Cone Axis Research Articles

Experimental and numerical analysis of decelerated swirling flow from the discharge cone of hydraulic turbines using pulsating jet technique

It is well known that the spiral vortex (or vortex rope) is developed in the conical diffuser of hydraulic turbines with fixed pitch blades (e.g. Francis and propeller) when operating conditions are far away from best efficiency point. The paper will present a new technique in order to mitigate, even eliminate the bad behave associated to this phenomenon. By injecting a pulsating water jet, along the cone axis, the unsteady pressure fluctuations given by the vortex rope are mitigated. Our investigations are performed on the test rig from Politehnica University. In order to assess the velocity profiles given by the swirling flow with and without pulsating water jet, an extensive 3D numerical simulations were performed. Second, the experimental data of pressure fluctuations was analysed. This technique, shows that the pressure recovery is improved and the hydraulic losses decreases along the conical diffuser. Also, it is shown that the stagnant region associated to the spiral vortex is mitigated since the pulsating jet is introduced. Also, the pressure fluctuations are mitigated.

Structure and abnormalities in cones of the Wollemi pine (Wollemia nobilis)

Reproductive structures of both genders of Wollemia nobilis were investigated, including both wild-type and teratological cones. Typically, both pollen cones and seed cones in this species are terminal on first order branches. At maturity, wild-type pollen cones are pendulous and cylindrical; wild-type seed cones are broad and ellipsoidal in shape. The teratological structures consisted of a basal region that resembled a typical fertile seed cone, and an apical proliferation that terminated in a well-developed pollen cone, resulting in a ‘bisexual’ unit. The proximal seed cone and the distal pollen cone were separated by a sterile region that represents an elongation of the cone axis. Of a total of 14 anomalous bisexual units investigated, all had the same bauplan. Such an arrangement of basal ovulate and distal staminate reproductive structures in a teratological conifer cone has previously not been reported for Wollemia. This topology is 'inside-out' with respect to most other reported anomalous bisexual conifer cones, which possess proximal staminate and distal ovulate structures. We discuss these spontaneous abnormalities in the broader context of understanding the homologies of seed-plant reproductive structures. The patterning of conifer cones is apparently highly labile, perhaps related to the extended cone axis and relatively long developmental duration.

Research on the influence of the off-axis processing axicon lens on the light field distribution of the non-diffracting beam

Non-diffracting beam are attracting increased attention because of their unique characteristics. A non-diffracting beam is usually generated with an axicon, which is a kind of line focus optical element with a conical surface axis that rotates symmetrically. Three deviation models of a generatrix relative to the ideal axicon have been established on its processing technology, namely, concave to the inner side, convex to the outer side and hyperbolic distribution of the apex of the axicon. The amplitude transmittance function is derived based on the profile of the generatrix. The emergent light field and intensity distributions of the three kinds of axicon in the case of plane wave verticality illumination are analyzed and simulated according to the Fresnel diffraction theory. Moreover, the theory of axicon diffraction field is enriched and the guiding significance for the processing of axicon lens is increased.

Understanding the cone scale in Cupressaceae: insights from seed-cone teratology in Glyptostrobus pensilis.

Both wild-type and teratological seed cones are described in the monoecious conifer Glyptostrobus pensilis and compared with those of other Cupressaceae sensu lato and other conifers. Some Cupressaceae apparently possess a proliferation of axillary structures in their cone scales. In our interpretation, in Glyptostrobus each bract of both typical and atypical seed cones bears two descending accessory shoots, interpreted here as seed scales (ovuliferous scales). The primary seed scale is fertile and forms the ovules, the second is sterile and forms characteristic tooth-like structures. The bract and the two axillary seed scales are each supplied with a single distinct vascular bundle that enters the cone axis as a separate strand; this vasculature also characterises the descending accessory short shoots in the vegetative parts of the crown. In wild-type seed cones, the fertile seed scale is reduced to its ovules, and the ovules are always axillary. In contrast, the ovules of some of the teratological seed cones examined were located at the centre of the cone scale. An additional tissue found on the upper surface of the sterile lower seed scale is here interpreted as the axis of the fertile seed scale. Thus, the central position of the ovules can be explained by recaulescent fusion of the upper fertile and lower sterile seed scales. In several teratological cone scales, the ovules were enveloped by an additional sterile tissue that is uniseriate and represents an epidermal outgrowth of the fertile seed scale. Close to the ovules, the epidermis was detached from lower tissue and surrounded the ovule completely, except at the micropyle. These teratological features are potentially significant in understanding seed-cone homologies among extant conifers.

Morphology of AGN emission-line regions in SDSS-IV MaNGA survey

Extended narrow-line regions (NLRs) around active galactic nuclei (AGN) are shaped by the distribution of gas in the host galaxy and by the geometry of the circumnuclear obscuration, and thus they can be used to test the AGN unification model. In this work, we quantify the morphologies of the narrow-line regions in 308 nearby AGNs ($z=0-0.14$, \lbol $\sim 10^{42.4-44.1}$ \erg{}) from the MaNGA survey. Based on the narrow-line region maps, we find that a large fraction (81\%) of these AGN have bi-conical NLR morphology. The distribution of their measured opening angles suggests that the intrinsic opening angles of the ionization cones has a mean value of 85--98$^\circ$ with a finite spread of 39-44$^\circ$ (1-$\sigma$). Our inferred opening angle distribution implies a number ratio of type I to type II AGN of 1:1.6--2.3, consistent with other measurements of the type I / type II ratio at low AGN luminosities. Combining these measurements with the WISE photometry data, we find that redder mid-IR color (lower effective temperature of dust) corresponds to stronger and narrower photo-ionized bicones. This relation is in agreement with the unification model that suggests that the bi-conical narrow-line regions are shaped by a toroidal dusty structure within a few pc from the AGN. Furthermore, we find a significant alignment between the minor axis of host galaxy disks and AGN ionization cones. Together, these findings suggest that obscuration on both circumnuclear ($\sim $pc) and galactic ($\sim$ kpc) scales are important in shaping and orienting the AGN narrow-line regions.

MoM analysis of cavity‐backed annular conical antennas

This study presents theoretical formulation and results for cavity-backed annular conical antennas. The formulation is based on equivalence principle and method of moments (MoM), in both point-matching and Galerkin forms. Results are presented for radiation diagram, and input impedance, and compared to those obtained using commercial software. The effects of dielectric thickness and of cavity dimensions on input impedance are presented. In addition, the feeding using two coaxial cables for radiation maximum at cone axis is also presented.

Director distribution in field-induced undulated structures of cholesteric liquid crystals

ABSTRACTStructures with a periodic in-plane liquid crystal director field modulation induced by an electric field are studied in cholesteric liquid crystals (CLCs). A phenomenon of the electric-field-induced instability in a planarly aligned cholesteric cell is used to create these undulated structures. The initial field-off state is planarly aligned with the cholesteric helix axis oriented perpendicular to the cell substrates. The interaction of the CLC with an electric field results in modulation of the refractive index, which is visualised as stripe domains oriented either along or perpendicular to the rubbing direction at cell alignment surfaces. The threshold electric field for the undulation appearance and a period of stripes are measured experimentally for three Grandjean zones (ratio d/p ~ 0.5, 1.0, and 1.5, where d is a cell thickness and p is the natural cholesteric pitch). For the zone with d/p ~ 1.0 using numerical simulations, we describe in detail the director distribution at an applied electric field. It is found that the in-plane undulated structure is characterised by a conical director rotation on moving along the alignment direction. The conical axis is tilted with respect to the alignment axis. The sign of the tilt angle depends on the handedness of CLC.

A new species of Elatides from the Lower Cretaceous in Shandong province, Eastern China and its geographic significance

Elatides, an ancient extinct conifer, is of great significance for studying the composition of forest vegetation in the Northern Hemisphere during the Mesozoic. A new Elatides species, Elatides laiyangensis sp. nov., has been described and diagnosed from the Lower Cretaceous Laiyang Formation in Shandong Province, China. The details of the gross morphology and cuticular structure of the new species have been studied. The significant characters of the studied fossils can be concluded as follows: the seed cones are ovate or round, and the middle part of the cone is the widest. It tapers slightly near the apex; the bract–scale complexes are numerous, broad–ovate or triangular–ovate, helically and imbricately arranged on the cone axis and compactly in each other, with an acuminate and slightly curved inward apex; the epidermal cells on the apex and middle part of bracts are irregular polygonal, and long–rectangular or long–rectangular on the side edge and basal; and the stomata complexes are predominantly on the apex and middle part of the adaxial surface. These features are much similar to those of the extant Cunninghamia, which provides further support for a phylogenetic relationship between Elatides and Cunninghamia. Since the morphological (macrostructure and microstructure) features of this species differ from any known species in the fossil records, it can be considered as a new species of Elatides. Associated leafy branches are also comparable to those of Cunninghamia lanceolata in shape and cuticular structure. The geographical distribution of Elatides through time is closely related to the prosperity-decline of the genus, geological events in Mesozoic and the trends of global paleoenvironmental change. Therefore, it can be inferred that this genus may possess high sensitivity to climate change, especially to temperature. Furthermore, the occurrences of Elatides seed cones and foliage shoots from the Laiyang Basin provide new information on the geographic distribution of Elatides in China, which indicates that Shandong should be the adaptive way through which the genus was transported from Hebei (Northern China) to Zhejiang and Fujian (Southern China).

Insights into anisotropy development and weakening of ice from in situ P wave velocity monitoring during laboratory creep

AbstractPolycrystalline ice weakens significantly after a few percent strain, during high homologous temperature deformation. Weakening is correlated broadly with the development of a crystallographic preferred orientation (CPO). We deformed synthetic polycrystalline ice at −5°C under uniaxial compression, while measuring ultrasonic P wave velocities along several raypaths through the sample. Changes in measured P wave velocities (Vp) and in the velocities calculated from microstructural measurements of CPO (by cryo‐electron backscatter diffraction) both show that velocities along trajectories parallel and perpendicular to shortening decrease with increasing strain, while velocities on diagonal trajectories increase. Thus, in these experiments, velocity data provide a continuous measurement of CPO evolution in creeping ice. Samples reach peak stresses after 1% shortening. Weakening corresponds to the start of CPO development, as indicated by divergence of P wave velocity changes for different raypaths, and initiates at ≈3% shortening. Selective growth by strain‐induced grain boundary migration (GBM) of grains favorably oriented for basal slip may initiate weakening through the formation of an interconnected network of these grains by 3% shortening. After weakening initiates, CPO continues to develop by GBM and nucleation processes. The resultant CPO has an open cone (small circle) configuration, with the cone axis parallel to shortening. The development of this CPO causes significant weakening under uniaxial compression, where the shear stresses resolved on the basal planes (Schmid factors) are high.

Fiber properties of axis and scale of eleven different coniferous cones

Fiber properties of eleven different coniferous cones, growing naturally in Turkey, were studied. Axis and scales of cones were analyzed separately. The slenderness, flexibility, and Runkel ratios were derived from measured fiber dimensions. Fiber length and fiber width of cones were between 0.93mm and 1.87mm, 16.6μm and 32.2μm, respectively. The longest fiber length was determined with 1.87mm in Pinus pinea cone axis fibers. Also, the widest fiber (32.2μm) and the widest lumen (20.0μm) were found in Abies equi-trojani cone scale fibers. The thickest cell wall (8.40μm) were found in Pinus sylvestris cone axis fibers. The sclerenchyma fibers, which were shorter and wider than fibers, were observed both in scale and axis of all cones. In general, cone axis fibers had lower slenderness and Runkel ratios and higher flexibility ratio than those of cone scale fibers. These results indicated that fiber properties of coniferous cones showed similarities with fibers of hardwood and nonwood species.

The Thermoheliodome – “Air conditioning” without conditioning the air, using radiant cooling and indirect evaporation

The Thermoheliodome is an experimental pavilion that explores cooling without air conditioning. The two research aims were to explore the use of indirect evaporative cooling and the geometric reflection of radiant cooling. For evaporative cooling we utilize a cooling tower outside of the pavilion to indirectly supply water chilled near the wet-bulb temperature. The radiant cooling system is made up of 55 coaxial chilled pipes each located in the central axis of cones with reflective surfaces that spectrally reflect the surface of the pipes and expand their radiant view factor to the occupants inside the pavilion. The specific geometry was digitally fabricated using an industrial robot and hot-wire foam cutter. The mean radiant temperature (MRT) was shown to be significantly decreased using thermal imaging cameras and with a novel scanning MRT sensor. The radiant cooling delivered from the fluid is maximized by reflection and concentration of heat emitted by occupants on the pipes, while the convective cooling of the air is minimized because only the small pipes are cooled and the reflecting surfaces are not, so the convective heat transfer surface area is small. Under typical indoor office conditions the ratio of radiant to convective cooling is slightly greater than one. For the Thermoheliodome the radiant ratio was greater than 10. Occupant surveys found that although the air temperature was not modified, they felt that inside the space there is a cooling sensation (p≤0.01). The day of the survey they felt on average 3°C cooler.

Multiple conical spin order in spinel structure stabilized by magnetic anisotropy

Conical spin order, where the spin components along the conical axis form magnetization while the spiral parts induce ferroelectric polarization, possesses multiferroicity with inherent magnetoelectric coupling. A Monte Carlo simulation performed using a classical Heisenberg spinel (AB2O4) model reveals a multiple conical spin order, i.e., three modulations with different cone angles and wavelengths on A sites and two alternate B sites. The spin order not only exists as the ground state but also survives locally stably in a larger parameter region. The whole existence range can be effectively expanded by anisotropy to cover the cases of CoCr2O4 and MnCr2O4. The multiple conical spin order is well maintained and finely tuned by frustration and anisotropy over the whole existence range, and the magnetic and ferroelectric properties are influenced correspondingly.

The down-stress transition from cluster to cone fabrics in experimentally deformed ice

During plastic deformation of polycrystalline ice 1h, ice crystals become crystallographically aligned due to dislocation glide, primarily on the basal slip system. Such crystallographic preferred orientation (CPO) introduces a viscous anisotropy in ice, and thus strongly influences the kinematics of the flow of glaciers and ice sheets. Two key mechanisms exert different controls on CPO. In axial compression, recrystallization dominated by lattice rotation yields a cluster of c-axes parallel to compression, and recrystallization dominated by grain boundary migration (GBM) yields a cone-shaped distribution of c-axes with the cone axis parallel to compression. The transition between these dominant mechanisms of CPO formation has not been well quantified. In this study, we explore how this transition varies with stress. Ice deformation experiments were conducted using a high-pressure, gas-medium apparatus to prevent fracturing of samples at relatively high stresses. Samples were deformed in uniaxial compression at a temperature of ∼−10 °C and a confining pressure of 10 MPa. Fabricated ice samples with starting average grain sizes of either ∼0.23 mm or ∼0.63 mm were each deformed to an axial strain of ∼0.2 at a nominally constant strain rate in the range 1.2×10−6 to 2.4×10−4 s−1, yielding flow stresses of 1.17 to 4.31 MPa. High-quality electron backscatter diffraction reveal the grain size, shape, subgrain structure, and CPOs formed at different stresses. All deformed samples have strong, non-random CPOs with c-axes concentrated in cones. The cone angle and CPO strength are observed to decrease with increasing stress. As stress increases, the fraction of grains with highly curved or lobate grain boundaries decreases and the fraction of polygonal grains with straight grain boundaries increases. Based on these observations, we propose that a transition in the dominant mechanism of CPO formation occurs with increasing stress, from GBM, which consumes grains with low Schmid factors at low stress, to lattice rotation caused by slip primarily on the basal slip system, which causes c-axes to rotate to become parallel to the shortening direction at high stress. Mapping out the transition from cluster (rotation-dominated) to cone (GBM-dominated) CPOs as a function of stress (this study) and temperature (future studies) allows for a robust extrapolation to, and a fundamental understanding of the CPOs formed at, glaciological stresses and temperatures.

Axis retrieval of a supersonic source in a reverberant space using time reversal

Localizing the axis of the Mach cone created by the supersonic displacement of a bullet in a reverberant environment is a challenging task, not only because of the high velocity of the moving source, but also because of the multiple wave reflections off of the walls. Although time reversal (TR) techniques allow static acoustic source localization in a reverberant space, they have not been explored yet on non stationary waves caused by supersonic displacements in urban canyons. The acoustic wave produced by a supersonic projectile has a conical wavefront and a N-shaped acoustic pressure signature. In this paper, this acoustic wave is reproduced using a line array of point-like sources (simulations) and loudspeakers (experiments). During the propagation of this conical wave in an urban canyon, the resulting pressure signals are measured using a time reversal array flush mounted into the ground. These acoustic signals allow to automatically retrieve with a high accuracy the location of the Mach cone axis using time reversal techniques. This inverse problem is solved using the maximization of a fourth-order statistical criterion of the backpropagated pressures. This criterion allows to estimate the intersections between the Mach cone axis and several vertical planes in the urban canyon. These estimations are then fitted to a 3D trajectory with a robust three dimensional interpolation technique based on the Random Sample Consensus (RANSAC) algorithm. This method allows to automatically retrieve the axis of the supersonic source with an angular accuracy of less than 0.5° and a misdistance of 0.5cm for both numerical simulations and experimental measurements.

Passively-coupled, low-coherence interferometric duct profiling with an astigmatism-corrected conical mirror.

Duct-profiling in test samples up to 25 mm in diameter has been demonstrated using a passive, low-coherence probe head with a depth resolution of 7.8 μm, incorporating an optical-fibre-linked conical mirror addressed by a custom-built array of single-mode fibres. Zemax modelling, and experimental assessment of instrument performance, show that degradation of focus, resulting from astigmatism introduced by the conical mirror, is mitigated by the introduction of a novel lens element. This enables a good beam focus to be achieved at distances of tens of millimetres from the cone axis, not achievable when the cone is used alone. Incorporation of the additional lens element is shown to provide a four-fold improvement in lateral imaging resolution, when compared with reflection from the conical mirror alone.

The conical conformal MEMS quasi-end-fire array antenna

The microelectromechanical system (MEMS) quasi-end-fire array antenna based on a liquid crystal polymer (LCP) substrate is designed and fabricated in this paper. The maximum radiation direction of the antenna tends to the cone axis forming an angle less than 90[Formula: see text], which satisfies the proximity detection system applied at the forward target detection. Furthermore, the proposed antenna is fed at the ended side in order to save internal space. Moreover, the proposed antenna takes small covering area of the proximity detection system. The proposed antenna is fabricated by using the flexible MEMS process, and the measurement results agree well with the simulation results. This is the first time that a conical conformal array antenna is fabricated by the flexible MEMS process to realize the quasi-end-fire radiation. A pair of conformal MEMS array antennas resonates at 14.2 GHz with its mainlobes tending to the cone axis forming a 30[Formula: see text] angle and a 31[Formula: see text] angle separately, and the gains achieved are 1.82 dB in two directions, respectively. The proposed antenna meets the performance requirements for the proximity detection system which has vast application prospects.

Regarding the structure and possible function of the columella in seed cones of Callitroideae (Cupressaceae): a morpho-anatomical approach

‘Columella’-named structures in seed cones of callitroid Cupressaceae were investigated. In the past, the term columella was used for different structures, which should not be summarised and treated under the same name. We suggest that all apices should be called columella, which exclusively represent the prolonged tip of the cone axis and do not reach the periphery of the seed cone and do not take part in it. The three distal lobes in Fitzroya Lindl. represent a sterile, strongly reduced, distal whorl of cone scales and not naked nucelli or resin glands as suggested in former studies. They should not be termed columella. The columellae and also the three lobes in Fitzroya may play a role within the pollination process and possibly in the chemical defence against pathogens. The columella, as it is defined here, is not restricted to the Callitroideae and is also present in other Cupressaceae, including Cupressus L. and Thujopsis Siebold & Zucc.

Influences of vacancy defects on tensile failure of open-tip carbon nanocones

This paper studied influences of vacancy defects on tensile failure of open-tip carbon nanocones (CNCs) by molecular dynamics simulations. Carbon nanocones, perfect and containing mono-vacancy defects (including CNCs with the upper-vacancy, the middle-vacancy, and the lower-vacancy), were simulated in order to understand the influence of the presence and location of the vacancy defects on the CNCs tensile behavior. Some findings were obtained. It was found that the upper-vacancy CNC has the greatest degradation in the failure strain and the failure load among the three vacancy-defect CNCs, and the lower-vacancy CNC has the smallest degradation in the failure strain and the failure load. Degradation in the failure load is larger than degradation in the failure strain. Moreover, no apparent yielding (large elongation) was observed before failure of the studied CNCs. All the vacancy-defect CNCs were broken near the top end rather than near the vacancy location of the CNCs. The behaviors of the vacancy-location-dependent degradation and the vacancy-location-independent failure (namely, the near top-end failure) of the vacancy-defect CNCs are quite different from those of vacancy-defect CNTs (carbon nanotubes). These particular behaviors are ascribed to non-uniform diameters along the cone axes of the CNCs.

Comparison of pyrolytic graphite spheres from propylene with spheroidal graphite nodules in steel

Two types of the spherical growth form of graphite from different precursors, pyrolytic graphite spheres (PGSs) formed by pyrolysis of propylene and spheroidal graphite nodules (SGNs) formed by heat treatment of the medium carbon steel, are investigated by scanning electron microscopy and transmission electron microscopy. Microstructural similarities and differences of these graphite spheres are drawn. The results show that PGSs and SGNs have a similar core-shell microstructure, which comprises a low graphitic core in the center and conical grains growing outward radially from the core with the cone axis along the c-axis direction of graphite. The role of hydrogen on pyrolytic graphite sphere formation is discussed, and we suggest layer-by-layer growth of the spheroidal graphite nodules by two-dimensional nucleation on the basal plane based on the parallel arrangement of graphene layers in the sectors. It is shown that the state of the precursor, gas, liquid, or solid, is not a determining factor on governing the resultant microstructure of graphite spheres.

Granular mixing in nauta blenders

Flow pattern of particles and their mixing performance in a Nauta blender were studied using the discrete element method. The model was validated by experimental data obtained in a convective conical screw blender and good agreement was obtained. Flow pattern of particles was studied through velocity profiles, granular temperature and streamlines of particles. Effects of sweeping rotation speed, primary rotation speed and impeller diameter on the mixing quality and mixing rate were studied. A vertical circulation pattern in the blender was observed due to the primary rotation of the impeller that produced a convective and layered flow. In this pattern, particles are lifted to the bed surface and then descend at the opposite side of the screw. On the other hand, the sweeping rotation of the impeller pushes the particles along the direction of sweeping which leads to a tangential flow of particles. Combination of primary and sweeping rotations of the impeller results in a three dimensional particle mixing. A semi-stagnant zone is also formed temporarily near the cone axis. It was found that increasing the primary rotation speed (from 5 to 10rad/s) and impeller diameter (from 9.72 to 10.8cm) improve the mixing rate (from 0.02096 to 0.05321/s and from 0.02462 to 0.034651/s, respectively), while increasing the sweeping rotation speed (from 0.15 to 0.45rad/s) decreases the Lacey index and the mixing rate (from 0.04429 to 0.03131/s). To reach a deeper understanding about the effect of sweeping rotation on the mixing behavior, eight different sweeping velocities were studied and the maximum mixing rate was observed at 0.05rad/s.