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Accretion discs around super-massive black holes (SMBH) not only power active galactic nuclei (AGNs), but also host single and binary embedded stellar-mass black holes (EBHs) that grow rapidly from gas accretion. The merger of these EBHs provides a promising mechanism for the excitation of some gravitational wave events observed by LIGO-Virgo, especially those with source masses considerably larger than isolated stellar-mass black hole binaries. In addition to their mass and mass-ratio distribution, their hitherto enigmatic small spin-parameters chi_effective carry important clues and stringent constraints on their formation channels and evolutionary pathways. Here we show that, between each coalescence, the typical rapid spin of the merged EBHs is suppressed by their subsequent accretion of gas from a turbulent environment, due to its ability to randomize the flow's spin orientation with respect to that of the EBHs on an eddy-turnover timescale. This theory provides supporting evidence for the prolificacy of EBH mergers and suggests that their mass growth may be dominated by gas accretion rather than their coalescence in AGN discs., accepted by MNRAS, 11 pages, 8 figures

The traditional paradigm of viscosity-dominated evolution of protoplanetary discs has been recently challenged by magnetized disc winds. However, distinguishing wind-driven and turbulence-driven accretion through observations has been difficult. In this study, we present a novel approach to identifying their separate contribution to angular momentum transport by studying the gap and ring morphology of planet-forming discs in the ALMA continuum. We model the gap-opening process of planets in discs with both viscous evolution and wind-driven accretion by 2D multi-fluid hydrodynamical simulations. Our results show that gap-opening planets in wind-driven accreting discs generate characteristic substructures that differ from those in purely viscous discs. Specifically, we demonstrate that discs, where wind-driven accretion dominates the production of substructures, exhibit significant asymmetries. Based on the diverse outputs of mock images in the ALMA continuum, we roughly divide the planet-induced features into four regimes (moderate-viscosity dominated, moderate-wind dominated, strong-wind dominated, inviscid). The classification of these regimes sets up a potential method to constrain the strength of magnetized disc wind and viscosity based on the observed gap and ring morphology. We discuss the asymmetry feature in our mock images and its potential manifestation in ALMA observations., Comment: 11 pages, 6 figures, accepted by MNRAS. Welcome any comments and suggestions!

We apply 3D hydrodynamical simulations to study the rotational aspect of gas flow patterns around eccentric companions embedded in an accretion disk around its primary host. We sample a wide range of companion mass ratio q and disk aspect ratio h, and confirm a generic transition from prograde (steady tidal interaction dominated) to retrograde (background Keplerian shear dominated) circum-companion flow when orbital eccentricity exceeds a critical value et. We find et \sim h for sub-thermal companions while et \sim (q/h)^1/3 for super-thermal companions, and propose an empirical formula to unify the two scenarios. Our results also suggest that et is insensitive to modest levels of turbulence, modeled in the form of a kinematic viscosity term. In the context of stellar-mass Black Holes (sBHs) embedded in AGN accretion disks, the bifurcation of their circum-stellar disk (CSD) rotation suggest the formation of a population of nearly anti-aligned sBHs, whose relevance to low spin gravitational waves (GW) events can be probed in more details with future population models of sBH evolution in AGN disks, making use of our quantitative scaling for et; In the context of circum-planetary disks (CPDs), our results suggest the possibility of forming retrograde satellites in-situ in retrograde CPDs around eccentric planets., Comment: Accepted to ApJL, 10 pages, 5 figures

We study the long-term radial transport of micron to mm-size grain in protostellar disks (PSDs) based on diffusion and viscosity coefficients measured from 3D global stratified-disk simulations with a Lagrangian hydrodynamic method. While gas-drag tend to transport dust species radially inwards, stochastic diffusion can spread a considerable fraction of dust radially outwards (upstream) depending on the nature of turbulence. In gravitationally unstable disks, we measure a high radial diffusion coefficient Dr with little dependence on altitude. This leads to strong and vertically homogeneous upstream diffusion in early PSDs. In the solar nebula, the robust upstream diffusion of micron to mm size grains not only efficiently transports highly refractory mocron-size grains (such as those identified in the samples of comet 81P/Wild 2) from their regions of formation inside the snow line out to the Kuiper Belt, but can also spread mm-size CAI formed in the stellar proximity to distances where they can be assimilated into chondritic meteorites. In disks dominated by magnetorotational instability (MRI), the upstream diffusion effect is generally milder, with a separating feature due to diffusion being stronger in the surface layer than the midplane. This variation becomes much more pronounced if we additionally consider a quiescent midplane with lower turbulence and larger characteristic dust size due to non-ideal MHD effects. This segregation scenario helps to account for dichotomy of two dust populations' spatial distribution as observed in scattered light and ALMA images., ApJ published, 14 pages, 12 figures

The tidal perturbation of embedded protoplanets on their natal disks has been widely attributed to be the cause of gap-ring structures in sub-mm images of protoplanetary disks around T Tauri stars. Numerical simulations of this process have been used to propose scalings of characteristic dust gap width/gap-ring distance with respect to planet mass. Applying such scalings to analyze observed gap samples yields a continuous mass distribution for a rich population of hypothetical planets in the range of several Earth to Jupiter masses. In contrast, the conventional core-accretion scenario of planet formation predicts a bi-modal mass function due to 1) the onset of runaway gas accretion above \sim20 Earth masses and 2) suppression of accretion induced by gap opening. Here we examine the dust disk response to the tidal perturbation of eccentric planets as a possible resolution of this paradox. Based on simulated gas and dust distributions, we show the gap-ring separation of Neptune-mass planets with small eccentricities might become comparable to that induced by Saturn-mass planets on circular orbits. This degeneracy may obliterate the discrepancy between the theoretical bi-modal mass distribution and the observed continuous gap width distribution. Despite damping due to planet-disk interaction, modest eccentricity may be sustained either in the outer regions of relatively thick disks or through resonant excitation among multiple super Earths. Moreover, the ring-like dust distribution induced by planets with small eccentricities is axisymmetric even in low viscosity environments, consistent with the paucity of vortices in ALMA images., 13 pages, 7 figures, ApJ in press

The prevalence of short-period super-Earths that are independent of host metallicity challenges the theoretical construction of their origin. We propose that dust trapping in the global pressure bump induced by magnetospheric truncation in evolved protoplanetary discs (PPDs) around T Tauri stars offers a promising formation mechanism for super-Earths, where the host metallicity is already established. To better understand this planet forming scenario, we construct a toy inner disc model and focus on the evolution of dust trapped in the bump, taking into account the supply from drifting pebbles and loss due to funnel flows. We develop an implicit coagulation-fragmentation code, $\mathtt{Rubble}$, and perform a suite of simulations to evolve the local dust size distributions. Our study for the first time considers dust feedback effect on turbulent diffusion in this kind of model. We report that efficient dust growth and significant accumulation of dust mass is possible in less turbulent disc with sturdier solids and with faster external supply, laying out a solid foundation for further growth towards planetesimals and planetary embryos. We further find that, depending on the dominant process, solid mass may predominantly accumulate in cm-sized grains or particles in runaway growth, indicating different ways of forming planetesimals. Furthermore, these various outcomes show different efficiencies in saving dust from funnel flows, suggesting that they may be distinguishable by constraining the opacity of funnel flows. Also, these diverse dust behaviours may help explain the observed dipper stars and rapidly varying shadows in PPDs., Comment: Accepted by MNRAS and in production; 20 pages, 14 figures

During their formation, emerging protoplanets tidally interact with their natal disks. Proto-gas-giant planets, with Hills radius larger than the disk thickness, open gaps and quench gas flow in the vicinity of their orbits. It is usually assumed that their type II migration is coupled to the viscous evolution of the disk. Although this hypothesis provides an explanation for the origin of close-in planets, it also encounter predicament on the retention of long-period orbits for most gas giant planets. Moreover, numerical simulations indicate that planets migrations are not solely determined by the viscous diffusion of their natal disk. Here we carry out a series of hydrodynamic simulations combined with analytic studies to examine the transition between different paradigms of type II migration. We find a range of planetary mass for which gas continues to flow through a severely depleted gap so that the surface density distribution in the disk region beyond the gap is maintained in a quasi-steady state. The associated gap profile modifies the location of corotation \& Lindblad resonances. In the proximity of the planet's orbit, high-order Lindblad \& corotation torque are weakened by the gas depletion in the gap while low-order Lindblad torques near the gap walls preserves their magnitude. Consequently, the intrinsic surface density distribution of the disk determines delicately both pace and direction of planets' type II migration. We show that this effect might stall the inward migration of giant planets and preserve them in disk regions where the surface density is steep., 21 pages, 12 figures, accepted by ApJ

We investigated how the stability of aqueous argon surface nanobubbles on hydrophobic surfaces depends on gas adsorption, solid-gas interaction energy, and the bulk gas concentration using molecular dynamics simulation with the SPC/E water solvent. We observed stable surface nanobubbles without surface pinning sites for longer than 160 ns, contrary to previous findings using monoatomic Lennard-Jones solvent. In addition, the hydrophobicity of a substrate has an effect to reduce the requirement degree of oversaturation on water bulk. We found that the gas enrichment layer, gas adsorption monolayer on the hydrophobic substrate, and water hydrogen bonding near the interface are likely necessary conditions for nanobubble stability. We concluded that gas nanobubble stability does not necessarily require three-phase pinning sites.

Recent studies indicate that changing the physical properties of lipid bilayers may profoundly change the function of membrane proteins. Here, the effects of dissolved nitrogen and oxygen molecules on the mechanical properties and stability of lipid bilayers are investigated using differential confocal microscopy, atomic force microscopy, and molecular dynamics simulations. All experiments evidence the presence of dissolved air gas in lipid bilayers prepared without gas control. The lipid bilayers in degassed solutions are softer and less stable than those in ambient solutions. High concentrations of nitrogen increase the bending moduli and stability of the lipid bilayers and impede phase separation in ternary lipid bilayers. The effect of oxygen is less prominent. Molecular dynamics simulations indicate that higher nitrogen affinity accounts for increased rigidity. These findings have fundamental and wide implications for phenomena related to lipid bilayers and cell membranes, including the origin of life.

This paper presents a novel design of multi dof and multifunctional manipulator arm control system. It uses 32 bit microcontroller STM32 as the core control unit, by controlling the pulse width modulation to control the manipulator arm of the steering gear. It consists of a mechanical model, the control core module, operation module, power supply module. The manipulator arm can greatly improve labor productivity, accelerate the realization of industrial production mechanization and automation, it can replace human labor in order to realize the mechanization and automation of production, and protect the personal safety in harmful environment. It has the advantages of light weight, simple operation, and low production cost etc.

In this paper, a kind of prevent drunk driving system is designed, which is based on the ARM9 core, alcohol detection module, GPS module, GSM module, voice module, LCD (Liquid Crystal Display), power and other functional modules are included in this new system. The system detect alcohol concentration, prevent drunk driving through the voice prompt and send text messages to a preset phone number. The system has absorbed the idea that most of the hardware functionality through software modular, so the circuit in the system is simple and that makes the system stability and accuracy greatly improved.

With the rapid development of science and technology, the current spectrum resources cannot simply cope with the high-load wireless networks cross-layer transmission. This thesis is based on the in-depth analysis of cognitive radio technology to understand the routing protocol in wireless cross-layer data transmission, and then discuss the relevant characteristics of the AODV routing protocol, and base on the AODV, the routing protocol uses in the analysis of the radio network organization based on the proposed to the possibility of cross-layer cognitive radio.

t is difficult to directly compress the raw data of synthetic aperture radar for its low relativity. In this paper, a new algorithm is put forward. Firstly range focusing is imposed to SAR raw data, which makes it have comparative high relativity, secondly a linear prediction is performed along the azimuth, lastly block adaptive quantization is used to the prediction difference series. The experiments manifest that with same bit rate, SQNR and SDNR of the algorithm proposed in this paper surpass that of BAQ algorithm. The calculation in this paper is far less than that of compression method after range focusing advised in corresponding reference. The algorithm proposed in this paper has a certain practical value.

A block adaptive scalar-vector quantization (BASVQ) algorithm is put forward in this paper, namely, scalar quantization is applied when data blocks satisfy Gaussian distribution while vector quantization is applied when doesnt satisfy. The experiments demonstrate that the performance of BASVQ algorithm surpasses that of BAQ algorithm. The BASVQ algorithm has practical value in some degree.

With the rapid development of science and technology, the current spectrum resources can not simply cope with the high-load wireless networks transmission. In addition, because the use of spectrum resources can not be fully maximize the overload load phenomenon, which leads to the waste of resources and loss of the spectrum, the existing overall spectrum resources are not adequate utilization and its utilization can not be improved. Obviously, in order to meet the growing demand for Internet and wireless communications, we must address the low rate of utilization of spectrum resources To this end, it is proposed to use the spectrum resources in cognitive radio drainage techniques, cognitive radio node to perceive the change of radio spectrum resources, and thus connected in the most appropriate timing and spectral integration, the effect of radio data transmission, and adequately addressed the problem of the spectrum resource low utilization. This thesis is based on the in-depth analysis of cognitive radio technology to understand the routing protocol in wireless cross-layer data transmission, and then discuss the relevant characteristics of the AODV routing protocol, and base on the AODV, the routing protocol uses in the analysis of the radio network organization based on the proposed to the possibility of cognitive radio.

It is difficult to directly compress the raw data of synthetic aperture radar for its low relativity. In this paper, a new algorithm is put forward. Firstly range focusing is imposed to SAR raw data, which makes it have comparative high relativity, secondly a linear prediction is performed along the azimuth, lastly block adaptive quantization is used to the prediction difference series. The experiments manifest that with same bit rate, SQNR and SDNR of the algorithm proposed in this paper surpass that of BAQ algorithm. The calculation in this paper is far less than that of compression method after range focusing advised in corresponding reference.

In this paper, we focus on joint channel estimation (JCE) of multi-cell networks, which is the basis for application of multi-cell cooperative. For overcoming the weakness that the existing multi-cell JCEs need power delay profile (PDP) knowledge of all multiple cells remained the same and known by receiver or pilot sequence sets of all cells being identical and other limitations, the paper presents a time domain correlation based JCE algorithm for multi-cell cooperative network when PDPs of multiple cells are not same and unknown and derives the corresponding Cramer-Rao bound (CRB). Then, by using Generalized Akaike Information Criterion (GAIC) to estimate PDPs of all cells for reducing the signal space of channel estimation, the paper further optimizes this JCE algorithm. Simulation results illustrate the proposed algorithms have good mean square error (MSE) performance, and corresponding space frequency block coded (SFBC) cooperative multi-cell transmission system have the good bit error rate (BER) performance too. 

Granular cell tumor is rare and accounts for approximately 0.5 % of all soft tissue tumors. The malignant granular cell tumor, especially cutaneous malignant granular cell tumor is extremely rare. The present case is the first patient of primary cutaneous malignant granular cell tumor reported from China in English. A review of the literature is performed, and the presentation, position, pathological diagnosis, treatment and prognosis of the patients with cutaneous malignant granular cell tumor of the reported cases before is analysed.

The block adaptive quantization (BAQ) algorithm is comparatively mature for SAR raw data compression at present. This algorithm is on the premise that SAR raw data should satisfy Gauss distribution. But the imaged region is quite rugged, some blocks of data doesn’t satisfy Gaussian distribution. Therefore, a block adative scalar-vector quantization (BASVQ) algorithm is put forward in this paper, namely, scalar quantization is applied when data blocks satisfy Gaussian distribution while vector quantization is applied when doesn’t satisfy. The experiments demonstrate that the performance of BASVQ algorithm outperforms that of BAQ algorithm. The BASVQ algorithm has practical value in some degree.

This paper, by exploiting characteristic function (CHF) and Beaulieu series, evaluates bit error rate (BER) of Orthogonal Frequency Division Multiplexing (OFDM) with Binary Phase Shift Keying (BPSK) modulation impaired by residual frequency and timing offsets over frequency selective Rayleigh fading channels. While it overcomes the limitation that the previous studies using the similar CHF approach can not calculate exact BER when OFDM has a large number of sub carriers. Simulation results illustrate the accuracy of the proposed analysis.