Air Medium Research Articles

PD01-03 CHANGES IN STONE CORE TEMPERATURE: FRAGMENTATION VS. DUSTING

You have accessJournal of UrologyCME1 Apr 2023PD01-03 CHANGES IN STONE CORE TEMPERATURE: FRAGMENTATION VS. DUSTING Ron Marom, John Robinson, Adam J. Matzger, Adam Maxwell, Khurshid R. Ghani, Timothy L. Hall, and William W. Roberts Ron MaromRon Marom More articles by this author , John RobinsonJohn Robinson More articles by this author , Adam J. MatzgerAdam J. Matzger More articles by this author , Adam MaxwellAdam Maxwell More articles by this author , Khurshid R. GhaniKhurshid R. Ghani More articles by this author , Timothy L. HallTimothy L. Hall More articles by this author , and William W. RobertsWilliam W. Roberts More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003218.03AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Tailoring and optimizing laser settings to achieve desired ablation effects (dusting vs. fragmenting) is challenging, in part due to an incomplete understanding of the mechanism of laser stone ablation. Recently, the dominance of photothermal over photoacoustic effects has been challenged. Quantification of the photothermal effect by measuring the temperature of the stone with absorption of laser energy could help us better understand the contribution of this mechanism of stone ablation. The objective of this study was to measure stone temperature during laser lithotripsy. METHODS: A cylindrical BegoStone model with a diameter of 8 mm and a height of 10 mm was molded with a thermocouple along its long axis with the tip at its center. A laser fiber was set perpendicular to the long axis and in contact with the stone surface. While the laser was activated for 30 seconds in an air medium, the fiber was moved by a 3D stepper scanning the surface of the stone. Two 10-Watt laser settings were used – 0.2 J × 50 Hz (Dusting) and 1 J × 10 Hz (Fragmentation) for 5 cycles with 30 seconds in between. Additionally, the power outputs of these settings were measured and compared using a power meter. RESULTS: The stone core temperature increased after each cycle of laser activation and did not return to baseline between cycles (Figure 1). Stone temperature of up to 120°C was observed. The 1 J × 10 Hz setting produced greater temperatures, 30°C greater than produced by 0.2 J × 50 Hz after the 5th laser cycle (Figure 2). This significant difference between same power settings can only be partially explained by the inconsistent energy output of the Ho:YAG laser, with up to 15% energy deviation as measured by a power meter. CONCLUSIONS: We have developed a tool to investigate temperature elevation in a stone model and shown that laser lithotripsy can substantially elevate stone temperature. Furthermore, the higher temperature found with higher pulse energy deserves additional exploration as temperature may play a role in determining whether dusting or fragmentation dominates stone comminution. Source of Funding: None © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e63 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Ron Marom More articles by this author John Robinson More articles by this author Adam J. Matzger More articles by this author Adam Maxwell More articles by this author Khurshid R. Ghani More articles by this author Timothy L. Hall More articles by this author William W. Roberts More articles by this author Expand All Advertisement PDF downloadLoading ...

The response of a steel-ceramic composite structure to dynamic loading: comparison between air and water explosions

In this paper, by utilizing LS-DYNA hydrocode, the simulation of the explosion phenomenon was performed by the Load Blast Enhance method and the Arbitrary Lagrangian-Eulerian technique for air and water environment, respectively. The composite armor consists of three layers of alumina ceramic, hot rolled armor steel, and polymethyl methacrylate polymer as the face, back, and target layers, respectively. The deformation and effective stress of the target layer for two kinds of the test were compared. Utilizing the response surface methodology and analysis of variance, it was revealed that the ceramic layer thickness has the most influence on the displacement of the target layer in both environments. Moreover, by defining the destruction ratio, it was specified that in the underwater explosion, this ratio is much higher versus air blasting due to the incompressibility and higher density of the water vs. the air. Since, more incredible energy will be transmitted to the structure in the water explosion, accordingly, more severe deformation occurs within the water-submerged structure versus the air medium.

Long-Range EM Communication Underwater With Ultracompact ELF Magneto-Mechanical Antenna

In this article, a long-range underwater electromagnetic (EM) communication system is proposed based on an ultracompact extremely low-frequency (ELF) magnetomechanical transmission antenna (UEMTA). The transmitter mainly includes a waveform generator, a variable frequency drive (VFD), and a three-phase induction motor. The receiver consists of a 200-turn coil and signal analyzer. Based on the equivalent model of a rotating magnetic dipole, the principles of the EM transmission underwater and across the interface of water and air are analyzed. ELF wave propagating underwater in the adjacent area was stronger and decays slowly, which was certificated by the experiment and simulation. Thus, the long-range transmission underwater in the ELF band with digital coding modulation based on the UEMTA is realized, and the longest distance can reach 210 m underwater in the experiment. The transmission of ELF wave across water–air medium based on the system is also tested by the experiment too. The long-range transmission of digital coding modulation across the water–air interface is realized with the longest distance of about 210 m. The ELF transmission technology based on the UEMTA can greatly promote flexible long-distance underwater transmission, the development of satellite-to-submarine communication, and ocean exploration.

Single-Step Synthesis of Graphitic Carbon Nitride Nanomaterials by Directly Calcining the Mixture of Urea and Thiourea: Application for Rhodamine B (RhB) Dye Degradation

Recently, polymeric graphitic carbon nitride (g-C3N4) has been explored as a potential catalytic material for the removal of organic pollutants in wastewater. In this work, graphitic carbon nitride (g-C3N4) photocatalysts were synthesized using mixtures of low-cost, environment-friendly urea and thiourea as precursors by varying calcination temperatures ranging from 500 to 650 °C for 3 h in an air medium. Different analytical methods were used to characterize prepared g-C3N4 samples. The effects of different calcination temperatures on the structural, morphological, optical, and physiochemical properties of g-C3N4 photocatalysts were investigated. The results showed that rhodamine B (RhB) dye removal efficiency of g-C3N4 prepared at a calcination temperature of 600 °C exhibited 94.83% within 180 min visible LED light irradiation. Photocatalytic activity of g-C3N4 was enhanced by calcination at higher temperatures, possibly by increasing crystallinity that ameliorated the separation of photoinduced charge carriers. Thus, controlling the type of precursors and calcination temperatures has a great impact on the photocatalytic performance of g-C3N4 towards the photodegradation of RhB dye. This investigation provides useful information about the synthesis of novel polymeric g-C3N4 photocatalysts using a mixture of two different environmentally benign precursors at high calcination temperatures for the photodegradation of organic pollutants.

Effects of Heat Treatment on Color, Dimensional Stability, Hygroscopicity and Chemical Structure of Afrormosia and Newtonia Wood: A Comparative Study of Air and Palm Oil Medium.

In recent years, China is increasingly dependent on imported wood. Afrormosia and Newtonia are some of the imported species with good utilization potential. However, both of them also have problems with poor dimensional stability. In order to make better use of these two types of wood, the influence of heat treatment under air and palm oil conditions on the color, dimensional stability, and hygroscopicity of Afrormosia and Newtonia was investigated. The Afrormosia and Newtonia wood samples were heated in air or palm oil medium for two hours at 160 °C, 180 °C and 200 °C, respectively. Then, the color, weight changes, swelling, moisture absorption and chemical structure were evaluated for each case. As results, the heat treatments with air or palm oil increased the dark color of Newtonia and Afrormosia wood and this increase was proportional to the treatment temperature. The tangential and radial swelling coefficient for air heat treatment of Afrormosia wood at 200 °C were, respectively, reduced by 24.59% and 19.58%, while this reduction for Newtonia was 21.32% and 14.80%. The heat treatment in palm oil further improved the stability and hygroscopicity of the wood, showing that the Afrormosia samples treated by palm oil at 200 °C underwent a decrease of its tangential and radial swelling coefficient, respectively, by 49.34% and 45.88%, whereas the tangential and radial swelling coefficient of Newtonia treated under the same conditions were reduced by 42.85% and 33.63%, respectively. The heat treatments of Afrormosia and Newtonia samples under air at 200 °C diminished the water absorption by 21.67% and 22.12%. The water absorption of Afrormosia and Newtonia heat-treated under palm oil at 200 °C was reduced, respectively, by 39.40% and 37.49%. Moreover, the FTIR analysis showed the decrease of hydroxyl groups in proportion to the wood treatment temperature.

Estimation of effective thermal conductivity and heat transfer coefficient of lithium orthosilicate pebble bed in carbon dioxide–air medium

ABSTRACT Lithium orthosilicate has the highest absorption capacity among other materials used to capture carbon dioxide (CO2) at a higher temperature. To design a CO2 adsorption system consisting of lithium orthosilicate pebble bed, effective thermal conductivity and heat transfer coefficient data are necessary, and till date, these are not reported in the literature. In the present study, experiments were conducted to estimate the effective thermal conductivity and heat transfer coefficient of lithium orthosilicate pebble bed in CO2–air medium. Effects of CO2 concentration in air, bed temperature, and gas flowrate on the hydrodynamic as well as heat transfer properties of the pebble bed of lithium orthosilicate pebbles were also studied. The effective thermal conductivity and heat transfer coefficients were found in the range of 0.2–0.75 Wm−1K−1 and 14–63 Wm−2K−1, respectively.

Experimental study of different innovative measurement methodologies applied to a canned pulsed eddy current testing probe suitable for dilation measurement of test specimens

A compact pulsed eddy current testing probe is being developed for the online dilation measurement of test specimens, examined in the high-temperature environment of material testing reactors. The probe has to be canned with metallic clad to protect it from the corrosive sodium-potassium coolant medium present in the material testing reactor. Electromagnetic modelling of the probe was carried out to compute the distribution of time-dependent eddy current density in the vicinity of the probe. It is understood that the slope of the pulsed eddy current signals in the specific time zone where the lift-off point of intersection occurs show a good correlation to the distance between the face of the probe and the test specimen. This paper discusses the experimental study of employing different measurement methodologies at room temperature with the canned pulsed eddy current probe to evaluate its feasibility for dilation measurement. It is observed that a phenomenon of a divergence of signals, akin to the lift-off point of intersection, occurs just after the transient part of the pulsed eddy current signals. Slope analysis of these diverging pulsed eddy current signals was carried out for characterisation of the probe in the air medium as well as the metallic medium present in the gap between the probe face and the test specimen.

Internet of things based automated monitoring for indoor aeroponic system

On the ever-rising urgency of global food security, efforts are required to develop a robust farming technique. This includes the capability of farming in non-agricultural land or indoor spaces. Farming in the air medium, i.e., aeroponic, has persistently stepped in as a viable solution. Aeroponic farming allows efficient water usage while preventing soil related diseases and pests. With the assistance of light emitting diodes (LEDs) and precise electronic monitoring and control, aeroponic may become the suitable farming technique of the future. This work presents an aeroponic system capable of automated monitoring and control of farming parameters. The system achieved both robustness in indoor farming and remote access by employing LED as an artificial lighting system and the internet-of-things (IoT) connectivity, respectively. The test result demonstrated that the system successfully maintained the root chamber temperature below 30 °C with a typical average temperature of 28.8 °C. The system managed a humidity level which prevented plants from drying out. It was also evident that the LED assistance significantly improved the growth quality of <em>Ipomea reptans</em>. The system, data, and analysis presented in this work is expected to facilitate further development of a robust food production system in overcoming the global food crisis.

Mathematical Model of the Ignition of a Gel Fuel Particle in a High-Temperature Air Medium

Mathematical Model of the Ignition of a Gel Fuel Particle in a High-Temperature Air Medium

Hydrogen generation from gasification of woody biomass upon acid mine drainage sludge as a novel catalyst under an air medium

In this study, the feasibility of employing acid mine drainage sludge (AMDS), mainly consisting of iron oxide (Fe2O3), as a novel catalyst for the air gasification of woody sawdust to produce H2-rich gas was evaluated for the first time. The effects of temperature, equivalence ratio (ER), and contact mode of the feedstock and catalyst on gas yield and H2 selectivity were investigated. Using the AMDS catalyst, a comparably higher gas yield (56.79 wt%) and higher content of H2 (18.31 vol%) and CO2 (36.45 vol%) were obtained compared to those obtained in the non-catalytic case owing to stimulated water–gas shift and steam–methane reforming reactions caused by the redox cycle of Fe2O3 within the gasification process. Gas yield and H2 concentration were enhanced by increasing the temperature from 750 to 850 ℃ (up to 65.11 wt% and 21.73 vol%, respectively) due to promoted endothermic reactions. Although increasing the ER from 0.1 to 0.3 dramatically increased the gas yield, it was not conducive to the promotion of H2 production, primarily because of the stimulated hydrogen oxidation reaction. The ex situ contact mode, where feedstock and catalyst were placed in the reactor and catalyst bed, respectively, resulted in a higher gas yield and H2 selectivity compared to those achieved by the in situ case, in which a mixture of feedstock and catalysts was located in the same reactor. Overall, the gasification of woody sawdust over an AMDS catalyst in an air medium has the potential to mitigate the challenges of AMDS treatment along with the production of valuable H2-rich gas.

Моделирование динамики электризованного потока частиц при ветровом выносе средствами OpenFoam

We study the generation of dust aerosol in the wind-driven cascading motion of charged particles over an irregular surface. The particles move under the influence of air flow over two elements of ripple type on an aeolian surface. Behind the obstacles the flow of saltation particles becomes non-uniform, the character of motion is noted by quasi-periodicity. The problem of including electrostatic effects into the hydrodynamic model, in which the mutual influence of particles and air medium is taken into account, was solved. A parametric model is proposed, which allows taking into account the chargeability of dust particles and the underlying surface in modeling wind transport. Computational experiments are carried out using the open source OpenFOAM package, the Eulerian-Lagrangian turbulent k-ω-model. Accordingly, the dynamics of charged particles is considered taking into account the electrification of the surface itself. From the results of computational experiments for different density characteristics of particles charged homonymously with the surface, the influence of the electric field on the frequency of change of the number of particles in the flow, on the scattering of values of velocities and the height of particle hops, as well as on the weakening of the effect of particles on the medium behind obstacles is estimated. When the influence of electrostatic effects is taken into account, an increase in the disturbing effect of particles flying after obstacles on the air medium is revealed (the distance from the obstacle increases, more local areas of disturbance appear). A decrease in the dispersion value is noted for the velocities of hopping particles. The height of particle jumps increases, which is confirmed by known experiments. The lower value of characteristic frequencies of change in the number of particles in the flow decreases. The non-uniformity of the particle flow determines changes in the intensity of dust aerosol generation.

Investigation of the adsorption behavior of the anti-cancer drug hydroxyurea on the graphene, BN, AlN, and GaN nanosheets and their doped structures via DFT and COSMO calculations.

To reduce the direct side effects of chemotherapy, researchers are trying to establish a new approach of a drug-delivery system using nanomaterials. In this study, we investigated graphene and its derivative nanomaterials for their favorable adsorption behavior with the anti-cancer drug hydroxyurea (HU) using DFT calculations. Initially, different pristine and doped graphene and its derivatives were taken into consideration as HU drug carriers. Among them, AlN, GaN, GaN-doped AlN, and AlN-doped GaN nanosheets exhibited favorable adsorption behavior with HU. The HU adsorbed on these four nanosheets with adsorption energies of -0.92, -0.75, -0.83, and -0.69 eV, transferring 0.16, 0.032, 0.108, and 0.230 e charges to the nanosheets, respectively, in air medium. In water solvent media, these four nanosheets interacted with HU by -0.56, -0.45, -0.58, and -0.56 eV by accepting a significant amount of charge of about 0.125, 0.128, 0.192, and 0.126 e from HU. The dipole moment and COSMO analysis also indicated that these nanosheets, except for GaN-doped AlN, show high asymmetricity and solubility in water solvent media due to the increased values of the dipole moment by two or three times after the adsorption of the HU drug. Quantum molecular descriptors also suggest that the sensitivity and reactivity of the nanosheets are enhanced during the interaction with HU. Therefore, these nanosheets can be used as anti-cancer drug carriers.

Beamwidth Enhancement of Microstrip Antennas Using Capacitive Via-Fence Loading

In this paper, a general approach to enhance the beamwidth of microstrip antennas is proposed for wide beam coverage in both E- and H-planes. A microstrip antenna loaded with two arrays of capacitive via fences is propounded and systematically studied. By introducing the vertical currents brought by the capacitive metalized vias, the half-power beamwidth (HPBW) is effectively broadened compared with the regular microstrip antennas. In addition, by utilizing the air medium with low loss, the microstrip antenna can be supported by the two arrays of via fences, maintaining a high radiation efficiency. To validate the proposed design, a prototype is fabricated and tested. The measurement results agree well with the simulated ones, with enhanced HPBWs of 100° and 90° in E- and H-planes, respectively. Compared with the existing 2.4-GHz antennas, the propounded antenna is with the advantages of wide beamwidth and high radiation efficiency, exhibiting the potential applications for space-limited mobile devices with wide coverage requirement.

ВКЛАД ТЕРМОЭМИССИИ НА КОНЦЕНТРАЦИЮ ЗАРЯДОВ В ЛАЗЕРНОМ ПУЧКЕ, РАСПРОСТРАНЯЮЩЕМСЯ ЧЕРЕЗ АЭРОЗОЛЬ

Physical processes occurring in aerodisperse media with solid particles during thermal emission of electrons from the particle surface and primary optical breakdown are considered. The possibility of weak ionization of the air medium at a distance of several centimeters from the breakdown center is shown, due to the ionization of NO molecules and the course of a number of thermochemical reactions suitable for use in a long laser spark.

Получение высокодисперсного порошка оксида цинка путем сжигания смеси нитрата цинка с глицином и его применение для фотокаталитического разложения фенола

The paper presents the results of a detailed study of the process and products of combustion during self-propagating high-temperature synthesis (SHS) of ZnO zinc oxide powder from mixtures of such common reagents as oxidizer zinc nitrate and reducing agent (fuel) glycine, as well as the application of synthesized highly dispersed submicron and nanosized ZnO powder for the phenol photocatalytic decomposition under the action of ultraviolet irradiation. An aqueous solution of a mixture of reagents (the SHS-S process or Solution Combustion Synthesis – SCS) and the gel from a mixture of initial dry reagents formed when they were moistened due to hygroscopicity (the SHS-G process or Gel Combustion Synthesis – GCS) were combusted. The authors studied the phase and chemical compositions, the structure of the combustion product, and the effect of calcination in an oxidizing air medium and grinding in drum ball and planetary-centrifugal mills, as well as in mortar, on them and their photocatalythic activity. The study showed that calcination considerably increases the photocatalytic activity of combustion products due to a significant decrease in carbon impurity in the unburned fuel remains, and grinding in mills reduces the photocatalytic activity due to iron contamination and coarsening of ZnO particle agglomerates. The difference between the photocatalytic activity of the SHS-G and SHS-S products in the phenol decomposition is evident only at the initial stage of ultraviolet irradiation, after which this difference disappears. The authors discuss the direction of further research to increase significantly the photocatalytic activity of zinc oxide synthesized during combustion to use it effectively for the phenol decomposition under the action of visible light.

Thermal behavior of diesel, honge oil methyl ester and ITS B-20 blend in atmospheric air and oxygen

ABSTRACT Thermal behavior of honge oil methyl ester (HOME) and its B-20 blend (20% HOME and 80% diesel) is examined by performing calorimetric experiments at 10°C/min heating rate in atmospheric air and oxygen medium. Thermogravitometry (TG) curves indicate two phases of decomposition for diesel and three phases for biofuel. Combustion reaction favors in oxidative atmosphere causing reduction in fuel preparation stage and increase in premixed burning phase reducing peak temperature of combustion and increasing enthalpy with high heat release rate. B-20 blend performance is similar to diesel with combustion index and intensity of combustion and is thermally stable with high offset temperature confirming more combustion duration. Blend of diesel lowers activation energy in initial stage of combustion process, whereas reverse trend is observed in final stage. Ignition index (Di) in air for diesel, HOME, and its B-20 blend is reduced by 70.11%, 34.92% and 42.80% respectively. Burnout index (Db) in air for diesel and B-20 blend reduced by 72% and 61% respectively whereas it increased by 28.5% for HOME. Combustion index (S) is more in air for HOME and its blend. Improved intensity of combustion is observed for diesel and B-20 blend in oxygen whereas reverse trend is observed for HOME.

Methodical approaches to scale-up measurement of glyphosate concentration using HPLC-FLD

Introduction. Traditionally, the hygienic assessment of working conditions when using glyphosate preparations, an extremely popular herbicide in the world, is based on the use of thin layer chromatography. In this paper, alternative approaches are considered. On the basis of experimental data, the conditions for the analysis of glyphosate content in air by high performance liquid chromatography were optimized. Material and methods. All work with glyphosate solutions was carried out in polypropylene vessels. Sampling from the air medium was carried out on a medium filtration filter (“blue ribbon”). Subsequent extraction was carried out with water. The measurements were performed by high performance liquid chromatography with a fluorimetric detector at an excitation wavelength of 270 nm and an emission wavelength of 313 nm. To transfer glyphosate to a molecule with fluorimetric properties after derivatization of glyphosate in an alkaline medium using 9-fluorenylmethyl chloroformate by heating and washing off the excess of the reagent with toluene. A C18 reverse phase column was used; ammonium acetate with the addition of acetic acid and acetonitrile were used as eluents. Results. Approbation of the developed technique was carried out on real samples taken during ground treatment of fallow fields and lands of industrial territories with glyphosate preparations. The detected levels of glyphosate did not exceed the lower limit of quantitative determination: 0.5 mg/m3 in the air of the working area and 0.025 mg/m3 in the atmospheric air (with maximum allowable concentrations of 1.0 and 0.1 mg/m3, respectively). Limitations. The study considers a limited number of chromatographic columns. The study is performed on 25 model samples of the air of the working area and atmospheric air. Conclusion. Based on the results of the work performed, methodological instructions “Measurement of glyphosate concentrations in the air by high-performance liquid chromatography” were formed and sent for metrological certification in the approved manner.

Development of Sound Experimentation Tool using Android-Based Sound Analysis Oscilloscope Software

Experimental activities are part of physics learning process with the aim of gaining knowledge and having good understanding of physics concepts. Sound and organ pipes are the main subjects discussed in physics and engineering lessons. These materials contain facts accompanied by actualization in everyday life in social life. However, the fact in high school (SMA) physics learning is that experimental activities in supporting students’ learning and understanding have not been widely carried out. This is due to the lack of practical support tools. The purposes of this research are to design a sound experimentation tool design of an open and closed organ pipes and to determine the value of the speed of sound which propagates through air medium using a data acquisition technique assisted by sound analysis oscilloscope software. This type of research is a Research and Development research with five stages referring to the ADDIE model. The first stage was analysis, that was done by conducting a study of the problems of physics learning at senior high school level, especially in sound chapter. The second stage was design, namely designing experimentation tools. The third stage was development, that was done by providing materials that were used in the experiment. The fourth stage was implementation, that was testing the tool which had been made combined with sound analysis oscilloscope software, and the fifth was conducting an evaluation and feasibility test based on the validity of the experimental data. The data analysis technique used average and linear regression by utilizing the results of data from frequency analysis using sound analysis oscilloscope software. The results showed that the experimentation tool in this study was able to be used as learning media for the sound and open and closed organ pipes materials. The experimental results obtained that the speed of the sound waves propagation in air for an open organ pipe was v = 332.19 m/s with an accuracy rate of 97.70%. While the value of the speed of the sound waves in air for a closed organ pipe was v = 334.69 m/s with an accuracy rate of 98.44%.

Absorption characteristics of a typical photonic crystal unidirectional absorber under graphene modulation

Unidirectional absorbers have potential applications in infrared detection, energy conversion, and solar energy harvesting. In this work, the absorption properties of a typical photonic crystal (PC) unidirectional absorber in the visible- and near-infrared modulated by graphene are systematically investigated. This is achieved by placing a typical non-periodic PC in an air medium. When the electromagnetic wave is incident vertically, double peak absorption is formed at wavelengths of 560 nm as well as 755 nm. The achieved non-reciprocal absorption is attributed by the surface plasmon resonance between the semiconductor and metal defect layers. In this work, the effect of period numbers is discussed to improve absorption performance. Meanwhile, the role of the metal defect layer is explored by the variation of the electric field inside the device. And the unidirectional absorption performance was verified. In addition, the absorption characteristics of the two types of semi-conductor material devices are analyzed. Compared to existing unidirectional devices, this structure has the advantages of small size, high efficiency, wide bandwidth, and easy optoelectronic integration. This structure, based on its own absorption and emission characteristics, can facilitate the development of LIDAR stealth devices, and thus, the advancement of infrared radar steganography.

Laser Welding of Ti6Al4V Titanium Alloy in Air and a Water Medium.

Ti6Al4V titanium alloys are widely used in a variety of scientific and industrial fields. Laser beam welding is one of the most effective techniques for the joining of titanium plates. The main objective of this study was to investigate the influence of the most important laser parameters on welding performance of titanium alloy in two different physical environments such as air and water (i.e., serum) media. Specifically, the laser beam welding of 2 mm thick Ti6Al4V samples was applied using an Nd:YAG laser in open-air welding using argon as a shielding gas, and in wet welding using a serum environment. The deepest penetration was achieved at -3 mm focal position with 11 J of laser energy in both investigated media (i.e., air and serum). The maximum hardness (1130 HV) was achieved for the focal position of -4 mm in serum medium while it was 795 HV for a focal position of -5 mm in air medium. The minimum (1200 μm and 800 μm) and maximum (1960 μm and 1900 μm) weld widths were observed for air and serum medium, respectively. After the welding process, martensite, massif martensite, and transformed martensite were observed in the microstructure of Ti6Al4V. To the best of our knowledge, the underwater wet welding of titanium alloy was carried out and reported for the first time in this study.