Incandescence Measurement During CO2 Laser Texturing of Silicate Glass

2000 ◽  
Vol 123 (2) ◽  
pp. 376-381 ◽  
Author(s):  
Lei Li ◽  
Ted D. Bennett
Keyword(s):  
Laser Energy ◽  
Heated Surface ◽  
Energy Coupling ◽  
Laser Pulses ◽  
Fictive Temperature ◽  
Emission Data ◽  
New Approach ◽  
Glass Substrates ◽  
Short Time ◽  
Laser Heated

Laser zone texture is a new approach to improve tribology performance of high aerial density disks made with glass substrates. In this process, nanotexture is introduced to the surface by discrete laser pulses. The topography change is due to the elevation of fictive temperature in the short time and high temperature scales that occur through the laser energy coupling with glass. To exercise better control over this thermal process, knowing the temperature field induced by the laser pulse and the timescale of the thermal cycle are very important. In this paper, emission measurements are made from a laser-heated surface of approximately 300 μm2 and temporally resolved to 100 ns. Several emission bands are collected in the visible. From emission data, the extensive heat capacity of the heat affected zone is derived, allowing peak surface temperatures to be determined from the pulse energy. Experimental results are compared with a numerical model to determine the validity of earlier calculations and conclusions.

Temporal Pulse Shaping and Optimization in Ultrafast Laser Ablation of Materials

2003 ◽  
Vol 780 ◽  
Author(s):  
R. Stoian ◽  
S. Winkler ◽  
M. Hildebrand ◽  
M. Boyle ◽  
A. Thoss ◽  
...  
Keyword(s):  
Pulse Shaping ◽  
Laser Energy ◽  
Energy Coupling ◽  
Laser Pulses ◽  
Ultrafast Laser ◽  
Ultrashort Laser Pulses ◽  
Adaptive Optimization ◽  
Ultrafast Laser Pulses ◽  
Energy Delivery ◽  
Optimal Processing

The possibility of phase manipulation and temporal tailoring of ultrashort laser pulses enables new opportunities for optimal processing of materials. Phase-manipulated ultrafast laser pulses allow adapting the laser energy delivery rate to the material properties for optimal processing laying the groundwork for adaptive optimization in materials structuring. Different materials respond with specific reaction pathways to the sudden energy input depending on the efficiency of electron generation and on the ability to release the energy into the lattice. The sequential energy delivery with judiciously chosen pulse trains may induce softening of the material during the initial steps of excitation and change the energy coupling for the subsequent steps. We show that this can result in lower stress, cleaner structures, and allow for a materialdependent optimization process.

scholarly journals Interaction of high intensity picosecond laser pulses with large preformed plasmas

1998 ◽  
Vol 16 (1) ◽  
pp. 101-113 ◽  
Author(s):  
D. Riley ◽  
R.A. Smith ◽  
A. J. MacKinnon ◽  
O. Willi ◽  
M.H.R. Hutchinson
Keyword(s):  
High Intensity ◽  
Laser Energy ◽  
Incident Light ◽  
Picosecond Laser ◽  
Laser Pulses ◽  
Resonance Absorption ◽  
Emission Data ◽  
X Ray ◽  
Spatially Resolved ◽  
Stimulated Brillouin

The interaction of short (1−2 ps) laser pulses with solid targets at irradiances of over 1016 Wcm−2, in the presence of a substantial prepulse has been investigated. High absorption of laser energy is found even at high angles of incidence, with evidence for a resonance absorption peak being found for S, P, and circular polarizations. It is considered that this may be a result of refraction and beam filamentation, which causes loss of distinct polarization. Measurements of hard X-ray emission (∼ 100 keV) confirm a resonance absorption type peak at 45−50°, again for all three cases. Typically, 5−15% of the incident light is back-reflected by stimulated Brillouin scatter, with spatially resolved spectra showing evidence of beam hot-spots at high intensity. The possibility that filamentation and refraction of the beam can explain the lack of polarization dependence in the absorption and hard X-ray emission data is discussed.

scholarly journals Earthquake forecasting and its verification

2005 ◽  
Vol 12 (6) ◽  
pp. 965-977 ◽  
Author(s):  
J. R. Holliday ◽  
K. Z. Nanjo ◽  
K. F. Tiampo ◽  
J. B. Rundle ◽  
D. L. Turcotte
Keyword(s):  
Temporal Variations ◽  
Earthquake Forecasting ◽  
Earthquake Risk ◽  
Decision Threshold ◽  
New Approach ◽  
Pi Method ◽  
Time Prediction ◽  
Short Time ◽  
Large Earthquakes ◽  
Proven Method

Abstract. No proven method is currently available for the reliable short time prediction of earthquakes (minutes to months). However, it is possible to make probabilistic hazard assessments for earthquake risk. In this paper we discuss a new approach to earthquake forecasting based on a pattern informatics (PI) method which quantifies temporal variations in seismicity. The output, which is based on an association of small earthquakes with future large earthquakes, is a map of areas in a seismogenic region ("hotspots'') where earthquakes are forecast to occur in a future 10-year time span. This approach has been successfully applied to California, to Japan, and on a worldwide basis. Because a sharp decision threshold is used, these forecasts are binary--an earthquake is forecast either to occur or to not occur. The standard approach to the evaluation of a binary forecast is the use of the relative (or receiver) operating characteristic (ROC) diagram, which is a more restrictive test and less subject to bias than maximum likelihood tests. To test our PI method, we made two types of retrospective forecasts for California. The first is the PI method and the second is a relative intensity (RI) forecast based on the hypothesis that future large earthquakes will occur where most smaller earthquakes have occurred in the recent past. While both retrospective forecasts are for the ten year period 1 January 2000 to 31 December 2009, we performed an interim analysis 5 years into the forecast. The PI method out performs the RI method under most circumstances.

A Novel Approach to Nanoscale Materials Synthesis Using Industrial Laser Processing of Organosilazane Liquid Precursors

1990 ◽  
Vol 206 ◽  
Author(s):  
Tongsan D. Xiao ◽  
Peter R. Strutt ◽  
Kenneth E. Gonsalves
Keyword(s):  
Ceramic Powder ◽  
Average Diameter ◽  
Current Approach ◽  
Powder Materials ◽  
Materials Synthesis ◽  
Laser Plume ◽  
New Approach ◽  
Novel Approach ◽  
Liquid Precursors ◽  
Short Time

ABSTRACTA new approach has been developed for the synthesis of nanoscale ceramic powder materials from liquid organosilazane precursors. This technique, by exploiting fast kinetic chemical and physical reactions, makes it possible to synthesize significant quantities of material in a relatively short time. In the current approach aerosols of a silazane monomer, (CH3SiHNH)n, (n = 3 or 4), of mol. wt. 280–320, are injected into the beam of a cw industrial CO2 laser to obtain nanoscale ceramic powders. Injection of the aerosol into the laser-beam results in a high-temperature plume. Rapid condensation of the molecular precursor species emerging from the laser plume results in the formation of preceramic polymer particles, with an average diameter of 62 nm. One attractive feature of this process is that 70 wt.% of the liquid precursor is converted into nanoscale powders. Another feature is that only a further 10 wt.% loss occurs during post thermal treatment to form the end-product.

scholarly journals Preparation and Characterization of Lead Oxide Nanoparticles by Laser Ablation as Antibacterial Agent

2017 ◽  
Vol 14 (4) ◽  
pp. 801-807
Author(s):  
Baghdad Science Journal
Keyword(s):  
Laser Ablation ◽  
Lead Oxide ◽  
Laser Energy ◽  
Laser Pulses ◽  
Diffusion Method ◽  
Lead Target ◽  
Oxide Nanoparticles ◽  
Gram Positive ◽  
Gram Negative ◽  
Gram Positive Bacteria

In this work, lead oxide nanoparticles were prepared by laser ablation of lead target immersed in deionized water by using pulsed Nd:YAG laser with laser energy 400 mJ/pulse and different laser pulses. The chemical bonding of lead oxide nps was investigated by Fourier Transform Infrared (FTIR); surface morphology and optical properties were investigated by Scanning Electron Microscope (SEM) and UV-Visible spectroscopy respectively, and the size effect of lead oxide nanoparticles was studied on its antibacterial action against two types of bacteria Gram-negitive (Escherichia coli) and Gram-positive (Staphylococcusaurus) by diffusion method. The antibacterial property results show that the antibacterial activity of the Lead oxide NPs was inversely proportional to the size of the nanoparticles in both Gram-negative and Gram-positive, and also it has been found that Gram-positive bacteria possess have greater sensitivity and less resistance to the lead oxide nanoparticles compared with Gram-negative bacteria.

scholarly journals PENYULUHAN DEMAM BERDARAH DENGUE (DBD) KEPADA PELAJAR-PELAJAR DI PERGURUAN KRISTEN METHODIST-2 RANTAUPRAPAT

2021 ◽  
Vol 2 (1) ◽  
pp. 33-41
Author(s):  
Saharnauli Janna Verawaty Simorangkir
Keyword(s):  
Dengue Virus ◽  
Dengue Fever ◽  
Mosquito Vectors ◽  
Public Concern ◽  
New Approach ◽  
Dengue Disease ◽  
Agents Of Change ◽  
Agent Of Change ◽  
Short Time ◽  
Activity Method

Abstrak Penyakit demam berdarah merupakan salah satu masalah kesehatan di Kota Medan yang cenderung menimbulkan kekhawatiran masyarakat karena perjalanan penyakitnya cepat dan dapat menyebabkan kematian dalam waktu yang singkat. Penyakit demam berdarah adalah penyakit yang disebabkan oleh virus dengue. Virus ini ditularkan melalui vector nyamuk. Pendekatan pemberantasan demam berdarah yang berwawasan kepedulian masyarakat merupakan salah satu alternatif pendekatan baru dalam rangka pengendalian penyebaran penyakit ini. Tujuan dari kegiatan ini adalah untuk memberikan penjelasan kepada pelajar-pelajar yang diharapkan dapat menjadi agent of change di lingkungannya dalam pemberantasan penyakit DBD ini. Metode kegiatan ini dilaksanakan dalam bentuk penyuluah, tanya jawab dan games. Kegiatan ini dinilai cukup berhasil. Indikator keberhasilannya adalah berdasarkan antusiasme peserta untuk bertanya dan feedback dari peserta yang menyatakan penyuluhan ini dinilai menarik dan bermanfaat. Kesimpulan dari kegiatan ini adalah melalui keilmuan yang dimiliki dapat digunakan untuk membantu memberikan pemahaman mengenai penyakit-penyakit kepada masyarakat, yang pada akhirnya dapat mendorong partisipasi masyarakat dalam pencegahan penularan dan pertambahan kasus-kasus penyakit tertentu di masyarakat Abstract Dengue fever is one of the health problems in Medan City which tends to cause public concern because the disease progresses quickly and can cause death in a short time. Dengue fever is a disease caused by the dengue virus. This virus is transmitted by mosquito vectors. The approach to eradicating dengue fever with a public concern is an alternative to a new approach to control the spread of this disease. The purpose of this activity is to provide explanations to students who are expected to become agents of change in their environment in eradicating this dengue disease. This activity method was carried out in the form of counseling, question and answer and games. This activity was considered quite successful. The success indicator was based on the enthusiasm of the participants to asked questions and feedback from the participants who stated that this counseling was considered interesting and useful. The conclusion of this activity was that through the knowledge that is owned it can be used to help provide an understanding of diseases to the community, which in turn can encourage community participation in preventing the transmission of certain diseases in the community.

“The Death of Liberal Internationalism?: Donald Trump, Walmart, and the Two Koreas”

2018 ◽  
Vol 25 (2) ◽  
pp. 169-197
Author(s):  
Mitchell B. Lerner
Keyword(s):  
United States ◽  
The United States ◽  
Business Practices ◽  
Short Term ◽  
New Approach ◽  
Liberal Internationalism ◽  
The People ◽  
Modern Business ◽  
Short Time

The election of Donald J. Trump unsettled many areas of U.S. foreign policy, but few more than the nation’s relationship with Korea. This article argues that the Trump administration’s vision for the world represents a stark break from the tradition of liberal internationalism and instead seeks to take the United States down a path that reflects the modern business practices of giant American corporations. A suitable label for this vision, as the following pages will show, is “Walmart unilateralism.” This framework abandons the traditional American policies of nation building and alliances based on shared ideological values. Instead, it embraces a more short-term approach rooted in financial bottom lines, flexible alliances and rivalries, and the ruthless exploitation of power hierarchies. This new approach, this article concludes, may dramatically transform the American relationship with Korea. Walmart unilateralism in Korea almost certainly will have some short-time positive ramifications for the United States, but its larger failure to consider the history and values of the people living on the Korean Peninsula may generate serious long-term problems for the future experience of the United States in the region.

Effect of Focusing Plane on Laser Blow-off Shock Waves from Confined Aluminum and Copper Foils

2021 ◽  
Author(s):  
Nagaraju Guthikonda ◽  
Sai Shiva S ◽  
E. Manikanta ◽  
Kameswari P S L D ◽  
V. R. Ikkurthi ◽  
...  
Keyword(s):  
Laser Energy ◽  
Plasma Temperature ◽  
Laser Pulses ◽  
Ambient Air ◽  
Rear Side ◽  
Hydrodynamic Simulations ◽  
Enhanced Absorption ◽  
532 Nm ◽  
Lower Plasma Density ◽  
Good Agreement

Abstract We present results on the dynamics of laser-induced blow-off shockwave generation from the rear side of 20 µm thick aluminum and copper foil confined with a glass (BK7) substrate. These foils are irradiated by 10 ns, 532 nm laser pulses of energy 25 – 200 mJ corresponding to the intensity range 0.2 – 10 GW/cm2. The plasma temperature at the glass-foil interface is observed to play an important role in the coupling of laser energy to the foil. From our experiments and 1D hydrodynamic simulations, we confirm that moving the glass-foil interface away from the focal plane led to (a) enhanced absorption of the laser beam by the foil resulting in ~ 30 % higher blow-off shock velocities (b) significant changes in the material ejection in terms of increased blow-off mass of the foil (c) lower plasma density and temperatures. The material ejection as well as blow-off shock velocity is higher for Al compared to Cu. The simulated shock evolution in ambient air shows a reasonably good agreement with the experimental results.

One-Step Fabrication and Functionalization of Nanostructured Silicon Surfaces for Advanced Sensing Applications

2020 ◽  
Vol 312 ◽  
pp. 154-159
Author(s):  
Alexander Yuryevich Mironenko ◽  
Mikhail Tutov ◽  
Alexander Konstantinovich Chepak ◽  
Eugeny Mitsai ◽  
Alexander A. Sergeev ◽  
...  
Keyword(s):  
Laser Processing ◽  
Laser Energy ◽  
High Spatial Frequency ◽  
Laser Pulses ◽  
Successful Implementation ◽  
Experimental Conditions ◽  
Sensing Applications ◽  
Direct Laser ◽  
Fs Laser ◽  
One Step

Direct laser processing of various materials with nano- and femtosecond (fs) laser pulses is known to be a facile and inexpensive technology for fabrication of various surface morphologies. Since ultrafast deposition of the laser energy to target material typically creates unique experimental conditions with extremely high pressure and temperature, we hypothesized that carrying out this process in anhydrous non-oxidizing environment containing functionalizing agent (fluorophore with vinyl functional group) will allow one-step fabrication and subsequent functionalization of the surface of high-n material. In this paper, we demonstrate successful implementation of this idea by fabricating high-spatial-frequency laser-induced periodic surface structures (LIPSS) via direct fs-pulse ablation of bulk crystalline Si wafer immersed in solution of N-vinylcarbazole in toluene. Laser processing with linearly polarized fs-laser pulses was found to produce LIPSS with a characteristic period around 100 nm functionalized with N-vinylcarbazole molecules via photo-activated hydrosililation reaction. The unique LIPSS with hierarchical roughness and remarkable light trapping performance functionalized with sensory fluorophore show high sensitivity due to implementation of surface enhanced fluorescence effect. By using N-vinylcarbazole as functionalizing agent we demonstrate one-step fabrication of high-performance sensor for detecting nitrobenzene in water with a detection limit of 40 nM.

scholarly journals Femtosecond Laser Fabrication of Engineered Functional Surfaces based on Biodegradable Polymer and Biopolymer/Ceramic Composite Thin Films

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 378 ◽  
Author(s):  
Albena Daskalova ◽  
Irina Bliznakova ◽  
Liliya Angelova ◽  
Anton Trifonov ◽  
Heidi Declercq ◽  
...  
Keyword(s):  
Thin Films ◽  
Surface Roughness ◽  
Femtosecond Laser ◽  
Surface Functionalization ◽  
Biodegradable Polymer ◽  
Photoelectron Spectroscopy ◽  
Laser Energy ◽  
Surface Characteristics ◽  
Laser Pulses ◽  
Xrd Analysis

Surface functionalization introduced by precisely-defined surface structures depended on the surface texture and quality. Laser treatment is an advanced, non-contact technique for improving the biomaterials surface characteristics. In this study, femtosecond laser modification was applied to fabricate diverse structures on biodegradable polymer thin films and their ceramic blends. The influences of key laser processing parameters like laser energy and a number of applied laser pulses (N) over laser-treated surfaces were investigated. The modification of surface roughness was determined by atomic force microscopy (AFM). The surface roughness (Rrms) increased from approximately 0.5 to nearly 3 µm. The roughness changed with increasing laser energy and a number of applied laser pulses (N). The induced morphologies with different laser parameters were compared via Scanning electron microscopy (SEM) and confocal microscopy analysis. The chemical composition of exposed surfaces was examined by FTIR, X-ray photoelectron spectroscopy (XPS), and XRD analysis. This work illustrates the capacity of the laser microstructuring method for surface functionalization with possible applications in improvement of cellular attachment and orientation. Cells exhibited an extended shape along laser-modified surface zones compared to non-structured areas and demonstrated parallel alignment to the created structures. We examined laser-material interaction, microstructural outgrowth, and surface-treatment effect. By comparing the experimental results, it can be summarized that considerable processing quality can be obtained with femtosecond laser structuring.

Sign in / Sign up

Export Citation Format

Share Document