Absorption Phenomena Research Articles

Activated Carbon Derived from Carbonization of Kevlar Waste Materials: A Novel Single Stage Method.

The augmented demands of textile materials over time have brought challenges in the disposal of substantial volumes of waste generated during the processing and end of life of such materials. Taking into consideration environmental safety due to discarding of textile waste, it becomes critical to recuperate useful products from such waste for economic reasons. The present work deals with the preparation of porous and electrically conductive activated carbon fabric by a novel single stage method of simultaneous carbonization and physical activation of Kevlar feedstock material procured from local industries, for effective electromagnetic (EM) shielding applications. The Kevlar fabric waste was directly carbonized under a layer of charcoal without any intermediate stabilization step at 800 °C, 1000 °C, and 1200 °C, with a heating rate of 300 °C/h and without any holding time. The physical and morphological properties of the activated carbon, influenced by carbonization process parameters, were characterized from EDX, X-ray diffraction, SEM analysis, and BET analysis. Furthermore, the electrical conductivity was analyzed. Finally, the potential application of the activated material for EM shielding effectiveness was analyzed at low (below 1.5 GHz) and high (2.45 GHz) frequencies. The phenomena of multiple internal reflections and absorption of electromagnetic radiations was found dominant in the case of activated carbon fabric produced at higher carbonization temperatures.

Bergenia ciliate-Mediated Mixed-Phase Synthesis and Characterization of Silver-Copper Oxide Nanocomposite for Environmental and Biological Applications.

Bergenia ciliate (B. ciliate) leaf extract was used as a reducing and stabilizing agent for the synthesis of silver-copper oxide nanocomposite (Ag-CuO NC). Scanning and transmission electron microscopies (SEM and TEM) were used to examine the structural morphology, and the average particle size was determined to be 47.65 nm. The phase confirmation and crystalline structure were examined through the X-ray diffraction (XRD) technique, where cubic and monoclinic geometries were assigned to Ag and CuO. The energy dispersive X-ray (EDX), Fourier transform infrared (FTIR) and ultra-violet and visible (UV-Visible) spectroscopies were operated to analyse the elemental composition, functional groups and light absorption phenomena of the Ag-CuO NC. Under the full light spectrum, the photodegradation of Rhodamine 6G was recorded, and 99.42 percent of the dye degraded in 80 min. The Agar well diffusion method was followed to perform antibacterial activity against selected pathogens, and the activity was found to increase with increasing concentration of Ag-CuO NC. The ABTS free radical scavenging activity suggests that the activity of Ag-CuO NC is higher than ascorbic acid.

Parameter inversion and microscopic damage research on discrete element model of cement-stabilized steel slag based on 3D scanning technology

The macro- and micro-physical properties of cement-stabilized steel slag (CSS) base materials in a highway project were studied. A discrete element model of CSS with a real steel slag shape was constructed using Particle Flow Code 3D and 3D scanning technology. The sensitivity between the macro- and micro-parameters of the sample was explored, and a nonlinear regression equation was established to analyze the relationship between these parameters. Uniaxial compression simulation tests were conducted on CSS with steel slag contents of 0%, 10%, 30%, and 50%. By combining contact calculation, crack location, energy tracking, acoustic emission (AE) monitoring, and other program systems, the macro- and micro-mechanical properties and micro-crack evolution law of the samples in the failure process were analyzed in terms of strength, energy, and fracture damage. The damage mechanism of CSS was also revealed. Results showed that with the increase in steel slag content, the elastic modulus and peak stress of the samples increased, the Poisson’s ratio decreased, and the post-peak stress curve steepened, indicating obvious brittle failure characteristics. With the increase in steel slag content, the crack initiation stress, thickness of the fracture surface, and number of internal micro-cracks in CSS increased exponentially. In the uniaxial compression test, AE intensity underwent five stages, in which the peak moment of AE intensity exhibited hysteresis compared with the moment of the peak stress. Absorption and release phenomena of strain energy were observed in the process of specimen failure. When the steel slag content increased, the total strain energy absorbed by the specimen increased. When the absorbed energy exceeded the bond strength, the bond ruptured with the release of energy. The main crack of the sample penetrated and stretched to the direction of strain energy release to form a macroscopic fracture surface.

Charge transfer transitions in glasses - Attempt of a systematic review

In glasses, even low levels of dopants or impurities can give rise to very intense and broad charge transfer transitions from ligands (e.g. oxygen or fluorine ions) to the metal ion (L→M), absorbing strongly in the short wavelength ultraviolet. In an attempt of a systematic review of charge transfer transitions, we compile data of various glass systems with high intrinsic transmission that allow the observation of charge transfer (CT) transitions involving cations of different electronic configurations. Various glasses of different composition were selected as matrices, including fluoroaluminate glasses with low P2O5 content (FP10 = 35AlF3–10MgF2–30CaF2–15SrF2–10Sr(PO3)2), phosphate [SrP = Sr(PO3)2, NSP = Na2O-40SrO-50P2O5], silicate (NS = 15Na2O–85SiO2, DS = 33Na2O–67SiO2), aluminosilicate (BCAS = 10BaO–10CaO–15Al2O3–65SiO2) and borosilicate (NBS1 = 16Na2O–10B2O3–74SiO2, NBS2 = 4Na2O–1Al2O3–21B2O3–74SiO2, Duran = 5Na2O/K2O–1Al2O3–12B2O3–82SiO2) compositions. All glasses were prepared from very high purity materials and doped with various metal ions. Charge transfer transitions of electrons to or from these cations induce absorption and photoluminescence phenomena in the ultraviolet and visible spectral region, which were recorded by optical spectroscopy.Charge transfer transitions were considered for empty valence orbitals, that is, for the high valent 3d, 4d and 5d ions, and for Zn2+, Ag+, Cu+ with full d10 orbitals. 3d, 4d and 5d ions with partially filled valence orbitals that could be stabilized in the named glasses are studied as well. Doping concentrations for these allowed transitions typically ranged from 5 to 5000 wt-ppm of metal ions, with some samples also displaying higher dopant levels.Inter valence charge transfer (IVCT) transitions directly from one metal ion to a neighboring metal ion (M→M) of the same element or metal to metal charge transfer (MM-CT) between ions of different elements can also induce strong visible absorption and deep coloring for which some examples will be discussed.

Acoustic graphene plasmon resonator based on gold nanowire arrays.

An acoustic graphene plasmon (AGP) resonator based on gold nanowire arrays structure is proposed in this paper. The resonator is designed by continuous graphene layer/gold nanowire arrays/optical resonant cavity. The infrared light excites the AGP in the graphene/gold arrays structure and propagates along the graphene surface. The coupling efficiency can be improved by the optical resonator cavity. The finite-difference time-domain method is used to simulate and optimize the property of the resonator. The results show that the resonator has a stronger optical limiting effect and higher coupling efficiency. The AGPs are a prospective platform that enhances light-matter interactions, reduces spread loss, and exhibits a double resonance absorption phenomenon in the studied mid-infrared wavelength range. The research results provide a basis for the design of optoelectronic devices and more.

A dense stereo matching method based on optimized direction-information images for the real underwater measurement environment

The refraction phenomenon of light at the interface of different media causes the epipolar to bend (the traditional camera model is invalid), and the stereo matching can’t be performed under the row matching. Therefore, we proposed a new model based on light field, in which an underwater image is expressed with the direction-information image and position image. The underwater stereo matching is conducted in the direction-information image instead of the original underwater image because the curve constraint of the correspondence becomes the row constraint in the direction-information image. In addition, the essence of stereo matching is similarity detection, but the phenomenon of absorption and scattering in water causes problems such as blurred outlines and loss of a large number of details in real underwater images, which will cause great interference in the similarity detection process. Therefore, we propose an image optimization method that fuses color correction and Dark channel Prior to improve the quality of the directional-information image. Finally, the underwater stereo matching process is divided into three steps. In order to verify the feasibility and effectiveness of the proposed method, we carry out more experiments. The experimental results show that our method and equipment can be used for underwater 3D measurement with high accuracy.

Phase transformation and enhanced blue photoluminescence of zirconium oxide poly-crystalline thin film induced by Ni ion beam irradiation

Swift heavy ions (SHI) irradiation of Nickel (Ni) beam with different ions fluence bring the modifications in the functional properties of radio frequency (RF) grown zirconium oxide (ZrO2) nanocrystalline thin films. X-ray diffraction analysis affirms the monoclinic to tetragonal phase transformation and diminishing of peak at higher fluence 1 × 1014 and 2 × 1014 ions/cm2 induced by electronic excitation caused by SHI. Zirconium oxide thin films exhibit the same thickness (195 nm) of virgin and irradiated samples and whereas the nanocrystalline thin films have the elemental composition in proper stoichiometry (1:2) as analyzed by rutherford backscattering spectroscopy (RBS). Photoluminescence measurements confirm the blue emission of virgin and irradiated sample recorded at excitation wavelength 270 to 310 nm. The intensity of obtained emission bands varies with fluence which is interpreted in terms of generation and annihilation of defect centers. The characteristic Ag and Bg Raman modes of monoclinic and tetragonal ZrO2 are obtained at different positions. Moreover, the nanocrystalline ZrO2 thin films exhibits the most prominent absorption phenomenon in the visible range and the irradiation cause significant decrease in band gap to 3.69 eV compare to the virgin ZrO2 sample (3.86 eV). XPS analysis indicates the shifting of the core levels Zr 3d and O 1s towards higher binding energy and spin—orbit splitting of different states. The findings in this research justify that the irradiated thin films can be a potential candidate for designing of new materials, intense radiation environments, nuclear reactors, nuclear waste systems, clean energy sources.

Convective Instability in Binary Nanofluids for Absorption Phenomenon with Cross Diffusions and Internal Heat Source

Convective Instability in Binary Nanofluids for Absorption Phenomenon with Cross Diffusions and Internal Heat Source

A Systematic Study of the Frequency Evolution Behavior of Pulsar Pulse Profiles

Abstract The frequency evolution behavior of radio pulse profiles is an important clue for the radiation mechanism of a pulsar. Combined with the latest results of the European Pulsar Network and the Australia Telescope National Facility data, we systematically study the evolution of W 50 (the full width of the pulse profile at 50% of the pulsar amplitude) for 74 pulsars with frequencies from tens to thousands of megahertz. We find that 71 pulsars show “absorption” features, which indicates that the absorption is an universal phenomenon in the pulsar population and independent of the type of pulsar profile. It is found that for most pulsars, the absorption features appear in the frequency range of 100–800 MHz, and the evolution trend of W 50 at frequencies less than ∼100 MHz and larger than ∼800 MHz can be described as a power-law function.We quantify the absorption intensity and analyze the correlation between the absorption intensity and the pulsar parameters (such as the spin period, magnetic field, and age of the pulsar). It is found that there is no direct correlation between them. Our results will provide good samples and clues for the study of the physical mechanism of the absorption phenomenon.

Revising Pharmacokinetics of Oral Drug Absorption: II Bioavailability-Bioequivalence Considerations.

To explore the application of the parameters of the physiologically based finite time pharmacokinetic(PBFTPK) models subdivided infirst-order(PBFTPK)1and zero-order (PBFTPK)0models to bioavailability and bioequivalence. To develop a methodology for the estimation of absolute bioavailability, F, from oral data exclusively. Simulated concentration time data were generated from the Bateman equation and compared with data generated from the (PBFTPK)1and (PBFTPK)0models. The blood concentration Cb(τ) at the end of the absorption processτ, was compared to Cmax; the utility of [Formula: see text]and [Formula: see text] in bioequivalence assessment was also explored. Equations for the calculation of F from oral data were derived forthe (PBFTPK)1and (PBFTPK)0models. An estimate for F was also derived from an areas proportionality using oral data exclusively. The simulated data of the (PBFTPK)0models exhibit rich dynamics encountered in complex drug absorption phenomena. Both (PBFTPK)1and (PBFTPK)0models result either in Cmax= Cb(τ) or Cmax> Cb(τ)for rapidly- and not rapidly-absorbed drugs, respectively; in the latter case, Cb(τ) andτ are meaningful parameters for drug's rate of exposure. For both (PBFTPK)1and (PBFTPK)0models,[Formula: see text]or portions of it cannot be used as early exposure rate indicators. [Formula: see text]is a useful parameter for the assessment of extent of absorption for very rapidly absorbed drugs. An estimate for F for theophylline formulations was found close to unity. The (PBFTPK)1and (PBFTPK)0models are more akin to in vivo conditions. Estimates for F can be derived from oral data exclusively.

Numerical Study of Heat Transfer Intensification in a Circular Tube Using a Thin, Radiation-Absorbing Insert. Part 1: Thermo-Hydraulic Characteristics

The presented paper, which is the first of two parts, shows the results of numerical investigations of a heat exchanger channel in the form of a cylindrical tube with a thin insert. The insert, placed concentrically in the pipe, uses the phenomenon of thermal radiation absorption to intensify the heat transfer between the pipe wall and the gas. Eight geometric configurations of the insert size were numerically investigated using CFD software, varying its diameter from 20% to 90% of the pipe diameter and obtaining the thermal-flow characteristics for each case. The tests were conducted for a range of numbers Re = 5000–100,000 and a constant temperature difference between the channel wall and the average gas temperature of ∆T = 100 °C. The results show that the highest increase in the Nu number was observed for the inserts with diameters of 0.3 and 0.4 of the channel diameter, while the highest flow resistance was noted for the inserts with diameters of 0.6–0.7 of the channel diameter. The f/fs(Re) and Nu/Nus(Re) ratios are shown on graphs indicating how much the flow resistance and heat transfer increased compared to the pipe without an insert. Two methods of calculating the Nu number are also presented and analysed. In the first one, the average fluid temperature of the entire pipe volume was used to calculate the Nu number, and in the second, only the average fluid temperature of the annular portion formed by the insert was used. The second one gives much larger Nu/Nus ratio values, reaching up to 8–9 for small Re numbers.

Numerical Study of Heat Transfer Intensification in a Circular Tube Using a Thin, Radiation-Absorbing Insert. Part 2: Thermal Performance

This article is the second part of the work under the same title, which is based on the results of the research presented in the previous article: “Numerical study of heat transfer intensification in a circular tube using a thin, radiation-absorbing insert. Part 1: Thermo-hydraulic characteristics”. Part 1 presents an analysis of pressure drops and heat transfer intensification in a round tube with an insert, using the phenomenon of radiation absorption. In this paper, an analysis of the tested insert’s thermal performance (PEC) is presented, taking into account the criterion of equal pumping power. The tests were carried out for the range of Re = 5000–100,000 numbers, for various insert diameters (from 20% to 90% of the pipe diameter) and a constant temperature difference between the wall and the gas ∆T = 100 °C. The highest Nu numbers were observed for inserts with dimensionless diameters of 0.3 and 0.4, while the highest flow resistance was observed for inserts with diameters of 0.6 and 0.7 of the channel diameter. The thermal efficiency was calculated in two ways, as was the associated Nu number. These results significantly differed from each other: the maximum PEC values for method (I) reached 2, and for method (II) to 8. The common feature for both calculation methods was the fact that the maximum values of the Nu number and the thermal efficiency were observed for small Re numbers; however, as the Re number increases, PEC and Nu number decrease strongly.

Presence, flow, and narrative absorption: an interdisciplinary theoretical exploration with a new spatiotemporal integrated model based on predictive processing.

Presence, flow, narrative absorption, immersion, transportation, and similar subjective phenomena are studied in many different disciplines, mostly in relation to mediated experiences (books, film, VR, games). Moreover, since real, virtual, or fictional agents are often involved, concepts like identification and state empathy are often linked to engaging media use. Based on a scoping review that identified similarities in the wording of various questionnaire items conceived to measure different phenomena, we categorize items into the most relevant psychological aspects and use this categorization to propose an interdisciplinary systematization. Then, based on a framework of embodied predictive processing, we present a new cognitive model of presence-related phenomena for mediated and non-mediated experiences, integrating spatial and temporal aspects and also considering the role of fiction and media design. Key processes described within the model are: selective attention, enactment of intentions, and interoception. We claim that presence is the state of perceived successful agency of an embodied mind able to correctly enact its predictions. The difference between real-life and simulated experiences ("book problem," "paradox of fiction") lays in the different precision weighting of exteroceptive and interoceptive signals.

Coherent perfect absorption of quantum light

Coherent perfect absorption (CPA) was introduced as a classical optics phenomenon of a standing-wave absorption by a subwavelength film. In this paper, we develop a theory of CPA of quantized standing waves taking account of a subwavelength thickness of the absorber. This approach allows us to merge all known quantum effects of CPA under a single theory and introduce other regimes of CPA including CPA of NOON states with arbitrary number of entangled photons, orthogonally squeezed vacuum states, continuous variable entangled states, and Schr\"odinger cat states. Detailed analysis of the quantum regime of CPA sheds light on fundamental aspects of quantum light dissipation and its practical implementation in quantum optics and quantum information.

Dislocation imaging through mapping based on the combination of an electron energy-loss spectroscope with a scanning transmission electron microscope

ABSTRACT This study analysed the electronic structures of dislocations in 9Cr steel using a spherical aberration-corrected scanning transmission electron microscope equipped with a monochromated electron energy-loss spectroscope. This is the first study to report that dislocations broaden a zero-loss peak (ZLP) and also induce an absorption phenomenon at approximately 0.5 eV in the ZLP tail, which are interpreted to be related to phonon scatterings by dislocations and interference effect of multiple beams, respectively. This work also experimentally demonstrates that the use of a spectrum-imaging method allows imaging of dislocations through ZLP broadening. The approach proposed herein is a promising technique for detecting dislocations in high Cr steel.

Influences of CO2 laser modification on the surface morphology and optical absorption of graphene thin films

Abnormal optical absorption phenomena were observed in as-modified few-layer graphene thin films by 10.6-μm CO2 laser under ambient conditions. Saturable absorption (SA) responses were measured using z-scan technology. The graphene samples showed SA before laser modification, whereas they exhibited reverse SA behavior after laser modification due to the effects of thinning and damage to samples. The shift of 2D peak and appearance of D peak from Raman scattering spectra further confirm the effects of laser irradiation on graphene.

Passive absorber design for mechanical vibrations with base excitation

The dynamic coupling of mechanical vibratory systems results in the oscillatory interaction between the bodies of the system as a whole, for a certain selection of some parameters the phenomenon of vibration absorption occurs, in this phenomenon the main system transfers its mechanical energy to the absorber, resulting in a minimum amplitude of movement of the primary system and the absorber develops a certain amplitude. In this work it is proposed to design a vibration absorber for a primary system that in turn is affected by the motion in the base, which produces vibrations, the motion in the base includes elastic and viscous actions. It has been possible to determine a set of parameters that allow the absorption of vibrations, likewise, the parameters determined not only allow the absorption, but also establish a transfer of the effect of the damping present in the base to the absorber.

Heat absorption due to falling film with imposed uniform mass fraction at the wall

The combined heat and mass transfer problem in the presence of constant mass fraction at the wall occurring in the process of laminar falling film absorption is undertaken in the present work. The energy and absorbate equations are analytically treated by means of integral transforms due to the versatile analytical solving Laplace method and exact series solutions are obtained for temperature and mass fraction fields under the assumptions of both the insulated (adiabatic) and isothermal wall boundary conditions. The effects of constant wall mass fraction versus the impermeable mass flux are then investigated across the film while the absorption evolves in the streamwise direction. Flow length dependent and independent solutions are eventually presented and discussed. The results clearly indicate that the final output through the film absorption process whether accounting for the adiabatic or isothermal wall boundary conditions can be controlled by the imposition of an adequate uniform mass fraction at the wall, which may have significant implications in the design of new generation absorbent tubes or similar apparatuses in medical applications. Supplying a uniform mass fraction at the wall considerably alters the physical absorption phenomenon. Impermeable wall condition is found to be equivalent to diminishing mass fraction at the wall and initial mass fraction at the wall resulted in enhanced cooling when the Stefan number goes to zero. Enhanced absorbed mass flux at the interface and heat transfer at the wall takes place by the prescription of constant mass fraction at the wall.

Global Analysis of a Spatiotemporal Cellular Model for the Transmission of Hepatitis C Virus With Hattaf-Yousfi Functional Response

This paper carries out a mathematical analysis of the global dynamics of a partial differential equation viral infection cellular model. We study the dynamics of a hepatitis C virus (HCV) model, under therapy, that considers both absorption phenomenon and diffusion of virions, infected and uninfected hepatocytes in the liver. Firstly, we prove the boundedness of the potential solutions, global existence, uniqueness, and positivity of the obtained initial value and boundary problem solution. Then, the dynamical behaviour of the model is entirely determined by a threshold parameter called the basic reproduction number denoted R0. We show that the uninfected spatially homogeneous equilibrium of the model is globally asymptotically stable if R0≤1 by using the direct Lyapunov method. The latter means that the HCV infection is cleared, and the disease dies out. Also, the global asymptotical properties stability of the infected spatially homogeneous equilibrium of the model are studied via a skilful construction of a suitable Lyapunov functional. It means that the HCV infection persists in the host, and the infection becomes chronic. Finally, numerical simulations are performed to support the obtained theoretical results.

Perfect Absorption of a Focused Light Beam by a Single Nanoparticle

AbstractAbsorption of electromagnetic energy by a dissipative material is one of the most fundamental electromagnetic processes that underlies a plethora of applied problems, including sensing, radar detection, wireless power transfer, and photovoltaics. Common wisdom is that a finite dissipative object illuminated by a plane wave removes only a finite amount of the wave's energy flux, which is determined by the object's absorption cross‐section. Thus, it is of fundamental interest to see if any far‐field waveform can be perfectly absorbed by a finite object. Here, it is theoretically demonstrated that a precisely tailored light beam containing only far‐field components can be perfectly absorbed by a finite scatterer on a substrate. The self‐consistent scattering problem in the dipole approximation is analytically solved and finds a closed‐form expression for the spatial spectrum of the incident field and the required complex polarizability of the particle. All analytical predictions are confirmed with full‐wave simulations. The results introduce a qualitatively novel class of perfect absorption phenomena in electromagnetics and other wave processes.