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1
Atalla, Noureddine, e Alain Berry. "Acoustic Radiation from a Coupled Planar Semi-Complex Structure in Heavy Fluid". Journal of Ship Research 38, n. 03 (1 settembre 1994): 213–24. http://dx.doi.org/10.5957/jsr.1994.38.3.213.
Testo completoAbstract (sommario):
A mathematical model is derived to address the vibrations and sound radiation into a dense fluid, of a coupled system consisting of two semi-complex plates (i.e., supporting added mass, stiffeners, and having arbitrary elastic boundary conditions) linked in four points through multistage suspensions elements. The supporting plate is subjected to point, line or surface harmonic excitation, while the radiating plate is excited through the suspensions. Both plates are assumed to be baffled, and the radiating plate is fluid loaded. The model is based on a variational approach for the plates, and a matrix transfer approach is used to handle the coupling between the two-plates. The solution is found using a Rayleigh-Ritz expansion in terms of polynomial trial functions which are shown to allow for the arbitrary elastic boundary conditions and to facilitate the calculation of the radiation impedance matrix. The vibrations and noise design of the system is discussed. The main design indicators are the force transmissibilities between the different excitation and attachment points, the mean square velocity, the radiated power and the radiation efficiency of the radiating plate. Numerical examples are presented to show the effects of fluid loading and different design parameters (plates thickness, boundary conditions, added mass, stiffeners, etc.) on the radiated sound.
2
Taratorin, Andrey, e Vladimir Tupov. "PETAL-SHAPED SILENCERS USAGE FOR NOISE REDUCTION IN CYLINDRICAL CHANNELS". VOLUME 39, VOLUME 39 (2021): 99. http://dx.doi.org/10.36336/akustika20213999.
Testo completoAbstract (sommario):
The article presents data on the results of petal-shaped silencer mathematical modeling. Dissipative silencers of complex shapes are the most promising technology. This design allows for achieving the required noise reduction. At the same time, geometric shape optimization allows reducing the aerodynamic drag to the smallest values. The article compares the variants of the silencer with the rotation angles of the plates 45 and 70 degrees. The use of such plates allows you to increase the acoustic efficiency of the silencer by eliminating the radiation effect. In the article, there are the results of noise calculation from a dry cooling tower. The use of a petal-shaped silencer will significantly increase acoustic efficiency. The extra aerodynamic drag will be minimal. For comparison presented the results of modeling a cylindrical silencer. The cylindrical silencer has an equal through-section and long. Justified the approach to choosing the most preferred option. The initial velocity field of the gas or air flow in the channel determines the choice of silencer design.
3
Wen, Hua Bing, Lin Bo Liu, Zi Long Peng e Qi Dong Zhong. "Research on the Effects of Blocking Mass on Vibration Resistance Performance of L-Shaped Plates". Applied Mechanics and Materials 482 (dicembre 2013): 131–35. http://dx.doi.org/10.4028/www.scientific.net/amm.482.131.
Testo completoAbstract (sommario):
The theory of vibration resistance of blocking mass at the corner interface of L-shaped plates is put forward from the perspective of wave approach. The equation of transmission and reflection coefficients of flexure wave is deduced by the presented theory. Based on FE/SEA method, the vibration resistance performance of the hollow blocking mass at the corner interface of L-shaped plates was studied through numerical simulation. The results show that the hollow blocking mass can impede the propagation of the high frequency vibration waves, reduce the vibration and sound radiation of the latter plate, and increase the influence of the reflection waves on the former plate. However, the overall radiant energy is basically identical to the L-shaped plates without the hollow blocking mass.
4
Tenenbaum, Roberto A., e Marcelo Bruno S. Magalhães. "A New Technique to Identify Arbitrarily Shaped Noise Sources". Shock and Vibration 13, n. 4-5 (2006): 219–32. http://dx.doi.org/10.1155/2006/231625.
Testo completoAbstract (sommario):
Acoustic intensity is one of the available tools for evaluating sound radiation from vibrating bodies. Active intensity may, in some situations, not give a faithful insight about how much energy is in fact carried into the far field. It was then proposed a new parameter, the supersonic acoustic intensity, which takes into account only the intensity generated by components having a smaller wavenumber than the acoustic one. However, the method is only efective for simple sources, such as plane plates, cylinders and spheres. This work presents a new technique, based on the Boundary Elements Method and the Singular Value Decomposition, to compute the supersonic acoustic intensity for arbitrarily shaped sources. The technique is based in the Kirchoff-Helmholtz equation in a discretized approach, leading to a radiation operator that relates the normal velocity on the source's surface mesh with the pressure at grid points located in the field. Then, the singular value decomposition technique is set to the radiation operator and a cutoff criterion is applied to remove non propagating components. Some numerical examples are presented.
5
García A., Carlos, Nicolas Dauchez e Gautier Lefebvre. "Radiation of thin complex plates estimated with the landscape of localisation theory". Journal of the Acoustical Society of America 151, n. 4 (aprile 2022): A167. http://dx.doi.org/10.1121/10.0010996.
Testo completoAbstract (sommario):
The landscape of localisation is a practical tool that enables the prediction of the geographical localisation of localized modes and helps us to understand the transition between localized and delocalised states. Moreover, approximations based on the Rayleigh quotient and on a variant of Weyl’s law are employed to predict the eigenfrequencies for the Schro ¨ dinger operator in quantum mechanics, but they are also valid for the Laplace and biharmonic operators, which characterize the behaviour of most dynamical systems in acoustics and vibrations. When studying the acoustic radiation from a vibrating structure, three global parameters are key indicators: the mean squared velocity, the acoustic radiated power, and the radiation efficiency. The literature on this subject is very vast for the plate case, where for simple geometries, it is still possible to derive analytical solutions or, at least, very useful approximations. For more complex structures, numerical simulations seem to be appropriate for lack of a simpler solution. In this context, this work aims to give some light to create a direct relationship between these global parameters and the landscape of localisation function, based on the multipolar radiation behaviour presented by localized modes and estimated by geometrical means.
6
Oji, Tatsuo, Stephen Q. Dornbos, Keigo Yada, Hitoshi Hasegawa, Sersmaa Gonchigdorj, Takafumi Mochizuki, Hideko Takayanagi e Yasufumi Iryu. "Penetrative trace fossils from the late Ediacaran of Mongolia: early onset of the agronomic revolution". Royal Society Open Science 5, n. 2 (febbraio 2018): 172250. http://dx.doi.org/10.1098/rsos.172250.
Testo completoAbstract (sommario):
The Cambrian radiation of complex animals includes a dramatic increase in the depth and intensity of bioturbation in seafloor sediment known as the ‘agronomic revolution’. This bioturbation transition was coupled with a shift in dominant trace fossil style from horizontal surficial traces in the late Precambrian to vertically penetrative trace fossils in the Cambrian. Here we show the existence of the first vertically penetrative trace fossils from the latest Ediacaran: dense occurrences of the U-shaped trace fossil Arenicolites from late Precambrian marine carbonates of Western Mongolia. Their Ediacaran age is established through stable carbon isotope chemostratigraphy and their occurrence stratigraphically below the first appearance of the trace fossil Treptichnus pedum . These Arenicolites are large in diameter, penetrate down to at least 4 cm into the sediment, and were presumably formed by the activity of bilaterian animals. They are preserved commonly as paired circular openings on bedding planes with maximum diameters ranging up to almost 1 cm, and as U- and J-shaped tubes in vertical sections of beds. Discovery of these complex penetrative trace fossils demonstrates that the agronomic revolution started earlier than previously considered.
7
Atalla, N., e J. Nicolas. "A Formulation for Mean Flow Effects on Sound Radiation from Rectangular Baffled Plates with Arbitrary Boundary Conditions". Journal of Vibration and Acoustics 117, n. 1 (1 gennaio 1995): 22–29. http://dx.doi.org/10.1115/1.2873863.
Testo completoAbstract (sommario):
A general formulation of the sound radiation from fluid-loaded rectangular baffled plates with arbitrary boundary conditions has been developed by Berry et al. (JASA, Vol. 90, No. 4, Pt. 2, 1991). In this paper, an extension of this formulation to inviscid, uniform subsonic flow is considered. The analysis is based on a variational formulation for the transverse vibrations of the plate and the use of the extended, to uniformly moving media, form of the Helmholtz integral equation. The formulation shows explicitly the effect of the flow in terms of added mass, and radiation resistance. Furthermore, it avoids the difficult problem of integration in the complex domain, typical of the wavenumber transform approaches to fluid-loading problems. Comparison of the acoustic radiation impedance with existing studies supports the validity of the approach. The details of the formulation and its numerical implementation is exposed and a discussion of the flow effects on the radiation impedance of a rectangular piston is presented. It is shown that subsonic mean flow increases the modal radiation resistance at low frequencies and affects added mass more strongly than it affects radiation resistance.
8
Putra, Azma, Nurain Shyafina, Noryani Muhammad, Hairul Bakri e Noor Fariza Saari. "Development of Hybrid Semi-Analytical and Finite Element Analysis to Calculate Sound Radiation from Vibrating Structure". Advanced Materials Research 845 (dicembre 2013): 71–75. http://dx.doi.org/10.4028/www.scientific.net/amr.845.71.
Testo completoAbstract (sommario):
Simple analytical model of plate dynamics usually applies for rectangular plate with simply supported edges. Analytical model of sound radiation from rectangular plate is also convenient, but not for other geometries and other boundary conditions. This paper presents a hybrid mathematical model which combines a semi-analytical model with the Finite Element Analysis (FEA) method to determine sound radiation from a vibrating structure. The latter is employed to calculate the vibration velocity of a structure with a rather complex geometry. The results are then used as the input in the semi-analytical model to calculate the radiated sound pressure through the Rayleigh integral. Results from the proposed model are presented here for the radiation efficiency of rectangular plates with different boundary conditions.
9
Sedlmayr, Erwin. "From Molecules to Grains". International Astronomical Union Colloquium 146 (1994): 163–85. http://dx.doi.org/10.1017/s025292110002131x.
Testo completoAbstract (sommario):
Cosmic dust is an ubiquiteous component of the interstellar medium, the presence of which has severe bearings both upon the observations and upon the physical description and realistic modelling of astronomical objects. In most dusty objects, the grain component is intimately interwoven with the gas component and the radiation field, and, hence strongly affects the thermodynamical, the hydrodynamical and the chemical structure of the object. Therefore any consistent description of the astrophysical dust complex has to rely upon a treatment where these aspects are properly taken into account. In general this complex comprises the following problems:–Formation of small stable molecular clusters out of the gaseous phase–Growth of these clusters to macroscopic specimens (primary condensates: grains, plates, etc.)–Destruction of grains (e.g. thermal evaporation, sputtering, shattering), and–Physical and chemical processing of already existing grains (e.g. coagulation, chemical and thermal transformation, etc....).
10
Ibragimov, Renat F., Yakov A. Kokorev, Anastasia P. Denisenko, Elena V. Ryabeva, Valery T. Samosadny e Hamza Hasnaoui. "Experimental determination of the induced activity in activation detectors of a complex geometric shape". Nuclear Energy and Technology 6, n. 3 (11 settembre 2020): 149–54. http://dx.doi.org/10.3897/nucet.6.57738.
Testo completoAbstract (sommario):
The paper presents the results of experimental determination of the induced activity in copper-/aluminum-based activation detectors when irradiated with neutrons with energies of about 14 MeV. The activation detectors were square-shaped metal plates with a thickness from 1.0 to 1.5 mm and a side size about 5.0 cm. These dimensions significantly exceed those of the detectors that are used in the research of high-intensity neutron fluxes. The detectors described in this work can be used for studying low-intensity neutron fluxes (with a flux density of up to 106 n/cm2∙s). It is shown that, when working with such detectors, it is possible to apply the usual methods for calculating the induced activity in thin activation detectors, with corrections that take into account the emerging features of the ‘neutron source - activation detector’ and ‘activation detector - secondary radiation detector’ geometries. The effects of absorption of primary and secondary radiation by the detector substance are also revealed. The Geant4 tools were used for calculating the geometric factors and theoretical induced activity. The study confirms the applicability of such activation detectors for solving the problem of determining the yield of neutrons with energies of about 14 MeV from a neutron generator target. The results of the experiments coincide, within the margin of error, with the results of simulations performed using the Geant4 tools.
11
Besserguenev, V. G., R. J. F. Pereira, M. C. Mateus, I. V. Khmelinskii, R. C. Nicula e E. Burkel. "TiO2thin film synthesis from complex precursors by CVD, its physical and photocatalytic properties". International Journal of Photoenergy 5, n. 2 (2003): 99–105. http://dx.doi.org/10.1155/s1110662x03000205.
Testo completoAbstract (sommario):
PhotocatalyticTiO2films on glass and quartz plates were obtained by the chemical vapour deposition using Ti(dpm)2(Opri)2complex compound (CC-CVD method) in a standard vacuum apparatus at 1.2–2.0 × 10-4 mbar. The substrate temperature was stabilised in the range of 450–600∘C. The growth rate varied from several nanometres to several dozen of nanometres per minute. Structural information onTiO2thin films was obtained from synchrotron radiation experiments. High-resolution grazing incidence X-ray diffraction (GIXRD) experiments were performed at the high-resolution powder diffractometer at the DESY/HASYLAB beamline B2 (Hamburg, Germany). Thin films deposited on either single-crystal Si wafers or on amorphous quartz substrates were analysed. The photocatalytic activity of theTiO2thin films was studied using a photocatalytic reactor. The fungicide Fenarimol was chosen as chemical indicator and its degradation kinetics was followed by High-Performance Liquid Chromatography (HPLC).
12
Ahmed, E. S. "Conformal Band-Notch UWB Monopole Antenna on Finite Cylindrical Substrates". Engineering, Technology & Applied Science Research 3, n. 3 (3 giugno 2013): 440–45. http://dx.doi.org/10.48084/etasr.332.
Testo completoAbstract (sommario):
A microstrip-fed new UWB monopole antenna with a band-notch characteristic mounted on the finite cylindrical surface is presented. The proposed antenna consists of a rectangular metal radiation patch fed by a 50 ohm microstrip line and a rectangular ground plane. To achieve ultra-wideband, three modifications are introduced. The first one is to blend the upper and lower corners of the radiating plates. The second one is to remove a circular section from the radiating metal. The third one is to blend the upper corners of the ground plane. The antenna is designed on a substrate with dielectric constant εr=3 and 1.6 mm height. The proposed antenna is conformed on finite cylindrical substrates of radiuses 4, 5 and 6 cm. The cylindrical structures were simulated through CST microwave studio finite element package. The simulation results, obtained via CST package on the return losses, VSWR and radiation pattern of the antenna are presented. For both planar and conformal antennas, results show that the impedance bandwidth of the designed antenna is from 2-18 GHz with a return loss less than -10 dB (VSWR<2) and a band rejection of 5-6 GHz for wireless LAN (WLAN), that includes the band 5.15-5.825 GHz limited by IEEE 802.11.a and HIPERLAN/2 with return loss greater than -10dB. The proposed simple shaped conformal antenna provides a good radiation pattern and gain between 3.84 and 5.96 dBi over the entire frequency band excluding the rejected band.
13
Maurerlehner, Paul, Stefan Schoder, Sebastian Floss, Johannes Tieber, Helfried Steiner, Günter Brenn e Manfred Kaltenbacher. "Validation setup for the investigation of aeroacoustic and vibroacoustic sound emission of confined turbulent flows". INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, n. 6 (1 agosto 2021): 519–25. http://dx.doi.org/10.3397/in-2021-1498.
Testo completoAbstract (sommario):
Confined flows induce sound at certain flow conditions, which can be annoying in electric vehicles due to the absence of combustion noise. Noise in internal flow may occur due to unfavorable flow-guiding geometries caused by the complex packaging required in engine compartments of modern vehicles. The flow-induced sound is emitted at duct openings (e.g., ventilation inside the passenger cabin). It also originates from the vibroacoustic emissions of the flow-guiding structure excited by the flow. We propose a modular validation procedure for aeroacoustic simulations of confined flows. The experimental setup includes the vibroacoustic emission of the involved flow-guiding structure. The test rig consists of a sensor system, a high-pressure blower, modular pipe sections, and absorbers, which decouple the system from blower noise and avoid acoustic reflections at the pipe exit. A sufficiently long straight inlet section ensures fully developed flow conditions entering the investigated region. For capturing the vibroacoustic sound radiation of the flow-guiding structure, the measurement object and the surrounding microphones are encapsulated in a wooden box, lined with micro-perforated plates. Measurement results of a straight pipe and a pipe with a half-moon-shaped orifice are presented. Additionally, the sound generation is reproduced by Lighthill's aeroacoustic analogy applying a hybrid approach.
14
Fedosenko, V. S., M. M. Iji, A. A. Lozovenko e G. G. Gorokh. "Bismuth Oxide-based Matrix Nanosystems for X-ray Contrast Diagnostics and Protection from Ionizing Radiation". Doklady BGUIR 21, n. 1 (2 marzo 2023): 89–93. http://dx.doi.org/10.35596/1729-7648-2023-21-1-89-93.
Testo completoAbstract (sommario):
The features of the bismuth oxide deposition by the ion layering method on matrices of anodic alumina and anodic titania have been studied. The formed nanostructured systems have been studied by means of electron micros copy, X-ray microanalysis, and X-ray spectroscopy. Two-layer nanocomposites consist of porous matrix or TiO2 island film with vertically oriented Bi2O3 plates placed on the surface. The photoluminescence spectrum of Al2O3/Bi2O3 oxide structure contains two photoluminescence channels with peaks at 460 and 560 nm upon excitation at 345 nm. Analysis of the EDX spectra showed that the atomic ratio of Bi, Ti and O was 31.46 % Bi : 3.78 % Ti : 51.05 % O. The possibility of using complex nanocomposite as contrast agents in X-ray diagnostics and for protection against ionizing radiation is shown.
15
Pallapatisaidulu e Rajeev Kumar. "Radiation Absorption on Non- Newtonian Fluid over A Vertical Plate with Radiation Heat Flux". Journal of Biomedical and Pharmaceutical Research 12, n. 4 (6 settembre 2023): 36–41. http://dx.doi.org/10.32553/jbpr.v12i4.1017.
Testo completoAbstract (sommario):
The study of radiation absorption in non-Newtonian fluids flowing over a vertical plate subjected to radiation heat flux is a complex yet critical area of research that finds wide applications in engineering, physics, and environmental sciences. In this investigation, we explore the intricate interplay between radiation heat transfer, the unique rheological properties of non-Newtonian fluids, and the resulting fluid dynamics and heat transfer phenomena. Non-Newtonian fluids, characterized by their nonlinear relationship between shear stress and shear rate, exhibit behavior that deviates from traditional Newtonian fluids. This departure introduces complexity into the heat transfer process when subjected to radiation heat flux. The vertical plate, a common boundary encountered in practical engineering scenarios, serves as a platform for examining these interactions. Research in this field employs a multidisciplinary approach, encompassing experimental investigations, mathematical modeling, and computational simulations. These methodologies are instrumental in unraveling the complexities of radiation absorption in non-Newtonian fluids over vertical plates and provide a foundation for advancements in various engineering and scientific domains.
Keywords: Radiation, Absorption, Transfer, Modeling, non-Newtonian
16
Khan, Umar, Adnan Abbasi, Naveed Ahmed e Syed Tauseef Mohyud-Din. "Particle shape, thermal radiations, viscous dissipation and joule heating effects on flow of magneto-nanofluid in a rotating system". Engineering Computations 34, n. 8 (6 novembre 2017): 2479–98. http://dx.doi.org/10.1108/ec-04-2017-0149.
Testo completoAbstract (sommario):
Purpose The purpose of this paper is to explore the impact of thermal radiation, viscous dissipation and Joule heating effects on the flow of a magneto-nanofluid between two horizontally placed plates. Three distinct shapes of nanoparticles in a base fluid (water) are considered to compose the nanofluid. Design/methodology/approach Introducing feasible similarity variables, the flow model is transformed into a nonlinear and coupled system of ordinary differential equations. The consequent system is solved by using homotopy analysis method. Findings Furthermore, the influence of embedded parameters on velocity and temperature profiles is highlighted graphically. The same is done for showing the variations in skin friction coefficient and local rate of heat transfer. Under certain conditions, present results compared with already existing results in the literature. Some main findings are pinpointed in the last section before the bibliography. From presented work, it is analyzed that the velocity field along y-axis and x-axis are increasing and decreasing functions of suction/injection parameter. The velocity of the fluid starts increases for Reynolds number and declines for volumetric fraction of the nanoparticles. Significant variations in angular velocity are observed for volumetric fraction and Reynolds number, respectively. Thermal field increases rapidly for brick-shaped nanoparticles, and for platelet-shaped nanoparticles, it decreases rapidly. Local rate of heat transfer increases for radiation and Reynolds number and starts decreasing for Eckert number. Originality/value The study presented is original and has not been submitted to any other journal for the publication purpose. The contents are original and proper references have been provided wherever applicable.
17
Trebukhov, Sergey, Valeriy Volodin, Alina Nitsenko, Xeniya Linnik, Erkebulan Kilibayev, Olga Kolesnikova e Yury Liseitsev. "Dearsenation of Gold-Bearing Composite Concentrates without Forced Displacement in a Sublimator". Journal of Composites Science 7, n. 9 (11 settembre 2023): 378. http://dx.doi.org/10.3390/jcs7090378.
Testo completoAbstract (sommario):
The primary devices for extracting volatile components from dispersed materials in a vacuum are devices with the movement of raw materials by directed vibrations. During the analysis of the operation of such installations, some shortcomings were identified, due to the supply of heat flow to the processed raw material and the requirements for the choice of structural materials. In this article, the authors tested a heating method and a design of a sublimator with the supply of heat flow to the dispersed material by radiation from the heater. The sublimation zone is made in the form of a shaft formed by simple-shaped plates, the design and material of which involve the use of refractory and ceramic materials that are inert with respect to an aggressive vaporous sulfide medium. The movement of bulk material through the volume of the sublimator occurs due to rheological properties: sliding along inclined plates. Technological tests on the sublimation of arsenic sulfides from gravity and flotation composite concentrates of the Bakyrchik deposit (Kazakhstan) have shown the possibility of a high degree of sublimation of arsenic (more than 96–99%) while preserving precious metal composites in the sublimation residue and stable operation of equipment. Sublimation residues containing 0.14–0.30% As can be processed by known methods. The possibility of sufficiently complete removal of arsenic and its compounds from composite concentrates at a reduced pressure with the removal of the latter in the most environmentally friendly sulfide form has been established.
18
Varun, Kumar, G. Manikandan, Kanna Rajesh e Venkata Poluru. "Experimental analysis of solar air heater using polygonal ribs in absorber plate integrated with phase change material". Thermal Science, n. 00 (2021): 345. http://dx.doi.org/10.2298/tsci210518345v.
Testo completoAbstract (sommario):
Heat transfer enhancement in Solar Air Heater (SAH) has been investigated by implementing rough surfaces in the absorber plate. We use paraffin wax is used as Phase Change Material (PCM) integrated with SAH as a Thermal Energy Storage (TES) system. A maximum convective heat transfer is attained during the daytime and retained as latent heat (LH) to discharge heat during OFF radiation. In this investigation, two types of absorber plates were employed such as flat & polygonal-shaped ribs at the test section. Further to investigate the heat transfer enhancement, the research was conducted with and without PCM. The study was carried out at the mass flow rates of 0.062 kg/s, 0.028 kg/s, and 0.01 kg/s to ascertain the enhancement of thermal efficiency and heat discharge duration. The temperatures of absorber plate Tp, ambient Tamb, outlet Tout and PCM along with Solar Intensity I (W/m-2) were taken as the main parameters. The research reveals that the absorber plate with polygonal ribs tested with PCM yields a higher temperature of 77?C with a mass flow rate of 0.062 kg/s during peak radiation. And discharged heat energy from PCM to absorber plate for 3.5 hours with a maximum temperature of 7.1?C.
19
Seiboth, Frank, Dennis Brückner, Maik Kahnt, Mikhail Lyubomirskiy, Felix Wittwer, Dmitry Dzhigaev, Tobias Ullsperger et al. "Hard X-ray wavefront correction via refractive phase plates made by additive and subtractive fabrication techniques". Journal of Synchrotron Radiation 27, n. 5 (30 luglio 2020): 1121–30. http://dx.doi.org/10.1107/s1600577520007900.
Testo completoAbstract (sommario):
Modern subtractive and additive manufacturing techniques present new avenues for X-ray optics with complex shapes and patterns. Refractive phase plates acting as glasses for X-ray optics have been fabricated, and spherical aberration in refractive X-ray lenses made from beryllium has been successfully corrected. A diamond phase plate made by femtosecond laser ablation was found to improve the Strehl ratio of a lens stack with a numerical aperture (NA) of 0.88 × 10−3 at 8.2 keV from 0.1 to 0.7. A polymer phase plate made by additive printing achieved an increase in the Strehl ratio of a lens stack at 35 keV with NA of 0.18 × 10−3 from 0.15 to 0.89, demonstrating diffraction-limited nanofocusing at high X-ray energies.
20
Majure, Lucas C., Yuley Encarnación, Teodoro Clase, Brígido Peguero, Kelly Ho e Duniel Barrios. "Phylogenetics of Leptocereus (Cactaceae) on Hispaniola: clarifying species limits in the L. weingartianus complex and a new species from the Sierra de Bahoruco". PhytoKeys 172 (29 gennaio 2021): 17–37. http://dx.doi.org/10.3897/phytokeys.172.59497.
Testo completoAbstract (sommario):
The Antillean genus Leptocereus represents an in-situ radiation among the Greater and Lesser Antilles of 19 currently recognized species. Extensive fieldwork carried out in the Dominican Republic over recent years has revealed that the species limits of Leptocereus of Hispaniola are more complex than previously thought. There are four currently recognized species that occur on the island, L. demissus, L. paniculatus, L. undulosus and L. weingartianus. We evaluate species limits in this group based on DNA sequence data and phylogenetic analysis, morphological characters and a survey of herbarium specimens from across Hispaniola. Based on our analyses, it is clear that at least five species occur on the island of Hispaniola, with the new species from Sierra de Bahoruco, L. velozianus, described here. We provide an identification key, distribution maps and photographic plates for all species on Hispaniola based on our own fieldwork and the study of herbarium specimens. The description of yet another species of Leptocereus on Hispaniola reiterates the importance of the poorly studied, but yet biodiverse, seasonally dry tropical forest in the Antilles.
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Wang, Jun, Jason Hilton, Hermann W. Pfefferkorn, Shijun Wang, Yi Zhang, Jiri Bek, Josef Pšenička, Leyla J. Seyfullah e David Dilcher. "Ancient noeggerathialean reveals the seed plant sister group diversified alongside the primary seed plant radiation". Proceedings of the National Academy of Sciences 118, n. 11 (8 marzo 2021): e2013442118. http://dx.doi.org/10.1073/pnas.2013442118.
Testo completoAbstract (sommario):
Noeggerathiales are enigmatic plants that existed during Carboniferous and Permian times, ∼323 to 252 Mya. Although their morphology, diversity, and distribution are well known, their systematic affinity remained enigmatic because their anatomy was unknown. Here, we report from a 298-My-old volcanic ash deposit, an in situ, complete, anatomically preserved noeggerathialean. The plant resolves the group’s affinity and places it in a key evolutionary position within the seed plant sister group. Paratingia wuhaia sp. nov. is a small tree producing gymnospermous wood with a crown of pinnate, compound megaphyllous leaves and fertile shoots each with Ω-shaped vascular bundles. The heterosporous (containing both microspores and megaspores), bisporangiate fertile shoots appear cylindrical and cone-like, but their bilateral vasculature demonstrates that they are complex, three-dimensional sporophylls, representing leaf homologs that are unique to Noeggerathiales. The combination of heterospory and gymnospermous wood confirms that Paratingia, and thus the Noeggerathiales, are progymnosperms. Progymnosperms constitute the seed plant stem group, and Paratingia extends their range 60 My, to the end of the Permian. Cladistic analysis resolves the position of the Noeggerathiales as the most derived members of a heterosporous progymnosperm clade that are the seed plant sister group, altering our understanding of the relationships within the seed plant stem lineage and the transition from pteridophytic spore-based reproduction to the seed. Permian Noeggerathiales show that the heterosporous progymnosperm sister group to seed plants diversified alongside the primary radiation of seed plants for ∼110 My, independently evolving sophisticated cone-like fertile organs from modified leaves.
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Azhagar, Arunagiri, Kunio Hayakawa, Hiroo Shizuka e Katsuhiko Sakai. "Influence of Tool pin Profiles in Friction Stir Welding of Aluminum Alloy and Polycarbonate". Defect and Diffusion Forum 414 (24 febbraio 2022): 185–90. http://dx.doi.org/10.4028/p-ohtn3n.
Testo completoAbstract (sommario):
In this study, the impact of tool pin profile on the dissimilar joining characteristics of aluminum alloy AA2017 and polycarbonate in friction stir welding (FSW) was examined. The tool pins made of SKD11 tool steel were used in the experiments of the FSW to join AA2017 and polycarbonate plates in a butt configuration at a tool rotation speed of 1320 and 1760 rpm and tool transverse speed of 60 mm/min. The tool shoulder diameter and tool pin height were set to 10 mm and 2 mm. The shapes of tool pin were cylindrical with and without groove, tapered cylindrical with and without groove, bobbin shaped with and without groove, square, triangular, pentagonal, hexagonal, oval, and ellipsoidal. The measurement of axial force was performed using a dynamometer. The changes in workpiece temperature at six locations during the process were measured using K-type thermocouples embedded in the plates. Microstructures of welded joints were examined by an optical microscope. Vickers Microhardness mapping was performed in and around the weld nugget zone, which is formed by the material flow between the two different base materials. From the result, the grooved tool pins generated less heat; while cylindrical, square, and oval type pins are also result in the superior properties of the welds during joining processes. Each tool pin had unique material flow behavior and weld formation, and the weld defects such as tunnel/voids occurred at the joint interface. The oval tool pin gives rise to the highest joint efficiency at a higher tool rotation speed, and the ellipsoidal tool pin generates the highest joint efficiency at a lower tool rotation speed was noticed.
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Sutton, S. R., P. E. Eng, M. L. Rivers e M. Newville. "Spatially-Resolved X-Ray Absorption fine Structure (XAFS) Spectroscopy Using Undulator Radiation Focused by Dynamically-Bent Elliptical Mirrors". Microscopy and Microanalysis 4, S2 (luglio 1998): 364–65. http://dx.doi.org/10.1017/s1431927600021942.
Testo completoAbstract (sommario):
X-ray absorption spectroscopy (XANES and EXAFS) applied with x-ray microprobe instrumentation (figures 1) can be used for studying the electronic structure of specific elements in complex materials in a spatially-resolved manner (figure 2). Such techniques are valuable in a wide range of studies including hydrothermal fluid processes, migration and encapsulation of toxic and radioactive wastes, and redox evolution of solar system bodies.One of the major technical challenges in this work is the production of high flux microbeams from high power, hard x-ray synchrotron sources. Some of the microbeam technologies under development include tapered glass capillaries, zone plates, and elliptical mirrors. Each approach has advantages and disadvantages and the optimum microfocusing device depends on the particular experiment.One of the most versatile of these devices is the dynamically bent, elliptical mirror, especially when a pair of mirrors are arranged in a Kirkpatrick-Baez (KB) geometry to provide two-dimensional focusing. This versatility derives mainly from four attributes.
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Minina, V. I., Yu A. Nelyubova, Ya A. Savchenko, A. A. Timofeeva, Ye A. Astafieva, M. L. Bakanova, A. V. Meier e A. N. Glushkov. "Estimation of chromosome disorders in workers at coal thermal power plant". Russian Journal of Occupational Health and Industrial Ecology, n. 3 (31 marzo 2019): 149–54. http://dx.doi.org/10.31089/1026-9428-2019-3-149-154.
Testo completoAbstract (sommario):
Introduction. Coal heat power stations are characterized by severe hazardous eff ect of occupational environment on workers. Objective. To analyze chromosomal disorders in workers of thermal power plant working on coal from Kuznetsk coal fi eld (West Siberia). Materials and methods. Th e authors studied level and specter of chromosomal aberrations in blood lymphocytes of 185 workers of Kemerovo thermal power plant and 218 inhabitants of the same location, not working on industrial enterprises (Kemerovo, Russia). For every individual, average number of 200 metaphase plates of high quality was analyzed. Results. Findings are that the workers of thermal power plant have levels of chromosomal aberrations signifi cantly higher than those of reference group (3,01±0,13% vs. 1,45±0,08%; р<0,00001). With that, increased frequency is seen both for chromatid aberrations and for chromosomal ones — that indicates complex exposure to chemical and radiation factors. Conclusions. Th e results obtained necessitate elaboration of measures to decrease genotoxic hazards in the occupational environment.
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Sanchez-Weatherby, Juan, James Sandy, Halina Mikolajek, Carina M. C. Lobley, Marco Mazzorana, Jon Kelly, Geoff Preece, Rich Littlewood e Thomas L. M. Sørensen. "VMXi: a fully automated, fully remote, high-flux in situ macromolecular crystallography beamline". Journal of Synchrotron Radiation 26, n. 1 (1 gennaio 2019): 291–301. http://dx.doi.org/10.1107/s1600577518015114.
Testo completoAbstract (sommario):
VMXi is a new high-flux microfocus macromolecular crystallography beamline at Diamond Light Source. The beamline, dedicated to fully automated and fully remote data collection of macromolecular crystals in situ, allows rapid screening of hundreds of crystallization plates from multiple user groups. Its main purpose is to give fast feedback at the complex stages of crystallization and crystal optimization, but it also enables data collection of small and delicate samples that are particularly difficult to harvest using conventional cryo-methods, crystals grown in the lipidic cubic phase, and allows for multi-crystal data collections in drug discovery programs. The beamline is equipped with two monochromators: one with a narrow band-pass and fine energy resolution (optimal for regular oscillation experiments), and one with a wide band-pass and a high photon flux (optimal for fast screening). The beamline has a state-of-the-art detector and custom goniometry that allows fast data collection. This paper describes the beamline design, current status and future plans.
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Yu, Jack C., Steven R. Buchman, Arun K. Gosain, Robert J. Havlik, Tien-Hsiang Wang, Po-Sang Lam e Mohamad Masoumy. "Basic Biomechanics for Craniofacial Surgeons: The Responses of Alloplastic Materials and Living Tissues to Mechanical Forces". FACE 2, n. 4 (22 novembre 2021): 446–61. http://dx.doi.org/10.1177/27325016211060232.
Testo completoAbstract (sommario):
Many terms such as twist, compress, bend, and stretch, describe how materials behave when subjected to mechanical stresses. Subjective adjectives to describe the property of materials such as hard or brittle are imprecise and impedes proper understanding of important principles needed in planning and performing surgical treatments. The viability of tissue and time dependent variables effect healing and compound the issue. Some parameters are time dependent (strain rate), while others are nearly independent of time (Young’s modulus). The craniofacial skeleton and enveloping soft tissues are viscoelastic composite materials which undergo time-dependent changes upon loading. The ability to remodel and respond to environmental changes makes them “smart,” reenforcing where needed and removing where not required based on a set of predetermined upper and lower thresholds. This mini review has 7 sections on engineering principles that underpin craniofacial surgery: (1) The general concept of mechanics: load, force, stress, strain, compression, tension, shear, stress-strain curves and values derived from them such as Young’s modulus, fatigue damage, and load- shearing. (2) Material properties of bone and suture and structural engineering of the craniofacial skeleton in normal and pathological conditions. (3) Fixation using wires, screws, and plates: anatomy and function of screws and plates, locking plates, lag screws, internal and external fixators. (4) Biomechanics of distraction osteogenesis and the effects of radiation. (5) Finite element analysis and other computational biomechanical tools. (6) Virtual surgical planning, cutting guides, and intra-operative navigation. (7) Tissue engineering: design goals, criteria, and constraints. An appreciation and understanding of these biomechanical principles will help craniofacial surgeons to facilitate intrinsic optimization and better treat complex morphological problems, helping one achieve the most favorable and durable results. The biological responses to mechanical stress are extremely important as well, but due to space constraints, they will be the subject of a separate dedicated review.
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Zhang, Han-hao, Pei-zhi Wang, Shuanhai He, Yuan Li, Ke-fan Chen e Nan-nan Sun. "Research of Thermal Effect of Cable-Stayed Bridge with a Separated Side-Box Steel-Concrete Composite Girder under Solar Radiation". Advances in Civil Engineering 2021 (5 aprile 2021): 1–17. http://dx.doi.org/10.1155/2021/8812687.
Testo completoAbstract (sommario):
At present, there are few studies on the thermal effect of solar radiation on a separated double-sided box steel-concrete composite girder cable-stayed bridge. In this paper, the beam element and mixed element models are combined with the theory of transient heat transfer analysis and meteorology; this approach is adopted to carry out a thermodynamic analysis of a related bridge project. The calculation results of the thermal field and structural thermodynamic analysis of bridge sections show that, in terms of a separated double-sided box steel-concrete composite girder cable-stayed bridge, the thermal field distributions of the main girder and the pylons are extremely complex under conditions of solar radiation. Therefore, the real thermal field cannot be accurately described as a one-dimensional temperature gradient. The traditional beam element model cannot accurately simulate the temperature effect, and it will underestimate its thermal effect. The calculated temperature stress values of the mixed element model are quite different from those of the of beam element model. The mixed element model can precisely reflect the local thermal effect of each component in this system under solar radiation. Compared with the calculation results of the beam element model, the maximum temperature stress of the bridge deck in each section of the main girder is generally 20% larger; the maximum temperature stress levels of the steel-beam top and bottom plates are 14.7 MPa and 15.9 MPa larger, respectively. The maximum shear stress of the steel-concrete interface is 0.2 MPa larger. The research results of the temperature effect calculated by the mixed element have an important guiding significance for the design and maintenance of bridges.
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van Diedenhoven, B., B. Cairns, A. M. Fridlind, A. S. Ackerman e T. J. Garrett. "Remote sensing of ice crystal asymmetry parameter using multi-directional polarization measurements – Part 2: Application to the Research Scanning Polarimeter". Atmospheric Chemistry and Physics Discussions 12, n. 12 (14 dicembre 2012): 32063–107. http://dx.doi.org/10.5194/acpd-12-32063-2012.
Testo completoAbstract (sommario):
Abstract. A new method to retrieve ice cloud asymmetry parameters from multi-directional polarized reflectance measurements is applied to measurements of the airborne Research Scanning Polarimeter (RSP) obtained during the CRYSTAL-FACE campaign in 2002. The method assumes individual hexagonal ice columns and plates serve as proxies for more complex shapes and aggregates. The closest fit is searched in a look-up table of simulated polarized reflectances computed for cloud layers that contain individual, randomly oriented hexagonal columns and plates with a virtually continuous selection of aspect ratios and distortion. The asymmetry parameter, aspect ratio and distortion of the hexagonal particle that leads to the best fit with the measurements are considered the retrieved values. Two cases of thick convective clouds and two cases of thinner anvil cloud layers are analyzed. Median asymmetry parameters retrieved by the RSP range from 0.76 to 0.78, and are generally smaller that those currently assumed in most climate models and satellite retrievals. In all cases the measurements indicate roughened ice crystals, which is consistent with previous findings. Retrieved aspect ratios in three of the cases range from 0.9 to 1.6, indicating compact particles dominate the cloud-top shortwave radiation. Retrievals for the remaining case indicate plate-like ice crystals with aspect ratios around 0.3. The RSP retrievals are qualitatively consistent with the CPI images obtained in the same cloud layers. Retrieved asymmetry parameters are compared to those determined in situ by the Cloud Integrating Nephelometer (CIN). For two cases, the median values of asymmetry parameter retrieved by CIN and RSP agree within 0.01, while for the two other cases RSP asymmetry parameters are about 0.03–0.05 greater than those obtained by the CIN. Part of this bias might be explained by vertical variation of the asymmetry parameter.
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van Diedenhoven, B., B. Cairns, A. M. Fridlind, A. S. Ackerman e T. J. Garrett. "Remote sensing of ice crystal asymmetry parameter using multi-directional polarization measurements – Part 2: Application to the Research Scanning Polarimeter". Atmospheric Chemistry and Physics 13, n. 6 (18 marzo 2013): 3185–203. http://dx.doi.org/10.5194/acp-13-3185-2013.
Testo completoAbstract (sommario):
Abstract. A new method to retrieve ice cloud asymmetry parameters from multi-directional polarized reflectance measurements is applied to measurements of the airborne Research Scanning Polarimeter (RSP) obtained during the CRYSTAL-FACE campaign in 2002. The method assumes individual hexagonal ice columns and plates serve as proxies for more complex shapes and aggregates. The closest fit is searched in a look-up table of simulated polarized reflectances computed for cloud layers that contain individual, randomly oriented hexagonal columns and plates with a virtually continuous selection of aspect ratios and distortion. The asymmetry parameter, aspect ratio and distortion of the hexagonal particle that leads to the best fit with the measurements are considered the retrieved values. Two cases of thick convective clouds and two cases of thinner anvil cloud layers are analyzed. Median asymmetry parameters retrieved by the RSP range from 0.76 to 0.78, and are generally smaller than those currently assumed in most climate models and satellite retrievals. In all cases the measurements indicate roughened or distorted ice crystals, which is consistent with previous findings. Retrieved aspect ratios in three of the cases range from 0.9 to 1.6, indicating compact particles dominate the cloud-top shortwave radiation. Retrievals for the remaining case indicate plate-like ice crystals with aspect ratios around 0.3. The RSP retrievals are qualitatively consistent with the CPI images obtained in the same cloud layers. Retrieved asymmetry parameters are compared to those determined in situ by the Cloud Integrating Nephelometer (CIN). For two cases, the median values of asymmetry parameter retrieved by CIN and RSP agree within 0.01, while for the two other cases RSP asymmetry parameters are about 0.03–0.05 greater than those obtained by the CIN. Part of this bias might be explained by vertical variation of the asymmetry parameter or ice shattering on the CIN probe, or both.
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Döring, Florian, Marcel Risch, Benedikt Rösner, Martin Beye, Philipp Busse, Katharina Kubiček, Leif Glaser et al. "A zone-plate-based two-color spectrometer for indirect X-ray absorption spectroscopy". Journal of Synchrotron Radiation 26, n. 4 (24 maggio 2019): 1266–71. http://dx.doi.org/10.1107/s1600577519003898.
Testo completoAbstract (sommario):
X-ray absorption spectroscopy (XAS) is a powerful element-specific technique that allows the study of structural and chemical properties of matter. Often an indirect method is used to access the X-ray absorption (XA). This work demonstrates a new XAS implementation that is based on off-axis transmission Fresnel zone plates to obtain the XA spectrum of La0.6Sr0.4MnO3 by analysis of three emission lines simultaneously at the detector, namely the O 2p–1s, Mn 3s–2p and Mn 3d–2p transitions. This scheme allows the simultaneous measurement of an integrated total fluorescence yield and the partial fluorescence yields (PFY) of the Mn 3s–2p and Mn 3d–2p transitions when scanning the Mn L-edge. In addition to this, the reduction in O fluorescence provides another measure for absorption often referred to as the inverse partial fluorescence yield (IPFY). Among these different methods to measure XA, the Mn 3s PFY and IPFY deviate the least from the true XA spectra due to the negligible influence of selection rules on the decay channel. Other advantages of this new scheme are the potential to strongly increase the efficiency and throughput compared with similar measurements using conventional gratings and to increase the signal-to-noise of the XA spectra as compared with a photodiode. The ability to record undistorted bulk XA spectra at high flux is crucial for future in situ spectroscopy experiments on complex materials.
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Bassim, M. Nabil, S. Boakye-Yiadom e Manon Bolduc. "Microstructural Evolution from Shaped Charge through Steel Plates". Applied Mechanics and Materials 566 (giugno 2014): 344–49. http://dx.doi.org/10.4028/www.scientific.net/amm.566.344.
Testo completoAbstract (sommario):
A set of 18 armour steel plates were stacked on top of each other and subjected to shape charges that went through the plates and created a hole that decreased in diameter as it went through consecutive plates. Afterwards, the plates were examined and the hardness near the hole and away from the hole was taken to determine the effect of the passing of the shaped charge through the plates. Also, specimens from the walls of the holes were taken to determine changes in the microstructure due to the shock wave and the resulting excessive heating from the shape charge. It was observed that the shock wave produced significant changes in the microstructure resulting in the appearance adiabatic shear bands (ASBs). These ASBs persisted in holes in plates placed further down the stack (up to 8thin the stack). More complex microstructural mechanisms are thought to take place as opposed to erosion from the flow of the molten metal through the holes in the plates.
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Taratorin, Andrey, e Ainur Mukhametov. "OPTIMIZATION OF COMPLEXLY SHAPED DISSIPATIVE SILENCERS". VOLUME 39, VOLUME 39 (2021): 94. http://dx.doi.org/10.36336/akustika20213994.
Testo completoAbstract (sommario):
The article is about a comprehensive study of dissipative silencers of complex shapes. Analyzed the acoustic efficiency of such silencers. The sound absorption coefficient determined from experimental data. The acoustic properties of plate silencers take into account that coefficient. Presented the results of verification of models with plates of constant thickness. Considered the plates of complex shapes: uniform thickness change, convex and concave. Obtained results of modeling the acoustic efficiency of silencers with complex shape plates. These results are for different values of the mean integral thickness for the octave bands frequencies. Determined the dependence of the length of complex shapes silencers on their mean integral thickness. Presented the results of mathematical modeling of the airflow in silencers to determine their aerodynamic drag. The calculations showed that there is an optimal shape and mean integral thickness of the plates. Under which conditions the aerodynamic resistance of the silencer is minimal.
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Onanko, Yurii Anatoliyovich, Dmytro Volodymyrovych Charnyi, Anatoliy Petrovich Onanko, Eugene Michaylovich Matseliuk, Oksana Petrivna Dmytrenko, Mukola Polikarpovich Kulish, Tatiana Mukolaivna Pinchuk-Rugal, Petro Petrovich Ilyin e Anna Andriivna Kuzmych. "(Digital Presentation) Internal Friction, Mechanical Spectroscopy in SiO2/Si Wafers". ECS Meeting Abstracts MA2023-01, n. 29 (28 agosto 2023): 1796. http://dx.doi.org/10.1149/ma2023-01291796mtgabs.
Testo completoAbstract (sommario):
Introduction The electrophysical properties of semiconductor devices significantly depend on the perfection of their structure. It is necessary to control the structure of semiconductor wafer-plates disks in the manufacture of large integrated circuits (LIC). Technique was developed and device was made that allows to obtain the information about structural defects in such disks by attenuating elastic oscillations Q-1 to study the defects density nd and the depth hd of their propagation. Defect annealing leads to change in the shape of internal friction (IF) temperature spectrum Q-1(T) [1]. IF method allows to set the spectrum of structural defects on the analysis of positions of maximums IF, on duration of relaxation time τ and on their deposit in attenuation of elastic vibrations [2]. A non-destructive method for the technological control of the structure defects by measuring internal friction (IF) and elastic modulus E after laser radiation was developed. Experimental procedure Ultrasonic (US) pulse-phase method using USMV-LETI, modernized USMV-KNU and computerized “KERN-4” with frequencies f║ ≈ 1 MHz and f┴ ≈ 0,7 MHz, US invariant-polarization method for determining the effective acoustic μil and elastic constants Cijkl were used [3,4,5]. The measured velocity error was equal to ΔV/V = 0.5÷1,5%. The study of influence of structure defects on damping of vibrations in Si/SiO2 wafer-plates by the diameter of D = 100÷60 mm and by the thickness of hSiO2 ≈ 600 nm, hSi ≈ 470 000 nm, allows to estimate the degree of perfection of crystalline structure. Metallography optical supervision of microstructure by means of the microscope ”LOMO MVT”, atomic-force microscopy (AFM) were used. Results and discussion The quasi-longitudinal US velocity V║[001] = 5870 m/s, elastic modulus E001 = ρV║[001] 2 = 80,28 GPa for SiO2/Si from the oscillogram were determined. Temperature dependence of internal friction Q-1(T) in SiO2/Si wafer-plate p-type, doped with B, KDB-7.5(100) diameter D ≈ 76∙10-3 m, thickness hSi ≈ 460∙103 nm with SiO2 layer thickness hSiO2 ≈ 100 nm after X-ray irradiation with dose Dγ ≈ 102 Gy is showed. Conclusions It was found that as the result of the structural defect annealing IF background Q0 -1 significantly decreases during measuring of IF temperature dependence Q-1(T), which indicates the improvement of SiO2/Si crystal structure. The elastic modulus Е, the shear modulus G, Poisson coefficient μ, IF Q-1 are dependent from SiO2/Si wafer-plate anisotropy. The value of IF background Q-1 0 after temperature T, mechanical treatments describes the changes of the elastic stress σi fields in SiO2/Si wafer-plate. The study of vibrations of disk wafer-plate Si/SiO2 at different harmonic frequencies f0, f2 made it possible to develop the technique for determining the structural defects density nD for semiconductor wafers-substrates. The relationship between IF Q-1 value, the logarithmic decrement of ultrasound damping δ and the dislocations density nD was established for disk-shaped semiconductor wafers-substrates. Acknowledgements This work has been supported by Ministry of Education and Science of Ukraine: Grant of the Ministry of Education and Science of Ukraine for perspective development of a scientific direction "Mathematical sciences and natural sciences" at Taras Shevchenko National University of Kyiv. References [1] Golovin I. S. 2012 Internal friction and mechanical spectroscopy of metal materials (Moscow: Publishing company MISIS). [2] Shpak A. P., Kunickiy Y. A. and Karbovskiy V. L. 2001 Cluster and nano structural materials (Kyiv: Academy periodicals). [3] Korobiichuk, I., Kuzmych, L., Kvasnikov, V. 2020 The system of the assessment of a residual resource of complex technical structures. MECHATRONICS 2019. Advances in Intelligent Systems and Computing. 1044, 350–357. DOI: https://doi.org/10.1007/978-3-030-29993-4_43 [4] Onanko A. P., Kuryliuk V. V., Onanko Y. A. et al. 2020 Peculiarity of elastic and inelastic properties of radiation cross-linked hydrogels. J. Nano- Electron. Phys. 12, № 4, 04026(5). DOI: https://doi.org/10.21272/jnep.12(4).04026 [5] Onanko A. P., Kuryliuk V. V., Onanko Y. A. et al. 2021 Features of inelastic and elastic characteristics of Si and SiO2/Si structures. J. Nano- Electron. Phys. 13, № 5, 05017(5). DOI: https://doi.org/10.21272/jnep.13(5).05017 Figure 1
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Paterson, N., A. Tawn, K. Williams e A. D. Nurse. "On the numerical modelling of laser shearing of glass sheets used to optimize production methods". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 218, n. 1 (1 gennaio 2004): 1–11. http://dx.doi.org/10.1243/095440604322786901.
Testo completoAbstract (sommario):
The problem of the control of the propagating crack tip during laser shearing (or zero width laser cutting of glass) is essentially one of controlling the stress field within the substrate. The glass substrate is stressed thermally using surface absorption of 10.6 μm laser radiation followed by cooling, in this case from a fine atomized waterjet. The stresses created in a large sheet, combined with the residual stresses within the glass substrate, are sufficient to propagate a subsurface flaw to form a controlled crack that gives excellent cut quality. This process has previously been studied experimentally and is successful for large plates and shapes with large radii of curvature. In order for future work to extend the process to minimize damage at the end of a cut, at the close of a profiled cut or close to the edge of the plate, it is necessary to understand the stresses that control the crack propagation and control these as the stress field changes. This work outlines an initial theoretical study of the heating and cooling cycle coupled with finite element analysis of the induced stresses to increase the understanding of laser shearing of glass. It provides a thorough description of how to perform the complex numerical studies, including how to determine the quasi-static crack tip position. The results provide levels of stresses in the immediate vicinity of the crack tip and show that thermal heating/cooling loading conditions are favourable for straight line cutting.
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Iqbal, Amjad, Amor Smida, Nazih Mallat, Mohammad Islam e Sunghwan Kim. "A Compact UWB Antenna with Independently Controllable Notch Bands". Sensors 19, n. 6 (22 marzo 2019): 1411. http://dx.doi.org/10.3390/s19061411.
Testo completoAbstract (sommario):
A minimally-sized, triple-notched band ultra-wideband (UWB) antenna, useful for many applications, is designed, analyzed, and experimentally validated in this paper. A modified maple leaf-shaped main radiating element with partial ground is used in the proposed design. An E-shaped resonator, meandered slot, and U-shaped slot are implemented in the proposed design to block the co-existing bands. The E-shaped resonator stops frequencies ranging from 1.8–2.3 GHz (Advanced Wireless System (AWS1–AWS2) band), while the meandered slot blocks frequencies from 3.2–3.8 GHz (WiMAX band). The co-existing band ranging from 5.6–6.1 GHz (IEEE 802.11/HIPERLANband) is blocked by utilizing the U-shaped section in the feeding network. The notched bands can be independently controlled over a wide range of frequencies using specific parameters. The proposed antenna is suitable for many applications because of its flat gain, good radiation characteristics at both principal planes, uniform group delay, and non-varying transfer function ( S 21 ) for the entire UWB frequency range.
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Pauly, Hans. "Columnar and radiating aggregates with jarlite from the Ivigtut cryolite deposit, South Greenland". Bulletin of the Geological Society of Denmark 40 (30 dicembre 1993): 272–79. http://dx.doi.org/10.37570/bgsd-1993-40-12.
Testo completoAbstract (sommario):
Most jarlite in the Ivigtut cryolite deposit occurred as cm-sized segregations in fluorite-carrying masses. The conspicuous columnar and radiating aggregates with jarlite occurred only in five places in the quarry. They are composed of mm-wide, dm-long lamellae either in a radiating pattern or in a more or less parallel arrangement. The major constituent of the lamellae is jarlite in fan-shaped grains 0.2-1 mm long. They are delineated by seams, a few tenths of a mm wide, of cryptocrystalline topaz and a spherulitic mica which show straight borders towards the jarlite. The lamellae are prismatic bodies with lozenge shaped cross sections showing angles of 70° and 110°, the latter often truncated giving 145°. The faces of the prisms correspond to topaz-coated planes found in the pseudocubic mineral cryolite: · pseudo-octahedral and pseudo-dodecahedral. planes. The lamellae are regarded as pseudomorphs after prismatic cleavage bodies of cryolite. The radiating and columnar aggregates formed when Sr-Ba-rich fluids dissolved shattered, topaz-coated cryolite. Simultaneously with the dissolution b0gvadite and strontian barite formed crystals with axes parallel to the crystallographic axes of the former cryolite. The fanshaped/subspherulitic jarlite grains with random orientations formed later, presumably from gel-like masses produced by the total dissolution of the cryolite. The central parts of the radiating aggregates had b0gvadite crystals in an array lined up after the radial directions, in a matrix of micron-sized scales of strontian barite with a kaolin-like mineral. Tangential bands of the spherulitic mica make the central parts, 5-10 cm across, appear as colloform masses formed from a gel.
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Sigal, S. H., S. Brill, A. S. Fiorino e L. M. Reid. "The liver as a stem cell and lineage system". American Journal of Physiology-Gastrointestinal and Liver Physiology 263, n. 2 (1 agosto 1992): G139—G148. http://dx.doi.org/10.1152/ajpgi.1992.263.2.g139.
Testo completoAbstract (sommario):
We propose that the liver is a stem cell and lineage system with many parallels to lineages in the bone marrow, gut, and epidermis, varying from them only in kinetics. All are organized with three compartments: a slow cycling stem cell compartment with cells expressing a fetal phenotype and responding slowly to injury; an amplification compartment with cells of intermediate phenotype rapidly proliferating in response to regenerative stimuli or acute injuries; and a terminal differentiation compartment in which cells increasingly differentiate and gradually lose their ability to divide. In all systems, both those with slow or rapid kinetics, the various compartments are positioned in a polarized organization, are associated with a gradient in the chemistry of the extracellular matrix, and show lineage-position-dependent growth responses, gene expression, pharmacological and toxicological responses, and reaction to viruses and radiation. In general, known oncogens selectively kill cells in the differentiation compartment inducing chronic regenerative responses of the cells in stem cell and/or amplification compartment. Tumors arise by subsequent transformation of the activated stem cells or early precursor cells. The evidence for a lineage model consists of the data implicating gradients in cell size, ploidy, growth potential, and antigenic and gene expression in the liver parenchyma along the sinusoidal plates. The traditional explanation for this heterogeneity is that it represents adaption of cells to a changing sinusoidal microenvironment dictated by the direction of blood flow. However, we review the extant data and suggest that it more readily supports a lineage model involving a maturation process beginning with stem cells and precursors in the periportal zone and ending with sensescing parenchyma near the central vein. Support for this theory is provided by the studies on phenotypic heterogeneity in liver, investigations into the embryology of the liver, and analyses of the responses of liver to chemical and viral oncogens that induce rapid proliferation of small cells with oval-shaped nuclei, "oval cells," now thought to be closely related to liver stem cells. The lineage model provides clarity and insights into many aspects of liver biology and disease including the limited proliferative ability of in vitro parenchymal cultures, liver regeneration, gene expression, viral infection, hepatocellular carcinogenesis, liver cell transplantation, and aging.
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Klochko, L. S. "THE HEADDRESS FROM THE BERDYANSK KURGAN". Archaeology and Early History of Ukraine 36, n. 3 (21 maggio 2020): 383–94. http://dx.doi.org/10.37445/adiu.2020.03.26.
Testo completoAbstract (sommario):
The Berdyansk kurgan has been studied for a long time, however some problems remain unsolved. One of them is the reconstruction of costume components by decorative elements, found in central burial (N 2). It was raided, however one area remained intact. Below the collapsed ceiling is the «item storage»: there were items of which only jewelry remained — the large amount of golden applique plates (2991 items total). The most peculiar are the artifacts which were probably the adornments for the headwear. In order to recreate their form, the complex and comparative analyses of golden plates’ collections were performed. The probably adorned cone-shaped hats and the veil. The one collection of adornments included appliques which were on the frontal part of the headwear. Below were the triangular plates, the main part was occupied by ornamented appliques: «portraits» full face (female image) and profile (grotesque male image), felidae predator. The adornments of the cone-shaped hat are connected to the other headwear — the veil. It was ornamented on its edges — on the left and on the right — with rectangular plates which contained so-called «brotherhood scene». The connection of the said images on the headwears is the marker of sacramental act — wedding rituals.
The artifacts, which probably were ornaments of headwear, draw most attention. The complex and comparative analysis of golden jewelry was used in order to recreate their form. It is possible that they were attached to different types of attires. One attire consisted of cone-shaped hat and the veil. They are decorated with anthropomorphous images and geometrical ornaments (triangles). Another attire is also the cone-shaped hat, which form is supported by horizontal lines of plates with the images of predators and triangles. Generally speaking, these are the symbols of fertility cult. One of the tasks of the research is the determination of attire’s semantics. The grave contains the burial of a high-rank man, but the reconstructed attires are female. Cone-shaped attires are linked to wedding ceremonies in many peoples. The burial and wedding rituals have similar semantics, since both are about passing from one world to another. Sacred attires could have been the markers of bride’s (or brides’) presence in the male burial.
Apart from the headwears there were also the necklace which resembles the net and the clothes adorned with golden appliques. The «item storage» was surrounded by the golden plates, presumably sewed on the veil, which had the images of the gryphon and felidae hunter — the ornament which divides two worlds — one of life, and the other of death.
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Katrich, V. A. "On Calculation of Radiation Field from Complex-Shaped Slot in Rectangular Waveguide". Telecommunications and Radio Engineering 53, n. 4-5 (1999): 83–87. http://dx.doi.org/10.1615/telecomradeng.v53.i4-5.150.
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Serebrennikova, N. Yu, Yu N. Nefedova, A. A. Selivanov, A. V. Kovalenko, P. S. Ogurtsov e V. A. Soloviev. "AUTOCLAVE MOLDING OF LOWER WING PANEL SKINS FROM 1441 ALLOY PLATES". Aviation Materials and Technologies, n. 3 (2021): 35–44. http://dx.doi.org/10.18577/2713-0193-2021-0-3-35-44.
Testo completoAbstract (sommario):
The paper considers the main features of the process of autoclave molding of complex geometric shape parts from plates of medium-strength alloy 1441, combined with aging to the state of T11 heat treatment. The article provides the results of modeling of the autoclave molding process of skin fragments of the lower wing panel made of 1441 alloy, and the temperature-time parameters of this process determined during the research. The paper generalizes the results of examination of mechanical and corrosion characteristics of the fragments of the lower wing panel. The possibility of obtaining high accuracy of geometry of complex shaped elements while ensuring uniformity of characteristics in the entire area of parts is shown.
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Onanko, Yurii Anatoliyovich, Dmytro Volodymyrovych Charnyi, Anatoliy Petrovich Onanko, Eugene Michaylovich Matseliuk, Oksana Petrivna Dmytrenko, Mukola Polikarpovich Kulish, Tatiana Mukolaivna Pinchuk-Rugal, Petro Petrovich Ilyin e Anna Andriivna Kuzmych. "Internal Friction and Mechanical Spectroscopy of SiO2/Si, Nanocomposites of Multiwalled Carbon Nanotubes and Polyamide, Polyethylene, Polyvinyl Chloride, Expanded Polystyrene". ECS Meeting Abstracts MA2022-02, n. 64 (9 ottobre 2022): 2365. http://dx.doi.org/10.1149/ma2022-02642365mtgabs.
Testo completoAbstract (sommario):
Abstract: In this work after X-ray irradiation outcomes of the evaluation of dynamic characteristics interstitial atoms Sij, vacancy V and O-complexes was applied for account of a condition of an annealing with the purpose of deriving specific structural defects in SiO2/Si wafer-plate. The nondestructive method, which is allow to determine from internal friction difference ΔQ-1/Q-1 0 of elastic vibrations structure defects density Nd and the depth of broken layer hb, is offered for SiO2/Si wafer-plates. 1. Introduction Defect annealing leads to a change in the shape of the internal friction (IF) temperature spectrum Q-1(T) [1]. IF method allows to set the spectrum of structural defects on the analysis of positions of maximums IF, on duration of relaxation time τ and on their deposit in attenuation of elastic vibrations [2]. A non-destructive method for the technological control of the structure defects by measuring internal friction (IF) and elastic modulus E after laser radiation was developed. 2. Experimental procedure Ultrasonic (US) pulse-phase method using USMV-LETI, modernized USMV-KNU and computerized “KERN-4” with frequencies f║ ≈ 1 MHz and f┴ ≈ 0,7 MHz, US invariant-polarization method for determining the effective acoustic μil and elastic constants Cijkl were used [3,4]. The measured velocity error was equal to ΔV/V = 0,5÷1,5%. The study of influence of structure defects on damping of vibrations in Si/SiO2 wafer-plates by the diameter of D = 100÷60 mm and by the thickness of hSiO2 ≈ 600 nm, hSi ≈ 470 000 nm, allows to estimate the degree of perfection of crystalline structure Metallography optical supervision of microstructure by means of the microscope ”LOMO MVT”, atomic-force microscopy (AFM) were used. 3. Results and discussion The quasi-longitudinal US velocity V║[001] = 5870 m/s, elastic modulus E001 = ρV║[001] 2 = 80,28 GPa for SiO2/Si from the oscillogram were determined. Temperature dependence of internal friction Q-1(T) in SiO2/Si wafer-plate p-type, doped with B, KDB-7.5(100) diameter D ≈ 76∙10-3 m, thickness hSi ≈ 460∙103 nm with SiO2 layer thickness hSiO2 ≈ 100 nm after X-ray irradiation with dose Dγ ≈ 102 Gy is showed. 4. Conclusions 1. The growth of internal friction maximum height QM -1 testifies the growth of the structural defects concentration n, and the broadening of internal friction maximum ΔQM -1 here represents the relaxation process of structural defects new types in SiO2/Si wafer-plate. 2. It was found that as the result of the structural defect annealing IF background Q0 -1 significantly decreases during measuring of IF temperature dependence Q-1(T), which indicates the improvement of SiO2/Si crystal structure. 3. The elastic modulus Е, the shear modulus G, Poisson coefficient μ, IF Q-1 are dependent from SiO2/Si wafer-plate anisotropy. 4. The value of IF background Q-1 0 after temperature T, mechanical treatments describes the changes of the elastic stress σi fields in SiO2/Si wafer-plate. 5. The study of vibrations of disk wafer-plate Si/SiO2 at different harmonic frequencies f0, f2 made it possible to develop the technique for determining the structural defects density nD for semiconductor wafers-substrates. 6. The relationship between IF Q-1 value, the logarithmic decrement of ultrasound damping δ and the dislocations density nD was established for disk-shaped semiconductor wafers-substrates. Acknowledgements This work has been supported by Ministry of Education and Science of Ukraine: Grant of the Ministry of Education and Science of Ukraine for perspective development of a scientific direction "Mathematical sciences and natural sciences" at Taras Shevchenko National University of Kyiv. References [1] Golovin I. S. 2012 Internal friction and mechanical spectroscopy of metal materials (Moscow: Publishing company MISIS). [2] Shpak A. P., Kunickiy Y. A. and Karbovskiy V. L. 2001 Cluster and nano structural materials (Kyiv: Academy periodicals). [3] Onanko A. P., Kuryliuk V. V., Onanko Y. A. et al. 2020 Peculiarity of elastic and inelastic properties of radiation cross-linked hydrogels. J. Nano- Electron. Phys. 12, № 4, 04026(5). DOI: https://doi.org/10.21272/jnep.12(4).04026. [4] Onanko A. P., Kuryliuk V. V., Onanko Y. A. et al. 2021 Features of inelastic and elastic characteristics of Si and SiO2/Si structures. J. Nano- Electron. Phys. 13, № 5, 05017(5). DOI: https://doi.org/10.21272/jnep.13(5).05017. Figure 1
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Sotnikova, E. V., e N. Yu Kalpina. "The System for Protecting Air Environment of the Welding Work Area Using Restorative Ventilation". Occupational Safety in Industry, n. 3 (marzo 2023): 57–61. http://dx.doi.org/10.24000/0409-2961-2023-3-57-61.
Testo completoAbstract (sommario):
The technology is considered related to the protection of the air environment of electric welding areas with the use of restorative ventilation and showering. With the help of it, polluted air is removed from the working area and the conditioned air is supplied instead for meeting the requirements of sanitary norms for the microclimate parameters of working premises and the content of harmful substances in them. The traditional technology of air purification from welding smoke has fundamental disadvantages, the main of which is the inability to clean the air from carbon monoxide and nitrogen dioxide impurities. To normalize the microclimate of working areas, the volumetric air conditioning is used, which requires enormous energy costs. At the same time, the distribution of supply air does not provide for the protection of the welder from intense thermal radiation. The system of harmful substances suction from the welding station limits the freedom of the welder action. Therefore, in some cases, he is forced to raise the suction funnel above his head, as a result of what the welding smoke enters the room. It is proposed to avoid the above shortcomings by improving the system of complex protection of the air environment, containing an exhaust panel, an apparatus for cleaning and heat-moisture treatment of air with its cooling and subsequent return to the welder working area. It is advisable to use an apparatus for wet air treatment made according to the type of a packed scrubber-absorber using water with active additives of permanganate and sodium bicarbonate dissolved in it, which contribute to the dissolution and retention of toxic gases of the welding smoke in water. To increase the efficiency of air purification in this apparatus, it is proposed to use a special irrigated nozzle made of porous plastic plates, in which artificial turbulence of the air flow is carried out, which ensures its intense heat and mass transfer and temperature reduction. The use of such a device allows to implement an energy-saving technology by reducing the performance of the supply units to the minimum required level of outdoor air supply.
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Aldhaheri, Rabah, Ibrahim Alruhaili, Kamili Babu e Muntasir Sheikh. "A Compact CPW-Fed UWB Antenna with Dual-Band Notched Characteristics for WiMAX/WLAN Applications". Applied Computational Electromagnetics Society 36, n. 2 (16 marzo 2021): 145–51. http://dx.doi.org/10.47037/2020.aces.j.360205.
Testo completoAbstract (sommario):
A dual-notched bands ultra-wideband (UWB) antenna with coplanar waveguide (CPW) fed is presented in the paper. The two notched bands are selected at 3.5 and 5.8 GHz frequencies to overcome the interference from WiMAX and WLAN bands. The overall size of the antenna is 17.5×17.5 mm2, which can be considered as one of the smallest UWB antennas in the literature. The developed antenna has an impedance band width ranging from 2.9 to 13 GHz. The measured radiation patterns on E and H planes are nearly omni-directional and stable with acceptable gain over the entire band. The dual-band notched at WiMAX and WLAN is created by embedding I-shaped and C-shaped stubs in the radiation patch of the antenna. Due to the compactness, good radiation patterns and the reasonable stable gain, this antenna is well suited for integration into portable wireless communications devices for UWB applications.
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Rippaus, N., J. Manning, A. Droop, M. Al-Jabri, M. Care, A. F. Bruns, M. D. Jenkinson et al. "OS9.5 Evidence that adult glioblastoma adapts to standard therapy though chromatin remodeling". Neuro-Oncology 21, Supplement_3 (agosto 2019): iii19. http://dx.doi.org/10.1093/neuonc/noz126.063.
Testo completoAbstract (sommario):
Abstract BACKGROUND Glioblastoma (GBM) tumours recur following standard treatment in almost all cases. We use ‘omics technologies to simultaneously profile pairs of primary and matched recurrent GBM to specifically identify and characterise the cells that resisted treatment, with the aim of determining how to more effectively kill them. MATERIAL AND METHODS We have analysed high coverage RNAseq data from pairs of GBM tumours: primary de novo tumour and matched local recurrence from patients that underwent standard therapy. Our original cohort constituted 23 pairs and our validation cohort was an additional 22 pairs. We also cultured two plates of spheroids directly from a patient’s GBM, treating one with radiation and temozolomide. We monitored growth and captured and sequenced RNA from single cells at two time-points: one week post-treatment when the deviation between untreated and treated spheroid growth curves was most pronounced; and three weeks post-treatment when the growth rate of treated spheroids had recovered. We investigated differential gene expression between primary and recurrent pairs, and single cells pre- and post-treatment, and performed a bespoke per patient gene set enrichment analysis. RESULTS Differential gene expression analysis in 23 tumour pairs indicated a treatment-induced shift in cell states linked to normal neurogenesis and prompted us to develop a novel gene set enrichment analysis approach to identify gene regulatory factors that may orchestrate such a shift. This revealed the significant and universal dysregulation of genes, through therapy, that are targeted by a specific chromatin remodeling machinery. This finding was validated in an independent cohort of 22 further GBM pairs. To understand the therapeutic potential of this finding we must determine whether genes are dysregulated through therapy owing to a) their fixed expression in inherently treatment resistance cells in the primary tumour which get selected during therapy to increase the signal of that profile, or b) changes in expression during the process of cells acquiring treatment resistance. To inspect this, we analysed single cell gene expression data from GBM spheroids pre- and post-treatment. We found that there was significant dysregulation of the genes associated with the chromatin remodeling complex but only at the three-week post-treatment time-point. CONCLUSION Our results indicate that GBM cells are being transcriptionally reprogrammed in response to treatment; the mechanism of which may represent a therapeutic opportunity.
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Van Laar, Timo, Thomas Collet, Dries Peumans e Yves Rolain. "Manufacturing Millimeter-Wave Horn Antennas Using 3D Printing and Direct Electrodeposition". ECS Meeting Abstracts MA2023-01, n. 22 (28 agosto 2023): 1566. http://dx.doi.org/10.1149/ma2023-01221566mtgabs.
Testo completoAbstract (sommario):
Additive manufacturing has undergone huge development in recent years. It has become commonplace both for the hobbyist community and industry, with important applications in several domains (e.g. biomedical, aerospace and automotive). Its main strength lies in the fact that custom parts can be quickly prototyped and manufactured, regardless of their complexity. However, many of the 3D printing techniques still have limitations in terms of strength, materials, production speed and overall usability. One of the main limitations is that most techniques utilize polymers, which are intrinsically non-conductive. This limits their use in electronics and telecommunication applications. Meanwhile, a lot of equipment used in telecommunications, such as antennas, tuners, waveguides, etc. remain very expensive due to complex and time-intensive manufacturing techniques. This leads to high prices, long lead times and limitations in the complexity of the geometries. The main goal of this research is to develop a fast and cost-effective method to produce conductive structures using additive manufacturing, more specifically fused deposition modeling (FDM) 3D printing. A special focus is put on horn antennas for microwave applications, as this application is very demanding on both the accuracy of the geometry and the conductivity of the structure. The approach in this work mainly consists of two steps: optimizing the plating conditions on flat test samples and extending this knowledge to the three-dimensional horn antenna. The chosen material is a PLA-based polymer with carbon black as an additive, which provides the polymer with some electrical conductivity (factor ~107 lower than copper). This conductivity is too low for any meaningful application but allows for the use of electrodeposition of copper directly onto the polymer to increase the conductivity. By focusing on reducing the distance from the electrical contact to the surface to be plated and by tuning the deposition parameters, high-quality uniform copper deposition is obtained on test samples. The achieved results outperform the current state-of-the-art in this field. The knowledge acquired from the test samples is then applied to the horn antenna. To this end a conductive antenna holder is developed. The antenna holder serves to keep the potential as constant as possible over the entire antenna surface in order to promote homogeneous deposition. It also aligns the electrodes, keeping the distance between electrodes as constant as possible and preventing short circuits. This method results in good partial coverage and again produces better results than can be found in the literature. However, direct deposition of a nicely uniform layer over the entire surface remains very challenging. An indirect electrodeposition method using conductive silver paint is used to produce the final version of the printed horn antenna. Measurements in an anechoic chamber demonstrate that the copper-coated version of the printed antenna has similar radiation performance as a commercial counterpart. An exponential horn antenna is made with decent performance, demonstrating the ease of production of more complexly shaped antennas. Our antennas can be produced within a couple of hours at a fraction of the price of commercial counterparts ($3 instead of $500-1500). This opens up new possibilities to quickly validate simulation results of new antenna designs. Further research focuses on the use of electroless plating to obtain more homogeneous copper deposition on three-dimensional structures, as well as extending our methodologies to more complex geometries.
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Ali, Wael A. E., e Rowan A. Ibrahim. "Highly Compact 4 × 4 Flower-Shaped MIMO Antenna for Wideband Communications". Applied Sciences 13, n. 6 (10 marzo 2023): 3532. http://dx.doi.org/10.3390/app13063532.
Testo completoAbstract (sommario):
This paper introduces an MIMO antenna with a highly compact size of 30 mm width and 30 mm length. Four symmetrical MIMO antenna radiators are utilized with decoupling stubs in the top and bottom planes of the substrate to improve the isolation level. The simulated and measured outcomes are validated to investigate the impact of the suggested MIMO antenna for wideband applications. The suggested MIMO antenna has an impedance matching less than −10 dB from 5.8 GHz up to 11 GHz, and the isolation between the four radiators exceeds 20 dB over this band. Moreover, the antenna provides an envelope correlation coefficient not exceeding 0.004, a diversity gain above 9.97 dB, and a mean effective gain of ≤−3 dB over the achieved frequency range. The suggested MIMO antenna exhibits a nearly omnidirectional radiation pattern in one plane and a bi-directional radiation pattern in the other plane with an acceptable average value of the realized gain (4 dBi) over the achieved frequency band. A comparison with the state-of-the-art is tabulated to show the distinct performance of the suggested MIMO antenna for wideband applications.
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PASTOR, CATALINA, e VIRGINIA LO RUSSO. "Two new species of Enoplolaiminae (Enoplida: Thoracostomopsidae) from Río Negro and Chubut, Argentina". Zootaxa 5020, n. 2 (12 agosto 2021): 337–51. http://dx.doi.org/10.11646/zootaxa.5020.2.6.
Testo completoAbstract (sommario):
Two new species of free-living marine nematodes of the subfamily Enoplolaiminae are described from Río Negro and Chubut Provinces, Argentina. Enoplolaimus variispiculum sp. n. is characterized by having asymmetric spicules, different in size and distal tips. It is the only species with this characteristic in the whole genus. Mesacanthoides flagellatum sp. n. is characterized by mandibles texture, weakly cuticularized and mottled and mandibular plates with pronounced “v” shaped incision posterior to the anterior bar. Cephalic capsule wider than long with setae on posterior end, males with long spicules, complex gubernaculum and flagellate tail.
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Kakehi, Yasumaro, e Kojiro Irikura. "High-frequency radiation process during earthquake faulting—envelope inversion of acceleration seismograms from the 1993 Hokkaido-Nansei-Oki, Japan, earthquake". Bulletin of the Seismological Society of America 87, n. 4 (1 agosto 1997): 904–17. http://dx.doi.org/10.1785/bssa0870040904.
Testo completoAbstract (sommario):
Abstract We investigate the process of high-frequency (1 to 10 Hz) radiation on the fault plane of the 1993 Hokkaido-Nansei-Oki, Japan, earthquake (MW = 7.5) from the envelope inversion of strong-motion acceleration seismograms. For the analysis, empirical Green's functions are used because theoretical approach is not available for such high frequencies. The source is modeled with two fault planes with different strike angles. The rupture process of this earthquake is very complex in terms of high-frequency wave generation. The rupture, which started on the northern fault plane, had a delay of about 10 sec or propagated very slowly between the northern and southern fault planes. High-frequency wave radiation is large at the northern and southern edges of the source region. Deceleration of rupture is also observed there. This is interpreted to be associated with stopping of rupture. Another high-frequency wave radiation area is found at the center of the northern fault plane, where discontinuity in the depth distribution of aftershocks suggests an existence of a barrier. The areas of high- and low-frequency wave radiation are not correlated. This is considered to result from the complexity of rupture process. We cannot distinguish between westward and eastward dip of the southern fault plane because of one-sided station distribution.
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Causse, Alexandre, Kevin Rodriguez, Loïc Bernard, Ala Sharaiha e Sylvain Collardey. "Compact Bandwidth Enhanced Cavity-Backed Magneto-Electric Dipole Antenna with Outer Γ-Shaped Probe for GNSS Bands". Sensors 21, n. 11 (21 maggio 2021): 3599. http://dx.doi.org/10.3390/s21113599.
Testo completoAbstract (sommario):
In this paper, a wideband small cavity-backed magneto-electric (ME) antenna is proposed. This antenna is linearly polarized and designed to cover all the Global Navigation Satellite System (GNSS) bands. It exhibits small external dimensions of 90 × 90 × 40 mm3 (0.34 × 0.34 × 0.15 λ3 at lowest frequency) and achieves a wide impedance bandwidth of 40.5% (from 1.14 to 1.72 GHz) due to the excitation of a third resonance of the ME structure. It also provides a regular broadside gain of 5.2 dBi and stable radiation pattern in both E and H planes of the antenna.
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Asyikin Ibrahim, Noorfaten, e Bibi Intan Suraya Murat. "Modeling Analysis of Guided Ultrasonic Waves in Composite Plates with Impact Damage". International Journal of Engineering & Technology 7, n. 4.26 (30 novembre 2018): 175. http://dx.doi.org/10.14419/ijet.v7i4.26.22162.
Testo completoAbstract (sommario):
This paper investigates the propagation of guided ultrasonic waves and the interaction with impact damage in composite plates using a full three-dimensional Finite Element analysis. Impact damage in the composite plate was modeled as rectangular- and T-shaped delaminations. In order to provide guidelines for extending the modeling of realistic multimode impact damage, the impact damage was modeled as a combination of the delamination and reduced materials properties. The information obtained from these methods was compared to the experimental results around the damage area for a validation. There was a reasonable similarity between the experimental and FE results. The FE simulations can effectively model the scattering characteristics of the A0 mode wave propagation in anisotropic composite plates. This suggests that the simplified and easy-to-implement FE model could be used to represent the complex impact damage in composite plates. This could be useful for the improvement of the FE modeling and performance of guided wave methods for the in-situ NDE of large composite structures.