Effects of multiple shapes for steady flow with transformer oil+Fe_(3)O_(4)+TiO_(2) between two stretchable rotating disks

In this study,we examine the effects of various shapes of nanoparticles in a steady flow of hybrid nanofluids between two stretchable rotating disks.The steady flow of hybrid nanofluids with transformer oil as the base fluid and Fe_(3)O_(4)+TiO_(2)as the hybrid nanofluid is considered.Several shapes of Fe_(3)O_(4)+TiO_(2)hybrid nanofluids,including sphere,brick,blade,cylinder,and platelet,are studied.Every shape exists in the same volume of a nanoparticle.The leading equations(partial differential equations(PDEs))are transformed to the nonlinear ordinary differential equations(ODEs)with the help of similarity transformations.The system of equations takes the form of ODEs depending on the boundary conditions,whose solutions are computed numerically by the bvp4c MATLAB solver.The outputs are compared with the previous findings,and an intriguing pattern is discovered,such that the tangential velocity is increased for the rotation parameter,while it is decreased by the stretching values because of the lower disk.For the reaction rate parameter,the concentration boundary layer becomes shorter,and the activation energy component increases the rate at which mass transfers come to the higher disk but have the opposite effect on the bottom disk.The ranges of various parameters taken into account are Pr=6.2,Re=2,M=1.0,φ_(1)=φ_(2)=0.03,K=0.5,S=-0.1,Br=0.3,Sc=2.0,α_(1)=0.2,γ=0.1,E_(n)=2.0,and q=1.0,and the rotation factor K is within the range of 0 to 1.

Transition from isotropic to polar state of self-driven eccentric disks

Inspired by the eccentricity design of self-driven disks,we propose a computational model to study the remarkable behavior of this kind of active matter via Langevin dynamics simulations.We pay attention to the effect of rotational friction coefficient and rotational noise on the phase behavior.A homogeneous system without rotational noise exhibits a sharp discontinuous transition of orientational order from an isotropic to a polar state with the increase of rotational friction coefficient.When there is rotational noise,the transition becomes continuous.The formation of polar state originates from the effective alignment effect due to the mutual coupling of the positional and orientational degrees of freedom of each disk.The rotational noise could weaken the alignment effect and cause the large spatial density inhomogeneity,while the translational noise homogenizes the system.Our model makes further conceptual progress on how the microscopic interaction among self-driven agents yields effective alignment.

使用Broadcast Disks方法分布的空中位图索引

提出一种使用BroadcastDisks算法来分布位图索引的空中索引方法,根据数据项访问概率,使用位图作为数据广播的索引,减少了移动终端等待数据时保持激活状态的时间,达到节能的目的。

REMARKS ON JOHN DISKS

Let D■R2 be a Jordan domain,D*=R2\D,the exterior of D.In this article,the authors obtained the following results:(1)If D is a John disk,then D is an outer linearly locally connected domain;(2)If D* is a John disk,then D is an inner linearly locally connected domain;(3)A homeomorphism f:R 2 →R 2 is a quasiconformal mapping if and only if f(D)is a John disk for any John disk D■R 2 ;and(4)If D is a bounded quasidisk,then D is a John disk,and there exists an unbounded quasidisk which is not a John disk.

An SPH simulation for cooling and self-gravitating protoplanetary disks

We investigate the effects of the cooling function in the formation of clumps of protoplanetary disks using two-dimensional smoothed particle hydrody- namic simulations. We use a simple prescription for the cooling rate of the flow, du/dt = -u/τcool, where u and %ool are the internal energy and cooling timeseale, respectively. We assume the ratio of local＇cooling to dynamical timescale, Ωτcool =β, to be a constant and also a function of the local temperature. We found that for the constantβ and γ = 5/3, fragmentation occurs only forβ ≤ 7. However, in the case ofβ having temperature dependence and γ = 5/3, fragmentation can also occur for larger values ofβ. By increasing the temperature dependence of the cooling timescale, the mass accretion rate decreases, the population of clumps/fragments increases, and the clumps/fragments can also form in the smaller radii. Moreover, we found that the clumps can form even in a low mass accretion rate, ≤10-7M⊙yr-1, in the case of temperature-dependentβ. However, clumps form with a larger mass accretion rate, 〉 10-7M⊙ yr-1, in the case of constantβ.

Low Co-Cultivation Temperature at 20°C Resulted in the Reproducible Maximum Increase in Both the Fresh Weight Yield and Stable Expression of GUS Activity after <i>Agrobacterium tumefaciens</i>-Mediated Transformation of Tobacco Leaf Disks

The importance of controlled temperature during the four-days co-cultivation period was evaluated under the most physiologically relevant conditions for Agrobacterium tumefaciens-mediated transformation of tobacco (Nicotiana tabacum L. cv. Xanthi (nn, Smith)) leaf disks. We compared the effect of temperatures ranging from 15°C, 18°C, 20°C, 22°C to 25°C on the stable expression of β-glucuronidase (GUS) activity of 14 days old hygromycin-selected leaf disks, and on the increase in the fresh weight yield of 28 days old kanamycin-selected calli. The highest average of GUS activity was obtained at 20°C among the five temperatures tested although the difference between the 18°C and 20°C treatment was not statistically significant. The GUS activity at 15°C was statistically lower than those at 18°C and 20°C. The GUS activity in 22°C treatment was an intermediate between the highest (18/20°C) and second highest averages (15°C), and was not statistically significantly different. The lowest average of GUS activity was observed at 25°C. The highest increase in the plate average of fresh weight yield was obtained at 20°C among the five temperature tested. The 20°C treatment was statistically significantly better than the 15°C and 18°C treatments. The 20°C co-cultivation treatment resulted in the higher FW yield than 22°C and 25°C even though the differences were not statistically significant. In conclusion, low co-cultivation temperature at 20°C resulted in the reproducible maximum increase in both the fresh weight yield and stable expression of GUS activity after transformation of tobacco leaf disks.

APPROXIMATION BY COMPLEX SZSZ-DURRMEYER OPERATORS IN COMPACT DISKS

In the present paper, we deal with the complex Szasz-Durrmeyer operators and study Voronovskaja type results with quantitative estimates for these operators attached to analytic functions of exponential growth on compact disks. Also, the exact order of approximation is found.

Numerical investigations of asymmetric flow of a micropolar fluid between two porous disks

Numerical solution is presented for the two- dimensional flow of a micropolar fluid between two porous coaxial disks of different permeability for a range of Reynolds number Re （-300≤ Re 〈 0） and permeability parameter A （1.0≤A ≤2.0）. The main flow is superimposed by the injection at the surfaces of the two disks. Von Karman＇s similarity transformations are used to reduce the governing equations of motion to a set of non-linear coupled ordinary differential equations （ODEs） in dimensionless form. An algorithm based on the finite difference method is employed to solve these ODEs and Richardson＇s extrapolation is used to obtain higher order accuracy. The results indicate that the parameters Re and A have a strong influence on the velocity and microrotation profiles, shear stresses at the disks and the position of the viscous/shear layer. The micropolar material constants cl, c2, c3 have profound effect on microrotation as compared to their effect on streamwise and axial velocity profiles. The results of micropolar fluids are compared with the results for Newtonian fluids.

Flow of a Second-Grade Fluid between Eccentric Rotating Porous Disks in the Presence of a Magnetic Field

This paper is concerned with the steady flow of a second-grade fluid between two porous disks rotating eccentrically under the effect of a magnetic field. A perturbation solution for the velocity field is presented under the assumption that the second-grade fluid parameter β is small. It is also studied the effect of all the parameters on the horizontal force per unit area exerted by the fluid on the disks. It is found that the x- and y-components of the force increase and decrease, respectively, when the second-grade fluid parameter β and the Hartmann number M increase. It is seen that the forces in the x- and y-directions on the top disk increase with the increase of the suction/injection velocity parameter P but those on the bottom disk decrease. It is shown that the force acting on the top disk is greater than that acting on the bottom disk in view of the axial velocity in the positive z-direction. It is observed that the increase in the Reynolds number R leads to a rise in the horizontal force.

Dust growth in protoplanetary disks-a comprehensive experimental / theoretical approach

More than a decade of dedicated experimental work on the collisional physics of protoplanetary dust has brought us to a point at which the growth of dust aggregates can - for the first time - be self-consistently and reliably modeled. In this article, the emergent collision model for protoplanetery dust aggregates, as well as the numerical model for the evolution of dust aggregates in protoplanetary disks, is reviewed. It turns out that, after a brief period of rapid collisional growth of fluffy dust aggregates to sizes of a few centimeters, the protoplanetary dust particles are subject to bouncing collisions, in which their porosity is considerably decreased. The model results also show that low-velocity fragmentation can reduce the final mass of the dust aggregates but that it does not trigger a new growth mode as discussed previously. According to the current stage of our model, the direct formation of kilometer-sized planetesimals by collisional sticking seems unlikely, implying that collective effects, such as the streaming instability and the gravitational instability in dust-enhanced regions of the protoplanetary disk, are the best candidates for the processes leading to planetesimals.

Jet precession in neutrino-cooled disks for gamma-ray bursts:The effects of the mass and spin of a black hole

We present a model of jet precession driven by a neutrino-cooled disk around a spinning black hole to explain the quasi-periodic features observed in some gamma-ray burst light curves. The different orientations of the rotational axes between the outer part of a neutrino-cooled disk and a black hole result in precessions of the central black hole and the inner part of the disk. Hence, the jet arising from the neutrino annihilation above the inner disk is driven to precession. We find that the period of precession is positively correlated with the mass as well as the spin of a black hole.

Flow and Melting Thermal Transfer Enhancement Analysis of Alumina,Titanium Oxide-Based Maxwell Nanofluid Flow Inside Double Rotating Disks with Finite-Element Simulation

The energy produced by the melting stretching disks surface has a wide range of commercial applications,including semi-conductor material preparation,magma solidification,permafrost melting,and frozen land refreezing,among others.In view of this,in the current communication we analyzed magnetohydrodynamic flow ofMaxwell nanofluid between two parallel rotating disks.Nanofluids are important due to their astonishing properties in heat conduction flows and in the enhancement of electronic and manufacturing devices.Furthermore,the distinct tinysized particles Al_(2)O_(3)and TiO_(2)in theMaxwell water-based fluid for enhancing the heat transfer rate are analyzed.The heat equation is developed in the occurrence of thermal radiation.The influences of melting impacts are incorporated.The mathematical model is developed in the form of partial differential expressions then converted to ordinary differential equations by employing tool of similarity variables.Finite element method(FEM)is chosen for solving the nonlinear governing ordinary differential equations(ODEs)with necessary conditions.The consequence of flow parameters against the velocity profiles and heat transport field is considered.The noted novelty of this communication is to discuss the thermal transfer of Maxwell nanofluid model through double stretching disks with thermal radiation and melting phenomenon.Further,Al_(2)O_(3)/water and TiO_(2)/water are considered in the modeling.

Nucleosynthesis in the accretion disks of Type Ⅱ collapsars

We investigate nucleosynthesis inside the gamma-ray burst （GRB） accre- tion disks formed by the Type II collapsars. In these collapsars, the core collapse of massive stars first leads to the formation of a proto-neutron star. After that, an out- ward moving shock triggers a successful supernova. However, the supernova ejecta lacks momentum and within a few seconds the newly formed neutron star gets trans- formed to a stellar mass black hole via massive fallback. The hydrodynamics of such an accretion disk formed from the fallback material of the supernova ejecta has been studied extensively in the past. We use these well-established hydrodynamic models for our accretion disk in order to understand nucleosynthesis, which is mainly ad- vection dominated in the outer regions. Neutrino cooling becomes important in the inner disk where the temperature and density are higher. The higher the accretion rate （M） is, the higher the density and temperature are in the disks. We deal with accre- tion disks with relatively low accretion rates： 0.001 Mo s-1 ~ 3）/~ 0.01 Mo S--1 and hence these disks are predominantly advection dominated. We use He-rich and Si- rich abundances as the initial condition of nucleosynthesis at the outer disk, and being equipped with the disk hydrodynamics and the nuclear network code, we study the abundance evolution as matter inflows and falls into the central object. We investigate the variation in the nucleosynthesis products in the disk with the change in the initial abundance at the outer disk and also with the change in the mass accretion rate. We report the synthesis of several unusual nuclei like 31p, 39K, 43Sc＇ 35C1 and various isotopes of titanium, vanadium, chromium, manganese and copper. We also confirm that isotopes of iron, cobalt, nickel, argon, calcium, sulphur and silicon get synthe- sized in the disk, as shown by previous authors. Much of these heavy elements thus synthesized are ejected from the disk via outflows and hence they should leave their signature in observed data.

Ice lines as the origin for the gap/ring structure in protoplanetary disks: the issue of the assumed temperature profile

Gaps and rings are commonly seen in recent high-resolution ALMA observations of protoplanetary disks. Ice lines of volatiles are one of the mechanisms proposed to explain the origin for these substructures. To examine the ice line hypothesis, literature studies usually parameterize the midplane temperature with the analytic formula of a passively heated, flared disk. The temperature in this simplified expression is basically dependent on the stellar luminosity. I have built a grid of self-consistent radiative transfer models that feature the same stellar properties, but different disk parameters. The midplane temperature of these models shows a large dispersion over a wide range of radii, indicating that besides the stellar luminosity, the disk parameters also play an important role in determining the thermal structure.Comparing the mid-plane temperature from radiative transfer simulation with the analytic solution shows a large difference between both approaches. This result suggests that special care on the assumed temperature profile has to be taken in the analysis of gap/ring origins, and conclusions drawn in previous works on the basis of the analytic temperature should be revisited. I further took the AS 209 disk as an example, and conducted a detailed radiative transfer modeling of the spectral energy distribution and the ALMA Band 6 image. The D137, D24 and D9 gaps are associated with the ice lines of major volatiles in the disk according to such a thorough analysis. However, if the temperature profile simply follows the analytic formula, none of these gaps matches the ice lines of the species considered here.

Approximation by Complex Baskakov-Szsz-Durrmeyer Operators in Compact Disks

In this paper, we deal with the complex Baskakov-Szasz-Durrmeyer mixed operators and study Voronovskaja type results with quantitative estimates for these operators attached to analytic functions of exponential growth in DR = {z ∈ C; ｜z｜ 〈 R}. Also, the exact order of approximation is found. The method used allows to construct complex Szasz-type and Baskakov-type approximation operators without involving the values on [0,∞）.

A WISE view of IRAS debris disks: revising the dust properties

Debris disks around stars are considered as components of planetary systems.Constraining the dust properties of these disks can give crucial information to formation and evolution of planetary systems.As an all-sky survey,InfRared Astronomical Satellite(IRAS)gave great contribution to the debris disk searching which discovered the first debris disk host star(Vega).The IRAS-detected debris disk sample published by Rhee(Rhee et al.2007)contains 146 stars with detailed information of dust properties.While the dust properties of 45 of them still cannot be determined due to the limitations with the IRAS database(have IRAS detection at 60μm only).Therefore,using more sensitivity data of Wide-.field Infrared Survey Explorer(WISE),we can better characterize the sample stars:for the stars with IRAS detection at 60μm only,we refit the excessive flux densities and obtain the dust temperatures and fractional luminosities;while for the remaining stars with multi-bands IRAS detections,the dust properties are revised which show that the dust temperatures were overestimated in the high temperature band before.Moreover,we identify 17 stars with excesses at the WISE 22μm which have smaller distribution of distance from Earth and higher fractional luminosities than the other stars without mid-infrared excess emission.Among them,15 stars can be found in previous works.

The density and temperature dependence of the cooling timescale for fragmentation of self-gravitating disks

The purpose of this paper is to explore the influences of cooling timescale on fragmentation of self-gravitating protoplanetary disks. We assume the cooling timescale, expressed in terms of the dynamical timescale Ω tcool, has a power-law dependence on temperature and density, Ω toool ∝∑-aT-b, where a and b are con- stants. We use this cooling timescale in a simple prescription for the cooling rate, du/dt = -u/tcoll, where u is the internal energy. We perform our simulations using the smoothed particle hydrodynamics method. The simulations demonstrate that the disk is very sensitive to the cooling timescale, which depends on density and tem- perature. Under such a cooling timescale, the disk becomes gravitationally unstable and clumps form in the disk. This property even occurs for cooling timescales which are much longer than the critical cooling timescale, Ω toool≥ 7. We show that by adding the dependence of a cooling timescale on temperature and density, the number of clumps increases and the clumps can also form at smaller radii. The simulations im- ply that the sensitivity of a cooling timescale to density is more than to temperature, because even for a small dependence of the cooling timescale on density, clumps can still form in the disk. However, when the cooling timescale has a large dependence on temperature, clumps form in the disk. We also consider the effects of artificial viscos- ity parameters on fragmentation conditions. This consideration is performed in two cases, where Ω tcool is a constant and Ω tcool is a function of density and temperature. The simulations consider both cases, and results show the artificial viscosity param- eters have rather similar effects. For example, using too small of values for linear and quadratic terms in artificial viscosity can suppress the gravitational instability and consequently the efficiency of the clump formation process decreases. This property is consistent with recent simulations of self-gravitating disks. We perform simulations with and without the Balsara form of artificial viscosity. We find that in the cooling and self-gravitating disks without the Balsara switch, the clumps can form more easily than those with the Balsara switch. Moreover, in both cases where the Balsara switch is present or absent, the simulations show that the cooling timescale strongly depends on density and temperature.

A numerical study of self-gravitating protoplanetary disks

The effect of self-gravity on protoplanetary disks is investigated.The mechanisms of angular momentum transport and energy dissipation are assumed to be the viscosity due to turbulence in the accretion disk.The energy equation is considered in a situation where the released energy by viscosity dissipation is balanced with cooling processes.The viscosity is obtained by equality of dissipation and cooling functions,and is used to derive the angular momentum equation.The cooling rate of the flow is calculated by a prescription,du/dt = u/τ cool,where u and τ cool are the internal energy and cooling timescale,respectively.The ratio of local cooling to dynamical timescales Ωτ cool is assumed to be a constant and also a function of the local temperature.The solutions for protoplanetary disks show that in the case of Ωτ cool = constant,the disk does not exhibit any gravitational instability over small radii for a typical mass accretion rate,˙ M = 10 6 M yr 1,but when choosing Ωτ cool to be a function of temperature,gravitational instability can occur for this value of mass accretion rate or even less in small radii.Also,by studying the viscosity parameter α,we find that the strength of turbulence in the inner part of self-gravitating protoplanetary disks is very low.These results are qualitatively consistent with direct numerical simulations of protoplanetary disks.Also,in the case of cooling with temperature dependence,the effect of physical parameters on the structure of the disk is investigated.These solutions demonstrate that disk thickness and the Toomre parameter decrease by adding the ratio of disk mass to central object mass.However,the disk thickness and the Toomre parameter increase by adding mass accretion rate.Furthermore,for typical input parameters such as mass accretion rate 10 6 M yr 1,the ratio of the specific heat γ = 5/3 and the ratio of disk mass to central object mass q = 0.1,gravitational instability can occur over the whole radius of the disk excluding the region very near the central object.

A possible origin of viscosity in Keplerian accretion disks due to secondary perturbation:Turbulent transport without magnetic fields

The origin of hydrodynamic turbulence in rotating shear flow is a long standing puzzle.Resolving it is especially important in astrophysics when the flow＇s angular momentum profile is Keplerian which forms an accretion disk having negligible molecular viscosity.Hence,any viscosity in such systems must be due to turbulence,arguably governed by magnetorotational instability,especially when temperature T ≥10 5.However,such disks around quiescent cataclysmic variables,protoplanetary and star-forming disks,and the outer regions of disks in active galactic nuclei are practically neutral in charge because of their low temperature,and thus are not expected to be coupled with magnetic fields enough to generate any transport due to the magnetorotational instability.This flow is similar to plane Couette flow including the Coriolis force,at least locally.What drives their turbulence and then transport,when such flows do not exhibit any unstable mode under linear hydrodynamic perturbation？ We demonstrate that the three-dimensional secondary disturbance to the primarily perturbed flow that triggers elliptical instability may generate significant turbulent viscosity in the range 0.0001 ≤νt≤ 0.1,which can explain transport in accretion flows.

The effects of viscosity on circumplanetary disks

The effects of viscosity on the circumplanetary disks residing in the vicinity of protoplanets are investigated through two-dimensional hydrodynamical simulations with the shearing sheet model. We find that viscosity can considerably affect properties of the circumplanetary disk when the mass of the protoplanet Mp ~ 33 Me, where Me is the Earth＇s mass. However, effects of viscosity on the circumplanetary disk are negligibly small when the mass of the protoplanet Mp 〉 33 Me. We find that when Mp ~ 33 Me, viscosity can markedly disrupt the spiral structure of the gas around the planet and smoothly distribute the gas, which weakens the torques exerted on the protoplanet. Thus, viscosity can slow the migration speed of a protoplanet. After including viscosity, the size of the circumplanetary disk can be decreased by a factor of 〉~ 20%. Viscosity helps to transport gas into the circumplanetary disk from the differentially rotating circumstellar disk. The mass of the circumplanetary disk can be increased by a factor of 50% after viscosity is taken into account when Mp ~ 33 Me. Effects of viscosity on the formation of planets and satellites are briefly discussed.