Flat Tail Research Articles

Fat Tails, Flat Tails, and Willingness to Pay

Fat Tails, Flat Tails, and Willingness to Pay

Equilibrium Taylor bubble in a narrow vertical tube with constriction

Equilibrium Taylor bubble in a narrow vertical tube with constriction

Study on Extending Range of Artillery Rocket Using Control Surfaces

Extension of range of artillery rocket using gliding technique is very effective way. Extension in the range is achieved by control surfaces without adding any extra charge. Controls are applied after completion of launch phase and trajectory is controlled by canards or flat tail control fins. Contribution in this work is to find the optimum time to initiate the controls during the flight so as to get maximum range. Analysis has been carried out using six degree of freedom equations of motion.

Ditching characteristics of civil aircraft with low-tail layout

Research focusing on the multi-phase coupling problem and ditching performance of a certain type of aircraft was carried out by the volume of fluid model and full-flow moving mesh method. Compared with the experimental results of the scaled model, the pressure predicted by this method matches well, and the maximum error of the pitch angle is less than 1.5°, which can accurately reflect the movement and load characteristics of the aircraft during ditching. On this basis, the influence of flat tails, flaps, and nacelles on the ditching performance is analyzed. The results show that it is not conducive to maintaining a stable attitude if the deflection of the flat tail is too slight, and the advance water-entry of flaps and nacelles will accelerate the decreasing process of pitch angle.

Some Morphofunctional Features of the Tail of Early Archosaurs in Relation to Swimming Adaptation

In ancient and modern aquatic and semi-aquatic tetrapods, several types of structure of the locomotor apparatus are presented, providing various styles of swimming. In the course of evolutionary adaptation to swimming, an important role was played by the morphological transformations of the tail, which often performs the main propulsion function. Modern reptiles (except turtles) swim mainly with the help of horizontal tail bends, while mammals swim either vertical or horizontal ones. Among extinct reptiles, Sauropterygia probably used vertical tail mobility when swimming. In most archosauromorphs, the tail became high, laterally compressed, and they swam mainly with the help of its horizontal movements. Among early archosaurs, Proterohampsians and Doswelliids are distinguished by their wide and dorsoventrally flat tails, which may indicate an adaptation to swimming using its vertical mobility.

ALMA-IMF

Context.Among the most central open questions regarding the initial mass function (IMF) of stars is the impact of environment on the shape of the core mass function (CMF) and thus potentially on the IMF.Aims.The ALMA-IMF Large Program aims to investigate the variations in the core distributions (CMF and mass segregation) with cloud characteristics, such as the density and kinematic of the gas, as diagnostic observables of the formation process and evolution of clouds. The present study focuses on the W43-MM2&MM3 mini-starburst, whose CMF has recently been found to be top-heavy with respect to the Salpeter slope of the canonical IMF.Methods.W43-MM2&MM3 is a useful test case for environmental studies because it harbors a rich cluster that contains a statistically significant number of cores (specifically, 205 cores), which was previously characterized in Paper III. We applied a multi-scale decomposition technique to the ALMA 1.3 mm and 3 mm continuum images of W43-MM2&MM3 to define six subregions, each 0.5–1 pc in size. For each subregion we characterized the probability distribution function of the high column density gas,η-PDF, using the 1.3 mm images. Using the core catalog, we investigate correlations between the CMF and cloud and core properties, such as theη-PDF and the core mass segregation.Results.We classify the W43-MM2&MM3 subregions into different stages of evolution, from quiescent to burst to post-burst, based on the surface number density of cores, number of outflows, and ultra-compact HII presence. The high-mass end (>1M⊙) of the subregion CMFs varies from close to the Salpeter slope (quiescent) to top-heavy (burst and post-burst). Moreover, the second tail of theη-PDF varies from steep (quiescent) to flat (burst and post-burst), as observed for high-mass star-forming clouds. We find that subregions with flat secondη-PDF tails display top-heavy CMFs.Conclusions.In dynamical environments such as W43-MM2&MM3, the high-mass end of the CMF appears to be rooted in the cloud structure, which is at high column density and surrounds cores. This connection stems from the fact that cores and their immediate surroundings are both determined and shaped by the cloud formation process, the current evolutionary state of the cloud, and, more broadly, the star formation history. The CMF may evolve from Salpeter to top-heavy throughout the star formation process from the quiescent to the burst phase. This scenario raises the question of if the CMF might revert again to Salpeter as the cloud approaches the end of its star formation stage, a hypothesis that remains to be tested.

Analysis of Aircraft Parking Stability Based on Atmosphere Boundary Theory

Based on numerical simulation technology, the aerodynamic load research of civil aircraft parked on the ground is conducted. The CRM model parked on the ground is established by CFD software. Based on the atmospheric boundary layer theory, the seven incoming flow conditions for numerical calculation are designed. And the aerodynamic loads’ change of the aircraft model is calculated when the -90° sideslip angle. The result shows that the mooring load on the nose landing gear mainly comes from the longitudinal load caused by the upwards pitching moment on the flat tail and the lateral load caused by the yaw moment; since the rolling moment coefficient is less than the pitching moment coefficient by two orders of magnitude, which hardly affects the mooring load. The study provides a reference for reducing the mooring load of civil aircraft under heavy wind conditions.

The Influence of Rotor Overlapping Azimuth on Compound Coaxial Helicopter Performance Based on Unsteady CFD Simulation

In this paper, a computational fluid dynamics simulation method is developed to study the influence of the rotor overlapping azimuth on the aerodynamic performance of compound coaxial helicopter. The simulation method is verified by comparing the numerical simulation results with the wind tunnel experiment data of the NASA coaxial rotor. Two overlapping azimuths of the upper and lower blades are considered, and the aerodynamic performance of the isolated rotor and the compound coaxial helicopter in hover and forward are analyzed respectively. State 1 means the upper and lower blades overlap at azimuth 0/180° or 90/270°, state 2 means the upper and lower blades overlap at azimuth 45/225° or 135/315°. It is found that the performance of isolated rotors is not affected by rotor overlapping azimuth in hover, but the total thrust fluctuation amplitude of isolated rotors in state 2 is 76.3% smaller than that in state 1 in forward. In the hovering flight of compound coaxial helicopter, compared with state 1, the fluctuation amplitude of the lift of the wing in state 2 is 42.7% smaller; the lift fluctuation amplitude of the flat tail in state 2 is 52.4% smaller. In the forward flight of compound coaxial helicopter, compared with state 1, the total thrust fluctuation amplitude in state 2 is 83.5% smaller; the fluctuation amplitude of the lift of the wing in state 2 is 61.2% smaller. It can be concluded that the compound coaxial helicopter working in state 2 has better aerodynamic performance than the compound coaxial helicopter working in state 1; changing the rotor overlapping azimuth of the upper and lower rotors has a high engineering application value, which can increase aerodynamic stability and reduce lift fluctuations.

LAMOST meets Gaia: The Galactic open clusters

Open clusters (OCs) are born and evolve along the Milky Way (MW) plane. On them is imprinted the history of the Galactic disc, including its chemical and dynamical evolution. Chemical and dynamical properties of OCs can be derived from photometric, spectroscopic, and astrometric data of their member stars. Based on the photometric and astrometric data from the Gaia mission, the membership of stars in more than two thousand Galactic clusters has been identified in the literature. The chemical properties (e.g. metallicity) and kinematical properties (e.g. radial velocity), however, are still poorly known for many of these clusters. In synergy with the large spectroscopic survey LAMOST (data release 8) and Gaia (data release 2), we report a new comprehensive catalogue of 386 OCs. This catalogue has homogeneous parameter determinations of radial velocity, metallicity, and dynamical properties, such as orbit, eccentricity, angular momenta, total energy, and 3D Galactic velocity. These parameters enable the first radial velocity determination for 44 clusters, and the first spectroscopic [Fe/H] determination for 137 clusters. The metallicity distributions of the majority of clusters show falling trends in the parameter space of the Galactocentric radius, the total energy, and the Z component of angular momentum, except for two old groups that show flat tails in their own parameter planes. Cluster populations of ages younger and older than 500 Myr distribute diversely on the disc. The latter have a spatial consistency with the Galactic disc flare. The 3D spatial comparison between very young clusters (< 100 Myr) and nearby molecular clouds revealed a wide range of metallicity distribution along the Radcliffe gas cloud wave, indicating a possible inhomogeneous mixing or fast star formation along the wave. This catalogue will serve the community as a useful tool to trace the chemical and dynamical evolution of the MW.

Nearly optimal Bayesian shrinkage for high-dimensional regression

During the past decade, shrinkage priors have received much attention in Bayesian analysis of high-dimensional data. This paper establishes the posterior consistency for high-dimensional linear regression with a class of shrinkage priors, which has a heavy and flat tail and allocates a sufficiently large probability mass in a very small neighborhood of zero. While enjoying its efficiency in posterior simulations, the shrinkage prior can lead to a nearly optimal posterior contraction rate and the variable selection consistency as the spike-and-slab prior. Our numerical results show that under the posterior consistency, Bayesian methods can yield much better results in variable selection than the regularization methods such as LASSO and SCAD. This paper also establishes a BvM-type result, which leads to a convenient way of uncertainty quantification for regression coefficient estimates.

Study on Flat Tail Stall Characteristics of Aircraft

Study on Flat Tail Stall Characteristics of Aircraft

ANALISIS PENDAPATAN DAN PROFITABILITAS PADA PETERNAKAN SAPI PERAH SUMBER MULYA DI KABUPATEN KEPAHIANG

ABSTRACT The study was purposed to find out income and profitability was achieved by a Sumber Mulya dairy farm. Research was held in July – Agust 2018 in Sumber Mulya dairy farm Kepahiang. The methods used in this research is case study method. Primary Data obtained through interviews with the respondents and recording. Data obtained for time 12 months on technical aspects and financial data covering production costs, data revenue, income data, the amount of data the data the amount of milk production and livestock lactation. Secondary data retrieved from the data contained in these farms. Data analysis used analysis formulas use income and profitability ratios. The result showed that Sumber Mulya Dairy cattle farm was net incomeaverages per month is Rp. 5,427,176,91 with the number of 7.00 averagecows lactation flat tail. Total cost per month of Rp.10,032,823.29 Profitability achieved by the company said 10,78% profitable because the value of profitability is greater than the interest rate a bank of 4.35%. Key word : income, dairy farm, profitability, dairy farm, milk production

Description of Ektaphelenchus masseyi n. sp. (Rhabditida: Ektaphelenchinae) found in dead wood, from Iran

Summary Ektaphelenchus masseyi n. sp. is described and illustrated. The new species was isolated from dead/rotten wood collected from natural forests in north Iran. It is characterised by 501-758 μm long females having three lines in lateral field, more or less continuous cephalic region separated from the body only by a shallow depression, relatively short tripartite stylet (total length 13-14 μm) lacking basal knobs or swellings, excretory pore at base of metacorpus or slightly anterior to it, post-vulval uterine sac 24-32 μm long, rectum and anus absent, posterior body region conical with finely rounded terminus, and males rare, with a dorsally convex and ventrally flat tail with a small mucron at terminus, 13-15 μm long spicules, and seven caudal papillae. The new species was morphologically compared with typologically similar species of Ektaphelenchus having three lines in the lateral field, namely E. joyceae, E. macrobulbosus, E. taiwanensis, and E. winteri. It was further compared with E. olitorius and E. prolobos having a similar female posterior body end shape and with an unknown number of incisures in the lateral field. It was also compared with three species currently placed under Ektaphelenchoides, namely E. andrassyi and E. poinari with three lines in the lateral field, and E. compsi with obscure lateral lines. The molecular phylogenetic relationships of the new species with other ektaphelenchid species were investigated using partial small, and large subunit ribosomal RNA gene (SSU and LSU rDNA D2-D3) sequences using the maximal number of currently sequenced ektaphelenchid and seinurid taxa.

Surficial geochemistry and bioaccessibility of tellurium in semiarid mine tailings

Environmental contextTellurium can be more toxic than arsenic, but its fate in the surficial environment is poorly understood. We studied tellurium behaviour in semiarid mine tailings and found that most tellurium is associated with iron (oxy)hydroxides as tellurate (TeVI), the less toxic oxidation state. Iron (oxy)hydroxides are likely to control the fate of Te in the surficial environment and may effectively sequester Te oxyanions released by oxidative weathering. AbstractTellurium (Te) is a critical element owing to its use in solar technology. However, some forms are highly toxic. Few studies have examined Te behaviour in the surficial environment, thus little is known about its potential human and environmental health impacts. This study characterises two physicochemically distinct Te-enriched mine tailings piles (big and flat tailings) deposited by historic gold (Au) mining in the semiarid Delamar mining district, Nevada, USA. The big tailings are characterised by smaller particle size and higher concentrations of potentially toxic elements (up to 290mgTekg−1), which are enriched at the tailings surface. In contrast, the flat tailings have larger particle size and properties that are relatively invariant with depth. Based on the sulfate to sulfide ratio, the tailings were determined to be sulfate dominated, which suggested a high degree of weathering, although the flat tailings did contain significant amounts of sulfides (~40%). Tellurium X-ray absorption spectroscopy of the big tailings indicates that tellurate, the less toxic Te species, is the principal form of Te. Electron microscopy indicates that most of the Te present at the site is associated with iron (oxy)hydroxides, and sometimes with other potentially toxic elements, especially lead and antimony. Physiologically-based extraction tests indicate that substantially more Te is solubilised in synthetic stomach fluids than in lung fluids, with gastric bioaccessibility ranging from 13 to 31% of total Te. This points to low to medium bioaccessibility, which is common for iron (oxy)hydroxide-associated elements. Together, these results represent a preliminary assessment of Te surficial behaviour in a semiarid environment and indicate that Te in these tailings represent a moderate health concern.

Study on the High-Speed and Close of the UVA Cooperative Formation Controller Design

Aiming at the high-speed flight of the UAVs cooperative formation, when a single UAV has occurred, need to exit the formation flight and be close or super close to form of the formation quickly. A fast close cooperative formation controller design method is proposed to make up for low the fighting robustness, and be shortcomings of timeliness poorly and analyze the dynamic characteristic of UAV formation flight. Taking the external factors known into consideration, setting up for the longitude maneuver of nonlinear thrust vector and unsteady aerodynamic model, according to the formation velocity, flat tail rudder angle and thrust vector and pitch angle velocity for corresponding input commend signals for the controller to research the dynamic characteristic of UAV formation flight. Meanwhile, the formation flight distance error is the convergence to a fixed value, and the stability of the cooperative formation flight is good. The simulation of results show that the controller can effectively improve the speed of the close or super close to formation, and maintain the stability of the formation flight, which provides a method of the close or super close formation flight controller design.

Production Pressure-Drawdown Management for Fractured Horizontal Shale Gas Wells

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 181365, “Production Pressure-Drawdown Management for Fractured Horizontal Wells in Shale Gas Formations,” by Ankit Mirani, University of Houston; Matteo Marongiu-Porcu, SPE, Schlumberger; HanYi Wang, SPE, The University of Texas at Austin; and Philippe Enkababian, SPE, Schlumberger, prepared for the 2016 SPE Annual Technical Conference and Exhibition, Dubai, 26–28 September. The paper has not been peer reviewed. The primary objective of this study is to address all known causes of productivity declines in unconventional shale gas formations with horizontal multifractured wells and to develop a fully coupled geomechanical/flow simulation model to simulate these production conditions. The model mimics the effect of depletion-induced in-situ stress variations on productivity by taking into account several phenomena, such as stress-dependent matrix and natural-fracture permeability and reduction in fracture conductivity because of fracture-face creep and proppant crushing, deformation, and embedment. Model Formulation Reservoir Matrix. The gas-storage mechanism in a shale gas reservoir is conceptually different from that of a conventional reservoir. Natural gas is adsorbed on the organic matter present in shales and, in some cases, on certain clay minerals. This adsorbed-gas layer further constricts the area for flow through the pore structure, thus reducing the effective pore radius. As the pressure in the pores reduces, gas is desorbed and the effective pore radius increases, resulting in an increase in the apparent matrix permeability. It has been suggested that desorption of methane might be partially responsible for the relatively long and flat production tails that have been observed in some shale reservoirs. Fig. 1 shows the effects of different mechanisms on permeability evolution. Clearly, shale gas long-term performance forecasting will be affected severely if these effects are not properly considered. Hydraulic Fractures. Hydraulic fractures are generally kept open and conductive by proppant. After exposure to confining stress for a long period of time, proppant can become deformed, causing degradation of its mechanical and physical properties. This leads to reductions in fracture width and fracture-pack permeability because of intermixing and plugging. Additionally, the interaction between the proppant and fracture surfaces under the same confining stress can result in embedment, decreasing the fracture aperture and impairing conductivity.

Three-dimensional hydrodynamical CO5BOLD model atmospheres of red giant stars

Although observational data unequivocally point out to the presence of chromospheres in red giant stars, no attempts have been made so far to model them using 3D hydrodynamical model atmospheres. We therefore compute an exploratory 3D hydrodynamical model atmosphere for a cool red giant in order to study the dynamical and thermodynamic properties of its chromosphere, as well as the influence of the chromosphere on its observable properties. 3D radiation hydrodynamics simulations are carried out with the CO5BOLD model atmosphere code for a star with the atmospheric parameters (Teff=4010 K, log g=1.5, [M/H]=0.0), which are similar to those of the K-type giant star Aldebaran (alpha Tau). ... we compute the emergent continuum intensity maps at different wavelengths, spectral line profiles of Ca II K, the Ca II infrared triplet line at 854.2nm, and H alpha, as well as the spectral energy distribution (SED) of the emergent radiative flux. The initial model quickly develops a dynamical chromosphere characterised by propagating and interacting shock waves. The peak temperatures in the chromospheric shock fronts reach values on the order of up to 5000 K although the shock fronts remain quite narrow. Like for the Sun, the gas temperature distribution in the upper layers is composed of a cool component due to adiabatic cooling in the expanding post-shock regions and a hot component due to shock waves. For this red giant model, the hot component is a rather flat high-temperature tail, which nevertheless affects the resulting average temperatures significantly. The simulations show that the atmospheres of red giant stars are dynamic and intermittent. Consequently, many observable properties cannot be reproduced with one-dimensional static models but demand for advanced 3D HD modelling. Furthermore, including a chromosphere in the models might produce significant contributions to the emergent UV flux.

Statistical analysis of some main geomechanical formulations evaluated with the Kaniadakis exponential law

ABSTRACTThe following paper reviews four well-known geomechanical equations, i.e. the elastic modulus of the rock mass as function of the Rock Mass Rating (RMR) system, the relation between Rock Quality Designation (RQD) and spacing distribution of the natural discontinuities in the rock mass, the distribution of the discontinuity spacing along a straight line for a rock mass and the intact rock strength in function of the specimen diameter by using a power-law flat tails equation based on the theory of Kaniadakis. The results show that by using novel formulations, the experimental data are better approximated by the power-law flat tails statistical approach, which shows a trend similar to ordinary exponential for a certain part of the interval of variability of x; the tails, however, follow the power law for extreme values of x. It was, therefore, possible to obtain new formulations able to better represent some fundamental aspects of geomechanics.

Backflows by active galactic nuclei jets: global properties and influence on supermassive black hole accretion

Jets from Active Galactic Nuclei (AGN) inflate large cavities in the hot gas environment around galaxies and galaxy clusters. The large-scale gas circulation promoted within such cavities by the jet itself gives rise to backflows that propagate back to the center of the jet-cocoon system, spanning all the physical scales relevant for the AGN. Using an Adaptive Mesh Refinement code, we study these backflows through a series of numerical experiments, aiming at understanding how their global properties depend on jet parameters. We are able to characterize their mass flux down to a scale of a few kiloparsecs to about $0.5\,\mathrm{M_\odot/y}$for as long as $15$ or $20$ Myr, depending on jet power. We find that backflows are both spatially coherent and temporally textbf{intermittent}, independently of jet power in the range $10^{43-45}$ erg/s. Using the mass flux thus measured, we model analytically the effect of backflows on the central accretion region, where a Magnetically Arrested Disk lies at the center of a thin circumnuclear disk. Backflow accretion onto the disk modifies its density profile, producing a flat core and tail. We use this analytic model to predict how accretion beyond the BH magnetopause is modified, and thus how the jet power is temporally modulated. Under the assumption that the magnetic flux stays frozen in the accreting matter, and that the jets are always launched via the Blandford-Znajek (1977) mechanism, we find that backflows are capable of boosting the jet power up to tenfold during relatively short time episodes (a few Myr).

翼身融合体飞机气动外形设计及分析

本文根据以往翼身融合体飞机的一些设计经验，设计了一种翼身融合体飞机气动外形，并研究分析了翼身融合体飞机初始模型在不同风速和迎角的情况下的气动特性。利用CATIA生成翼身融合体飞机初始模型，由于考虑到该型飞机的具体尺寸、选用翼型以及制作重量，所以飞机的巡航速度设计为30 m/s，通过风洞实验和FLUENT计算流体力学软件计算得出初始翼身融合体飞机模型的速度云图和压力云图以及初始模型飞机周围流场分布情况，然后根据FLUENT计算流体力学软件得出的初始模型流场分布情况，确定4种在初始模型基础上经过改进的模型，分别为涡流器模型、翼梢小翼模型、鸭翼模型、平尾模型，研究经过改进的4个模型气动特性(包括升力系数，阻力系数，升阻比)随速度和迎角的影响的思路是：建立精确的改进涡流器模型、改进翼梢小翼模型、改进鸭翼模型、改进平尾模型，利用CFD计算流体力学软件计算在不同风速迎角分别从−4˚到14˚下飞机的气动特性，并分析在不同速度和迎角下的飞机的气动特性随迎角的变化规律，为今后翼身融合飞机的安全高效飞行提供理论依据。并对改进的4种模型在不同速度和迎角下的升阻比等气动特性与初始模型进行对比，再根据不同的改进模型在不同飞行状态下所具有的气动特性探讨其改进模型的用途及其发展价值。 This article based on the design experience of wing body fusion aircraft before designed a wing body fusion aircraft aerodynamic shape, and analyzed initial model of the wing fusion aircraft with different wind speed and angle of attack. In the process of research, CATIA was used to generate the initial model of wing body fusion aircraft. Taking into account the specific size of the aircraft, the choice of airfoil and for weight, the cruise speed of the aircraft is designed to be 30 m/s. Through the wind tunnel experiment and FLUENT computational fluid dynamics soft-ware calculations, we can get the initial model of wing fusion aircrafts speed cloud and pressure cloud and the distribution of the surrounding flow field. On the basis of FLUENT computational fluid dynamics software and the distribution of the surrounding flow field, four improved models based on the initial model were identified: Eddy swirl model, wingtip winglet model, canyon model, and flat tail model. This paper researched the aerodynamic performance of the four improved wing-body fusion aircraft models at different angles of attack and wind speed (including lift coefficient, drag coefficient, lift drag ratio). The idea of the impact is to establish an accurate improved swirl model, to improve the wing winglet model, to improve the duck wing model, to improve the flat tail model. The research has used CFD to calculate the aerody-namic characteristics of the airplane at different wind of angles at −4˚ to 14˚, and analyzed the aerodynamic characteristics of the aircraft at different speeds and angles of attack. It can pro-vide a theoretical basis for the safe and efficient flight of the aircraft. This research compared the aerodynamic characteristics of the improved four models with the initial model at different speeds and angles of attack. And then it used the aerodynamic characteristics of different im-proved models under different flight states to explore the use of the improved model and its development value.