scholarly journals A Strategy for Achieving Smooth Filamentation Cutting of Transparent Materials with Ultrafast Lasers

2021 ◽  
Vol 11 (4) ◽  
pp. 1732
Author(s):  
Vladimir N. Tokarev ◽  
Igor V. Melnikov
Keyword(s):  
Ultrafast Lasers ◽  
Necessary Conditions ◽  
Tempered Glass ◽  
Practical Applications ◽  
Average Laser Power ◽  
Moving Beam ◽  
Transparent Materials ◽  
Very High ◽  
Cutting Speeds ◽  
Good Agreement

A strategy is proposed for achieving a practically important mode of laser processing—a so-called “smooth” laser filamentation cutting (LFC) of transparent materials by a moving beam of a pulse-periodic pico- or subpicosecond laser. With such cutting, the surface of the sidewalls of the cuts have a significantly improved smoothness, and, as a result, the laser-cut plates have increased resistance to damage and cracking due to mechanical impacts during their subsequent use. According to the proposed analytical model, for the case when each filament is formed only by a single laser pulse, the strategy of such cutting is defined by a set of necessary conditions, whose implementation requires, in turn, a certain selection and matching with each other of irradiation parameters (pulse duration and energy, repetition rate, pitch of filaments following) and of material parameters—thermal, optical and mechanical strength constants. The model shows good agreement with experiments on sapphire and tempered glass. Besides, LFC modes are also predicted that provide very high cutting speeds of the order of 1–25 m/s or more, or allow cutting with an extremely low average laser power, but still at a speed acceptable for practical applications.

scholarly journals Progress in ultrafast laser processing and future prospects

Nanophotonics ◽  
2017 ◽  
Vol 6 (2) ◽  
pp. 393-413 ◽  
Author(s):  
Koji Sugioka
Keyword(s):  
Laser Processing ◽  
Ultrafast Lasers ◽  
Industrial Applications ◽  
Femtosecond Laser Pulses ◽  
Ultrafast Laser ◽  
Heat Diffusion ◽  
Multiphoton Absorption ◽  
Future Prospects ◽  
Practical Applications ◽  
Transparent Materials

AbstractThe unique characteristics of ultrafast lasers have rapidly revolutionized materials processing after their first demonstration in 1987. The ultrashort pulse width of the laser suppresses heat diffusion to the surroundings of the processed region, which minimizes the formation of a heat-affected zone and thereby enables ultrahigh precision micro- and nanofabrication of various materials. In addition, the extremely high peak intensity can induce nonlinear multiphoton absorption, which extends the diversity of materials that can be processed to transparent materials such as glass. Nonlinear multiphoton absorption enables three-dimensional (3D) micro- and nanofabrication by irradiation with tightly focused femtosecond laser pulses inside transparent materials. Thus, ultrafast lasers are currently widely used for both fundamental research and practical applications. This review presents progress in ultrafast laser processing, including micromachining, surface micro- and nanostructuring, nanoablation, and 3D and volume processing. Advanced technologies that promise to enhance the performance of ultrafast laser processing, such as hybrid additive and subtractive processing, and shaped beam processing are discussed. Commercial and industrial applications of ultrafast laser processing are also introduced. Finally, future prospects of the technology are given with a summary.

Dislocation structures around SiO2 Particles in aged Cu-Cr-SiO2

1978 ◽  
Vol 36 (1) ◽  
pp. 594-595
Author(s):  
N.J. Long ◽  
M.H. Loretto ◽  
C.H. Lloyd
Keyword(s):  
Flow Stress ◽  
Single Crystals ◽  
Room Temperature ◽  
Thin Foil ◽  
Age Hardening ◽  
Dispersion Strengthening ◽  
Accurate Picture ◽  
The Matrix ◽  
Very High ◽  
Good Agreement

IntroductionThere have been several t.e.m. studies (1,2,3,4) of the dislocation arrangements in the matrix and around the particles in dispersion strengthened single crystals deformed in single slip. Good agreement has been obtained in general between the observed structures and the various theories for the flow stress and work hardening of this class of alloy. There has been though some difficulty in obtaining an accurate picture of these arrangements in the case when the obstacles are large (of the order of several 1000's Å). This is due to both the physical loss of dislocations from the thin foil in its preparation and to rearrangement of the structure on unloading and standing at room temperature under the influence of the very high localised stresses in the vicinity of the particles (2,3).This contribution presents part of a study of the Cu-Cr-SiO2 system where age hardening from the Cu-Cr and dispersion strengthening from Cu-Sio2 is combined.

scholarly journals Separate Universe calibration of the dependence of halo bias on cosmic web anisotropy

2020 ◽  
Vol 499 (3) ◽  
pp. 4418-4431 ◽  
Author(s):  
Sujatha Ramakrishnan ◽  
Aseem Paranjape
Keyword(s):  
Dark Matter ◽  
High Precision ◽  
Gaussian Distribution ◽  
Initial Perturbation ◽  
Analytical Framework ◽  
Web Environment ◽  
Wide Range ◽  
Galaxy Assembly ◽  
Very High ◽  
Good Agreement

ABSTRACT We use the Separate Universe technique to calibrate the dependence of linear and quadratic halo bias b1 and b2 on the local cosmic web environment of dark matter haloes. We do this by measuring the response of halo abundances at fixed mass and cosmic web tidal anisotropy α to an infinite wavelength initial perturbation. We augment our measurements with an analytical framework developed in earlier work that exploits the near-lognormal shape of the distribution of α and results in very high precision calibrations. We present convenient fitting functions for the dependence of b1 and b2 on α over a wide range of halo mass for redshifts 0 ≤ z ≤ 1. Our calibration of b2(α) is the first demonstration to date of the dependence of non-linear bias on the local web environment. Motivated by previous results that showed that α is the primary indicator of halo assembly bias for a number of halo properties beyond halo mass, we then extend our analytical framework to accommodate the dependence of b1 and b2 on any such secondary property that has, or can be monotonically transformed to have, a Gaussian distribution. We demonstrate this technique for the specific case of halo concentration, finding good agreement with previous results. Our calibrations will be useful for a variety of halo model analyses focusing on galaxy assembly bias, as well as analytical forecasts of the potential for using α as a segregating variable in multitracer analyses.

scholarly journals Drought Vulnerability Indices in Mexico

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1671 ◽  
Author(s):  
David Ortega-Gaucin ◽  
Jesús de la Cruz Bartolón ◽  
Heidy Castellano Bahena
Keyword(s):  
Social Economic ◽  
Necessary Conditions ◽  
Environmental Indicators ◽  
Mitigation Strategies ◽  
Social Programs ◽  
Drought Vulnerability ◽  
Public Programs ◽  
Analytic Procedure ◽  
The Impact ◽  
Very High

Drought is one of the most harmful hydro climatic threats to society. Mexico has been historically affected by recurring and long-lasting droughts that have severely impacted society and the economy. Consequently, public programs and policies have been developed in order to reduce the country’s vulnerability to drought, hence the importance of identifying the spatial distribution and the dimension—even in relative terms only—of vulnerability in different regions from social, economic, and environmental perspectives. This article presents a method for obtaining indices and maps of vulnerability to drought in Mexico; indices and maps are based on a set of socioeconomic and environmental indicators that the method combines using an objective analytic procedure that identifies the most vulnerable states and municipalities from social, economic, and environmental perspectives, all of which converge in overall vulnerability to drought. The results obtained indicate that 38.9% of total Mexican population inhabits municipalities with high and very high degrees of overall vulnerability to drought. For this reason, it is necessary to continue implementing actions and preventive and mitigation strategies via public policies and social programs aimed at decreasing the country’s vulnerability to the occurrence of drought events. This is the only way to facilitate the necessary conditions to reduce the impact of drought and to decrease people’s vulnerability to this phenomenon.

scholarly journals The high Arctic in extreme winters: vortex, temperature, and MLS and ACE-FTS trace gas evolution

2008 ◽  
Vol 8 (3) ◽  
pp. 505-522 ◽  
Author(s):  
G. L. Manney ◽  
W. H. Daffer ◽  
K. B. Strawbridge ◽  
K. A. Walker ◽  
C. D. Boone ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Lower Stratosphere ◽  
High Arctic ◽  
Trace Gas ◽  
Satellite Measurements ◽  
Broadband Emission ◽  
Gas Measurements ◽  
Chemistry Experiment ◽  
Very High ◽  
Good Agreement

Abstract. The first three Arctic winters of the ACE mission represented two extremes of winter variability: Stratospheric sudden warmings (SSWs) in 2004 and 2006 were among the strongest, most prolonged on record; 2005 was a record cold winter. Canadian Arctic Atmospheric Chemistry Experiment (ACE) Validation Campaigns were conducted at Eureka (80° N, 86° W) during each of these winters. New satellite measurements from ACE-Fourier Transform Spectrometer (ACE-FTS), Sounding of the Atmosphere using Broadband Emission Radiometry (SABER), and Aura Microwave Limb Sounder (MLS), along with meteorological analyses and Eureka lidar temperatures, are used to detail the meteorology in these winters, to demonstrate its influence on transport, and to provide a context for interpretation of ACE-FTS and validation campaign observations. During the 2004 and 2006 SSWs, the vortex broke down throughout the stratosphere, reformed quickly in the upper stratosphere, and remained weak in the middle and lower stratosphere. The stratopause reformed at very high altitude, near 75 km. ACE measurements covered both vortex and extra-vortex conditions in each winter, except in late-February through mid-March 2004 and 2006, when the strong, pole-centered vortex that reformed after the SSWs resulted in ACE sampling only inside the vortex in the middle through upper stratosphere. The 2004 and 2006 Eureka campaigns were during the recovery from the SSWs, with the redeveloping vortex over Eureka. 2005 was the coldest winter on record in the lower stratosphere, but with an early final warming in mid-March. The vortex was over Eureka at the start of the 2005 campaign, but moved away as it broke up. Disparate temperature profile structure and vortex evolution resulted in much lower (higher) temperatures in the upper (lower) stratosphere in 2004 and 2006 than in 2005. Satellite temperatures agree well with lidar data up to 50–60 km, and ACE-FTS, MLS and SABER show good agreement in high-latitude temperatures throughout the winters. Consistent with a strong, cold upper stratospheric vortex and enhanced radiative cooling after the SSWs, MLS and ACE-FTS trace gas measurements show strongly enhanced descent in the upper stratospheric vortex in late January through March 2006 compared to that in 2005.

scholarly journals Pd/FER vs Pd/SSZ-13 Passive NOx Adsorbers: Adsorbate-controlled Location of Atomically Dispersed Pd(II) in FER Determines High Activity and Stability

2020 ◽  
Author(s):  
Konstantin Khivantsev ◽  
Xinyi Wei ◽  
Libor Kovarik ◽  
Nicholas R. Jaegers ◽  
Eric D. Walter ◽  
...  
Keyword(s):  
Low Temperature ◽  
Beneficial Effect ◽  
Hot Spots ◽  
Release Behavior ◽  
Hydrothermal Aging ◽  
Practical Applications ◽  
Systematic Exploration ◽  
No Release ◽  
Co Concentration ◽  
Very High

<p>Pd-loaded FER and SSZ-13 zeolites as low-temperature passive NOx adsorbers (PNA) are compared under practically relevant conditions. Vehicle cold-start exposes the material to CO under a range of concentrations, necessitating a systematic exploration of the effect of CO on the performance of isolated Pd ions for PNA. NO release temperature of both adsorbers decreases gradually with the increase of CO concentration from a few hundred to a few thousand ppm. This beneficial effect results from local nano-“hot spots” formation during CO oxidation. Dissimilar to Pd/SSZ-13, increasing the CO concentration above ~1,000 ppm improves the NOx storage significantly for Pd/FER, attributed to the presence of a Pd ions in FER γ-site that is shielded from NO<sub>x</sub>. CO mobilizes this Pd atom to the NO<sub>x</sub> accessible position where it becomes active for PNA. This behavior explains the very high resistance of Pd/FER to hydrothermal aging: Pd/FER materials survive hydrothermal aging at 800⁰C in 10% H<sub>2</sub>O vapor for 16 hours with no deterioration in NOx uptake/release behavior. Thus, by allocating Pd ions to the specific microporous pockets in FER, we have produced very hydrothermally stable and active PNA materials with immediate practical applications.<br></p>

Competitive reactions in the irradiation of anthracene + cyclohexane solutions

1959 ◽  
Vol 249 (1256) ◽  
pp. 51-64 ◽  
Keyword(s):  
Radiation Intensity ◽  
Quantitative Agreement ◽  
Radical Scavenger ◽  
Organic Systems ◽  
Low Concentrations ◽  
Radiation Induced ◽  
Experimental Values ◽  
Very High ◽  
Intensity Radiation ◽  
Good Agreement

Anthracene acts as a radical scavenger when present at low concentrations in irradiated hydrocarbons. A study has been made of the effect of radiation intensity and anthracene concentration on G( — A) , the number of anthracene molecules lost per 100 eV of energy absorbed. A theoretical calculation is made of the dependence of G( — A) on radiation intensity 1 and anthracene concentration ( A ), assuming that radiation-induced radicals (R.) are formed at random, and can either disappear by direct combination with one another, or with the anthracene to give RAR or RAAR bridges, or possibly some form of stabilized RA molecules. This theory is in good agreement with the experimental values of G( — A) measured at various low radiation intensities and anthracene concentrations. From the comparison estimates of the reactivity constants are derived. With very high intensity radiation quantitative agreement is less satisfactory, due to the non-steady conditions prevailing in a pulsed beam. The results obtained are compared with previous work on anthracene + hexane and iodine + cyclo hexane mixtures, in which the effect of radiation intensity was not investigated. The results reported here are of interest to the study of reaction kinetics in irradiated organic systems.

Calculation of Punch Force and Maximum Pressure for Tube Extrusion

2000 ◽  
Author(s):  
S.-H. Zhang ◽  
Y.-L. Shang
Keyword(s):  
Upper Bound ◽  
Physical Modeling ◽  
Steel Tube ◽  
Experimental Results ◽  
Maximum Pressure ◽  
Punch Force ◽  
Tube Extrusion ◽  
Tooling System ◽  
Very High ◽  
Good Agreement

Abstract Punch force and maximum pressure for tube extrusion can be predicted with an upper bound theory-based program POLSK. Experiments of steel tube extrusion and wax physical modeling were performed. The punch force and the maximum pressure values were obtained. Comparisons were made among the experimental results, physical modeling results and upper bound predictions. It was found that a medium extrusion coefficient causes the lowest pressure on the tooling system, very low and very high extrusion coefficients can both cause very high pressure. It is proved that the upper bound predictions are in good agreement with the experimental results and the upper bound program is suitable for use of steel tube extrusion design.

scholarly journals New Coefficients of the Minority Carrier Lifetime and Bandgap Narrowing Models in the Transparent Emitter of Thin Film Silicon Solar Cells

2003 ◽  
Vol 26 (1) ◽  
pp. 1-10 ◽  
Author(s):  
A. Zerga ◽  
M. Benosman ◽  
F. Dujardin ◽  
B. Benyoucef ◽  
J-P. Charles
Keyword(s):  
Silicon Solar Cell ◽  
Minority Carrier ◽  
Minority Carrier Lifetime ◽  
Bandgap Narrowing ◽  
Heavy Doping ◽  
High Level ◽  
Band Gap Narrowing ◽  
Very High ◽  
Minority Carriers ◽  
Good Agreement

In this study we have determined new coefficients for the physical model describing the band-gap narrowing and the minority carriers lifetime. This was accomplished according to the doping level of the thin emitter. This model allows us to take into account both the effects of the heavy doping and the majority carrier degeneration for the very high level of doping. The results we obtain by the corrected model are in good agreement with those reported in the literature and in different experiments. They show us the possibility of accurately evaluating the performances for then+psilicon solar cell. This model is then used to introduce a new concept for the thin layer emitter, called transparent emitter.

scholarly journals Low-Profile Spidron Fractal Dipole Antenna with a Ferrite-Loaded Artificial Magnetic Conductor for Manpack Applications

2020 ◽  
Vol 10 (24) ◽  
pp. 8843
Author(s):  
Oh Heon Kwon ◽  
Keum Cheol Hwang
Keyword(s):  
High Frequency ◽  
Dipole Antenna ◽  
Magnetic Conductor ◽  
Very High Frequency ◽  
Artificial Magnetic Conductor ◽  
Received Power ◽  
Low Profile ◽  
Profile Characteristics ◽  
Very High ◽  
Good Agreement

In this paper, a Spidron fractal dipole antenna with a ferrite-loaded artificial magnetic conductor (AMC) is presented. By applying ferrite composed of nickel–zinc with a high permeability value, a compact AMC that operates in the broadband frequency range within the high-frequency/very-high-frequency/ultra-high-frequency (HF/VHF/UHF) bands was designed. A Spidron fractal-shaped dipole antenna with a quasi-self-complementary structure was designed and combined with a miniaturized ferrite-loaded AMC. This allowed the designed AMC-integrated dipole antenna to operate in a wide frequency band, covering the HF/VHF/UHF bands, with low-profile characteristics. A prototype of the proposed Spidron fractal dipole antenna with the AMC was manufactured and measured and found to meet low VSWR (voltage standing wave radios) specifications of <3.5 within the 20–500 MHz bandwidth range. The simulated and measured results are in good agreement. The size of the Spidron fractal dipole antenna with the AMC is 0.03×0.026×0.001λ3 relative to the wavelength of the lowest operating frequency. The received power of the Spidron fractal dipole antenna with the AMC was also measured when it was applied to relatively small applications, such as a manpack in this case.

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