Journal articles on the topic 'Absorbed power density (APD)'
To see the other types of publications on this topic, follow the link: Absorbed power density (APD).
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Absorbed power density (APD).'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Mutombo, Ntumba Marc-Alain, and Bubele Papy Numbi. "Absorbed power density approach for optimal design of heaving point absorber wave energy converter: A case study of Durban sea characteristics." Journal of Energy in Southern Africa 33, no. 1 (March 17, 2022): 52–67. http://dx.doi.org/10.17159/2413-3051/2022/v33i1a10381.
Abstract:
This work proposes an approach for the optimal sizing of a cylindrical heaving wave energy converter (WEC). The approach is based on maximising the absorbed power density (APD) of the buoy, with the diameter being the decision variable. Furthermore, two types of buoy shapes were compared to get the best option. The two buoy shapes are the cone cylinder buoy (CCB) and the hemisphere cylinder buoy (HCB). The aim was therefore to determine the best shape and as well as the optimal size of the cylindrical point absorber. To validate the approach, the simulation was performed under Durban (South Africa) sea characteristics of 3.6 m wave significant height and 8.5 s peak period, using the openWEC simulator. The buoy diameter range considered was from 0.5 m to 10 m for both shapes. Simulation results revealed that a diameter of 1 m was the optimal solution for both buoy shapes. Furthermore, the APD method revealed that the HCB was more efficient than the CCB. The power density of the HCB was 1070 W/m2, which was almost double the power density of the CCB, while the two shapes present almost the same absorbed power.
2
Liang, Zhiyue, Haoyu Zhang, Zixiang Li, Dong Du, and Li Wang. "In situ monitoring of beam current in electron beam directed energy deposition based on adsorbed electrons." Journal of Physics: Conference Series 2369, no. 1 (November 1, 2022): 012086. http://dx.doi.org/10.1088/1742-6596/2369/1/012086.
Abstract:
Electron beam directed energy deposition (EB-DED) is a promising and efficient additive manufacturing technology, but the vacuum environment challenges the in situ parameters monitoring. In this paper, an in situ beam current monitoring method is developed based on the absorbed electrons. A series of experiments show that there is a linear relationship between the absorbed electron current and the impinging beam current. However, this relationship only holds when the beam power density is relatively low. When the power density is high, the absorbed electron current will be lower than the theoretical value determined by the linear relationship. This is mainly due to the massive generation and ionization of metal vapor. The critical power density depends on the melting point of the material. Nonetheless, the deviation of the absorbed electron current at high power density can roughly determine the relative position between the focal spot and the workpiece surface. In addition, the slope of the linear relationship is material-dependent, so this method can also distinguish different materials.
3
Lee, S. "Density ratios in compressions driven by radiation pressure." Laser and Particle Beams 6, no. 3 (August 1988): 597–606. http://dx.doi.org/10.1017/s026303460000553x.
Abstract:
It has been recently suggested (Hora & Miley 1984) that in the cannonball scheme of laser compression the pellet may be considered to be compressed by the ‘brute force’ of the radiation pressure. For such a radiation-driven compression, this paper applies an energy balance method to give an equation fixing the radius compression ratio κ which is a key parameter for such intense compressions. A shock model is used to yield specific results. For a square-pulse driving power compressing a spherical pellet with a specific heat ratio of 5/3, a density compression ratio Γ of 27 is computed. Double (stepped) pulsing with linearly rising power enhances Γ to 1750. The value of Γ is not dependent on the absolute magnitude of the piston power, as long as this is large enough. Further enhancement of compression by multiple (stepped) pulsing becomes obvious. The enhanced compression increases the energy gain factor G for a 100 μm DT pellet driven by radiation power of 1016 W from 6 for a square pulse power with 0·5 MJ absorbed energy to 90 for a double (stepped) linearly rising pulse with absorbed energy of 0·4 MJ assuming perfect coupling efficiency.
4
Vashchuk, E. S., E. A. Budovskikh, L. P. Bashchenko, V. E. Gromov, and K. V. Aksenova. "Structural Phase States and Surface Properties of Steel 45 after Electroexplosive Borocoppering and Electron-Beam Treatment." Izvestiya of Altai State University, no. 4(120) (September 10, 2021): 17–23. http://dx.doi.org/10.14258/izvasu(2021)4-02.
Abstract:
The paper concerns improving the microhardness and wear resistance of steel 45 by the combined treatment of electroexplosive borocoppering with the subsequent electron-beam treatment. It is found that surface roughness at the area of the electroexplosive treatment increases along with the absorbed power density and the mass of boron powder. The electron-beam treatment leads to a decrease of roughness and appearance of craters instead of radial melt flow traces. The depth structure of the electroexplosive alloying area with a thickness of 25 µm includes a coating layer, near-surface, intermediate, and boundary layers. The surface microhardness and the depth of the hardening zone after the electroexlosive alloying increase along with the absorbed power density and boron concentration and reach the values of 1400 HV The electron-beam treatment causes merging of the coating and the surface layers and increases the hardening zone depth up to 80 µm. A cellular or dendritic crystallization structure is formed near the surface, and a grain structure is formed in the depth. The inhomogeneous distribution of alloying elements over the volume of the alloying area and its adjustment during the electron-beam treatment are established. The inter-dendritic distances and grain diameters increase as the absorbed power density becomes higher with the increase of the electron-beam treatment exposure time. Also, the size of martensite needles increases in the depth. The combined treatment produces the sub microcrystalline strengthening phases-borides FeB, Fe2B, FeB2, carboboride Fe23 (C, B)6 , and carbide B4C. The microhardness level is reduced to 800 HV, and the wear resistance increases up to five times when compared to the wear resistance of the base.
5
Poljak, Dragan, Anna Šušnjara, and Lucija Kraljević. "Assessment of absorbed power density in multilayer planar model of human tissue." Radiation Protection Dosimetry 199, no. 8-9 (May 24, 2023): 798–805. http://dx.doi.org/10.1093/rpd/ncad082.
Abstract:
Abstract The paper deals with the determination of the absorbed power density (Sab) in a planar multilayer model of a tissue exposed to the radiation of a dipole antenna, based on the analytical/numerical approach. A derivation of Sab from the differential form of Poynting theorem is presented. The two-layer and three-layer tissue models are used. Illustrative analytical/numerical results for electric and magnetic fields and Sab induced at the tissue surface for various antenna lengths, operating frequencies and antenna-interface distances are presented in the paper. Exposure scenarios of interest pertain to frequencies above 6GHz pertaining to 5G mobile systems.
6
Arreola-Ramos, Carlos E., Omar Álvarez-Brito, Juan Daniel Macías, Aldo Javier Guadarrama-Mendoza, Manuel A. Ramírez-Cabrera, Armando Rojas-Morin, Patricio J. Valadés-Pelayo, Heidi Isabel Villafán-Vidales, and Camilo A. Arancibia-Bulnes. "Experimental Evaluation and Modeling of Air Heating in a Ceramic Foam Volumetric Absorber by Effective Parameters." Energies 14, no. 9 (April 27, 2021): 2506. http://dx.doi.org/10.3390/en14092506.
Abstract:
Reticulate porous ceramic reactors use foam-type absorbers in their operation which must fulfill two essential functions: favoring the volumetric effect and increasing the mass and heat transfer by acting as a support for the reactive materials. Heating these absorbers with highly inhomogeneous concentrate irradiation induces high thermal gradients that affect their thermal performance. Owing to the critical function of these component in the reactor, it is necessary to define a selection criterion for the foam-type absorbers. In this work, we performed an experimental and numerical thermal analysis of three partially stabilized zirconia (PSZ) foam-type absorbers with pore density of 10, 20, and 30 PPI (pores per inch) used as a volumetric absorber. A numerical model and an analytical approximation were developed to reproduce experimental results, and calculate the thermal conductivity, as well as volumetric heat transfer coefficient. The results show that an increase in pore density leads to an increase in the temperature difference between the irradiated face and the rear face of the absorber, this occurs because when pore density increases the concentrated energy no longer penetrates in the deepest space of the absorber and energy is absorbed in areas close to the surface; therefore, temperature gradients are created within the porous medium. The opposite effect occurs when the airflow rate increases; the temperature gradient between the irradiated face and the rear face is reduced. This behavior is more noticeable at low pore densities, but at high pore densities, the effect is less relevant because the internal structure of porous absorbers with high pore density is more complex, which offers obstructions or physical barriers to airflow and thermal barriers to heat transfer. When the steady state is reached, the temperature difference between the two faces of the absorber remains constant if the concentrate irradiation changes slightly, even changing the airflow rate. The results obtained in this work allow us to establish a selection criterion for porous absorbers that operate within solar reactors; this criterion is based on knowledge of the physical properties of the porous absorber, the environment, the working conditions, and the results expected.
7
Kim, J. D., Jin Seok Oh, Myung Hyun Lee, and Y. S. Kim. "Spectroscopic Analysis of Plasma Induced in Laser Welding of Aluminum Alloys." Materials Science Forum 449-452 (March 2004): 429–32. http://dx.doi.org/10.4028/www.scientific.net/msf.449-452.429.
Abstract:
This paper describes the features and characteristics of plasma induced in the pulsed YAG laser welding of Al-Mg alloys in air and argon atmospheres. In the air environment, the identified spectra are atomic lines of Al, Mg, Cr, Mn, Fe and Zn, and singly ionized Mg line, as well as strong molecular spectrum of AlO, MgO and AlH. It has been confirmed that the resonant lines of Al and Mg were strongly self-absorbed. These facts have shown that the laser-induced plasma is relatively a low temperature and high density metallic vapor. The intensities of molecular spectra of AlO and MgO are different each other depending on the power density of laser beam. Under the low power density irradiation condition, the MgO band spectrum is predominant in intensity, while the AlO spectrum became much stronger with the increase in high power density. This was attributed by the great difference in boiling point and vaporization energy of Al and Mg. In argon atmosphere the band spectra of MgO and AlO completely vanished, but AlH molecular spectra is detected clearly. The hydrogen source is presumably the hydrogen solved in the base metal, absorbed water on the surface oxide layer, or H2 and H2O in the shielding gas.
8
Mitev, Ivan, and Simeon Tsenkulovski. "LOCAL PROCESSING OF NON-METAL MATERIALS WITH CONCENTRATED ENERGY FLOW." ENVIRONMENT. TECHNOLOGIES. RESOURCES. Proceedings of the International Scientific and Practical Conference 3 (June 13, 2023): 183–86. http://dx.doi.org/10.17770/etr2023vol3.7275.
Abstract:
In the present study, the peculiarities of local heat treatment with a concentrated light energy flow of non-metallic materials are traced. Mathematical dependences are presented for determining the surface density of the absorbed power - W(r), the thermal power - Po, and other characteristics in case of local thermal impact on the surface of non-metallic materials with a concentrated light energy flow.
9
Li, Jiang-Jiang, Yan-Bin Xi, Na Gao, Zhi-Qiang Wang, Qian Wang, and Yue Liu. "Effect of electron density gradient on power absorption during gigahertz electromagnetic wave propagating in cold plasma." Physics of Plasmas 29, no. 3 (March 2022): 033301. http://dx.doi.org/10.1063/5.0080079.
Abstract:
Considering the effect of electron density gradient, an analytical, parameter adjustable density distribution function is presented, and a multislab plasma model is used to investigate power absorption of gigahertz electromagnetic waves between 0.20 and 30 GHz in a partially ionized cold plasma layer. The effects of plasma parameters on the absorbed power during electromagnetic wave propagation are investigated and compared with corresponding uniform cases. An optimized asymmetric electron density gradient profile is designed by calculating the corresponding absorption spectrum with selected parameters to enhance the absorption rate near original peak frequencies. The possibility of theoretically designing electron density gradient profiles is important to understand how to enhance the plasma cloaking in some specific electromagnetic wave frequency bands.
10
Song, Jaeman, Minwoo Choi, Zhimin Yang, Jungchul Lee, and Bong Jae Lee. "A multi-junction-based near-field solar thermophotovoltaic system with a graphite intermediate structure." Applied Physics Letters 121, no. 16 (October 17, 2022): 163503. http://dx.doi.org/10.1063/5.0115007.
Abstract:
A solar thermophotovoltaic (STPV) system can transform incident concentrated solar energy into electrical energy with an efficiency that could be higher than the Shockley–Queisser limit. Near-field thermophotovoltaic (NF-TPV) devices can generate larger electrical power output than traditional far-field TPV devices with the aid of photon tunneling. Moreover, multi-junction PV cells can boost the performance of TPV devices by effectively distributing the absorbed photon energy inside the PV cell. In this work, we design a multi-junction-based near-field STPV system with a practical and high-temperature stable graphite intermediate structure. To optimize the system configuration, we employ a genetic algorithm and a surrogate model based on an artificial neural network, which enables us to suggest a better design approach for the multi-junction-based NF-STPV system between the power output density and power conversion efficiency maximization scenarios. When the concentration factor of the incident solar energy is 5000 and the absorber-to-emitter area ratio is 3, we can achieve a system efficiency of 23%. By introducing a material whose emissivity is as high as a blackbody on the solar absorber, the system efficiency can be further enhanced up to 35%.
11
Sedláček, Z., and B. Roberts. "Resonance absorption of energy by a cold inhomogeneous plasma." Journal of Plasma Physics 41, no. 1 (February 1989): 97–105. http://dx.doi.org/10.1017/s0022377800013696.
Abstract:
The active and reactive power resonantly absorbed by a linear passive system is calculated in terms of its continuum eigenfunctions and the spatial–temporal spectral density of the external force. An application to the resonance absorption of electromagnetic radiation by a cold inhomogeneous plasma is given.
12
Pavlovic, Z., Ivica Manic, and Snezana Golubovic. "Effects of γ-irradiation on electrical characteristics of power vdmos transistors." Facta universitatis - series: Physics, Chemistry and Technology 2, no. 4 (2002): 223–33. http://dx.doi.org/10.2298/fupct0204223p.
Abstract:
In this paper we present the results of both experimental investigation and analytical modelling of ?-irradiation effects on basic electrical characteristics of power VDMOS transistors. First, an analytical model that yields the drain current and transconductance dependencies on gate oxide charge density is developed. The experimental data are utilized to establish an analytical relation between the absorbed dose of ?-irradiation and corresponding effective density of gate oxide charges, as well as to extract the values of model parameters. Drain current and transconductance of VDMOS devices are then modelled as the functions of irradiation dose. Finally, the results of modelling are compared with experimental data.
13
Lei, Fan, Yan Xue, and Donglin Liu. "Simulation of millimeter-sized microwave plasma discharge generator under various conditions." AIP Advances 12, no. 8 (August 1, 2022): 085015. http://dx.doi.org/10.1063/5.0105035.
Abstract:
A microwave plasma generator (MPG) of a sub-millimeter scale might be suitable for biomedical applications. However, there are still many unknowns regarding the MPG discharge behavior at this scale and specific conditions. A two-dimensional MPG model at the millimeter scale and its simulation and relative calculation in the COMSOL Multiphysics software are presented. A MPG filled with argon and helium is simulated, respectively. The frequency of a microwave source of about 5 GHz is considered. The number density and temperature of electrons as well as chemical composition are obtained at different power and pressure conditions. The electron density peaks slightly downstream of the crossing point, and the electron density is slightly asymmetrically in the y-plane due to the fact that the electromagnetic waves are absorbed asymmetrically. The electron temperature is relatively low everywhere, in part, due to the high operating pressure. The electron temperature peaks directly underneath the wave guide where the wave is absorbed. The electron density increases with the increase in the internal pressure and the input power of the MPG, the electron temperature decreases with the increase in the internal pressure of the MPG, but the electron temperature cannot be affected by the input power change of MPG. The amount of excited Ar+ and Ars (metastable atom) increases with the increase in the input power and pressure of MPG, but the amount of excited Ar almost remained unchanged. In addition, the amount of excited He almost remained unchanged, while the amount of excited He+, Hes (metastable atom), and He2+ increased with the increase in the input power and pressure of MPG. The simulation results of this model are thus informative for understanding the physical characteristics of millimeter-sized MPG, and it will provide a solid basis for the future development of such hardware in small plasma capsules for cancer therapy.
14
Wang, Zhao Xi, Hui Ji Shi, Guo Dong Zhang, Bao Ping Qu, Jian Lu, and Xian Bo Zhao. "Investigation of the Hydrogen Embrittlement on the 65Mn Steel from the Nuclear Power Plant with Small Punch Method." Advanced Materials Research 118-120 (June 2010): 206–10. http://dx.doi.org/10.4028/www.scientific.net/amr.118-120.206.
Abstract:
Damage of metals due to the influence of hydrogen is quite frequent and leads to dangerous failures. The characteristics of the hydrogen embrittlemnt of the 65Mn steel were evaluated with small punch test. With the increment of the amount of the hydrogen absorbed into the alloy at room temperature, the strength and the toughness of the material reduce. From the small punch experimental results, it is found the total impact energy, the fracture strain and the fracture stress decrease with the increment of the cathodic hydrogen charging time. The fracture surfaces change from the typical ductile fracture with big voids to the typical intergranular brittle fracture mode after hydrogen absorbed in the specimens with higher charging current density.
15
Зуев, С. Ю., А. Я. Лопатин, В. И. Лучин, Н. Н. Салащенко, Д. А. Татарский, Н. Н. Цыбин, and Н. И. Чхало. "Сравнительное исследование термостойкости пелликлов на основе бериллия." Журнал технической физики 92, no. 1 (2022): 92. http://dx.doi.org/10.21883/jtf.2022.01.51857.197-21.
Abstract:
We demonstrate the possibility of manufacturing Be-based ultrathin films with high transmission at wavelengths of 11.4 and 13.5 nm. For free-standing films of Be and Be-based multilayer structures (Si/Be, ZrSi2/Be, Be/BexNy, Zr/Be, Ru/Be, Mo/Be), we determine the thresholds of the absorbed power at which over a short period (tens of minutes) of vacuum annealing, initially sagging free-standing films became visibly stretched over the hole. Of the film structures tested here, the Be/BexNy structure (with beryllium nitride interlayers) showed the highest threshold for the absorbed power (1 W/cm2). However, due to the low strength of this structure, ZrSi2/Be, Mo/Be, and Be films seem to be more promising for the manufacture of a full-size pellicle. Long-term vacuum annealing of Mo/Be and Be ultrathin films showed that they could withstand 24 hours of vacuum heating at an absorbed power density of 0.2 W/cm2 (film temperature ~250°C) without noticeable changes in EUV transmission or sagging of films. With comparable transmission (~83% at 13.5 nm and ~88% at 11.4 nm), a multilayer Mo/Be structure with a thickness of 30 nm appears to be preferable, as it shows less brittleness than a monolayer Be film with a thickness of 50 nm.
16
Martín Ortega, Álvaro, Ana Lacoste, Stéphane Béchu, Alexandre Bès, and Nader Sadeghi. "Characterization of X-ray gas attenuator plasmas by optical emission and tunable laser absorption spectroscopies." Journal of Synchrotron Radiation 24, no. 6 (October 6, 2017): 1195–208. http://dx.doi.org/10.1107/s1600577517012000.
Abstract:
X-ray gas attenuators are used in high-energy synchrotron beamlines as high-pass filters to reduce the incident power on downstream optical elements. The absorption of the X-ray beam ionizes and heats up the gas, creating plasma around the beam path and hence temperature and density gradients between the center and the walls of the attenuator vessel. The objective of this work is to demonstrate experimentally the generation of plasma by the X-ray beam and to investigate its spatial distribution by measuring some of its parameters, simultaneously with the X-ray power absorption. The gases used in this study were argon and krypton between 13 and 530 mbar. The distribution of the 2pexcited states of both gases was measured using optical emission spectroscopy, and the density of argon metastable atoms in the 1s5state was deduced using tunable laser absorption spectroscopy. The amount of power absorbed was measured using calorimetry and X-ray transmission. The results showed a plasma confined around the X-ray beam path, its size determined mainly by the spatial dimensions of the X-ray beam and not by the absorbed power or the gas pressure. In addition, the X-ray absorption showed a hot central region at a temperature varying between 400 and 1100 K, depending on the incident beam power and on the gas used. The results show that the plasma generated by the X-ray beam plays an essential role in the X-ray absorption. Therefore, plasma processes must be taken into account in the design and modeling of gas attenuators.
17
Ma, Yongqian, Bo Tang, Xiaolan Liu, Ru Shao, and Huangang Zhu. "Study on fractal and energy dissipation characteristics of rock impact fragmentation in Junggar basin." Journal of Physics: Conference Series 2683, no. 1 (January 1, 2024): 012015. http://dx.doi.org/10.1088/1742-6596/2683/1/012015.
Abstract:
Abstract In order to study the rock energy absorption and crushing fractal characteristics under impact load, the dynamic impact tests of rock in J1b formation in Junggar Basin were carried out by split Hopkinson bar. The strain rate effect on the crushing energy consumption and failure mode were analyzed. Combined with fractal dimension calculation and energy density analysis, the energy density and fractal characteristics of rocks during the impact process are studied. The results showed that the strain rate and energy density of the specimens are in line with the power relationship, the energy density increases with the strain rate, and the fractal dimension increases significantly with the increase of the strain rate, the energy density and fractal dimension of the specimen under dynamic load conform to a power relationship. The more energy absorbed by the rock, the more obvious the fractal characteristics are. The energy density combined with the fractal dimension calculation of rock fragmentation can quantitatively study the energy absorption law of rock per unit time.
18
Ziane, Massinissa, Ronan Sauleau, and Maxim Zhadobov. "Antenna/Body Coupling in the Near-Field at 60 GHz: Impact on the Absorbed Power Density." Applied Sciences 10, no. 21 (October 22, 2020): 7392. http://dx.doi.org/10.3390/app10217392.
Abstract:
Wireless devices, such as smartphones, tablets, and laptops, are intended to be used in the vicinity of the human body. When an antenna is placed close to a lossy medium, near-field interactions may modify the electromagnetic field distribution. Here, we analyze analytically and numerically the impact of antenna/human body interactions on the transmitted power density (TPD) at 60 GHz using a skin-equivalent model. To this end, several scenarios of increasing complexity are considered: plane-wave illumination, equivalent source, and patch antenna arrays. Our results demonstrate that, for all considered scenarios, the presence of the body in the vicinity of a source results in an increase in the average TPD. The local TPD enhancement due to the body presence close to a patch antenna array reaches 95.5% for an adult (dry skin). The variations are higher for wet skin (up to 98.25%) and for children (up to 103.3%). Both absolute value and spatial distribution of TPD are altered by the antenna/body coupling. These results suggest that the exact distribution of TPD cannot be retrieved from measurements of the incident power density in free-space in absence of the body. Therefore, for accurate measurements of the absorbed and epithelial power density (metrics used as the main dosimetric quantities at frequencies > 6 GHz), it is important to perform measurements under conditions where the wireless device under test is perturbed in the same way as by the presence of the human body in realistic use case scenarios.
19
Ali, M. B., Kamarul Ariffin Zakaria, Shahrum Abdullah, and M. R. Alkhari. "Correlation of Impact Energy from Instrumented Charpy Impact." Applied Mechanics and Materials 815 (November 2015): 221–26. http://dx.doi.org/10.4028/www.scientific.net/amm.815.221.
Abstract:
This paper proposes the correlation of absorbed energy with calculated energy using the power spectrum density (PSD) method. The total absorbed energy was obtained using the dial/encoder system may significantly vary depending on the strength and ductility of the material. In addition, according to ASTM E23, over 80% of absorbed energy is inaccurate and approximate. For this reason, we determined the energy collected from the dial/encoder Charpy impact test using the signal processing approach. Strain gauges were connected to the Charpy impact striker and the high frequency data acquisition system in order to capture the dynamic impact strain response. Specimens of an aluminium alloy of 6061-T6 and carbon steel 1050 with different velocities and thicknesses were used in the experiment. The specimens are prepared based on the ASTM E23. A collection of signal was converted from the time domain to the frequency domain by means of PSD method and the area under its plot was used to calculate strain energy. The comparison between energy absorbed during the experiment with PSD peak and the strain energy were performed using different materials, velocities and thicknesses. The total energy absorbed for both material with the PSD peak and the strain energy using the dial/encoder system can be linked by a power law equation with R2 96% and R2 94 %. Thus, the effects of the strain signal pattern and impact duration with different parameters were correlated with the PSD peak and the strain energy. This correlation using PSD can be used as an alternative for the charpy impact test and solve the problem of inaccurate absorbed energy.
20
Ikramov, Rustamjon G., Khurshidbek A. Muminov, Mashkhura A. Nuritdinova, Bobur Q. Sutonov, Oybek T. Kholmirzayev, and A’zamxo’ja A. Mamakhanov. "Dangerous Bonds Individual of Hydrogenated Amorphous Silicon and Defect Absorption Spectra." East European Journal of Physics, no. 4 (December 2, 2023): 244–50. http://dx.doi.org/10.26565/2312-4334-2023-4-30.
Abstract:
In this work, defect absorption spectra for defects characteristic of hydrogenated amorphous silicon are theoretically studied. It is shown that in order to determine defect absorption spectra using the Kubo-Greenwood formula, the indefinite integral in this formula must be written in a certain form. It was discovered that electronic transitions involving defect states are divided into two parts depending on the energy of absorbed photons. The values of the partial defect absorption spectrum at low energies of absorbed photons have almost no effect on the overall defect absorption spectrum. It has been established that the main role in determining the defect absorption spectrum is played by partial spectra determined by optical transitions of electrons between allowed bands and defects. It is shown that with a power-law distribution of the density of electronic states in allowed bands, the spectra of optical transitions between them and defects do not depend on the value of this power.
21
Samaras, Theodoros, Andreas Christ, and Niels Kuster. "Compliance Assessment of the Epithelial or Absorbed Power Density Below 10 GHz Using SAR Measurement Systems." Bioelectromagnetics 42, no. 6 (June 15, 2021): 484–90. http://dx.doi.org/10.1002/bem.22355.
22
Özkan, Ilkan, and Abdurrahman Telli. "The effects of metal type, number of layers, and hybrid yarn placement on the absorption and reflection properties in electromagnetic shielding of woven fabrics." Journal of Engineered Fibers and Fabrics 14 (January 2019): 155892501986096. http://dx.doi.org/10.1177/1558925019860961.
Abstract:
In this study, stainless steel, copper, and silver wires were intermingled with two polyamide 6.6 filaments through the commingling technique to produce three-component hybrid yarns. The produced hybrid yarns were used as weft in the structure of plain woven fabric samples. The electromagnetic shielding effectiveness parameters of samples were measured in the frequency range of 0.8–5.2 GHz by the free space technique. The effects of metal hybrid yarn placement, number of fabric layers, metal types, and wave polarization on the electromagnetic shielding effectiveness and absorption and reflection properties of the woven fabrics were analyzed statistically at low and high frequencies separately. As a result, the samples have no shielding property in the warp direction. Metal types show no statistically significant effect on electromagnetic shielding effectiveness. However, fabrics containing stainless steel have a higher absorption power ratio than copper and silver samples. Double-layer samples have higher electromagnetic shielding effectiveness values than single-layer fabrics in both frequency ranges. However, the number of layers does not have a significant effect on the absorbed and reflected power in the range of 0.8–2.6 GHz. There was a significant difference above 2.6 GHz frequency for absorbed power ratio. An increase in the density of hybrid yarns in the fabric structure leads to an increase in the electromagnetic shielding effectiveness values. Two-metal placement has a higher absorbed power than the full and one-metal placements, respectively. The samples which have double layers and including metal wire were in their all wefts reached the maximum electromagnetic shielding effectiveness values for stainless steel (78.70 dB), copper (72.69 dB), and silver composite (57.50 dB) fabrics.
23
Stachowicz, M. "Effect of Sand Base Grade and Density of Moulding Sands with Sodium Silicate on Effectiveness of Absorbing Microwaves." Archives of Foundry Engineering 16, no. 3 (September 1, 2016): 103–8. http://dx.doi.org/10.1515/afe-2016-0059.
Abstract:
Abstract In the paper, presented is a research on effectiveness of absorbing electromagnetic waves at frequency 2.45 GHz by unhardened moulding sands prepared of three kinds of high-silica base and a selected grade of sodium silicate. Measurements of power loss of microwave radiation (Pin) expressed by a total of absorbed power (Pabs), output power (Pout) and reflected power (Pref) were carried-out on a stand of semiautomatic microwave slot line. Values of microwave power loss in the rectangular waveguide filled with unhardened moulding sands served for determining effectiveness of microwave heating. Balance of microwave power loss is of technological and economical importance for manufacture of high-quality casting moulds and cores of various shapes and sizes. It was found that relative density influences parameters of power output and power reflected from samples of moulding sand placed in a waveguide. Absorption expressed by the parameter Pabs is not related to granularity of high-silica base: fine, medium and coarse. It was found that the semiautomatic microwave slot line supports evaluation of effectiveness of microwave absorption on the grounds of power loss measurements and enables statistic description of influence of relative density of the sandmix on penetration of electromagnetic waves in unhardened moulding sands.
24
Alekseeva, P. M., K. T. Efendiev, T. A. Savelieva, A. S. Moskalev, R. Steiner, and V. B. Loschenov. "Optimization of energy parameters for laser-induced PDT of cervical tissues using numerical simulation and fluorescent monitoring." Laser Physics 33, no. 6 (April 28, 2023): 065602. http://dx.doi.org/10.1088/1555-6611/acce2e.
Abstract:
Abstract The main problem in the photodynamic therapy (PDT) of tumors is insufficient light exposure to tissue or the appearance of undesirable surface effects. The reason is the irregular distribution of the absorbed light dose by depth. The influence of the spot diameter on the relative fluence rate in the near-surface layer of the cervical tissue was studied by Monte Carlo simulation. Photodynamic exposure with chlorine-type photosensitizer (PS) was carried out on the tissue model with laser 660 nm at the same power density with a change in spot diameter from 5 to 15 mm and radiation energy density from 100 to 300 J cm−2. The distributions of the fluorescence indices of the PS and the hemoglobin oxygenation degree by depth were obtained. The dependence of PS photobleaching on the energy density was established at the same power density and different spot diameters. The developed method increased the efficiency of PDT by delivering a sufficient energy density of laser radiation to the entire tumor tissue by depth without thermal damage, that allowed minimizing side effects and prevent possible growth and recurrence of the disease.
25
Kim, Ju Ho, and Chin-Wook Chung. "Plasma and electrical characteristics depending on an antenna position in an inductively coupled plasma with a passive resonant antenna." Plasma Sources Science and Technology 31, no. 1 (January 1, 2022): 015002. http://dx.doi.org/10.1088/1361-6595/ac4146.
Abstract:
Abstract We investigated the plasma and electrical characteristics depending on the antenna position in an inductively coupled plasma with a passive resonant antenna. When the powered antenna and passive resonant antenna are installed near the top plate and in the middle of the cylindrical reactor (setup A), respectively, the ion density at the resonance is about 2.4 times to 9 times higher than that at non-resonance. This is explained by the reduction in power loss in the powered antenna (including the matching circuits) and the increase in power absorbed by the plasma discharge. However, when the powered antenna and passive resonant antenna are interchanged (setup B), the ion density at the resonance is not significantly different from that at the non-resonance. When RF power is changed from 50 to 200 W, the ion density at the resonance of setup B is 1.6 times to 5.4 times higher than at the non-resonance of setup A. To analyse this difference, the profile of the z-axis ion density is measured and the electric and magnetic field simulations are investigated. The results are discussed along with the electron kinetics effect and the coupling loss between the antenna and the metal plate.
26
Eguchi, Takuto, Shinya Kato, Naoki Kishi, and Tetsuo Soga. "Effect of thickness on photovoltaic properties of amorphous carbon/fullerene junction." AIMS Materials Science 9, no. 3 (2022): 446–54. http://dx.doi.org/10.3934/matersci.2022026.
Abstract:
<abstract> <p>All-carbon photovoltaic devices have attracted attention in terms of resources and environment. However, the device application is very limited because of poor performance. In this work, we studied the solar cell characteristics of amorphous carbon (a–C)/fullerene (C<sub>60</sub>) junction when the thickness of the a–C layer was varied. When the thickness of the a–C layer was varied, the short-circuit current density and open-circuit voltage increased with increasing film thickness and then decreased after a certain value. Also, the spectral response measurement results suggest that most of the power generation is due to the light absorbed by the C<sub>60</sub> layer, and that the light absorbed by the a–C layer may contribute little to power generation. This study suggests that the improvement in the electronic properties of a–C is necessary to make a photovoltaic device with high performance.</p> </abstract>
27
Knyazeva, I. R., M. A. Medvedev, L. P. Zharkova, K. V. Afanasyev, M. A. Bolshakov, and V. V. Rostov. "Pulse-repetitive microwave and X-ray exposure on human erythrocyte." Bulletin of Siberian Medicine 8, no. 1 (February 28, 2009): 24–29. http://dx.doi.org/10.20538/1682-0363-2009-1-24-29.
Abstract:
The effects of pulse-repetitive X-ray radiation and microwaves on the suspension of human erythrocyte was investigated in present work taking in to account changing their electrical capacitance. It was shown that the single 5-min exposure of suspension of erythrocyte to pulse periodic x-rays and microwaves causes the changes of the capacitance. The of the effect depends on the radiation type, the pulse repetition frequency, the radiation absorbed dose (in case of x-rays) and power flow density (in the case of microwaves).
28
Diao, Yinliang, Essam A. Rashed, and Akimasa Hirata. "Assessment of absorbed power density and temperature rise for nonplanar body model under electromagnetic exposure above 6 GHz." Physics in Medicine & Biology 65, no. 22 (November 24, 2020): 224001. http://dx.doi.org/10.1088/1361-6560/abbdb7.
29
Bonato, Marta, Laura Dossi, Silvia Gallucci, Martina Benini, Gabriella Tognola, and Marta Parazzini. "Assessment of Human Exposure Levels Due to Mobile Phone Antennas in 5G Networks." International Journal of Environmental Research and Public Health 19, no. 3 (January 29, 2022): 1546. http://dx.doi.org/10.3390/ijerph19031546.
Abstract:
The recent deployment of 5G networks is bringing benefits to the population but it is also raising public concern about human RF-EMF exposure levels. This is particularly relevant considering the next 5G mobile devices, which are placed in close proximity to the subjects. Therefore, the aim of the following paper is focused on expanding the knowledge of the exposure levels in 5G exposure scenarios, specifically for mobile applications, using computational methods. The mobile antenna was designed considering the 5G technology innovations (i.e., mm-wave spectrum, beamforming capability, high gain and wide coverage), resulting in a phased-array antenna with eight elements at the working frequency of 27 GHz. To assess the exposure levels, different types of skin models with different grades of details and layers were considered. Furthermore, not only was the presence of a mobile phone user simulated, but also that of a person in their proximity, who could be hit by the main beam of the phased-array antenna. All the simulations were conducted in Sim4Life platform, where the exposure levels were assessed in terms of absorbed power density averaged over 4 cm2 and 1 cm2, following the ICNIRP guidelines. The results highlighted that the use of the homogeneous skin model led to the absorbed power density peaks being greatly underestimated, with respect to those obtained in multilayer skin models. Furthermore, interestingly, we found that the exposure levels obtained for the person passing nearby were slightly higher than those experienced by the mobile phone user himself. Finally, using the allowed input power for real mobile applications, all the values remained below the limits indicated by the ICNIRP guidelines.
30
Senstius, Mads G., Simon J. Freethy, Joe Allen, and Stefan K. Nielsen. "A radiometer to diagnose parametric instabilities during linear excitation of electron Bernstein waves in the Mega Amp Spherical Tokamak (MAST) Upgrade." Review of Scientific Instruments 93, no. 10 (October 1, 2022): 103522. http://dx.doi.org/10.1063/5.0101785.
Abstract:
Highly overdense magnetically confined fusion plasmas, such as the Mega Amp Spherical Tokamak (MAST) Upgrade, cannot easily be heated using conventional electron cyclotron resonance heating because high density cutoffs block microwave access to the plasma core. Instead, electromagnetic waves can be coupled to electron Bernstein waves (EBWs) through the O-X-B mode coupling scheme, and the EBWs can then be absorbed at higher densities. The excitation of EBWs occurs at the upper hybrid (UH) layer where nonlinear wave interactions, called parametric decay instabilities (PDIs), are known to occur at reduced power thresholds. We present a design for a radiometer to detect PDIs during O-X-B in MAST Upgrade. The radiometer will aid in determining at what power levels PDIs become important as well as inferring various parameters about both electrons and ions near the UH layer. We estimate a gyrotron power density threshold for PDI and expected frequency shifts to be produced in them. The design allows for shifts from several decays involving lower hybrid (LH) waves to be observed.
31
Mantel, N., D. Bowden, S. S. Herashchenko, M. Fursdon, A. D. L. Hancock, I. E. Garkusha, J. Roberts, et al. "Development and testing of an additively manufactured lattice for DEMO limiters." Nuclear Fusion 62, no. 3 (January 26, 2022): 036017. http://dx.doi.org/10.1088/1741-4326/ac486a.
Abstract:
Abstract In the conceptual design of EU-DEMO, damage to plasma-facing components under disruption events is planned to be mitigated by specific sacrificial limiter components. A new limiter concept has been proposed using lattice structures fabricated with tungsten powder by additive manufacturing techniques. The major potential benefits of using a lattice structure for limiters are the possibility to customise the thermal conductivity and structural compliance of these components to manage temperatures and stress within material limits and lower the sensitivity to crack propagation. This paper presents the results of the first investigations into the production, characterisation, and high heat flux testing of these lattices to assess their suitability for DEMO limiters. First stage prototypes have been manufactured from tungsten and tungsten tantalum mixed powder with two distinct laser power bed fusion processes, namely pulsed laser and continuous laser with heated bed. The samples are characterised in terms of mass, volume, density, extent of microcracks and voids, level of un-melted or partially melted particulates, texture and grain size, as well as tantalum segregation when applicable. High transient (0.25 ms) heat load testing, with hydrogen plasma of energy density up to ∼3 MJ m−2 was carried out at Kharkov Institute of Physics and Technology on the quasi-stationary plasma accellerator Kh-50. These tests have shown that the energy absorbed by latticed targets preheated at 500 °C is close to that absorbed by solid tungsten, suggesting that they may be used for limiter applications with the added advantage of adjustment of the heat transfer and stiffness performance by geometry design or material properties.
32
Nassim, Baba Ahmed, Aliane Khaled, and Benmoussat Abderrahim. "Influence of an absorbers GEMPEHD thermal properties on the propagation of heat in a solar sensor." MATEC Web of Conferences 149 (2018): 02046. http://dx.doi.org/10.1051/matecconf/201814902046.
Abstract:
This paper presents an experimental study to measure some physic-chemical properties of a high-density polyethylene geomembane (GEMPEHD) in a temperature range from 300 K to 400 K. The results will yield a dependency between temperature and its properties in order to study an energy and process the thermal aging GEMPEHD on the solar collector. In the energy study, we solve the nonlinear equation of unsteady heat with as main non linearity influence of different properties GEMPEHD on the solar collector and one notes that the GEMPEHD presented a maximum exchange Thermal characterized by high absorption and low reflection. Thus, increasing the power absorbed by the GEMPEHD increases its temperature and the useful power received by the air and then the air temperature. Overall losses increase with the increase of the temperature difference between the GEMPEHD and windows and this increases the efficiency of the solar collector and minimize the entropy of the system. Then the study of thermal aging is dedicated to the interpretation of various analyses on GEMPEHD before and after its use in the solar collector. The thermal aging GEMPEHD in the air is a physical loss and chemical consumption immediately followed by a brutal oxidation of the polymer. The losses would be governed primarily by the chemical consumption of antioxidants. After various tests, we conclude that the value of using the GEMPEHD as absorber in the solar collector is doubly beneficial. First, given its very attractive cost compared to other as efficient absorbers (such as metals) gives good thermal performance of the solar collector even reaching 72%. While the life of the GEMPEHD is rather long (several years).
33
GRESCHIK, F., and H. J. KULL. "Two-dimensional PIC simulation of atomic clusters in intense laser fields." Laser and Particle Beams 22, no. 2 (June 2004): 137–45. http://dx.doi.org/10.1017/s026303460422208x.
Abstract:
Collective absorption of intense laser pulses by atomic clusters is studied by PIC simulations. The cluster is modeled in two-dimensional calculations as a cylindrical plasma column with a diameter of D = 6.4 nm and an initial electron density of ne0 = 1023 cm−3. The frequency and intensity dependence of absorption is discussed. It is found that nonresonant absorption by electron emission increases as a power law with the laser intensity. The absorbed energy per electron reaches a maximum of about Wmax = mωp2D2 (ωp: plasma frequency, m: electron mass) at the intensity where ionization saturates.
34
Kim, K. T., H. W. Kim, H. Y. Chang, B. T. Lim, H. B. Park, and Y. S. Kim. "Corrosion Inhibiting Mechanism of Nitrite Ion on the Passivation of Carbon Steel and Ductile Cast Iron for Nuclear Power Plants." Advances in Materials Science and Engineering 2015 (2015): 1–16. http://dx.doi.org/10.1155/2015/408138.
Abstract:
While NaNO2addition can greatly inhibit the corrosion of carbon steel and ductile cast iron, in order to improve the similar corrosion resistance,ca.100 times more NaNO2addition is needed for ductile cast iron compared to carbon steel. A corrosion and inhibition mechanism is proposed wherebyNO2-ion is added to oxidize. TheNO2-ion can be reduced to nitrogen compounds and these compounds may be absorbed on the surface of graphite. Therefore, since nitrite ion needs to oxidize the surface of matrix and needs to passivate the galvanic corroded area and since it is absorbed on the surface of graphite, a greater amount of corrosion inhibitor needs to be added to ductile cast iron compared to carbon steel. The passive film of carbon steel and ductile cast iron, formed by NaNO2addition showed N-type semiconductive properties and its resistance, is increased; the passive current density is thus decreased and the corrosion rate is then lowered. In addition, the film is mainly composed of iron oxide due to the oxidation byNO2-ion; however, regardless of the alloys, nitrogen compounds (not nitrite) were detected at the outermost surface but were not incorporated in the inner oxide.
35
Ibrahim, Nor Adibah, Tharek Abd Rahman, Razali Ngah, Omar Abd Aziz, and Olakunle Elijah. "Power density of rectangular microstrip patch antenna arrays for 5G indoor base station." Indonesian Journal of Electrical Engineering and Computer Science 19, no. 3 (September 1, 2020): 1367. http://dx.doi.org/10.11591/ijeecs.v19.i3.pp1367-1374.
Abstract:
The fifth-generation (5G) network has been broadly investigated by many researchers. The capabilities of 5G include massive system capacity, incredibly high data rates everywhere, very low latency and the most important point is that it is exceptionally low device cost and low energy consumption. A key technology of 5G is the millimeter wave operating at 28 GHz and 38 GHz frequency bands which enable massive MIMO and small cell base station densification. However, there has been public concern associated with human exposure to electromagnetic fields (EMF) from 5G communication devices. Hence, this paper studies the power density of a 5G antenna array that can be used for the indoor base station. The power density is the amount of power or signal strength absorbed by a receiver such as the human body located a distance from the base station. To achieve this, the design of array antennas using CST software at 28 GHz, fabrication and measurement were carried out in an indoor and hallway environment. The measurement processes were set up at IC5G at UTM Kuala Lumpur in which the distance of the transmitter to receiver where 1 m, 4 m, 8 m, and 10 m. In this study, the measured power density is found to be below the set limit by ICNIRP and hence no health implication is feared. Regardless, sufficient act of cautionary has to be applied by those staying close to small cell base stations and more studies are still needed to ensure the safety of use of 5G base stations.
36
Zhang, Mingwei, Qingbin Meng, and Shengdong Liu. "Energy Evolution Characteristics and Distribution Laws of Rock Materials under Triaxial Cyclic Loading and Unloading Compression." Advances in Materials Science and Engineering 2017 (2017): 1–16. http://dx.doi.org/10.1155/2017/5471571.
Abstract:
To explore the influence of confining pressure on the energy evolution characteristics of loaded rocks, triaxial cyclic loading-unloading experiments on sandstones were carried out under 6 kinds of confining pressures using the axial loading and circumferential deforming control modes. Total energy density, elastic energy density, and dissipated energy density absorbed by rock specimens under different confining pressures were obtained. The confining pressure effect of the evolution process and distribution law in energy accumulation and dissipation was analyzed. Energy conversion mechanism from rock deformation to failure was revealed, and energy conversion equations in different stress-strain stages were established. The method of representing the rock energy accumulation, dissipation, and release behaviors by energy storage limit density, maximum dissipated energy density, and residual elastic energy density was established. The rock showed that, with the increase of confining pressure, the characteristic energy density of rock increased in the power exponent form, and the energy storage limit density increased faster than the maximum dissipated energy density. The greater the confining pressure was, the greater the proportion of elastic energy before peak was. It is indicated that the confining pressure increased the energy inputting intensity, improved the energy accumulating efficiency, and inhibited the energy releasing degree.
37
Yang, Liang, Yunkai Cai, and Lin Lu. "Experimental Study on Simultaneous Desulfurization and Denitrification by DBD Combined with Wet Scrubbing." Applied Sciences 11, no. 18 (September 16, 2021): 8592. http://dx.doi.org/10.3390/app11188592.
Abstract:
A dielectric barrier discharge (DBD) reactor combined with a wet scrubbing tower was used to carry out an experimental study on desulfurization and denitrification. The effects of the packing type, packing height, spray density, mass fraction of the NaOH solution, discharge power in the DBD reactor, and simulated flue gas flow rate on the desulfurization and denitrification efficiency were analyzed, along with the influence weight of each factor, using orthogonal testing. The experimental results showed that SO2 was easily absorbed by the scrubbing solution, while the desulfurization efficiency remained at a high level (97–100%) during the experiment. The denitration efficiency was between 12 and 96% under various operating conditions. Denitration is the key problem in this system. The influence weights of the DBD power, simulated flue gas flow rate, mass fraction of the NaOH solution, spray density, packing type, and packing height on the denitration efficiency were 56.96%, 18.02%, 11.52%, 5.02%, 4.33%, and 4.16%, respectively. This paper can provide guidance to optimize the desulfurization and denitrification efficiency of this DBD reactor combined with a wet scrubbing system.
38
Jiménez, Pedro, Mario Merino, and Eduardo Ahedo. "Wave propagation and absorption in a helicon plasma thruster and its plume." Plasma Sources Science and Technology 31, no. 4 (April 1, 2022): 045009. http://dx.doi.org/10.1088/1361-6595/ac5ecd.
Abstract:
Abstract A two-dimensional, full-wave, frequency domain, cold plasma model is used to study electromagnetic power propagation and absorption in a helicon plasma thruster, including its far plume region and surrounding space. Results show that a fraction of power is absorbed in the plume region, and that the power deposition in the source is essentially unperturbed by the simulation domain size, the presence of metallic obstacles, or the plasma density in the environment. An electron–cyclotron resonance (ECR) surface always exists downstream that effectively prevents radiation to the space beyond along the plume. In the presence of an overdense environmental plasma, like the one expected in a vacuum chamber, fields are fully evanescent beyond this transition, and vacuum chamber boundary conditions affect but little the wavefields before this surface. In the absence of an environmental plasma, a double wave regime transition exists at the interface between the plasma and vacuum that hinders accurate numerical simulation in the plume region.
39
Divac, Srđan, Marko Rosić, Stan Zurek, Branko Koprivica, Krzysztof Chwastek, and Milan Vesković. "A Methodology for Calculating the R-L Parameters of a Nonlinear Hysteretic Inductor Model in the Time Domain." Energies 16, no. 13 (July 5, 2023): 5167. http://dx.doi.org/10.3390/en16135167.
Abstract:
The aim of this paper is to present a methodology for the calculation of the R-L parameters of a model of a nonlinear hysteretic inductor. The methodology is based on the analysis of the instantaneous magnetising power calculated from the hysteresis loop of the inductor and is completely developed in the time domain. The instantaneous magnetising power is firstly separated into the oscillatory and absorbed components. Thereafter, the parameter R is calculated using the absorbed component and the parameter L using the oscillatory component. The methodology is validated through the comparison of the results for parameters R and L obtained with the proposed method and the existing method based on the Poynting theorem. The validation is demonstrated on the specific simulated cases with idealised parameters of a nonlinear circuit. Additionally, the paper presents results for the parameters R and L calculated from the hysteresis loops measured at frequencies from 1 to 300 Hz. Furthermore, the fitting functions representing the variation of these parameters with the rate of change of magnetic flux density, and the corresponding results, are presented in the paper. A discussion of all the results presented and applicability of the methodology proposed, as well as the concluding remarks, are given thereafter.
40
Martín Ortega, Álvaro, Ana Lacoste, and Tiberiu Minea. "Hybrid modelling of a high-power X-ray attenuator plasma." Journal of Synchrotron Radiation 25, no. 3 (March 27, 2018): 671–85. http://dx.doi.org/10.1107/s1600577518002679.
Abstract:
X-ray gas attenuators act as stress-free high-pass filters for synchrotron and free-electron laser beamlines to reduce the heat load in downstream optical elements without affecting other properties of the X-ray beam. The absorption of the X-ray beam triggers a cascade of processes that ionize and heat up the gas locally, changing its density and therefore the X-ray absorption. Aiming to understand and predict the behaviour of the gas attenuator in terms of efficiencyversusgas pressure, a hybrid model has been developed, combining three approaches: an analytical description of the X-ray absorption; Monte Carlo for the electron thermalization; and a fluid treatment for the electron diffusion, recombination and excited-states relaxation. The model was applied to an argon-filled attenuator prototype built and tested at the European Synchrotron Radiation Facility, at a pressure of 200 mbar and assuming stationary conditions. The results of the model showed that the electron population thermalizes within a few nanoseconds after the X-ray pulse arrival and it occurs just around the X-ray beam path, recombining in the bulk of the gas rather than diffusing to the attenuator walls. The gas temperature along the beam path reached 850 K for 770 W of incident power and 182 W m−1of absorbed power. Around 70% of the absorbed power is released as visible and UV radiation rather than as heat to the gas. Comparison of the power absorption with the experiment showed an overall agreement both with the plasma radial profile and power absorption trend, the latter within an error smaller than 20%. This model can be used for the design and operation of synchrotron gas attenuators and as a base for a time-dependent model for free-electron laser attenuators.
41
Alnoman, Rua B., Eman Nabil, Shazia Parveen, Mohamed Hagar, Mohamed Zakaria, and Ahmed A. Hasanein. "Synthesis and Computational Characterization of Organic UV-Dyes for Cosensitization of Transparent Dye-Sensitized Solar Cells." Molecules 26, no. 23 (December 3, 2021): 7336. http://dx.doi.org/10.3390/molecules26237336.
Abstract:
The fabrication of colorless and see-through dye-sensitized solar cells (DSCs) requires the photosensitizers to have little or no absorption in the visible light region of the solar spectrum. However, a trade-off between transparency and power conversion efficiency (PCE) has to be tackled, since most transparent DSCs are showing low PCE when compared to colorful and opaque DSCs. One strategy to increase PCE is applying two cosensitizers with selective conversion of the UV and NIR radiation, therefore, the non-visible part only is absorbed. In this study, we report synthesis of novel five UV-selective absorbers, based on diimide and Schiff bases incorporating carboxyl and pyridyl anchoring groups. A systematic computational investigation using density functional theory (DFT) and time-dependent DFT approaches was employed to evaluate their prospect of application in transparent DSCs. Experimental UV/Vis absorption spectra showed that all dyes exhibit an absorption band covering the mid/near-UV region of solar spectrum, with a bathochromic shift and a hyperchromic shifts for Py-1 dye. Computational results showed that the studied dyes satisfied the basic photophysical and energetics requirements of operating DSC as well as the stability and thermodynamical spontaneity of adsorption onto surface of TiO2. However, results revealed outperformance of the thienothiophene core-containing Py-1 UV-dye, owing to its advantageous structural attributes, improved conjugation, intense emission, large Stokes shift and maximum charge transferred to the anchor. Chemical compatibility of Py-1 dye was then theoretically investigated as a potential cosensitizer of a reference VG20-C2 NIR-dye. By the judicious selection of pyridyl anchor-based UV-absorber (Py-1) and carboxyl anchor-based NIR-absorber (VG20), the advantage of the optical complementarity and selectivity of different TiO2-adsorption-site (Lewis- and Bronsted-acidic) can be achieved. An improved overall PCE is estimated accordingly.
42
Tan, Jian, Henk Polinder, Antonio Jarquin Laguna, Peter Wellens, and Sape A. Miedema. "The Influence of Sizing of Wave Energy Converters on the Techno-Economic Performance." Journal of Marine Science and Engineering 9, no. 1 (January 5, 2021): 52. http://dx.doi.org/10.3390/jmse9010052.
Abstract:
Currently, the techno-economic performance of Wave Energy Converters (WECs) is not competitive with other renewable technologies. Size optimization could make a difference. However, the impact of sizing on the techno-economic performance of WECs still remains unclear, especially when sizing of the buoy and Power Take-Off (PTO) are considered collectively. In this paper, an optimization method for the buoy and PTO sizing is proposed for a generic heaving point absorber to reduce the Levelized Cost Of Energy (LCOE). Frequency domain modeling is used to calculate the power absorption of WECs with different buoy and PTO sizes. Force constraints are used to represent the effects of PTO sizing on the absorbed power, in which the passive and reactive control strategy are considered, respectively. A preliminary economic model is established to calculate the cost of WECs. The proposed method is implemented for three realistic sea sites, and the dependence of the optimal size of WECs on wave resources and control strategies is analyzed. The results show that PTO sizing has a limited effect on the buoy size determination, while it can reduce the LCOE by 24% to 31%. Besides, the higher mean wave power density of wave resources does not necessarily correspond to the larger optimal buoy or PTO sizes, but it contributes to the lower LCOE. In addition, the optimal PTO force limit converges at around 0.4 to 0.5 times the maximum required PTO force for the corresponding sea sites. Compared with other methods, this proposed method shows a better potential in sizing and reducing LCOE.
43
Kobayashi, Hidetoshi, Keitaro Horikawa, Keiko Watanabe, Kinya Ogawa, and Kensuke Nozaki. "Dynamic and Quasi-Static Compression Tests for Polylactic Acid Resin Foam." Materials Science Forum 706-709 (January 2012): 745–50. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.745.
Abstract:
In this study, the effect of strain rate on the strength and the absorbed energy of polylactic acid resin foam (PLA-foam), which is generally known as one of carbon-neutral and environmentally-friendly polymers, were examined by a series of compression tests at various strain rates from 0.001 to 750 s-1. For the measurements of the impact load and the displacement of specimen, a special load cell and a high-speed video camera were used, respectively. The flow stress of the PLA-foam strongly depends upon not only strain rate but also density of specimens. Thus, a new technique to eliminate the effect of the difference in the specimen density was proposed and successfully applied. It was also found that the strain-rate dependency of PLA-foam can be expressed by a simple power law.
44
Di Barba, Paolo, Łukasz Januszkiewicz, Jarosław Kawecki, and Maria Evelina Mognaschi. "Electromagnetic Wave Absorption in the Human Head: A Virtual Sensor Based on a Deep-Learning Model." Sensors 23, no. 6 (March 15, 2023): 3131. http://dx.doi.org/10.3390/s23063131.
Abstract:
Determining the amount of electromagnetic wave energy absorbed by the human body is an important issue in the analysis of wireless systems. Typically, numerical methods based on Maxwell’s equations and numerical models of the body are used for this purpose. This approach is time-consuming, especially in the case of high frequencies, for which a fine discretization of the model should be used. In this paper, the surrogate model of electromagnetic wave absorption in human body, utilizing Deep-Learning, is proposed. In particular, a family of data from finite-difference time-domain analyses makes it possible to train a Convolutional Neural Network (CNN), in view of recovering the average and maximum power density in the cross-section region of the human head at the frequency of 3.5 GHz. The developed method allows for quick determination of the average and maximum power density for the area of the entire head and eyeball areas. The results obtained in this way are similar to those obtained by the method based on Maxwell’s equations.
45
Veličković, Dragan, Milanka Jevtić, Nebojša Milosavljević, Dragana Stanisavljević, Dejan Davidović, Sofija Đorđević, and Milena Nikolova. "Experimental investigation of technological parameters of herbal drugs for the extraction and distillation process." Advanced Technologies 12, no. 1 (2023): 29–37. http://dx.doi.org/10.5937/savteh2301029v.
Abstract:
The parameters of herbal drugs that are important for technological processes, especially for extraction and distillation processes were examined: bulk density, tapped density, compressibility index, Hausner ratio, and solvent absorption power. The methods described in the pharmacopoeia were used for the examination. Based on the values of bulk density and tapped density, the volume of the device is planned, ie. the size of the batch for extraction or distillation. These parameters were shown to have lower values for flower, leaf and herb, and higher values for fruit and root. Also, the compressibility index depends on the degree of fragmentation and the Hausner ratio. The results showed that these parameters have lower values for fruit and root. Solvent absorption power is the volume of solvent absorbed by a certain amount of herbal drug. Two solvents with differences in concentration were used: ethanol (aqueous solution: 96 vol.%, 70 vol.% and 50 vol.%) and distilled water. At the end of the technological process, a part of the solvent/ extract can be extracted from the spent plant material by pressing or vacuum filtration. The other part is difficult to get rid of the spent plant material and is irreversibly thrown away. In all tested herbal drugs, it is noticeable that the solvent absorption power increases with the increasing polarity of the solvent. Also, the less polar solvent EtOH 96% is more selective in terms of plant part. As the polarity of the solvent increases, it does not matter which part of the plant is extracted.
46
Nga, Do Thi, Le Ba Nam, To Thi Thao, and Vu Thi Thuy Duong. "PLASMONIC PHOTOTHERMAL HEATING OF GOLD NANOSHELL SOLUTIONS." Communications in Physics 30, no. 4 (November 16, 2020): 363. http://dx.doi.org/10.15625/0868-3166/30/4/15152.
Abstract:
We present a theoretical approach to theoretically investigate how gold core-shellnanoparticles dispersed in water thermally respond to near-infrared-regime laser illumination. First, the absorption cross section of gold nanostructures is calculated using Mie theory. Second, we determine the absorbed power density when the solution is exposed by the laser light. Here, the solution of nanostructures is assumed to be uniform and homogenous. Third, we analytically solve the transient bioheat equation to calculate time-dependent temperature increase. Our theoretical calculations quantitatively agree with previous experiments without any adjustable parameter.This approach would provide a reliable tool to understand photothermal effects in unexplored structures.
47
Glicksman, L. R., J. Azzola, and J. Modlin. "Fluidized Bed Solar Collector." Journal of Solar Energy Engineering 110, no. 4 (November 1, 1988): 321–26. http://dx.doi.org/10.1115/1.3268274.
Abstract:
An air fluidized bed, contained in the wall cavity of an exterior building wall, forms the basis of a new solar collector design which is simpler than a water-cooled collector and has a thermal performance superior to that of an air-cooled collector. The fluidized bed serves as an intermediate heat transfer medium between a solar flux absorbed on the external building surface and a liquid thermal transfer loop. Fluidized beds yield heat-transfer coefficients an order of magnitude higher than single phase air flow. Low density particles are used in the bed to minimize power consumption. When defluidized, the bed acts as a good thermal insulator. Recent experimental results are presented for the heat-transfer coefficients of the immersed tubes, bounding walls, the effective conductivity of the bed, and the overall full-scale thermal design efficiency for various low density materials. Structural and power consumption performance is examined as well. An integrated fluidized bed solar collector design is proposed and compared with representative water and air collector designs.
48
Masoura, V. A., G. Mountrichas, I. Georgantopoulos, and M. Plionis. "Relation between AGN type and host galaxy properties." Astronomy & Astrophysics 646 (February 2021): A167. http://dx.doi.org/10.1051/0004-6361/202039238.
Abstract:
We use 3213 active galactic nuclei (AGNs) from the XMM-XXL northern field to investigate the relation of AGN type with host galaxy properties. Applying a Bayesian method, we derive the hardness ratios, and through these the hydrogen column density (NH) for each source. We consider those with NH > 1021.5 cm−2 as absorbed sources (type 2). We examine the star formation rate (SFR) and the stellar mass (M*) distributions for both absorbed and unabsorbed sources. Our work indicates that there is no significant link between AGN type and these host galaxy properties. Next, we investigate whether the AGN power, as represented by its X-ray luminosity (LX) correlates with any deviation of the host galaxy’s place from the so-called main sequence of galaxies, and we examine this separately for the obscured and the unobscured AGN populations. To take into account the effect of M* and redshift on SFR, we use the normalised SFR (SFRnorm). We find that the correlation between LX and SFRnorm follows approximately the same trend for both absorbed and unabsorbed sources, a result that favours the standard AGN unification models. Finally, we explore the connection between the obscuration (NH) and the SFR. We find that there is no relation between them, suggesting that obscuration is not related to the large-scale SFR in the galaxy.
49
Su, Zi-Xuan, De-Hua Shi, Yong-Xin Liu, Kai Zhao, Fei Gao, and You-Nian Wang. "Radially-dependent ignition process of a pulsed capacitively coupled RF argon plasma over 300 mm-diameter electrodes: multi-fold experimental diagnostics." Plasma Sources Science and Technology 30, no. 12 (December 1, 2021): 125013. http://dx.doi.org/10.1088/1361-6595/ac3e3f.
Abstract:
Abstract A synergistic combination of multi-diagnostic methods are proposed to investigate temporal evolution of electrical and plasma parameters at various radial positions over 300 mm-diameter electrodes during the pre-ignition, ignition, and post-ignition phases of a pulsed capacitively coupled radio-frequency (RF) argon discharge. The electron density, n e, and the optical emission intensity (OEI) of argon at 750.4 nm at different radial positions are measured time-resolved by using a hairpin probe and an optical probe, respectively. A B-dot probe is employed to determine the waveforms of the azimuthal magnetic field at different radii, from which the waveforms of the axial current density at corresponding radial positions are derived based on Ampere’s law. Then, the time evolution of the power density at various radii can be calculated, provided that the voltage drop between the electrodes is independent of radius. Meanwhile, the time-dependent total power deposited into the reactor is calculated with the voltage and the current waveforms measured by a voltage and a current probe at the power feeding point. It was found that during pre-ignition phase, the OEI and n e cannot be measurable due to extremely low power deposition when the system exhibits pure capacitive impedance. During the ignition phase, the OEI, the power density, and the current density exhibit the most significant increase at the electrode center, while the time evolution of n e measured by the hairpin probe seems to exhibit a relatively weak radial dependence during this phase. In particular, at r ⩽ 8 cm, the OEI at every radius was observed to change with time in the same manner as the power density during the ignition phase, because the RF power is absorbed primarily by electrons, which dissipate their energy via inelastic collisions. Shortly, the profile of n e becomes edge-high during the post-ignition phase and remains thereafter until the end of the pulse-on period. Methodologically, the synergistic diagnostics lay the foundation for extensive studies on spatiotemporal evolution of plasma ignition process under broader conditions, e.g. electronegative gas, lower working gas pressure and very high driving frequency, widely used by practical etching process.
50
Koshiji, Hayato, Tomomasa Ohkubo, Takumi Shimoyama, Takeru Nagai, Ei-ichi Matsunaga, Yuji Sato, and Thanh-Hung Dinh. "Analysis of Vase Shaped Pumping Cavity for Solar-Pumped Laser." Journal of Advanced Computational Intelligence and Intelligent Informatics 25, no. 2 (March 20, 2021): 242–47. http://dx.doi.org/10.20965/jaciii.2021.p0242.
Abstract:
Although sunlight is a promising renewable energy source, the light is incoherent and difficult to use directly. Therefore, a solar-pumped laser, which directly converts sunlight into coherent laser light of, is a promising technology. A solar-pumped laser collects sunlight into the laser medium to realize laser oscillation. In order to realize an efficient solar-pumped laser system, it is necessary to design a pumping cavity that absorbs maximal sunlight into the laser medium with minimal thermal shock. In this research, the pumping cavity shape was studied using a numerical ray tracing simulation. As a result, it was found that a cone shaped pumping cavity can be expected to improve the absorption rate by approximately 30% over a cylindrically shaped pumping cavity. Furthermore, the absorption power density distribution can be flattened by a vase shaped pumping cavity, while maintaining the same absorption efficiency. The vase shaped pumping cavity has almost half the dispersion of the absorbed power density in the laser medium when compared with the cone shaped pumping cavity.