Influence of aspect ratio, plasma viscosity, and radial position of the resonant surfaces on the plasmoid formation in the low resistivity plasma in Tokamak

In the present paper, we systematically investigate the nonlinear evolution of the resistive kink mode in the low resistivity plasma in Tokamak geometry. We find that the aspect ratio of the initial equilibrium can significantly influence the critical resistivity for plasmoid formation. With the aspect ratio of 3/1, the critical resistivity can be one magnitude larger than that in cylindrical geometry due to the strong mode-mode coupling. We also find that the critical resistivity for plasmoid formation decreases with increasing plasma viscosity in the moderately low resistivity regime. Due to the geometry of Tokamaks, the critical resistivity for plasmoid formation increases with the increasing radial location of the resonant surface.

Inorganic Elements of Mangium Stem (Acacia mangium Willd) from Different Provenanc

This study aimed to investigate the ash content and concentrations of inorganic elements present in the stem of Acacia mangium. The tree samples (24 years) were collected from five different provenances (Sidei, West of Morehead, Daintree, Ellerbeck, and El Arish). Meanwhile, the disc samples were obtained from the trunk of each tree on the lower parts. The samples were collected from four radial positions (bark, sapwood, outer heartwood, inner heartwood), and the ash and insoluble acid contents were determined. Furthermore, the concentration of 5 elements (Ca, Mg, Fe, Mn, K, and Na) was measured by Atomic Absorption Spectrophotometry (AAS). The interaction of provenance and radial position factors affected ash and potassium contents. Also, acid insoluble ash and calcium contents showed a provenance factor effect. The barks obtained from the tree samples contained the highest concentrations of ash content and most of the elements. The wood and bark of El-Arish provenance showed the lowest (0.50~0.72%) and highest levels (4.75%) of ash content respectively. Furthermore, the highest amount of insoluble acid ash (3075 ppm) and calcium (4513 ppm) content was also measured in samples of El-Arish provenance, and radial position factor was a significant source of variation for Ca, Mg, Na, and Mn concentrations. Except Mg, the inner and outer portions of the heartwood mostly showed no significant difference in unprecedented element concentrations. Ash content was positively correlated with Ca in sapwood (r=0.39) and Mn in bark (r=0.54). In addition, moderate correlations were observed between Mg and Ca in heartwood (r=0.63) and bark (r=0.54) tissues. For ash and silica content, the comparatively low concentration on samples from El-Arish provenance are good options to improve wood quality for breeding programs.

PROPERTIES OF TEAK WOOD INFECTED BY Ceratocystis fimbriata

In Brazil, the growth of Tectona grandis (teak) plantations is accompanied by an increased incidence of Ceratocystis wilt, a fungal disease that colonizes the vascular system of such tree. The objective of this work was to evaluate the properties of teak wood infected with Ceratocystis fimbriata at different radial positions. Ten 17-year-old trees (five infected and five healthy) were collected. A disk was removed from the base of each tree to determine Janka hardness, basic density, anatomical analysis, colorimetric parameters in the CIEL*a*b* system and sodium hydroxide solubility (NaOH). There were no significant differences for radial position and health for basic density and Janka hardness of the wood, with mean values of 0.488 g.cm3 and 58.66 MPa, respectively. The deposition of dark compounds was observed inside the parenchyma cells and fibers, as well as the formation of tyloses in the sapwood. Yellow pigment was predominant in the color formation of teak wood, which was influenced by radial position, with the sapwood being lighter. Regarding C. fimbriata infection, the color change was more evident in sapwood. Conversely, the NaOH solubility was lower for the sapwood attacked by the fungus. In conclusion, the changes in teak wood infected by C. fimbriata are visual and the anatomical structures do not deteriorate.

Spatial distribution of the X-ray-emitting plasma of SS Cygni in quiescence and outburst

We present our analysis of the Suzaku data of SS Cygni (SS Cyg) from 2005 both in quiescence and outburst. A fluorescent iron Kα line bears significant information about the geometry of an X-ray-emitting hot plasma and a cold reflector, such as the surfaces of the white dwarf (WD) and the accretion disk (AD). Our reflection simulation has revealed that the X-ray-emitting hot plasma is located either very close to the WD surface in the boundary layer (BL), with an upper limit radial position of <1.004 times the white dwarf radius (RWD), or near the entrance of the BL where the optically thick AD is truncated at a distance of 1.14–1.27 RWD for the assumed WD mass of 1.19 M⊙ in quiescence. In the latter configuration, the plasma torus is located just above the inner edge of the AD. The result suggests that the accreting matter is heated up close to the maximum temperature immediately after the matter enters the BL. The matter probably expands precipitously at the entrance of the BL and leaves the disk plane to reach a height comparable to the radial distance of the plasma torus from the center of the WD. In outburst, on the other hand, our spectral analysis favors the picture that the optically thick disk reaches the WD surface. In addition, the plasma distributes above the disk like coronae, as suggested by a previous study, and the 90% upper limit of the coronae radial position is 1.2 RWD.

A Novel Driving Scheme for Three-Phase Bearingless Induction Machine with Split Winding

In order to reduce the costs of implementing the radial position control system of a three-phase bearingless machine with split winding, this article proposes a driving method that uses only two phases of the system instead of the three-phase traditional one. It reduces from six to four the number of inverter legs, drivers, sensors, and current controllers necessary to drive and control the system. To justify the proposal, this new power and control configuration was applied to a 250 W machine controlled by a digital signal processor (DSP). The results obtained demonstrated that it is possible to carry out the radial position control through two phases, without loss of performance in relation to the conventional three-phase drive and control system.

Investigating the Influence of Impeller Axial Thrust Balance Holes On the Flow and Overall Performance of a Cryogenic Liquid Turbine Expander

An excessive rotor axial thrust in any turbomachine can cause critical operational problems, and rotor axial thrust balancing has always attracted much attention. The present numerical study is focused on axial thrust balancing for a cryogenic liquid turbine expander, whose axial thrust balancing is typically challenging because of its small impeller size and large axial thrust. A computational fluid dynamics (CFD) simulation is conducted in a real turbine expander environment constituted by main and gap flow domains with allowing for the thermodynamic effect of liquefied air. The balance hole influential mechanism on the main and gap flows is explored, and its influence on the expander axial thrust and overall performance is quantified. The results show that the use of balance holes creates a highly swirling gap flow, and the static pressure over the impeller disk back-side surface decreases to produce a small axial component force and axial thrust, but the turbine expander overall efficiency drops by 1.1 and 2.8 points at 100% and 50% design flow, respectively, due to an increased internal leakage loss and distorted impeller flow. In addition, a parametric study is conducted to analyze the effect of balance hole diameter, circumferential position and radial position on expander axial thrust and overall performance. The results indicate that the axial thrust is sensitive to both the balance hole diameter and circumferential position but less sensitive to its radial position, while the overall efficiency is influenced by all three parameters.

A substrate for brane shells from $$ T\overline{T} $$

A solvable current-current deformation of the worldsheet theory of strings on AdS3 has been recently conjectured to be dual to an irrelevant deformation of the spacetime orbifold CFT, commonly referred to as single-trace $$ T\overline{T} $$ T T ¯ . These deformations give rise to a family of bulk geometries which realize a non-trivial flow towards the UV. For a particular sign of this deformation, the corresponding three-dimensional geometry approaches AdS3 in the interior, but has a curvature singularity at finite radius, beyond which there are closed timelike curves. It has been suggested that this singularity is due to the presence of “negative branes,” which are exotic objects that generically change the metric signature. We propose an alternative UV-completion for geometries displaying a similar singular behavior by cutting and gluing to a regular background which approaches a linear dilaton vacuum in the UV. In the S-dual picture, a singularity resolution mechanism known as the enhançon induces this transition by the formation of a shell of D5-branes at a fixed radial position near the singularity. The solutions involving negative branes gain a new interpretation in this context.

Systematic biases in the on-board navigation solution of a CubeSat GNSS payload board

<p>In December 2018 and April 2019, two 3-unit cube satellites of the company Astrocast were launched into orbit. Both satellites are equipped with our low-cost single-frequency multi-GNSS payload board, which provides almost continuous on-board receiver solutions containing the position from GNSS code observations and the velocity from Doppler measurements. We make use of these independent observation types (positions and velocities) to identify and analyse systematic biases in the receiver solution. Therefore, we estimate the parameters of a dynamic orbit model using three different approaches: fitting the orbit model (1) to the positions only, (2) to the velocities only and (3) to both, positions and velocities.</p><p>After removing outliers, the position residuals from the position-only approach are at a level of about 5 m, the velocity residuals from the velocity-only approach at about 15 cm/s. When computing the positions with the velocity-only approach, however, the residuals are much larger and show a once-per revolution periodicity with amplitudes of up to 40 m. Besides that, we identify two offsets in the residuals which are independent of the observation type: a radial position bias of -3 m and an along-track velocity bias of -1.2 cm/s. Additionally, we observe two offsets which are dependent on the observation type: an along-track offset of 13 m in the position residuals when using the velocity-only approach and a radial offset of 1.3 cm/s in radial velocities when using the position-only approach.</p><p>The periodicity in radial and along-track direction is related to the orbit eccentricity and may be due to a general deficiency, when using velocities to estimate geometric orbit parameters. When comparing the orbits from the position-only and the velocity-only approach, we find an offset in the right ascension of the ascending node, which corresponds to a maximum cross-track position difference of 40 m at the equator. We show that this effect is caused by a periodic bias in the velocity solutions with a maximum at the poles. A possible cause for such a periodicity in the velocity solutions may be dynamic effects in the receiver tracking loops related to the LEO satellite velocity relative to the GNSS constellation, which can vary strongly within one revolution.</p><p>Our results show that both, the radial position offset and the along-track velocity offset are dependent on the altitude of the satellite and are likely to be caused by ionospheric refraction. The explanation for the along-track position offset and the along-track velocity offset, however, is not that obvious. We found that these two offsets are geometrically related and, thus, must have the same physical cause. Based on the combined position-and-velocity approach we demonstrate that they originate from a velocity bias rather than from a position bias. To explain the physical cause of such a radial velocity offset, we will study the ionospheric effects on GNSS code and Doppler measurements in more detail, where we use a 3D-ionosphere model and take also the altitude of the two satellites into account.</p>

Colorimetry of Acacia mangium wood from plantations in northeast Brazil

The aim of this study was to evaluate color characteristics in wood samples from Acacia mangium from a homogeneous plantation in Bahia state, northeast Brazil, and also analyze the influence of anatomical section and radial position in the trunk on color response to contribute to information for the best use of the wood, such as, for example, the optimization of the performance of the pieces in sawmill through the most acceptable aesthetic form by the final consumer. Six trees with age of 14 years were cut. The species was identified by anatomical analysis at the Laboratory of Wood Anatomy of the Federal University of Paraná, comparing the sample collected with the authenticated material. A disc from the base of each tree was divided into six samples oriented in anatomical sections (transversal, radial and tangential), with dimensions of 20 × 20 × 30mm, named near pith, intermediate and near bark. A total of 36 samples were evaluated, 12 from each position. The colorimetric evaluation was performed with a CM-5 spectrophotometer. Data on lightness, green-red and blue-yellow chromatic coordinates were obtained, and values of saturation and hue angle were calculated. Acacia wood from planted forest is classified as olive color. Color parameters were influenced by anatomical section and radial position in the trunk, being found 44 for the transversal section, 55 for the tangential section and 57 in the radial for luminosity. Transversal sections had lower values in comparison to longitudinal surfaces and radial sections had higher luminosity than tangential sections. The near bark region presented lower values in most colorimetric parameters, except hue angle, in comparison with the intermediate and near pith regions, which was around 70 in the different positions of the wood.