of the target, the vapor density, velocity and temperature distribution in the evaporated plume, the ionization degree and the density profiles of Cu 0 atoms, Cu + and Cu 2+ ions and electrons in the plume (plasma), as well as the resulting plasma shielding of the incoming laser beam. Results are presented as a function of time during and after the laser pulse, and as a function of position in the target or in the plume. The influence of the target reflection coefficient on the above calculation results is investigated. Finally, the effect of the laser pulse fluence on the target heating, melting and vaporization, and on the plume characteristics and plasma formation is studied. Our modeling results are in reasonable agreement with calculated and measured data from literature

Atrial fibrillation ablation using a closed irrigation radiofrequency ablation catheter.

Science.gov (United States)

Golden, Keith; Mounsey, John Paul; Chung, Eugene; Roomiani, Pahresah; Morse, Michael Andew; Patel, Ankit; Gehi, Anil

2012-05-01

Catheter ablation is an effective therapy for symptomatic, medically refractory atrial fibrillation (AF). Open-irrigated radiofrequency (RF) ablation catheters produce transmural lesions at the cost of increased fluid delivery. In vivo models suggest closed-irrigated RF catheters create equivalent lesions, but clinical outcomes are limited. A cohort of 195 sequential patients with symptomatic AF underwent stepwise AF ablation (AFA) using a closed-irrigation ablation catheter. Recurrence of AF was monitored and outcomes were evaluated using Kaplan-Meier survival analysis and Cox proportional hazards models. Mean age was 59.0 years, 74.9% were male, 56.4% of patients were paroxysmal and mean duration of AF was 5.4 years. Patients had multiple comorbidities including hypertension (76.4%), tobacco abuse (42.1%), diabetes (17.4%), and obesity (mean body mass index 30.8). The median follow-up was 55.8 weeks. Overall event-free survival was 73.6% with one ablation and 77.4% after reablation (reablation rate was 8.7%). Median time to recurrence was 26.9 weeks. AF was more likely to recur in patients being treated with antiarrhythmic therapy at the time of last follow-up (recurrence rate 30.3% with antiarrhythmic drugs, 13.2% without antiarrhythmic drugs; hazard ratio [HR] 2.2, 95% confidence interval [CI] 1.1-4.4, P = 0.024) and in those with a history of AF greater than 2 years duration (HR 2.7, 95% CI 1.1-6.9, P = 0.038). Our study represents the largest cohort of patients receiving AFA with closed-irrigation ablation catheters. We demonstrate comparable outcomes to those previously reported in studies of open-irrigation ablation catheters. Given the theoretical benefits of a closed-irrigation system, a large head-to-head comparison using this catheter is warranted. ©2012, The Authors. Journal compilation ©2012 Wiley Periodicals, Inc.

Analysis of coarse aggregate performance based on the modified Micro Deval abrasion test

Directory of Open Access Journals (Sweden)

Jiangfeng Wu

2018-03-01

Full Text Available The anti-abrasion property of aggregate significantly affects the performance of the pavement. In this research, the quartzite and gneiss which were produced in Lincheng County, Xingtai City, Hebei Province were selected as test samples. According to the American Society for Testing and Materials standard, the Micro-Deval abrasion test was taken every 1000 rotation times until 20,000 times, and the change trend of the Micro-Deval abrasion value was obtained. Results showed that the abrasion values were in the exponential growth rate rather than linear rate. Their R-Square coefficient was 0.99142 and 0.99916 respectively. The gravel information such as area, roundness, diameter, perimeter and so on were calculated and analyzed by Image-Pro Plus software, which provided a rapid way for the 2D morphology characteristics analysis of the coarse aggregate. Keywords: Micro-Deval abrasion test, Coarse aggregate, Anti-abrasion property, Abrasion values

Comprehensive preclinical evaluation of a multi-physics model of liver tumor radiofrequency ablation.

Science.gov (United States)

Audigier, Chloé; Mansi, Tommaso; Delingette, Hervé; Rapaka, Saikiran; Passerini, Tiziano; Mihalef, Viorel; Jolly, Marie-Pierre; Pop, Raoul; Diana, Michele; Soler, Luc; Kamen, Ali; Comaniciu, Dorin; Ayache, Nicholas

2017-09-01

We aim at developing a framework for the validation of a subject-specific multi-physics model of liver tumor radiofrequency ablation (RFA). The RFA computation becomes subject specific after several levels of personalization: geometrical and biophysical (hemodynamics, heat transfer and an extended cellular necrosis model). We present a comprehensive experimental setup combining multimodal, pre- and postoperative anatomical and functional images, as well as the interventional monitoring of intra-operative signals: the temperature and delivered power. To exploit this dataset, an efficient processing pipeline is introduced, which copes with image noise, variable resolution and anisotropy. The validation study includes twelve ablations from five healthy pig livers: a mean point-to-mesh error between predicted and actual ablation extent of 5.3 ± 3.6 mm is achieved. This enables an end-to-end preclinical validation framework that considers the available dataset.

Abrasive wear of WC-NiMoCrFeCo thermally sprayed coatings in dependence on different types of abrasive sands

Czech Academy of Sciences Publication Activity Database

Kašparová, M.; Zahálka, F.; Houdková, Š.; Ctibor, Pavel

2010-01-01

Roč. 48, č. 1 (2010), s. 75-85 ISSN 0023-432X R&D Projects: GA AV ČR 1QS200430560 Institutional research plan: CEZ:AV0Z20430508 Keywords : WC-Hastelloy * abrasive wear * Al2O3 sand * SiO2 sand * braun size * abrasive efficiency Subject RIV: JG - Metallurgy Impact factor: 0.471, year: 2010 http://kovmat.sav.sk/abstract.php?rr=48&cc=1&ss=73

Mangrove Cultivation For Dealing With Coastal Abrasion Case Study Of Karangsong

Science.gov (United States)

Fatimatuzzahroh, Feti; Hadi, Sudharto P.; Purnaweni, Hartuti

2018-02-01

Coastal abrasion is consequence from destructive waves and sea current. One of cause is human intervention. The effort to solve of abrasion is by mangrove cultivation. Mangroves are halophyte plant that can restrain the sea wave. Mangrove cultivation required participation community that give awareness the importance of mangrove in coastal sustainability. Mangroves in coastal Karangsong, Indramayu west java, in 2007 was through abrasion approximately 127.30 ha. Mangrove cultivation in Karangsong has been replanting since 1998 to 2003, but there was no maintenance and management. In 2007 until 2015 Karangsong replanting mangroves and has been succeed. Karangsong became the center of mangrove study for west java area in 2015. This achievement is result of cooperation between community, NGO, and local government. In addition, this effort made not only overcome the abrasion problem but also give community awareness about the importance of mangrove cultivation in preventing coastal abrasion throughout community development. This paper reviews abrasion in Karangsong and the impact for local community and empowerment in mangrove cultivation. To achieve the success mangrove cultivation required community development approach from planning process, planting, maintenance and management.

Boundary conditions for 3D dynamic models of ablation of ceramics by pulsed mid-infrared lasers

Energy Technology Data Exchange (ETDEWEB)

Vila Verde, A. [Department of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Ramos, Marta M.D. [Department of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal)]. E-mail: marta@fisica.uminho.pt

2005-07-15

We present and discuss a set of boundary conditions (BCs) to use in three-dimensional, mesoscopic, finite element models of mid-infrared pulsed laser ablation of brittle materials. These models allow the study of the transient displacement and stress fields generated at micrometer scales during and after one laser pulse, where using conventional BCs may lead to some results without physical significance that can be considered an artefact of the calculations. The proposed BCs are tested and applied to a micrometer-scale continuous model of human dental enamel under CO{sub 2} radiation (10.6 {mu}m, 0.35 {mu}s pulse, sub-ablative fluence), giving rise to the following results: the highest stress is obtained at the irradiated surface of the model, at the end of the laser pulse, but afterwards it decreases rapidly until it becomes significantly lower than the stress in a region 2.5 {mu}m deep in the model; a thermally induced vibration in the material is predicted. This non-intuitive dynamics in stress and displacement distribution cannot be neglected and has to be considered in dynamic laser ablation models, since it may have serious implications in the mechanisms of ablation.

Experimental Research into Technology of Abrasive Flow Machining Nonlinear Tube Runner

Directory of Open Access Journals (Sweden)

Junye Li

2014-06-01

Full Text Available In the fields of military and civil uses, some special passages exist in many major parts, such as non-linear tubes. The overall performance is usually decided by the surface quality. Abrasive flow machining (AFM technology can effectively improve the surface quality of the parts. In order to discuss the mechanism and technology of abrasive flow machining nonlinear tube, the nozzle is picked up as the researching object, and the self-designed polishing liquid is employed to make research on the key technological parameters of abrasive flow machining linear tube. Technological parameters’ impact on surface quality of the parts through the nozzle surface topography and scanning electron microscopy (SEM map is explored. It is experimentally confirmed that abrasive flow machining can significantly improve surface quality of nonlinear runner, and experimental results can provide technical reference to optimizing study of abrasive flow machining theory.

Moving-shot versus fixed electrode techniques for radiofrequency ablation: Comparison in an ex-vivo bovine liver tissue model

International Nuclear Information System (INIS)

Ha, Eun Ju; Baek, Jung Hwan; Lee, Jeong Hyun

2014-01-01

To compare the ablation characteristics of the moving-shot technique (MST) and the fixed electrode technique (FET) for radiofrequency (RF) ablation in an ex-vivo bovine liver tissue model. We performed RF ablation using FET in 110 bovine liver blocks using 11 different ablation times ranging from 5 seconds to 5 minutes (10 blocks per each time duration). Ten bovine liver blocks at each ablation time of 1- or 2-minute, were ablated with MST, which treated conceptual ablation units by moving the electrode tip. We evaluated the ablation volume obtained with FET across ablation time lengths. The results of FET and MST performed with the same ablation time lengths, i.e., 1- and 2-minute ablation time were also compared. The ablation volume achieved with FET gradually increased with increasing ablation time; however, the pair-wise statistical comparison between 2 neighboring ablation time lengths was not significant after 30 seconds. MST with either 1- or 2-minute ablation time achieved larger ablation volumes (1.1 +/- 0.2 mL vs. 2.7 +/- 0.3 mL, p < 0.001; and 1.4 +/- 0.2 mL vs. 5.6 +/- 0.4 mL, p < 0.001, respectively), longer true RF times (46.7 +/- 4.6 seconds vs. 60 seconds, p < 0.001; and 64.8 +/- 4.6 seconds vs. 120 seconds, p < 0.001, respectively), fewer numbers of RF cut-offs (1.6 +/- 0.5 vs. 0, p < 0.001; and 5.5 +/- 0.5 vs. 0, p < 0.001, respectively), and greater energy deposition (2050.16 +/- 209.2 J vs. 2677.76 +/- 83.68 J, p < 0.001; and 2970.64 +/- 376.56 J vs. 5564.72 +/- 5439.2 J, p < 0.001, respectively), than FET. The MST can achieve a larger ablation volume by preventing RF cut-off, compared with the FET in an ex-vivo bovine liver model.

Systematic review of the synergist muscle ablation model for compensatory hypertrophy.

Science.gov (United States)

Terena, Stella Maris Lins; Fernandes, Kristianne Porta Santos; Bussadori, Sandra Kalill; Deana, Alessandro Melo; Mesquita-Ferrari, Raquel Agnelli

2017-02-01

The aim was to evaluate the effectiveness of the experimental synergists muscle ablation model to promote muscle hypertrophy, determine the period of greatest hypertrophy and its influence on muscle fiber types and determine differences in bilateral and unilateral removal to reduce the number of animals used in this model. Following the application of the eligibility criteria for the mechanical overload of the plantar muscle in rats, nineteen papers were included in the review. The results reveal a greatest hypertrophy occurring between days 12 and 15, and based on the findings, synergist muscle ablation is an efficient model for achieving rapid hypertrophy and the contralateral limb can be used as there was no difference between unilateral and bilateral surgery, which reduces the number of animals used in this model. This model differs from other overload models (exercise and training) regarding the characteristics involved in the hypertrophy process (acute) and result in a chronic muscle adaptation with selective regulation and modification of fast-twitch fibers in skeletal muscle. This is an efficient and rapid model for compensatory hypertrophy.

Modelling of pulsed electron beam induced graphite ablation: Sublimation versus melting

Science.gov (United States)

Ali, Muddassir; Henda, Redhouane

2017-12-01

Pulsed electron beam ablation (PEBA) has recently emerged as a very promising technique for the deposition of thin films with superior properties. Interaction of the pulsed electron beam with the target material is a complex process, which consists of heating, phase transition, and erosion of a small portion from the target surface. Ablation can be significantly affected by the nature of thermal phenomena taking place at the target surface, with subsequent bearing on the properties, stoichiometry and structure of deposited thin films. A two stage, one-dimensional heat conduction model is presented to describe two different thermal phenomena accounting for interaction of a graphite target with a polyenergetic electron beam. In the first instance, the thermal phenomena are comprised of heating, melting and vaporization of the target surface, while in the second instance the thermal phenomena are described in terms of heating and sublimation of the graphite surface. In this work, the electron beam delivers intense electron pulses of ∼100 ns with energies up to 16 keV and an electric current of ∼400 A to a graphite target. The temperature distribution, surface recession velocity, ablated mass per unit area, and ablation depth for the graphite target are numerically simulated by the finite element method for each case. Based on calculation findings and available experimental data, ablation appears to occur mainly in the regime of melting and vaporization from the surface.

A preoperative mathematic model for computed tomographic guided microwave ablation treatment of hepatic dome tumors.

Science.gov (United States)

Gao, Fei; Wang, Guo-Bao; Xiang, Zhan-Wang; Yang, Bin; Xue, Jing-Bing; Mo, Zhi-Qiang; Zhong, Zhi-Hui; Zhang, Tao; Zhang, Fu-Jun; Fan, Wei-Jun

2016-05-03

This study sought to prospectively evaluate the feasibility and safety of a preoperative mathematic model for computed tomographic(CT) guided microwave(MW) ablation treatment of hepatic dome tumors. This mathematic model was a regular cylinder quantifying appropriate puncture routes from the bottom up. A total of 103 patients with hepatic dome tumors were enrolled and randomly divided into 2 groups based on whether this model was used or not: Group A (using the model; n = 43) versus Group B (not using the model; n = 60). All tumors were treated by CT-guided MW ablation and follow-up contrast CT were reviewed. The average number of times for successful puncture, average ablation time, and incidence of right shoulder pain were less in Group A than Group B (1.4 vs. 2.5, P = 0.001; 8.8 vs. 11.1 minutes, P = 0.003; and 4.7% vs. 20%, P = 0.039). The technical success rate was higher in Group A than Group B (97.7% vs. 85.0%, P = 0.032). There were no significant differences between the two groups in primary and secondary technique efficacy rates (97.7% vs. 88.3%, P = 0.081; 90.0% vs. 72.7%, P = 0.314). No major complications occurred in both groups. The mathematic model of regular cylinder is feasible and safe for CT-guided MW ablation in treating hepatic dome tumors.

A Review on Parametric Analysis of Magnetic Abrasive Machining Process

Science.gov (United States)

Khattri, Krishna; Choudhary, Gulshan; Bhuyan, B. K.; Selokar, Ashish

2018-03-01

The magnetic abrasive machining (MAM) process is a highly developed unconventional machining process. It is frequently used in manufacturing industries for nanometer range surface finishing of workpiece with the help of Magnetic abrasive particles (MAPs) and magnetic force applied in the machining zone. It is precise and faster than conventional methods and able to produce defect free finished components. This paper provides a comprehensive review on the recent advancement of MAM process carried out by different researcher till date. The effect of different input parameters such as rotational speed of electromagnet, voltage, magnetic flux density, abrasive particles size and working gap on the performances of Material Removal Rate (MRR) and surface roughness (Ra) have been discussed. On the basis of review, it is observed that the rotational speed of electromagnet, voltage and mesh size of abrasive particles have significant impact on MAM process.

Evaluation of a novel cryoballoon swipe ablation system in bench, porcine, and human esophagus models

NARCIS (Netherlands)

Louie, B. E.; Hofstetter, W.; Triadafilopoulos, G.; Weusten, B. L.

2018-01-01

Current ablation devices for dysplastic Barrett's esophagus are effective but have significant limitations. This pilot study aims to evaluate the safety, feasibility, and dose response of a novel cryoballoon swipe ablation system (CbSAS) in three experimental in vitro and in vivo models. CbSAS is a

Decontamination of Steam Generator tube using Abrasive Blasting Technology

International Nuclear Information System (INIS)

Min, B. Y.; Kim, G. N.; Choi, W. K.; Lee, K. W.; Kim, D. H.; Kim, K. H.; Kim, B. T.

2010-01-01

As a part of a technology development of volume reduction and self disposal for large metal waste project, We at KAERI and our Sunkwang Atomic Energy Safety (KAES) subcontractor colleagues are demonstrating radioactively contaminated steam generator tube by abrasive blasting technology at Kori-1 NPP. A steam generator is a crucial component in a PWR (pressurized Water Reactor). It is the crossing between the primary, contaminated, circuit and the secondary waste-steam circuit. The heat from the primary reactor coolant loop is transferred to the secondary side in thousands of small tubes. Due to several problems in the material of those tube, like SCC (Stress Corrosion Cracking), insufficient control in water chemistry, which can be cause of tube leakage, more and more steam generators are replaced today. Only in Korea, already 2 of them are replaced and will be replaced in the near future. The retired 300 ton heavy Steam generator was stored at the storage waste building of Kori NPP site. The steam generator waste has a large volume, so that it is necessary to reduce its volume by decontamination. A waste reduction effect can be obtained through decontamination of the inner surface of a steam generator. Therefore, it is necessary to develop an optimum method for decontamination of the inner surface of bundle tubes. The dry abrasive blasting is a very interesting technology for the realization of three-dimensional microstructures in brittle materials like glass or silicon. Dry abrasive blasting is applicable to most surface materials except those that might be shattered by the abrasive. It is most effective on flat surface and because the abrasive is sprayed and can also applicable on 'hard to reach' areas such as inner tube ceilings or behind equipment. Abrasive decontamination techniques have been applied in several countries, including Belgium, the CIS, France, Germany, Japan, the UK and the USA

Innovative decontamination technology by abrasion in vibratory vessels

International Nuclear Information System (INIS)

Fabbri, Silvio; Ilarri, Sergio

2007-01-01

Available in abstract form only. Full text of publication follows: The possibility of using conventional vibratory vessel technology as a decontamination technique is the motivation for the development of this project. The objective is to explore the feasibility of applying the vibratory vessel technology for decontamination of radioactively-contaminated materials such as pipes and metal structures. The research and development of this technology was granted by the U.S. Department of Energy (DOE). Abrasion processes in vibratory vessels are widely used in the manufacture of metals, ceramics, and plastics. Samples to be treated, solid abrasive media and liquid media are set up into a vessel. Erosion results from the repeated impact of the abrasive particles on the surface of the body being treated. A liquid media, generally detergents or surfactants aid the abrasive action. The amount of material removed increases with the time of treatment. The design and construction of the machine were provided by Vibro, Argentina private company. Tests with radioactively-contaminated aluminum tubes and a stainless steel bar, were performed at laboratory level. Tests showed that it is possible to clean both the external and the internal surface of contaminated tubes. Results show a decontamination factor around 10 after the first 30 minutes of the cleaning time. (authors)

Artificial evolutionary approaches to produce smoother surface in magnetic abrasive finishing of hardened AISI 52100 steel

Energy Technology Data Exchange (ETDEWEB)

Teimouri, Reza; Baseri, Hamid [Babol University of Technology, Babol (Iran, Islamic Republic of)

2013-02-15

In this work, two models of feed forward back-propagation neural network (FFBP-NN) and adaptive neuro-fuzzy inference system (ANFIS) have been developed to predict the performance of magnetic abrasive finishing process, based on experimental data of literature. Input parameters of process are electromagnet's voltage, mesh number of abrasive particles, poles rotational speed and weight percent of abrasive particles, and also the output is percentage of surface roughness variation. In order to select the best model, a comparison between developed models has been done based on their mean absolute error (MAE) and root mean square error (RMSE). Moreover, optimization methods based on simulated annealing (SA) and particle swarm optimization (PSO) algorithms were used to maximize the percent of surface roughness variation and select the optimal process parameters. Results indicated that the models based on artificial intelligence predict much more precise values with respect to predictive regression model developed in main literature. Also, the ANFIS model had a lowest value of MAE and RMSE with respect to others. So it was used as an objective function to maximize the surface roughness variation by using SA and PSO. Comparison between the obtained optimal solutions and analysis of results in main literature indicated that SA and PSO could find the optimal answers logically and precisely.

Abrasive wear of enamel by bioactive glass-based toothpastes.

Science.gov (United States)

Mahmood, Asad; Mneimne, Mohammed; Zou, Li Fong; Hill, Robert G; Gillam, David G

2014-10-01

To determine the abrasivity of a 45S5 bioactive glass based toothpaste on enamel as a function of the particle size and shape of the glass. 45S5 glass was synthesized ground and sieved to give various particle sized fractions toothpastes and their tooth brush abrasivity measured according to BS EN ISO11609 methodology. Enamel loss increased with increasing particle size. The percussion milled powder exhibited particles that had sharp edges and the pastes were significantly more abrasive than the pastes made with round ball milled powders. One interesting observation made during the present study was that there was preferential wear of the enamel at the dentin-enamel junction (DEJ), particularly with the coarse particle sized pastes.

Abrasion Resistance of Nano Silica Modified Roller Compacted Rubbercrete: Cantabro Loss Method and Response Surface Methodology Approach

Science.gov (United States)

Adamu, Musa; Mohammed, Bashar S.; Shafiq, Nasir

2018-04-01

Roller compacted concrete (RCC) when used for pavement is subjected to skidding/rubbing by wheels of moving vehicles, this causes pavement surface to wear out and abrade. Therefore, abrasion resistance is one of the most important properties of concern for RCC pavement. In this study, response surface methodology was used to design, evaluate and analyze the effect of partial replacement of fine aggregate with crumb rubber, and addition of nano silica on the abrasion resistance of roller compacted rubbercrete (RCR). RCR is the terminology used for RCC pavement where crumb rubber was used as partial replacement to fine aggregate. The Box-Behnken design method was used to develop the mixtures combinations using 10%, 20%, and 30% crumb rubber with 0%, 1%, and 2% nano silica. The Cantabro loss method was used to measure the abrasion resistance. The results showed that the abrasion resistance of RCR decreases with increase in crumb rubber content, and increases with increase in addition of nano silica. The analysis of variance shows that the model developed using response surface methodology (RSM) has a very good degree of correlation, and can be used to predict the abrasion resistance of RCR with a percentage error of 5.44%. The combination of 10.76% crumb rubber and 1.59% nano silica yielded the best combinations of RCR in terms of abrasion resistance of RCR.

Comparative evaluation of enamel abrasivity of different commercially available dentifrices – An In vitro Study

Directory of Open Access Journals (Sweden)

Rupali Athawale

2018-01-01

Full Text Available Background: Toothbrushing with toothpaste is a major contributor to dental abrasion. A number of factors such as abrasivity and concentration of the toothpaste, brushing frequency, brushing duration, force of brushing, and toothbrush bristle stiffness have a potential impact on the abrasion process of dental hard tissue. However, the abrasivity of the toothpaste is the most important parameter that affects the abrasion process of dental hard tissue. Aims: This study aims to evaluate the maximum and mean enamel abrasivity of commercially available dentifrices such as Colgate total®, Pepsodent whitening®, Vicco vajradanti®, Dabur red® in primary and permanent teeth. Materials and Methods: Human extracted 60 primary and 60 permanent teeth were randomly selected based on the inclusion criteria. Teeth were sectioned at cementoenamel junction using diamond disc and mounted in an acrylic resin blocks. Baseline profilometric measurements were recorded for all the samples. Four commonly used dentifrices were selected and labeled as Group A (Colgate Total®, B (Pepsodent Whitening®, C (Vicco Vajradanti®, and D (Dabur Red®. Toothpaste slurry was prepared. Tooth specimens were brushed in vitro using a customized brushing machine. After toothbrushing, profilometric measurements were obtained, and the differences in readings served as proxy measure to assess surface abrasion. Data were collected and analyzed using student t-test and ANOVA test. Student t-test was used to compare the enamel abrasivity prebrushing and postbrushing, and ANOVA was used to compare the enamel abrasivity among the four different commercially available toothpastes. Results: In permanent teeth, all the toothpastes were found to cause significant enamel abrasion (P = 0.000 and a significant variation was observed when maximum (P = 0.008 and mean (P = 0.036 enamel abrasivity of these toothpastes were compared. In primary teeth also, all the toothpastes caused significant abrasion

Automated planning of ablation targets in atrial fibrillation treatment

Science.gov (United States)

Keustermans, Johannes; De Buck, Stijn; Heidbüchel, Hein; Suetens, Paul

2011-03-01

Catheter based radio-frequency ablation is used as an invasive treatment of atrial fibrillation. This procedure is often guided by the use of 3D anatomical models obtained from CT, MRI or rotational angiography. During the intervention the operator accurately guides the catheter to prespecified target ablation lines. The planning stage, however, can be time consuming and operator dependent which is suboptimal both from a cost and health perspective. Therefore, we present a novel statistical model-based algorithm for locating ablation targets from 3D rotational angiography images. Based on a training data set of 20 patients, consisting of 3D rotational angiography images with 30 manually indicated ablation points, a statistical local appearance and shape model is built. The local appearance model is based on local image descriptors to capture the intensity patterns around each ablation point. The local shape model is constructed by embedding the ablation points in an undirected graph and imposing that each ablation point only interacts with its neighbors. Identifying the ablation points on a new 3D rotational angiography image is performed by proposing a set of possible candidate locations for each ablation point, as such, converting the problem into a labeling problem. The algorithm is validated using a leave-one-out-approach on the training data set, by computing the distance between the ablation lines obtained by the algorithm and the manually identified ablation points. The distance error is equal to 3.8+/-2.9 mm. As ablation lesion size is around 5-7 mm, automated planning of ablation targets by the presented approach is sufficiently accurate.

Pleurectomy versus pleural abrasion for primary spontaneous pneumothorax in children.

Science.gov (United States)

Joharifard, Shahrzad; Coakley, Brian A; Butterworth, Sonia A

2017-05-01

Primary spontaneous pneumothorax (PSP) represents a common indication for urgent surgical intervention in children. First episodes are often managed with thoracostomy tube, whereas recurrent episodes typically prompt surgery involving apical bleb resection and pleurodesis, either via pleurectomy or pleural abrasion. The purpose of this study was to assess whether pleurectomy or pleural abrasion was associated with lower postoperative recurrence. The records of patients undergoing surgery for PSP between February 2005 and December 2015 were retrospectively reviewed. Recurrence was defined as an ipsilateral pneumothorax requiring surgical intervention. Bivariate logistic regressions were used to identify factors associated with recurrence. Fifty-two patients underwent 64 index operations for PSP (12 patients had surgery for contralateral pneumothorax, and each instance was analyzed separately). The mean age was 15.7±1.2years, and 79.7% (n=51) of patients were male. In addition to apical wedge resection, 53.1% (n=34) of patients underwent pleurectomy, 39.1% (n=25) underwent pleural abrasion, and 7.8% (n=5) had no pleural treatment. The overall recurrence rate was 23.4% (n=15). Recurrence was significantly lower in patients who underwent pleurectomy rather than pleural abrasion (8.8% vs. 40%, p<0.01). In patients who underwent pleural abrasion without pleurectomy, the relative risk of recurrence was 2.36 [1.41-3.92, p<0.01]. Recurrence of PSP is significantly reduced in patients undergoing pleurectomy compared to pleural abrasion. Level III, retrospective comparative therapeutic study. Copyright © 2017 Elsevier Inc. All rights reserved.

Controls on wind abrasion patterns through a fractured bedrock landscape

Science.gov (United States)

Perkins, J. P.; Finnegan, N. J.

2017-12-01

Wind abrasion is an important geomorphic process for understanding arid landscape evolution on Earth and interpreting the post-fluvial history of Mars. Both the presence and orientation of wind-abraded landforms provide potentially important constraints on paleo-climatic conditions; however, such interpretations can be complicated by lithologic and structural heterogeneity. To explore the influence of pre-existing structure on wind abrasion, we exploit a natural experiment along the 10.2 Ma Lower Rio San Pedro ignimbrite in northern Chile. Here, a 3.2 Ma andesite flow erupted from Cerro de las Cuevas and deposited atop the ignimbrite, supplying wind-transportable sediment and initiating a phase of downwind abrasion. Additionally, the lava flow provides a continually varying degree of upwind topographic shielding along the ignimbrite that is reflected in a range of surface morphologies. Where fully shielded the ignimbrite surface is partially blanketed by sediment. However, as relief decreases the surface morphology shifts from large polygonal structures that emerge due to the concentration of wind abrasion along pre-existing fracture sets, to polygons that are bisected by wind-parallel grooves that cross-cut fracture sets, to linear sets of yardangs. We reconstruct the ignimbrite surface using a high-resolution digital elevation model, and calculate erosion rates ranging from 0.002 to 0.45 mm/kyr that vary strongly with degree of topographic shielding (R2 = 0.97). We use measured abrasion rates together with nearby weather station data to estimate the nondimensional Rouse number and Inertial Parameter for a range of particle sizes. From these calculations, we hypothesize that the change from fracture-controlled to flow-controlled morphology reflects increases in the grain size and inertia of particles in the suspension cloud. Where the ignimbrite experiences persistent high winds, large particles may travel in suspension and are largely insensitive to topographic

CRAC2 model description

International Nuclear Information System (INIS)

Ritchie, L.T.; Alpert, D.J.; Burke, R.P.; Johnson, J.D.; Ostmeyer, R.M.; Aldrich, D.C.; Blond, R.M.

1984-03-01

The CRAC2 computer code is a revised version of CRAC (Calculation of Reactor Accident Consequences) which was developed for the Reactor Safety Study. This document provides an overview of the CRAC2 code and a description of each of the models used. Significant improvements incorporated into CRAC2 include an improved weather sequence sampling technique, a new evacuation model, and new output capabilities. In addition, refinements have been made to the atmospheric transport and deposition model. Details of the modeling differences between CRAC2 and CRAC are emphasized in the model descriptions

Laboratory Simulations of Micrometeoroid Ablation

Science.gov (United States)

Thomas, Evan Williamson

Each day, several tons of meteoric material enters Earth's atmosphere, the majority of which consist of small dust particles (micrometeoroids) that completely ablate at high altitudes. The dust input has been suggested to play a role in a variety of phenomena including: layers of metal atoms and ions, nucleation of noctilucent clouds, effects on stratospheric aerosols and ozone chemistry, and the fertilization of the ocean with bio-available iron. Furthermore, a correct understanding of the dust input to the Earth provides constraints on inner solar system dust models. Various methods are used to measure the dust input to the Earth including satellite detectors, radar, lidar, rocket-borne detectors, ice core and deep-sea sediment analysis. However, the best way to interpret each of these measurements is uncertain, which leads to large uncertainties in the total dust input. To better understand the ablation process, and thereby reduce uncertainties in micrometeoroid ablation measurements, a facility has been developed to simulate the ablation of micrometeoroids in laboratory conditions. An electrostatic dust accelerator is used to accelerate iron particles to relevant meteoric velocities (10-70 km/s). The particles are then introduced into a chamber pressurized with a target gas, and they partially or completely ablate over a short distance. An array of diagnostics then measure, with timing and spatial resolution, the charge and light that is generated in the ablation process. In this thesis, we present results from the newly developed ablation facility. The ionization coefficient, an important parameter for interpreting meteor radar measurements, is measured for various target gases. Furthermore, experimental ablation measurements are compared to predictions from commonly used ablation models. In light of these measurements, implications to the broader context of meteor ablation are discussed.

Systematic review of the synergist muscle ablation model for compensatory hypertrophy

Directory of Open Access Journals (Sweden)

Stella Maris Lins Terena

Full Text Available Summary Objective: The aim was to evaluate the effectiveness of the experimental synergists muscle ablation model to promote muscle hypertrophy, determine the period of greatest hypertrophy and its influence on muscle fiber types and determine differences in bilateral and unilateral removal to reduce the number of animals used in this model. Method: Following the application of the eligibility criteria for the mechanical overload of the plantar muscle in rats, nineteen papers were included in the review. Results: The results reveal a greatest hypertrophy occurring between days 12 and 15, and based on the findings, synergist muscle ablation is an efficient model for achieving rapid hypertrophy and the contralateral limb can be used as there was no difference between unilateral and bilateral surgery, which reduces the number of animals used in this model. Conclusion: This model differs from other overload models (exercise and training regarding the characteristics involved in the hypertrophy process (acute and result in a chronic muscle adaptation with selective regulation and modification of fast-twitch fibers in skeletal muscle. This is an efficient and rapid model for compensatory hypertrophy.

Surface characterization of current composites after toothbrush abrasion.

Science.gov (United States)

Takahashi, Rena; Jin, Jian; Nikaido, Toru; Tagami, Junji; Hickel, Reinhard; Kunzelmann, Karl-Heinz

2013-01-01

The present study was designed to evaluate the surface roughness and the gloss of current composites before and after toothbrush abrasion. We assessed forty dimensionally standardized composite specimens (n=8/group) from five composites: two nanohybrids (i. e., IPS Empress Direct Enamel and IPS Empress Direct Dentin), two microhybrids (i. e., Clearfil AP-X and Filtek Z250) and one organically modified ceramics (Admira). All of the specimens were polished with 4000-grid silicon carbide papers. Surface roughness was measured with a profilometer and gloss was measured with a glossmeter before and after powered toothbrush abrasion with a 1:1 slurry (dentifrice/tap water) at 12,000 strokes in a toothbrush simulator. There was a significant increase in the surface roughness and a reduction in gloss after toothbrush abrasion in all of the composites except Clearfil AP-X (pgloss (R(2)=0.191, p<0.001).

All fiber cladding mode stripper with uniform heat distribution and high cladding light loss manufactured by CO2 laser ablation

Science.gov (United States)

Jebali, M. A.; Basso, E. T.

2018-02-01

Cladding mode strippers are primarily used at the end of a fiber laser cavity to remove high-power excess cladding light without inducing core loss and beam quality degradation. Conventional manufacturing methods of cladding mode strippers include acid etching, abrasive blasting or laser ablation. Manufacturing of cladding mode strippers using laser ablation consist of removing parts of the cladding by fused silica ablation with a controlled penetration and shape. We present and characterize an optimized cladding mode stripper design that increases the cladding light loss with a minimal device length and manufacturing time. This design reduces the localized heat generation by improving the heat distribution along the device. We demonstrate a cladding mode stripper written on a 400um fiber with cladding light loss of 20dB, with less than 0.02dB loss in the core and minimal heating of the fiber and coating. The manufacturing process of the designed component is fully automated and takes less than 3 minutes with a very high throughput yield.

Baking soda as an abrasive in toothpastes: Mechanism of action and safety and effectiveness considerations.

Science.gov (United States)

Hara, Anderson T; Turssi, Cecilia P

2017-11-01

Toothpastes can be formulated with different abrasive systems, depending on their intended clinical application. This formulation potentially affects their effectiveness and safety and, therefore, requires proper understanding. In this article, the authors focused on abrasive aspects of toothpastes containing sodium bicarbonate (baking soda), which have gained considerable attention because of their low abrasivity and good compatibility, while providing clinical effectiveness (further detailed in the other articles of this special issue). The authors first appraised the role of toothpaste abrasivity on tooth wear, exploring some underlying processes and the existing methods to determine toothpaste abrasivity. The authors reviewed the available data on the abrasivity of toothpastes containing baking soda and reported a summary of findings highlighting the clinical implications. On the basis of the collected evidence, baking soda has an intrinsic low-abrasive nature because of its comparatively lower hardness in relation to enamel and dentin. Baking soda toothpastes also may contain other ingredients, which can increase their stain removal effectiveness and, consequently, abrasivity. Even those formulations have abrasivity well within the safety limit regulatory agencies have established and, therefore, can be considered safe. Copyright © 2017 American Dental Association. Published by Elsevier Inc. All rights reserved.

Demonstration experience with an abrasive blasting technique for decontaminating concrete pads

International Nuclear Information System (INIS)

Devgun, J.S.; Land, R.R.; Doane, R.W.

1990-01-01

A demonstration was performed for decontaminating a radioactivity contaminated concrete pad with a portable abrasive blasting system. The system utilizes a rotating blast wheel that scours the concrete surface with metal abrasive. The metal abrasive, pulverized concrete dust, and contaminants rebound into a separator chamber. The reusable metal abrasive is recycled, and the pulverized media are removed to an integral dust collection system. The exhaust is HEPA filtered to minimize release of airborne contaminants. However, the technique had limited success in reducing contamination around the cracks and seams in the concrete where the higher activity levels of contamination were detected during the radiological survey before the cleanup. The technique can be successful and cost-effective in decontaminating large areas of low contamination; however, careful characterization and planning are necessary. 3 refs., 3 figs., 1 tabs

Abrasion behavior of graphite pebble in lifting pipe of pebble-bed HTR

Energy Technology Data Exchange (ETDEWEB)

Shen, Ke; Su, Jiageng [Institute of Nuclear and New Energy Technology, Advanced Nuclear Energy Technology Cooperation Innovation Center, The Key Laboratory of Advanced Nuclear Engineering and Safety, Ministry of Education, Beijing 10084 (China); Zhou, Hongbo [Institute of Nuclear and New Energy Technology, Advanced Nuclear Energy Technology Cooperation Innovation Center, The Key Laboratory of Advanced Nuclear Engineering and Safety, Ministry of Education, Beijing 10084 (China); Chinergy Co., LTD., Beijing 100193 (China); Peng, Wei; Liu, Bing [Institute of Nuclear and New Energy Technology, Advanced Nuclear Energy Technology Cooperation Innovation Center, The Key Laboratory of Advanced Nuclear Engineering and Safety, Ministry of Education, Beijing 10084 (China); Yu, Suyun, E-mail: suyuan@tsinghua.edu.cn [Center for Combustion Energy, The Key Laboratory for Thermal Science and Power Engineering, Ministry of Educations, Tsinghua University, Beijing 10084 (China)

2015-11-15

Highlights: • Quantitative determination of abrasion rate of graphite pebbles in different lifting velocities. • Abrasion behavior of graphite pebble in helium, air and nitrogen. • In helium, intensive collisions caused by oscillatory motion result in more graphite dust production. - Abstract: A pebble-bed high-temperature gas-cooled reactor (pebble-bed HTR) uses a helium coolant, graphite core structure, and spherical fuel elements. The pebble-bed design enables on-line refueling, avoiding refueling shutdowns. During circulation process, the pebbles are lifted pneumatically via a stainless steel lifting pipe and reinserted into the reactor. Inevitably, the movement of the fuel elements as they recirculate in the reactor produces graphite dust. Mechanical wear is the primary source of graphite dust production. Specifically, the sources are mechanisms of pebble–pebble contact, pebble–wall (structural graphite) contact, and fuel handling (pebble–metal abrasion). The key contribution to graphite dust production is from the fuel handling system, particularly from the lifting pipe. During pneumatic lift, graphite pebbles undergo multiple collisions with the stainless steel lifting pipe, thereby causing abrasion of the graphite pebbles and producing graphite dust. The present work explored the abrasion behavior of graphite pebble in the lifting pipe by measuring the abrasion rate at different lifting velocities. The abrasion rate of the graphite pebble in helium was found much higher than those in air and nitrogen. This gas environment effect could be explained by either tribology behavior or dynamic behavior. Friction testing excluded the possibility of tribology reason. The dynamic behavior of the graphite pebble was captured by analysis of the audio waveforms during pneumatic lift. The analysis results revealed unique dynamic behavior of the graphite pebble in helium. Oscillation and consequently intensive collisions occur during pneumatic lift, causing

Lung scintigraphy evaluation in workers exposed to abrasive dusts

International Nuclear Information System (INIS)

Terra Filho, Mario

1995-01-01

The production process of abrasives use aluminium, or silicon carbide a synthetic material with a hardness only slightly less than that of a diamond. It is popularly known as carborundum since it was first manufactured as an abrasive in 1891, produced by the fusion of high grade silica and petroleum coke with sawdust. For many years silicon carbide was thought not to give rise to pulmonary lesions. Recently several researchers suggested the existence of a carborundum pneumoconiosis. The aim of this study was to evaluate the role of the pulmonary clearance of 99m Technetium chelated to diethylene-triamine penta-acetate ( 99m Tc DTPA), and 67 Gallium lung scanning in workers exposed to abrasive dusts. Thirty seven subjects, 13 smokers and 24 nonsmokers and ex smokers were studied. In 32 (86,48%) 67 Gallium lung scanning was positive including 13 (40,62%) retired workers. We conclude that non smoking workers of abrasives plants have a pulmonary alveolar epithelial permeability disturbance similar as observed in smoking workers and smoking controls. Most workers, ex-workers of these industries and in patients with carborundum pneumoconiosis there is an evidence of pulmonary inflammation measured with abnormal 67 Gallium lung scan. (author)

Measurement of nanoparticle removal by abrasion

International Nuclear Information System (INIS)

Guiot, Arnaud; Golanski, Luana; Tardif, Francois

2009-01-01

A strong release limitation of single nanoparticles from commercial manufactured 'nanoproducts' is necessary to decrease potential exposure risks of consumers and represents also a pragmatic way to facilitate acceptance for nanomaterial commercialization before obtaining definitive toxicological results. So, it is of prime importance to know how to characterize the release of small materials during usage solicitations such as mechanical, thermal, UV stress: are they single nanoparticles, aggregates or nanoparticles included in a bigger piece of the matrix? In the frame of NanoSafe2 project, CEA developed and qualified a specific bench test where the material to be tested is mechanically solicited by abrasion using a normalized Taber equipment. The first results show that nanofillers can be released in usage by abrasion for non optimised nanoproducts.

Mathematical 3D modelling and sensitivity analysis of multipolar radiofrequency ablation in the spine.

Science.gov (United States)

Matschek, Janine; Bullinger, Eric; von Haeseler, Friedrich; Skalej, Martin; Findeisen, Rolf

2017-02-01

Radiofrequency ablation is a valuable tool in the treatment of many diseases, especially cancer. However, controlled heating up to apoptosis of the desired target tissue in complex situations, e.g. in the spine, is challenging and requires experienced interventionalists. For such challenging situations a mathematical model of radiofrequency ablation allows to understand, improve and optimise the outcome of the medical therapy. The main contribution of this work is the derivation of a tailored, yet expandable mathematical model, for the simulation, analysis, planning and control of radiofrequency ablation in complex situations. The dynamic model consists of partial differential equations that describe the potential and temperature distribution during intervention. To account for multipolar operation, time-dependent boundary conditions are introduced. Spatially distributed parameters, like tissue conductivity and blood perfusion, allow to describe the complex 3D environment representing diverse involved tissue types in the spine. To identify the key parameters affecting the prediction quality of the model, the influence of the parameters on the temperature distribution is investigated via a sensitivity analysis. Simulations underpin the quality of the derived model and the analysis approach. The proposed modelling and analysis schemes set the basis for intervention planning, state- and parameter estimation, and control. Copyright © 2016. Published by Elsevier Inc.

Effects of magnetic resonance-guided high-intensity focused ultrasound ablation on bone mechanical properties and modeling

NARCIS (Netherlands)

Yeoh, S.Y.; Arias Moreno, A.J.; Rietbergen, van B.; Hoeve, ter N.D.; Diest, van P.J.; Grull, H.

2015-01-01

Background Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) is a promising technique for palliative treatment of bone pain. In this study, the effects of MR-HIFU ablation on bone mechanics and modeling were investigated. Methods A total of 12 healthy rat femurs were ablated

Influence of Corrosion on the Abrasion of Cutter Steels Used in TBM Tunnelling

Science.gov (United States)

Espallargas, N.; Jakobsen, P. D.; Langmaack, L.; Macias, F. J.

2015-01-01

Abrasion on tunnel boring machine (TBM) cutters may be critical in terms of project duration and costs. Several researchers are currently studying the degradation of TBM cutter tools used for excavating hard rock, soft ground and loose soil. So far, the primary focus of this research has been directed towards abrasive wear. Abrasive wear is a very common process in TBM excavation, but with a view to the environment in which the tools are working, corrosion may also exert an influence. This paper presents a selection of techniques that can be used to evaluate the influence of corrosion on abrasion on TBM excavation tools. It also presents the influence of corrosion on abrasive wear for some initial tests, with constant steel and geomaterial and varying properties of the excavation fluids (soil conditioners, anti-abrasion additives and water). The results indicate that the chloride content in the water media greatly influences the amount of wear, providing evidence of the influence of corrosion on the abrasion of the cutting tools. The presence of conditioning additives tailored to specific rock or soil conditions reduces wear. However, when chloride is present in the water, the additives minimise wear rates but fail to suppress corrosion of the cutting tools.

Shoe heel abrasion and its possible biomechanical cause: a transversal study with infantry recruits.

Science.gov (United States)

Baumfeld, Daniel; Raduan, Fernando C; Macedo, Benjamim; Silva, Thiago Alexandre Alves; Baumfeld, Tiago; Favato, Danilo Fabrino; de Andrade, Marco Antonio Percope; Nery, Caio

2015-11-19

Excessive shoe heel abrasion is of concern to patients and shoe manufacturers, but little scientific information is available about this feature and its possible causes. The purpose of this study was to relate this phenomenon with biomechanical factors that could predispose to shoe heel abrasion. Ninety-seven recruits (median age 25) were enrolled in this study. Shoe abrasion was assessed manually with a metric plastic tape on the posterior part of the heel that comes in contact with the ground. The number of sprains, foot alignment, and calf muscle shortening (Silfverskiold test) was also assessed in order to relate it with shoe heel abrasion. After using our exclusion criteria, 86 recruits and 172 were considered for this study. The most common abrasion site was the lateral portion of the heel surface (50 %). Forty-four percent of the participants had neutral hind-foot alignment and 39 % had valgus alignment. Twenty-six (30 %) patients have had previous ankle or foot sprains. Neutral foot was related with less calf muscle shortening. On the other hand, valgus hind-foot alignment was more associated with Achilles shortening (p study was able to correlate shoe heel abrasion with biomechanical causes (neutral alignment-uniform abrasion/varus alignment-central and lateral abrasion). More effort has to be done to continue evaluating outsole abrasion with its possible biomechanical cause in order to predict and treat possible associated injuries.

Voltage and pace-capture mapping of linear ablation lesions overestimates chronic ablation gap size.

Science.gov (United States)

O'Neill, Louisa; Harrison, James; Chubb, Henry; Whitaker, John; Mukherjee, Rahul K; Bloch, Lars Ølgaard; Andersen, Niels Peter; Dam, Høgni; Jensen, Henrik K; Niederer, Steven; Wright, Matthew; O'Neill, Mark; Williams, Steven E

2018-04-26

Conducting gaps in lesion sets are a major reason for failure of ablation procedures. Voltage mapping and pace-capture have been proposed for intra-procedural identification of gaps. We aimed to compare gap size measured acutely and chronically post-ablation to macroscopic gap size in a porcine model. Intercaval linear ablation was performed in eight Göttingen minipigs with a deliberate gap of ∼5 mm left in the ablation line. Gap size was measured by interpolating ablation contact force values between ablation tags and thresholding at a low force cut-off of 5 g. Bipolar voltage mapping and pace-capture mapping along the length of the line were performed immediately, and at 2 months, post-ablation. Animals were euthanized and gap sizes were measured macroscopically. Voltage thresholds to define scar were determined by receiver operating characteristic analysis as voltage, pace-capture, and ablation contact force maps. All modalities overestimated chronic gap size, by 1.4 ± 2.0 mm (ablation contact force map), 5.1 ± 3.4 mm (pace-capture), and 9.5 ± 3.8 mm (voltage mapping). Error on ablation contact force map gap measurements were significantly less than for voltage mapping (P = 0.003, Tukey's multiple comparisons test). Chronically, voltage mapping and pace-capture mapping overestimated macroscopic gap size by 11.9 ± 3.7 and 9.8 ± 3.5 mm, respectively. Bipolar voltage and pace-capture mapping overestimate the size of chronic gap formation in linear ablation lesions. The most accurate estimation of chronic gap size was achieved by analysis of catheter-myocardium contact force during ablation.

Submerged cutting of steel by abrasive water jets

International Nuclear Information System (INIS)

Haferkamp, H.; Louis, H.; Meier, G.

1990-01-01

A special cutting head for underwater use was designed and built. Tests were carried out to find out useful parameters for submerged cutting. With regard to the production of secondary waste the abrasive flow rate had to be minimized. This was achieved by using a small water jet nozzle (up to 0.4 mm diameter) and a high pressure (up to 4000 bar) with an optimal abrasive flow rate of about 5 g/s. In the case of a higher ambient pressure a decrease of the cutting performance was measured. But this decrease is not important regarding decommissioning because the ambient pressure is less than 2 bar. An air mantle nozzle was adapted to the cutting head to improve the working distance under water. The air mantle surrounding the abrasive jet lowers the friction between jet and surrounding water and increases the cutting efficiency in the case of greater working distances. (author)

Technology of magnetic abrasive finishing in machining of difficult-to-machine alloy complex surface

Directory of Open Access Journals (Sweden)

Fujian MA

2016-10-01

Full Text Available The technology of magnetic abrasive finishing is one of the important finishing technologies. Combining with low-frequency vibration and ultrasonic vibration, it can attain higher precision, quality and efficiency. The characteristics and the related current research of magnetic abrasive finishing, vibration assisted magnetic abrasive finishing and ultrasonic assisted magnetic abrasive finishing are introduced. According to the characteristics of the difficult-to-machine alloy's complex surface, the important problems for further study are presented to realize the finishing of complex surface with the technology of magnetic abrasive finishing, such as increasing the machining efficiency by enhancing the magnetic flux density of machining gap and compounding of magnetic energy and others, establishing of the control function during machining and the process planning method for magnetic abrasive finishing of complex surface under the space geometry restraint of complex surface on magnetic pole, etc.

Study of Effect of Impacting Direction on Abrasive Nanometric Cutting Process with Molecular Dynamics.

Science.gov (United States)

Li, Junye; Meng, Wenqing; Dong, Kun; Zhang, Xinming; Zhao, Weihong

2018-01-11

Abrasive flow polishing plays an important part in modern ultra-precision machining. Ultrafine particles suspended in the medium of abrasive flow removes the material in nanoscale. In this paper, three-dimensional molecular dynamics (MD) simulations are performed to investigate the effect of impacting direction on abrasive cutting process during abrasive flow polishing. The molecular dynamics simulation software Lammps was used to simulate the cutting of single crystal copper with SiC abrasive grains at different cutting angles (0 o -45 o ). At a constant friction coefficient, we found a direct relation between cutting angle and cutting force, which ultimately increases the number of dislocation during abrasive flow machining. Our theoretical study reveal that a small cutting angle is beneficial for improving surface quality and reducing internal defects in the workpiece. However, there is no obvious relationship between cutting angle and friction coefficient.

Convergent ablation measurements of plastic ablators in gas-filled rugby hohlraums on OMEGA

Science.gov (United States)

Casner, A.; Jalinaud, T.; Masse, L.; Galmiche, D.

2015-10-01

Indirect-drive implosions experiments were conducted on the Omega Laser Facility to test the performance of uniformly doped plastic ablators for Inertial Confinement Fusion. The first convergent ablation measurements in gas-filled rugby hohlraums are reported. Ignition relevant limb velocities in the range from 150 to 300 μm .n s-1 have been reached by varying the laser drive energy and the initial capsule aspect ratio. The measured capsule trajectory and implosion velocity are in good agreement with 2D integrated simulations and a zero-dimensional modeling of the implosions. We demonstrate experimentally the scaling law for the maximum implosion velocity predicted by the improved rocket model [Y. Saillard, Nucl. Fusion 46, 1017 (2006)] in the high-ablation regime case.

Bach1 gene ablation reduces steatohepatitis in mouse MCD diet model.

Science.gov (United States)

Inoue, Motoki; Tazuma, Susumu; Kanno, Keishi; Hyogo, Hideyuki; Igarashi, Kazuhiko; Chayama, Kazuaki

2011-03-01

Bach1 is a transcriptional repressor of heme oxygenase-1 (HO-1, a.k.a. HSP-32), which is an inducible enzyme and has anti-oxidation/anti-inflammatory properties shown in various models of organ injuries. Since oxidative stress plays a pivotal role in the pathogenesis of nonalcoholic steatohepatitis (NASH), HO-1 induction would be expected to prevent the development of NASH. In this study, we investigated the influence of Bach1 ablation in mice on the progression of NASH in methionine-choline deficient (MCD) diet model. Bach1 ablation resulted in significant induction of HO-1 mRNA and its activity in the liver. When fed MCD diet, Bach1(-/-) mice exhibited negligible hepatic steatosis compared to pronounced steatohepatitis in wild type mice with 6-fold increase in hepatic triglyceride content. Whereas feeding of MCD diet decreased mRNA expressions of peroxisome proliferator-activated receptor (PPAR) α and microsomal triglyceride transfer protein (MTP) in wild type mice, there were no change in Bach1(-/-) mice. In addition, hepatic concentration of malondialdehyde (MDA), a biomarker for oxidative stress as well as plasma alanine aminotransferase (ALT) was significantly lower in Bach1(-/-) mice. These findings suggest that Bach1 ablation exerts hepatoprotective effect against steatohepatitis presumably via HO-1 induction and may be a potential therapeutic target.

Hydrodynamic instabilities in an ablation front

International Nuclear Information System (INIS)

Piriz, A R; Portugues, R F

2004-01-01

The hydrodynamic stability of an ablation front is studied for situations in which the wavelength of the perturbations is larger than the distance to the critical surface where the driving radiation is absorbed. An analytical model is presented, and it shows that under conditions in which the thermal flux is limited within the supercritical region of the ablative corona, the front may behave like a flame or like an ablation front, depending on the perturbation wavelength. For relatively long wavelengths the critical and ablation surfaces practically lump together into a unique surface and the front behaves like a flame, whereas for the shortest wavelengths the ablation front substructure is resolved

Hydrodynamic instabilities in an ablation front

Energy Technology Data Exchange (ETDEWEB)

Piriz, A R; Portugues, R F [E.T.S.I. Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real (Spain)

2004-06-01

The hydrodynamic stability of an ablation front is studied for situations in which the wavelength of the perturbations is larger than the distance to the critical surface where the driving radiation is absorbed. An analytical model is presented, and it shows that under conditions in which the thermal flux is limited within the supercritical region of the ablative corona, the front may behave like a flame or like an ablation front, depending on the perturbation wavelength. For relatively long wavelengths the critical and ablation surfaces practically lump together into a unique surface and the front behaves like a flame, whereas for the shortest wavelengths the ablation front substructure is resolved.

Modeling hydrodynamic instabilities of double ablation fronts in inertial confinement fusion

International Nuclear Information System (INIS)

Yanez, C.; Sanz, J.; Olazabal-Loume, M.; Ibanez, L. F.

2013-01-01

A linear Rayleigh-Taylor instability theory of double ablation (DA) fronts is developed for direct-drive inertial confinement fusion. Two approaches are discussed: an analytical discontinuity model for the radiation dominated regime of very steep DA front structure, and a numerical self-consistent model that covers more general hydrodynamic profiles behaviours. Dispersion relation results are compared to 2D simulations. (authors)

Experimental Investigation on the Material Removal of the Ultrasonic Vibration Assisted Abrasive Water Jet Machining Ceramics

Directory of Open Access Journals (Sweden)

Tao Wang

2017-01-01

Full Text Available The ultrasonic vibration activated in the abrasive water jet nozzle is used to enhance the capability of the abrasive water jet machinery. The experiment devices of the ultrasonic vibration assisted abrasive water jet are established; they are composed of the ultrasonic vibration producing device, the abrasive supplying device, the abrasive water jet nozzle, the water jet intensifier pump, and so on. And the effect of process parameters such as the vibration amplitude, the system working pressure, the stand-off, and the abrasive diameter on the ceramics material removal is studied. The experimental result indicates that the depth and the volume removal are increased when the ultrasonic vibration is added on abrasive water jet. With the increase of vibration amplitude, the depth and the volume of material removal are also increased. The other parameters of the ultrasonic vibration assisted abrasive water jet also have an important role in the improvement of ceramic material erosion efficiency.

Ablation threshold and ablation mechanism transition of polyoxymethylene irradiated by CO2 laser.

Science.gov (United States)

Li, Gan; Cheng, Mousen; Li, Xiaokang

2016-09-01

Polyoxymethylene (POM) decomposes gradually as it is heated up by the irradiation of CO2 laser; the long-chain molecules of POM are broken into short chains, which leads to the lowering of the melting point and the critical temperature of the ablation products. When the product temperature is above the melting point, ablation comes up in the way of vaporization; when the product temperature is higher than the critical temperature, all liquid products are transformed into gas instantly and the ablation mechanism is changed. The laser fluence at which significant ablation is observed is defined as the ablation threshold, and the fluence corresponding to the ablation mechanism changing is denoted as the flyover threshold. In this paper, random pyrolysis is adopted to describe the pyrolytic decomposition of POM, and consequently, the components of the pyrolysis products under different pyrolysis rates are acquired. The Group Contribution method is used to count the thermodynamic properties of the pyrolysis products, and the melting point and the critical temperature of the product mixture are obtained by the Mixing Law. The Knudsen layer relationship is employed to evaluate the ablation mass removal when the product temperature is below the critical temperature. The gas dynamics conservation laws associated with the Jouguet condition are used to calculate the mass removal when the product temperature is higher than the critical temperature. Based on the model, a set of simulations for various laser intensities and lengths are carried out to generalize the relationships between the thresholds and the laser parameters. Besides the ablated mass areal density, which fits the experimental data quite well, the ablation temperature, pyrolysis rate, and product components are also discussed for a better understanding of the ablation mechanism of POM.

Global Modeling of Uranium Molecular Species Formation Using Laser-Ablated Plasmas

Science.gov (United States)

Curreli, Davide; Finko, Mikhail; Azer, Magdi; Armstrong, Mike; Crowhurst, Jonathan; Radousky, Harry; Rose, Timothy; Stavrou, Elissaios; Weisz, David; Zaug, Joseph

2016-10-01

Uranium is chemically fractionated from other refractory elements in post-detonation nuclear debris but the mechanism is poorly understood. Fractionation alters the chemistry of the nuclear debris so that it no longer reflects the chemistry of the source weapon. The conditions of a condensing fireball can be simulated by a low-temperature plasma formed by vaporizing a uranium sample via laser heating. We have developed a global plasma kinetic model in order to model the chemical evolution of U/UOx species within an ablated plasma plume. The model allows to track the time evolution of the density and energy of an uranium plasma plume moving through an oxygen atmosphere of given fugacity, as well as other relevant quantities such as average electron and gas temperature. Comparison of model predictions with absorption spectroscopy of uranium-ablated plasmas provide preliminary insights on the key chemical species and evolution pathways involved during the fractionation process. This project was sponsored by the DoD, Defense Threat Reduction Agency, Grant HDTRA1-16-1-0020. This work was performed in part under the auspices of the U.S. DoE by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Percutaneous radiofrequency thermal ablation of lung VX2 tumors in a rabbit model: evaluation with helical CT findings for the complete and partal ablation

Energy Technology Data Exchange (ETDEWEB)

Jin, Gong Yong; Han, Young Min; Lim, Yeong Su; Jang, Kyu Yun; Lee, Sang Yong; Chung, Gyung Ho [School of Medicine, Chonbuk National Univ., Chonju (Korea, Republic of)

2004-05-01

To evaluate the radiologic findings for complete and partial ablation after percutaneous CT-guided transthoracic radiofrequency ablation (RFA) of lung VX2 tumor implanted in rabbits. Thirteen rabbits with successfully implanted lung VX2 were used. Three rabbits as controls did not receive RFA while the other ten rabbits underwent RFA; 5 complete and 5 partial. RFA was performed using an internally cooled, 17-gauge electrode (Radionics, Burlington, MA) with a 1-cm active tip under CT guidance. Postprocedural CT was performed within 3 days, and we analyzed the ablated size, enhancement pattern, shape, margin, and complications of the complete and partial ablation groups. Rabbits were sacrificed after postprocedural CT with an overdose of ketamine, and pathologic findings of the ablated groups were compared with those of the control group. The size of the ablated lesions and the enhancement pattern differed between the completely and partially ablated groups on chest CT. The size of the ablated lesions was increased by 47.1% in the completely ablated group and by 2.1% in the partially ablated group. In the completely ablated group, VX2 tumor showed absolutely no enhancement, whereas only ablated pulmonary parenchyma outside VX2 showed mild enhancement on enhanced CT. In the partial ablated group, a part of VX2 became strongly enhanced on enhanced CT. On microscopic examination, the completely ablated group demonstrated that a viable tumor cell was not visible. In the partially ablated group, however, a viable tumor cell within the surrounding fibrous capsule on the peripheral area of the VX2 was observed. The important CT findings for evaluation of complete and partial RFA are the ablated size and enhancement pattern of the ablated lesion.

Cutting and skin-ablative properties of pulsed mid-infrared laser surgery.

Science.gov (United States)

Kaufmann, R; Hartmann, A; Hibst, R

1994-02-01

Pulsed mid-infrared lasers allow a precise removal of soft tissues with only minimal thermal damage. To study the potential dermatosurgical usefulness of currently available systems at different wavelengths (2010-nm Thulium:YAG laser, 2100-nm Holmium:YAG laser, 2790-nm Erbium:YSGG laser, and 2940-nm Erbium:YAG laser) in vivo on pig skin. Immediate effects and wound healing of superficial laser-abrasions and incisions were compared with those of identical control lesions produced by dermabrasion, scalpel incisions, or laser surgery performed by a 1060-nm Nd:YAG and a 1060-nm CO2 laser (continuous and superpulsed mode). Best efficiency and least thermal injury was found for the pulsed Erbium:YAG laser, leading to ablative and incisional lesions comparable to those obtained by dermabrasion or superficial scalpel incisions, respectively. In contrast to other mid-infrared lasers tested, the 2940-nm Erbium:YAG laser thus provides a potential instrument for future applications in skin surgery, especially when aiming at a careful ablative removal of delicate superficial lesions with maximum sparing of adjacent tissue structures. However, in the purely incisional application mode pulsed mid-infrared lasers, though of potential usefulness in microsurgical indications (eg, surgery of the cornea), do not offer a suggestive alternative to simple scalpel surgery of the skin.

Quantitative characterization of agglomerate abrasion in a tumbling blender by using the Stokes number approach.

Science.gov (United States)

Willemsz, Tofan A; Nguyen, Tien Thanh; Hooijmaijers, Ricardo; Frijlink, Henderik W; Vromans, Herman; van der Voort Maarschalk, Kees

2013-03-01

Removal of microcrystalline cellulose agglomerates in a dry-mixing system (lactose, 100 M) predominantly occurs via abrasion. The agglomerate abrasion rate potential is estimated by the Stokes abrasion (StAbr) number of the system. The StAbr number equals the ratio between the kinetic energy density of the moving powder bed and the work of fracture of the agglomerate. Basically, the StAbr number concept describes the blending condition of the dry-mixing system. The concept has been applied to investigate the relevance of process parameters on agglomerate abrasion in tumbling blenders. Here, process parameters such as blender rotational speed and relative fill volumes were investigated. In this study, the StAbr approach revealed a transition point between abrasion rate behaviors. Below this transition point, a blending condition exists where agglomerate abrasion is dominated by the kinetic energy density of the powder blend. Above this transition point, a blending condition exists where agglomerates show (undesirable) slow abrasion rates. In this situation, the blending condition is mainly determined by the high fill volume of the filler.

Impact Capacity Reduction in Railway Prestressed Concrete Sleepers with Surface Abrasions

Science.gov (United States)

Ngamkhanong, Chayut; Li, Dan; Kaewunruen, Sakdirat

2017-10-01

Railway sleepers (also called ‘railroad tie’ in North America) embedded in ballasted railway tracks are a main part of railway track structures. Its important role is to transfer the loads evenly from the rails to a wider area of ballast bed and to secure rail gauge and enable safe passages of rolling stocks. By nature, railway infrastructure is nonlinear, evidenced by its behaviours, geometry and alignment, wheel-rail contact and operational parameters such as tractive efforts. Based on our critical review, the dynamic behaviour of railway sleepers has not been fully investigated, especially when the sleepers are deteriorated by excessive wears. In fact, the ballast angularity causes differential abrasions on the soffit or bottom surface of sleepers (especially at railseat zone). Furthermore, in sharp curves and rapid gradient change, longitudinal and lateral dynamics of rails increase the likelihood of railseat abrasions in concrete sleepers due to the unbalanced loading conditions. This paper presents a structural capacity of concrete sleepers under dynamic transient loading. The modified compression field theory for ultimate strength design of concrete sleepers under impact loading will be highlighted in this study. The influences of surface abrasions, including surface abrasion and soffit abrasion, on the dynamic behaviour of prestressed concrete sleepers, are firstly highlighted. The outcome of this study will improve the rail maintenance and inspection criteria in order to establish appropriate and sensible remote track condition monitoring network in practice. Moreover, this study will also improve the understanding of the fundamental dynamic behaviour of prestressed concrete sleepers with surface abrasions. The insight into these behaviours will not only improve safety and reliability of railway infrastructure but will enhance the structural safety of other concrete structures.

Study on isotopic distribution produced by nucleus-nucleus collisions with modified SAA model

International Nuclear Information System (INIS)

Zhong Chen; Fang Deqing; Cai Xiangzhou; Shen Wenqing; Zhang Huyong; Wei Yibin; Ma Yugang

2003-01-01

Base on Brohm's Statistic-Ablation-Abrasion (SAA) model, the modified SAA model was developed via introducing the isospin dependence of nucleon distribution in nucleus and parameterized formulas for nucleon-nucleon cross section in nuclear matter. It can simulate well the isotopic distribution at both high and intermediate energies. By the improvement of computational method, the range of calculation of isotopic distribution can be increased from three order magnitude to eight order magnitude (even higher). It can reproduce experimental data and predict the isotopic distribution for very far from stability line which is very important from experimental viewpoint

Refractory, Abrasive and Other Industrial Mineral Operations

Data.gov (United States)

Department of Homeland Security — This map layer includes refractory, abrasive, and other industrial minerals operations in the United States. The data represent commodities covered by the Minerals...

Thermal Ablation of the Pancreas With Intraoperative High-Intensity Focused Ultrasound: Safety and Efficacy in a Porcine Model.

Science.gov (United States)

Dupré, Aurélien; Melodelima, David; Pflieger, Hannah; Chen, Yao; Vincenot, Jérémy; Kocot, Anthony; Langonnet, Stéphan; Rivoire, Michel

2017-02-01

New focal destruction technologies such as high-intensity focused ultrasound (HIFU) may improve the prognosis of pancreatic ductal adenocarcinoma. Our objectives were to demonstrate the safety and efficacy of intraoperative pancreatic HIFU ablation in a porcine model. In a porcine model (N = 12), a single HIFU ablation was performed in either the body or tail of the pancreas, distant to superior mesenteric vessels. All animals were sacrificed on the eighth day. The primary objective was to obtain an HIFU ablation measuring at least 1 cm without premature death. In total, 12 HIFU ablations were carried out. These ablations were performed within 160 seconds and on average measured 20 (15-27) × 16 (8-26) mm. The primary objective was fulfilled in all but 1 pig. There were no premature deaths or severe complications. High-intensity focused ultrasound treatment was associated with a transitory increase in amylase and lipase levels, and pseudocysts were observed in half of the pigs without being clinically apparent. All ablations were well delimited at both gross and histological examinations. Intraoperative thermal destruction of porcine pancreas with HIFU is feasible. Reproducibility and safety have to be confirmed when applied close to mesenteric vessels and in long-term preclinical studies.

Transport properties site descriptive model. Guidelines for evaluation and modelling

International Nuclear Information System (INIS)

Berglund, Sten; Selroos, Jan-Olof

2004-04-01

This report describes a strategy for the development of Transport Properties Site Descriptive Models within the SKB Site Investigation programme. Similar reports have been produced for the other disciplines in the site descriptive modelling (Geology, Hydrogeology, Hydrogeochemistry, Rock mechanics, Thermal properties, and Surface ecosystems). These reports are intended to guide the site descriptive modelling, but also to provide the authorities with an overview of modelling work that will be performed. The site descriptive modelling of transport properties is presented in this report and in the associated 'Strategy for the use of laboratory methods in the site investigations programme for the transport properties of the rock', which describes laboratory measurements and data evaluations. Specifically, the objectives of the present report are to: Present a description that gives an overview of the strategy for developing Site Descriptive Models, and which sets the transport modelling into this general context. Provide a structure for developing Transport Properties Site Descriptive Models that facilitates efficient modelling and comparisons between different sites. Provide guidelines on specific modelling issues where methodological consistency is judged to be of special importance, or where there is no general consensus on the modelling approach. The objectives of the site descriptive modelling process and the resulting Transport Properties Site Descriptive Models are to: Provide transport parameters for Safety Assessment. Describe the geoscientific basis for the transport model, including the qualitative and quantitative data that are of importance for the assessment of uncertainties and confidence in the transport description, and for the understanding of the processes at the sites. Provide transport parameters for use within other discipline-specific programmes. Contribute to the integrated evaluation of the investigated sites. The site descriptive modelling of

Self-consistent model of the Rayleigh--Taylor instability in ablatively accelerated laser plasma

International Nuclear Information System (INIS)

Bychkov, V.V.; Golberg, S.M.; Liberman, M.A.

1994-01-01

A self-consistent approach to the problem of the growth rate of the Rayleigh--Taylor instability in laser accelerated targets is developed. The analytical solution of the problem is obtained by solving the complete system of the hydrodynamical equations which include both thermal conductivity and energy release due to absorption of the laser light. The developed theory provides a rigorous justification for the supplementary boundary condition in the limiting case of the discontinuity model. An analysis of the suppression of the Rayleigh--Taylor instability by the ablation flow is done and it is found that there is a good agreement between the obtained solution and the approximate formula σ = 0.9√gk - 3u 1 k, where g is the acceleration, u 1 is the ablation velocity. This paper discusses different regimes of the ablative stabilization and compares them with previous analytical and numerical works

A modeling of elementary passes taking into account the firing angle in abrasive water jet machining of titanium alloy

Science.gov (United States)

Bui, Van-Hung; Gilles, Patrick; Cohen, Guillaume; Rubio, Walter

2018-05-01

The use of titanium alloys in the aeronautical and high technology domains is widespread. The high strength and the low mass are two outstanding characteristics of titanium alloys which permit to produce parts for these domains. As other hard materials, it is challenging to generate 3D surfaces (e.g. pockets) when using conventional cutting methods. The development of Abrasive Water Jet Machining (AWJM) technology shows the capability to cut any kind of materials and it seems to be a good solution for such titanium materials with low specific force, low deformation of parts and low thermal shocks. Applying this technology for generating 3D surfaces requires to adopt a modelling approach. However, a general methodology results in complex models due to a lot of parameters of the machining process and based on numerous experiments. This study introduces an extended geometry model of an elementary pass when changing the firing angle during machining Ti-6AL-4V titanium alloy with a given machine configuration. Several experiments are conducted to observe the influence of major kinematic operating parameters, i.e. jet inclination angle (α) (perpendicular to the feed direction) and traverse speed (Vf). The material exposure time and the erosion capability of abrasives particles are affected directly by a variation of the traverse speed (Vf) and firing angle (α). These variations lead to different erosion rates along the kerf profile characterized by the depth and width of cut. A comparison demonstrated an efficiency of the proposed model for depth and width of elementary passes. Based on knowledge of the influence of both firing angle and traverse speed on the elementary pass shape, the proposed model allows to develop the simulation of AWJM process and paves a way for milling flat bottom pockets and 3D complex shapes.

Feasibility Study on Cutting HTPB Propellants with Abrasive Water Jet

Science.gov (United States)

Jiang, Dayong; Bai, Yun

2018-01-01

Abrasive water jet is used to carry out the experiment research on cutting HTPB propellants with three components, which will provide technical support for the engineering treatment of waste rocket motor. Based on the reliability theory and related scientific research results, the safety and efficiency of cutting sensitive HTPB propellants by abrasive water jet were experimentally studied. The results show that the safety reliability is not less than 99.52% at 90% confidence level, so the safety is adequately ensured. The cooling and anti-friction effect of high-speed water jet is the decisive factor to suppress the detonation of HTPB propellant. Compared with pure water jet, cutting efficiency was increased by 5% - 87%. The study shows that abrasive water jets meet the practical use for cutting HTPB propellants.

Quantitative characterization of agglomerate abrasion in a tumbling blender by using the Stokes number approach

NARCIS (Netherlands)

Willemsz, Tofan A.; Nguyen, Tien Thanh; Hooijmaijers, Ricardo; Frijlink, Henderik W.; Vromans, Herman; van der Voort Maarschalk, Kees

2013-01-01

Removal of microcrystalline cellulose agglomerates in a dry-mixing system (lactose, 100 M) predominantly occurs via abrasion. The agglomerate abrasion rate potential is estimated by the Stokes abrasion (StAbr) number of the system. The StAbrnumber equals the ratio between the kinetic energy density

An object model for beamline descriptions

International Nuclear Information System (INIS)

Hill, B.W.; Martono, H.; Gillespie, J.S.

1997-01-01

Translation of beamline model descriptions between different accelerator codes presents a unique challenge due to the different representations used for various elements and subsystems. These differences range from simple units conversions to more complex translations involving multiple beamline components. A representation of basic accelerator components is being developed in order to define a meta-structure from which beamline models, in different codes, can be described and to facilitate the translation of models between these codes. Sublines of basic components will be used to represent more complex beamline descriptions and bridge the gap between codes which may represent a beamline element as a single entity, and those which use multiple elements to describe the same physical device. A C++ object model for supporting this beamline description and a grammar for describing beamlines in terms of these components is being developed. The object model will support a common graphic user interface and translation filters for representing native beamline descriptions for a variety of accelerator codes. An overview of our work on the object model for beamline descriptions is presented here. copyright 1997 American Institute of Physics

A Zero Dimensional Time-Dependent Model of High-Pressure Ablative Capillary Discharge (Preprint)

National Research Council Canada - National Science Library

Pekker, Leonid

2008-01-01

... plasma core and the ablative capillary walls. The model includes the thermodynamics of partially ionized plasmas and non-ideal effects taking place in the high density plasma and assumes local thermodynamic equilibrium (LTE...

Modeling of Heat Transfer and Ablation of Refractory Material Due to Rocket Plume Impingement

Science.gov (United States)

Harris, Michael F.; Vu, Bruce T.

2012-01-01

CR Tech's Thermal Desktop-SINDA/FLUINT software was used in the thermal analysis of a flame deflector design for Launch Complex 39B at Kennedy Space Center, Florida. The analysis of the flame deflector takes into account heat transfer due to plume impingement from expected vehicles to be launched at KSC. The heat flux from the plume was computed using computational fluid dynamics provided by Ames Research Center in Moffet Field, California. The results from the CFD solutions were mapped onto a 3-D Thermal Desktop model of the flame deflector using the boundary condition mapping capabilities in Thermal Desktop. The ablation subroutine in SINDA/FLUINT was then used to model the ablation of the refractory material.

Modeling of the physico-chemical ablation of carbon-based composites

International Nuclear Information System (INIS)

Lachaud, J.

2006-12-01

Carbon-based composites are used in extreme conditions: Tokamaks, re-entry bodies, nozzle throats, plane brakes. Their walls undergo a surface recession, called ablation, mainly due to some gasification phenomena (oxidation or even sublimation). This work is a contribution to the improvement of the understanding of the near-wall material/environment interaction and to its modeling. Some original gasification experiments have been carried out, modeled, and quantitatively analyzed; a complex multi-scale behavior of the materials is observed through their average recession velocity and a surface roughness onset mainly caused by their heterogeneous anisotropic structure. In order to explain these observations, a multi-scale modeling strategy has been set up; it follows the characteristic scales of the composites: nano-scopic (carbon texture), microscopic (fiber, inter-fiber matrix), mesoscopic (yarn, inter-yarn matrix), and macroscopic (homogenized composite) scales. The proposed models notably integrate the local recession of the wall, the heterogeneous gasification reactions, and mass transfer. A numerical simulation tool, based on Monte-Carlo Random Walks with Simplified Marching Cubes for the front tracking, has been implemented, validated, and used to solve these models. Using some numerically validated hypotheses, an analytical solution has been obtained; it provides a comprehensive understanding of ablation phenomena. It provides the effective behavior of the composites from that of their microscopic components through two changes of scale. The results of these phenomenological models have been validated by comparison to the laboratory experiments and applied for the analysis of actual applications. Physics-based criterions are made available for the choice or the fabrication of ideal materials. (author)

Photochemical surface modification of PP for abrasion resistance

International Nuclear Information System (INIS)

Bahners, Thomas; Haessler, Ruediger; Gao Shanglin; Maeder, Edith; Wego, Andreas; Schollmeyer, Eckhard

2009-01-01

The potential of a photo-chemical approach to increase the surface hardness of polypropylene (PP) has been studied. Using a 222 nm excimer lamp, fibers and film were irradiated in the presence of multi-functional substances diallylphthalate (DAP), tetraallyloxyethane (TAE), and pentaerithritoltriacylate (PETA) and characterized with regard to the resulting effect on abrasion resistance. AFM-based methods were employed to analyze thermo-mechanical surface properties. Nanoindentation and microthermal analyses of the outermost surface layers of UV treated fibers gave clear indications of an effective cross-linking of reactive substances present during irradiation. One may assume that the reactive media polymerize on top of the surface of the PP substrate and form a thin-layer. The abrasion resistance of the PP fibers was tested by applying stress through a rotating and axially oscillating roller of defined roughness and measuring the mass loss as a function of time. The abrasion resistance was found to be remarkably improved compared to the untreated fiber. Best effects were achieved using PETA as reactive substance. The experiments clearly showed the influence of processing conditions, namely with regard to homogeneous coverage of the substrate surface with the reactive medium.

Experimental Study of the Ultrasonic Vibration-Assisted Abrasive Waterjet Micromachining the Quartz Glass

Directory of Open Access Journals (Sweden)

Rongguo Hou

2018-01-01

Full Text Available The ultrasonic vibration is used to enhance the capability of the abrasive water micromachining glass. And, the ultrasonic vibration is activated on the abrasive waterjet nozzle. The quality of the flow is improved, and the velocity of the abrasive is increased because of the addition of the ultrasonic energy. The relevant experimental results indicate that the erosion depth and the material volume removal of the glass are obviously increased when ultrasonic vibration is working. As for the influence of process parameters on the material removal of the glass such as vibration amplitude, system pressure, distance of the standoff, and abrasive size, the experimental results indicate that the system pressure and vibration contribute greatly to the glass material removal. Also, the erosion depth and the volume of material removal are increased with the increase in the vibration amplitude and system pressure. There are some uplifts found at the edge of erosion pit. Then, it can be inferred that the plastic method is an important material removal method during the machining process of ultrasonic vibration-assisted abrasive waterjet.

A new method to test rock abrasiveness based on physico-mechanical and structural properties of rocks

Directory of Open Access Journals (Sweden)

V.N. Oparin

2015-06-01

Full Text Available A new method to test rock abrasiveness is proposed based upon the dependence of rock abrasiveness on their structural and physico-mechanical properties. The article describes the procedure of presentation of properties that govern rock abrasiveness on a canonical scale by dimensionless components, and the integrated estimation of the properties by a generalized index. The obtained results are compared with the known classifications of rock abrasiveness.

Kinetic energy density and agglomerate abrasion rate during blending of agglomerates into powders.

Science.gov (United States)

Willemsz, Tofan A; Hooijmaijers, Ricardo; Rubingh, Carina M; Tran, Thanh N; Frijlink, Henderik W; Vromans, Herman; van der Voort Maarschalk, Kees

2012-01-23

Problems related to the blending of a cohesive powder with a free flowing bulk powder are frequently encountered in the pharmaceutical industry. The cohesive powder often forms lumps or agglomerates which are not dispersed during the mixing process and are therefore detrimental to blend uniformity. Achieving sufficient blend uniformity requires that the blending conditions are able to break up agglomerates, which is often an abrasion process. This study was based on the assumption that the abrasion rate of agglomerates determines the required blending time. It is shown that the kinetic energy density of the moving powder bed is a relevant parameter which correlates with the abrasion rate of agglomerates. However, aspects related to the strength of agglomerates should also be considered. For this reason the Stokes abrasion number (St(Abr)) has been defined. This parameter describes the ratio between the kinetic energy density of the moving powder bed and the work of fracture of the agglomerate. The St(Abr) number is shown to predict the abrasion potential of agglomerates in the dry-mixing process. It appeared possible to include effects of filler particle size and impeller rotational rate into this concept. A clear relationship between abrasion rate of agglomerates and the value of St(Abr) was demonstrated. Copyright © 2011 Elsevier B.V. All rights reserved.

Site descriptive modelling - strategy for integrated evaluation

International Nuclear Information System (INIS)

Andersson, Johan

2003-02-01

The current document establishes the strategy to be used for achieving sufficient integration between disciplines in producing Site Descriptive Models during the Site Investigation stage. The Site Descriptive Model should be a multidisciplinary interpretation of geology, rock mechanics, thermal properties, hydrogeology, hydrogeochemistry, transport properties and ecosystems using site investigation data from deep bore holes and from the surface as input. The modelling comprise the following iterative steps, evaluation of primary data, descriptive and quantitative modelling (in 3D), overall confidence evaluation. Data are first evaluated within each discipline and then the evaluations are checked between the disciplines. Three-dimensional modelling (i.e. estimating the distribution of parameter values in space and its uncertainty) is made in a sequence, where the geometrical framework is taken from the geological model and in turn used by the rock mechanics, thermal and hydrogeological modelling etc. The three-dimensional description should present the parameters with their spatial variability over a relevant and specified scale, with the uncertainty included in this description. Different alternative descriptions may be required. After the individual discipline modelling and uncertainty assessment a phase of overall confidence evaluation follows. Relevant parts of the different modelling teams assess the suggested uncertainties and evaluate the feedback. These discussions should assess overall confidence by, checking that all relevant data are used, checking that information in past model versions is considered, checking that the different kinds of uncertainty are addressed, checking if suggested alternatives make sense and if there is potential for additional alternatives, and by discussing, if appropriate, how additional measurements (i.e. more data) would affect confidence. The findings as well as the modelling results are to be documented in a Site Description

Ablation - breakthrough technology to reduce uranium mining cost and increase resources

International Nuclear Information System (INIS)

Scriven, D.

2014-01-01

Ablation Technologies, LLC has developed and patented a revolutionary mining technology termed “ablation”. Ablation is a process using only mechanical forces to upgrade sandstone uranium ores. Uranium bearing sandstone orebodies are formed from a uranium enriched solution flowing through an aquifer until it reached some type of a “red/ox” zone forcing the uranium and other heavy metals to come out of solution. The precipitate forms a thin coating on the sand grains and fills the interstitial space between the sand grains but does no penetrate the sand grains. The ablation process knocks the precipitate off the sand grains using the forces of abrasion, elastic compression and rebounding, much like a mud coated tennis ball will sheds the mud when bounced off the ground, and to some extent, sonic waves. This produces a product which collectively is exactly the same as the ore going in but with all the individual components separated. This allows for disgressionary separation, the most important of which is screening. The uranium and heavy metals report to the finer fractions of the material, typically less than 250 mesh. The larger fractions contain less than five percent of the uranium but 90 to 95 percent of the mass. The advantages of making an enriched ore are numerous: • Reduce haulage costs from 90 to 95 percent. • Reduce milling costs by reducing material handling costs, acid consumption and tailings disposal costs. • In addition to reducing overall mining and milling costs, the overall recovery of the recourse is increased because the ablation process is so inexpensive, if the material has to be mined it will be ablated and screened. This basically means ore control is significantly reduced, cutoff grade goes to practically zero and overall resource recovery is significantly increased. • Environmentally, the two major advantages are reduced tailings requirements at the mill site and cleaner waste dumps at the mine site. This paper will show

Performance Enhancement of Abrasive Waterjet Cutting

NARCIS (Netherlands)

2008-01-01

Abrasive Waterjet (AWJ) Machining is a recent non-traditional machining process. This technology is widely used in industry for cutting difficult-to-machine-materials, milling slots, polishing hard materials etc. AWJ machining has many advantages, e.g. it can cut net-shape parts, no heat is

Performance tests of an abrasive cut-off systems for the finishing of high-precision casts

Directory of Open Access Journals (Sweden)

A. Fedoryszyn

2008-10-01

Full Text Available The paper summarizes the performance data of a newly designed and engineered grinding and cut-off system. The machine is used forseparation of models manufactured by the investment casting method. The machine comprises the following units:- base supporting other assemblies and elements: abrasive disc holder and drives; this solution enables an easy replacement and access toholding elements while a belt transmission allows the disc rpm to be varied,- mechanism moving the spindle in the horizontal, hence the abrasive disc position with respect to the batch can be precisely controlled,depending on the cast position and their shape,- holding and positioning-control of the batch to enable the fore and aft movements and rotations,- guide systems ensuring the travel of the batch in the specified direction and adjusting the travel speed to the required cutting rate,- centering, control, exhaust system, housing.Extensive tests were performed, including the tests of operating parameters of abrasive discs depending on the cast material, cyclograms ofthe applied treatment are obtained accordingly.

Performance tests of an abrasive cut-off systems for the finishing of high-precision casts

Directory of Open Access Journals (Sweden)

A. Fedoryszyn

2008-07-01

Full Text Available The paper summarizes the performance data of a newly designed and engineered grinding and cut-off system. The machine is used for separation of models manufactured by the investment casting method. The machine comprises the following units:- base supporting other assemblies and elements: abrasive disc holder and drives; this solution enables an easy replacement and access to holding elements while a belt transmission allows the disc rpm to be varied,- mechanism moving the spindle in the horizontal, hence the abrasive disc position with respect to the batch can be precisely controlled, depending on the cast position and their shape,- holding and positioning-control of the batch to enable the fore and aft movements and rotations,- guide systems ensuring the travel of the batch in the specified direction and adjusting the travel speed to the required cutting rate,- centering, control, exhaust system, housingExtensive tests were performed, including the tests of operating parameters of abrasive discs depending on the cast material, cyclograms of the applied treatment are obtained accordingly.

Electrical resistivity measurements to predict abrasion resistance

Indian Academy of Sciences (India)

Home; Journals; Bulletin of Materials Science; Volume 31; Issue 2. Electrical resistivity measurements to predict abrasion resistance of rock aggregates ... It was seen that correlation coefficients were increased for the rock classes. In addition ...

Abrasion Wear Resistance, Hardness and Microstructure of Hard Linings Deposited by Means of a Submerged Arc. Dureza, microestructura y resistencia al desgaste por abrasion de recargues duros depositados con arco sumergido

Energy Technology Data Exchange (ETDEWEB)

Paranhos, R; Alcoforado, J M; Castillo, J A; Sauer, A

1989-01-01

Consumable materials for submerged arc welding of the types alloyed flux-neutral electrode and neutral flux-alloyed electrode were used to form, through multipass welding, a light alloy hard lining of the C-Mn type on ASTM A36 Type structural steel. Emphasis was put on microstructural characterization of the linings surveyed under electron scanning microscopy, and tests were performed to study their hardness and abrasion wear resistance at low pressures. As a result of these tests, a great influence of welding parameters on hardness and abrasion resistance properties of the combination active flux-neutral electrode was noticed. As the results showed no relationship between the hardness and the abrasion wear resistance of the linings surveyed, an attempt was made to relate the resulting microstructure with their abrasion wear resistance. (Author)

Characterization of Conventional and High-Translucency Y-TZP Dental Ceramics Submitted to Air Abrasion.

Science.gov (United States)

Tostes, Bhenya Ottoni; Guimarães, Renato Bastos; Noronha-Filho, Jaime Dutra; Botelho, Glauco Dos Santos; Guimarães, José Guilherme Antunes; Silva, Eduardo Moreira da

2017-01-01

This study evaluated the effect of air-abrasion on t®m phase transformation, roughness, topography and the elemental composition of three Y-TZP (Yttria-stabilized tetragonal zirconia polycrystal) dental ceramics: two conventional (Lava Frame and IPS ZirCad) and one with high-translucency (Lava Plus). Plates obtained from sintered blocks of each ceramic were divided into four groups: AS (as-sintered); 30 (air-abrasion with 30 mm Si-coated Al2O3 particles); 50 (air-abrasion with 50 mm Al2O3 particles) and 150 (air-abrasion with 150 mm Al2O3 particles). After the treatments, the plates were submitted to X-ray diffractometry; 3-D profilometry and SEM/EDS. The AS surfaces were composed of Zr and t phases. All treatments produced t®m phase transformation in the ceramics. The diameter of air-abrasion particles influenced the roughness (150>50>30>AS) and the topography. SEM analysis showed that the three treatments produced groove-shaped microretentions on the ceramic surfaces, which increased with the diameter of air-abrasion particles. EDS showed a decrease in Zr content along with the emergence of O and Al elements after air-abrasion. Presence of Si was also detected on the plates air-abraded with 30 mm Si-coated Al2O3 particles. It was concluded that irrespective of the type and diameter of the particles, air-abrasion produced t®m phase transformation, increased the roughness and changed the elemental composition of the three Y-TZP dental ceramics. Lava Plus also behaved similarly to the conventional Y-TZP ceramics, indicating that this high translucency ceramic could be more suitable to build monolithic ceramic restorations in the aesthetic restorative dentistry field.

Abrasive water jet: a complementary tool

Directory of Open Access Journals (Sweden)

Duarte, J. P.

1998-04-01

Full Text Available The abrasive water jet is a powerful cutting tool, whose main advantages lie in the absence of thermal effects and the capability of cutting highly thick materials. Compared with Laser, the abrasive water jet allows the cutting of a larger range of thicknesses and a wider variety of materials such as: ornamental stones, metals, polymers, composites, wood, glass and ceramics. The application of this technology has suffered an extensive growth, with successful applications in varied industrial sectors like the automotive, aerospace, textile, metalworking, ornamental stones, etc. The present communication aims at introducing the abrasive water jet as a complementary tool to laser cutting, presenting its advantages by showing some documented examples of pieces cut for different industries.

O jacto de água abrasivo é uma poderosa ferramenta de corte, tendo como principais vantagens a ausência de processo térmico e permitir o corte de elevadas espessuras. Comparativamente com o laser o jacto de água abrasivo permite cortar uma maior gama de espessuras, e uma maior diversidade de materiais: rochas ornamentais, metais, polimeros, compósitos, madeiras, vidro e cerâmicos. A aplicação desta tecnologia tem sofrido um crescimento acentuado, existindo aplicações de sucesso nos mais variados sectores industriáis como a indústria automóvel, aeroespacial, têxtil, metalomecânica e rochas ornamentáis. Esta comunição pretende apresentar o corte por jacto de agua abrasivo como uma ferramenta de corte complementar ao corte por laser, apresentando as suas vantagens documentadas através de alguns exemplos de peças executadas para as diferentes indústrias.

Lesion size in relation to ablation site during radiofrequency ablation

DEFF Research Database (Denmark)

Petersen, H H; Chen, X; Pietersen, A

1998-01-01

This study was designed to investigate the effect of the convective cooling of the tip of the ablation electrode during temperature controlled radiofrequency ablation. In vivo two different application sites in the left ventricle of anaesthetised pigs were ablated and in vitro ablation was perfor......This study was designed to investigate the effect of the convective cooling of the tip of the ablation electrode during temperature controlled radiofrequency ablation. In vivo two different application sites in the left ventricle of anaesthetised pigs were ablated and in vitro ablation...... was performed during two different flow-velocities in a tissue bath, while electrode contact pressure and position were unchanged. Target temperature was 80 degrees C. Obtained tip temperature, power consumption and lesion dimensions were measured. In vivo lesion volume, depth and width were found significantly.......61 in vitro). We conclude that during temperature controlled radiofrequency ablation lesion size differs for septal and apical left ventricular applications. Differences in convective cooling might play an important role in this respect. This is supported by our in vitro experiments, where increased...

Cardiac ablation

Directory of Open Access Journals (Sweden)

Kelly Ratheal

2016-01-01

Full Text Available Cardiac ablation is a procedure that uses either radiofrequency or cryothermal energy to destroy cells in the heart to terminate and/or prevent arrhythmias. The indications for cardiac catheter ablation include refractory, symptomatic arrhythmias, with more specific guidelines for atrial fibrillation in particular. The ablation procedure itself involves mapping the arrhythmia and destruction of the aberrant pathway in an effort to permanently prevent the arrhythmia. There are many types of arrhythmias, and they require individualized approaches to ablation based on their innately different electrical pathways. Ablation of arrhythmias, such as Wolff-Parkinson-White syndrome, AV nodal reentrant tachycardia, and atrial-fibrillation, is discussed in this review. Ablation has a high success rate overall and minimal complication rates, leading to improved quality of life in many patients.

Effect of Radiofrequency Endometrial Ablation on Dysmenorrhea.

Science.gov (United States)

Wyatt, Sabrina N; Banahan, Taylor; Tang, Ying; Nadendla, Kavita; Szychowski, Jeff M; Jenkins, Todd R

To examine rates of dysmenorrhea after radiofrequency endometrial ablation in patients with and without known dysmenorrhea symptoms prior to the procedure in a diverse population. Retrospective cohort study (Canadian Task Force classification II-2). Academic gynecology practice. A total of 307 women underwent endometrial ablation between 2007 and 2013 at our institution. Patients who had preoperative and postoperative pain symptom assessments as well as a description of pain timing recorded were included in our analysis. Exclusion criteria were age dysmenorrhea was evaluated. Demographic information and other outcome variables were used to evaluate factors associated with resolution of dysmenorrhea. A total of 307 patients who underwent radiofrequency endometrial ablation were identified. After exclusions, 296 charts were examined, and 144 patients met our enrollment criteria. The mean age of the study cohort was 45.4 ± 6.2 years; 57 patients (40%) were African American, 16 (11%) had a body mass index (BMI) > 40, and 41 (29%) were of normal weight. Preoperative dysmenorrhea was reported by 100 patients (69%); 48 of these patients (48%) experienced resolution of symptoms postoperatively. Only 3 of the 44 patients (7%) without preoperative dysmenorrhea reported new-onset dysmenorrhea postoperatively. Significantly fewer patients had dysmenorrhea after compared to before radiofrequency ablation (55 of 144 [38%] vs 100 of 144 [69%]; p dysmenorrhea after ablation was associated with reduction in bleeding volume (p = .048) but not with a reduction in frequency of bleeding (p = .12). Approximately one-half of women who undergo radiofrequency endometrial ablation to treat heavy menstrual bleeding who also have preoperative dysmenorrhea exhibit documented pain resolution after the procedure. Resolution of dysmenorrhea is more likely if menstrual flow volume is decreased postprocedure. Copyright © 2016 AAGL. Published by Elsevier Inc. All rights reserved.

Revised neutral gas shielding model for pellet ablation - combined neutral and plasma shielding

International Nuclear Information System (INIS)

Houlberg, W.A.; Schuresko, D.D.; Attenberger, S.E.

1986-01-01

The ablation and penetration of pellets in early ORMAK and ISX-A experiments were reliably predicted by the neutral gas shielding model of Milora and Foster. These experiments demonstrated that the principle components of the model - a self-generated shield which reduces the heat flux at the plasma surface - were correct. In more recent experiments with higher temperature plasmas, this model consistently predicts greater penetration than observed in the experiments. Upgarding known limitations of the original model brings the predicted and observed penetration values into agreement. These improvements include: (1) treating the incident electrons as having distribution in energy rather than being monoenergetic; (2) including the shielding effects of cold, dense plasma extending along the magnetic field outside the neutral shield; and (3) modifying the finite plasma, self-limiting incident heat flux so that it represents a collisionless plasma limit rather than a collisional limit. Comparisons are made between the models for a selection of ISX-B Alcator-C, and TFTR shots. The net effect of the changes in the model is an increase in pellet ablation rates and decrease in penetration for current and future experiments

Release of carbon nanotubes from an epoxy-based nanocomposite during an abrasion process.

Science.gov (United States)

Schlagenhauf, Lukas; Chu, Bryan T T; Buha, Jelena; Nüesch, Frank; Wang, Jing

2012-07-03

The abrasion behavior of an epoxy/carbon nanotube (CNT) nanocomposite was investigated. An experimental setup has been established to perform abrasion, particle measurement, and collection all in one. The abraded particles were characterized by particle size distribution and by electron microscopy. The abrasion process was carried out with a Taber Abraser, and the released particles were collected by a tube for further investigation. The particle size distributions were measured with a scanning mobility particle sizer (SMPS) and an aerodynamic particle sizer (APS) and revealed four size modes for all measured samples. The mode corresponding to the smallest particle sizes of 300-400 nm was measured with the SMPS and showed a trend of increasing size with increasing nanofiller content. The three measured modes with particle sizes from 0.6 to 2.5 μm, measured with the APS, were similar for all samples. The measured particle concentrations were between 8000 and 20,000 particles/cm(3) for measurements with the SMPS and between 1000 and 3000 particles/cm(3) for measurements with the APS. Imaging by transmission electron microscopy (TEM) revealed that free-standing individual CNTs and agglomerates were emitted during abrasion.

Erosion wear of boron carbide ceramic nozzles by abrasive air-jets

International Nuclear Information System (INIS)

Deng Jianxin

2005-01-01

Boron carbide nozzles were produced by hot pressing. The erosion wear of this nozzle caused by abrasive particle impact was investigated by abrasive air-jets. Silica, silicon carbide and alumina powders with different hardness were used as the erodent abrasive particles. Results showed that the hardness of the erodent particles played an important role with respect to the erosion wear of the boron carbide nozzles. As the hardness of the erodent particles increases, there is a dramatic increase in erosion rate of the nozzles. The nozzle entrance area suffered from severe abrasive impact under large impact angles, and generated maximum tensile stresses. The wear mechanisms of boron carbide nozzle at this area appeared to be entirely brittle in nature with the evidence of large scale-chipping, and exhibited a brittle fracture induced removal process. While at the nozzle center wall section, most of the particles traveled parallel to the nozzle wall, and showed minimum tensile stresses. The wear mode in this area of the nozzle changed from impact to sliding erosion, and the wear mechanisms appeared to be the lateral cracking owing to a surface fatigue fracture mechanism

Effect of dried sunflower seeds on incisal edge abrasion: A rare case report.

Science.gov (United States)

Rath, Avita; Ramamurthy, Priyadarshini H; Fernandes, Bennete Aloysius; Sidhu, Preena

2017-01-01

Tooth surface loss (TSL) is a complex phenomenon characterized by the loss of hard tooth structure at various locations of the teeth, usually due to more than one factor. TSL due to abrasion can be significant in patients consuming coarse, abrasive diet. The present case reports an interesting incisal edge abrasion in a female patient, attributed to a particular dietary behavior of long-term consumption of sunflower seeds. All her family members and most of the people from her native place were also reported to have similar lesions by the patient. Larger epidemiological studies to assess the prevalence and severity of such abrasive lesions in geographic areas with this particular dietary habit need to be carried out so that people may be made aware and educated about alternative ways of eating sunflower seeds that will not cause any form of tooth wear.

Hydrogen pellet ablation and accelerator by current in high temperature plasmas

International Nuclear Information System (INIS)

Kuteev, B.V.

1995-01-01

Hydrogen pellet ablation and acceleration by current in high temperature plasmas are analyzed. The present state of ablation theory and experiment is discussed and an ablation model is formulated. This model takes into account the energy distribution of the particles (both electrons and ions) participating in the ablation process, electrostatic effects of the cloud charging and changes of the pellet form during ablation. Without charging the pellet form tends to a shape resembling a lentil while it remains almost spherical if charged. A new algorithm for ablation rate calculations that can be used for an arbitrary initial form of the pellet is described. The results of this kinetic two dimensional approach differ from those of the Parks ablation scaling used in the ITER design by not more than 30%. Plasma shielding effects are not significant in the ablation if strong turbulence in the cloud is taken into account. Acceleration analysis is based on the Braginskii corrected electron distribution function. For the lentil mode of ablation, acceleration is higher than those for the charged mode by a factor of 1.76. The ablation models are compared with the experiments on T-10, JET, TFTR, Heliotron-E and Tore Supra. A sensitivity analysis shows that pellet size and electron temperature are the most significant factors for determination of the penetration length. The available database of penetration lengths is not sufficient for distinguishing between the models. Acceleration for the charged model correlates with experimental data better than that for the lentil mode. The effect of the hot ions is seen on the ablation. Finally, ablation at reactor relevant plasma and pellet parameters is considered. This range of the plasma parameters needs a correction of the ablation scaling as follows: dN/dt ∼ n 0.453 e T 1.72 e r 1.443 p M -0.283 i , where n e and T e are the electron density and temperature, respectively, and r p and M i are the pellet radius and atomic mass

29 CFR 1915.134 - Abrasive wheels.

Science.gov (United States)

2010-07-01

... 29 Labor 7 2010-07-01 2010-07-01 false Abrasive wheels. 1915.134 Section 1915.134 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR... wheels shall fit freely on the spindle and shall not be forced on. The spindle nut shall be tightened...

Review of Artificial Abrasion Test Methods for PV Module Technology

Energy Technology Data Exchange (ETDEWEB)

Miller, David C. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Muller, Matt T. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Simpson, Lin J. [National Renewable Energy Lab. (NREL), Golden, CO (United States)

2016-08-01

This review is intended to identify the method or methods--and the basic details of those methods--that might be used to develop an artificial abrasion test. Methods used in the PV literature were compared with their closest implementation in existing standards. Also, meetings of the International PV Quality Assurance Task Force Task Group 12-3 (TG12-3, which is concerned with coated glass) were used to identify established test methods. Feedback from the group, which included many of the authors from the PV literature, included insights not explored within the literature itself. The combined experience and examples from the literature are intended to provide an assessment of the present industry practices and an informed path forward. Recommendations toward artificial abrasion test methods are then identified based on the experiences in the literature and feedback from the PV community. The review here is strictly focused on abrasion. Assessment methods, including optical performance (e.g., transmittance or reflectance), surface energy, and verification of chemical composition were not examined. Methods of artificially soiling PV modules or other specimens were not examined. The weathering of artificial or naturally soiled specimens (which may ultimately include combined temperature and humidity, thermal cycling and ultraviolet light) were also not examined. A sense of the purpose or application of an abrasion test method within the PV industry should, however, be evident from the literature.

Robotically Assisted Sonic Therapy as a Noninvasive Nonthermal Ablation Modality: Proof of Concept in a Porcine Liver Model.

Science.gov (United States)

Smolock, Amanda R; Cristescu, Mircea M; Vlaisavljevich, Eli; Gendron-Fitzpatrick, Annette; Green, Chelsey; Cannata, Jonathan; Ziemlewicz, Timothy J; Lee, Fred T

2018-05-01

Purpose To determine the feasibility of creating a clinically relevant hepatic ablation (ie, an ablation zone capable of treating a 2-cm liver tumor) by using robotically assisted sonic therapy (RAST), a noninvasive and nonthermal focused ultrasound therapy based on histotripsy. Materials and Methods This study was approved by the institutional animal use and care committee. Ten female pigs were treated with RAST in a single session with a prescribed 3-cm spherical treatment region and immediately underwent abdominal magnetic resonance (MR) imaging. Three pigs (acute group) were sacrificed immediately following MR imaging. Seven pigs (chronic group) were survived for approximately 4 weeks and were reimaged with MR imaging immediately before sacrifice. Animals underwent necropsy and harvesting of the liver for histologic evaluation of the ablation zone. RAST ablations were performed with a 700-kHz therapy transducer. Student t tests were performed to compare prescribed versus achieved ablation diameter, difference of sphericity from 1, and change in ablation zone volume from acute to chronic imaging. Results Ablation zones had a sphericity index of 0.99 ± 0.01 (standard deviation) (P < .001 vs sphericity index of 1). Anteroposterior and transverse dimensions were not significantly different from prescribed (3.4 ± 0.7; P = .08 and 3.2 ± 0.8; P = .29, respectively). The craniocaudal dimension was significantly larger than prescribed (3.8 ± 1.1; P = .04), likely because of respiratory motion. The central ablation zone demonstrated complete cell destruction and a zone of partial necrosis. A fibrous capsule surrounded the ablation zone by 4 weeks. On 4-week follow-up images, ablation zone volumes decreased by 64% (P < .001). Conclusion RAST is capable of producing clinically relevant ablation zones in a noninvasive manner in a porcine model. © RSNA, 2018.

Study on Abrasive Wear of Brake Pad in the Large-megawatt Wind Turbine Brake Based on Deform Software

Science.gov (United States)

Zhang, Shengfang; Hao, Qiang; Sha, Zhihua; Yin, Jian; Ma, Fujian; Liu, Yu

2017-12-01

For the friction and wear issues of brake pads in the large-megawatt wind turbine brake during braking, this paper established the micro finite element model of abrasive wear by using Deform-2D software. Based on abrasive wear theory and considered the variation of the velocity and load in the micro friction and wear process, the Archard wear calculation model is developed. The influence rules of relative sliding velocity and friction coefficient in the brake pad and disc is analysed. The simulation results showed that as the relative sliding velocity increases, the wear will be more serious, while the larger friction coefficient lowered the contact pressure which released the wear of the brake pad.

Liquid abrasive pressure pot scoping tests report

International Nuclear Information System (INIS)

Archibald, K.E.

1996-01-01

The primary initiatives of the LITCO Decontamination Development group at the Idaho Chemical Process Plant (ICPP) are the development of methods to eliminate the use of sodium bearing decontamination chemicals and minimization of the amount of secondary waste generated during decontamination activities. In July of 1994, a Commerce Business Daily (CBD) announcement was issued by the INEL to determine commercial interest in the development of an in-situ liquid abrasive grit blasting system. As a result of the CBD announcement, Klieber ampersand Schulz issued an Expression of Interest letter which stated they would be interested in testing a prototype Liquid Abrasive Pressure Pot (LAPP). LITCO's Decontamination group and Kleiber ampersand Schulz entered into a Cooperative Research and Development Agreement (CRADA) in which the Decontamination Development group tested the prototype LAPP in a non-radioactive hot cell mockup. Test results are provided

Therapeutic efficacy of percutaneous radiofrequency ablation versus microwave ablation for hepatocellular carcinoma.

Directory of Open Access Journals (Sweden)

Lei Zhang

Full Text Available The aim of this study was to investigate the therapeutic efficacy of percutaneous radiofrequency (RF ablation versus microwave (MW ablation for hepatocellular carcinoma (HCC measuring ≤ 5 cm in greatest diameter. From January 2006 to December 2006, 78 patients had undergone RF ablation whereas 77 had undergone MW ablation. Complete ablation (CA, local tumour progression (LTP and distant recurrence (DR were compared. The overall survival curves were calculated with the Kaplan-Meier technique and compared with the log-rank test. The CA rate was 83.4% (78/93 for RF ablation and 86.7%(91/105 for MW ablation. The LTP rate was 11.8% (11/93 for RF ablation and 10.5% (11/105 for MW ablation. DR was found in 51 (65.4% in the RF ablation and 62 (80.5% in the MW ablation. There was no significant difference in the 1-, 3-, and 5-year overall survival rates (P = 0.780 and the 1-, 3-, and 5-year disease-free survival rates (P = 0.123 between RF and MW ablation. At subgroup analyses, for patients with tumors ≤ 3.0 cm, there was no significant difference in the 1-, 3-, and 5-year overall survival rates (P = 0.067 and the corresponding disease-free survival rates(P = 0.849. For patients with tumor diameters of 3.1-5.0 cm, the 1-, 3-, and 5-year overall survival rates were 87.1%, 61.3%, and 40.1% for RF ablation and 85.4%, 36.6%, and 22% for MW ablation, with no significant difference (P = 0.068. The corresponding disease-free survival rates were 74.2%, 54.8%, and 45.2% for the RF ablation group and 53.3%, 26.8%, and 17.1% for the MW ablation group. The disease-free survival curve for the RF ablation group was significantly better than that for the MW ablation group (P = 0.018. RF ablation and MW ablation are both effective methods in treating hepatocellular carcinomas, with no significant differences in CA, LTP, DR, and overall survival.

Micrometeoroid ablation simulated in the laboratory

Science.gov (United States)

Sternovsky, Zoltan; Thomas, Evan W.; DeLuca, Michael; Horanyi, Mihaly; Janches, Diego; Munsat, Tobin L.; Plane, John M. C.

2016-04-01

A facility is developed to simulate the ablation of micrometeoroids in laboratory conditions, which also allows measuring the ionization probability of the ablated material. An electrostatic dust accelerator is used to generate iron and meteoric analog particles with velocities 10-50 km/s. The particles are then introduced into a cell filled with nitrogen, air or carbon dioxide gas with pressures adjustable in the 0.02 - 0.5 Torr range, where the partial or complete ablation of the particle occurs over a short distance. An array of biased electrodes is used to collect the ionized products with spatial resolution along the ablating particles' path, allowing thus the study of the temporal resolution of the process. A simple ablation model is used to match the observations. For completely ablated particles the total collected charge directly yields the ionization efficiency for. The measurements using iron particles in N2 and air are in relatively good agreement with earlier data. The measurements with CO2 and He gases, however, are significantly different from the expectations.

Abrasion Resistance of as-Cast High-Chromium Cast Iron

Directory of Open Access Journals (Sweden)

Pokusová Marcela

2014-12-01

Full Text Available High chromium cast irons are widely used as abrasion resistant materials. Their properties and wear resistance depend on carbides and on the nature of the matrix supporting these carbides. The paper presents test results of irons which contain (in wt.% 18-22 Cr and 2-5 C, and is alloyed by 1.7 Mo + 5 Ni + 2 Mn to improve the toughness. Tests showed as-cast irons with mostly austenitic matrix achieved hardness 36-53 HRC but their relative abrasion-resistance was higher than the tool steel STN 19436 heat treated on hardness 60 HRC.

Research on operation mode of abrasive grain during grinding

Science.gov (United States)

Ivanova, T. N.; Dement’ev, V. B.; Nikitina, O. V.

2018-03-01

The processing of materials by cutting with an abrasive tool is carried out by means of thousands of grains bonded together as a single whole. The quality of the abrasive tool is defined by cutting properties of abrasive grains and depends on features of spreading the temperature field in time and in the abrasive grain volume. Grains are exposed to heating and cooling during work. It leads to undesired effects such as a decrease of durability of grain retention in the binder, hardness, intensification of diffusion and oxidation processes between the binder and the grain, the occurrence of considerable temperature stresses in the grain itself. The obtained equation which allows calculation of temperature field of grain for one rotation of grinding wheel shows that the temperature of the wheel depends on grinding modes and thermophysical properties of abrasive material. Thus, as the time of contact of grain with processed material increases, the temperature in the cutting area rises. As thermophysical properties increase, the temperature in cutting area decreases. Thermal working conditions are determined to be different from each other depending on contact time of the grain and the material. For example, in case of creep-feed grinding, the peak value of temperature is higher than during multistep grinding; the depth of expansion is greater. While the speed of the thermal process in creep-feed grinding is 2-3 times lower than in multistep grinding, the gradient reduces 3-4 times. The analysis of machining methods shows that creep-feed grinding ensures greater depth of grain heating, a smaller heating rate and a reduced velocity gradient. It causes a decrease of probable allotropic modifications and prevents from occurring of heat strokes - cracking of grains due to high temperature falls. Consequently, it is necessary to employ creep-feed grinding to increase the efficiency of abrasive tool employing. Three operation modes of grinding wheel including blunting, full

Percutaneous Irreversible Electroporation Lung Ablation: Preliminary Results in a Porcine Model

International Nuclear Information System (INIS)

Deodhar, Ajita; Monette, Sébastien; Single, Gordon W.; Hamilton, William C.; Thornton, Raymond H.; Sofocleous, Constantinos T.; Maybody, Majid; Solomon, Stephen B.

2011-01-01

Objective: Irreversible electroporation (IRE) uses direct electrical pulses to create permanent “pores” in cell membranes to cause cell death. In contrast to conventional modalities, IRE has a nonthermal mechanism of action. Our objective was to study the histopathological and imaging features of IRE in normal swine lung. Materials and Methods: Eleven female swine were studied for hyperacute (8 h), acute (24 h), subacute (96 h), and chronic (3 week) effects of IRE ablation in lung. Paired unipolar IRE applicators were placed under computed tomography (CT) guidance. Some applicators were deliberately positioned near bronchovascular structures. IRE pulse delivery was synchronized with the cardiac rhythm only when ablation was performed within 2 cm of the heart. Contrast-enhanced CT scan was performed immediately before and after IRE and at 1 and 3 weeks after IRE ablation. Representative tissue was stained with hematoxylin and eosin for histopathology. Results: Twenty-five ablations were created: ten hyperacute, four acute, and three subacute ablations showed alveolar edema and necrosis with necrosis of bronchial, bronchiolar, and vascular epithelium. Bronchovascular architecture was maintained. Chronic ablations showed bronchiolitis obliterans and alveolar interstitial fibrosis. Immediate post-procedure CT images showed linear or patchy density along the applicator tract. At 1 week, there was consolidation that resolved partially or completely by 3 weeks. Pneumothorax requiring chest tube developed in two animals; no significant cardiac arrhythmias were noted. Conclusion: Our preliminary porcine study demonstrates the nonthermal and extracellular matrix sparing mechanism of action of IRE. IRE is a potential alternative to thermal ablative modalities.

Prepolishing on a CNC platform with bound abrasive contour tools

Science.gov (United States)

Schoeffler, Adrienne E.; Gregg, Leslie L.; Schoen, John M.; Fess, Edward M.; Hakiel, Michael; Jacobs, Stephen D.

2003-05-01

Deterministic microgrinding (DMG) of optical glasses and ceramics is the commercial manufacturing process of choice to shape glass surfaces prior to final finishing. This process employs rigid bound matrix diamond tooling resulting in surface roughness values of 3-5μm peak to valley and 100-400nm rms, as well as mid-spatial frequency tool marks that require subsequent removal in secondary finishing steps. The ability to pre-polish optical surfaces within the grinding platform would reduce final finishing process times. Bound abrasive contour wheels containing cerium oxide, alumina or zirconia abrasives were constructed with an epoxy matrix. The effects of abrasive type, composition, and erosion promoters were examined for tool hardness (Shore D), and tested with commercial optical glasses in an Optipro CNC grinding platform. Metrology protocols were developed to examine tool wear and subsequent surface roughness. Work is directed to demonstrating effective material removal, improved surface roughness and cutter mark removal.

Development of abrasion resistant glass-ceramics from industrial waste products. Final report

Energy Technology Data Exchange (ETDEWEB)

von Roode, M.

1983-05-26

Slag-ceramics were produced from glass compositions using pelletized slag as the major ingredient. The abrasion resistance, fracture toughness and microstructure of the prepared glass and glass-ceramics were evaluated. Glas-ceramics with good abrasion resistance were obtained when iron oxide in conjunction with carbon was used as a nucleating agent. 5 figs., 11 tabs.

Characterization of abrasion-induced nanoparticle release from paints into liquids and air

Science.gov (United States)

Golanski, L.; Gaborieau, A.; Guiot, A.; Uzu, G.; Chatenet, J.; Tardif, F.

2011-07-01

Two standard methods for the characterization of the abrasion nanoparticle release into air and liquid from coatings containing nanoparticles were developed. Details of the abrasion processes and the measurement methods are shown. Paints were formulated in an industrial facility. Standard abrasion conditions in wet environments were simulated. The size distribution of the particles abraded into liquid was analyzed by a laser granulometer: submicrometric and micrometric particles were observed, but no nanometric particles. The nanoparticles released in liquid were deposited on filters for SEM (Scanning Electron Microscopy) analysis. No free or agglomerated nanoparticles were observed by SEM: nanoparticles seem to remain embedded in the paint matrix. The same coatings were abraded in the air using another standard method. The ELPI (Electrical Low Pressure Impactor) was used to determine the number size distribution of the dust generated. Abrasion is found to produce submicrometric and micrometric particles in the air but no nanoparticles. Further characterizations by SEM confirmed that no free or agglomerated nanoparticles were emitted: nanoparticles seem to remain embedded in the paint matrix.

Characterization of abrasion-induced nanoparticle release from paints into liquids and air

International Nuclear Information System (INIS)

Golanski, L; Guiot, A; Uzu, G; Tardif, F; Gaborieau, A; Chatenet, J

2011-01-01

Two standard methods for the characterization of the abrasion nanoparticle release into air and liquid from coatings containing nanoparticles were developed. Details of the abrasion processes and the measurement methods are shown. Paints were formulated in an industrial facility. Standard abrasion conditions in wet environments were simulated. The size distribution of the particles abraded into liquid was analyzed by a laser granulometer: submicrometric and micrometric particles were observed, but no nanometric particles. The nanoparticles released in liquid were deposited on filters for SEM (Scanning Electron Microscopy) analysis. No free or agglomerated nanoparticles were observed by SEM: nanoparticles seem to remain embedded in the paint matrix. The same coatings were abraded in the air using another standard method. The ELPI (Electrical Low Pressure Impactor) was used to determine the number size distribution of the dust generated. Abrasion is found to produce submicrometric and micrometric particles in the air but no nanoparticles. Further characterizations by SEM confirmed that no free or agglomerated nanoparticles were emitted: nanoparticles seem to remain embedded in the paint matrix.

Development of a novel bioactive glass for air-abrasion to selectively remove orthodontic adhesives.

Science.gov (United States)

Taha, Ayam A; Hill, Robert G; Fleming, Padhraig S; Patel, Mangala P

2018-05-01

To develop a novel, bioactive glass for removing residual orthodontic adhesive via air-abrasion, following bracket debonding, and to evaluate its effectiveness against a proprietary bioactive glass 45S5(Sylc™)-air-abrasion, and a slow-speed tungsten carbide (TC) bur. Three glasses were prepared and their bioactivity was proved. One novel glass (QMAT3) was selected due to its appropriate hardness, lower than that of enamel/45S5(Sylc™). Sixty extracted human premolars were randomly assigned to adhesive removal using: (a) QMAT3-air-abrasion, (b) 45S5(Sylc™)-air-abrasion, and (c) TC bur, which were further subdivided (n = 10) based on the adhesive used (Transbond XT™ or Fuji Ortho LC™). Enamel roughness was assessed using scanning electron microscopy (SEM) and non-contact profilometry before bracket bonding, after removing residual adhesive following bracket debonding and after polishing. QMAT3 formed apatite faster (6 h) than 45S5(Sylc™) (24 h) in Tris solution. QMAT3-air-abrasion gave the lowest enamel roughness (Ra) after removing the adhesives. SEM images showed a pitted, roughened enamel surface in the TC bur group and to a lesser extent with 45S5(Sylc™), while a virtually smooth surface without any damage was observed in the QMAT3-air-abrasion group. The time taken for adhesive removal with QMAT3 was comparable to 45S5(Sylc™) but was twice as long with the TC bur. QMAT3-air-abrasion is a promising technique for selective removal of adhesives without inducing tangible enamel damage. A novel bioactive glass has been developed as an alternative to the use of TC burs for orthodontic adhesive removal.

Pellet-plasma interaction: Local disturbances caused by pellet ablation in tokamaks

International Nuclear Information System (INIS)

Lengyel, L.L.

1989-01-01

The local disturbance amplitudes caused by ablating pellets in tokamaks are computed in the framework of a magnetohydrodynamic model supplemented by the neutral gas plasma shielding ablation model. The model computes, for a given number of pellet particles locally deposited, the time histories of the ablatant cloud parameters, such as cloud radius, cloud length, electron density, temperature and cloud beta, at a succession of magnetic flux surfaces. The cloud radius thus determined may be fed back into the ablation model, thus adjusting the effect of the shielding cloud on the ablation rate. The model is applied to typical plasma parameter ranges of existing and planned tokamaks. The results show that the ablating pellets may cause massive local disturbances in tokamaks, depending upon the number of particles locally deposited. The peaks of these disturbances are of a spike nature, lasting only a few microseconds (Alfven time-scale). The characteristic decay time of the 'quasi-steady' disturbance values that characterize the after-spike period is of the order of several milliseconds (hydrodynamic time-scale). The peak electron density values may be as high as 10 23 to 10 25 m -3 , with the associated beta peaks exceeding unity. The 'quasi-steady' values of the electron density and the ablatant beta may be of the order of 10 22 to 10 24 m -3 and unity, respectively. Furthermore, the results show the strong dependence of the ablation rate on the dynamic characteristics of the ablatant cloud surrounding the pellet. (author). 25 refs, 6 figs, 2 tabs

Radiofrequency thermal ablation of malignant hepatic tumors: post-ablation syndrome

International Nuclear Information System (INIS)

Choi, Jung Bin; Rhim, Hyunchul; Kim, Yongsoo; Koh, Byung Hee; Cho, On Koo; Seo, Heung Suk; Lee, Seung Ro

2000-01-01

To evaluate post-ablation syndrome after radiofrequency thermal ablation of malignant hepatic tumors. Forty-two patients with primary (n=3D29) or secondary (n=3D13) hepatic tumors underwent radiofrequency thermal ablation. A total of 65 nodules ranging in size from 1.1 to 5.0 (mean, 3.1) cm were treated percutaneously using a 50W RF generator with 15G expandable needle electrodes. We retrospectively evaluated the spectrum of post-ablation syndrome including pain, fever (≥3D 38 deg C), nausea, vomiting, right shoulder pain, and chest discomfort according to frequency, intensity and duration, and the findings were correlated with tumor location and number of ablations. We also evaluated changes in pre-/post-ablation serum aminotransferase (ALT/AST) and prothrombin time, and correlated these findings with the number of ablations. Post-ablation syndrome was noted in 29 of 42 patients (69.0%), and most symptoms improved with conservative treatment. The most important of these were abdominal plan (n=3D20, 47.6%), fever (n=3D8, 19.0%), and nausea (n=3D7, 16.7%), and four of 42 (9.5%) patients complained of severe pain. The abdominal pain lasted from 3 hours to 5.5 days (mean; 20.4 hours), the fever from 6 hours to 5 days (mean; 63.0 hours). And the nausea from 1 hours to 4 days (mean; 21.0 hours). Other symptoms were right shoulder pain (n=3D6, 14.3%), chest discomfort (n=3D3, 7.1%), and headache (n=3D3, 7.1%). Seventeen of 20 patients (85%) with abdominal pain had subcapsular tumor of the liver. There was significant correlation between pain, location of the tumor, and a number of ablations. After ablation, ALT/AST was elevated more than two-fold in 52.6%/73.7% of patients, respectively but there was no significant correlation with the number of ablation. Post-ablation syndrome is a frequent and tolerable post-procedural process after radiofrequency thermal ablation. The spectrum of this syndrome provides a useful guideline for the post-ablation management. (author)

Abrasion Testing of Critical Components of Hydrokinetic Devices

Energy Technology Data Exchange (ETDEWEB)

Worthington, Monty [ORPC Alaska; Ali, Muhammad [Ohio University; Ravens, Tom [University of Alaska Anchorage

2013-12-06

The objective of the Abrasion Testing of Critical Components of Hydrokinetic Devices (Project) was to test critical components of hydrokinetic devices in waters with high levels of suspended sediment – information that is widely applicable to the hydrokinetic industry. Tidal and river sites in Alaska typically have high suspended sediment concentrations. High suspended sediment also occurs in major rivers and estuaries throughout the world and throughout high latitude locations where glacial inputs introduce silt into water bodies. In assessing the vulnerability of technology components to sediment induced abrasion, one of the greatest concerns is the impact that the sediment may have on device components such as bearings and seals, failures of which could lead to both efficiency loss and catastrophic system failures.

Steady ablation on the surface of a two-layer composite

Energy Technology Data Exchange (ETDEWEB)

Lin, Wen-Shan [Chung Shan Institute of Science and Technology, P.O. Box 90008-15-3, Lung-Tan, Tao-Yuan, 32526 Taiwan (China)

2005-12-01

Discovered is a quasi-steady ablation phenomenon on the surface of a two-layer composite which is formed by a layer of ablative material and another layer of non-ablative substrate. Theoretical exact solutions of quasi-steady ablation rate, the associated temperature distribution and end-of-ablation time of this two-layer composite are derived. A criterion for the occurrence of quasi-steady ablation is presented also. A one-dimensional transient numerical model is developed to perform a number of numerical experiments and hence to verify the correctness of the above theoretical solutions for the current quasi-steady ablation phenomenon. Based on the current results, a new method of measuring the ablation (or sublimation) heat is also proposed. (author)

Large fragment production calculations in relativistic heavy-ion reactions

International Nuclear Information System (INIS)

Seixas de Oliveira, L.F.

1978-12-01

The abrasion-ablation model is briefly described and then used to calculate cross sections for production of large fragments resulting from target or projectile fragmentation in high-energy heavy-ion collisions. The number of nucleons removed from the colliding nuclei in the abrasion stage and the excitation energy of the remaining fragments (primary products) are calculated with the geometrical picture of two different models: the fireball and the firestreak models. The charge-to-mass dispersion of the primary products is calculated using either a model which assumes no correlations between proton and neutron positions inside the nucleus (hypergeometric distribution) or a model based upon the zero-point oscillations of the giant dipole resonance (NUC-GDR). Standard Weisskopf--Ewing statistical evaporation calculations are used to calculate final product distributions. Results of the pure abrasion-ablation model are compared with a variety of experimental data. The comparisons show the insufficiency of the extra-surface energy term used in the abrasion calculations. A frictional spectator interaction (FSI) is introduced which increases the average excitation energy of the primary products, and improves the results considerably in most cases. Agreements and discrepancies of the results calculated with the different theoretical assumptions and the experimental data are studied. Of particular relevance is the possibility of observing nuclear ground-state correlations.Results of the recently completed experiment of fragmentation of 213 Mev/A 40 Ar projectiles are studied and shown not to be capable of answering that question unambiguously. But predictions for the upcoming 48 Ca fragmentation experiment clearly show the possibility of observing correlation effects. 78 references

Finishing of display glass for mobile electronics using 3M Trizact diamond tile abrasive pads

Science.gov (United States)

Zheng, Lianbin; Fletcher, Tim; Na, Tee Koon; Sventek, Bruce; Romero, Vince; Lugg, Paul S.; Kim, Don

2010-10-01

This paper will describe a new method being used during the finishing of glass displays for mobile electronics including mobile hand held devices and notebook computers. The new method consists of using 3M TrizactTM Diamond Tile Abrasive Pads. TrizactTM Diamond Tile is a structured fixed abrasive grinding technology developed by 3M Company. The TrizactTM Diamond Tile structured abrasive pad consists of an organic (polymeric binder) - inorganic (abrasive mineral, i.e., diamond) composite that is used with a water-based coolant. TrizactTM Diamond Tile technology can be applied in both double and single side grinding applications. A unique advantage of TrizactTM Diamond Tile technology is the combination of high stock removal and low sub-surface damage. Grinding results will be presented for both 9 micron and 20 micron grades of TrizactTM Diamond Tile abrasive pads used to finish several common display glasses including Corning GorillaTM glass and Soda Lime glass.

Cryogenically assisted abrasive jet micromachining of polymers

International Nuclear Information System (INIS)

Getu, H; Papini, M; Spelt, J K

2008-01-01

The abrasive jet micromachining (AJM) of elastomers and polymers such as polydimethylsiloxane (PDMS), acrylonitrile butadiene styrene (ABS) and polytetrafluoroethylene (PTFE) for use in micro-fluidic devices was found to be very slow or impossible at room temperature. To enhance the material removal rate in such materials, a stream of liquid nitrogen (LN 2 ) was injected into the abrasive jet, cooling the target to cryogenic temperatures. Erosion rate measurements on the three polymeric materials (PDMS, ABS and PTFE) with and without the use of LN 2 were compared along with the profiles of micromachined channels and holes. It was found that the use of LN 2 cooling caused brittle erosion in PDMS, allowing it to be micromachined successfully. An erosion rate increase was also observed in PTFE and ABS at high and intermediate impact angles. The use of LN 2 also was found to reduce particle embedding

MR-Guided Laser Ablation of Osteoid Osteoma in an Open High-Field System (1.0 T)

International Nuclear Information System (INIS)

Streitparth, F.; Gebauer, B.; Melcher, I.; Schaser, K.; Philipp, C.; Rump, J.; Hamm, B.; Teichgraeber, U.

2009-01-01

Computed tomography is the standard imaging modality to minimize the extent of surgical or ablative treatment in osteoid osteomas. In the last 15 years, since a description of thermal ablation of osteoid osteomas was first published, this technique has become a treatment of choice for this tumor. We report the case of a 20-year-old man with an osteoid osteoma treated with laser ablation in an open high-field magnetic resonance imaging scanner (1.0 T). The tumor, located in the right fibula, was safely and effectively ablated under online monitoring. We describe the steps of this interventional procedure and discuss related innovative guidance and monitoring features and potential benefits compared with computed tomographic guidance.

Radiofrequency thermal ablation of benign cystic lesion: an experimental pilot study in a porcine gallbladder model

International Nuclear Information System (INIS)

Song, Ho Taek; Rhim, Hyun Chul; Choi, Jung Bin; Oh, Jae Cheon; Cho, On Koo; Koh, Byung Hee; Kim, Yong Soo; Seo, Heung Suk; Joo, Kyung Bin

2001-01-01

To determine whether radiofrequency thermal ablation can be used to treat benign cystic lesions in a porcine gallbladder model. This experimental study of radiofrequency thermal ablation involved the use of 15 exvivo porcine gallbladders and 15-G expandable needle electrodes. To investigate optimal temperature parameters, three groups of five were designated according to target temperature:Group A: 70 deg C; Group B: 80 deg C; Group C: 90 deg C. After the target temperature was reached, ablation lasted for one minute. Gallbladder width, height and length were measured before and after ablation , and the estimated volume reduction ratios of the three groups were compared. Whether adjacent liver parenchyma around the gallbladder fossa was ablated by heat conducted from hot bile was also determined, and the thickness of the ablated area of the liver was measured. The volume reduction ratio in Group A, B and C was 42.7%, 41.7% and 42.9%, respectively (ρ>.05). In all 15 cases, gallbladder walls lost their transparency and elasticity at about 70 deg C. In nine of ten cases in Groups B and C, the hepatic capsule around the gallbladder fossa was retracted at about 80 deg C. The mean thickness of liver parenchymal damage adjacent to the gallbladder was 5.4 mm in Group B and 9.8 mm in Group C. In Group A livers, only one case showed minimal gradual parenchymal change. Microscopically, all three groups showed complete coagulation necrosis of the wall. On the basis of this feasibility study, radiofrequency thermal ablation is potentially suitable for the ultrasound-guided treatment of symptomatic cystic lesions including benign hepatic or renal cyst

Management of Retrograde Peri-Implantitis Using an Air-Abrasive Device, Er,Cr:YSGG Laser, and Guided Bone Regeneration

Directory of Open Access Journals (Sweden)

Nikolaos Soldatos

2018-01-01

Full Text Available Background. The placement of an implant in a previously infected site is an important etiologic factor contributing to implant failure. The aim of this case report is to present the management of retrograde peri-implantitis (RPI in a first maxillary molar site, 2 years after the implant placement. The RPI was treated using an air-abrasive device, Er,Cr:YSGG laser, and guided bone regeneration (GBR. Case Description. A 65-year-old Caucasian male presented with a draining fistula associated with an implant at tooth #3. Tooth #3 revealed periapical radiolucency two years before the implant placement. Tooth #3 was extracted, and a ridge preservation procedure was performed followed by implant rehabilitation. A periapical radiograph (PA showed lack of bone density around the implant apex. The site was decontaminated with an air-abrasive device and Er,Cr:YSGG laser, and GBR was performed. The patient was seen every two weeks until suture removal, followed by monthly visits for 12 months. The periapical X-rays, from 6 to 13 months postoperatively, showed increased bone density around the implant apex, with no signs of residual clinical or radiographic pathology and probing depths ≤4 mm. Conclusions. The etiology of RPI in this case was the placement of an implant in a previously infected site. The use of an air-abrasive device, Er,Cr:YSGG, and GBR was utilized to treat this case of RPI. The site was monitored for 13 months, and increased radiographic bone density was noted.

Fragmentations of 40Ar at 213 MeV/nucleon

International Nuclear Information System (INIS)

Viyogi, Y.P.; Symons, T.J.M.; Doll, P.; Greiner, D.E.; Heckman, H.H.; Hendrie, D.L.; Lindstrom, P.J.; Mahoney, J.; Scott, D.K.; Van Bibber, K.; Westfall, G.D.; Wieman, H.; Crawford, H.J.; McParland, C.; Gelbke, C.K.

1979-01-01

Energy and isotope distributions were measured for peripheral reactions induced by 40 Ar at 213 MeV/nucleon. The data are consistent with the predictions of abrasion-ablation models. The influence of correlations in the nuclear ground state is discussed

Towards reproducible descriptions of neuronal network models.

Directory of Open Access Journals (Sweden)

Eilen Nordlie

2009-08-01

Full Text Available Progress in science depends on the effective exchange of ideas among scientists. New ideas can be assessed and criticized in a meaningful manner only if they are formulated precisely. This applies to simulation studies as well as to experiments and theories. But after more than 50 years of neuronal network simulations, we still lack a clear and common understanding of the role of computational models in neuroscience as well as established practices for describing network models in publications. This hinders the critical evaluation of network models as well as their re-use. We analyze here 14 research papers proposing neuronal network models of different complexity and find widely varying approaches to model descriptions, with regard to both the means of description and the ordering and placement of material. We further observe great variation in the graphical representation of networks and the notation used in equations. Based on our observations, we propose a good model description practice, composed of guidelines for the organization of publications, a checklist for model descriptions, templates for tables presenting model structure, and guidelines for diagrams of networks. The main purpose of this good practice is to trigger a debate about the communication of neuronal network models in a manner comprehensible to humans, as opposed to machine-readable model description languages. We believe that the good model description practice proposed here, together with a number of other recent initiatives on data-, model-, and software-sharing, may lead to a deeper and more fruitful exchange of ideas among computational neuroscientists in years to come. We further hope that work on standardized ways of describing--and thinking about--complex neuronal networks will lead the scientific community to a clearer understanding of high-level concepts in network dynamics, and will thus lead to deeper insights into the function of the brain.

In vivo effect of carbon dioxide laser-skin resurfacing and mechanical abrasion on the skin's microbial flora in an animal model.

Science.gov (United States)

Manolis, Evangelos N; Tsakris, Athanassios; Kaklamanos, Ioannis; Markogiannakis, Antonios; Siomos, Konstadinos

2006-03-01

Although beam-scanning carbon dioxide (CO2) lasers have provided a highly efficient tool for esthetic skin rejuvenation there has been no comprehensive animal studies looking into microbial skin changes following CO2 laser skin resurfacing. To evaluate the in vivo effects of CO2 laser skin resurfacing in an experimental rat model in comparison with mechanical abrasion on the skin microbial flora. Four separate cutaneous sections of the right dorsal surface of 10 Wistar rats were treated with a CO2 laser, operating at 18 W and delivering a radiant energy of 5.76 J/cm2, while mechanical abrasions of the skin were created on four sections of the left dorsal surface using a scalpel. Samples for culture and biopsies were obtained from the skin surfaces of the rats on day 1 of application of the CO2 laser or mechanical abrasion, as well as 10, 30, and 90 days after the procedure. The presence of four microorganisms (staphylococci, streptococci, diphtheroids, and yeasts) was evaluated as a microbe index for the skin flora, and colony counts were obtained using standard microbiological methods. Skin biopsy specimens, following CO2 laser treatment, initially showed epidermal and papillary dermal necrosis and later a re-epithelization of the epidermis as well as the generation of new collagen on the upper papillary dermis. The reduction in microbial counts on day 1 of the CO2 laser-inflicted wound was statistically significant for staphylococci and diphtheroids compared with the baseline counts (p=.004 and pSkin resurfacing using CO2 lasers considerably reduces microbial counts of most microorganisms in comparison with either normal skin flora or a scalpel-inflicted wound. This might contribute to the positive clinical outcome of laser skin resurfacing.

Validation of Proposed Metrics for Two-Body Abrasion Scratch Test Analysis Standards

Science.gov (United States)

Street, Kenneth W., Jr.; Kobrick, Ryan L.; Klaus, David M.

2013-01-01

Abrasion of mechanical components and fabrics by soil on Earth is typically minimized by the effects of atmosphere and water. Potentially abrasive particles lose sharp and pointed geometrical features through erosion. In environments where such erosion does not exist, such as the vacuum of the Moon, particles retain sharp geometries associated with fracturing of their parent particles by micrometeorite impacts. The relationship between hardness of the abrasive and that of the material being abraded is well understood, such that the abrasive ability of a material can be estimated as a function of the ratio of the hardness of the two interacting materials. Knowing the abrasive nature of an environment (abrasive)/construction material is crucial to designing durable equipment for use in such surroundings. The objective of this work was to evaluate a set of standardized metrics proposed for characterizing a surface that has been scratched from a two-body abrasion test. This is achieved by defining a new abrasion region termed Zone of Interaction (ZOI). The ZOI describes the full surface profile of all peaks and valleys, rather than just measuring a scratch width. The ZOI has been found to be at least twice the size of a standard width measurement; in some cases, considerably greater, indicating that at least half of the disturbed surface area would be neglected without this insight. The ZOI is used to calculate a more robust data set of volume measurements that can be used to computationally reconstruct a resultant profile for de tailed analysis. Documenting additional changes to various surface roughness par ameters also allows key material attributes of importance to ultimate design applications to be quantified, such as depth of penetration and final abraded surface roughness. Further - more, by investigating the use of custom scratch tips for specific needs, the usefulness of having an abrasion metric that can measure the displaced volume in this standardized

Heavy ion reactions at high energies

International Nuclear Information System (INIS)

Jakobsson, Bo.

1977-01-01

A review on heavy ion experiments at energies >0.1GeV/nucleon is presented. Reaction cross-sections, isotope production cross-sections and pion production in nucleus-nucleus collisions are discussed. Some recent models for heavy ion reactions like the abrasion-ablation model, the fireball model and the different shock-wave models are also presented

Robotic edge machining using elastic abrasive tool

Science.gov (United States)

Sidorova, A. V.; Semyonov, E. N.; Belomestnykh, A. S.

2018-03-01

The article describes a robotic center designed for automation of finishing operations, and analyzes technological aspects of an elastic abrasive tool applied for edge machining. Based on the experimental studies, practical recommendations on the application of the robotic center for finishing operations were developed.

Hydrodynamic stability theory of double ablation front structures in inertial confinement fusion

International Nuclear Information System (INIS)

Yanez Vico, C.

2012-11-01

For moderate-Z materials, the hydrodynamic structure of the ablation region formed by the irradiation of high intensity laser beams differs from that of low-Z materials (hydrogenic ablators). In particular, the role played by the radiative energy flux becomes non-negligible for increasing atomic number material and ended up forming a second ablation front. This structure of two separated ablation fronts, called double ablation (DA) front, was confirmed in the simulations carried out by Fujioka et al. In this work a linear stability theory of DA fronts is developed for direct-drive inertial confinement fusion targets. Two models are proposed. First, a sharp boundary model where the thin front approximation is assumed for both ablation fronts. The information about the corona region that permits to close the sharp boundary model is obtained from a prior self-consistent analysis of the electronic-radiative ablation (ERA) front. Numerical results are presented as well as an analytical approach for the radiation dominated regime of very steep double ablation front structure. Second, a self-consistent numerical method where the finite length of the ablation fronts is considered. Accurate hydrodynamic profiles are taken into account in the theoretical model by means of a fitting parameters method using one-dimensional simulation results. Numerical dispersion relation is compared to the analytical sharp boundary model showing an excellent agreement for the radiation dominated regime, and the stabilization due to smooth profiles. 2D simulations are presented to validate the linear stability theory

Dynamic Mechanical Analysis and Three-Body Abrasive Wear Behaviour of Thermoplastic Copolyester Elastomer Composites

Directory of Open Access Journals (Sweden)

Hemanth Rajashekaraiah

2014-01-01

Full Text Available Various amounts of short fibers (glass and carbon and particulate fillers like polytetrafluoroethylene (PTFE, silicon carbide (SiC, and alumina (Al2O3 were systematically introduced into the thermoplastic copolyester elastomer (TCE matrix for reinforcement purpose. The mechanical properties such as storage modulus, loss modulus, and Tan δ by dynamic mechanical analysis (DMA and three-body abrasive wear performance on a dry sand rubber wheel abrasion tester have been investigated. For abrasive wear study, the experiments were planned according to L27 orthogonal array by considering three factors and three levels. The complex moduli for TCE hybrid composites were pushed to a higher level relative to the TCE filled PTFE composite. At lower temperatures (in the glassy region, the storage modulus increases with increase in wt.% of reinforcement (fiber + fillers and the value is maximum for the composite with 40 wt.% reinforcement. The loss modulus and damping peaks were also found to be higher by the incorporation of SiC and Al2O3 microfillers. The routine abrasive wear test results indicated that TCE filled PTFE composite exhibited better abrasion resistance. Improvements in the abrasion resistance, however, have not been achieved by short-fiber and particlaute filler reinforcements. From the Taguchi’s experimental findings, optimal combination of control factors were obtained for minimum wear volume and also predictive correlations were proposed. Further, the worn surface morphology of the samples was discussed.

The abrasive effect of commercial whitening toothpastes on eroded enamel.

Science.gov (United States)

Mosquim, Victor; Martines Souza, Beatriz; Foratori Junior, Gerson Aparecido; Wang, Linda; Magalhães, Ana Carolina

2017-06-01

To evaluate the in vitro abrasive effect of commercial whitening toothpastes on eroded bovine enamel samples in respect to erosive tooth wear. 72 bovine crowns were embedded, polished and subjected to the baseline profile analysis. The samples were then protected in 2/3 of the enamel surface and were randomly assigned to six groups (n= 12/group): G1: Oral-B 3D White, G2: Close-up Diamond Attraction Power White, G3: Sorriso Xtreme White 4D, G4: Colgate Luminous White, G5: Crest (conventional toothpaste), G6:erosion only (control). All samples were submitted to an erosive pH cycling (4 x 90 seconds in 0.1% citric acid, pH 2.5, per day) and abrasive challenges (2 x 15 seconds, per day) for 7 days. After the first and the last daily cycles, the samples were subjected to abrasive challenges, using a toothbrushing machine, soft toothbrushes and slurry of the tested toothpastes (1.5 N). Between the challenges, the samples were immersed in artificial saliva. The final profile was obtained and overlaid to the baseline profile for the calculation of the erosive tooth wear (μm). The data were subjected to Kruskal-Wallis/Dunn tests (Penamel wear (3.68±1.06 μm), similarly to G3 (3.17± 0.80 μm) and G4 (3.44± 1.29 μm). G3 and G4 performed similarly between them and compared with G5 (2.35± 1.44 μm). G2 (1.51± 0.95 μm) and G6 (0.85± 0.36 μm) showed the lowest enamel wear, which did not differ between them and from G5. Oral-B 3D White showed the highest abrasive potential while Close-up Diamond Attraction Power White showed the lowest abrasive potential on eroded enamel in vitro. This study showed that some commercial whitening toothpastes, especially those containing pyrophosphate associated with hydrated silica, enhanced enamel erosive wear.

Effect analysis of material properties of picosecond laser ablation for ABS/PVC

Science.gov (United States)

Tsai, Y. H.; Ho, C. Y.; Chiou, Y. J.

2017-06-01

This paper analytically investigates the picosecond laser ablation of ABS/PVC. Laser-pulsed ablation is a wellestablished tool for polymer. However the ablation mechanism of laser processing for polymer has not been thoroughly understood yet. This study utilized a thermal transport model to analyze the relationship between the ablation rate and laser fluences. This model considered the energy balance at the decomposition interface and Arrhenius law as the ablation mechanisms. The calculated variation of the ablation rate with the logarithm of the laser fluence agrees with the measured data. It is also validated in this work that the variation of the ablation rate with the logarithm of the laser fluence obeys Beer's law for low laser fluences. The effects of material properties and processing parameters on the ablation depth per pulse are also discussed for picosecond laser processing of ABS/PVC.

Damage to the edge of steel stampings and abrasive during ultrasonic hydroabrasive machining

International Nuclear Information System (INIS)

Dokuchaeva, V.A.; Chernov, A.P.

1976-01-01

Principles have been established explaining the fracture of abrasive material in the process of ultrasonic hydroabrasive treatment, and a method is proposed suitable for the calculation of steel barb erosion in the hydroabrasive flux. It is assumed that fracture occurs along the entire edge surface and that the losses caused by plastic deformation are small. Conclusion has been made as to the governing the change of the abrasive particle size in the time of treatment. It is shown that the most serious fracture takes place at initial stage of the treatment, terminating practically after 60 minutes of operation. Curves showing the distribution of boron carbide abrasive particles are presented

CORECOOL, model description of the programme

International Nuclear Information System (INIS)

Andersen, J.G.M.; Abel-Larsen, H.

1978-11-01

CORECOOL, Convection and Radiation Emergency Cooling, is a model for the two-phase flow and heat transfer in a fuel element during the core heat-up phase following a loss of coolant accident. The model for the two-phase flow is based on a solution of the conservation equations with a separate description of the two phases and thermodynamic non-equilibrium. The flow-regimes considered are drop flow and film flow. The heat transfer consists of convection, sputtering and radiation heat transfer. The documentation of CORECOOL consists of four parts: I) model description, II) programme description (COMMERCIAL), III) users guide (COMMERCIAL) IV) verification (COMMERCIAL). CORECOOL is a joint project between Risoe National Laboratory Denmark and General Electric Company, San Jose, USA. (author)

Landau-Darrieus instability in an ablation front

International Nuclear Information System (INIS)

Piriz, A.R.; Portugues, R.F.

2003-01-01

An analytical model that shows the conditions for the existence of the Landau-Darrieus instability of an ablation front is presented. The model seems to agree with recently claimed simulation results [L. Masse et al., Proceedings of the 1st International Conference on Inertial Fusion Sciences and Applications (Elsevier, Paris, 2000), p. 220]. The model shows that the ablation front can be unstable in absence of gravity when the thermal flux is inhibited within the supercritical region of the corona

Material Abrasive Water Jet Cutting Investigation by Means Accompanying Physical Phenomena

OpenAIRE

Kinik, D.; Gánovská, B.; Hloch, S. (Sergej); Cárach, J.; Lehocká, D.

2013-01-01

The paper deals with the indirect ways of on-line monitoring of technological processes of cutting. The objective of the study is a design of on-line monitoring system for the cutting technology through an abrasive water jet. In cutting by the abrasive water jet two parallel phenomena are formed. The phenomena are represented by generated surface and vibrations. For the purpose of proving of the hypothetical assumptions on dependence of generated surface quality on vibrations the ex...

3D transient model to predict temperature and ablated areas during laser processing of metallic surfaces

Directory of Open Access Journals (Sweden)

Babak. B. Naghshine

2017-02-01

Full Text Available Laser processing is one of the most popular small-scale patterning methods and has many applications in semiconductor device fabrication and biomedical engineering. Numerical modelling of this process can be used for better understanding of the process, optimization, and predicting the quality of the final product. An accurate 3D model is presented here for short laser pulses that can predict the ablation depth and temperature distribution on any section of the material in a minimal amount of time. In this transient model, variations of thermal properties, plasma shielding, and phase change are considered. Ablation depth was measured using a 3D optical profiler. Calculated depths are in good agreement with measured values on laser treated titanium surfaces. The proposed model can be applied to a wide range of materials and laser systems.

Comparison of wet radiofrequency ablation with dry radiofrequency ablation and radiofrequency ablation using hypertonic saline preinjection: ex vivo bovine liver

International Nuclear Information System (INIS)

Lee, Jeong Min; Han, Joon Koo; Kim, Se Hyung; Lee, Jae Young; Park, Hee Sun; Hur, Hurn; Choi, Byung Ihn; Shin, Kyung Sook

2004-01-01

We wished to compare the in-vitro efficiency of wet radiofrequency (RF) ablation with the efficiency of dry RF ablation and RF ablation with preinjection of NaCl solutions using excised bovine liver. Radiofrequency was applied to excised bovine livers in a monopolar mode for 10 minutes using a 200 W generator and a perfused-cooled electrode with or without injection or slow infusion of NaCl solutions. After placing the perfused-cooled electrode in the explanted liver, 50 ablation zones were created with five different regimens: group A; standard dry RF ablation, group B; RF ablation with 11 mL of 5% NaCl solution preinjection, group C; RF ablation with infusion of 11 mL of 5% NaCl solution at a rate of 1 mL/min, group D; RFA with 6 mL of 36% NaCl solution preinjection, group E; RF ablation with infusion of 6 mL of 36% NaCl solution at a rate of 0.5 mL/min. In groups C and E, infusion of the NaCl solutions was started 1 min before RF ablation and then maintained during RF ablation (wet RF ablation). During RF ablation, we measured the tissue temperature at 15 mm from the electrode. The dimensions of the ablation zones and changes in impedance, current and liver temperature during RF ablation were then compared between the groups. With injection or infusion of NaCl solutions, the mean initial tissue impedance prior to RF ablation was significantly less in groups B, C, D, and E (43-75 Ω) than for group A (80 Ω) (ρ 3 in group A; 12.4 ± 3.8 cm 3 in group B; 80.9 ± 9.9 cm 3 in group C; 45.3 ± 11.3 cm 3 in group D and 81.6 ± 8.6 cm 3 in group E. The tissue temperature measured at 15 mm from the electrode was higher in groups C, D and E than other groups (ρ < 0.05): 53 ± 12 .deg. C in group A, 42 ± 2 .deg. C in group B, 93 ± 8 .deg. C in group C; 79 ± 12 .deg. C in group D and 83 ± 8 .deg.C in group E. Wet RF ablation with 5% or 36% NaCl solutions shows better efficiency in creating a large ablation zone than does dry RF ablation or RF ablation with

A model of early formation of uranium molecular oxides in laser-ablated plasmas

Science.gov (United States)

Finko, Mikhail; Curreli, Davide; Azer, Magdi; Weisz, David; Crowhurst, Jonathan; Rose, Timothy; Koroglu, Batikan; Radousky, Harry; Zaug, Joseph; Armstrong, Mike

2017-10-01

An important problem within the field of nuclear forensics is fractionation: the formation of post-detonation nuclear debris whose composition does not reflect that of the source weapon. We are investigating uranium fractionation in rapidly cooling plasma using a combined experimental and modeling approach. In particular, we use laser ablation of uranium metal samples to produce a low-temperature plasma with physical conditions similar to a condensing nuclear fireball. Here we present a first plasma-chemistry model of uranium molecular species formation during the early stage of laser ablated plasma evolution in atmospheric oxygen. The system is simulated using a global kinetic model with rate coefficients calculated according to literature data and the application of reaction rate theory. The model allows for a detailed analysis of the evolution of key uranium molecular species and represents the first step in producing a uranium fireball model that is kinetically validated against spatially and temporally resolved spectroscopy measurements. This project was sponsored by the DoD, Defense Threat Reduction Agency, Grant HDTRA1-16- 1-0020. This work was performed in part under the auspices of the U.S. DoE by Lawrence Livermore National Laboratory under Contract DE-AC52- 07NA27344.

Chemical mechanical polishing of hard disk substrate with {alpha}-alumina-g-polystyrene sulfonic acid composite abrasive

Energy Technology Data Exchange (ETDEWEB)

Lei Hong, E-mail: hong_lei2005@yahoo.com.c [Research Center of Nano-science and Nano-technology, Shanghai University, Shanghai 200444 (China); Bu Naijing; Chen Ruling; Hao Ping [Research Center of Nano-science and Nano-technology, Shanghai University, Shanghai 200444 (China); Neng Sima; Tu Xifu; Yuen Kwok [Shenzhen Kaifa Magnetic Recording Co., LTD, Shenzhen, 518035 (China)

2010-05-03

{alpha}-Alumina-g-polystyrene sulfonic acid ({alpha}-Al{sub 2}O{sub 3}-g-PSS) composite abrasive was prepared by surface activation, graft polymerization and sulfonation, successively. The composition, dispersibility and morphology of the product were characterized by Fourier transformed infrared spectroscopy, laser particle size analysis and scanning electron microscopy, respectively. The chemical mechanical polishing (CMP) performances of the composite abrasive on hard disk substrate with nickel-phosphorous plating were investigated. The microscopy images of the polished surfaces show that {alpha}-Al{sub 2}O{sub 3}-g-PSS composite abrasive results in improved CMP and post-CMP cleaning performances than pure {alpha}-alumina abrasive under the same testing conditions.

Liquid abrasive grit blasting literature search and decontamination scoping tests report

International Nuclear Information System (INIS)

Ferguson, R.L.

1993-10-01

Past decontamination and solvent recovery activities at the Idaho Chemical Processing Plant (ICPP) have resulted in the accumulation of 1.5 million gallons of radioactively contaminated sodium-bearing liquid waste. Future decontamination activities at the ICPP could result in the production of 5 million gallons or more of sodium-bearing waste using the current decontamination techniques of chemical/water flushes and steam jet cleaning. With the curtailment of reprocessing at the ICPP, the focus of decontamination is shifting from maintenance for continued operation of the facilities to decommissioning. As decommissioning plans are developed, new decontamination methods must be used which result in higher decontamination factors and generate lower amounts of sodium-bearing secondary waste. The primary initiative of the WINCO Decontamination Development Program is the development of methods to eliminate/minimize the use of sodium-bearing decontamination chemicals. One method that was chosen for cold scoping studies during FY-93 was abrasive grit blasting. Abrasive grit blasting has been used in many industries and a vast amount of research and development has already been conducted. However, new grits, process improvements and ICPP applicability was investigated. This evaluation report is a summary of the research efforts and scoping tests using the liquid abrasive grit blasting decontamination technique. The purpose of these scoping tests was to determine the effectiveness of three different abrasive grits: plastic beads, glass beads and alumina oxide

Enhanced Radiofrequency Ablation With Magnetically Directed Metallic Nanoparticles.

Science.gov (United States)

Nguyen, Duy T; Tzou, Wendy S; Zheng, Lijun; Barham, Waseem; Schuller, Joseph L; Shillinglaw, Benjamin; Quaife, Robert A; Sauer, William H

2016-05-01

Remote heating of metal located near a radiofrequency ablation source has been previously demonstrated. Therefore, ablation of cardiac tissue treated with metallic nanoparticles may improve local radiofrequency heating and lead to larger ablation lesions. We sought to evaluate the effect of magnetic nanoparticles on tissue sensitivity to radiofrequency energy. Ablation was performed using an ablation catheter positioned with 10 g of force over prepared ex vivo specimens. Tissue temperatures were measured and lesion volumes were acquired. An in vivo porcine thigh model was used to study systemically delivered magnetically guided iron oxide (FeO) nanoparticles during radiofrequency application. Magnetic resonance imaging and histological staining of ablated tissue were subsequently performed as a part of ablation lesion analysis. Ablation of ex vivo myocardial tissue treated with metallic nanoparticles resulted in significantly larger lesions with greater impedance changes and evidence of increased thermal conductivity within the tissue. Magnet-guided localization of FeO nanoparticles within porcine thigh preps was demonstrated by magnetic resonance imaging and iron staining. Irrigated ablation in the regions with greater FeO, after FeO infusion and magnetic guidance, created larger lesions without a greater incidence of steam pops. Metal nanoparticle infiltration resulted in significantly larger ablation lesions with altered electric and thermal conductivity. In vivo magnetic guidance of FeO nanoparticles allowed for facilitated radiofrequency ablation without direct infiltration into the targeted tissue. Further research is needed to assess the clinical applicability of this ablation strategy using metallic nanoparticles for the treatment of cardiac arrhythmias. © 2016 American Heart Association, Inc.

Maintenance and preservation of concrete structures. Report 3: Abrasion-erosion resistance of concrete

Science.gov (United States)

Liu, T. C.

1980-07-01

This report describes a laboratory test program on abrasion-erosion resistance of concrete, including the development of a new underwater abrasion-erosion test method. This program was designed to evaluate the relative abrasion-erosion resistance of various materials considered for use in the repair of erosion-damaged concrete structures. The test program encompassed three concrete types (conventional concrete, fiber-reinforced concrete, and polymer concrete); seven aggregate types (limestone, chert, trap rock, quartzite, granite, siliceous gravel, and slag); three principal water-cement rations (0.72, 0.54, and 0.40); and six types of surface treatment (vacuum, polyurethane coating, acrylic mortar coating, epoxy mortar coating, furan resin mortar coating, and iron aggregate topping). A total of 114 specimens made from 41 batches of concrete was tested. Based on the test data obtained, a comprehensive evaluation of the effects of various parameters on the abrasion-erosion resistance of concrete was presented. Materials suitable for use in the repair of erosion-damaged concrete structures were recommended. Additional work to correlate the reported findings with field performance was formulated.

Nonlinear Analysis of Two-phase Circumferential Motion in the Ablation Circumstance

Science.gov (United States)

Xiao-liang, Xu; Hai-ming, Huang; Zi-mao, Zhang

2010-05-01

In aerospace craft reentry and solid rocket propellant nozzle, thermal chemistry ablation is a complex process coupling with convection, heat transfer, mass transfer and chemical reaction. Based on discrete vortex method (DVM), thermal chemical ablation model and particle kinetic model, a computational module dealing with the two-phase circumferential motion in ablation circumstance is designed, the ablation velocity and circumferential field can be thus calculated. The calculated nonlinear time series are analyzed in chaotic identification method: relative chaotic characters such as correlation dimension and the maximum Lyapunov exponent are calculated, fractal dimension of vortex bulbs and particles distributions are also obtained, thus the nonlinear ablation process can be judged as a spatiotemporal chaotic process.

A descriptive ecosystem model - a strategy for model development during site investigations

International Nuclear Information System (INIS)

Loefgren, Anders

2003-09-01

This report describes a strategy for the development of a site descriptive model for the surface ecosystem on the potential deep repository sites. The surface ecosystem embraces many disciplines, and these have to be identified, described and integrated in order to construct a descriptive ecosystem model that describes and quantifies biotic and abiotic patterns and processes of importance for the ecosystem on the site. The descriptive model includes both present day conditions and historical information. The descriptive ecosystem model will be used to supply input data for the safety assessment and to serve as the baseline model for devising a monitoring program to detect short-term disturbances caused first by the site investigations and later by the construction of the deep repository. Furthermore, it will serve as a reference for future comparisons to determine more long-term effects or changes caused by the deep repository. The report adopts a non-site-specific approach focusing on the following aims: 1. To present and define the properties that will constitute the descriptive ecosystem model. 2. To present a methodology for determining those properties. 3. To describe and develop the framework for the descriptive ecosystem model by integrating the different properties. 4. To present vital data from other site descriptive models such as those for geology or hydrogeology that interacts with and affects the descriptive ecosystem model. The properties are described under four different sections: general physical properties of the landscape, the terrestrial system, the limnic system and the marine system. These headings are further subdivided into entities that integrate properties in relation to processes

A descriptive ecosystem model - a strategy for model development during site investigations

Energy Technology Data Exchange (ETDEWEB)

Loefgren, Anders [Stockholm Univ. (Sweden). Dept. of Botany; Lindborg, Tobias [Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden)

2003-09-01

This report describes a strategy for the development of a site descriptive model for the surface ecosystem on the potential deep repository sites. The surface ecosystem embraces many disciplines, and these have to be identified, described and integrated in order to construct a descriptive ecosystem model that describes and quantifies biotic and abiotic patterns and processes of importance for the ecosystem on the site. The descriptive model includes both present day conditions and historical information. The descriptive ecosystem model will be used to supply input data for the safety assessment and to serve as the baseline model for devising a monitoring program to detect short-term disturbances caused first by the site investigations and later by the construction of the deep repository. Furthermore, it will serve as a reference for future comparisons to determine more long-term effects or changes caused by the deep repository. The report adopts a non-site-specific approach focusing on the following aims: 1. To present and define the properties that will constitute the descriptive ecosystem model. 2. To present a methodology for determining those properties. 3. To describe and develop the framework for the descriptive ecosystem model by integrating the different properties. 4. To present vital data from other site descriptive models such as those for geology or hydrogeology that interacts with and affects the descriptive ecosystem model. The properties are described under four different sections: general physical properties of the landscape, the terrestrial system, the limnic system and the marine system. These headings are further subdivided into entities that integrate properties in relation to processes.

Abrasive Wear Resistance of the Iron- and WC-based Hardfaced Coatings Evaluated with Scratch Test Method

Directory of Open Access Journals (Sweden)

A. Vencl

2013-06-01

Full Text Available Abrasive wear is one of the most common types of wear, which makesabrasive wear resistance very important in many industries. Thehard facing is considered as useful and economical way to improve theperformance of components submitted to severe abrasive wear conditions, with wide range of applicable filler materials. The abrasive wear resistance of the three different hardfaced coatings (two iron‐based and one WC‐based, which were intended to be used for reparation of the impact plates of the ventilation mill, was investigated and compared. Abrasive wear tests were carried‐out by using the scratch tester under the dry conditions. Three normal loads of 10, 50 and 100 N and the constant sliding speed of 4 mm/s were used. Scratch test was chosen as a relatively easy and quick test method. Wear mechanism analysis showed significant influence of the hardfaced coatings structure, which, along with hardness, has determined coatings abrasive wear resistance.

Pre-polishing on a CNC platform with bound abrasive contour tools

Science.gov (United States)

Schoeffer, Adrienne E.

2003-05-01

Deterministic micorgrinding (DMG) of optical glasses and ceramics is the commercial manufacturing process of choice to shape glass surfaces prior to final finishing. This process employs rigid bound matrix diamond tooling resulting in surface roughness values of 3-51.tm peak to valley and 100-400nm rms, as well as mid-spatial frequency tool marks that require subsequent removal in secondary finishing steps. The ability to pre-polish optical surfaces within the grinding platform would reduce final finishing process times. Bound abrasive contour wheels containing cerium oxide, alumina or zirconia abrasives were constructed with an epoxy matrix. The effects of abrasive type, composition, and erosion promoters were examined for tool hardness (Shore D), and tested with commercial optical glasses in an OptiproTM CNC grinding platform. Metrology protocols were developed to examine tool wear and subsequent surface roughness. Work is directed to demonstrating effective material removal, improved surface roughness and cutter mark removal.

Experimental Study on Layered Ice Bonded Abrasive Polishing of Glass-ceramics

Directory of Open Access Journals (Sweden)

Yuli SUN

2014-12-01

Full Text Available Layered ice bonded abrasive tools (LIBAT is a new kind of one which not only has the ability of lapping and polishing but also has the effect of self-dressing. In this paper, two kinds of layered ice bonded abrasive tools were designed and manufactured. Experimental studies on layered ice bonded abrasive (LIBA polishing of glass-ceramics were conducted. The results show that the surface topography of glass-ceramics polished by micro α-Al2O3-nano α-Al2O3 LIBAT is better than that of polished by micro α-Al2O3-nano SiO2 LIBAT. The surface roughness Sa of glass-ceramics polished by the two kinds of LIBAT is at the nanometer scale. The reasons of this phenomenon were analyzed. The experimental results illustrate that the LIBAT shows good effect and can be used in production practice. DOI: http://dx.doi.org/10.5755/j01.ms.20.4.6149

HYDRO-ABRASIVE RESISTANCE AND MECHANICAL PROPERTIES OF CONCRETE WITH ADDED FLY ASH

OpenAIRE

Ristić, Nenad; Grdić, Zoran; Topličić-Ćurčić, Gordana

2015-01-01

The durability of hydraulic engineering structures mostly depends on the resistance of their concrete surfaces to mechanical abrasion. In this paper, we study the hydro-abrasive resistance and mechanical properties of concrete in which cement is partially replaced with fly ash in various proportions. To evaluate these concretes, we measured their compressive strength, flexural strength, static modulus of elasticity, ultrasound velocity through concrete, and sclerometer rebound. The hydro-abra...

An experimental study of simultaneous ablation with dual probes in radiofrequency thermal ablation

International Nuclear Information System (INIS)

Jang, Il Soo; Rhim, Hyun Chul; Koh, Byung Hee; Cho, On Koo; Seo, Heung Suk; Kim, Yong Soo; Kim, Young Sun; Heo, Jeong Nam

2003-01-01

To determine the differences between sequential ablation with a single probe and simultaneous ablation with dual probes. Using two 14-gauge expandable probes (nine internal prongs with 4-cm deployment), radiofrequency was applied sequentially (n=8) or simultaneously (n=8) to ten ex-vivo cow livers. Before starting ablation, two RF probes with an inter-probe space of 2 cm (n=8) or 3 cm (n=8) were inserted. In the sequential group, switching the connecting cable to an RF generator permitted ablation with the second probe just after ablation with the first probe had finished. In the simultaneous group, single ablation was performed only after connecting the shafts of both RF probes using a connection device. Each ablation lasted 7 minutes at a target temperature of 105-110 .deg. C. The size and shape of the ablated area, and total ablation time were then compared between the two groups. With 2-cm spacing, the group, mean length and overlapping width of ablated lesions were, respectively, 5.20 and 5.05 cm in the sequential group (n=4), and 5.81 and 5.65 cm in the simultaneous group (n=4). With 3-cm spacing, the corresponding figures were 4.99 and 5.60 cm in the sequential group (n=4), and 6.04 and 6.78 cm in the simultaneous group (n=4). With 2-cm spacing, the mean depth of the proximal waist was 0.58 cm in the sequential (group and 0.28 cm in the simultaneous group, while with 3-cm spacing, the corresponding figures were 1.65 and 1.48 cm. In neither group was there a distal waist. Mean total ablation time was 23.4 minutes in the sequential group and 14 minutes in the simultaneous group. In terms of ablation size and ablation time, simultaneous radiofrequency ablation with dual probes is superior to sequential ablation with a single probe. A simultaneous approach will enable an operator to overcome difficulty in probe repositioning during overlapping ablation, resulting in complete ablation with a successful safety margin

A comparison of microwave ablation and bipolar radiofrequency ablation both with an internally cooled probe: Results in ex vivo and in vivo porcine livers

International Nuclear Information System (INIS)

Yu Jie; Liang Ping; Yu Xiaoling; Liu Fangyi; Chen Lei; Wang Yang

2011-01-01

Purpose: The purpose of this study was to compare the effectiveness of microwave (MW) ablation and radiofrequency (RF) ablation using a single internally cooled probe in a hepatic porcine model. Materials and methods: In the ex vivo experiment, MW ablations (n = 40) were performed with a 2450 MHz and 915 MHz needle antenna, respectively at 60 W, 70 W power settings. Bipolar RF ablations (n = 20) were performed with a 3-cm (T30) and 4-cm (T40) active tip needle electrodes, respectively at a rated power 30 W and 40 W according to automatically systematic power setting. In the in vivo experiment, the 2450 MHz and 915 MHz MW ablation both at 60 W and T30 bipolar RF ablation at 30 W were performed (n = 30). All of the application time were 10 min. Long-axis diameter (Dl), short-axis diameter (Ds), ratio of Ds/Dl, the temperature data 5 mm from the needle and the time of temperature 5 mm from the needle rising to 54 deg. C were measured. Results: Both in ex vivo and in vivo models, Ds and Dl of 915 MHz MW ablations were significantly larger than all the RF ablations (P < 0.05); the Ds for all the 2450 MHz MW ablations were significantly larger than that of T30 RF ablations (P < 0.05). 2450 MHz MW and T30 RF ablation tended to produce more elliptical-shaped ablation zone. Tissue temperatures 5 mm from the needle were considerably higher with MW ablation, meanwhile MW ablation achieved significantly faster rate of temperature rising to 54 deg. C than RF ablation. For in vivo study after 10 min of ablation, the Ds and Dl of 2450 MHz MW, 915 MHz MW and Bipolar RF were 2.35 ± 0.75, 2.95 ± 0.32, 1.61 ± 0.33 and 3.86 ± 0.81, 5.79 ± 1.03, 3.21 ± 0.51, respectively. Highest tissue temperatures 5 mm from the needle were 80.07 ± 12.82 deg. C, 89.07 ± 3.52 deg. C and 65.56 ± 15.31 deg. C and the time of temperature rising to 54 deg. C were respectively 37.50 ± 7.62 s, 24.50 ± 4.09 s and 57.29 ± 23.24 s for three applicators. Conclusion: MW ablation may have higher

Design of a new abrasive slurry jet generator

Science.gov (United States)

Wang, F. C.; Shi, L. L.; Guo, C. W.

2017-12-01

With the advantages of a low system working pressure, good jet convergence and high cutting quality, abrasive slurry jet (ASJ) has broad application prospects in material cutting and equipment cleaning. Considering that the generator plays a crucial role in ASJ system, the paper designed a new type ASJ generator using an electric oil pump, a separate plunger cylinder, and a spring energized seal. According to the determining of structure shape, size and seal type, a new ASJ generator has been manufactured out and tested by a series of experiments. The new generator separates the abrasive slurry from the dynamic hydraulic oil, which can improve the service life of the ASJ system. And the new ASJ system can reach 40 MPa and has good performance in jet convergence, which deserves to popularization and application in materials machining.

MRI Reconstructions of Human Phrenic Nerve Anatomy and Computational Modeling of Cryoballoon Ablative Therapy.

Science.gov (United States)

Goff, Ryan P; Spencer, Julianne H; Iaizzo, Paul A

2016-04-01

The primary goal of this computational modeling study was to better quantify the relative distance of the phrenic nerves to areas where cryoballoon ablations may be applied within the left atria. Phrenic nerve injury can be a significant complication of applied ablative therapies for treatment of drug refractory atrial fibrillation. To date, published reports suggest that such injuries may occur more frequently in cryoballoon ablations than in radiofrequency therapies. Ten human heart-lung blocs were prepared in an end-diastolic state, scanned with MRI, and analyzed using Mimics software as a means to make anatomical measurements. Next, generated computer models of ArticFront cryoballoons (23, 28 mm) were mated with reconstructed pulmonary vein ostias to determine relative distances between the phrenic nerves and projected balloon placements, simulating pulmonary vein isolation. The effects of deep seating balloons were also investigated. Interestingly, the relative anatomical differences in placement of 23 and 28 mm cryoballoons were quite small, e.g., the determined difference between mid spline distance to the phrenic nerves between the two cryoballoon sizes was only 1.7 ± 1.2 mm. Furthermore, the right phrenic nerves were commonly closer to the pulmonary veins than the left, and surprisingly tips of balloons were further from the nerves, yet balloon size choice did not significantly alter calculated distance to the nerves. Such computational modeling is considered as a useful tool for both clinicians and device designers to better understand these associated anatomies that, in turn, may lead to optimization of therapeutic treatments.

Effects of hardness of abrasive grains on surface roughness of work piece in PVA bonded grinding wheel

International Nuclear Information System (INIS)

Nitta, S.; Takata, A.; Ishizaki, K.

2000-01-01

The purpose of this study is to clarify relation between hardness of abrasive grains and surface roughness of work piece in the case of PVA (Polyvinyl alcohol) bonded grinding wheels. Two PVA bonded grinding wheels; with diamond or silicon carbide as abrasive grains and grinding of glass and aluminum alloy was performed. The PVA bonded grinding wheels The PVA bonded grinding wheel with silicon carbide could not grind the glass. Because insufficiency in hardness, the PVA bonded grinding wheel with the diamond abrasive grains caused deep scratch on the aluminum alloy. It was found that the final surface roughness of the work piece was not proportional to the hardness of abrasive grains. The suitable hardness of abrasive grains will be obtained by the hardness of work piece. Copyright (2000) AD-TECH - International Foundation for the Advancement of Technology Ltd

Universal Survival Curve and Single Fraction Equivalent Dose: Useful Tools in Understanding Potency of Ablative Radiotherapy

International Nuclear Information System (INIS)

Park, Clint; Papiez, Lech; Zhang Shichuan; Story, Michael; Timmerman, Robert D.

2008-01-01

Purpose: Overprediction of the potency and toxicity of high-dose ablative radiotherapy such as stereotactic body radiotherapy (SBRT) by the linear quadratic (LQ) model led to many clinicians' hesitating to adopt this efficacious and well-tolerated therapeutic option. The aim of this study was to offer an alternative method of analyzing the effect of SBRT by constructing a universal survival curve (USC) that provides superior approximation of the experimentally measured survival curves in the ablative, high-dose range without losing the strengths of the LQ model around the shoulder. Methods and Materials: The USC was constructed by hybridizing two classic radiobiologic models: the LQ model and the multitarget model. We have assumed that the LQ model gives a good description for conventionally fractionated radiotherapy (CFRT) for the dose to the shoulder. For ablative doses beyond the shoulder, the survival curve is better described as a straight line as predicted by the multitarget model. The USC smoothly interpolates from a parabola predicted by the LQ model to the terminal asymptote of the multitarget model in the high-dose region. From the USC, we derived two equivalence functions, the biologically effective dose and the single fraction equivalent dose for both CFRT and SBRT. Results: The validity of the USC was tested by using previously published parameters of the LQ and multitarget models for non-small-cell lung cancer cell lines. A comparison of the goodness-of-fit of the LQ and USC models was made to a high-dose survival curve of the H460 non-small-cell lung cancer cell line. Conclusion: The USC can be used to compare the dose fractionation schemes of both CFRT and SBRT. The USC provides an empirically and a clinically well-justified rationale for SBRT while preserving the strengths of the LQ model for CFRT

Post ablation recanalization of varicose veins of the limbs: Comparison ablation method of mechanochemical and laser procedure

Science.gov (United States)

Suhartono, R.; Irfan, W.; Wangge, G.; Moenadjat, Y.; Destanto, W. I.

2017-08-01

Endovenous ablation has been performed for varicose veins of the limbs in Indonesia since 2010. Endovenous laser ablation (EVLA) therapy has been performed in Cipto Mangunkusumo Hospital (RSCM) in Jakarta, and mechanochemical ablation (MOCA) has been conducted in Fatmawati Hospital. This was a descriptive analytical study, with a cross-sectional design to analyze post-ablation recanalization after MOCA and EVLA procedures. Patients who had undergone MOCA or EVLA treatment were interviewed 3-18 months after the procedures. All the patients underwent vascular ultrasonography (USG) of the operated limb to assess recanalization. Secondary presurgery data were obtained from the patients’ from patients’ medical records. The clinical characteristics of the subjects were recorded to compare the potential correlation between these characteristics and recanalization post-MOCA and EVLA procedures. All the data were analyzed using SPSS ver. 20.0. The study consisted of 43 limbs: 24 treated by MOCA and 19 treated by EVLA. Most subjects in the MOCA group were 7 mm in 13/19 extremities. In the MOCA group, total recanalization occurred in 2/24 extremities, and partial recanalization occurred in 8/24 extremities. In the EVLA group, total recanalization occurred in 1/19 extremities, and partial recanalization occurred in 3/19 extremities. The association between the clinical characteristics of the patients and recanalization was not statistically significant (p > 0.05). The recanalization tendency was higher in the MOCA group than in the EVLA group. Although there was no statistically significant association between the clinical characteristics of the patients and recanalization, the largest diameter of the VSM presurgery (>7 mm) was higher in 3/4 extremities in the MOCA group, as compared to 3/13 extremities in the EVLA group.

MODIFIED KACHUGIN METHOD OF ALTERNATIVE SOFTWARE-BASED PROJECTION OF THE PATTERN OF REORGANIZATION OF ABRASION SHORES OF WATER RESERVOIRS IN THE FLAT TERRAIN

Directory of Open Access Journals (Sweden)

Sobol' Il'ya Stanislavovich

2012-10-01

Full Text Available Presently, effective regulations employed in the Russian Federation recommend the use of the methods developed by E.G. Kachuchin, G.S. Zolotarev, I.A. Pecherkin, etc. for the projection of patterns of reorganization of coastlines of water reservoirs. One of these methods, developed by E.G. Kachugin, belongs to the group of power methods based on the hypothesis that the amplitudes of destruction of the coast are proportionate to the total wave energy alongside the coastline. The Kachugin method was reworked into a computer-based two-dimensional engineering model of reorganization of the abrasion shore. The model generates alternative projections. It simulates the processes of washout and accumulation of soil in the coastal area and solves the problem of predicting the potential profile of the shore within a pre-set time period or until the abrasion is smoothed away in the course of formation of coastal shallows. The model testing has proven its efficiency in solving the engineering problems of projecting the line of reservoir abrasion shores with a high degree of reliability.

Effects of Load and Speed on Wear Rate of Abrasive Wear for 2014 Al Alloy

Science.gov (United States)

Odabas, D.

2018-01-01

In this paper, the effects of the normal load and sliding speed on wear rate of two-body abrasive wear for 2014 Al Alloy were investigated in detail. In order to understand the variation in wear behaviour with load and speed, wear tests were carried out at a sliding distance of 11 m, a speed of 0.36 m/s, a duration of 30 s and loads in the range 3-11 N using 220 grit abrasive paper, and at a speed range 0.09-0.90 m/s, a load of 5 N and an average sliding distance of 11 m using abrasive papers of 150 grit size under dry friction conditions. Before the wear tests, solution treatment of the 2014 Al alloy was carried out at temperatures of 505 and 520 °C for 1 h in a muffle furnace and then quenched in cold water at 15 °C. Later, the ageing treatment was carried out at 185 °C for 8 h in the furnace. Generally, wear rate due to time increased linearly and linear wear resistance decreased with increasing loads. However, the wear rate was directly proportional to the load up to a critical load of 7 N. After this load, the slope of the curves decreased because the excessive deformation of the worn surface and the instability of the abrasive grains began to increase. When the load on an abrasive grain reaches a critical value, the groove width is about 0.17 of the abrasive grain diameter, and the abrasive grains begin to fail. The wear rate due to time increased slightly as the sliding speed increased in the range 0.09-0.90 m/s. The reason for this is that changes arising from strain rate and friction heating are expected with increasing sliding speeds.

Assessment of thermal spray coatings for wear and abrasion resistance applications

Science.gov (United States)

Karode, Ishaan Nitin

Thermal spray cermet and metallic coatings are extensively used for wear, abrasion and corrosion control in a variety of industries. The first part of the thesis focuses mainly on testing of sand erosion resistance of thermal spray coatings on carbon composites used in the manufacture of helicopter rotor blades. The test set-up employed is a sand blasting machine and is an effort to duplicate the in-flight conditions especially those encountered in hot arid conditions. The technique adopted follows the Department of Defence test method standard. Carbon Composites have excellent stiffness, strength and low weight/density. The strength to weight ratio is high. Hence, these are used in aerospace applications to a large extent. However, the biggest problem encountered with carbon composites is its low abrasion resistance as its surface is very weak. Hence, thermal spray coatings are used to improve the surface properties of CFRP. Zinc bond coats and WC-Co coatings were tested. However, high amount of thermal stresses were developed between the substrate and the coating due to large differences in the CTE's of the both, leading to high mass losses within two minutes and just 130 grams of sand sprayed on to the coatings with the sand blasting machine built; and hence the coatings with CC as a substrate could not qualify for the application. The second part of the thesis focuses on the assessment of different thermal spray coatings used for manufacture of mechanical seals in pumps and analyze the best coating material for the wear resistance application through detail quantification of material loss by block-on-ring test set-up. A machine based on Block-on-ring test set-up following ASTM G77 (Measurement of Adhesive wear resistance of thermal spray coatings) standards was built to duplicate the pump conditions. Thermally sprayed coated materials were tested in different conditions (Load, time, abrasive). WC-Co had the highest wear resistance (lower volume losses) and

Infrared laser-induced chaos and conformational disorder in a model polymer crystal: Melting vs ablation

International Nuclear Information System (INIS)

Sumpter, B.G.; Noid, D.W.; Voth, G.A.; Wunderlich, B.

1990-01-01

Molecular dynamics-based computer simulations are presented for the interaction of one and two infrared (IR) laser beams with a model polymer surface. When a single laser beam system is studied over a wide range of intensities, only melting of the polymer, or melting followed by bond dissociation, is observed for up to 100 picoseconds. In contrast, the two-laser simulation results exhibit a marked difference in the energy absorption behavior of the irradiated polymer which, in turn, results in multiple bond dissociations. The results for the one- and two-laser cases studied can be divided into four different classes of physical behavior: (a) the polymer remains in the solid state; (b) the polymer crystal melts; (c) the polymer ablates, but with significant melting (charring); or (d) the polymer ablates with minimal melting. Damage to the model polymer crystal from absorption of energy from either one or two lasers occurs through a mechanism that involves the competition between the absorption of energy and internal energy redistribution. The rate of energy loss from the absorption site(s) relative to the rate of absorption of energy from the radiation field determines rather the polymer melts or ablates (low absorption rates lead to melting or no change and high rates lead to ablation). A sufficiently large rate of energy absorption is only obtainable through the use of two lasers. Two lasers also significantly decrease the total laser intensity required to cause polymer crystal melting. The differences between the one- and two-laser cases are studied by adapting novel signal/subspace techniques to analyze the dynamical changes in the mode spectrum of the polymer as it melts

Studying the thermal performance of a bipolar radiofrequency ablation with an improved electrode matrix system: In vitro experiments and modelling

International Nuclear Information System (INIS)

Shao, Y.L.; Leo, H.L.; Chua, K.J.

2017-01-01

Highlights: • We made judicious modification to the Penne’s equation in the process of developing our model. We consider the liver to consist of tumor and health tissue. The model has been validated with experimental data. • The proposed electrode system can reduce the tissue volume damage outside the electrodes. The designed building unit with 10 mm inter-electrode distance is the optimal choice to achieve desired ablation zone. • The influence of blood vessel is relatively small for using this electrode system. A spatial distance of 13 mm is deemed as the safe distance between the wall of the central probe and the large vessel. • This proposed electrode system demonstrated higher ablation stability even for tissue regions that are close to blood vessels. The system is better suited for matrix-type RFA. - Abstract: Radiofrequency ablation (RFA) is becoming an effective treatment method for both primary tumors and tumors that have metastasized. Large tumors in difficult anatomic locations can be treated by RFA technologies. However, constant size and regular shape of damage zones cannot be obtained by recent RFA technologies. The aim of this study is to optimize the stability of RFA treatment by employing a newly proposed bipolar electrode system. A hepatic RFA mathematical model is developed by the finite element method approach. The model is validated with the experimental data. This model is then used to verify the reliability and stability of the proposed electrode system. Simulated results showed the cross section of the ablation zone utilizing designed electrode system approximates a square. In addition, the fraction of the necrosed tissue with this electrode pattern turned out to be larger than the fraction with single-probe RFA techniques. This system demonstrated higher ablation stability even for tissue regions that are close to blood vessels. The proposed electrode system is better suited for matrix-type RFA.

Nuclear-chemical methods in a hard tooth tissue abrasion study

International Nuclear Information System (INIS)

Gosman, A.; Spevacek, V.; Konicek, J.; Vopalka, D.; Housova, D.; Dolezalova, L.

1999-01-01

The advanced method consists in implantation-labelling of the thin surface layers of the solid objects, e.g. hard tooth tissue, by atoms of suitable natural or artificial radionuclides. Nuclides from the uranium series were implanted into the surface by using nuclear recoil effect at alpha decay of 226 Ra to 222 Rn, alpha decay of 222 Rn to RaA, alpha decay of RaA to RaB (beta-emitter) and further alpha or beta emitters. With regard to chosen alpha detection and to the half-lives of the radionuclides, there was actually measured the activity of 222 Rn, RaA and RaC' in the thin surface layer. This was followed by the laboratory simulation of the abrasion in the system of 'toothbrush - various suspensions of the tooth-pastes - hard tooth tissue (or material standard - ivory)' in specially designed device - the dentoabrasion meter. The activities of the tissue surface measured before and after abrasion were used for calculations of the relative drop of the surface activity. On this basis the influence of various tooth-pastes containing various abrasive substances was determined. (author)

Toward a comprehensive UV laser ablation modeling of multicomponent materials—A non-equilibrium investigation on titanium carbide

Science.gov (United States)

Ait Oumeziane, Amina; Parisse, Jean-Denis

2018-05-01

Titanium carbide (TiC) coatings of great quality can be produced using nanosecond pulsed laser deposition (PLD). Because the deposition rate and the transfer of the target stoichiometry depend strongly on the laser-target/laser-plasma interaction as well as the composition of the laser induced plume, investigating the ruling fundamental mechanisms behind the material ablation and the plasma evolution in the background environment under PLD conditions is essential. This work, which extends previous investigations dedicated to the study of nanosecond laser ablation of pure target materials, is a first step toward a comprehensive non-equilibrium model of multicomponent ones. A laser-material interaction model coupled to a laser-plasma interaction one is presented. A UV 20 ns KrF (248 nm) laser pulse is considered. Ablation depths, plasma ignition thresholds, and shielding rates have been calculated for a wide range of laser beam fluences. A comparison of TiC behavior with pure titanium material under the same conditions is made. Plasma characteristics such as temperature and composition have been investigated. An overall correlation between the various results is presented.

Air-propelled abrasive grit can damage the perennial weed, quackgrass, Elytrigia repens (L.) Nevski

Science.gov (United States)

New techniques are needed to control quackgrass in organic crops. With greater than or equal to 2 applications of abrasive air-propelled (800 kPa) corncob grit to 15 cm tall quackgrass tillers, regrowth was minimal at 5 weeks after treatment. Abrasive grits may be effective tools to help manage pere...

Radiofrequency Thermal Ablation Heat Energy Transfer in an Ex-Vivo Model.

Science.gov (United States)

Thakur, Shivani; Lavito, Sandi; Grobner, Elizabeth; Grobner, Mark

2017-12-01

Little work has been done to consider the temperature changes and energy transfer that occur in the tissue outside the vein with ultrasound-guided vein ablation therapy. In this experiment, a Ex-Vivo model of the human calf was used to analyze heat transfer and energy degradation in tissue surrounding the vein during endovascular radiofrequency ablation (RFA). A clinical vein ablation protocol was used to determine the tissue temperature distribution in 10 per cent agar gel. Heat energy from the radiofrequency catheter was measured for 140 seconds at fixed points by four thermometer probes placed equidistant radially at 0.0025, 0.005, and 0.01 m away from the RFA catheter. The temperature rose 1.5°C at 0.0025 m, 0.6°C at 0.005 m, and 0.0°C at 0.01 m from the RFA catheter. There was a clinically insignificant heat transfer at the distances evaluated, 1.4 ± 0.2 J/s at 0.0025 m, 0.7 ± 0.3 J/s at 0.0050 m, and 0.3 ± 0.0 J/s at 0.01 m. Heat degradation occurred rapidly: 4.5 ± 0.5 J (at 0.0025 m), 4.0 ± 1.6 J (at 0.0050 m), and 3.9 ± 3.6 J (at 0.01 m). Tumescent anesthesia injected one centimeter around the vein would act as a heat sink to absorb the energy transferred outside the vein to minimize tissue and nerve damage and will help phlebologists strategize options for minimizing damage.

STUDY OF POLISHING AISI 316L WITH STRUCTURED ABRASIVE

Directory of Open Access Journals (Sweden)

François GOOSSENS

2015-05-01

Full Text Available Finishing process like polishing is usually used to obtain high quality mechanical surface characteristics such as texture and roughness. These operations are mainly handmade and need highly trained operators thus limiting their repeatability and profitability. To optimize the industrialization of the polishing process, it is therefore necessary to modelize the process to built efficient parameter database. The aim of this study is to characterise the polishing of 316L stainless steel with structured abrasive belts. The geometric data of the belts are given, and we then propose a model to determine material removal. An experimental test bench is set up to test this model and characterise the polishing process in terms of forces. It produces samples for different polishing conditions. The different polished surfaces are then analyzed thanks to the roughness and the wettability. Using experimental designs, we are able to validate the proposed model and identify the parameters that influence a polishing operation.

Two-body, dry abrasive wear of Fe/Cr/C experimental alloys - relationship between microstructure and mechanical properties

International Nuclear Information System (INIS)

Kwok, C.K.S.

1982-01-01

A systematic study of abrasive wear resistance of Fe/Cr/Mn based alloys has been carried out using a two body pin-on-disc wear machine. Abrasives used were silicon carbide, alumina and quartz. The objective of this study was to evaluate the abrasive wear resistance and to investigate the relationships between microstructure, mechanical properties, and abrasive wear resistance for these experimental alloys. Several commercial alloys were also tested to provide a basis for comparison. The goal of this study was to develop information so as to improve wear resistance of these experimental alloys by means of thermal treatments. Grain-refinement by double heat treatment was carried out in this research

Thermal annealing and ionic abrasion in ZnTe

International Nuclear Information System (INIS)

Bensahel, D.

1975-01-01

Thermal annealing of the ZnTe crystal is studied first in order to obtain information on the aspect of the penetration profile. Ionic abrasion is then investigated to find out whether it produces the same effects as ionic implantation, especially for luminescence [fr

Model-based feasibility assessment and evaluation of prostate hyperthermia with a commercial MR-guided endorectal HIFU ablation array

Science.gov (United States)

Salgaonkar, Vasant A.; Prakash, Punit; Rieke, Viola; Ozhinsky, Eugene; Plata, Juan; Kurhanewicz, John; Hsu, I.-C. Joe; Diederich, Chris J.

2017-03-01

Here, operational modifications to a commercial MR-guided ultrasound phased array designed for prostate ablation (part of ExAblate 2100, InSightec Ltd) are presented for the delivery of protracted mild (40 - 45°C) hyperthermia to large contiguous target volumes in the prostate. This high-intensity focused ultrasound phased array is already in clinical trials for prostate ablation, and can be potentially fast-tracked for clinical hyperthermia treatments. As a part of this preliminary feasibility study, patient-specific numerical simulations were performed using Pennes bioheat model and acoustic field calculations were conducted using the rectangular radiator method for the ExAblate prostate array (2.3 MHz, 2.3×4.0 cm2, ˜1000 channels). Thermal solutions were computed using 3D finite element methods (FEM) implemented using Comsol Multiphysics (Comsol Inc). The patient-specific geometries were created through manual segmentation of anatomical structures from representative patient MRIs and 3D rendering (Mimics 15.01, Materialise) and generation of finite element meshes (3-Matic 7.01, Materialise). Array beamforming was employed and acoustic fields were synthesized (Matlab 2010a, MathWorks) to deliver protracted continuous wave hyperthermia to focal prostate cancer targets identified in the patient-specific models. Constraints on power densities, sonication durations and switching speeds imposed by ExAblate hardware and software were incorporated in the models. Sonication strategies explored during modeling were implemented on the ExAblate prostate array and preliminary experiments were conducted in tissue mimicking phantoms under MR temperature monitoring at 3 T (GE Discovery MR750W). Therapeutic temperatures (40 - 45 °C) could be established conformably in focal cancer volumes in a single prostate quadrant using focused heating patterns and hemi-gland heating was possible using diffused heating patterns (iso-phase or diverging). T>41 °C was calculated in 13

Assessment of mechanical and three-body abrasive wear peculiarity ...

Indian Academy of Sciences (India)

directional fabric reinforcement offers a unique solution for ... showed good performance to the three-body abrasive wear. .... plied by the Pioneer Chemical Company, Delhi, India. ..... Theoretical and measured densities of composites, along.

Wall ablation of heated compound-materials into non-equilibrium discharge plasmas

Science.gov (United States)

Wang, Weizong; Kong, Linghan; Geng, Jinyue; Wei, Fuzhi; Xia, Guangqing

2017-02-01

The discharge properties of the plasma bulk flow near the surface of heated compound-materials strongly affects the kinetic layer parameters modeled and manifested in the Knudsen layer. This paper extends the widely used two-layer kinetic ablation model to the ablation controlled non-equilibrium discharge due to the fact that the local thermodynamic equilibrium (LTE) approximation is often violated as a result of the interaction between the plasma and solid walls. Modifications to the governing set of equations, to account for this effect, are derived and presented by assuming that the temperature of the electrons deviates from that of the heavy particles. The ablation characteristics of one typical material, polytetrafluoroethylene (PTFE) are calculated with this improved model. The internal degrees of freedom as well as the average particle mass and specific heat ratio of the polyatomic vapor, which strongly depends on the temperature, pressure and plasma non-equilibrium degree and plays a crucial role in the accurate determination of the ablation behavior by this model, are also taken into account. Our assessment showed the significance of including such modifications related to the non-equilibrium effect in the study of vaporization of heated compound materials in ablation controlled arcs. Additionally, a two-temperature magneto-hydrodynamic (MHD) model accounting for the thermal non-equilibrium occurring near the wall surface is developed and applied into an ablation-dominated discharge for an electro-thermal chemical launch device. Special attention is paid to the interaction between the non-equilibrium plasma and the solid propellant surface. Both the mass exchange process caused by the wall ablation and plasma species deposition as well as the associated momentum and energy exchange processes are taken into account. A detailed comparison of the results of the non-equilibrium model with those of an equilibrium model is presented. The non-equilibrium results

Ultrasound-guided radiofrequency thermal ablation of normal kidney in a rabbit model: correlation with CT and histopathology

Energy Technology Data Exchange (ETDEWEB)

Kim, Sang Won; Lee, Jeong Min; Kin, Chong Soo; Lee, Sang Hun [College of Medicine, Chonbuk National Univ., Chonju (Korea, Republic of)

2002-01-01

To assess the feasibility and safety of using a cooled-tip electrode to perform percutaneous radiofrequency ablation of kidney tissue in rabbits, and to evaluate the ability of CT to reveal the appearance and extent of tissue necrosis during follow-up after ablation. Using ultrasound guidance, a 17-G cooled-tip electrode was inserted into the right lower portion of the kidney in 26 New Zealand White rabbits. Radiofrequency was applied for 2 mins, and biphasic helical CT scanning was used to assess tissue destruction and the presence or absence of complications immediately after the procedure and at 24 hrs, 2 and 3 days, and 1,2,3,4,5,6 and 7 weeks. The study had three phases: acute (immediately killed : N=10); subacute (killed at 24 hrs (n=3), 2 days (n=3), 3 days (n=1) : N=7); chronic (killed at 1 week (n=4), 2 weeks (n=2), 4 weeks (n=1), 7 weeks (n=1): N=8). After the animals were killed, their kidneys were histopathologically examined and the radiologic and pathologic findings of lesion size and configuration were correlated. In each instance, ultrasound-guided radiofrequency ablations of the lower pole of the kidney were technically successful. Contrast-enhanced biphasic helical CT revealed regions of hypoattenuation devoid of parenchymal enhancement, and these correlated closely with true pathologic lesion size (r=0.884; p>0.05). In subacute and chronic models, CT scanning revealed gradual spontaneous resorption of the ablated lesion and the presence of perilesional calcification. Histopathologically, in the acute phase the ablated lesion showed coagulative necrosis and infiltration of inflammatory cells, and in the chronic phase there was clear cut necrosis of glomeruli, tubules and renal interstitium, with diminishing inflammatory response and peripheral fibrotic tissue formation. Ultrasound-guided renal radiofrequency ablation is technically feasible and safe. In addition, the avascular lesion measured at contrast-enhanced helical CT closely correlated with

Ultrasound-guided radiofrequency thermal ablation of normal kidney in a rabbit model: correlation with CT and histopathology

International Nuclear Information System (INIS)

Kim, Sang Won; Lee, Jeong Min; Kin, Chong Soo; Lee, Sang Hun

2002-01-01

To assess the feasibility and safety of using a cooled-tip electrode to perform percutaneous radiofrequency ablation of kidney tissue in rabbits, and to evaluate the ability of CT to reveal the appearance and extent of tissue necrosis during follow-up after ablation. Using ultrasound guidance, a 17-G cooled-tip electrode was inserted into the right lower portion of the kidney in 26 New Zealand White rabbits. Radiofrequency was applied for 2 mins, and biphasic helical CT scanning was used to assess tissue destruction and the presence or absence of complications immediately after the procedure and at 24 hrs, 2 and 3 days, and 1,2,3,4,5,6 and 7 weeks. The study had three phases: acute (immediately killed : N=10); subacute (killed at 24 hrs (n=3), 2 days (n=3), 3 days (n=1) : N=7); chronic (killed at 1 week (n=4), 2 weeks (n=2), 4 weeks (n=1), 7 weeks (n=1): N=8). After the animals were killed, their kidneys were histopathologically examined and the radiologic and pathologic findings of lesion size and configuration were correlated. In each instance, ultrasound-guided radiofrequency ablations of the lower pole of the kidney were technically successful. Contrast-enhanced biphasic helical CT revealed regions of hypoattenuation devoid of parenchymal enhancement, and these correlated closely with true pathologic lesion size (r=0.884; p>0.05). In subacute and chronic models, CT scanning revealed gradual spontaneous resorption of the ablated lesion and the presence of perilesional calcification. Histopathologically, in the acute phase the ablated lesion showed coagulative necrosis and infiltration of inflammatory cells, and in the chronic phase there was clear cut necrosis of glomeruli, tubules and renal interstitium, with diminishing inflammatory response and peripheral fibrotic tissue formation. Ultrasound-guided renal radiofrequency ablation is technically feasible and safe. In addition, the avascular lesion measured at contrast-enhanced helical CT closely correlated with

Investigation of the wavelength dependence of laser stratigraphy on Cu and Ni coatings using LIBS compared to a pure thermal ablation model

Science.gov (United States)

Paulis, Evgeniya; Pacher, Ulrich; Weimerskirch, Morris J. J.; Nagy, Tristan O.; Kautek, Wolfgang

2017-12-01

In this study, galvanic coatings of Cu and Ni, typically applied in industrial standard routines, were investigated. Ablation experiments were carried out using the first two harmonic wavelengths of a pulsed Nd:YAG laser and the resulting plasma spectra were analysed using a linear Pearson correlation method. For both wavelengths the absorption/ablation behaviour as well as laser-induced breakdown spectroscopy (LIBS) depth profiles were studied varying laser fluences between 4.3-17.2 J/cm^2 at 532 nm and 2.9-11.7 J/cm^2 at 1064 nm. The LIBS-stratigrams were compared with energy-dispersive X-ray spectroscopy of cross-sections. The ablation rates were calculated and compared to theoretical values originating from a thermal ablation model. Generally, higher ablation rates were obtained with 532 nm light for both materials. The light-plasma interaction is suggested as possible cause of the lower ablation rates in the infrared regime. Neither clear evidence of the pure thermal ablation, nor correlation with optical properties of investigated materials was obtained.

Radiofrequency Ablation of Lung Tumors

Science.gov (United States)

... News Physician Resources Professions Site Index A-Z Radiofrequency Ablation (RFA) / Microwave Ablation (MWA) of Lung Tumors ... and Microwave Ablation of Lung Tumors? What are Radiofrequency and Microwave Ablation of Lung Tumors? Radiofrequency ablation, ...

Turning of wood plastic composites by water jet and abrasive water jet

OpenAIRE

Hutyrová, Z.; Ščučka, J. (Jiří); Hloch, S. (Sergej); Hlaváček, P. (Petr); Zeleňák, M. (Michal)

2015-01-01

The paper deals with the verification of suitability of water jet and abrasive water jet application for the disintegration of rotating samples of wood plastic composites (WPCs) with diameter d=36 mm. The influence of selected technological factors (traverse speed of cutting head v [mm/ min] and size of abrasive particles [MESH]) on the topography of resulting surfaces has in particular been studied. Surface topography and quality have been assessed using the methods of optical and co...

Monitoring of the Abrasion Processes (by the Example of Alakol Lake, Republic of Kazakhstan)

Science.gov (United States)

Abitbayeva, Ainagul; Valeyev, Adilet; Yegemberdiyeva, Kamshat; Assylbekova, Aizhan; Ryskeldieva, Aizhan

2016-01-01

The purpose of the study is to analyze the abrasion processes in the regions of dynamically changing Alakol lake shores. Using the field method, methods of positioning by the GPS receiver and interpretation of remote sensing data, the authors determined that abrasion processes actively contributed to the formation the modern landscape, causing the…

Gingival abrasion and recession in manual and oscillating-rotating power brush users.

Science.gov (United States)

Rosema, N A M; Adam, R; Grender, J M; Van der Sluijs, E; Supranoto, S C; Van der Weijden, G A

2014-11-01

To assess gingival recession (GR) in manual and power toothbrush users and evaluate the relationship between GR and gingival abrasion scores (GA). This was an observational (cross-sectional), single-centre, examiner-blind study involving a single-brushing exercise, with 181 young adult participants: 90 manual brush users and 91 oscillating-rotating power brush users. Participants were assessed for GR and GA as primary response variables. Secondary response variables were the level of gingival inflammation, plaque score reduction and brushing duration. Pearson correlation was used to describe the relationship between number of recession sites and number of abrasions. Prebrushing (baseline) and post-brushing GA and plaque scores were assessed and differences analysed using paired tests. Two-sample t-test was used to analyse group differences; ancova was used for analyses of post-brushing changes with baseline as covariate. Overall, 97.8% of the study population had at least one site of ≥1 mm of gingival recession. For the manual group, this percentage was 98.9%, and for the power group, this percentage was 96.7% (P = 0.621). Post-brushing, the power group showed a significantly smaller GA increase than the manual group (P = 0.004); however, there was no significant correlation between number of recession sites and number of abrasions for either group (P ≥ 0.327). Little gingival recession was observed in either toothbrush user group; the observed GR levels were comparable. Lower post-brushing gingival abrasion levels were seen in the power group. There was no correlation between gingival abrasion as a result of brushing and the observed gingival recession following use of either toothbrush. © 2014 The Authors International Journal of Dental Hygiene Published by John Wiley & Sons Ltd.

Importance of catheter contact force during irrigated radiofrequency ablation: evaluation in a porcine ex vivo model using a force-sensing catheter.

Science.gov (United States)

Thiagalingam, Aravinda; D'Avila, Andre; Foley, Lori; Guerrero, J Luis; Lambert, Hendrik; Leo, Giovanni; Ruskin, Jeremy N; Reddy, Vivek Y

2010-07-01

Ablation electrode-tissue contact has been shown to be an important determinant of lesion size and safety during nonirrigated ablation but little data are available during irrigated ablation. We aimed to determine the importance of contact force during irrigated-tip ablation. Freshly excised hearts from 11 male pigs were perfused and superfused using fresh, heparinized, oxygenated swine blood in an ex vivo model. One-minute ablations were placed using one of 3 different power control strategies (impedance control-15 Omega target impedance drop, and 20 W or 30 W fixed power) and 3 different contact forces (2 g, 20 g, and 60 g) to give a grid of 9 ablation groups. The force sensing catheter (Tacticath, Endosense SA) was irrigated at 17 mL/min for all of the ablations. Of a total 101 ablations, no thrombus formation was noted but popping was seen in 17 lesions. The lesion depth and incidence of pops was 5.0 +/- 1.3 mm /0%, 5.0 +/- 1.6 mm /10% and 6.7 +/- 2.5 mm /45% for the 15 Omega, 20 W, and 30 W groups (P force: 9.7 +/- 9.9 Omega, 22.3 +/- 11.0 Omega, and 41.7 +/- 22.1 Omega, respectively, for the 2 g, 20 g, and 60 g groups (Pearson's r = 0.65, P force has an important impact on both ablation lesion size and the incidence of pops.

Assessment of Rail Seat Abrasion Patterns and Environment

Science.gov (United States)

2012-05-01

Rail seat abrasion (RSA) of concrete ties is manifested by the loss of material under the rail seat area and, in extreme cases, results in loss of rail clip holding power, reverse rail cant, and gauge widening. RSA was measured in several curves on t...

Simulation of ablation and plume dynamics under femtosecond double-pulse laser irradiation of aluminum: Comparison of atomistic and continual approaches

Energy Technology Data Exchange (ETDEWEB)

Fokin, Vladimir B.; Povarnitsyn, Mikhail E., E-mail: povar@ihed.ras; Levashov, Pavel R.

2017-02-28

Highlights: • We model double-pulse laser ablation of aluminum using microscopic and macroscopic approaches. • Both methods show decrease in depth of crater with increasing delay between pulses. • Both methods reveal the plume temperature growth with the increasing delay. • Good agreement between results is a step towards the development of combined model. - Abstract: We elaborated two numerical methods, two-temperature hydrodynamics and hybrid two-temperature molecular dynamics, which take into account basic mechanisms of a metal target response to ultrashort laser irradiation. The model used for the description of the electronic subsystem is identical for both approaches, while the ionic part is defined by an equation of state in hydrodynamics and by an interatomic potential in molecular dynamics. Since the phase diagram of the equation of state and corresponding potential match reasonably well, the dynamics of laser ablation obtained by both methods is quite similar. This correspondence can be considered as a first step towards the development of a self-consistent combined model. Two important processes are highlighted in simulations of double-pulse ablation: (1) the crater depth decrease as a result of recoil flux formation in the nascent plume when the delay between the pulses increases; (2) the plume reheating by the second pulse that gives rise to two- three-fold growth of the electron temperature with the delay varying from 0 to 200 ps.

Atmospheric pressure arc discharge with ablating graphite anode

International Nuclear Information System (INIS)

Nemchinsky, V A; Raitses, Y

2015-01-01

The anodic carbon arc discharge is used to produce carbon nanoparticles. Recent experiments with the carbon arc at atmospheric pressure helium demonstrated the enhanced ablation rate for narrow graphite anodes resulting in high deposition rates of carbonaceous products on the copper cathode (Fetterman et al 2008 Carbon 46 1322–6). The proposed model explains these results with interconnected steady-state models of the cathode and the anode processes. When considering cathode functioning, the model predicts circulation of the particles in the near-cathode region: evaporation of the cathode material, ionization of evaporated atoms and molecules in the near-cathode plasma, return of the resulting ions to the cathode, surface recombination of ions and electrons followed again by cathode evaporation etc. In the case of the low anode ablation rate, the ion acceleration in the cathode sheath provides the major cathode heating mechanism. In the case of an intensive anode ablation, an additional cathode heating is due to latent fusion heat of the atomic species evaporated from the anode and depositing at the cathode. Using the experimental arc voltage as the only input discharge parameter, the model allows us to calculate the anode ablation rate. A comparison of the results of calculations with the available experimental data shows reasonable agreement. (paper)

Atmospheric pressure arc discharge with ablating graphite anode

Science.gov (United States)

Nemchinsky, V. A.; Raitses, Y.

2015-06-01

The anodic carbon arc discharge is used to produce carbon nanoparticles. Recent experiments with the carbon arc at atmospheric pressure helium demonstrated the enhanced ablation rate for narrow graphite anodes resulting in high deposition rates of carbonaceous products on the copper cathode (Fetterman et al 2008 Carbon 46 1322-6). The proposed model explains these results with interconnected steady-state models of the cathode and the anode processes. When considering cathode functioning, the model predicts circulation of the particles in the near-cathode region: evaporation of the cathode material, ionization of evaporated atoms and molecules in the near-cathode plasma, return of the resulting ions to the cathode, surface recombination of ions and electrons followed again by cathode evaporation etc. In the case of the low anode ablation rate, the ion acceleration in the cathode sheath provides the major cathode heating mechanism. In the case of an intensive anode ablation, an additional cathode heating is due to latent fusion heat of the atomic species evaporated from the anode and depositing at the cathode. Using the experimental arc voltage as the only input discharge parameter, the model allows us to calculate the anode ablation rate. A comparison of the results of calculations with the available experimental data shows reasonable agreement.

Tribological properties of multifunctional coatings with Shape Memory Effect in abrasive wear

Science.gov (United States)

Blednova, Zh. M.; Dmitrenko, D. V.; Balaev, E. U. O.

2018-01-01

The article gives research results of the abrasive wear process on samples made of Steel 1045, U10 and with applied composite surface layer "Nickel-Multicomponent material with Shape Memory Effect (SME) based on TiNi". For the tests we have chosen TiNiZr, which is in the martensite state and TiNiHfCu, which is in the austenitic state at the test temperature. The formation of the surface layer was carried out by high-speed oxygen-fuel deposition in a protective atmosphere of argon. In the wear test, Al2O3 corundum powder was used as an abrasive. It is shown that the wear rate of samples with a composite surface layer of multicomponent materials with SME is significantly reduced in comparison with the base, which is explained by reversible phase transformations of the surface layer with SME. After carrying out the additional surface plastic deformation (SPD), the resistance of the laminated composition to abrasion wear has greatly enhanced, due to the reinforcing effect of the SPD. It is recommended for products working in conditions of abrasive wear and high temperatures to use the complex formation technology of the surface composition "steel-nickel-material with high-temperature SME", including preparation of the substrate surface and the deposited material, high-speed spraying in the protective atmosphere of argon, followed by SPD.

The Antineoplastic Activity of Photothermal Ablative Therapy with Targeted Gold Nanorods in an Orthotopic Urinary Bladder Cancer Model.

Science.gov (United States)

Yang, Xiaoping; Su, Lih-Jen; La Rosa, Francisco G; Smith, Elizabeth Erin; Schlaepfer, Isabel R; Cho, Suehyun K; Kavanagh, Brian; Park, Wounjhang; Flaig, Thomas W

2017-07-27

Gold nanoparticles treated with near infrared (NIR) light can be heated preferentially, allowing for thermal ablation of targeted cells. The use of novel intravesical nanoparticle-directed therapy in conjunction with laser irradiation via a fiber optic cystoscope, represents a potential ablative treatment approach in patients with superficial bladder cancer. To examine the thermal ablative effect of epidermal growth factor receptor (EGFR)-directed gold nanorods irradiated with NIR light in an orthotopic urinary bladder cancer model. Gold nanorods linked to an anti-EGFR antibody (Conjugated gold NanoRods - CNR) were instilled into the bladder cavity of an orthotopic murine xenograft model with T24 bladder cancer cells expressing luciferase. NIR light was externally administered via an 808 nm diode laser. This treatment was repeated weekly for 4 weeks. The anti-cancer effect was monitored by an in vivo imaging system in a non-invasive manner, which was the primary outcome of our study. The optimal approach for an individual treatment was 2.1 W/cm 2 laser power for 30 seconds. Using this in vivo model, NIR light combined with CNR demonstrated a statistically significant reduction in tumor-associated bioluminescent activity ( n  = 16) compared to mice treated with laser alone ( n  = 14) at the end of the study ( p  = 0.035). Furthermore, the CNR+NIR light treatment significantly abrogated bioluminescence signals over a 6-week observation period, compared to pre-treatment levels ( p  = 0.045). Photothermal tumor ablation with EGFR-directed gold nanorods and NIR light proved effective and well tolerated in a murine in vivo model of urinary bladder cancer.

Resistance to abrasion of extrinsic porcelain esthetic characterization techniques.

Science.gov (United States)

Chi, Woo J; Browning, William; Looney, Stephen; Mackert, J Rodway; Windhorn, Richard J; Rueggeberg, Frederick

2017-01-01

A novel esthetic porcelain characterization technique involves mixing an appropriate amount of ceramic colorants with clear, low-fusing porcelain (LFP), applying the mixture on the external surfaces, and firing the combined components onto the surface of restorations in a porcelain oven. This method may provide better esthetic qualities and toothbrush abrasion resistance compared to the conventional techniques of applying color-corrective porcelain colorants alone, or applying a clear glaze layer over the colorants. However, there is no scientific literature to support this claim. This research evaluated toothbrush abrasion resistance of a novel porcelain esthetic characterization technique by subjecting specimens to various durations of simulated toothbrush abrasion. The results were compared to those obtained using the conventional characterization techniques of colorant application only or colorant followed by placement of a clear over-glaze. Four experimental groups, all of which were a leucite reinforced ceramic of E TC1 (Vita A1) shade, were prepared and fired in a porcelain oven according to the manufacturer's instructions. Group S (stain only) was characterized by application of surface colorants to provide a definitive shade of Vita A3.5. Group GS (glaze over stain) was characterized by application of a layer of glaze over the existing colorant layer as used for Group S. Group SL (stain+LFP) was characterized by application of a mixture of colorants and clear low-fusing add-on porcelain to provide a definitive shade of Vita A3.5. Group C (Control) was used as a control without any surface characterization. The 4 groups were subjected to mechanical toothbrushing using a 1:1 water-to-toothpaste solution for a simulated duration of 32 years of clinical use. The amount of wear was measured at time intervals simulating every 4 years of toothbrushing. These parameters were evaluated longitudinally for all groups as well as compared at similar time points among

Abrasive wear behaviour of bio-active glass ceramics containing ...

Indian Academy of Sciences (India)

Unknown

Technical Education Faculty, Mersin University, 33480 Tarsus, Turkey. MS received 18 October 2005; revised 22 March 2006. Abstract. In this study, abrasive ... process were used to produce bio-active ceramics. Fracture toughness of studied ...

New decontamination techniques: chemical gels, electropolishing and abrasives

International Nuclear Information System (INIS)

Brunel, G.; Gauchon, J.P.; Kervegant, Y.; Josso, F.

1991-01-01

The decommissioning of nuclear installations requires decontamination techniques that are efficient, simple to apply and producing a small amount of wastes, which are easy to process. With a view to this, three decontamination methods, which appear to be particularly suited to decommissioning, have been studied. These three methods are: - spraying of gels carrying chemical decontaminating agents, - electropolishing with a swab device, - abrasives blasting. After parametric tests on non-radioactive and active samples, the industrial application of these methods in the dismantling of installations was studied. These industrial applications concern: - decontamination of pieces coming from the German BWR ISAR by immersion and gel spraying, - decontamination, mainly by gel spraying, and dismantling of the BRENNILIS bituminisation plant, - decontamination of part of the cooling circuit of the graphite gas reactor G2 by gel spraying, - decontamination of a component of the FBR SuperPhenix, using dry abrasives blasting. During the first three applications, generated secondary wastes volume and form were determined. 33 tabs., 16 figs., 12 refs

Effects of magnetic resonance-guided high-intensity focused ultrasound ablation on bone mechanical properties and modeling.

Science.gov (United States)

Yeo, Sin Yuin; Arias Moreno, Andrés J; van Rietbergen, Bert; Ter Hoeve, Natalie D; van Diest, Paul J; Grüll, Holger

2015-01-01

Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) is a promising technique for palliative treatment of bone pain. In this study, the effects of MR-HIFU ablation on bone mechanics and modeling were investigated. A total of 12 healthy rat femurs were ablated using 10 W for 46 ± 4 s per sonication with 4 sonications for each femur. At 7 days after treatments, all animals underwent MR and single photon emission computed tomography/computed tomography (SPECT/CT) imaging. Then, six animals were euthanized. At 1 month following ablations, the remaining six animals were scanned again with MR and SPECT/CT prior to euthanization. Thereafter, both the HIFU-treated and contralateral control bones of three animals from each time interval were processed for histology, whereas the remaining bones were subjected to micro-CT (μCT), three-point bending tests, and micro-finite element (micro-FE) analyses. At 7 days after HIFU ablations, edema formation around the treated bones coupled with bone marrow and cortical bone necrosis was observed on MRI and histological images. SPECT/CT and μCT images revealed presence of bone modeling through an increased uptake of (99m)Tc-MDP and formation of woven bone, respectively. At 31 days after ablations, as illustrated by imaging and histology, healing of the treated bone and the surrounding soft tissue was noted, marked by decreased in amount of tissue damage, formation of scar tissue, and sub-periosteal reaction. The results of three-point bending tests showed no significant differences in elastic stiffness, ultimate load, and yield load between the HIFU-treated and contralateral control bones at 7 days and 1 month after treatments. Similarly, the elastic stiffness and Young's moduli determined by micro-FE analyses at both time intervals were not statistically different. Multimodality imaging and histological data illustrated the presence of HIFU-induced bone damage at the cellular level, which activated the

Percutaneous radiofrequency ablation of lung tumors in a large animal model.

Science.gov (United States)

Ahrar, Kamran; Price, Roger E; Wallace, Michael J; Madoff, David C; Gupta, Sanjay; Morello, Frank A; Wright, Kenneth C

2003-08-01

Percutaneous radiofrequency ablation (RFA) is accepted therapy for liver tumors in the appropriate clinical setting, but its use in lung neoplasms remains investigational. We undertook this study to evaluate the feasibility and immediate effectiveness of RFA for treatment of both solitary pulmonary nodules and clusters of lung tumors in a large animal model. Percutaneous RFA of 14 lung tumors in five dogs was performed under CT guidance. Animals were euthanatized 8-48 hours after the procedure. The lungs and adjacent structures were harvested for gross and histopathologic evaluation. Five solitary pulmonary nodules (range, 17-26 mm) and three clusters of three nodules each (range, 7-17 mm per nodule) were treated with RFA. All ablations were technically successful. Perilesional ground-glass opacity and small asymptomatic pneumothoraces (n = 4) were visualized during the RFA sessions. One dog developed a large pneumothorax treated with tube thoracostomy but was euthanatized 8 hours post-RFA for persistent pneumothorax and continued breathing difficulty. Follow-up CT 48 hours post-RFA revealed opacification of the whole lung segment. Gross and histopathologic evaluation showed complete thermal coagulation necrosis of all treated lesions without evidence of any viable tumor. The region of thermal coagulation necrosis typically extended to the lung surface. Small regions of pulmonary hemorrhage and congestion often surrounded the areas of coagulation necrosis. RFA can be used to treat both solitary pulmonary nodules and clusters of tumor nodules in the canine lung tumor model. This model may be useful for development of specific RFA protocols for human lung tumors.

Photomechanical model of tooth enamel ablation by Er-laser radiation

Science.gov (United States)

Belikov, A. V.; Shatilova, K. V.; Skrypnik, A. V.; Vostryakov, R. G.; Maykapar, N. O.

2012-03-01

The photomechanical model of ablation of human tooth enamel is described in this work. It takes into account the structural peculiarities of enamel: free water in the enamel pores or cracks. We consider the photomechanical destruction of the enamel rods of hydroxyapatite by the pressure of water contained in the enamel pores and heated by laser radiation. This model takes into account attenuation by the Lambert-Beer law when radiation passes through the tissue and the fact that the tissue removal occurs when a unit volume of water was heated to the critical temperature. Decreasing logarithmic dependence of the enamel removal efficiency on the energy density was obtained as a result of the calculations. The shape of this function follows the shape of the experimental curve.

Micro-Abrasion Wear Resistance of Borided 316L Stainless Steel and AISI 1018 Steel

Science.gov (United States)

Reséndiz-Calderon, C. D.; Rodríguez-Castro, G. A.; Meneses-Amador, A.; Campos-Silva, I. E.; Andraca-Adame, J.; Palomar-Pardavé, M. E.; Gallardo-Hernández, E. A.

2017-11-01

The 316L stainless steel has high corrosion resistance but low tribological performance. In different industrial sectors (biomedical, chemical, petrochemical, and nuclear engineering), improvement upon wear resistance of 316L stainless steel components using accessible and inexpensive methods is critical. The AISI 1018 steel is widely used in industry, but its tribological performance is not the best among steels. Therefore, in this study the behavior of the borided 316L stainless steel and 1018 steel is evaluated under micro-abrasion wear. The boriding was carried out at 1223 K over 6 h of exposure time, resulting in a biphase layer composed of FeB/Fe2B phases. In order to evaluate Fe2B phase with no influence from FeB phase, AISI 1018 steel samples were borided at 1273 K for over 20 min and then diffusion annealed at 1273 K over 2 h to obtain a Fe2B mono-phase layer. Micro-abrasion wear resistance was evaluated by a commercial micro-abrasion testing rig using a mix of F-1200 SiC particles with deionized water as abrasive slurry. The obtained wear rates for FeB and Fe2B phases and for the 316L stainless steel were compared. Wear resistance of 316L stainless steel increases after boriding. The wear mechanisms for both phases and for the stainless steel were identified. Also, transient conditions for rolling and grooving abrasion were determined for the FeB and Fe2B phases.

Ultraviolet versus infrared: Effects of ablation laser wavelength on the expansion of laser-induced plasma into one-atmosphere argon gas

International Nuclear Information System (INIS)

Ma Qianli; Motto-Ros, Vincent; Laye, Fabrice; Yu Jin; Lei Wenqi; Bai Xueshi; Zheng Lijuan; Zeng Heping

2012-01-01

Laser-induced plasma from an aluminum target in one-atmosphere argon background has been investigated with ablation using nanosecond ultraviolet (UV: 355 nm) or infrared (IR: 1064 nm) laser pulses. Time- and space-resolved emission spectroscopy was used as a diagnostics tool to have access to the plasma parameters during its propagation into the background, such as optical emission intensity, electron density, and temperature. The specific feature of nanosecond laser ablation is that the pulse duration is significantly longer than the initiation time of the plasma. Laser-supported absorption wave due to post-ablation absorption of the laser radiation by the vapor plume and the shocked background gas plays a dominant role in the propagation and subsequently the behavior of the plasma. We demonstrate that the difference in absorption rate between UV and IR radiations leads to different propagation behaviors of the plasma produced with these radiations. The consequence is that higher electron density and temperature are observed for UV ablation. While for IR ablation, the plasma is found with lower electron density and temperature in a larger and more homogenous axial profile. The difference is also that for UV ablation, the background gas is principally evacuated by the expansion of the vapor plume as predicted by the standard piston model. While for IR ablation, the background gas is effectively mixed to the ejected vapor at least hundreds of nanoseconds after the initiation of the plasma. Our observations suggest a description by laser-supported combustion wave for the propagation of the plasma produced by UV laser, while that by laser-supported detonation wave for the propagation of the plasma produced by IR laser. Finally, practical consequences of specific expansion behavior for UV or IR ablation are discussed in terms of analytical performance promised by corresponding plasmas for application with laser-induced breakdown spectroscopy.

Topographical anomaly on surfaces created by abrasive waterjet

Czech Academy of Sciences Publication Activity Database

Hloch, S.; Valíček, Jan

2012-01-01

Roč. 59, 5-8 (2012), s. 593-604 ISSN 0268-3768 Institutional research plan: CEZ:AV0Z30860518 Keywords : abrasive waterjet * initial zone * surface topography Subject RIV: JQ - Machines ; Tools Impact factor: 1.205, year: 2012 http://www.springerlink.com/content/5701144k76v02372

The use of abrasive polishing and laser processing for developing polyurethane surfaces for controlling fibroblast cell behaviour

Energy Technology Data Exchange (ETDEWEB)

Irving, Michael; Murphy, Mark F; Lilley, Francis; French, Paul W; Burton, David R [General Engineering Research Institute, Liverpool John Moores University, Liverpool, L3 3AF (United Kingdom); Dixon, Simon [Biomer Technology LTD, 10 Seymour Court, Tudor Road, Manor Park, Runcorn, Cheshire, WA7 1SY (United Kingdom); Sharp, Martin C [General Engineering Research Institute, Liverpool John Moores University, Liverpool, L3 3AF (United Kingdom)

2017-02-01

Studies have shown that surfaces having micro and nano-scale features can be used to control cell behaviours including; cell proliferation, migration and adhesion. The aim of this work was to compare the use of laser processing and abrasive polishing to develop micro/nano-patterned polyurethane substrates for controlling fibroblast cell adhesion, migration and proliferation. Laser processing in a directional manner resulted in polyurethane surfaces having a ploughed field effect with micron-scale features. In contrast, abrasive polishing in a directional and random manner resulted in polyurethane surfaces having sub-micron scale features orientated in a linear or random manner. Results show that when compared with flat (non-patterned) polymer, both the laser processed and abrasive polished surface having randomly organised features, promoted significantly greater cell adhesion, while also enhancing cell proliferation after 72 h. In contrast, the abrasive polished surface having linear features did not enhance cell adhesion or proliferation when compared to the flat surface. For cell migration, the cells growing on the laser processed and abrasively polished random surface showed decreased levels of migration when compared to the flat surface. This study shows that both abrasive polishing and laser processing can be used to produce surfaces having features on the nano-scale and micron-scale, respectively. Surfaces produced using both techniques can be used to promote fibroblast cell adhesion and proliferation. Thus both methods offer a viable alternative to using lithographic techniques for developing patterned surfaces. In particular, abrasive polishing is an attractive method due to it being a simple, rapid and inexpensive method that can be used to produce surfaces having features on a comparable scale to more expensive, multi-step methods. - Highlights: • Abrasive polishing can generate nano-scratches on stainless steel to cast polymer films for cell

The use of abrasive polishing and laser processing for developing polyurethane surfaces for controlling fibroblast cell behaviour

International Nuclear Information System (INIS)

Irving, Michael; Murphy, Mark F; Lilley, Francis; French, Paul W; Burton, David R; Dixon, Simon; Sharp, Martin C

2017-01-01

Studies have shown that surfaces having micro and nano-scale features can be used to control cell behaviours including; cell proliferation, migration and adhesion. The aim of this work was to compare the use of laser processing and abrasive polishing to develop micro/nano-patterned polyurethane substrates for controlling fibroblast cell adhesion, migration and proliferation. Laser processing in a directional manner resulted in polyurethane surfaces having a ploughed field effect with micron-scale features. In contrast, abrasive polishing in a directional and random manner resulted in polyurethane surfaces having sub-micron scale features orientated in a linear or random manner. Results show that when compared with flat (non-patterned) polymer, both the laser processed and abrasive polished surface having randomly organised features, promoted significantly greater cell adhesion, while also enhancing cell proliferation after 72 h. In contrast, the abrasive polished surface having linear features did not enhance cell adhesion or proliferation when compared to the flat surface. For cell migration, the cells growing on the laser processed and abrasively polished random surface showed decreased levels of migration when compared to the flat surface. This study shows that both abrasive polishing and laser processing can be used to produce surfaces having features on the nano-scale and micron-scale, respectively. Surfaces produced using both techniques can be used to promote fibroblast cell adhesion and proliferation. Thus both methods offer a viable alternative to using lithographic techniques for developing patterned surfaces. In particular, abrasive polishing is an attractive method due to it being a simple, rapid and inexpensive method that can be used to produce surfaces having features on a comparable scale to more expensive, multi-step methods. - Highlights: • Abrasive polishing can generate nano-scratches on stainless steel to cast polymer films for cell

Pacemaker implantation after catheter ablation for atrial fibrillation.

Science.gov (United States)

Deshmukh, Abhishek J; Yao, Xiaoxi; Schilz, Stephanie; Van Houten, Holly; Sangaralingham, Lindsey R; Asirvatham, Samuel J; Friedman, Paul A; Packer, Douglas L; Noseworthy, Peter A

2016-01-01

Sinus node dysfunction requiring pacemaker implantation is commonly associated with atrial fibrillation (AF), but may not be clinically apparent until restoration of sinus rhythm with ablation or cardioversion. We sought to determine frequency, time course, and predictors for pacemaker implantation after catheter ablation, and to compare the overall rates to a matched cardioversion cohort. We conducted a retrospective analysis using a large US commercial insurance database and identified 12,158 AF patients who underwent catheter ablation between January 1, 2005 and December 31, 2012. Over an average of 2.4 years of follow-up, 5.6 % of the patients underwent pacemaker implantation. Using the Cox proportional hazards models, we found that risk of risks of pacemaker implantation was associated with older age (50-64 and ≥65 versus pacemaker implantation between ablation patients and propensity score (PS)-matched cardioversion groups (3.5 versus. 4.1 % at 1 year and 8.8 versus 8.3 % at 5 years). Overall, pacemaker implantation occurs in about 1/28 patients within 1 year of catheter ablation. The overall implantation rate decreased between 2005 and 2012. Furthermore, the risk after ablation is similar to cardioversion, suggesting that patients require pacing due to a common underlying electrophysiologic substrate, rather than the ablation itself.

Determination of Physical Properties of Carbon Materials by Results of Ablative Experiments Con-ducted in the Jets of Gas Dynamic Units

Directory of Open Access Journals (Sweden)

V. V. Gorsky

2015-01-01

Full Text Available The process of hypersonic vehicles’ movement in the dense layers of the atmosphere is accompanied by the considerable combustion of heat shield, which effects on the aerodynamic, mass-inertial and centering characteristics of the product.For correct calculation of model's movement parameters it is necessary:* Using the theoretical and computation methods for determining ablative characteristics of heat-protective materials;* Taking into account all the basic physical and chemical processes, involved in their ablation, using the above mentioned methods;* Testing these techniques in the wide range of experimental data. This physic-mathematical model of carbon materials (CM aerothermochemical destruction is based on using the following:* Arrhenius equations to calculate carbon kinetic oxidation;* Langmuir-Knudsen formula to calculate the velocity of non-equilibrium carbon’s sublimation;* Carbon erosion law represented as a unique dependence of this process velocity on the gas pressure on the wall.Mathematical description of all major processes included in this formulation of the problem, contains a number of "free" parameters that can be determined only on the basis of comparison of theoretical and experimental data according to total ablation characteristics of these materials.This comparison was performed in the article applicable to the tests conditions of modern CM in the stream of electric arc plant and in combustion products of liquid-propellant rocket engines.As the result, the data of kinetic of carbon oxidation by atomic oxygen at sublimation mode of material ablation were obtained for the first time. Carbon erosion law under high pressure was established for the first time.The new approach to processing of ablation experiments is enunciated. Using this approach allows to turn this experiments for CM from comparative tests into the tests to determine ablation properties of thermal protection. Moreover, it enables us also to use the

Laser ablation principles and applications

CERN Document Server

1994-01-01

Laser Ablation provides a broad picture of the current understanding of laser ablation and its many applications, from the views of key contributors to the field. Discussed are in detail the electronic processes in laser ablation of semiconductors and insulators, the post-ionization of laser-desorbed biomolecules, Fourier-transform mass spectroscopy, the interaction of laser radiation with organic polymers, laser ablation and optical surface damage, laser desorption/ablation with laser detection, and laser ablation of superconducting thin films.

Strong feedbacks between hillslope sediment production and channel incision by saltation-abrasion

Science.gov (United States)

Lundbek Egholm, David; Faurschou Knudsen, Mads; Sandiford, Mike

2013-04-01

While it is well understood that rivers erode mountain ranges by incising the bedrock and by transporting sediments away from the ranges, the basic physical mechanisms that drive long-term bedrock erosion and control the lifespan of mountain ranges remain uncertain. A particularly challenging paradox is reconciling the dichotomy associated with the high incision rates observed in active mountain belts, and the long-term (108 years) preservation of significant topographic reliefs in inactive orogenic belts (e.g. von Blankenburg, 2005). We have performed three-dimensional computational experiments with a landscape evolution model that couples bedrock landslides and sediment flux-dependent river erosion by saltation-abrasion (Sklar & Dietrich, 2004). The coupled model experiments show strong feedbacks between the channel erosion and the hillslope delivery of sediments. The feedbacks point to hillslope sediment production rate as the main control on channel erosion rates where saltation-abrasion dominates over other fluvial erosion processes. Our models results thus highlight the importance of hillslope sediment production controlled by climate and tectonic activity for scaling erosion rates in fluvial systems. Because of variations in landslide frequency, the feedbacks make tectonic activity a primary driver of fluvial erosion and help clarifying the long-standing paradox associated with the persistence of significant relief in old orogenic belts, up to several hundred-million-years after tectonic activity has effectively ceased. References F. von Blankenburg. The control mechanisms of erosion and weathering at basin scale from cosmogenic nuclides in river sediment. Earth Planet. Sci. Lett. 237, 462-479 (2005). L. S. Sklar, W. E. Dietrich. A mechanistic model for river incision into bedrock by saltating bed load. Water Resour. Res. 40, W06301 (2004).

Hydro-abrasive erosion of hydraulic turbines caused by sediment - a century of research and development

Science.gov (United States)

Felix, D.; Albayrak, I.; Abgottspon, A.; Boes, R. M.

2016-11-01

Hydro-abrasive erosion of hydraulic turbines is an economically important issue due to maintenance costs and production losses, in particular at high- and medium-head run-of- river hydropower plants (HPPs) on sediment laden rivers. In this paper, research and development in this field over the last century are reviewed. Facilities for sediment exclusion, typically sand traps, as well as turbine design and materials have been improved considerably. Since the 1980s, hard-coatings have been applied on Francis and Pelton turbine parts of erosion-prone HPPs and became state-of-the-art. These measures have led to increased times between overhauls and smaller efficiency reductions. Analytical, laboratory and field investigations have contributed to a better processes understanding and quantification of sediment-related effects on turbines. More recently, progress has been made in numerical modelling of turbine erosion. To calibrate, validate and further develop prediction models, more measurements from both physical model tests in laboratories and real-scale data from HPPs are required. Significant improvements to mitigate hydro-abrasive erosion have been achieved so far and development is ongoing. A good collaboration between turbine manufacturers, HPP operators, measuring equipment suppliers, engineering consultants, and research institutes is required. This contributes to the energy- and cost-efficient use of the worldwide hydropower potential.

Ablative thermal protection systems

International Nuclear Information System (INIS)

Vaniman, J.; Fisher, R.; Wojciechowski, C.; Dean, W.

1983-01-01

The procedures used to establish the TPS (thermal protection system) design of the SRB (solid rocket booster) element of the Space Shuttle vehicle are discussed. A final evaluation of the adequacy of this design will be made from data obtained from the first five Shuttle flights. Temperature sensors installed at selected locations on the SRB structure covered by the TPS give information as a function of time throughout the flight. Anomalies are to be investigated and computer design thermal models adjusted if required. In addition, the actual TPS ablator material loss is to be measured after each flight and compared with analytically determined losses. The analytical methods of predicting ablator performance are surveyed. 5 references

Inertial effects in laser-driven ablation

International Nuclear Information System (INIS)

Harrach, R.J.; Szeoke, A.; Howard, W.M.

1983-01-01

The gasdynamic partial differential equations (PDE's) governing the motion of an ablatively accelerated target (rocket) contain an inertial force term that arises from acceleration of the reference frame in which the PDE's are written. We give a simple, intuitive description of this effect, and estimate its magnitude and parametric dependences by means of approximate analytical formulas inferred from our computer hydrocode calculations. Often this inertial term is negligible, but for problems in the areas of laser fusion and laser equation of state studies we find that it can substantially reduce the attainable hydrodynamic efficiency of acceleration and implosion

Increase in Volume of Ablation Zones during Follow-up Is Highly Suggestive of Ablation Site Recurrence in Colorectal Liver Metastases Treated with Radiofrequency Ablation

NARCIS (Netherlands)

Kele, Petra G.; de Jong, Koert P.; van der Jagt, Eric J.

Purpose: To test the hypothesis that volume changes of ablation zones (AZs) on successive computed tomography (CT) scans could predict ablation site recurrences (ASRs) in patients with colorectal liver metastases treated by radiofrequency (RF) ablation. Materials and Methods: RF ablation was

Monte Carlo description of gas flow from laser-evaporated silver

DEFF Research Database (Denmark)

Ellegaard, O.; Schou, Jørgen; Urbassek, H.M.

1999-01-01

and evaporation rates. These realistic experimental input parameters are further combined with a direct simulation Monte Carlo (DSMC) description of collisions in the gas flow of ablated surface atoms. With this method, new data of plume development and collision processes in the beginning of the ablation process...... can be extracted. It also allows us to identify important processes by comparing the computational results with experimental ones, such as density, energy, and angular distributions. Our main results deviate only slightly from an earlier study with constant surface temperature and evaporation rate...

The internal structure and dynamics of the railgun plasma armature between infinitely wide ablating rails

International Nuclear Information System (INIS)

Frese, M.F.

1991-01-01

This paper reports on computer simulations of the plasma flow in two-dimensionally symmetric railgun plasma arcs that were performed. The direction of symmetry is normal to the insulator surface, so that the rails are effectively infinite in width. The rail surface ablates according to one of two ablation models, in which either all absorbed energy flux, or only the excess over that which the rail material can conduct away, ablates mass. A number of combinations of initial conditions, boundary conditions and resistivity models were explored. The full ablation model produces an arc of continuously growing mass and length, in which the current distribution reaches from the projectile half-way to the breech. The conduction limited ablation model produces a compact arc approximately eight times the bore height in length, which ceases to ablate material from the rails before the projectile reaches a velocity of 1 km/s. There is need for further study in several areas. These include the arc initiation process, the ablation of the insulators, and three-dimensional effects

Forsmark - site descriptive model version 0

International Nuclear Information System (INIS)

2002-10-01

During 2002, the Swedish Nuclear Fuel and Waste Management Company (SKB) is starting investigations at two potential sites for a deep repository in the Precambrian basement of the Fennoscandian Shield. The present report concerns one of those sites, Forsmark, which lies in the municipality of Oesthammar, on the east coast of Sweden, about 150 kilometres north of Stockholm. The site description should present all collected data and interpreted parameters of importance for the overall scientific understanding of the site, for the technical design and environmental impact assessment of the deep repository, and for the assessment of long-term safety. The site description will have two main components: a written synthesis of the site, summarising the current state of knowledge, as documented in the databases containing the primary data from the site investigations, and one or several site descriptive models, in which the collected information is interpreted and presented in a form which can be used in numerical models for rock engineering, environmental impact and long-term safety assessments. The site descriptive models are devised and stepwise updated as the site investigations proceed. The point of departure for this process is the regional site descriptive model, version 0, which is the subject of the present report. Version 0 is developed out of the information available at the start of the site investigation. This information, with the exception of data from tunnels and drill holes at the sites of the Forsmark nuclear reactors and the underground low-middle active radioactive waste storage facility, SFR, is mainly 2D in nature (surface data), and is general and regional, rather than site-specific, in content. For this reason, the Forsmark site descriptive model, version 0, as detailed in the present report, has been developed at a regional scale. It covers a rectangular area, 15 km in a southwest-northeast and 11 km in a northwest-southeast direction, around the

29 CFR 1926.303 - Abrasive wheels and tools.

Science.gov (United States)

2010-07-01

... 29 Labor 8 2010-07-01 2010-07-01 false Abrasive wheels and tools. 1926.303 Section 1926.303 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR... freely on the spindle and shall not be forced on. The spindle nut shall be tightened only enough to hold...

Simpevarp - site descriptive model version 0

Energy Technology Data Exchange (ETDEWEB)

NONE

2002-11-01

During 2002, SKB is starting detailed investigations at two potential sites for a deep repository in the Precambrian rocks of the Fennoscandian Shield. The present report concerns one of those sites, Simpevarp, which lies in the municipality of Oskarshamn, on the southeast coast of Sweden, about 250 kilometres south of Stockholm. The site description will have two main components: a written synthesis of the site, summarising the current state of knowledge, as documented in the databases containing the primary data from the site investigations, and one or several site descriptive models, in which the collected information is interpreted and presented in a form which can be used in numerical models for rock engineering, environmental impact and long-term safety assessments. SKB maintains two main databases at the present time, a site characterisation database called SICADA and a geographic information system called SKB GIS. The site descriptive model will be developed and presented with the aid of the SKB GIS capabilities, and with SKBs Rock Visualisation System (RVS), which is also linked to SICADA. The version 0 model forms an important framework for subsequent model versions, which are developed successively, as new information from the site investigations becomes available. Version 0 is developed out of the information available at the start of the site investigation. In the case of Simpevarp, this is essentially the information which was compiled for the Oskarshamn feasibility study, which led to the choice of that area as a favourable object for further study, together with information collected since its completion. This information, with the exception of the extensive data base from the nearby Aespoe Hard Rock Laboratory, is mainly 2D in nature (surface data), and is general and regional, rather than site-specific, in content. Against this background, the present report consists of the following components: an overview of the present content of the databases

A Study on Accuracy Improvement of Dual Micro Patterns Using Magnetic Abrasive Deburring

Energy Technology Data Exchange (ETDEWEB)

Jin, Dong-Hyun; Kwak, Jae-Seob [Pukyong Nat’l Univ., Busan (Korea, Republic of)

2016-11-15

In recent times, the requirement of a micro pattern on the surface of products has been increasing, and high precision in the fabrication of the pattern is required. Hence, in this study, dual micro patterns were fabricated on a cylindrical workpiece, and deburring was performed by magnetic abrasive deburring (MAD) process. A prediction model was developed, and the MAD process was optimized using the response surface method. When the predicted values were compared with the experimental results, the average prediction error was found to be approximately 7%. Experimental verification shows fabrication of high accuracy dual micro pattern and reliability of prediction model.

Pulmonary ablation: a primer.

Science.gov (United States)

Roberton, Benjamin J; Liu, David; Power, Mark; Wan, John M C; Stuart, Sam; Klass, Darren; Yee, John

2014-05-01

Percutaneous image-guided thermal ablation is safe and efficacious in achieving local control and improving outcome in the treatment of both early stage non-small-cell lung cancer and pulmonary metastatic disease, in which surgical treatment is precluded by comorbidity, poor cardiorespiratory reserve, or unfavorable disease distribution. Radiofrequency ablation is the most established technology, but new thermal ablation technologies such as microwave ablation and cryoablation may offer some advantages. The use of advanced techniques, such as induced pneumothorax and the popsicle stick technique, or combining thermal ablation with radiotherapy, widens the treatment options available to the multidisciplinary team. The intent of this article is to provide the reader with a practical knowledge base of pulmonary ablation by concentrating on indications, techniques, and follow-up. Copyright © 2014 Canadian Association of Radiologists. Published by Elsevier Inc. All rights reserved.

Identification of photoacoustic transients during pulsed laser ablation of the human temporal bone: an experimental model.

Science.gov (United States)

Wong, B J; Dickinson, M R; Berns, M W; Neev, J

1996-12-01

Laser ablation of hard tissues during neurotologic operations has been accomplished with continuous-wave (CW) lasers in the visible and midinfrared spectrum. The mechanism of ablation at these wavelengths is secondary to photothermal-induced tissue destruction. As a result, significant thermal damage to surrounding tissue may occur. Pulsed ultraviolet (UV) lasers have been suggested as an alternative to the argon, KTP-532, and CO2 lasers currently used in clinical practice. The pulse length of Excimer lasers are considerably shorter than the thermal diffusion time of bone tissue, and as a consequence thermal injury is minimal. This makes pulsed lasers an attractive tool for tissue ablation in the ear: in essence a "cold knife." However, the short pulse width of Excimer lasers (typically 10-150 ns) can create large thermoelastic stresses in the ablation specimen. This study identifies the presence of these photoacoustic waves during the Excimer laser treatment of the cadaveric human temporal bone. A XeCl (lambda = 308 nm, tau p = 12 ns) excimer laser was used to ablate hard tissue surrounding the oval window and facial ridge with energies of 75, 45, 25, and 12 mJ/pulse. Spot size was estimated to be 0.5 mm2. Custom high-frequency polyvinyldifluoride (PVDF) piezoelectric film transducers were fabricated and attached to the promontory, round window niche, and facial ridges. The signals were amplified using a low-noise preamplifier and recorded on a digitizing oscilloscope. Photoacoustic waves were clearly identified. Notably, large acoustic waves were measured on the promontory and on both sides of the facial ridge. The implications and clinical relevance of these findings is discussed and compared to findings obtained from a model system.

Numerical study of agglomerate abrasion in a tumbling mixer

NARCIS (Netherlands)

Thanh Nguyen, [No Value; Willemsz, Tofan; Frijlink, Henderik; Maarschalk, Kees van der Voort

2014-01-01

A numerical simulation using the Discrete Element Method (DEM) was performed to investigate the phenomena concerning the abrasion and breakage of agglomerates in a diffusion powder mixer. Agglomerates were created by defining a single structure of particles with bonds of different strengths using

Release of particles by abrasion of CNT composites using a belt sander

International Nuclear Information System (INIS)

Matsui, Yasuto; Nobuyuki, Kato; Ishibashi, Tomonori; Nagaya, Taiki; Yoneda, Minoru

2017-01-01

There have been many reports on the effect of exposure to nanomaterials such as titanium dioxide, silver, and carbon nanotube (CNT) on human health. Several experiments have examined the abrasion of CNT composites, in which CNT nanoparticles are embedded within a resin or rubber matrix, yielding varying results. Separate study of free CNTs and CNT nanoparticles in relation to health is important due to the different physicochemical characteristics of the two types of material. This study investigated the abrasion of CNT composites using a belt sander inside an enclosed chamber, with variation in the applied load and belt sander speed. At lower speeds, the population of particles with diameters of ∼100 nm was observed to increase (cf. mode values of ∼10 nm), and we found a relationship between the amount of the raising dust and the abrasion conditions. From these results, we propose a robust and widely applicable method to create particles of nanomaterial-containing composite materials of various types in order to conduct accelerated exposure assessment studies. (paper)

Bump evolution driven by the x-ray ablation Richtmyer-Meshkov effect in plastic inertial confinement fusion Ablators

Directory of Open Access Journals (Sweden)

Loomis Eric

2013-11-01

Full Text Available Growth of hydrodynamic instabilities at the interfaces of inertial confinement fusion capsules (ICF due to ablator and fuel non-uniformities are a primary concern for the ICF program. Recently, observed jetting and parasitic mix into the fuel were attributed to isolated defects on the outer surface of the capsule. Strategies for mitigation of these defects exist, however, they require reduced uncertainties in Equation of State (EOS models prior to invoking them. In light of this, we have begun a campaign to measure the growth of isolated defects (bumps due to x-ray ablation Richtmyer-Meshkov in plastic ablators to validate these models. Experiments used hohlraums with radiation temperatures near 70 eV driven by 15 beams from the Omega laser (Laboratory for Laser Energetics, University of Rochester, NY, which sent a ∼1.25Mbar shock into a planar CH target placed over one laser entrance hole. Targets consisted of 2-D arrays of quasi-gaussian bumps (10 microns tall, 34 microns FWHM deposited on the surface facing into the hohlraum. On-axis radiography with a saran (Cl Heα − 2.76keV backlighter was used to measure bump evolution prior to shock breakout. Shock speed measurements were also performed to determine target conditions. Simulations using the LEOS 5310 and SESAME 7592 models required the simulated laser power be turned down to 80 and 88%, respectively to match observed shock speeds. Both LEOS 5310 and SESAME 7592 simulations agreed with measured bump areal densities out to 6 ns where ablative RM oscillations were observed in previous laser-driven experiments, but did not occur in the x-ray driven case. The QEOS model, conversely, over predicted shock speeds and under predicted areal density in the bump.

Adhesive, abrasive and oxidative wear in ion-implanted metals

International Nuclear Information System (INIS)

Dearnaley, G.

1985-01-01

Ion implantation is increasingly being used to provide wear resistance in metals and cemented tungsten carbides. Field trials and laboratory tests indicate that the best performance is achieved in mild abrasive wear. This can be understood in terms of the classification of wear modes (adhesive, abrasive, oxidative etc.) introduced by Burwell. Surface hardening and work hardenability are the major properties to be enhanced by ion implantation. The implantation of nitrogen or dual implants of metallic and interstitial species are effective. Recently developed techniques of ion-beam-enhanced deposition of coatings can further improve wear resistance by lessening adhesion and oxidation. In order to support such hard coatings, ion implantation of nitrogen can be used as a preliminary treatment. There is thus emerging a versatile group of related hard vacuum treatments involving intense beams of nitrogen ions for the purpose of tailoring metal surfaces to resist wear. (Auth.)

Abrasion Testing of Products Containing Nanomaterials, SOP-R-2: Scientific Operating Procedure Series: Release (R)

Science.gov (United States)

2016-04-01

Nanotechnologies -- Terminology and definitions for nano-objects -- Nanoparticle, nanofibre and nanoplate Definitions Abrasion - wearing away...ER D C SR -1 6- 2 Environmental Consequences of Nanotechnologies Abrasion Testing of Products Containing Nanomaterials, SOP-R-2...ERDC online library at http://acwc.sdp.sirsi.net/client/default. Environmental Consequences of Nanotechnologies ERDC SR-16-2 April 2016

Effect of Bioactive Glass air Abrasion on Shear Bond Strength of Two Adhesive Resins to Decalcified Enamel.

Directory of Open Access Journals (Sweden)

Alireza Eshghi

2014-12-01

Full Text Available Bioactive glass air abrasion is a conservative technique to remove initial decalcified tissue and caries. This study examined the shear bond strength of composite resin to sound and decalcified enamel air-abraded by bioactive glass (BAG or alumina using etch-and-rinse and self-etch adhesives.Forty-eight permanent molars were root-amputated and sectioned mesiodistally. The obtained 96 specimens were mounted in acrylic resin; the buccal and lingual surfaces remained exposed. A demineralizing solution was used to decalcify half the specimens. Both sound and decalcified specimens were divided into two groups of alumina and bioactive glass air abrasion. In each group, the specimens were subdivided into two subgroups of Clearfil SE Bond or OptiBond FL adhesives (n=12. Composite resin cylinders were bonded on enamel surfaces cured and underwent thermocycling. The specimens were tested for shear bond strength. Data were analyzed using SPSS 16.0 and three-way ANOVA (α=0.05. Similar to the experimental groups, the enamel surface of one specimen underwent SEM evaluation.No significant differences were observed in composite resin bond strength subsequent to alumina or bioactive glass air abrasion preparation techniques (P=0.987. There were no statistically significant differences between the bond strength of etch-and-rinse and self-etch adhesive groups (P=1. Also, decalcified or intact enamel groups had no significant difference (P=0.918. However, SEM analysis showed much less enamel irregularities with BAG air abrasion compared to alumina air abrasion.Under the limitations of this study, preparation of both intact and decalcified enamel surfaces with bioactive glass air abrasion results in similar bond strength of composite resin in comparison with alumina air abrasion using etch-&-rinse or self-etch adhesives.

Effect of Bioactive Glass air Abrasion on Shear Bond Strength of Two Adhesive Resins to Decalcified Enamel

Science.gov (United States)

Eshghi, Alireza; Khoroushi, Maryam; Rezvani, Alireza

2014-01-01

Objective: Bioactive glass air abrasion is a conservative technique to remove initial decalcified tissue and caries. This study examined the shear bond strength of composite resin to sound and decalcified enamel air-abraded by bioactive glass (BAG) or alumina using etch-and-rinse and self-etch adhesives. Materials and Methods: Forty-eight permanent molars were root-amputated and sectioned mesiodistally. The obtained 96 specimens were mounted in acrylic resin; the buccal and lingual surfaces remained exposed. A demineralizing solution was used to decalcify half the specimens. Both sound and decalcified specimens were divided into two groups of alumina and bioactive glass air abrasion. In each group, the specimens were subdivided into two subgroups of Clearfil SE Bond or OptiBond FL adhesives (n=12). Composite resin cylinders were bonded on enamel surfaces cured and underwent thermocycling. The specimens were tested for shear bond strength. Data were analyzed using SPSS 16.0 and three-way ANOVA (α=0.05). Similar to the experimental groups, the enamel surface of one specimen underwent SEM evaluation. Results: No significant differences were observed in composite resin bond strength subsequent to alumina or bioactive glass air abrasion preparation techniques (P=0.987). There were no statistically significant differences between the bond strength of etch-and-rinse and self-etch adhesive groups (P=1). Also, decalcified or intact enamel groups had no significant difference (P=0.918). However, SEM analysis showed much less enamel irregularities with BAG air abrasion compared to alumina air abrasion. Conclusion: Under the limitations of this study, preparation of both intact and decalcified enamel surfaces with bioactive glass air abrasion results in similar bond strength of composite resin in comparison with alumina air abrasion using etch-&-rinse or self-etch adhesives. PMID:25628694

Impact of radiofrequency ablation geometry on electrical conduction

Science.gov (United States)

Rivas, Rhiana N.; Lye, Theresa H.; Hendon, Christine P.

2018-02-01

The gold standard of current treatment for atrial fibrillation is radiofrequency ablation (RFA). Single RFA procedures have low long-term, single-procedure success rates, which can be attributed to factors including inability to measure and visualize lesion depth in real time and incomplete knowledge of how atrial fibrillation manifests and persists. One way to address this problem is to develop a heart model that accurately fits lesion dimensions and depth using OCT to extract structural information. Twenty-three lesions of varying transmurality in left and right swine atrial tissue have been imaged with a Thorlabs OCT system with 6.5-micron axial resolution and a custom Ultra High Resolution system with 2.5-micron axial resolution. The boundaries of the ablation lesions were identified by the appearance of the birefringence artifact to identify areas of un-ablated tissue, as well as by changes to depth penetration and structural features, including decreased contrast between the endocardium and myocardium and disappearance of collagen fibers within the ablation lesion. Using these features, the lateral positions of the lesion boundaries were identified. An algorithm that fit ellipses to the lesion contours modeled the ablation geometry in depth. Lesion dimensions and shape were confirmed by comparison with trichrome histological processing. Finite-element models were fitted with these parameters and electrophysiological simulations were run with the Continuity 6 package. Next steps include correlating lesion geometry to conduction velocity, and including further tissue complexity such as varying tissue composition and fiber orientation. Additional models of linear lesions with gaps and adjacent lesions created with non-perpendicular contact will be created. This work will provide insight into how lesion geometry, tissue composition, and fiber organization impact electrophysiological propagation.

Investigating selective transport and abrasion on an alluvial fan using quantitative grain size and shape analysis

Science.gov (United States)

Litwin, K. L.; Jerolmack, D. J.

2011-12-01

Selective sorting and abrasion are the two major fluvial processes that are attributed to the downstream fining of sediments in rivers and alluvial fans. Selective transport is the process by which smaller grains are preferentially transported downstream while larger grains are deposited closer to the source. Abrasion is defined by the production of fine sediments and sand that occurs by saltation of gravel, where particle-to-particle collisions supply the energy required to break apart grains. We hypothesize that abrasion results in the gradual fining of large grains and the production of fine sands and silts, while sorting accounts for the differences in transport of these two grain-size fractions produced from abrasion, thereby creating the abrupt gravel-sand transition observed in many channel systems. In this research, we explore both selective transport and abrasion processes on the Dog Canyon alluvial fan near Alamogordo, New Mexico. We complete an extensive grain size analysis down the main channel of the fan employing an image-based technique that utilizes an autocorrelation process. We also characterize changes in grain shape using standard shape parameters, as well as Fourier analysis, which allows the study of contributions of grain roughness on a variety of length scales. Sorting appears to dominate the upper portion of the fan; the grain-size distribution narrows moving downstream until reaching a point of equal mobility, at which point sorting ceases. Abrasion exerts a subtle but persistent effect on grains during transport down the fan. Shape analysis reveals that particles become more rounded by the removal of small-scale textural features, a process that is expected to only modestly influence grain size of gravel, but should produce significant quantities of sand. This study provides a better understanding of the importance of grain abrasion and sorting on the downstream fining of channel grains in an alluvial fan, as well as an improved knowledge

Sliding-gate valve for use with abrasive materials

Science.gov (United States)

Ayers, Jr., William J.; Carter, Charles R.; Griffith, Richard A.; Loomis, Richard B.; Notestein, John E.

1985-01-01

The invention is a flow and pressure-sealing valve for use with abrasive solids. The valve embodies special features which provide for long, reliable operating lifetimes in solids-handling service. The valve includes upper and lower transversely slidable gates, contained in separate chambers. The upper gate provides a solids-flow control function, whereas the lower gate provides a pressure-sealing function. The lower gate is supported by means for (a) lifting that gate into sealing engagement with its seat when the gate is in its open and closed positions and (b) lowering the gate out of contact with its seat to permit abrasion-free transit of the gate between its open and closed positions. When closed, the upper gate isolates the lower gate from the solids. Because of this shielding action, the sealing surface of the lower gate is not exposed to solids during transit or when it is being lifted or lowered. The chamber containing the lower gate normally is pressurized slightly, and a sweep gas is directed inwardly across the lower-gate sealing surface during the vertical translation of the gate.

Study on mineral processing technology for abrasive minerals

Energy Technology Data Exchange (ETDEWEB)

Hong, Seong Woong; Yang, Jung Il; Hwang, Seon Kook; Choi, Yeon Ho; Cho, Ken Joon; Shin, Hee Young [Korea Inst. of Geology Mining and Materials, Taejon (Korea, Republic of)

1995-12-01

Buyeo Materials in Buyeogun, Choongnam province is a company producing feldspar concentrate, but does not yet utilize the garnet as abrasive material and other useful heavy minerals wasted out from the process of feldspar ore. The purpose of this study is to develop technology and process for the recovery of garnet concentrate. As results, the garnet is defined as ferro manganese garnet. The optimum process for recovery of garnet concentrate is to primarily concentrate heavy minerals from tailings of feldspar processing. And secondly the heavy minerals concentrated is dried and separated garnet concentrate from other heavy minerals. At this time, the garnet concentrate is yield by 0.176%wt from 0.31%wt of heavy minerals in head ore. The garnet concentrate contains 33.35% SiO{sub 2}, 12.20% Al{sub 2}O{sub 3}, 28.47% Fe{sub 2}O{sub 3}, 11.96% MnO. As for utilization of abrasive materials, a fundamental data was established on technology of grinding and classification. (author). 13 refs., 47 figs., 24 tabs.

CONTROL SYSTEM EVALUATION AND IMPLEMENTATION FOR THE ABRASIVE MACHINING PROCESS ON WOOD

Directory of Open Access Journals (Sweden)

Stephen Jackson

2011-06-01

Full Text Available Continuous process improvement and automation have proven to be powerful tools for the wood processing industries in order to obtain better final product quality and thus increase profits. Abrasive machining represents an important and relevant process in the manufacturing and processing of wood products, which also implies high cost of materials and labor; therefore, special attention to this process is necessary. The objective of this work was to evaluate and demonstrate a process control system for use in the abrasive machining of wood and wood-based products. A control system was created on LabView® to integrate the monitoring process and the actions required, depending on the abrasive machining process conditions. The system acquires information from the optical sensor to detect loading and activate the cleaning system. The system continuously monitors the condition of the abrasive belt (tool wear by using an acoustic emission sensor and alerts the operator of the status of the belt (green, yellow, and red lights indicating satisfactory, medium, and poor belt condition. The system also incorporates an additional safety device, which helps prevent permanent damage to the belt, equipment, or workpiece by alerting the operator when an excessive temperature has been reached. The process control system proved that automation permits enhancement in the consistency of the belt cleaning technique by the elimination of the human errors. Furthermore, this improvement also affects the cost by extending the life of the belt, which reduces setup time, belt cost, operation cost, as well as others.

Radiofrequency ablation of pancreas and optimal cooling of peripancreatic tissue in an ex-vivo porcine model

Directory of Open Access Journals (Sweden)

Michal Crha

2011-01-01

Full Text Available Radiofrequency ablation is a possible palliative treatment for patients suffering from pancreatic neoplasia. However, radiofrequency-induced damage to the peripancreatic tissues during pancreatic ablation might cause fatal complications. The aim of this experimental ex vivo study on pigs was to verify ablation protocols and evaluate whether or not the cooling of peripancereatic tissues during pancreatic ablation has any benefit for their protection against thermal injury. Radiofrequency ablation was performed on 52 pancreatic specimens obtained from pigs. During each pancreatic ablation, continuous measurements of the temperature in the portal vein and duodenal lumen were performed. Peripancreatic tissues were either not cooled or were cooled by being submerged in 14 °C water, or by a perfusion of the portal vein and duodenum with 14 °C saline. The effects of variation in target temperature of the ablated area (90 °C and 100 °C, duration of ablation (5 and 10 min and the effect of peripancreatic tissues cooling were studied. We proved that optimal radiofrequency ablation of the porcine pancreas can be reached with the temperature of 90  °C for 5 min in the ablated area. The perfusion of the duodenal and portal vein by 14 °C saline was found to be the most effective cooling method for minimizing damage to the walls. Continuous measurement of temperatures in peripancreatic tissues will provide useful feedback to assist in their protection against thermal injury. This therapy could be used in the treatment of pancreatic tumours.

Numerical Simulation Analysis of Five-Step Variable-Diameter Pipe with Solid-Liquid Two-Phase Abrasive Flow Polishing

Science.gov (United States)

Li, Junye; Zhang, Hengfu; Wu, Guiling; Hu, Jinglei; Liu, Yang; Sun, Zhihui

2018-01-01

In many areas of precision machining abrasive flow polishing technology has an important role. In order to study the influence of abrasive flow on the polishing effect of variable diameter parts, the fifth step variable diameter tube was taken as the research object to analyze the dynamic pressure and turbulent kinetic energy distribution of inlet velocity on the fifth-order variable diameter tube influences. Through comparative analysis, the abrasive flow polished variable diameter pipe parts have very effective and significant polishing effect and the higher the inlet speed, the more significant the polishing effect.

Controlled wear of vitrified abrasive materials for precision grinding ...

Indian Academy of Sciences (India)

R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

2Machining Research Group, Department of Engineering, University of ... ods are applied to analyse the cutting mechanism in grinding. .... (d) Chemical reaction between abrasive and workpiece material at elevated temperatures ... most common method used for measuring wear flat area employs an optical, or an electron.

Forsmark - site descriptive model version 0

Energy Technology Data Exchange (ETDEWEB)

NONE

2002-10-01

During 2002, the Swedish Nuclear Fuel and Waste Management Company (SKB) is starting investigations at two potential sites for a deep repository in the Precambrian basement of the Fennoscandian Shield. The present report concerns one of those sites, Forsmark, which lies in the municipality of Oesthammar, on the east coast of Sweden, about 150 kilometres north of Stockholm. The site description should present all collected data and interpreted parameters of importance for the overall scientific understanding of the site, for the technical design and environmental impact assessment of the deep repository, and for the assessment of long-term safety. The site description will have two main components: a written synthesis of the site, summarising the current state of knowledge, as documented in the databases containing the primary data from the site investigations, and one or several site descriptive models, in which the collected information is interpreted and presented in a form which can be used in numerical models for rock engineering, environmental impact and long-term safety assessments. The site descriptive models are devised and stepwise updated as the site investigations proceed. The point of departure for this process is the regional site descriptive model, version 0, which is the subject of the present report. Version 0 is developed out of the information available at the start of the site investigation. This information, with the exception of data from tunnels and drill holes at the sites of the Forsmark nuclear reactors and the underground low-middle active radioactive waste storage facility, SFR, is mainly 2D in nature (surface data), and is general and regional, rather than site-specific, in content. For this reason, the Forsmark site descriptive model, version 0, as detailed in the present report, has been developed at a regional scale. It covers a rectangular area, 15 km in a southwest-northeast and 11 km in a northwest-southeast direction, around the

Ultrasound-guided percutaneous thermal ablation of hepatocellular carcinoma using microwave and radiofrequency ablation

Energy Technology Data Exchange (ETDEWEB)

Xu, H.-X.; Xie, X.-Y.; Lu, M.-D. E-mail: lumd@21cn.com; Chen, J.-W.; Yin, X.-Y.; Xu, Z.-F.; Liu, G.-J

2004-01-01

AIM: To investigate the therapeutic efficacy of thermal ablation for treatment of hepatocellular carcinoma (HCC) using microwave and radiofrequency (RF) energy application. MATERIALS AND METHODS: A total of 190 nodules in 97 patients (84 male, 13 female; mean age 53.4 years, range 24-74 years) with HCC were treated with microwave or RF ablation in the last 4 years. The applicators were introduced into the tumours under conscious analgesic sedation by intravenous administration of fentanyl citrate and droperidol and local anaesthesia in both thermal ablation procedures. The patients were then followed up with contrast-enhanced computed tomography (CT) to evaluate treatment response. Survival was analysed using the Kaplan-Meier method. RESULTS: Complete ablation was obtained in 92.6% (176/190) nodules. The complete ablation rates were 94.6% (106/112) in microwave ablation and 89.7% (70/78) in RF ablation. The complete ablation rates in tumours{<=}2.0, 2.1-3.9 and {>=}4.0 cm were 93.1, 93.8 and 86.4%, respectively. Local recurrence was found in 9.5% nodules and the rates in tumours{<=}2.0, 2.1-3.9 and {>=}4.0 cm in diameter were 3.4, 9.9 and 31.8%, respectively. In the follow-up period, 7.1% nodules ablated by microwave and 12.8% by RF presented local recurrence. The 1, 2 and 3-year distant recurrence-free survivals were 47.2, 34.9 and 31.0%, respectively. Estimated mean survival was 32 months, and 1, 2 and 3-year cumulative survivals were 75.6, 58.5, and 50.0%, respectively. One and 2 years survivals of Child-Pugh class A, B and C patients were 83.8 and 70.4%, 78.2 and 53.2%, 36.3 and 27.3%, respectively. CONCLUSION: Thermal ablation therapy by means of microwave and RF energy application is an effective and safe therapeutic technique for hepatocellular carcinoma. Large tumours can be completely ablated, but have a significantly higher risk of local recurrence at follow-up.

Ultrasound-guided percutaneous thermal ablation of hepatocellular carcinoma using microwave and radiofrequency ablation

International Nuclear Information System (INIS)

Xu, H.-X.; Xie, X.-Y.; Lu, M.-D.; Chen, J.-W.; Yin, X.-Y.; Xu, Z.-F.; Liu, G.-J.

2004-01-01

AIM: To investigate the therapeutic efficacy of thermal ablation for treatment of hepatocellular carcinoma (HCC) using microwave and radiofrequency (RF) energy application. MATERIALS AND METHODS: A total of 190 nodules in 97 patients (84 male, 13 female; mean age 53.4 years, range 24-74 years) with HCC were treated with microwave or RF ablation in the last 4 years. The applicators were introduced into the tumours under conscious analgesic sedation by intravenous administration of fentanyl citrate and droperidol and local anaesthesia in both thermal ablation procedures. The patients were then followed up with contrast-enhanced computed tomography (CT) to evaluate treatment response. Survival was analysed using the Kaplan-Meier method. RESULTS: Complete ablation was obtained in 92.6% (176/190) nodules. The complete ablation rates were 94.6% (106/112) in microwave ablation and 89.7% (70/78) in RF ablation. The complete ablation rates in tumours≤2.0, 2.1-3.9 and ≥4.0 cm were 93.1, 93.8 and 86.4%, respectively. Local recurrence was found in 9.5% nodules and the rates in tumours≤2.0, 2.1-3.9 and ≥4.0 cm in diameter were 3.4, 9.9 and 31.8%, respectively. In the follow-up period, 7.1% nodules ablated by microwave and 12.8% by RF presented local recurrence. The 1, 2 and 3-year distant recurrence-free survivals were 47.2, 34.9 and 31.0%, respectively. Estimated mean survival was 32 months, and 1, 2 and 3-year cumulative survivals were 75.6, 58.5, and 50.0%, respectively. One and 2 years survivals of Child-Pugh class A, B and C patients were 83.8 and 70.4%, 78.2 and 53.2%, 36.3 and 27.3%, respectively. CONCLUSION: Thermal ablation therapy by means of microwave and RF energy application is an effective and safe therapeutic technique for hepatocellular carcinoma. Large tumours can be completely ablated, but have a significantly higher risk of local recurrence at follow-up

Pathological effects of lung radiofrequency ablation that contribute to pneumothorax, using a porcine model.

Science.gov (United States)

Izaaryene, Jean; Cohen, Frederic; Souteyrand, Philippe; Rolland, Pierre-Henri; Vidal, Vincent; Bartoli, Jean-Michel; Secq, Veronique; Gaubert, Jean-Yves

2017-11-01

The incidence of pneumothorax is 7 times higher after lung radiofrequency ablation (RFA) than after lung biopsy. The reasons for such a difference have never been objectified. The histopathologic changes in lung tissue are well-studied and established for RF in the ablation zone. However, it has not been previously described what the nature of thermal injury might be along the shaft of the RF electrode as it traverses through normal lung tissue to reach the ablation zone. The purpose of this study was to determine the changes occurring around the RF needle along the pathway between the ablated zone and the pleura. In 3 anaesthetised and ventilated swine, 6 RFA procedures (right and left lungs) were performed using a 14-gauge unipolar multi-tined retractable 3 cm radiofrequency LeVeen probe with a coaxial introducer positioned under CT fluoroscopic guidance. In compliance with literature guidelines, we implemented a gradually increasing thermo-ablation protocol using a RF generator. Helical CT images were acquired pre- and post-RFA procedure to detect and evaluate pneumothorax. Four percutaneous 19-gauge lung biopsies were also performed on the fourth swine under CT guidance. Swine were sacrificed for lung ex vivo examinations, scanning electron microscopy (SEM) and pathological analysis. Three severe (over 50 ml) pneumothorax were detected after RFA. In each one of them, pathological examination revealed a fistulous tract between ablation zone and pleura. No fistulous tract was observed after biopsies. In the 3 cases of severe pneumothorax, the tract was wide open and clearly visible on post procedure CT images and SEM examinations. The RFA tract differed from the needle biopsy tract. The histological changes that are usually found in the ablated zone were observed in the RFA tract's wall and were related to thermal lesions. These modifications caused the creation of a coagulated pulmonary parenchyma rim between the thermo-ablation zone and the pleural space

Turning of materials with high-speed abrasive waterjet

Czech Academy of Sciences Publication Activity Database

Sitek, Libor; Hlaváček, Petr

-, October 2016 (2016), s. 1160-1165 ISSN 1805-0476 R&D Projects: GA MŠk ED2.1.00/03.0082; GA MŠk(CZ) LO1406 Institutional support: RVO:68145535 Keywords : abrasive water jet machining * turning * steel * rock * wood Subject RIV: JQ - Machines ; Tools http://www.mmscience.eu/content/file/archives/MM_Science_201692.pdf

The modeling and synthesis of nanodiamonds by laser ablation of graphite and diamond-like carbon in liquid-confined ambient

Science.gov (United States)

Basso, L.; Gorrini, F.; Bazzanella, N.; Cazzanelli, M.; Dorigoni, C.; Bifone, A.; Miotello, A.

2018-01-01

Nanodiamonds have attracted considerable interest for their potential applications in quantum computation, sensing, and bioimaging. However, synthesis of nanodiamonds typically requires high pressures and temperatures, and is still a challenge. Here, we demonstrate production of nanodiamonds by pulsed laser ablation of graphite and diamond-like carbon in water. Importantly, this technique enables production of nanocrystalline diamonds at room temperature and standard pressure conditions. Moreover, we propose a method for the purification of nanodiamonds from graphitic and amorphous carbon phases that do not require strong acids and harsh chemical conditions. Finally, we present a thermodynamic model that describes the formation of nanodiamonds during pulsed laser ablation. We show that synthesis of the crystalline phase is driven by a graphite-liquid-diamond transition process that occurs at the extreme thermodynamic conditions reached inside the ablation plume.

Examination of Wetting by Liquid Zinc of Steel Sheets Following Various Kinds of Abrasive Blasting

Directory of Open Access Journals (Sweden)

Cecotka M.

2016-06-01

Full Text Available Abrasive blasting is one of the methods of surface working before hot-dip zinc-coating. It allows not only to remove products of corrosion from the surface, but it also affects the quality of the zinc coating applied later, thereby affecting wettability of surface being zinc-coated. The surface working can be done with different types of abrasive material.

Abrasion Resistance and Mechanical Properties of Waste-Glass-Fiber-Reinforced Roller-compacted Concrete

Science.gov (United States)

Yildizel, S. A.; Timur, O.; Ozturk, A. U.

2018-05-01

The potential use of waste glass fibers in roller-compacted concrete (RCC) was investigated with the aim to improve its performance and reduce environmental effects. The research was focused on the abrasion resistance and compressive and flexural strengths of the reinforced concrete relative to those of reference mixes without fibers. The freeze-thaw resistance of RCC mixes was also examined. It was found that the use of waste glass fibers at a rate of 2 % increased the abrasion resistance of the RCC mixes considerably.

Femtosecond laser excitation of dielectric materials: experiments and modeling of optical properties and ablation depths

DEFF Research Database (Denmark)

Wædegaard, Kristian Juncher; Frislev, Martin Thomas; Balling, Peter

2013-01-01

Modeling of the interaction between a dielec- tric material and ultrashort laser pulses provides the tem- poral evolution of the electronic excitation and the optical properties of the dielectric. Experimentally determined re- flectances and ablation depths for sapphire are compared...... to the calculations. A decrease in reflectance at high fluences is observed experimentally, which demonstrates the neces- sity of a temperature-dependent electron scattering rate in the model. The comparison thus provides new constraints on the optical parameters of the model....

Abrasive wear behaviour of bio-active glass ceramics containing ...

Indian Academy of Sciences (India)

In this study, abrasive wear behaviour of bio-active glass ceramic materials produced with two different processes is studied. Hot pressing process and conventional casting and controlled crystallization process were used to produce bio-active ceramics. Fracture toughness of studied material was calculated by fracture ...

Linear stability analysis of double ablation fronts in direct-drive inertial confinement fusion

International Nuclear Information System (INIS)

Yanez, C.; Sanz, J.; Ibanez, L. F.; Olazabal-Loume, M.

2011-01-01

A linear stability theory of double ablation fronts is developed for direct-drive inertial confinement fusion targets. The so-called electron radiative ablation front [S. Fujioka et al., Phys. Rev. Lett. 92, 195001 (2004)] is studied with a self-consistent model. Numerical results are presented as well as an analytical approach for the radiation dominated regime of very steep double ablation front structure. Dispersion relation formula is tackled by means of a sharp boundary model.

Thermal Ablation of Lung Tissue: In Vivo Experimental Comparison of Microwave and Radiofrequency

International Nuclear Information System (INIS)

Crocetti, Laura; Bozzi, Elena; Faviana, Pinuccia; Cioni, Dania; Della Pina, Clotilde; Sbrana, Alberto; Fontanini, Gabriella; Lencioni, Riccardo

2010-01-01

This study was designed to compare feasibility, safety, and effectiveness of microwave (MW) ablation versus radiofrequency (RF) ablation of lung tissue in a rabbit model. Twenty New Zealand White rabbits were submitted to MW (n = 10, group A) or RF ablation (n = 10, group B). The procedures were performed with a prototype MW ablation device with a 1.6-cm radiating section antenna (Valleylab MW Ablation System) and with a 2-cm exposed-tip RF electrode (Cool-tip RF Ablation System). At immediate computed tomography increase in density, maximum diameters (D1-D3) of ablation zones were measured and ablation volume was calculated. Histopathologic assessment was performed 3 and 7 days after the procedure. Technical success was achieved in nine of 10 rabbits in each group. One death occurred in group B. Complications included pneumothorax (group A, n = 4; group B, n = 4), abscess (group A, n = 1; group B, n = 1), and thoracic wall burn (group A, n = 4). No significant differences were demonstrated in attenuation increase (P = 0.73), dimensions (P = 0.28, 0.86, 0.06, respectively, comparing D1-D3) and volume (P = 0.17). At histopathology, ablation zones were similar, with septal necrosis, edema, hemorrhage, and peripheral lymphocytic infiltrate. Complete thrombosis of more than 90% of vessels up to 2 mm in diameter was depicted at the periphery of the ablation zone in group A specimens. In group B specimens, complete thrombosis was depicted in 20% of vessels. Feasibility and safety of MW and RF ablation are similar in a lung rabbit model. MW ablation produces a greater damage to peripheral small vessels inducing thrombosis.

Gamma Reaction History ablator areal density constraints upon correlated diagnostic modeling of National Ignition Facility implosion experiments

Energy Technology Data Exchange (ETDEWEB)

Cerjan, C., E-mail: cerjan1@llnl.gov; Sayre, D. B.; Landen, O. L.; Church, J. A.; Stoeffl, W. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States); Grafil, E. M. [Colorado School of Mines, Golden, Colorado 80401 (United States); Herrmann, H. W.; Hoffman, N. M.; Kim, Y. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2015-03-15

The inelastic neutron scattering induced γ-ray signal from {sup 12}C in an Inertial Confinement Fusion capsule is demonstrated to be an effective and general diagnostic for shell ablator areal density. Experimental acquisition of the time-integrated signal at 4.4 MeV using threshold detection from four gas Čerenkov cells provides a direct measurement of the {sup 12}C areal density near stagnation. Application of a three-dimensional isobaric static model of data acquired in a recent high neutron yield National Ignition Facility experimental campaign reveals two general trends: smaller remaining ablator mass at stagnation and higher shell density with increasing laser drive.

Abrasion-resistant concrete mix designs for precast bridge deck panels.

Science.gov (United States)

2010-08-01

The report documents laboratory investigations undertaken to develop high performance concrete (HPC) for precast and pre-stressed bridge deck components that would reduce the life-cycle cost of bridges by improving the studded tire wear (abrasion) re...

Radiofrequency ablation of pulmonary tumors

Energy Technology Data Exchange (ETDEWEB)

Crocetti, Laura, E-mail: l.crocetti@med.unipi.i [Division of Diagnostic Imaging and Intervention, Department of Liver Transplants, Hepatology and Infectious Diseases, Pisa University School of Medicine (Italy); Lencioni, Riccardo [Division of Diagnostic Imaging and Intervention, Department of Liver Transplants, Hepatology and Infectious Diseases, Pisa University School of Medicine (Italy)

2010-07-15

The development of image-guided percutaneous techniques for local tumor ablation has been one of the major advances in the treatment of solid tumors. Among these methods, radiofrequency (RF) ablation is currently established as the primary ablative modality at most institutions. RF ablation is accepted as the best therapeutic choice for patients with early-stage hepatocellular carcinoma when liver transplantation or surgical resection are not suitable options and is considered as a viable alternate to surgery for inoperable patients with limited hepatic metastatic disease, especially from colorectal cancer. Recently, RF ablation has been demonstrated to be a safe and valuable treatment option for patients with unresectable or medically inoperable lung malignancies. Resection should remain the standard therapy for non-small cell lung cancer (NSCLC) but RF ablation may be better than conventional external-beam radiation for the treatment of the high-risk individual with NSCLC. Initial favourable outcomes encourage combining radiotherapy and RF ablation, especially for treating larger tumors. In the setting of colorectal cancer lung metastases, survival rates provided by RF ablation in selected patients, are substantially higher than those obtained with any chemotherapy regimens and provide indirect evidence that RF ablation therapy improves survival in patients with limited lung metastatic disease.

Erosion and abrasion on dental structures undergoing at-home bleaching

Directory of Open Access Journals (Sweden)

Tarquinio SBC

2011-07-01

Full Text Available Flávio Fernando Demarco1, Sônia Saeger Meireles2, Hugo Ramalho Sarmento1, Raquel Venâncio Fernandes Dantas1, Tatiana Botero3, Sandra Beatriz Chaves Tarquinio11Graduate Program in Dentistry, School of Dentistry, Federal University of Pelotas, Brazil; 2Department of Operative Dentistry, Federal University of Paraíba, Brazil; 3Cariology, Restorative Science, and Endodontics Department, School of Dentistry, University of Michigan, MI, USAAbstract: This review investigates erosion and abrasion in dental structures undergoing at-home bleaching. Dental erosion is a multifactorial condition that may be idiopathic or caused by a known acid source. Some bleaching agents have a pH lower than the critical level, which can cause changes in the enamel mineral content. Investigations have shown that at-home tooth bleaching with low concentrations of hydrogen or carbamide peroxide have no significant damaging effects on enamel and dentin surface properties. Most studies where erosion was observed were in vitro. Even though the treatment may cause side effects like sensitivity and gingival irritation, these usually disappear at the end of treatment. Considering the literature reviewed, we conclude that tooth bleaching agents based on hydrogen or carbamide peroxide have no clinically significant influence on enamel/dentin mineral loss caused by erosion or abrasion. Furthermore, the treatment is tolerable and safe, and any adverse effects can be easily reversed and controlled.Keywords: peroxide, tooth bleaching, enamel, dentin, erosion, abrasion

Ablative skin resurfacing.

Science.gov (United States)

Agrawal, Nidhi; Smith, Greg; Heffelfinger, Ryan

2014-02-01

Ablative laser resurfacing has evolved as a safe and effective treatment for skin rejuvenation. Although traditional lasers were associated with significant thermal damage and lengthy recovery, advances in laser technology have improved safety profiles and reduced social downtime. CO2 lasers remain the gold standard of treatment, and fractional ablative devices capable of achieving remarkable clinical improvement with fewer side effects and shorter recovery times have made it a more practical option for patients. Although ablative resurfacing has become safer, careful patient selection and choice of suitable laser parameters are essential to minimize complications and optimize outcomes. This article describes the current modalities used in ablative laser skin resurfacing and examines their efficacy, indications, and possible side effects. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Influence of Heat Treatment on Abrasive Wear Resistance of Silumin Matrix Composite Castings

Directory of Open Access Journals (Sweden)

Gawdzińska K.

2016-03-01

Full Text Available The authors attempted at examining the effect of heat treatment on abrasive wear resistance of metal composite castings. Metal matrix composites were made by infiltrating preforms created from unordered short fibers (graphite or silumin with liquid aluminium alloy AlSi12(b. Thus prepared composites were subject to solution heat treatment at a temperature of 520°C for four hours, then aging at a temperature of 220°C for four hours. Abrasion resistance of the material was tested before and after thermal treatment.

Hardness and elasticity of abrasive particles measured by instrumented indentation

Czech Academy of Sciences Publication Activity Database

Hvizdoš, P.; Zeleňák, Michal; Hloch, Sergej

2016-01-01

Roč. 8, č. 1 (2016), s. 869-871 ISSN 1805-0476 Institutional support: RVO:68145535 Keywords : abrasive * garnet * hardness * elasticity * instrumental indentation Subject RIV: JQ - Machines ; Tools http://www.mmscience.eu/content/file/archives/MM_Science_201601.pdf

In vivo comparison of simultaneous versus sequential injection technique for thermochemical ablation in a porcine model.

Science.gov (United States)

Cressman, Erik N K; Shenoi, Mithun M; Edelman, Theresa L; Geeslin, Matthew G; Hennings, Leah J; Zhang, Yan; Iaizzo, Paul A; Bischof, John C

2012-01-01

To investigate simultaneous and sequential injection thermochemical ablation in a porcine model, and compare them to sham and acid-only ablation. This IACUC-approved study involved 11 pigs in an acute setting. Ultrasound was used to guide placement of a thermocouple probe and coaxial device designed for thermochemical ablation. Solutions of 10 M acetic acid and NaOH were used in the study. Four injections per pig were performed in identical order at a total rate of 4 mL/min: saline sham, simultaneous, sequential, and acid only. Volume and sphericity of zones of coagulation were measured. Fixed specimens were examined by H&E stain. Average coagulation volumes were 11.2 mL (simultaneous), 19.0 mL (sequential) and 4.4 mL (acid). The highest temperature, 81.3°C, was obtained with simultaneous injection. Average temperatures were 61.1°C (simultaneous), 47.7°C (sequential) and 39.5°C (acid only). Sphericity coefficients (0.83-0.89) had no statistically significant difference among conditions. Thermochemical ablation produced substantial volumes of coagulated tissues relative to the amounts of reagents injected, considerably greater than acid alone in either technique employed. The largest volumes were obtained with sequential injection, yet this came at a price in one case of cardiac arrest. Simultaneous injection yielded the highest recorded temperatures and may be tolerated as well as or better than acid injection alone. Although this pilot study did not show a clear advantage for either sequential or simultaneous methods, the results indicate that thermochemical ablation is attractive for further investigation with regard to both safety and efficacy.

Theoretical analyses of the refractive implications of transepithelial PRK ablations.

Science.gov (United States)

Arba Mosquera, Samuel; Awwad, Shady T

2013-07-01

To analyse the refractive implications of single-step, transepithelial photorefractive keratectomy (TransPRK) ablations. A simulation for quantifying the refractive implications of TransPRK ablations has been developed. The simulation includes a simple modelling of corneal epithelial profiles, epithelial ablation profiles as well as refractive ablation profiles, and allows the analytical quantification of the refractive implications of TransPRK in terms of wasted tissue, achieved optical zone (OZ) and induced refractive error. Wasted tissue occurs whenever the actual corneal epithelial profile is thinner than the applied epithelial ablation profile, achieved OZ is reduced whenever the actual corneal epithelial profile is thicker than the applied epithelial ablation profile and additional refractive errors are induced whenever the actual difference centre-to-periphery in the corneal epithelial profile deviates from the difference in the applied epithelial ablation profile. The refractive implications of TransPRK ablations can be quantified using simple theoretical simulations. These implications can be wasted tissue (∼14 µm, if the corneal epithelial profile is thinner than the ablated one), reduced OZ (if the corneal epithelial profile is thicker than ablated one, very severe for low corrections) and additional refractive errors (∼0.66 D, if the centre-to-periphery progression of the corneal epithelial profile deviates from the progression of the ablated one). When TransPRK profiles are applied to normal, not previously treated, non-pathologic corneas, no specific refractive implications associated to the transepithelial profile can be anticipated; TransPRK would provide refractive outcomes equal to those of standard PRK. Adjustments for the planned OZ and, in the event of retreatments, for the target sphere can be easily derived.

42 CFR 84.130 - Supplied-air respirators; description.

Science.gov (United States)

2010-10-01

... material, and with shielding material such as plastic, glass, woven wire, sheet metal, or other suitable... from rebounding abrasive material, and with shielding material such as plastic, glass, woven wire... against impact and abrasion from rebounding abrasive material, and with shielding material such as plastic...

Treatment of compounds and alloys in radiation hydrodynamics simulations of ablative laser loading

International Nuclear Information System (INIS)

Swift, Damian C.; Gammel, J. Tinka; Clegg, Samuel M.

2004-01-01

Different methods were compared for constructing models of the behavior of a prototype intermetallic compound, nickel aluminide, for use in radiation hydrodynamics simulations of shock wave generation by ablation induced by laser energy. The models included the equation of state, ionization, and radiation opacity. The methods of construction were evaluated by comparing the results of simulations of an ablatively generated shock wave in a sample of the alloy. The most accurate simulations were obtained using the 'constant number density' mixture model to calculate the equation of state and opacity, and Thomas-Fermi ionization. This model is consistent with that found to be most accurate for simulations of ablatively shocked elements

Hydrodynamic description of spin Calogero-Sutherland model

Science.gov (United States)

Abanov, Alexander; Kulkarni, Manas; Franchini, Fabio

2009-03-01

We study a non-linear collective field theory for an integrable spin-Calogero-Sutherland model. The hydrodynamic description of this SU(2) model in terms of charge density, charge velocity and spin currents is used to study non-perturbative solutions (solitons) and examine their correspondence with known quantum numbers of elementary excitations [1]. A conventional linear bosonization or harmonic approximation is not sufficient to describe, for example, the physics of spin-charge (non)separation. Therefore, we need this new collective bosonic field description that captures the effects of the band curvature. In the strong coupling limit [2] this model reduces to integrable SU(2) Haldane-Shastry model. We study a non-linear coupling of left and right spin currents which form a Kac-Moody algebra. Our quantum hydrodynamic description for the spin case is an extension for the one found in the spinless version in [3].[3pt] [1] Y. Kato,T. Yamamoto, and M. Arikawa, J. Phys. Soc. Jpn. 66, 1954-1961 (1997).[0pt] [2] A. Polychronakos, Phys Rev Lett. 70,2329-2331(1993).[0pt] [3] A.G.Abanov and P.B. Wiegmann, Phys Rev Lett 95, 076402(2005)

Metal segmenting using abrasive and reciprocating saws

International Nuclear Information System (INIS)

Allen, R.P.; Fetrow, L.K.; Haun, F.E. Jr.

1987-06-01

This paper evaluates a light-weight, high-power abrasive saw for segmenting radioactively contaminated metal components. A unique application of a reciprocating mechanical saw for the remote disassembly of equipment in a hot cell also is described. The results of this work suggest that use of these techniques for selected remote sectioning applications could minimize operational and access problems and be very cost effective in comparison with other inherently faster sectioning methods. 2 refs., 7 figs

Analysis of plasma-mediated ablation in aqueous tissue

International Nuclear Information System (INIS)

Jiao Jian; Guo Zhixiong

2012-01-01

Plasma-mediated ablation using ultrafast lasers in transparent media such as aqueous tissues is studied. It is postulated that a critical seed free electron density exists due to the multiphoton ionization in order to trigger the avalanche ionization which causes ablation and during the avalanche ionization process the contribution of laser-induced photon ionization is negligible. Based on this assumption, the ablation process can be treated as two separate processes - the multiphoton and avalanche ionizations - at different time stages; so that an analytical solution to the evolution of plasma formation is obtained for the first time. The analysis is applied to plasma-mediated ablation in corneal epithelium and validated via comparison with experimental data available in the literature. The critical seed free-electron density and the time to initiate the avalanche ionization for sub-picosecond laser pulses are analyzed. It is found that the critical seed free-electron density decreases as the pulse width increases, obeying a t p -5.65 rule. This model is further extended to the estimation of crater size in the ablation of tissue-mimic polydimethylsiloxane (PDMS). The results match well with the available experimental measurements.

Adhesive interfaces of enamel and dentin prepared by air-abrasion at different distances

International Nuclear Information System (INIS)

Chinelatti, Michelle Alexandra; Andreolli do Amaral, Thais Helena; Borsatto, Maria Cristina; Palma-Dibb, Regina Guenka; Corona, Silmara Aparecida Milori

2007-01-01

The purpose of this study was to analyse, by scanning electron microscopy (SEM), the morphology of enamel and dentin/adhesive interfaces in cavities prepared by air-abrasion at different working distances. Thirty sound third human molars were selected and, on both their buccal and lingual surfaces, class V cavities were prepared by air-abrasion, at 2-, 4-, 6-, 8- and 10-mm working distances, or high-speed bur (control group). After preparation, all cavities were etched with 35% phosphoric acid gel and restored with Single Bond/Filtek Z-250. Buccal and lingual surfaces were separated and restorations sectioned in a buccolingual direction, providing two sections of each cavity, which were analysed by scanning electron microscopy. It was observed that the distances of 6 and 8 mm promoted more homogeneous dentin/adhesive interfaces, with tags formation, and more uniform for enamel, which were similar to the control group. It may be concluded that the air-abrasion working distance can influence the morphology of enamel and dentin/adhesive interfaces, and the intermediate distances provided better adhesive interfaces

Theoretical and experimental analysis of amplitude control ablation and bipolar ablation in creating linear lesion and discrete lesions for treating atrial fibrillation.

Science.gov (United States)

Yan, Shengjie; Wu, Xiaomei; Wang, Weiqi

2017-09-01

Radiofrequency (RF) energy is often used to create a linear lesion or discrete lesions for blocking the accessory conduction pathways for treating atrial fibrillation. By using finite element analysis, we study the ablation effect of amplitude control ablation mode (AcM) and bipolar ablation mode (BiM) in creating a linear lesion and discrete lesions in a 5-mm-thick atrial wall; particularly, the characteristic of lesion shape has been investigated in amplitude control ablation. Computer models of multipolar catheter were developed to study the lesion dimensions in atrial walls created through AcM, BiM and special electrodes activated ablation methods in AcM and BiM. To validate the theoretical results in this study, an in vitro experiment with porcine cardiac tissue was performed. At 40 V/20 V root mean squared (RMS) of the RF voltage for AcM, the continuous and transmural lesion was created by AcM-15s, AcM-5s and AcM-ad-20V ablation in 5-mm-thick atrial wall. At 20 V RMS for BiM, the continuous but not transmural lesion was created. AcM ablation yielded asymmetrical and discrete lesions shape, whereas the lesion shape turned to more symmetrical and continuous as the electrodes alternative activated period decreased from 15 s to 5 s. Two discrete lesions were created when using AcM, AcM-ad-40V, BiM-ad-20V and BiM-ad-40V. The experimental and computational thermal lesion shapes created in cardiac tissue were in agreement. Amplitude control ablation technology and bipolar ablation technology are feasible methods to create continuous lesion or discrete for pulmonary veins isolation.

The prediction of radiofrequency ablation zone volume using vascular indices of 3-dimensional volumetric colour Doppler ultrasound in an in vitro blood-perfused bovine liver model

Science.gov (United States)

Lanctot, Anthony C; McCarter, Martin D; Roberts, Katherine M; Glueck, Deborah H; Dodd, Gerald D

2017-01-01

Objective: To determine the most reliable predictor of radiofrequency (RF) ablation zone volume among three-dimensional (3D) volumetric colour Doppler vascular indices in an in vitro blood-perfused bovine liver model. Methods: 3D colour Doppler volume data of the local hepatic parenchyma were acquired from 37 areas of 13 bovine livers connected to an in vitro oxygenated blood perfusion system. Doppler vascular indices of vascularization index (VI), flow index (FI) and vascularization flow index (VFI) were obtained from the volume data using 3D volume analysis software. 37 RF ablations were performed at the same locations where the ultrasound data were obtained from. The relationship of these vascular indices and the ablation zone volumes measured from gross specimens were analyzed using a general linear mixed model fit with random effect for liver and backward stepwise regression analysis. Results: FI was significantly associated with ablation zone volumes measured on gross specimens (p = 0.0047), but explained little of the variance (Rβ2 = 0.21). Ablation zone volume decreased by 0.23 cm3 (95% confidence interval: −0.38, −0.08) for every 1 increase in FI. Neither VI nor VFI was significantly associated with ablation zone volumes (p > 0.05). Conclusion: Although FI was associated with ablation zone volumes, it could not sufficiently explain their variability, limiting its clinical applicability. VI, FI and VFI are not clinically useful in the prediction of RF ablation zone volume in the liver. Advances in knowledge: Despite a significant association of FI with ablation zone volumes, VI, FI and VFI cannot be used for their prediction. Different Doppler vascular indices need to be investigated for clinical use. PMID:27925468

Abrasive wear behavior of heat-treated ABC-silicon carbide

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xiao Feng; Lee, Gun Y.; Chen, Da; Ritchie, Robert O.; De Jonghe, Lutgard C.

2002-06-17

Hot-pressed silicon carbide, containing aluminum, boron, and carbon additives (ABC-SiC), was subjected to three-body and two-body wear testing using diamond abrasives over a range of sizes. In general, the wear resistance of ABC-SiC, with suitable heat treatment, was superior to that of commercial SiC.

Effects of different lasers and particle abrasion on surface characteristics of zirconia ceramics.

Directory of Open Access Journals (Sweden)

Sakineh Arami

2014-04-01

Full Text Available The aim of this study was to assess the surface of yttrium-stabilized tetragonal zirconia (Y-TZP after surface treatment with lasers and airborne-particle abrasion.First, 77 samples of presintered zirconia blocks measuring 10 × 10 × 2 mm were made, sintered and polished. Then, they were randomly divided into 11 groups (n=7 and received surface treatments namely, Er:YAG laser irradiation with output power of 1.5, 2 and 2.5 W, Nd:YAG laser with output power of 1.5, 2 and 2.5 W, CO2 laser with output power of 3, 4 and 5 W, AL2O3 airborne-particle abrasion (50μ and no treatment (controls. Following treatment, the parameters of surface roughness such as Ra, Rku and Rsk were evaluated using a digital profilometer and surface examination was done by SEM.According to ANOVA and Tukey's test, the mean surface roughness (Ra after Nd:YAG laser irradiation at 2 and 2.5 W was significantly higher than other groups. Roughness increased with increasing output power of Nd:YAG and CO2 lasers. Treated surfaces by Er:YAG laser and air abrasion showed similar surface roughness. SEM micrographs showed small microcracks in specimens irradiated with Nd:YAG and CO2 lasers.Nd:YAG laser created a rough surface on the zirconia ceramic with many microcracks; therefore, its use is not recommended. Air abrasion method can be used with Er:YAG laser irradiation for the treatment of zirconia ceramic.

Three body abrasion of laser surface alloyed aluminium AA1200

CSIR Research Space (South Africa)

Mabhali, Luyolo AB

2012-06-01

Full Text Available Laser surface alloying of aluminium AA1200 was performed with a 4 kW Nd:YAG laser to improve the abrasion wear resistance. Aluminium surfaces reinforced with metal matrix composites and intermetallic phases were achieved. The phases present depended...

Optical tools for high-throughput screening of abrasion resistance of combinatorial libraries of organic coatings

Science.gov (United States)

Potyrailo, Radislav A.; Chisholm, Bret J.; Olson, Daniel R.; Brennan, Michael J.; Molaison, Chris A.

2002-02-01

Design, validation, and implementation of an optical spectroscopic system for high-throughput analysis of combinatorially developed protective organic coatings are reported. Our approach replaces labor-intensive coating evaluation steps with an automated system that rapidly analyzes 8x6 arrays of coating elements that are deposited on a plastic substrate. Each coating element of the library is 10 mm in diameter and 2 to 5 micrometers thick. Performance of coatings is evaluated with respect to their resistance to wear abrasion because this parameter is one of the primary considerations in end-use applications. Upon testing, the organic coatings undergo changes that are impossible to quantitatively predict using existing knowledge. Coatings are abraded using industry-accepted abrasion test methods at single-or multiple-abrasion conditions, followed by high- throughput analysis of abrasion-induced light scatter. The developed automated system is optimized for the analysis of diffusively scattered light that corresponds to 0 to 30% haze. System precision of 0.1 to 2.5% relative standard deviation provides capability for the reliable ranking of coatings performance. While the system was implemented for high-throughput screening of combinatorially developed organic protective coatings for automotive applications, it can be applied to a variety of other applications where materials ranking can be achieved using optical spectroscopic tools.

3D patient-specific models for left atrium characterization to support ablation in atrial fibrillation patients.

Science.gov (United States)

Valinoti, Maddalena; Fabbri, Claudio; Turco, Dario; Mantovan, Roberto; Pasini, Antonio; Corsi, Cristiana

2018-01-01

Radiofrequency ablation (RFA) is an important and promising therapy for atrial fibrillation (AF) patients. Optimization of patient selection and the availability of an accurate anatomical guide could improve RFA success rate. In this study we propose a unified, fully automated approach to build a 3D patient-specific left atrium (LA) model including pulmonary veins (PVs) in order to provide an accurate anatomical guide during RFA and without PVs in order to characterize LA volumetry and support patient selection for AF ablation. Magnetic resonance data from twenty-six patients referred for AF RFA were processed applying an edge-based level set approach guided by a phase-based edge detector to obtain the 3D LA model with PVs. An automated technique based on the shape diameter function was designed and applied to remove PVs and compute LA volume. 3D LA models were qualitatively compared with 3D LA surfaces acquired during the ablation procedure. An expert radiologist manually traced the LA on MR images twice. LA surfaces from the automatic approach and manual tracing were compared by mean surface-to-surface distance. In addition, LA volumes were compared with volumes from manual segmentation by linear and Bland-Altman analyses. Qualitative comparison of 3D LA models showed several inaccuracies, in particular PVs reconstruction was not accurate and left atrial appendage was missing in the model obtained during RFA procedure. LA surfaces were very similar (mean surface-to-surface distance: 2.3±0.7mm). LA volumes were in excellent agreement (y=1.03x-1.4, r=0.99, bias=-1.37ml (-1.43%) SD=2.16ml (2.3%), mean percentage difference=1.3%±2.1%). Results showed the proposed 3D patient-specific LA model with PVs is able to better describe LA anatomy compared to models derived from the navigation system, thus potentially improving electrograms and voltage information location and reducing fluoroscopic time during RFA. Quantitative assessment of LA volume derived from our 3D LA

Abrasive water jet cutting technique for biological shield concrete dismantlement

International Nuclear Information System (INIS)

Konno, T.; Narazaki, T.; Yokota, M.; Yoshida, H.; Miura, M.; Miyazaki, Y.

1987-01-01

The Japan Atomic Energy Research Institute (JAERI) is developing the abrasive-water jet cutting system to be applied to dismantling the biological shield walls of the JPDR as a part of the reactor dismantling technology development project. This is a total system for dismantling highly activated concrete. The concrete biological shield wall is cut into blocks by driving the abrasive-water jet nozzle, which is operated with a remote, automated control system. In this system, the concrete blocks are removed to a container, while the slurry and dust/mist which are generated during cutting are collected and treated, both automatically. It is a very practical method and will quite probably by used for actual dismantling of commercial power reactors in the future because it can minimize workers' exposure to radioactivity during dismantling, contributes to preventing diffusion of radiation, and reduces the volume of contaminated secondary waste

Enhanced ablation of small anodes in a carbon nanotube arc discharge

Science.gov (United States)

Raitses, Yevgeny; Fetterman, Abraham; Keidar, Michael

2008-11-01

An atmospheric pressure helium arc discharge is used for carbon nanotube synthesis. The arc discharge operates in an anodic mode with the ablating anode made from a graphite material. For such conditions, models predict the electron-repelling (negative) anode sheath. In the present experiments, the anode ablation rate is investigated as a function of the anode diameter. It is found that anomalously high ablation occurs for small anode diameters (Fetterman, Y. Raitses and M. Keidar, Carbon (2008).

Micro-scale abrasive wear behavior of medical implant material Ti-25Nb-3Mo-3Zr-2Sn alloy on various friction pairs.

Science.gov (United States)

Wang, Zhenguo; Huang, Weijiu; Ma, Yanlong

2014-09-01

The micro-scale abrasion behaviors of surgical implant materials have often been reported in the literature. However, little work has been reported on the micro-scale abrasive wear behavior of Ti-25Nb-3Mo-3Zr-2Sn (TLM) titanium alloy in simulated body fluids, especially with respect to friction pairs. Therefore, a TE66 Micro-Scale Abrasion Tester was used to study the micro-scale abrasive wear behavior of the TLM alloy. This study covers the friction coefficient and wear loss of the TLM alloy induced by various friction pairs. Different friction pairs comprised of ZrO2, Si3N4 and Al2O3 ceramic balls with 25.4mm diameters were employed. The micro-scale abrasive wear mechanisms and synergistic effect between corrosion and micro-abrasion of the TLM alloy were investigated under various wear-corrosion conditions employing an abrasive, comprised of SiC (3.5 ± 0.5 μm), in two test solutions, Hanks' solution and distilled water. Before the test, the specimens were heat treated at 760°C/1.0/AC+550°C/6.0/AC. It was discovered that the friction coefficient values of the TLM alloy are larger than those in distilled water regardless of friction pairs used, because of the corrosive Hanks' solution. It was also found that the value of the friction coefficient was volatile at the beginning of wear testing, and it became more stable with further experiments. Because the ceramic balls have different properties, especially with respect to the Vickers hardness (Hv), the wear loss of the TLM alloy increased as the ball hardness increased. In addition, the wear loss of the TLM alloy in Hanks' solution was greater than that in distilled water, and this was due to the synergistic effect of micro-abrasion and corrosion, and this micro-abrasion played a leading role in the wear process. The micro-scale abrasive wear mechanism of the TLM alloy gradually changed from two-body to mixed abrasion and then to three-body abrasion as the Vickers hardness of the balls increased. Copyright �

Models of electron conductivity which lead to ablation stabilization of fluid instabilities in laser-driven implosions

International Nuclear Information System (INIS)

Lindl, J.D.; Mead, W.C.

1975-01-01

LASNEX calculations with a modified electron conductivity show the existence of a firepolishing stabilization effect. By modifying the thermal conductivity so that K α T/sup n//rho/sup m/, one is able to construct a situation in which the electrons deposit their energy in a thin layer at the ablation surface and closely match the zero order solutions assumed earlier. The firepolishing effect appears to require that a significant fraction of the total pressure be due to the ablation process itself rather than the thermal pressure in the corona gas. It also requires KL approximately 1 where L is the scale height for decay of thermal perturbations generated at the ablation surface. For classical electron conductivity, because the thermal flux depends linearly on the grams/cm 2 necessary to stop the electrons, (1/rho) nabla rho approximately (1/T) nabla T near the ablation surface so that the pressure is nearly constant across the ablation surface. Hence there is no ablation pressure as such and no firepolishing effect for electron-driven implosions

Percutaneous thermal ablation of renal neoplasms

International Nuclear Information System (INIS)

Tacke, J.; Mahnken, A.H.; Guenther, R.W.

2005-01-01

Due to modern examination techniques such as multidetector computed tomography and high-field magnetic resonance imaging, the detection rate of renal neoplasms is continually increasing. Even though tumors exceeding 4 cm in diameter rarely metastasize, all renal lesions that are possible neoplasms should be treated. Traditional treatment techniques include radical nephrectomy or nephron-sparing resection, which are increasingly performed laparoscopically. Modern thermal ablation techniques such as hyperthermal techniques like radiofrequency ablation RFA, laser induced thermal ablation LITT, focused ultrasound FUS and microwave therapy MW, as well as hypothermal techniques (cryotherapy) may be a useful treatment option for patients who are unfit for or refuse surgical resection. Cryotherapy is the oldest and best known thermal ablation technique and can be performed laparoscopically or percutaneously. Since subzero temperatures have no antistyptic effect, additional maneuvers must be performed to control bleeding. Percutaneous cryotherapy of renal tumors is a new and interesting method, but experience with it is still limited. Radiofrequency ablation is the most frequently used method. Modern probe design allows volumes between 2 and 5 cm in diameter to be ablated. Due to hyperthermal tract ablation, the procedure is deemed to be safe and has a low complication rate. Although there are no randomized comparative studies to open resection, the preliminary results for renal RFA are promising and show RFA to be superior to other thermal ablation techniques. Clinical success rates are over 90% for both, cryo- and radiofrequency ablation. Whereas laser induced thermal therapy is established in hepatic ablation, experience is minimal with respect to renal application. For lesions of more than 2 cm in diameter, additional cooling catheters are required. MR thermometry offers temperature control during ablation. Microwave ablation is characterized by small ablation volumes

Simpevarp - site descriptive model version 0

International Nuclear Information System (INIS)

2002-11-01

During 2002, SKB is starting detailed investigations at two potential sites for a deep repository in the Precambrian rocks of the Fennoscandian Shield. The present report concerns one of those sites, Simpevarp, which lies in the municipality of Oskarshamn, on the southeast coast of Sweden, about 250 kilometres south of Stockholm. The site description will have two main components: a written synthesis of the site, summarising the current state of knowledge, as documented in the databases containing the primary data from the site investigations, and one or several site descriptive models, in which the collected information is interpreted and presented in a form which can be used in numerical models for rock engineering, environmental impact and long-term safety assessments. SKB maintains two main databases at the present time, a site characterisation database called SICADA and a geographic information system called SKB GIS. The site descriptive model will be developed and presented with the aid of the SKB GIS capabilities, and with SKBs Rock Visualisation System (RVS), which is also linked to SICADA. The version 0 model forms an important framework for subsequent model versions, which are developed successively, as new information from the site investigations becomes available. Version 0 is developed out of the information available at the start of the site investigation. In the case of Simpevarp, this is essentially the information which was compiled for the Oskarshamn feasibility study, which led to the choice of that area as a favourable object for further study, together with information collected since its completion. This information, with the exception of the extensive data base from the nearby Aespoe Hard Rock Laboratory, is mainly 2D in nature (surface data), and is general and regional, rather than site-specific, in content. Against this background, the present report consists of the following components: an overview of the present content of the databases

Studies of the impurity pellet ablation in the high-temperature plasma of magnetic confinement devices

International Nuclear Information System (INIS)

Sergeev, V. Yu.; Bakhareva, O. A.; Kuteev, B. V.; Tendler, M.

2006-01-01

The ablation of impurity pellets in tokamak and stellarator plasmas is investigated. Different mechanisms for shielding the heat fluxes from the surrounding plasma to the pellet surface are discussed. A model for impurity pellet ablation is developed that can account for both neutral and electrostatic shielding. It is shown that the experimental values of the impurity pellet ablation rate are well described by the neutral gas shielding model over a wide range of plasma temperatures and densities. Taking into account the electrostatic shielding leads to worse agreement between the predictions of the model and the experimental data; this result still remains unclear. Scaling laws are obtained that allow one to estimate the local ablation rate of impurity pellets made of various materials over a wide range of plasma parameters in the neutral gas shielding model

Ventricular fibrillation occurring after atrioventricular node ablation despite minimal difference between pre- and post-ablation heart rates.

Science.gov (United States)

Squara, F; Theodore, G; Scarlatti, D; Ferrari, E

2017-02-01

We report the case of an 82-year-old man presenting with ventricular fibrillation (VF) occurring acutely after atrioventricular node (AVN) ablation. This patient had severe valvular cardiomyopathy, chronic atrial fibrillation (AF), and underwent prior to the AVN ablation a biventricular implantable cardiac defibrillator positioning. The VF was successfully cardioverted with one external electrical shock. What makes this presentation original is that the pre-ablation spontaneous heart rate in AF was slow (84 bpm), and that VF occurred after ablation despite a minimal heart rate drop of only 14 bpm. VF is the most feared complication of AVN ablation, but it had previously only been described in case of acute heart rate drop after ablation of at least 30 bpm (and more frequently>50 bpm). This case report highlights the fact that VF may occur after AVN ablation regardless of the heart rate drop, rendering temporary fast ventricular pacing mandatory whatever the pre-ablation heart rate. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Renal denervation using catheter-based radiofrequency ablation with temperature control: renovascular safety profile and underlying mechanisms in a hypertensive canine model.

Science.gov (United States)

Li, Huijie; Yu, Hang; Zeng, Chunyu; Fang, Yuqiang; He, Duofen; Zhang, Xiaoqun; Wen, Chunlan; Yang, Chengming

2015-01-01

Renal denervation is a novel method for hypertension treatment. In this study, we aimed to investigate the safety and efficacy of radiofrequency ablation (RFA) at ablation temperatures of 45 °C or 50 °C and its possible mechanisms. A hypertensive canine model was established by abdominal aortic constriction in 20 healthy hybrid dogs. These dogs were then randomly assigned to the treatment and the control groups, with dogs in the treatment group further randomly assigned to receive RFA at ablation temperatures of 45 °C or 50 °C. In the treatment group, RFA was performed at 1 month after modeling; renal angiography was performed at 2 months after ablation. The arterial vessels of the dogs were examined histologically with hematoxylin and eosin staining. Changes in blood pressure in the foreleg and whole-body norepinephrine spillover rate were also assessed. No arterial stenosis, dissection, thrombosis or other abnormalities were detected in the treated vessels by renal angiography, yet histology results showed minimal to mild renal arterial injury. Renal denervation resulted in a marked decrease in the whole-body norepinephrine spillover rate (p 0.05). Renal denervation can be performed without acute major adverse events, using catheter-based RFA with temperature control. The procedure was feasible in reducing blood pressure by at least partially inhibiting sympathetic drive and systemic sympathetic outflow.

Confidence assessment. Site-descriptive modelling SDM-Site Laxemar

International Nuclear Information System (INIS)

2009-06-01

The objective of this report is to assess the confidence that can be placed in the Laxemar site descriptive model, based on the information available at the conclusion of the surface-based investigations (SDM-Site Laxemar). In this exploration, an overriding question is whether remaining uncertainties are significant for repository engineering design or long-term safety assessment and could successfully be further reduced by more surface-based investigations or more usefully by explorations underground made during construction of the repository. Procedures for this assessment have been progressively refined during the course of the site descriptive modelling, and applied to all previous versions of the Forsmark and Laxemar site descriptive models. They include assessment of whether all relevant data have been considered and understood, identification of the main uncertainties and their causes, possible alternative models and their handling, and consistency between disciplines. The assessment then forms the basis for an overall confidence statement. The confidence in the Laxemar site descriptive model, based on the data available at the conclusion of the surface based site investigations, has been assessed by exploring: - Confidence in the site characterization data base, - remaining issues and their handling, - handling of alternatives, - consistency between disciplines and - main reasons for confidence and lack of confidence in the model. Generally, the site investigation database is of high quality, as assured by the quality procedures applied. It is judged that the Laxemar site descriptive model has an overall high level of confidence. Because of the relatively robust geological model that describes the site, the overall confidence in the Laxemar Site Descriptive model is judged to be high, even though details of the spatial variability remain unknown. The overall reason for this confidence is the wide spatial distribution of the data and the consistency between

Confidence assessment. Site-descriptive modelling SDM-Site Laxemar

Energy Technology Data Exchange (ETDEWEB)

2008-12-15

The objective of this report is to assess the confidence that can be placed in the Laxemar site descriptive model, based on the information available at the conclusion of the surface-based investigations (SDM-Site Laxemar). In this exploration, an overriding question is whether remaining uncertainties are significant for repository engineering design or long-term safety assessment and could successfully be further reduced by more surface-based investigations or more usefully by explorations underground made during construction of the repository. Procedures for this assessment have been progressively refined during the course of the site descriptive modelling, and applied to all previous versions of the Forsmark and Laxemar site descriptive models. They include assessment of whether all relevant data have been considered and understood, identification of the main uncertainties and their causes, possible alternative models and their handling, and consistency between disciplines. The assessment then forms the basis for an overall confidence statement. The confidence in the Laxemar site descriptive model, based on the data available at the conclusion of the surface based site investigations, has been assessed by exploring: - Confidence in the site characterization data base, - remaining issues and their handling, - handling of alternatives, - consistency between disciplines and - main reasons for confidence and lack of confidence in the model. Generally, the site investigation database is of high quality, as assured by the quality procedures applied. It is judged that the Laxemar site descriptive model has an overall high level of confidence. Because of the relatively robust geological model that describes the site, the overall confidence in the Laxemar Site Descriptive model is judged to be high, even though details of the spatial variability remain unknown. The overall reason for this confidence is the wide spatial distribution of the data and the consistency between

Performance tests of an abrasive cut-off systems for the finishing of high-precision casts

OpenAIRE

A. Fedoryszyn; W. T. Meksa; G. Woźnicki

2008-01-01

The paper summarizes the performance data of a newly designed and engineered grinding and cut-off system. The machine is used for separation of models manufactured by the investment casting method. The machine comprises the following units:- base supporting other assemblies and elements: abrasive disc holder and drives; this solution enables an easy replacement and access to holding elements while a belt transmission allows the disc rpm to be varied,- mechanism moving the spindle in the horiz...

Development and assessment of two decontamination processes: closed electropolishing system for decontamination of underwater surfaces -vibratory decontamination with abrasives

International Nuclear Information System (INIS)

Benavides, E.; Fajardo, M.

1992-01-01

Two decontamination processes have been developed to decontaminate the stainless steel components of nuclear power plants. The first process uses an underwater closed electropolishing system for the decontamination of large stainless steel surfaces in flooded systems without loss of electrolyte. Large underwater contaminated areas can be treated with an electropolishing head covering an area of 2 m 2 in one step. The decontamination factors achieved with this technique range between 100 and 1000. The second process consists in the decontamination of nuclear components using vibratory equipment with self-cleaning abrasives generating a minimum quantity of waste. This technique may reach contamination factors similar to those obtained with other abrasive methods (brush abrasion, abrasive blasting, etc...). The obtained decontamination factors range between 5 and 50. Only a small quantity of waste is generated, which is treated and reduced in volume by filtration and evaporation

Thermal Ablation of T1c Renal Cell Carcinoma: A Comparative Assessment of Technical Performance, Procedural Outcome, and Safety of Microwave Ablation, Radiofrequency Ablation, and Cryoablation.

Science.gov (United States)

Zhou, Wenhui; Arellano, Ronald S

2018-04-06

To evaluate perioperative outcomes of thermal ablation with microwave (MW), radiofrequency (RF), and cryoablation for stage T1c renal cell carcinoma (RCC). A retrospective analysis of 384 patients (mean age, 71 y; range, 22-88 y) was performed between October 2006 and October 2016. Mean radius, exophytic/endophytic, nearness to collecting system or sinus, anterior/posterior, and location relative to polar lines; preoperative aspects and dimensions used for anatomic classification; and centrality index scores were 6.3, 7.9, and 2.7, respectively. Assessment of pre- and postablation serum blood urea nitrogen, creatinine, and estimated glomerular filtration rate was performed to assess functional outcomes. Linear regression analyses were performed to compare sedation medication dosages among the three treatment cohorts. Univariable and multivariable logistic regression analyses were performed to compare rates of residual disease and complications among treatment modalities. A total of 437 clinical stage T1N0M0 biopsy-proven RCCs measuring 1.2-6.9 cm were treated with computed tomography (CT)-guided MW ablation (n = 44; 10%), RF ablation (n = 347; 79%), or cryoablation (n = 46; 11%). There were no significant differences in patient demographic or tumor characteristics among cohorts. Complication rates and immediate renal function changes were similar among the three ablation modalities (P = .46 and P = .08, respectively). MW ablation was associated with significantly decreased ablation time (P < .05), procedural time (P < .05), and dosage of sedative medication (P < .05) compared with RF ablation and cryoablation. CT-guided percutaneous MW ablation is comparable to RF ablation or cryoablation for the treatment of stage T1N0M0 RCC with regard to treatment response and is associated with shorter treatment times and less sedation than RF ablation or cryoablation. In addition, the safety profile of CT-guided MW ablation is noninferior to those of RF ablation or

Testing of abrasion materials

International Nuclear Information System (INIS)

Hummert, G.

1983-01-01

A method of abrasion testing according to ASTM C 704-76 a is presented for steel fibre concrete mortar, fusion-cast basalt and a surface coating material and results of practical interest are mentioned. Due to the high technical demands on these materials and their specific fields of application, the very first test already supplied interesting findings. From the user's point of view, the method is an interesting alternative to the common test methods, e.g. according to DIN 52 108 (wheel test according to Boehme). In English-speaking countries, testing according to ASTM is often mandatory in the refractory industry in order to assure constant quality of refractory materials after setting. The method is characterized by good comparability and high accuracy of measurement. Only the test piece is exchanged while the test conditions remain constant, so that accurate information on the material studied is obtained. (orig.) [de

Description of the Lewin Natural Gas Model

International Nuclear Information System (INIS)

Kuuskraa, V.; Godec, M.

1989-01-01

This paper provides a brief description of the Lewin Natural Gas Model, shows how this model differs in key features from the other models participating in EMF-9, and describes how the different modeling scenarios analyzed in EMF-9 were implemented in the Lewin model. This background helps explain the key results that have been gained from applying the Lewin model to the EMF scenarios

Perioral Rejuvenation With Ablative Erbium Resurfacing.

Science.gov (United States)

Cohen, Joel L

2015-11-01

Since the introduction of the scanning full-field erbium laser, misconceptions regarding ablative erbium resurfacing have resulted in its being largely overshadowed by ablative fractional resurfacing. This case report illustrates the appropriateness of full-field erbium ablation for perioral resurfacing. A patient with profoundly severe perioral photodamage etched-in lines underwent full-field ablative perioral resurfacing with an erbium laser (Contour TRL, Sciton Inc., Palo Alto, CA) that allows separate control of ablation and coagulation. The pre-procedure consultations included evaluation of the severity of etched-in lines, and discussion of patient goals, expectations, and appropriate treatment options, as well as a review of patient photos and post-treatment care required. The author generally avoids full-field erbium ablation in patients with Fitzpatrick type IV and above. For each of 2 treatment sessions (separated by approximately 4 months), the patient received (12 cc plain 2% lidodaine) sulcus blocks before undergoing 4 passes with the erbium laser at 150 μ ablation, no coagulation, and then some very focal 30 μ ablation to areas of residual lines still visualized through the pinpoint bleeding. Similarly, full-field ablative resurfacing can be very reliable for significant wrinkles and creping in the lower eyelid skin--where often a single treatment of 80 μ ablation, 50 μ coagulation can lead to a nice improvement. Standardized digital imaging revealed significant improvement in deeply etched rhytides without significant adverse events. For appropriately selected patients requiring perioral (or periorbital) rejuvenation, full-field ablative erbium resurfacing is safe, efficacious and merits consideration.

Superficial characterization of titanium league when submitted to abrasive blasting

International Nuclear Information System (INIS)

Suzuki, L.Y.; Leite, I.V.; Szesz, E.M.; Siqueira, C.J.M.

2010-01-01

Commercially pure titanium and some of its alloys exhibit a good biocompatibility. These characteristics are frequently used in the manufacture of orthopedic and dental implants. It is possible to modify its surface making it the bioactive using various methods, such as deposition of hydroxyapatite by plasma spray and increasing the roughness of the surface by abrasive blasting. This work is to modify the surface of titanium alloy Ti6Al4V ELI (ASTM F136: 02a) for abrasive blasting and study the morphology, crystallographic phases and the mechanical characteristics of the surface obtained. For such purpose, SEM images, diffraction of X-rays and tests of risk produced by nanoindenter. The sandblasting was done using alumina powder and blasting time of 6s. The morphology of the surfaces of Ti6Al4V ELI changed after sandblasting with increased roughness. It is possible to conclude that after sandblasting the titanium surface do not have a ductile behavior. (author)

A study of angular dependence in the ablation rate of polymers by nanosecond pulses

Science.gov (United States)

Pedder, James E. A.; Holmes, Andrew S.

2006-02-01

Measurements of ablation rate have traditionally been carried out only at normal incidence. However, in real-world applications ablation is often carried out at oblique angles, and it is useful to have prior knowledge of the ablation rate in this case. Detailed information about the angular dependence is also important for the development of ablation simulation tools, and can provide additional insight into the ablation mechanism. Previously we have reported on the angular dependence of direct-write ablation at 266 nm wavelength in solgel and polymer materials. In this paper we present a systematic study of angular dependence for excimer laser ablation of two polymer materials of interest for microfabrication: polycarbonate and SU8 photoresist. The results are used to improve simulation models to aid in mask design.

Influence of Utilization of High-Volumes of Class F Fly Ash on the Abrasion Resistance of Concrete

Directory of Open Access Journals (Sweden)

William PRINCE

2007-01-01

Full Text Available Utilization of large volumes of fly ash in various concrete applications is a becoming a more general practice in an efforts towards using large quantities of fly ash. Around the world, Class C or Class F or both as available have been used in high volumes in cement-based materials. In India, majority of fly generated is of Class F type as per ASTM C 618. Yearly fly ash generation in India is approximately 95 million tonnes. Out of which around 15-20% is utilized in cement production and cement/concrete related activities. In order to increase its percentage utilization, an investigation was carried out to use it in concrete.In this paper, abrasion resistance of high volume fly ash (HVFA concretes made with 35, 45, 55, and 65% of cement replacement was evaluated in terms of its relation with compressive strength. Comparison was made between ordinary Portland cement and fly ash concrete. Test results indicated that abrasion resistance of concrete having cement replacement up to 35 percent was comparable to the normal concrete mix with out fly ash. Beyond 35% cement replacement, fly ash concretes exhibited slightly lower resistance to abrasion relative to non-fly ash concretes. Test results further indicated that abrasion resistance of concrete is closely related with compressive strength, and had a very good correlation between abrasion resistance and compressive strength (R2 value between 0.9018 and 0.9859 depending upon age.

CT-guided Bipolar and Multipolar Radiofrequency Ablation (RF Ablation) of Renal Cell Carcinoma: Specific Technical Aspects and Clinical Results

Energy Technology Data Exchange (ETDEWEB)

Sommer, C. M., E-mail: christof.sommer@med.uni-heidelberg.de [University Hospital Heidelberg, INF 110, Department of Diagnostic and Interventional Radiology (Germany); Lemm, G.; Hohenstein, E. [Minimally Invasive Therapies and Nuclear Medicine, SLK Kliniken Heilbronn GmbH, Clinic for Radiology (Germany); Bellemann, N.; Stampfl, U. [University Hospital Heidelberg, INF 110, Department of Diagnostic and Interventional Radiology (Germany); Goezen, A. S.; Rassweiler, J. [Clinic for Urology, SLK Kliniken Heilbronn GmbH (Germany); Kauczor, H. U.; Radeleff, B. A. [University Hospital Heidelberg, INF 110, Department of Diagnostic and Interventional Radiology (Germany); Pereira, P. L. [Minimally Invasive Therapies and Nuclear Medicine, SLK Kliniken Heilbronn GmbH, Clinic for Radiology (Germany)

2013-06-15

Purpose. This study was designed to evaluate the clinical efficacy of CT-guided bipolar and multipolar radiofrequency ablation (RF ablation) of renal cell carcinoma (RCC) and to analyze specific technical aspects between both technologies. Methods. We included 22 consecutive patients (3 women; age 74.2 {+-} 8.6 years) after 28 CT-guided bipolar or multipolar RF ablations of 28 RCCs (diameter 2.5 {+-} 0.8 cm). Procedures were performed with a commercially available RF system (Celon AG Olympus, Berlin, Germany). Technical aspects of RF ablation procedures (ablation mode [bipolar or multipolar], number of applicators and ablation cycles, overall ablation time and deployed energy, and technical success rate) were analyzed. Clinical results (local recurrence-free survival and local tumor control rate, renal function [glomerular filtration rate (GFR)]) and complication rates were evaluated. Results. Bipolar RF ablation was performed in 12 procedures and multipolar RF ablation in 16 procedures (2 applicators in 14 procedures and 3 applicators in 2 procedures). One ablation cycle was performed in 15 procedures and two ablation cycles in 13 procedures. Overall ablation time and deployed energy were 35.0 {+-} 13.6 min and 43.7 {+-} 17.9 kJ. Technical success rate was 100 %. Major and minor complication rates were 4 and 14 %. At an imaging follow-up of 15.2 {+-} 8.8 months, local recurrence-free survival was 14.4 {+-} 8.8 months and local tumor control rate was 93 %. GFR did not deteriorate after RF ablation (50.8 {+-} 16.6 ml/min/1.73 m{sup 2} before RF ablation vs. 47.2 {+-} 11.9 ml/min/1.73 m{sup 2} after RF ablation; not significant). Conclusions. CT-guided bipolar and multipolar RF ablation of RCC has a high rate of clinical success and low complication rates. At short-term follow-up, clinical efficacy is high without deterioration of the renal function.

Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives: Synthesis and the effects on chemical mechanical polishing (CMP) performances of sapphire wafers

Energy Technology Data Exchange (ETDEWEB)

Liu, Tingting; Lei, Hong, E-mail: hong_lei2005@aliyun.com

2017-08-15

Highlights: • The novel Nd{sup 3+}-doped colloidal SiO{sub 2} abrasives were synthesized by seed-introduced method. • The Nd{sup 3+}-doped colloidal SiO{sub 2} abrasives exhibited lower Ra and higher MRR on sapphire during CMP. • The cores SiO{sub 2} were coated by the shells (SiO{sub 2}, Nd{sub 2}Si{sub 2}O{sub 7} and Nd(OH){sub 3}) via chemical bonds and hydrogen bonds. • XPS analysis revealed the solid-state chemical reaction between Nd{sup 3+}-doped colloidal SiO{sub 2} abrasives and sapphire during CMP. - Abstract: Abrasive is one of the most important factors in chemical mechanical polishing (CMP). In order to improve the polishing qualities of sapphire substrates, the novel Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives were prepared by seed-induced growth method. In this work, there were a series of condensation reactions during the synthesis process of Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives and the silica cores were coated by shells (which contains SiO{sub 2}, Nd{sub 2}Si{sub 2}O{sub 7} and Nd(OH){sub 3}) via chemical bonds and hydrogen bonds in the Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives, which made the composite abrasives’ core-shell structure more sTable Scanning electron microscopy (SEM) showed that Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives were spherical and uniform in size. And the acting mechanisms of Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives on sapphire in CMP were investigated. Time-of-flight secondary ion mass spectroscopy (TOF-SIMS) analysis and X-ray photoelectron spectroscopy (XPS) analysis demonstrated that the solid-state chemical reactions between the shells (which contained SiO{sub 2}, Nd{sub 2}Si{sub 2}O{sub 7} and Nd(OH){sub 3}) of Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives and the sapphire occurred during the CMP process. Furthermore, Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives exhibited lower surface roughness and

Abrasive wear mechanisms and surface layer structure of refractory materials after mechanical working

International Nuclear Information System (INIS)

Milman, Y.V.; Lotsko, D.V.

1989-01-01

The mechanisms of abrasive wear and surface layer structure formation after different kinds of mechanical working are considered in terms of fracture and plastic deformation mechanisms for various refractory materials. The principles for classification of abrasive wear mechanisms are proposed, the four types of wear mechanisms are distinguished for various combinations of fractures and plastic deformation types. The concept of characteristic deformation temperature t * (knee temperature) is used. Detailed examples are given of investigating the surface layer structures in grinded crystals of sapphire and molybdenum. The amorphisation tendency of the thinnest surface layer while mechanical polishing is discussed separately. 19 refs., 11 figs., 2 tabs. (Author)

Effect of Twisted Fiber Anisotropy in Cardiac Tissue on Ablation with Pulsed Electric Fields.

Directory of Open Access Journals (Sweden)

Fei Xie

Full Text Available Ablation of cardiac tissue with pulsed electric fields is a promising alternative to current thermal ablation methods, and it critically depends on the electric field distribution in the heart.We developed a model that incorporates the twisted anisotropy of cardiac tissue and computed the electric field distribution in the tissue. We also performed experiments in rabbit ventricles to validate our model. We find that the model agrees well with the experimentally determined ablation volume if we assume that all tissue that is exposed to a field greater than 3 kV/cm is ablated. In our numerical analysis, we considered how tissue thickness, degree of anisotropy, and electrode configuration affect the geometry of the ablated volume. We considered two electrode configurations: two parallel needles inserted into the myocardium ("penetrating needles" configuration and one circular electrode each on epi- and endocardium, opposing each other ("epi-endo" configuration.For thick tissues (10 mm and moderate anisotropy ratio (a = 2, we find that the geometry of the ablated volume is almost unaffected by twisted anisotropy, i.e. it is approximately translationally symmetric from epi- to endocardium, for both electrode configurations. Higher anisotropy ratio (a = 10 leads to substantial variation in ablation width across the wall; these variations were more pronounced for the penetrating needle configuration than for the epi-endo configuration. For thinner tissues (4 mm, typical for human atria and higher anisotropy ratio (a = 10, the epi-endo configuration yielded approximately translationally symmetric ablation volumes, while the penetrating electrodes configuration was much more sensitive to fiber twist.These results suggest that the epi-endo configuration will be reliable for ablation of atrial fibrillation, independently of fiber orientation, while the penetrating electrode configuration may experience problems when the fiber orientation is not consistent

Effect of Twisted Fiber Anisotropy in Cardiac Tissue on Ablation with Pulsed Electric Fields.

Science.gov (United States)

Xie, Fei; Zemlin, Christian W

2016-01-01

Ablation of cardiac tissue with pulsed electric fields is a promising alternative to current thermal ablation methods, and it critically depends on the electric field distribution in the heart. We developed a model that incorporates the twisted anisotropy of cardiac tissue and computed the electric field distribution in the tissue. We also performed experiments in rabbit ventricles to validate our model. We find that the model agrees well with the experimentally determined ablation volume if we assume that all tissue that is exposed to a field greater than 3 kV/cm is ablated. In our numerical analysis, we considered how tissue thickness, degree of anisotropy, and electrode configuration affect the geometry of the ablated volume. We considered two electrode configurations: two parallel needles inserted into the myocardium ("penetrating needles" configuration) and one circular electrode each on epi- and endocardium, opposing each other ("epi-endo" configuration). For thick tissues (10 mm) and moderate anisotropy ratio (a = 2), we find that the geometry of the ablated volume is almost unaffected by twisted anisotropy, i.e. it is approximately translationally symmetric from epi- to endocardium, for both electrode configurations. Higher anisotropy ratio (a = 10) leads to substantial variation in ablation width across the wall; these variations were more pronounced for the penetrating needle configuration than for the epi-endo configuration. For thinner tissues (4 mm, typical for human atria) and higher anisotropy ratio (a = 10), the epi-endo configuration yielded approximately translationally symmetric ablation volumes, while the penetrating electrodes configuration was much more sensitive to fiber twist. These results suggest that the epi-endo configuration will be reliable for ablation of atrial fibrillation, independently of fiber orientation, while the penetrating electrode configuration may experience problems when the fiber orientation is not consistent across the

A study on practical use of underwater abrasive water jet cutting

Science.gov (United States)

Yamaguchi, Hitoshi; Demura, Kenji

1993-09-01

The practicality of underwater abrasive water jet cutting technology was studied in experiments. A study of abrasives in slurried form showed that optimum polymer concentration can be selected to suit underwater conditions. For the long-distance transport of slurry from the ocean surface to the ocean floor, a direct supply system by hose proved to be practical. This system takes advantage of the insolubility of the slurry in water due to a difference in specific gravity. For cutting thick steel plate at great ocean depths, a simulation with a pressurized container revealed the requirements for actual cutting. Confirmation of remote cutting operations will become the most important technology in field applications. Underwater sound vibration characteristics were found to change significantly in direct response to modifications in cutting conditions. This will be important basic data to develop an effective sensoring method.

Water spray assisted ultrashort laser pulse ablation

International Nuclear Information System (INIS)

Silvennoinen, M.; Kaakkunen, J.J.J.; Paivasaari, K.; Vahimaa, P.

2013-01-01

Highlights: ► We show the novel method to use multibeam processing with ultrashort pulses efficiently. ► Sprayed thin water layer on ablation zone enhances ablation rate and quality. ► In some cases this method also enables ablation of the deeper and straighter holes compared to ones made without the water layer. ► Method also makes possible to directly write features without the self-organizing structures. - Abstract: We have studied femtosecond ablation under sprayed thin water film and its influence and benefits compared with ablation in the air atmosphere. These have been studied in case of the hole and the groove ablation using IR femtosecond laser. Water enhances the ablation rate and in some situations it makes possible to ablate the holes with a higher aspect ratio. While ablating the grooves, the water spray allows using the high fluences without the generation of the self-organized structures.

Domain Endurants: An Analysis and Description Process Model

DEFF Research Database (Denmark)

Bjørner, Dines

2014-01-01

We present a summary, Sect. 2, of a structure of domain analysis and description concepts: techniques and tools. And we link, in Sect. 3, these concepts, embodied in domain analysis prompts and domain description prompts, in a model of how a diligent domain analyser cum describer would use them. We...

Adding Curvature to Minimum Description Length Shape Models

DEFF Research Database (Denmark)

Thodberg, Hans Henrik; Ólafsdóttir, Hildur

2003-01-01

The Minimum Description Length (MDL) approach to shape modelling seeks a compact description of a set of shapes in terms of the coordinates of marks on the shapes. It has been shown that the mark positions resulting from this optimisation to a large extent solve the so-called point correspondence...

The measurement of the velocity of abrasive particlesat the suction part of the cutting head

Czech Academy of Sciences Publication Activity Database

Foldyna, Josef; Zeleňák, Michal; Klich, Jiří; Hlaváček, Petr; Sitek, Libor; Říha, Zdeněk

2015-01-01

Roč. 22, č. 6 (2015), s. 1441-1446 ISSN 1330-3651. [Vodní paprsek 2013 - výzkum, vývoj, aplikace. Soláň, Karolinka, 22.10.2013-24.10.2013] R&D Projects: GA MŠk ED2.1.00/03.0082; GA MŠk(CZ) LO1406 Institutional support: RVO:68145535 Keywords : abrasive water jet * velocity of abrasive particles * shadowgraphy Subject RIV: JQ - Machines ; Tools Impact factor: 0.464, year: 2015 http://www.tehnicki-vjesnik.com/web/public/archive

The effect of ethanol infusion on the size of the ablated lesion in radiofrequency thermal ablation: A pilot study

International Nuclear Information System (INIS)

Kim, Young Sun; Rhim, Hyun Chul; Koh, Byung Hee; Cho, On Koo; Seo, Heung Suk; Kim, Yong Soo; Joo, Kyoung Bin

2001-01-01

To assess the effect of ethanol infusion on the size of ablated lesion during radiofrequency (RF) thermal ablation. We performed an ex vivo experimental study using a total of 15 pig livers. Three groups were designed: 1)normal control (n=10), 2) saline infusion (n=10) 3) ethanol infusion (n=10). Two radiofrequency ablations were done using a 50 watt RF generator and a 15 guage expandable elections with four prongs in each liver. During ablation for 8 minutes, continuous infusion of fluid at a rate of 0.5 ml/min through the side arm of electrode was performed. We checked the frequency of the 'impeded-out' phenomenon due to abrupt increase of impedance during ablation. Size of ablated lesion was measured according to length, width, height, and subsequently volume after the ablations. The sizes of the ablated lesions were compared between the three groups. 'Impeded-out' phenomenon during ablation was noted 4 times in control group, although that never happened in saline or ethanol infusion groups. There were significant differences in the volumes of ablated lesions between control group (10.62 ± 1.45 cm 3 ) and saline infusion group (15.33 ± 2.47 cm 3 ), and saline infusion group and ethanol infusion group (18.78 ± 3.58 cm 3 ) (p<0.05). Fluid infusion during radiofrequency thermal ablation decrease a chance of charming and increase the volume of the ablated lesion. Ethanol infusion during ablation may induce larger volume of ablated lesion than saline infusion.

Simulation of the impact of refractive surgery ablative laser pulses with a flying-spot laser beam on intrasurgery corneal temperature.

Science.gov (United States)

Shraiki, Mario; Arba-Mosquera, Samuel

2011-06-01

To evaluate ablation algorithms and temperature changes in laser refractive surgery. The model (virtual laser system [VLS]) simulates different physical effects of an entire surgical process, simulating the shot-by-shot ablation process based on a modeled beam profile. The model is comprehensive and directly considers applied correction; corneal geometry, including astigmatism; laser beam characteristics; and ablative spot properties. Pulse lists collected from actual treatments were used to simulate the temperature increase during the ablation process. Ablation efficiency reduction in the periphery resulted in a lower peripheral temperature increase. Steep corneas had lesser temperature increases than flat ones. The maximum rise in temperature depends on the spatial density of the ablation pulses. For the same number of ablative pulses, myopic corrections showed the highest temperature increase, followed by myopic astigmatism, mixed astigmatism, phototherapeutic keratectomy (PTK), hyperopic astigmatism, and hyperopic treatments. The proposed model can be used, at relatively low cost, for calibration, verification, and validation of the laser systems used for ablation processes and would directly improve the quality of the results.

Effects of enamel abrasion, salivary pellicle, and measurement angle on the optical assessment of dental erosion

Science.gov (United States)

Lussi, Adrian; Bossen, Anke; Höschele, Christoph; Beyeler, Barbara; Megert, Brigitte; Meier, Christoph; Rakhmatullina, Ekaterina

2012-09-01

The present study assessed the effects of abrasion, salivary proteins, and measurement angle on the quantification of early dental erosion by the analysis of reflection intensities from enamel. Enamel from 184 caries-free human molars was used for in vitro erosion in citric acid (pH 3.6). Abrasion of the eroded enamel resulted in a 6% to 14% increase in the specular reflection intensity compared to only eroded enamel, and the reflection increase depended on the erosion degree. Nevertheless, monitoring of early erosion by reflection analysis was possible even in the abraded eroded teeth. The presence of the salivary pellicle induced up to 22% higher reflection intensities due to the smoothing of the eroded enamel by the adhered proteins. However, this measurement artifact could be significantly minimized (pmeasurement angles from 45 to 60 deg did not improve the sensitivity of the analysis at late erosion stages. The applicability of the method for monitoring the remineralization of eroded enamel remained unclear in a demineralization/remineralization cycling model of early dental erosion in vitro.

High-intensity interstitial ultrasound for thermal ablation of focal cancer targets in prostate

Science.gov (United States)

Salgaonkar, Vasant A.; Scott, Serena; Kurhanewicz, John; Diederich, Chris J.

2017-03-01

Recent advances in image based techniques such as multi-parametric MRI (MP-MRI) can provide precise targeting of focal disease in the prostate. Thermal ablation of such cancer targets while avoiding rectum, urethra, neurovascular bundles (NVB) and sphincter is clinically challenging. The approach described here employs multi-element ultrasound linear arrays designed for transperineal placement within prostate. They consist of independently powered sectored tubular transducers (6.5 - 8.0 MHz) that provide spatial control of energy deposition in angle and length. Volumetric ablation strategies were investigated through patient-specific biothermal models based on Pennes bioheat transfer equation. The acoustic and heat transfer models used here have been validated in several previous simulation and experimental studies. Focal disease sites in prostate were identified through multi-parametric MR images of representative patient cases (n=3). Focal cancer lesions and critical anatomy (prostate, urethra, rectum, bladder, seminal vesicles) were manually segmented (Mimics, Materialise) and converted to 3D finite element meshes (3-Matic, Materialise). The chosen test cases consisted of patients with medium and large sized glands and models of bulk tissue ablation covered volumes in a single quadrant in posterior prostate, hemi-gland targets and "hockey-stick" targets (lesions in three quadrants). Ultrasound applicator placement was determined such that devices were positioned along the prostate periphery while avoiding surrounding anatomy. Transducer sector angles were chosen based on applicator location within limits of fabrication practicability. Thermal models were numerically solved using finite element methods (FEM) in COMSOL Multiphysics. Temperature and thermal dose distributions were calculated to determine treated volumes (> 240 CEM43C, >52 °C) and safety profiles (<10 CEM43C, <45 °C) for nerve, rectal and urethral sparing. Modeling studies indicated that focal

Simulation of radiofrequency ablation in real human anatomy.

Science.gov (United States)

Zorbas, George; Samaras, Theodoros

2014-12-01

The objective of the current work was to simulate radiofrequency ablation treatment in computational models with realistic human anatomy, in order to investigate the effect of realistic geometry in the treatment outcome. The body sites considered in the study were liver, lung and kidney. One numerical model for each body site was obtained from Duke, member of the IT'IS Virtual Family. A spherical tumour was embedded in each model and a single electrode was inserted into the tumour. The same excitation voltage was used in all cases to underline the differences in the resulting temperature rise, due to different anatomy at each body site investigated. The same numerical calculations were performed for a two-compartment model of the tissue geometry, as well as with the use of an analytical approximation for a single tissue compartment. Radiofrequency ablation (RFA) therapy appears efficient for tumours in liver and lung, but less efficient in kidney. Moreover, the time evolution of temperature for a realistic geometry differs from that for a two-compartment model, but even more for an infinite homogenous tissue model. However, it appears that the most critical parameters of computational models for RFA treatment planning are tissue properties rather than tissue geometry. Computational simulations of realistic anatomy models show that the conventional technique of a single electrode inside the tumour volume requires a careful choice of both the excitation voltage and treatment time in order to achieve effective treatment, since the ablation zone differs considerably for various body sites.

FE simulation of the indentation deformation of SiC modified vinylester composites in respect to their abrasive wear performance

Directory of Open Access Journals (Sweden)

2008-10-01

Full Text Available The abrasive sliding friction and wear behaviours of silicon carbide (SiC filled vinylester (VE composites were investigated. The average grain size of the incorporated SiC particles was varied, holding the volume content of them in every case at 16 vol%. Mechanical properties (hardness, compression modulus, yield stress of the filled and neat VE were determined. The tribological properties were investigated in block (composite – on – ring (steel test configuration. The steel counter bodies were covered with abrasive papers of different graining. Coefficient of friction (COF and specific wear rate of the VE + SiC composites were determined. It was observed that the wear resistance increases with increasing average filler grain size and with decreasing abrasiveness of the counter surface. The COF of the VE + SiC composites is independent of the size of the incorporated particles, but it is strongly influenced by the abrasiveness of the counter body. The worn surfaces of the VE + SiC systems were analysed in scanning electron microscope (SEM to deduce the typical wear mechanisms. The size effect of the SiC filler particles onto the abrasive wear characteristics was investigated by assuming that the roughness peaks of the abrasive paper and the indenter of the microhardness test cause similar micro scaled contact deformations in the composites. Therefore FE method was used to simulate the micro scaled deformation process in the VE + SiC systems during microindentation tests. The FE results provided valuable information on how to explain the size effect of the incorporated SiC filler.

Three-body abrasive wear behaviour of metastable spheroidal carbide cast irons with different chromium contents

Energy Technology Data Exchange (ETDEWEB)

Efremenko, Vasily; Pastukhova, Tatiana; Chabak, Yuliia; Efremenko, Alexey [Pryazovskyi State Technical Univ., Mariupol (Ukraine); Shimizu, Kazumichi; Kusumoto, Kenta [Muroran Institute of Technology, Hokkaido (Japan); Brykov, Michail [Zaporozhye National Technical Univ., Zaporozhye (Ukraine)

2018-02-15

The effect of heat treatment and chromium contents (up to 9.1 wt.%) on the wear resistance of spheroidal carbide cast iron (9.5 wt.% V) was studied using optical and scanning electron microscopy, X-ray diffractometry, dilatometry and three-body abrasive testing. It was found that quenching from 760 C and 920 C improved the alloys' wear resistance compared to the as-cast state due to the formation of metastable austenite transforming into martensite under abrasion. The wear characteristics of alloys studied are 1.6 - 2.3 times higher than that of reference cast iron (12 wt.% V) having stable austenitic matrix. Chromium addition decreases surface damage due to the formation of M{sub 7}C{sub 3} carbides, while it reduces wear resistance owing to austenite stabilization to abrasion-induced martensite transformation. The superposition of these factors results in decreasing the alloys' wear behaviour with chromium content increase.

Abrasive wear resistance and microstructure of Ni-Cr-B-Si hardfacing alloys with additions of Al, Nb, Mo, Fe, Mn and C

International Nuclear Information System (INIS)

Berns, H.; Fischer, A.; Theisen, W.

1987-01-01

The development of new Ni-base hardfacing alloys for filler wire welding or metal spraying should result in materials with a good resistance against high temperature corrosion and abrasive wear. The first step is to design microstructures, which obtain a satisfactory abrasive wear behaviour at room temperature. Thus, different alloys are melted and scrutinized as to their microstructure and their abrasive wear resistance in laboratory. Compared to commercial Ni-base hardfacing alloys they show a higher volume fraction of coarse hard phases due to the additional, initial solidification of Nb-carbides and Cr-, and Mo-borides. Thus, the abrasive wear resistance is improved. For hard abrasive particles, such as corundum, the Ni-base alloys are more wear resistant than harder Fe-base alloys investigate earlier. This is due to the tougher Ni metal matrix that results in microcracking not to be the most significantly acting wear mechanism

Randomized Controlled Trial to Explore the Effect of Experimental Low Abrasivity Dentifrices on Enamel Gloss and Smoothness, and the Build-up of Extrinsic Tooth Stain.

Science.gov (United States)

Milleman, Kimberly R; Milleman, Jeffery L; Young, Sarah; Parkinson, Charles

2017-06-01

To evaluate and compare examiner-assessed changes in enamel gloss, extrinsic dental stain, and surface smoothness following one, two, four, and eight weeks of twice-daily use of an experimental low abrasivity desensitizing dentifrice (relative dentin abrasivity [RDA] ~40) containing 5% sodium tripolyphosphate (STP) chemical cleaning agent and 1% aluminum trioxide abrasive. This was compared with an ultra-low abrasivity dentifrice (5% STP only; RDA ~13), a moderate abrasivity fluoride dentifrice (RDA ~80), and a higher abrasivity marketed whitening dentifrice (RDA ~142). This was a single-center, examiner-blind, randomized, controlled, parallel group study in healthy adults stratified by gloss score and age. Following a washout period with a conventional silica abrasive dentifrice, subjects received a dental scale and polish and were randomized to treatment. Subjects brushed their teeth for two minutes, twice daily, with their assigned dentifrice. Enamel gloss was assessed visually by comparing the facial surfaces of the maxillary incisors to the Sturzenberger gloss standards. Extrinsic dental stain was measured on the 12 anterior teeth (facial and lingual) using the Macpherson modification of the Lobene Stain Index (MLSI). Tooth smoothness was assessed using scanning electron microscope (SEM) analysis of a silicone impression of the central incisors. Of 120 screened subjects, 95 were randomized to the study. Subjects using the low abrasivity aluminum trioxide/STP dentifrice demonstrated statistically significant (p tooth smoothness, at Week 8, statistically significant increases in surface smoothness were observed for most treatment groups compared to baseline (p tooth gloss compared to a non-alumina ultra-low abrasivity STP-containing dentifrice, and moderate and high abrasivity dentifrices, over an eight-week period.

Rock Abrasion and Ventifact Formation on Mars from Field Analog, Theoretical, and Experimental Studies