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Densification Behavior of 316L Stainless Steel Parts Fabricated by Selective Laser Melting by Variation in Laser Energy Density

Densification Behavior of 316L Stainless Steel Parts Fabricated by Selective Laser Melting by Variation in Laser Energy Density

where P is the laser power (W), v is the scanning speed (mm/s), h is the hatch spacing (mm), and t is the layer thick- ness (mm). According to the eq. (1), the laser energy density E is simply controlled by the initial SLM process conditions of the laser powder, scanning speed, hatch spacing, and layer thickness. Thus, in this work, a parametric study was carried out to investigate the influence of the laser energy density on the densification and microstructural development of SS316L parts fabricated by the SLM process. The variation of the in- cident energy density was controlled by adjusting the laser scanning speed (v). The hardness and tensile properties of the fabricated samples were also evaluated, and consequently the suitable process window for SLM was properly determined. 2. Experimental Procedure
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Ultrafast Laser Energy Density and Retinal Absorption Cross Section Determination by Saturable Absorption Measurements

Ultrafast Laser Energy Density and Retinal Absorption Cross Section Determination by Saturable Absorption Measurements

ADS084BE in THF or the HKR1 rhodopsin in pH 7.4 HEPES/DDM buffer. The laser was operated in single- shot mode. It was fired every 10 seconds. Each energy transmission data point shown in Figures 5 and 6 was obtained as an average over about 30 laser shots. The retinal cofactor in HKR1 rhodopsin was brought and kept in the RetA isoform by continuous sample irradiation at 470 nm with an intensity of I exc = 1.5 mW cm −2 using a

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An Experimental Investigation on Effect of Volume Energy Density for Selective Laser Melted Inconel718

An Experimental Investigation on Effect of Volume Energy Density for Selective Laser Melted Inconel718

behavior of SLM processed Inconel718 is due to grain morphology and γ precipitation and grain orientation in relation to tensile axis [11]. Lower strength compared to conventionally processed part is due to micro cracks and porosity. Post process heat treatment is crucial for SLM processed part of Inconel718 to obtain improved mechanical properties [10]. Linear laser energy density also played a significant role in microstructure growth and development of surface texture of SLM processed part. Considerable abatement in cracking can be achieved with minor alterations to the composition of alloy constituents [39]. Interaction process between laser beam and base material determines the part geometry accuracy and properties of laser processed part [18]. Energy transfer to material from laser beam is essentially multifarious process affected by numerous factors like beam power density, wave length and pulse duration, irradiation time or scanning speed, absorptivity and thermo physical properties of powder. The microstructures and mechanical properties of SLM processed parts are restrained by complex physical and chemical changes within the molten pool and periodical energy transfer by laser. Laser energy input directly administers melting conditions of powder, flow of liquid metal which has significant impact on type and size of defect that affects quality and properties of built part. Linear energy density plays a vital role in microstructural evolution of SLM processed Inconel718 [7-8]. The molten metal flow and pool dimensions and solidification behavior is governed by volumetric energy density [27]. Grain morphology, orientation and precipitation of strengthening elements have remarkable impact on mechanical properties of SLM processed Inconel718 [19-20]. Higher scanning speed causes unstable melt flow and splashing of molten material and affects the surface roughness. Scanning speed has remarkable effect on relative density of SLM
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Laser modification of graphene oxide layers

Laser modification of graphene oxide layers

whereas the C-O peak that in GO commonly dominates is in the current sample reduced [17]. These indicate the significant degree of reduction of as-prepared GO foil that can be connected with warm drying during GO foil preparation. After laser irradiation there is evident slight increase of intensity of the C-C peak. This C-C mildly increase continues with the increasing laser energy density simultaneously with only C-O peak slight decrease. This phenomenon demonstrates the laconic reduction of the oxygen containing groups and creation of the carbon groups with increasing laser energy density, as has also been found using ATR-FTIR analysis. The RBS shows more pronounced deoxygenation compared to the XPS, but it should be emphasized that deconvolution of high resolution XPS C 1s peak provides information about oxygen bonded to carbon and that RBS detect oxygen in all chemical states in analysed matrix. It is therefore obvious that after laser irradiation mainly the groups obtaining the O-H bonds are removed as predicted by FTIR and can be concluded that the removal of the highly oxidized debris adsorbed on the surface of GO, so called cleaning, is more likely than GO reduction [21, 36].
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PC to PC Laser Communication

PC to PC Laser Communication

rectify the ripples. Since we can place the transmitter and receiver side at a distance we use two transformer and two power supply circuits. The MAX232 [1] IC is used to convert the logic from RS232 serial port [2] and transmit it over the PC. The Schmitt trigger is used to smoothen the wave pattern. The two PC’s can be installed with a software called Docklight which specializes in handling the RS232 serial port. The baud rate is set to 2400 for error free transmission and the setup of laser and photodiode always maintains line of sight.

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Nanosize Particles of ZrVFe Alloy by Pulsed Laser Ablation in Ethanol

Nanosize Particles of ZrVFe Alloy by Pulsed Laser Ablation in Ethanol

No specific change on the crystallographic structure is found on the powder X-ray diffraction of the raw target material and the prepared powder. Only the samples from the ablation in water have strong zirconium oxide and zirconium alloy peaks in the X-ray diffraction pattern. The water at the ablating site is presumed to oxidize the zirconium of the vaporizing target. As Kimura 11) and Yeh 12) reported for the coagulation of oxidized particles during laser irradiation of gold nano colloids and copper colloids, the dispersion of the nanoparticles in organic liquid was dramatically accelerated under the illumination of light. In the same way, the metallic vapor in water suffered an instantaneous high temperature and oxidized into the charged nano colloids. The stability of the particle is balanced between Van der Waals attraction and Coulomic repulsion. Enhancing Van der Waals attraction forces induced rapid coagulation of colloids. As a result, the oxidative condition of the liquid induces more charged particles and the particles are coagulated. This interpretation agrees with Fig. 2 that has shown the particles in water and hexane are seriously coagulated and are not able to maintain round shape particles.
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Laser Energy Scaling Law for the Yield of Neutrons Generated by Intense Femtosecond Laser-Cluster Interactions

Laser Energy Scaling Law for the Yield of Neutrons Generated by Intense Femtosecond Laser-Cluster Interactions

The generation of high-energy ions by interactions between intense femtosecond lasers and plasma can be realized via two mechanisms. One mechanism is based on acceleration in an electrostatic field induced by high- energy electrons driven by a ponderomotive force in over- dense plasmas in thin foils [7, 8], and the other involves Coulomb explosion in molecular gases, such as clusters or nano particles [6]. Here, we discuss the latter mech- anism. When a cluster is irradiated with an intense fem- tosecond laser pulse, the following two phenomena can be considered. One phenomenon concerns the heating of the cluster until it is transformed into spherical plasma and the subsequent expansion of the created plasma as a result of plasma pressure. The other phenomenon is that electrons are instantaneously expelled from the clus- ter, and the ion cluster thus explodes under the influence of repulsive Coulomb forces. Although it cannot be di- rectly observed, the type of phenomenon which occurs in the cluster can be determined from the energy distribu- tion of the ions emitted from the cluster. The respective ion energy distributions resulting from the two phenomena are rather different: ions emitted from expanding spher- ical plasma generally exhibit a broad Boltzmann energy distribution dN/dE∼exp(−E/k B T e ), while ions generated
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On the Internal Structure of a Black Hole Utilizing a 4 D Spatial Blackbody Radiation Model

On the Internal Structure of a Black Hole Utilizing a 4 D Spatial Blackbody Radiation Model

DOI: 10.4236/jhepgc.2019.53039 765 Journal of High Energy Physics, Gravitation and Cosmology somewhat familiar, and leads to acceptable results. We fixed the parameters by assuming that we have maximum radiative energy at the center, which allowed us to set, µ = 0 . We were also able to determine the shape parameter, σ , by using the temperature just inside the event horizon. This inner surface tempera- ture was calculated using a generalized version of the Stefan-Boltzmann law, de- rived in a previous paper, and which allows for radiative transfers between spac- es having different dimensions. In a very real sense, we can think of a black hole as an exotic type of capacitor, but one which stores energy in 4-D space, in a non-uniform way, and, in blackbody form. The distribution of radiative energy is not constant; rather it follows a pdf, which has to be specified and fulfill cer- tain conditions. We treat the black hole as a 4-D construct, for reasons given in a previous work. If our model is correct, the rip or tear in the space-time conti- nuum occurs not at the center of the black hole, but rather at its surface, because it is there that we are transitioning between 3-D and 4-D space. The event hori- zon is assumed infinitely thin.
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Escaping electrons from intense laser-solid interactions as a function of laser spot size

Escaping electrons from intense laser-solid interactions as a function of laser spot size

0.85mm thick iron filtering layers, they lose energy. Therefore, the deeper layers will only detect the higher energy electrons. The response function of each layer of image plate, as calculated by Rusby et al. [9], was calculated using the Monte Carlo code GEANT4; this is shown in Figure 1 c). The first layer of image plate will only detect electron energies greater than 3 MeV. The copper target was placed directly in the middle of the wraparound diagnostic so it provides angular information about the escaping electrons. It is biased vertically such that it only observes the lower half of the escaping electron beam. The specular reflectivity was also monitored using two 12-bit CCDs; one that observes the 1 µm laser reflection and the other the emitted 2 nd
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Comparison of refractive predictability and endothelial cell loss in femtosecond laser-assisted cataract surgery and conventional phaco surgery: prospective randomised trial with 6 months of follow-up

Comparison of refractive predictability and endothelial cell loss in femtosecond laser-assisted cataract surgery and conventional phaco surgery: prospective randomised trial with 6 months of follow-up

Limitations in our study is the lack of an objective or standardised subjective grading of the cataract grade preoperatively. This was not performed as cataract grading was not of primary concern instead we used energy consumption to evaluate ECL. We chose to use the patient as an intraindividual control and therefore randomised one eye leaving the other to get the opposite treatment than the randomised eye. It would have been possible to randomise all eyes instead of only one of the two eyes. We chose the former to reduce interindividual variation and because randomisation of all eyes would require inclusion of twice the number of eyes.
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Optimal laser marking of 2D data matrix codes on Cavendish bananas

Optimal laser marking of 2D data matrix codes on Cavendish bananas

cantly correlates with the contrast value, whereas no significant correlation is detected between the readability and the contrast value. Laser energy and marking time have positive correlations with read- ability of the code, while laser power gives no corre- lation. Accordingly, readability is more dependent on the laser energy and marking time than on the laser power. Marking at low laser energy for a short time tends to produce relatively low readability due to less contrast. However, applying low laser ener- gy for a longer time will produce better readability. This behaviour was similarly described by Sood et al. (2008), namely that higher exposure time at a low laser energy level (0.000752 W/dot) creates darker labels without significantly increasing peel disruption on tangerines. By contrast, using high energy may potentially damage outer cell layers of bananas and promote unsuccessful readability of the codes. Once the laser beam has irradiated on the outer cells, photons penetrate into the epider- mis layer and convert into thermal energy. Thus, the heat is distributed within the cells. According to Blanaru et al. (2003), the heat distribution is in- fluenced by thermal properties, conductivity, heat capacity, convective coefficients and emissivity of the plant material.
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3-Light Production - PPT slides

3-Light Production - PPT slides

- Military: Boeing airborne laser, tactical high energy laser. - Media technology: CD, DVD.[r]

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A Review Study on Amplification of X Ray Free Electron Laser Pulse in Plasma

A Review Study on Amplification of X Ray Free Electron Laser Pulse in Plasma

[23,24] results has shown the possibility and potential to focus and compress the intense laser pulses (optical and X-ray regime) through Backward Raman amplification (BRA) in plasmas. We report here the review study of these results and similar scalings for efficient BRA to compress and amplify the intense X-ray pulse. Before explaining the review work we outline first the BRA process in plasmas. BRA is based on the fact that a plasma can withstand very high energy densities due to its ionized nature. This has motivated research to realize a plasma amplifier to further boost the power of an ex- isting CPA system [25] or as an alternative technique that will replace CPA itself [26]. The idea of the Raman ef- fect in various media to amplify laser pulses extends back to work carried out 40 years ago when researchers used gases and liquids to amplify excimer laser pulses for the purpose of laser-based nuclear fusion [27]. The idea of using plasmas for this same purpose is however more recent. Proof-of-principle experiments demonstrating BRA in a plasma have been reported by several groups over the last 10 years. These studies have focused primarily on the amplification of ultrashort Ti:Sapphire laser pulses with the goal of creating ultrahigh peak intensities by significantly increasing the amount of energy contained in a single femtosecond-scale pulse.
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Influence of laser polarization on collective electron dynamics in ultraintense laser-foil interactions

Influence of laser polarization on collective electron dynamics in ultraintense laser-foil interactions

on the front and rear surfaces were included. Due to high computational requirements the mesh cell size was 20 nm. The target then was pre-expanded to a Gaussian profile (with 245 nm FWHM for the 10 nm case and 980 nm FWHM for the 40 nm case) in order to have a sufficient number of cells across it to avoid self-heating and other numerical artefacts. The peak electron density was reduced accordingly in both cases to keep the same areal density as a non-pre-expanded target. Pre-expansion of this order, prior to the peak of the laser interaction, is expected based on plasma expansion estimates for the measured laser contrast. The ion density was initialized to neutralize the electrons using appropriate proportions of Al 13+ , C 6+ and H + ions. The initial electron temperature, 100 keV, was selected to be low enough to avoid artificial thermal induced effects, but high enough to resolve the Debye length as closely as possible. Initially there were 22 simulation particles per cell per species (total of 3.11 × 10 9 simulation particles).
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The investigation of selective pre pattern free self assembled Ge nano dot formed by excimer laser annealing

The investigation of selective pre pattern free self assembled Ge nano dot formed by excimer laser annealing

Self-assembled Ge quantum dots and well arrangements have attracted a lot of attention due to their ability of being integrated into silicon-based optoelectronic and nano-electronic devices [1,2]. One of the motivations be- hind these efforts is to form devices and functions that take advantage of quantum confinement effects for elec- tronic and optical applications, such as light emitting diodes, tunneling diodes, detectors, etc. [3,4], where Ge quantum dots were formed by ultra-high vacuum chem- ical vapor deposition (UHV-CVD). Recently, the Ge dots multilayer solar cell made by molecular beam epitaxy was reported [5]. Another motivation is to find cost- effective methods for forming nanoscale devices without using expensive lithography techniques. Among the dif- ferent ways in producing quantum dots [6-8], excimer laser annealing (ELA) to induce self-assembled Ge islands is an innovative technique. ELA has been widely used in low temperature poly-Si thin film-transistor pro- cesses for flat panel display products [9]. One of the char- acteristics of laser annealing is a shallow absorption depth, which avoids heating of layers underneath, due to the high absorption coefficient of semiconductor material in the UV laser wavelength range [10]. An advantage of laser anneal- ing is the determination of dot localization on the surface.
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CLARA conceptual design report

CLARA conceptual design report

For example, in many schemes one or more magnetic chicanes are used, either to longitudi- nally shear the electron bunch or delay it with respect to the radiation. Often some wavelength- specific tolerances on the stability of these chicanes have been determined in the original papers (see for example [15]). Sometimes more specific issues have been raised which need further study, such as: the effect of R 51 leakage smearing the imparted modulation in EEHG; the degrading ef- fect of Coherent Synchrotron Radiation (CSR) emission in the chicanes; the washing out of FEL induced microbunching during beam transport; the discrepancy between the EEHG model, which assumes each harmonic has a δ -function linewidth, and reality where the harmonics all have a width which depends on laser pulse length, chirp, laser phase noise and electron beam shot noise. All of these effects will become relatively more significant for the finer beam manipulations and structures required at shorter wavelengths. Using CLARA we will be uniquely placed to actively study the impact of these effects by progressively changing the input parameters and carefully as- sessing the FEL performance. For example we can add errors to magnet angles, add jitter to mag- net power supplies, adjust the laser heater settings to control the beam microbunching, propagate bunched beams over variable distances before diagnosing the bunching degradation via Coherent Optical Transmission Radiation (COTR) screens, adjust the laser chirp and pulse duration, and so on. In this way we can obtain invaluable data which can be used to prioritise schemes for future implementation at X-ray wavelengths.
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Influence of different laser irradiation energy on ceramic bond strength

Influence of different laser irradiation energy on ceramic bond strength

Using an adhesive cementation strategy for treatments involving pure ceramics, generated the need of bond improvement between the resin cement and the ceramic substrate. In the last decade several studies have been conducted to bring solutions to this problem (Carvalho et al., 2011; Cavalcanti et al., 2009; Demir et al., 2012; Kirmali et al., 2014). Among the treatments evidenced are sandblasting with aluminum oxide particles (5.6), the silane drying with hot air (1.7) and the irradiation on surfaces with high power laser such as Er:YAG laser (erbium-doped: yttrium aluminum garnet) and Nd:YAG laser (neodymium-doped: yttrium aluminum garnet).Some studies have indicated that the use of Nd:YAG laser increase the roughness on the surface and bond strength improvement in adhesive resin bonding (Cavalcanti et al., 2009; Demir et al., 2012; Foxton et al., 2011; Guarda et al., 2013; Kirmali et al., 2014; Nagai, 2005).
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Cholesterol Interactions with Fatty Acids and DMPC Phospholipids of Liver Membranes

Cholesterol Interactions with Fatty Acids and DMPC Phospholipids of Liver Membranes

Cholesterol and fatty acids is important subject in liver to different model of regulation for realizing the evolution of vertebrates. The major solubility of cholesterol in bilayers of glycerol- phospholipids is between 65 and 50 mole%, relevant on the bilayer of lipid membrane but they cannot alone form multi layered structures. Livers from the transgenic rat showed increases in mRNAs encoding various enzymes of cholesterol synthesis, the LDL’s receptor and fatty acid synthesis. Based on our previous works we have modeled and simulated various molecules of that Cholesterol in binding to membrane. A number of computational chemistry studies carried out to understand of the cholesterol parallel to fatty acid synthesis (FAS) for preventing the fatty liver disease. In this work ELF, LOL, ECP, electrical properties such as electron densities, energy densities, and potential energy densities, eta index for some of the fatty acids have been calculated.
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Laser Produced Plasma X Ray Sources for Nanoscale Resolution Contact Microscopy: A Candidate in Cancerous Stem Cells Imaging

Laser Produced Plasma X Ray Sources for Nanoscale Resolution Contact Microscopy: A Candidate in Cancerous Stem Cells Imaging

DOI: 10.4236/ami.2017.74004 69 Advances in Molecular Imaging (0.6 J) and Nd:YAG (0.5 J) lasers has also been investigated since very long [11]. In this paper, results are reported using a Q-Switched neodymium glass laser of pulses in the nano scale range and powers up to 10 GW. One of the advantages of this technique is its spatial resolution at the nanometre scale with a soft X-ray microscope. Spatial resolution can be below 10 nm which will be of other inter- ests like for zone plate fabrication. This X-ray microscopy technique is therefore suitable for a wide range of studies; biological imaging in the water window [12]; studies of magnetic nanostructures with both elemental and spin-orbit sensitivi- ty [12]; studies that require viewing through thin windows, and three-dimensional imaging of cryogenically fixed biological cells [13].
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Echolocation signals of wild harbour porpoises, Phocoena
phocoena

Echolocation signals of wild harbour porpoises, Phocoena phocoena

The biosonar performance of a toothed whale under low noise and reverberation conditions is described by the transient form of the sonar equation (Eqn·1). The returning echo energy flux density is a function of the emitted source energy flux density and the target strength. As the target strength is dependent on the frequency content of the impinging signal (Urick, 1983), the energy flux density of the returning echo will depend on both the frequency and energy content of the emitted signal. Most toothed whales emit broadband clicks during echolocation. In theory, these animals could regulate their biosonar performance by changing both the frequency content and the intensity of the click independently. In practice, however, these parameters are closely interrelated so that high intensity clicks will also contain higher frequencies (Au, 1993). The harbour porpoise and the rest of the Phocoenidae family, plus dolphins of the genus Cephalorhynchus and the pygmy sperm whale of the genus Kogia, produce narrowband clicks of high frequency (Dubrovskij et al., 1971; Møhl and Andersen, 1973; Dawson and Thorpe, 1990; Au et al., 1999; Marten, 2000). The variation in the frequency content of harbour porpoise signals is small (Au et al., 1999) compared with odontocetes using broadband signals. Therefore, the only way in which the porpoise can affect the returning echo energy flux density is to alter the emitted source energy flux density, as seen by the sonar equation. An increased source energy flux density will lead to a higher received echo energy flux density, everything else being equal, and hence a better chance for the animal to detect and classify the target. However, there may be good reasons for odontocetes not to use the highest possible sound
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