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Journal articles on the topic 'Disks'
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1
Kiyamov, Asror Z. "Comb-forming roller with elastic rods." E3S Web of Conferences 390 (2023): 06041. http://dx.doi.org/10.1051/e3sconf/202339006041.
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A design diagram of comb formation roller in resilient stems is given. Comb-forming roller consists of support and small discs, as well as elastic rods. Elastic rods are installed along the perimeter of the diameter of the disks through their holes. Analytical dependences and mathematical models are obtained for determining the distance between disks, the diameter of disks, the diameter, length and number of elastic rods. One-factor experiments were carried out to substantiate the diameter of the disks and the number of rods. It was found that with the length of the elastic rods of the comb-forming roller 65-75 cm, the diameters of large, medium and small discs, respectively, at least 600mm, 550 mm and 200 mm, the angle of sharpening of the discs within 55-650, the issue of stems within 64 - 69 trimming and diameter bars 3 mm, intensive defeat of chunk and high- quality creation of ridges is ensured.
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Andrulionis, Robertas, and Ieva Švagždytė. "RESEARCH OF EFFECTIVENESS OF DISK SHAPED ELEMENTS FOR OIL REMOVAL / DISKINIŲ NAFTOS SURINKIMO ELEMENTŲ EFEKTYVUMO TYRIMAS." Mokslas – Lietuvos ateitis 7, no. 6 (April 1, 2016): 624–27. http://dx.doi.org/10.3846/mla.2015.851.
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Influence of grooved disc rotation speed and inclination angle of fluid from surface on amount of removed liquid, was studied in this article. Stand with possibility to change disc, rotation speed of disc and angle was designed and assembled. U and V shaped groove discs were used. Edible and industrial oil SAE 80W90 were removed from water surface and collected into the flash. Optimal disc rotation speed, which is 15 rpm and disc inclination angle 00 were determined after analysis of results. Straipsnyje išnagrinėta skirtingais griovėtais diskais nuo vandens paviršiaus surenkamo skysčio ir jame esančio vandens kiekio priklausomybė nuo griovėto disko sukimosi greičio ir polinkio kampo. Buvo suprojektuotas stendas su galimybėmis pakeisti diską, disko sukimosi greičius bei polinkio kampą. Naudotų diskų griovelių geometrija V ir U formos. Nuo vandens paviršiaus disku buvo renkamas maistinis aliejus ir tepalai 80W90 į sugraduotą kolbą. Atlikus gautų rezultatų analizę, nustatytas optimalus disko sukimosi greitis, kuris lygus 15 aps/min, o polinkio kampas lygus 0°.
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ATANASIU, COSTICĂ, and STEFAN SOROHAN. "Buckling of perforated discs." Journal of Engineering Sciences and Innovation 9, no. 1 (March 22, 2024): 1–14. https://doi.org/10.56958/jesi.2024.9.1.1.
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The paper presents the results obtained regarding the stability of discs perforated by two, four and 96 circular holes. Circular discs are subjected to two types of loadings: diametrical compression by concentrated forces and radial compression produced by an equivalent uniformly distributed load on the contour of the disks. The influence of the radius of the holes, the distance between the holes and the way of applying the loads, on the value of the critical buckling load is investigated. The results obtained by the finite element method are compared with those obtained in the case of non-perforated disks with the same support conditions and required with the same loads. At the same time, the forms of loss of stability and the values of the buckling safety coefficients for the analyzed disks are determined
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ZHONG, HONGJIE, and CUNBIAO LEE. "PATHS OF FREELY FALLING DISKS." Modern Physics Letters B 23, no. 03 (January 30, 2009): 373–76. http://dx.doi.org/10.1142/s0217984909018436.
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The free falling motion of round thin disks in quiescent water was investigated experimentally. The mean density of the disks were about 1.05 g/cm3, slightly larger than water, and thickness to diameter ratio is 0.1. In this letter, We reported two cases with different mass distributions, in one case the disk's center of mass coincided with the geometry center and in another case it was deviated. Two CCD cameras were used to photograph the falling disk simultaneously, the disk's six degrees of freedom were obtained via a stereoscopic vision method. In the first case fluttering motion was observed, the disk's oscillatory motion confined in a vertical plane, and the pitching motion occurred about an axis normal to the plane. In the second case, steady helical falling was observed, the disk moved in a helical path at constant speed, the attacking angle is constant.
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Hamidov, Namik, Zabit Aslanov, and Gultakin Imanova. "SOME FEATURES OF THE OPERATING CAPACITY OF THE REDUCER." Scientific works/Elmi eserler 2 (April 2, 1996): 109–13. http://dx.doi.org/10.58225/sw.2022.2.109-113.
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Abstract. The main factor affecting the performance of the clutch is the load. The load on the clutch is sign-variable and uneven. It strongly depends on the state of the antenna system (with ice, without ice) as well as on the strength and direction of the wind. During operation, in places of the highest specific pressure, the discs seize and weld, which leads to deep tearing of the metal with the formation of deep grooves, ledges and depressions. When the disks seize, which is very often the case in operating conditions, the clutch works like a single shaft, and when the multi-ton cabin moves from its place, the disks do not slip relative to each other, a strong starting current occurs in the motor winding, and the protection system turns it off and the station. If the discs slip relative to each other, then the station also does not rotate. The analysis of friction clutches that were in operation revealed: the shape error has the greatest influence on the destruction of the disks; the wear of the disks in thickness is negligible Keywords: analysis of operational factors, clutch performance, disk surface roughness
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Funes, S.J.,, José G., and Enrico Maria Corsini. "Galaxy Disks and Disk Galaxies1." Publications of the Astronomical Society of the Pacific 112, no. 777 (November 2000): 1510–11. http://dx.doi.org/10.1086/317703.
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Yakhin, Sergey, Il'fat Aliakberov, and Adel Vakhitov. "SUBSTANTIATION OF PARAMETERS OF A ROTARY IMPLEMENT FOR SURFACE TREATMENT OF SOIL WITH INCLINED HEXAGONAL DISC." Vestnik of Kazan State Agrarian University 17, no. 4 (January 27, 2023): 106–11. http://dx.doi.org/10.12737/2073-0462-2023-106-111.
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For surface tillage, rotary implements with disk working bodies are widely used. In recent decades, intensive research has been carried out on the development of rotary tools with polygonal disks. They were implemented in practice in the form of hexagonal disks mounted on a shaft at an angle of 90° and performing the usual rotational movement around its axis. Of interest are polygonal discs, which are fixed obliquely on the shaft. The well-known tillage tool with inclined square discs was not implemented in practice, since it turned out to be technologically unstable and did not provide a uniform depth of tillage. In the developed soil-cultivating tool, these shortcomings are eliminated. As a result of the study, analytical dependences were obtained, which made it possible to substantiate the parameters of a tillage tool containing obliquely fixed hexagonal disks: the width of the tool (module) capture B = 1.8 m; number of rotary batteries - 2; disk diameter D = 0.32…0.48 m; angle of fastening of discs on the shaft > 50°…55°; distance between disc centers S = 0.100…0.105 m; the number of disks in the battery n = 17; the angle of rotation (displacement) of the disks one relative to the other around the axis of the shaft ɛ = 11.25°. A formula was also obtained to reveal the regularity of the change in the angle of entry of the disk into the soil. The calculation showed that this angle during the rotation of the disk is a variable parameter and varies within 72.5° ... 107.5°. This contributes to the self-cleaning of the inter-disk space from adhering soil and plant residues and is used in determining the traction resistance of the implement.
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Kachan, O. Ya, and S. O. Ulanov. "DETERMINATION OF REGULARITIES OF TREATMENT OF DISKS IN A FLUIDIZED BED OF ABRASIVE." Kosmìčna nauka ì tehnologìâ 29, no. 6 (December 9, 2023): 62–67. http://dx.doi.org/10.15407/knit2023.06.062.
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n this work, the main regularities of processing disks in a fluidized bed of abrasive are established.The research was carried out on the АПС-600A installation when processing disks in a fluidized bed of abrasive. When processing discs, abrasive grains of groups 24A, 63C, and a mixture of abrasive grains 24A63+24A20 (50 % + 50 %) were used.The grain size of the abrasive grains varied in the range № 20 … № 80.The processed disks were made of such alloys as VT3-1, VT-9, EI698-VD, steel 45 HRC 38...45, and aluminum alloy D1T. The peripheral speed of the parts is Vp = 5...40 m/s. The maximum air consumption is 2000 Nm 3/h. The pressure of the air that liquefies the abrasive in the air-falling chamber is 5...6 kPa. The disk was immersed in a liquefied layer of abrasive to a depth of 0.2...1.2 of the radius of the disk. The regularities of the dependence of the removal of various materials from the machined surface of the disks on the speed of the part, the grain size, and the brand of the abrasive grain have been established. The dependence of abrasive grain wear on the speed of the part and on its position along the height of the abrasive layer was experimentally established, which allowed forassigning rational modes of processing discs in a fluidized layer of abrasive. The main regularities of the processing of disks in a fluidized bed of abrasive have been established, and the influence of the main parameters of the processing process on the productivity and stability of the abrasive grain has been determined. The main regularities of the process of processing discs in a fluidized bed of abrasive have been established experimentally, which allowsfor determining the main parameters, technological conditions, and modes of the finishing operation of parts manufacturing.
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Lee, Jung Hoon. "Weak reducing disks and disk surgery." Journal of Knot Theory and Its Ramifications 27, no. 12 (October 2018): 1850069. http://dx.doi.org/10.1142/s0218216518500694.
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Let [Formula: see text] be an unknot in [Formula: see text]-bridge position in the [Formula: see text]-sphere. We give an example of a pair of weak reducing disks [Formula: see text] and [Formula: see text] for [Formula: see text] such that both disks obtained from [Formula: see text] ([Formula: see text]) by a surgery along any outermost disk in [Formula: see text], cut off by an outermost arc of [Formula: see text] in [Formula: see text], are not weak reducing disks, i.e. the property of weak reducibility of compressing disks is not preserved by a disk surgery.
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Montgomery, M. M. "Modeling Fluid Flow Effects in Close Binary and Protoplanetary Systems." Proceedings of the International Astronomical Union 7, S282 (July 2011): 549–50. http://dx.doi.org/10.1017/s1743921311028365.
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AbstractAccretion disks around some white dwarfs in Cataclysmic Variables are thought to tilt around the line of nodes by the lift force acting at the disk's center of pressure. We investigate whether protoplanetary disks can also experience disk tilt. We find that lift may be possible by an asymmetric, net uni-directional, in-falling gas/dust stream overflowing a bluff body (e.g., Class I sources) or inner annuli of young Class II sources if gas/dust is still in-falling and the aspect ratio and disk surface area are large enough. However, inner disks of Class II sources LkCa 15, UX Tau A, and Rox 44 are not large enough, and therefore disk tilt is not likely.
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Hincapié Mejía, Gina María, Juan Miguel Marín S., Luis Alberto Rios, and Gloria Restrepo. "Evaluating E. coli degradation using a rotatory disk photoreactor." Ingeniería e Investigación 27, no. 3 (September 1, 2007): 65–69. http://dx.doi.org/10.15446/ing.investig.v27n3.14846.
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Degradation of the bacterium E. coli was studied using a rotatory disk photoreactor manufactured in stainless steel to ascertain this photoreaction system’s behavior in different operating conditions. The photoreactor was equipped with 6 black light bulbs (BLB) used as a source of UV light and fitted with 7 removable disks made of common frosted glass impregnated with TiO2 photocatalyzer which were coupled to a rotation system. TiO2 was impregnated on the disks using the sol-gel method varying molar precursor gel ratios. Abrasion resistance, disk adhesion and surface uniformity tests were carried out for selecting the film presenting the best characteristics. Bacterial photodegradation studies were carried out using the following variable parameters: the disks’ rotation speed, radiation intensity and the number of discs which were directly related to the concentration of photocatalyzer in the system. Up to 64.3% degradation was achieved in 4 hours using 7 disks, low intensity and low rotation speed.
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Avramenko, R., S. Wolf, T. F. Illenseer, and S. Rehberg. "Selected aspects of the analysis of molecular line observations of edge-on circumbinary disks." Astronomy & Astrophysics 642 (October 2020): A127. http://dx.doi.org/10.1051/0004-6361/201935610.
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Context. Inner cavities, accretion arms, and density waves are characteristic structures in the density distribution of circumbinary disks. They are the result of the tidal interaction of the non-axisymmetric gravitational forces of the central binary with the surrounding disk and are most prominent in the inner region, where the asymmetry is most pronounced. Aims. The goal of this study is to test the feasibility of reconstructing the gas density distribution and quantifying properties of structures in the inner regions of edge-on circumbinary disks using multiple molecular line observations. Methods. The density distribution in circumbinary disks is calculated with 2D hydrodynamic simulations. Subsequently, molecular line emission maps are generated with 3D radiative transfer simulations. Based on these, we investigate the observability of characteristic circumbinary structures located in the innermost region for spatially resolved and unresolved disks. Results. We find that it is possible to reconstruct the inner cavity, accretion arms, and density waves from spatially resolved multi-wavelength molecular line observations of circumbinary disks seen edge-on. For the spatially unresolved observations only, an estimate can be derived for the density gradient in the transition area between the cavity and the disk’s inner rim.
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Khaibrakhmanov, Sergey A., Alexander E. Dudorov, and Andrey M. Sobolev. "Rising magnetic flux tubes as a source of IR-variability of the accretion disks of young stars." Proceedings of the International Astronomical Union 14, S345 (August 2018): 295–96. http://dx.doi.org/10.1017/s1743921319001431.
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AbstractWe investigate dynamics of slender magnetic flux tubes (MFT) in the accretion disks of young stars. Simulations show that MFT rise from the disk and can accelerate to 20-30 km/s causing periodic outflows. Magnetic field of the disk counteracts the buoyancy, and the MFT oscillate near the disk’s surface with periods of 10-100 days. We demonstrate that rising and oscillating MFT can cause the IR-variability of the accretion disks of young stars.
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Nakao, Yasushi. "Enhancement of Turbulent Viscosity by Global Magnetic Fields in Accretion Disks." Symposium - International Astronomical Union 188 (1998): 412. http://dx.doi.org/10.1017/s0074180900115773.
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A model of magnetohydrodynamic (MHD) turbulence in accretion disks with global magnetic fields is constructed using a second-order closure modeling of turbulence. The transport equations of the Reynolds stress tensor, the Maxwell stress tensor, and the cross-helicity tensor (the correlation of velocity fluctuation and magnetic fluctuation) are closed by second-order quantities using atwo-scale direct interaction approximation(TSDIA). The quantities appearing these equations are considered to be those averaged in the vertical direction of the disks. The turbulence is assumed to be stationary. We are interested only in the effects of the global magnetic fields on the turbulence in the disks, i.e., no dynamo processes are considered, and the global magnetic fields are supposed to be embedded in the diska priori.
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Angelo, Isabel, Gaspard Duchene, Karl Stapelfeldt, Zoie Telkamp, François Ménard, Deborah Padgett, Gerrit Van der Plas, et al. "Demographics of Protoplanetary Disks: A Simulated Population of Edge-on Systems." Astrophysical Journal 945, no. 2 (March 1, 2023): 130. http://dx.doi.org/10.3847/1538-4357/acbb01.
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Abstract The structure of protoplanetary disks plays an essential role in planet formation. A disk that is highly inclined, or “edge-on,” is of particular interest since its geometry provides a unique opportunity to study the disk’s vertical structure and radial extent. Candidate edge-on protoplanetary disks are typically identified via their unique spectral energy distributions (SEDs) and subsequently confirmed through high-resolution imaging. However, this selection process is likely biased toward the largest, most-massive disks, and the resulting sample may not accurately represent the underlying disk population. To investigate this, we generated a grid of protoplanetary disk models using radiative transfer simulations and determined which sets of disk parameters produce edge-on systems that could be recovered by the aforementioned detection techniques—i.e., identified by their SEDs and confirmed through follow-up imaging with the Hubble Space Telescope. In doing so, we adopt a quantitative working definition of “edge-on disks” (EODs) that is observation driven and agnostic about the disk inclination or other properties. Folding in empirical disk demographics, we predict an occurrence rate of 6.2% for EODs and quantify biases toward highly inclined, massive disks. We also find that EODs are underrepresented in samples of Spitzer-studied young stellar objects, particularly for disks with host masses of M ≲ 0.5 M ⊙. Overall, our analysis suggests that several dozen EODs remain undiscovered in nearby star-forming regions, and provides a universal selection process to identify EODs for consistent, population-level demographic studies.
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Sydorenko, Yuryi M., Bohdan Jo Semon, Vadim V. Yakovenko, Yevhen V. Ryzhov, and Eugene G. Ivanyk. "Spatial Distribution of Mass and Speed on Movement of Two Shrapnel Discs of Variable Thickness in Explosive Load." Defence Science Journal 70, no. 5 (October 8, 2020): 479–85. http://dx.doi.org/10.14429/dsj.70.14524.
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Results of studies of the explosive expansion of a set of shrapnel discs of natural crushing are described in the article. Set consisted of two disks of different thickness, but of a fixed total mass. The studies were carried out by computer simulation of shock-wave processes in a continuous formulation using the ANSYS/LS-DYNA program. The program of computer design foresees development of three-dimensional certainly-element model including, in accordance with symmetry of the examined system fourth part of the examined explosive system of casting block, with imposed on its knots of the proper scopes terms concerted with taken mixed Lagrangian-Eulerian approach within the framework of the continuum model. The effect of the order of installing disks of different thickness on the distribution of their mass and its velocity in the middle of the meridional angle of expansion is established. The analysis of the computer simulation presented on the basis of numerical studies on the distribution of the mass of the disks and its velocity of motion suggests that to create a narrow high-speed uniformly filled fragmentary mass of the axial flow, it is necessary to change the geometric shape of the disc so that in the central angular zones of the disks. This allows the velocity of the fragment mass to be aligned along the radius of the discs and to fill the first angular zones with the required mass of fragments.
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Plank, James S. "The Raid-6 Liber8Tion Code." International Journal of High Performance Computing Applications 23, no. 3 (June 2, 2009): 242–51. http://dx.doi.org/10.1177/1094342009106191.
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Large centralized and networked storage systems have grown to the point where the single fault tolerance provided by RAID-5 is no longer enough. RAID-6 storage systems protect k disks of data with two parity disks so that the system of k + 2 disks may tolerate the failure of any two disks. Coding techniques for RAID-6 systems are varied, but an important class of techniques are those with minimum density, featuring an optimal combination of encoding, decoding and modification complexity. The word size of a code has an impact on both how the code is laid out on each disk's sectors and how large k can be. Word sizes which are powers of two are especially important, since they fit precisely into file system blocks. Minimum density codes exist for many word sizes with the notable exception of eight. This paper fills that gap by describing a new code called The RAID-6 Liber8tion Code for this important word size. The description includes performance properties as well as details of the discovery process.
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Hristov, Krasimir, Nikolay Ishkitiev, Marina Miteva, and Nataliya Gateva. "EVALUATION OF THE ADHESION AND MORPHOLOGY OF STEM CELLS FROM APICAL PAPILLA IN DIRECT CONTACT WITH MTA AND BIODENTINE." Journal of IMAB - Annual Proceeding (Scientific Papers) 28, no. 4 (November 2, 2022): 4655–59. http://dx.doi.org/10.5272/jimab.2022284.4655.
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Purpose: To investigate the use of tricalcium silicate cement Biodentine as an alternative to MTA in regenerative endodontic procedures by assessing the morphology and adhesion of stem cells from apical papilla in direct contact with these materials Materials/Methods: Glass ionomer cement, MTA and Biodentine disks with identical size were created. Stem cells from apical papilla were incubated on these disks, and their size and morphology were assessed with a scanning electron microscope. Results: No adhesion of SCAP was observed when incubating cells with glass ionomer disks, which can be explained by a decrease in pH and a delay in cell proliferation. Cell adhesion was observed in the groups incubated in the presence of MTA and Biodentine discs. Cells adhered to the calcium silicate cements have different morphology and can be round or flat, with several processes. Conclusions: Stem cells from apical papilla adhere to MTA and Biodentiе when in direct contact with discs made of these materials. The cells show different morphology and can be round or flat, with several processes. Calcium silicate cements have biocompatibility and bioactivity and they are suitable materials for the biological treatment of pulp and regenerative endodontics.
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Scorza, Cecilia, and Ralf Bender. "Disky Ellipticals in the Hubble Sequence." Symposium - International Astronomical Union 171 (1996): 55–59. http://dx.doi.org/10.1017/s0074180900232154.
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About one third of the elliptical galaxies show disky isophotes (Bender et al. 1989). These are low luminosity objects, are rotationally flattened (Carter 1987, Bender 1988b, Nieto 1988), are much weaker radio emitters than ellipticals in average and show no strong X-ray emission in excess of their discrete sources contribution. They have pointed isophotes which are thought to reflect the presence of embedded stellar disks. A large number of these disks could be hidden due to low inclinations (Rix and White 1990). Because of these properties, which makes them strongly resemble S0 galaxies, it has been suggested that disky ellipticals form together with S0s and spirals a continuous transition in D/B ratio in the Hubble sequence (Bender 1988b, Nieto 1988). However, until the present, this hypothesis had not been investigated throughout.
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Ekkerdt, A. A. "Problems of Studying the Purpose of Disks with Concentric Ornament in Russian Archaeology." Izvestiya of Altai State University, no. 3(125) (July 12, 2022): 73–76. http://dx.doi.org/10.14258/izvasu(2022)3-11.
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The article is devoted to a historiographical review of scientific works, which provides an analysis and purpose of disks with concentric ornament, common in the Urals and Siberia in the first half of the 1st millennium AD. The stages of the history of the study of bronze disks with concentric ornament with the definition of their purpose in a particular complex are distinguished and characterized. When describing each of the stages, the most significant works of the authors who worked during this period are given within the framework of the designated topic, the main ideas and concepts are highlighted. The author provides several points of view of researchers on the purpose of disks with concentric ornament. The first considers disks as elements of armor or armor. The second defines them as objects of ritual and religious practices. The third notes the purely aesthetic function of the discs as costume decorations. The fourth combines several interpretations about the place and role of these products in the life of the ancient population of Siberia, as well as the reflection of the idea of the calendar. As a result, it is concluded that currently there is no consensus about the purpose of disks with concentric ornament, and different researchers agree only that the local population of Siberia and the Urals used these imports differently.
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Qian, Yansong, and Yanqin Wu. "Shadows Wreak Havoc in Transition Disks." Astrophysical Journal 976, no. 1 (November 1, 2024): 5. http://dx.doi.org/10.3847/1538-4357/ad8233.
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Abstract We demonstrate that shadows cast on a protoplanetary disk can drive it eccentric. Stellar irradiation dominates heating across much of these disks, so an uneven illumination can have interesting dynamical effects. Here, we focus on transition disks. We carry out 3D Athena++ simulations, using a constant thermal relaxation time to describe the disk’s response to changing stellar illumination. We find that an asymmetric shadow, a feature commonly observed in real disks, perturbs the radial pressure gradient and distorts the fluid streamlines into a set of twisted ellipses. Interactions between these streamlines have a range of consequences. For a narrow ring, an asymmetric shadow can sharply truncate its inner edge, possibly explaining the steep density drop-offs observed in some disks and obviating the need for massive perturbers. For a wide ring, such a shadow can dismantle it into two (or possibly more) eccentric rings. These rings continuously exert torque on each other and drive gas accretion at a healthy rate, even in the absence of disk viscosity. Signatures of such twisted eccentric rings may have already been observed as, e.g., twisted velocity maps inside gas cavities. We advocate for more targeted observations and for a better understanding on the origin of such shadows.
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Kormendy, John. "Internal secular evolution in disk galaxies: the growth of pseudobulges." Proceedings of the International Astronomical Union 3, S245 (July 2007): 107–12. http://dx.doi.org/10.1017/s1743921308017407.
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AbstractObservational and theoretical evidence that internal, slow (“secular”) evolution reshapes galaxy disks is reviewed in Kormendy & Kennicutt (2004). This update has three aims. First, I emphasize that this evolution is very general – it is as fundamental to the evolution of galaxy disks as (e. g.) core collapse is to globular clusters, as the production of hot Jupiters is to the evolution of protoplanetary disks, and as evolution to red giants containing proto-white-dwarfs is to stellar evolution. One consequence for disk galaxies is the buildup of dense central components that get mistaken for classical (i. e., merger-built) bulges but that were grown out of disk stars and gas. We call these pseudobulges. Second, I review new results on pseudobulge star formation and structure and on the distinction between boxy and disky pseudobulges. Finally, I highlight how these results make a galaxy formation problem more acute. How can hierarchical clustering produce so many pure disk galaxies with no evidence for merger-built bulges?
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Domotenko, Lubov` Viktorovna, A. Yu Mironov, I. S. Kosilova, and A. P. Shepelin. "Standardness of antimicrobial discs by various manufacturers in the light of import substitution." Russian Clinical Laboratory Diagnostics 67, no. 9 (September 12, 2022): 550–56. http://dx.doi.org/10.51620/0869-2084-2022-67-9-550-556.
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In connection with the introduction of economic sanctions against the Russian Federation by the United States, the European Union, Japan, and a number of other countries, import substitution is becoming one of the strategic objectives of the Russian economy The comparative assessment of standardness and effectiveness of six antimicrobial commercial producer-varying disks for clinical and test strains of microorganisms has been conducted. It is based on analyzing of the variation coefficient (Cv) of inhibition zone diameters, mean values, and diameter values ranges, which are indicators of reproducibility, accuracy and efficiency, respectively. Discs from BD BBL result in insignificant variations of inhibition zone diameters, providing accurate and reproducible data. Imported discs available on the national market from a friendly country produced by HiMedia Company are showed more variation and inferior in quality to BD BBL ones. There are satisfactory results for some domestic discs, but discs with imipenem, meropenem, ciprofloxacin and gentamicin are not standard enough to assure reproducible results. To have reliable data on antibiotic susceptibility of infectious agents, incoming and routine quality control of antimicrobial disks is needed as a compulsory procedure for every bacteriological laboratory.
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Pfalzner, S., S. Umbreit, and Th Henning. "Disk‐Disk Encounters between Low‐Mass Protoplanetary Accretion Disks." Astrophysical Journal 629, no. 1 (August 10, 2005): 526–34. http://dx.doi.org/10.1086/431350.
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Robert, C. M. T., A. Crida, E. Lega, H. Méheut, and A. Morbidelli. "Toward a new paradigm for Type II migration." Astronomy & Astrophysics 617 (September 2018): A98. http://dx.doi.org/10.1051/0004-6361/201833539.
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Context. Giant planets open gaps in their protoplanetary and subsequently suffer so-called type II migration. Schematically, planets are thought to be tightly locked within their surrounding disks, and forced to follow the viscous advection of gas onto the central star. This fundamental principle, however, has recently been questioned as migrating planets were shown to decouple from the gas’ radial drift. Aims. In this framework, we question whether the traditionally used linear scaling of migration rate of a giant planet with the disk’s viscosity still holds. Additionally, we assess the role of orbit-crossing material as part of the decoupling mechanism. Methods. We have performed 2D (r, θ) numerical simulations of point-mass planets embedded in locally isothermal α-disks in steady-state accretion, with various values of α. Arbitrary planetary accretion rates were used as a means to diminish or nullify orbit-crossing flows. Results. We confirm that the migration rate of a gap-opening planet is indeed proportional to the disk’s viscosity, but is not equal to the gas drift speed in the unperturbed disk. We show that the role of gap-crossing flows is in fact negligible. Conclusions. From these observations, we propose a new paradigm for type II migration: a giant planet feels a torque from the disk that promotes its migration, while the gap profile relative to the planet is restored on a viscous timescale, thus limiting the planet migration rate to be proportional to the disk’s viscosity. Hence, in disks with low viscosity in the planet region, type II migration should still be very slow.
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Ertel, S., S. Wolf, and J. Rodmann. "Observing planet-disk interaction in debris disks." Astronomy & Astrophysics 544 (July 26, 2012): A61. http://dx.doi.org/10.1051/0004-6361/201219236.
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Bai, Xue-Ning, Jiani Ye, Jeremy Goodman, and Feng Yuan. "MAGNETO-THERMAL DISK WINDS FROM PROTOPLANETARY DISKS." Astrophysical Journal 818, no. 2 (February 18, 2016): 152. http://dx.doi.org/10.3847/0004-637x/818/2/152.
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GLUTSCH, S., B. ADOLPH, and F. BECHSTEDT. "Excitons in quantum disks and disk arrays." Le Journal de Physique IV 03, no. C5 (October 1993): 373–76. http://dx.doi.org/10.1051/jp4:1993578.
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Essa, Kevin. "Manufacturing disks and disk drives: Open problems." Journal of the Acoustical Society of America 95, no. 5 (May 1994): 2814. http://dx.doi.org/10.1121/1.409701.
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Kock, Joost P. de, Seiji Kobayashi, and Hisayuki Yamatsu. "Disk Noise Measurement System for Optical Disks." Optical Review 2, no. 6 (November 1995): 424–33. http://dx.doi.org/10.1007/s10043-995-0424-0.
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Bohn, A. J., M. Benisty, K. Perraut, N. van der Marel, L. Wölfer, E. F. van Dishoeck, S. Facchini, et al. "Probing inner and outer disk misalignments in transition disks." Astronomy & Astrophysics 658 (February 2022): A183. http://dx.doi.org/10.1051/0004-6361/202142070.
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Context. Transition disks are protoplanetary disks with dust-depleted cavities, possibly indicating substantial clearing of their dust content by a massive companion. For several known transition disks, dark regions interpreted as shadows have been observed in scattered light imaging and are hypothesized to originate from misalignments between distinct regions of the disk. Aims. We aim to investigate the presence of misalignments in transition disks. We study the inner disk (<1 au) geometries of a sample of 20 well-known transition disks with Very Large Telescope Interferometer (VLTI) GRAVITY observations and use complementary 12CO and 13CO molecular line archival data from the Atacama Large Millimeter/submillimeter Array (ALMA) to derive the orientation of the outer disk regions (>10 au). Methods. We fit simple parametric models to the visibilities and closure phases of the GRAVITY data to derive the inclination and position angle of the inner disks. The outer disk geometries were derived from Keplerian fits to the ALMA velocity maps and compared to the inner disk constraints. We also predicted the locations of expected shadows for significantly misaligned systems. Results. Our analysis reveals six disks to exhibit significant misalignments between their inner and outer disk structures. The predicted shadow positions agree well with the scattered light images of HD 100453 and HD 142527, and we find supporting evidence for a shadow in the south of the disk around CQ Tau. In the other three targets for which we infer significantly misaligned disks, V1247 Ori, V1366 Ori, and RY Lup, we do not see any evident sign of shadows in the scattered light images. The scattered light shadows observed in DoAr 44, HD 135344 B, and HD 139614 are consistent with our observations, yet the underlying morphology is likely too complex to be described properly by our models and the accuracy achieved by our observations. Conclusions. The combination of near infrared and submillimeter interferometric observations allows us to assess the geometries of the innermost disk regions and those of the outer disk. Whereas we can derive precise constraints on the potential shadow positions for well-resolved inner disks around Herbig Ae/Be stars, the large statistical uncertainties for the marginally resolved inner disks around the T Tauri stars of our sample make it difficult to extract conclusive constraints for the presence of shadows in these systems.
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Fraser-McKelvie, A., and L. Cortese. "Beyond Galaxy Bimodality: The Complex Interplay between Kinematic Morphology and Star Formation in the Local Universe." Astrophysical Journal 937, no. 2 (October 1, 2022): 117. http://dx.doi.org/10.3847/1538-4357/ac874d.
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Abstract It is generally assumed that galaxies are a bimodal population in both star formation and structure; star-forming galaxies are disks, while passive galaxies host large bulges or are entirely spheroidal. Here we test this scenario by presenting a full census of the kinematic morphologies of a volume-limited sample of galaxies in the local universe extracted from the MaNGA galaxy survey. We measure the integrated stellar line-of-sight velocity to velocity dispersion ratio (V/σ) for 4574 galaxies in the stellar mass range 9.75 < log M ⋆ [ M ⊙ ] < 11.75 . We show that at fixed stellar mass, the distribution of V/σ is not bimodal, and that a simple separation between fast and slow rotators is oversimplistic. Fast rotators are a mixture of at least two populations, referred to here as dynamically cold disks and intermediate systems, with disks dominating in both total stellar mass and number. When considering star-forming and passive galaxies separately, the star-forming population is almost entirely made up of disks, while the passive population is mixed, implying an array of quenching mechanisms. Passive disks represent ∼30% (both in number and mass) of passive galaxies, nearly a factor of two higher than that of slow rotators, reiterating that these are an important population for understanding galaxy quenching. These results paint a picture of a local universe dominated by disky galaxies, most of which become somewhat less rotation-supported upon or after quenching. While spheroids are present to a degree, they are certainly not the evolutionary end point for the majority of galaxies.
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Yoshida, Tomohiro C., Hideko Nomura, Kenji Furuya, Richard Teague, Charles J. Law, Takashi Tsukagoshi, Seokho Lee, Christian Rab, Karin I. Öberg, and Ryan A. Loomis. "The First Spatially Resolved Detection of 13CN in a Protoplanetary Disk and Evidence for Complex Carbon Isotope Fractionation." Astrophysical Journal 966, no. 1 (April 25, 2024): 63. http://dx.doi.org/10.3847/1538-4357/ad2fb4.
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Abstract Recent measurements of carbon isotope ratios in both protoplanetary disks and exoplanet atmospheres have suggested a possible transfer of significant carbon isotope fractionation from disks to planets. For a clearer understanding of the isotopic link between disks and planets, it is important to measure the carbon isotope ratios in various species. In this paper, we present a detection of the 13CN N = 2 − 1 hyperfine lines in the TW Hya disk with the Atacama Large Millimeter/submillimeter Array. This is the first spatially resolved detection of 13CN in disks, which enables us to measure the spatially resolved 12CN/13CN ratio for the first time. We conducted nonlocal thermal equilibrium modeling of the 13CN lines in conjunction with previously observed 12CN lines to derive the kinetic temperature, H2 volume density, and column densities of 12CN and 13CN. The H2 volume density is found to range between (4 − 10) × 107 cm−3, suggesting that CN molecules mainly reside in the disk's upper layer. The 12CN/13CN ratio is measured to be 70 − 6 + 9 at 30 < r < 80 au from the central star, which is similar to the 12C/13C ratio in the interstellar medium. However, this value differs from the previously reported values found for other carbon-bearing molecules (CO and HCN) in the TW Hya disk. This could be self-consistently explained by different emission layer heights for different molecules combined with preferential sequestration of 12C into the solid phase toward the disk midplane. This study reveals the complexity of the carbon isotope fractionation operating in disks.
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Lysenko, Serhii. "The Influence of the Tribological Efficiency of Resource-Determining Яonjugations of Transmission Parts on the Operational Reliability of Transport Vehicles". Central Ukrainian Scientific Bulletin. Technical Sciences 2, № 5(36) (2022): 213–24. http://dx.doi.org/10.32515/2664-262x.2022.5(36).2.213-224.
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This work examines the conditions of tribological efficiency of couplings of TM transmission discs as resource-determining parts and its influence on the operational reliability of machines. The change in hydrodynamic friction, oil consumption, oil carrying capacity by rotating disks in both laminar and turbulent modes of transmission oil flow is substantiated. The nature of oil discharge from the working surface of the disk in laminar and turbulent modes is considered. Based on the system of the Navier-Stokes equation, the change in the effective characteristics of the coupled transmission discs is substantiated: carrying capacity and oil consumption. The nature of oil discharge from the working surface of the transmission disc is considered, taking into account the friction forces and inertia forces. The dependence of the moment of hydrodynamic resistance on a number of parameters, as well as the relative moment of resistance on the Reynolds and Froude criteria, was investigated as the efficiency of the coupled discs of the transmission of transport vehicles. A qualitative graphical dependence of the moment of hydrodynamic resistance of tribocouplers of disks on the angular speed of their rotation is constructed, with the selection of characteristic zones, and a description of the physical picture of the processes in them is given. The well-founded dependence of the moment of hydrodynamic resistance on a number of influencing parameters, as well as the relative moment of resistance in the multiplicative model representation through criterion dimensionless complexes. The set of processes occurring in the tribo-coupling of disks depending on the angular speed of their rotation in five selected zones has been clarified. It is shown that the efficiency and reliability of the TM transmission depends on the total frictional force acting on the tribo-coupling of the discs, load and operating conditions.
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Gryadunov, Sergey S., and Vladimir V. Sivakov. "The Use of Surfacing Materials to Increase the Durability of Disc Harrow Working Elements." Engineering Technologies and Systems 31, no. 4 (December 30, 2021): 544–58. http://dx.doi.org/10.15507/2658-4123.031.202104.544-558.
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Introduction. For surface tillage operation there widely used disc harrows, working bodies of which are discs wearing out during operation. The wear intensity of discs depends on the wear resistance of their working surfaces, working modes and properties of the cultivated soil. It has been found that an effective way to increase the life of discs is surfacing them with wear-resistant materials. The aim of the work is to study the wear out of surfacing materials, which can be used to harden discs and to make recommendation for the use of these materials in the repair departments of agricultural enterprises. Materials and Methods. Surfacing with electrodes T-590 and powder wires PP-Np200Kh15S1GRT, VELTEK-N560.02 and PP-Np280Kh9F7SG4 were taken as test materials. For wear tests of materials in abrasive mass, there was used an apparatus to simulate the moisture content and composition (sandy loam or loam) of the soil. In the disk-pad tests, the effect of abrasive particle size, load and sliding friction velocity on the wear of the materials was studied. In field tests, wear of the disks made of 65G steel, surfaced toothed and solid disks were monitored. Results. Laboratory studies of the materials revealed the effect of soil moisture and composition, load, abrasive grit and sliding friction velocity on wear. The main factor determining the wear resistance of materials is their structural state. The indexes of wear resistance of surfacing were determined during the laboratory tests and confirmed by field tests. Discussion and Conclusion. Surfacing with flux-cored wire PP-Np280Kh9F7SG4 has the highest wear resistance of the studied materials. The technology of hard-facing disks with modern materials, in particular with flux-cored wire PP-Np280Kh9F7SG4, can be implemented in repair departments of agricultural enterprises when they have the equipment for hard-facing and sharpening of working surfaces.
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Kamali, F., C. Henkel, S. Koyama, C. Y. Kuo, J. J. Condon, A. Brunthaler, M. J. Reid, et al. "Accretion disk versus jet orientation in H2O megamaser galaxies." Astronomy & Astrophysics 624 (April 2019): A42. http://dx.doi.org/10.1051/0004-6361/201834600.
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Context. An essential part of the paradigm describing active galactic nuclei is the alignment between the radio jet and the associated rotation axis of the sub-pc accretion disks. Because of the small linear and angular scales involved, this alignment has not yet been checked in a sufficient number of low luminosity active galactic nuclei (LLAGNs). Aims. The project examines the validity of this paradigm by measuring the radio continuum on the same physical scale as the accretion disks to investigate any possible connection between these disks and the radio continuum. Methods. We observed a sample of 18 LLAGNs in the 4.8 GHz (6 cm) radio continuum using the Very Long Baseline Array (VLBA) with 3.3–6.5 ms resolution. The sources were selected to show both an edge-on accretion disk revealed by 22 GHz H2O megamaser emission and signatures of a radio jet. Furthermore, the sources were previously detected in 33 GHz radio continuum observations made with the Very Large Array. Results. Five out of 18 galaxies observed were detected at 8σ or higher levels (Mrk 0001, Mrk 1210, Mrk 1419, NGC 2273, and UGC 3193). While these five sources are known to have maser disks, four of them exhibit a maser disk with known orientation. For all four of these sources, the radio continuum is misaligned relative to the rotation axis of the maser disk, but with a 99.1% confidence level, the orientations are not random and are confined to a cone within 32° of the maser disk’s normal. Among the four sources the misalignment of the radio continuum with respect to the normal vector to the maser disk is smaller when the inner radius of the maser disk is larger. Furthermore, a correlation is observed between the 5 GHz VLBA radio continuum and the [OIII] luminosity and also with the H2O maser disk’s inner radius.
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Lee, D. W., E. J. Lee, Sung Su Chun, Myun Whan Ahn, I. W. Song, I. K. Kang, and Suk Young Kim. "A Collagen Grafting on Hydroxyapatite to Enhancement of Bone Cell Attachment." Key Engineering Materials 396-398 (October 2008): 41–45. http://dx.doi.org/10.4028/www.scientific.net/kem.396-398.41.
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A collagen material was chemically grafted on hydroxyapatite (HA) to enhance bone cell attachment because the collagen is a major constituent of connective tissues and has been regarded as one of the most excellent coating materials for bone bonding. First, HA disks were prepared with 12mm diameter and 1mm thickness. And then collagen (type I) was immobilbized on the HA surface using a 3-APTES coupling agent on HA disk surfaces. MC3T3-E1 osteoblasts were seeded on the collagen-grafted and non-grated HA disks and cultured for 4 hrs to evaluate the cell adhesion on the HA discs. The Attached cell morphology on discs was observed with a fluorescent optical microscopy (FOM) and a scanning electron microscopy (SEM). The osteoblasts on the collagen-grafted sample were more spread than those on the non-grafted sample. It is believed that collagen-grafted HA surface provides suitable sites for cell attaching due to the high biocompatibility of collagen.
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Leiendecker, Harrison, Hannah Jang-Condell, Neal J. Turner, and Adam D. Myers. "Dust Rings and Cavities in the Protoplanetary Disks around HD 163296 and DoAr 44." Astrophysical Journal 941, no. 2 (December 1, 2022): 172. http://dx.doi.org/10.3847/1538-4357/aca32d.
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Abstract We model substructure in the protoplanetary disks around DoAr 44 and HD 163296 in order to better understand the conditions under which planets may form. We match archival millimeter-wavelength thermal emission against models of the disks’ structure that are in radiation balance with the starlight heating and in vertical hydrostatic equilibrium, and then we compare to archival polarized scattered near-infrared images of the disks. The millimeter emission arises in the interior, while the scattered near-infrared radiation probes the disks’ outer layers. Our best model of the HD 163296 disk has dust masses 81 ± 13 M ⊕ in the inner ring at 68 au and 82 − 16 + 26 M ⊕ in the outer ring at 102 au, both falling within the range of estimates from previous studies. Our DoAr 44 model has total dust mass 84 − 3.5 + 7.0 M ⊕. Unlike HD 163296, DoAr 44 as of yet has no detected planets. If the central cavity in the DoAr 44 disk is caused by a planet, the planet’s mass must be at least 0.5 M J and is unlikely to be greater than 1.6 M J. We demonstrate that the DoAr 44 disk's structure with a bright ring offset within a fainter skirt can be formed by dust particles drifting through a plausible distribution of gas.
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Tanaka, Hidekazu, Youhei Himeno, and Shigeru Ida. "Dust Growth and Settling in Protoplanetary Disks and Disk Spectral Energy Distributions. I. Laminar Disks." Astrophysical Journal 625, no. 1 (May 20, 2005): 414–26. http://dx.doi.org/10.1086/429658.
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Pérez, Laura M. "Formation and Evolution of Protoplanetary Disks: Observations and Modeling of Jets, Disks, and Disk Substructures." Proceedings of the International Astronomical Union 14, S345 (August 2018): 96–101. http://dx.doi.org/10.1017/s1743921319002278.
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AbstractPlanet formation takes place in the gaseous and dusty disks that surround young stars, known as protoplanetary disks. With the advent of sensitive observations and together with developments in theory, our field is making rapid progress in understanding how the evolution of protoplanetary disks takes place, from its inception to the end result of a fully-formed planetary system. In this review, I discuss how observations that trace both the dust and gas components of these systems inform us about their evolution, mass budget, and chemistry. Particularly, the process of disk evolution and planet formation will leave an imprint on the distribution of solid particles at different locations in a protoplanetary disk, and I focus on recent observational results at high angular resolution in the sub-millimeter regime, which have revealed a variety of substructures present in these objects.
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Luo, Siqiang, Yifeng Luo, Shuigeng Zhou, Gao Cong, and Jihong Guan. "DISKs." Proceedings of the VLDB Endowment 5, no. 12 (August 2012): 1966–69. http://dx.doi.org/10.14778/2367502.2367549.
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Rafikov, Roman R. "Protoplanetary Disks as (Possibly) Viscous Disks." Astrophysical Journal 837, no. 2 (March 15, 2017): 163. http://dx.doi.org/10.3847/1538-4357/aa6249.
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Kang, Byeonguk, Jongmin Choi, and Hee-Kap Ahn. "Intersecting disks using two congruent disks." Computational Geometry 110 (March 2023): 101966. http://dx.doi.org/10.1016/j.comgeo.2022.101966.
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Ghafourian, Neda, and Mahmood Roshan. "Evolution of disk galaxies in MOdified Gravity (MOG)." Proceedings of the International Astronomical Union 14, S353 (June 2019): 152–53. http://dx.doi.org/10.1017/s1743921319008810.
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AbstractEvolution and the formation of bars in the galactic disks is studied in the context of Modified Gravity (MOG) by using N-body simulations. It is found that changing the value of free parameters of the model can effectively alter the strength of the bar and disk’s stability.
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Vorobyov, Eduard, and Christian Theis. "Structure Formation in Anisotropic Disks." Proceedings of the International Astronomical Union 2, S235 (August 2006): 143. http://dx.doi.org/10.1017/s1743921306005758.
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The majority of normal disk galaxies are characterized by non-axisymmetric structures like spirals or bars. These structural elements have been widely discussed in the literature as a result of gravitational instabilities which are connected to growing density waves or global instabilities of disks. A first insight into the properties of galactic discs was provided by linear stability analysis. However, a disadvantage of linear stability analysis remained its restriction to small perturbations, both in amplitude and wavelength. Thus, numerical simulations, especially hydrodynamical and stellar-hydrodynamical simulations became a primary tool for the analysis of galactic evolution.
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WILSON, R. E., and DIRK TERRELL. "Learning about Algol Disks-Learning from Algol Disksa." Annals of the New York Academy of Sciences 675, no. 1 (December 1992): 65–74. http://dx.doi.org/10.1111/j.1749-6632.1992.tb56790.x.
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Nikolayev, V. A. "Geometric, kinematic and dynamic parameters of the disc ripper." Russian Automobile and Highway Industry Journal 18, no. 5 (November 25, 2021): 476–87. http://dx.doi.org/10.26518/2071-7296-2021-18-5-476-487.
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Introduction. The unit of continuous action for the formation of the underlying layer is designed to increase labour productivity in the construction of roads and other objects, for the construction of which it is necessary to remove the upper layer of soil. For loosening of soil in the unit used bit-like working bodies. Often, disc working bodies are used to cut the soil. Therefore, the expediency of using passive discs in road-building technical means, in particular, in the unit of continuous action for the formation of the underlying layer of highways, is of practical interest. Despite the large number of works, a detailed analysis of the operation of passive disks was not made. Therefore, in order to compare the energy costs for cutting the soil with passive discs and chisel-shaped working bodies, it is necessary to make a theoretical analysis of the operation of passive disks. Analysis of the energy costs of the disk ripper cannot be carried out without having the approximate values of its geometric, kinematic and dynamic parameters.The method of research. As part of a continuous unit to form the underlying layer of roads, each disc would be clamped with soil on both sides and carried out clamped cutting. Therefore, a disk ripper is adopted for analysis, aggregated with a separate energy device. On the basis of the constructive layout, rational geometric parameters of the disk ripper are revealed. The method of calculation of its kinematic and dynamic parameters is developed. In particular, the method of determining the weighted average circumferental velocity of the disk, the angular velocity of the disk and the circumferental velocity of the point on the edge of the disk blade is considered. The modes of cutting the soil by various parts of the disk are considered.Results. On the basis of the developed technique, the dependence of the minimum diameter of the disk on the depth of soil development was revealed. The moment of resistance of the soil to the rotation of the disks is calculated. The horizontal and vertical component of soil resistance to the front disc carrying out clamped cutting and subsequent discs carrying out semi-clamped cutting of the soil are determined. The necessary thrust force of the energy device for cutting the soil with a disk ripper and the dependence of the thrust force of the energy device for cutting the soil on the depth of soil development were revealed. The performance of the unit, including the power device and the disk ripper, is calculated.Conclusion. Since as part of the unit of continuous action for the formation of the underlying layer of roads, the disks will carry out clamped cutting of the soil, for preliminary loosening of the soil with disks, it is more expedient to use a separate unit, including an energy device and a disk ripper. On the basis of the theoretical studies carried out, the necessary thrust force of the energy device for cutting the soil and the total traction force necessary to move the disc ripper were revealed. The performance of the unit is calculated. To compare the energy costs for cutting the soil with passive discs and chisel-shaped working bodies, it is necessary to make a theoretical analysis of the energy costs for the operation of passive disks.
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Liu, Xia, Lin Xiao, and Li Zhang. "Long-lived Prptoplanetary disk Formation." Journal of Physics: Conference Series 2457, no. 1 (March 1, 2023): 012040. http://dx.doi.org/10.1088/1742-6596/2457/1/012040.
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Abstract Recently, protoplanetary disks around M dwarf stars have had longer ages than that typical protoplanetary disks. These long-lived protoplanetary disks imply that some protoplanetary disks suffer from a low-radiation. On the other hand, the host star’s masses around these protoplanetary disks are very low. We do not know whether long-lived protoplanetary disks can survive around stars with higher mass. In this work, we explore how protoplanetary disks lose their masses and how protoplanetary disk lifetimes dextral photoevaporation on host star mass. We find that only low-mass stars (< 0.5 M*) can host lone-lived protoplanetary disks (∼45 Myr). When star masses > 0.7 M*, the protoplanetary disk lifetimes drop below 45 Myr quickly because of the strong accretion and photoevaporation. The host stars with ∼2 M* may have protoplanetary disks with a lifetime of up to only 14 Myr. According to observations and our simulations, we consider that long-lived protoplanetary disks can only survive around M dwarf stars.
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Ryzhkov, A. V., A. V. Machkarin, and K. V. Kazakov. "Comparative analysis of soil discarding by spherical disks." IOP Conference Series: Earth and Environmental Science 845, no. 1 (November 1, 2021): 012138. http://dx.doi.org/10.1088/1755-1315/845/1/012138.
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Abstract The article presents data on the influence of various types of spherical disks on the discarding of soil in the horizontal and vertical planes during its processing. These studies were conducted in order to optimize the selection of working bodies of disk tillage machines in terms of resistance and processing quality. Three types of disks were used in the comparative analysis. Two types of discs with cutouts and one solid spherical disc. On one type of disk, the cutouts are made in the form of circular arcs, and on the other-in the form of arcs of a logarithmic spiral. The conducted studies have shown that within the working surface of the disk, the trajectories of movement of soil particles under the influence of the three types of disks under study differ little from each other. Although it can be noted that the steeper rise of the trajectory in the vertical plane provides a solid disk, and the smallest rise of the trajectory - at the disk with cutouts in the form of a logarithmic spiral. In the horizontal plane, the longitudinal movement of the soil mass is less in disks with cutouts, especially in a disk with cutouts along the arc of a logarithmic spiral. As a result of these studies, it was revealed that the disk working bodies with cutouts on the cutting edge in the form of arcs of a logarithmic spiral showed the best quality and energy indicators.
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Kondo, Katsushi, Satoshi Okuzumi, and Shoji Mori. "The Roles of Dust Growth in the Temperature Evolution and Snow Line Migration in Magnetically Accreting Protoplanetary Disks." Astrophysical Journal 949, no. 2 (June 1, 2023): 119. http://dx.doi.org/10.3847/1538-4357/acc840.
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Abstract The temperature structure of protoplanetary disks provides an important constraint on where in the disks rocky planets like our own form. Recent nonideal magnetohydrodynamical (MHD) simulations have shown that the internal Joule heating associated with magnetically driven disk accretion is inefficient at heating the disk midplane. A disk temperature model based on the MHD simulations predicts that in a disk around a solar-mass young star, the water snow line can move inside the current Earth’s orbit within 1 Myr after disk formation. However, the efficiency of the internal Joule heating depends on the disk’s ionization and opacity structures, both of which are governed by dust grains. In this study, we investigate these effects by combining the previous temperature model for magnetically accreting disks with a parameterized model for the grain size and vertical distribution. Grain growth enhances the gas ionization fraction and thereby allows Joule heating to occur closer to the midplane. However, growth beyond 10 μm causes a decrease in the disk opacity, leading to a lower midplane temperature. The combination of these two effects results in the midplane temperature being maximized when the grain size is in the range 10–100 μm. Grain growth to millimeter sizes can also delay the snow line’s migration to the 1 au orbit by up to a few million years. We conclude that accounting for dust growth is essential for accurately modeling the snow line evolution and terrestrial planet formation in magnetically accreting protoplanetary disks.