Cone Edge Research Articles

Experimental Study on the Effects of Low Ambient Pressure Conditions at High Altitude on Fire Suppression with Water Mist

In order to study the effects of low ambient pressure conditions at high altitude on fire suppression with water mist, a water mist fire suppression experimental facility was built in Lhasa, Tibet, a province of China. Using this facility, water mist extinguishing tests were carried out on gasoline, diesel oil, molten ghee, and wood crib fires, and the results compared with the similar tests conducted in Hefei. Water mist spray patterns under normal and low atmospheric pressures were characterized with a laser sheet method. Fuel mass burning rates were measured in both Lhasa and Hefei to investigate differences and influences on fire suppression. The experimental results showed that the burning rates of the above fuels are lower in Lhasa than in Hefei, and that mist droplets tended to congregate along the spray cone edge as the atmospheric pressure decreased. For most of the test cases, the fire suppression performance of water mist in Lhasa is a little better than that in Hefei, which may be largely caused by decreasing of the mass burning rate at lower atmospheric pressure conditions.

The Solution of Mitchell's Problem for the Elastic Infinite Cone with a Spherical Crack

The new problem about the stress concentration around a spherical crack inside of an elastic cone is solved for the point tensile force enclosed to a cone's edge. The constructed discontinuous solutions of the equilibrium equations have allowed to express the displacements and stress in a cone through their jumps and the jumps of their normal derivatives across the crack's surface. The application of the integral transformation method under the generalized scheme has reduced the problem solving to the solving of the integrodifferential equation system with regard to the displacements' jumps. This system was solved approximately by the orthogonal polynomial method. The use of this method has allowed to take into consideration the order of the solution's singularities at the ends of an integral interval. The correlation between the crack's geometrical parameters, its distance from an edge, and the SIF values is established after the numerical analysis. The limit of the proposed method applicability is specified.

Carbon nanocones: wall structure and morphology

Large-scale production of conical carbon nanostructures is possible through pyrolysis of hydrocarbons in a plasma torch process. The resulting carbon cones occur in five distinctly different forms, and disc-shaped particles are produced as well. The structure and properties of these carbon cones and discs have been relatively little explored until now. Here we characterize the structure of these particles using transmission electron microscopy, synchrotron x-ray and electron diffraction. The carbon nanocones are found to exhibit several interesting structural features; instead of having a uniform cross-section, the walls consist of a relatively thin inner graphite-like layer with a non-crystalline envelope, where the amount of the latter can be modified significantly by annealing. The cones appear with a well-defined faceting along the cone edge, demonstrating strict long-range atomic ordering; they also present occasional examples of symmetry breaking, such as two apexes appearing in the same carbon nanocone.

Continuum and all-atom description of the energetics of graphene nanocones

Energies of graphene nanocones with 1–5 pentagonal disclinations are studied on anatomically detailed level. The numerical results are interpreted in terms of three differentcontributions to the cone energy: the disclination core energy, the bending energy of thecone surface, and the ‘line tension’ energy of the cone edge that originates in reducedcoordination of carbon atoms situated at the edge. This continuum description allows for aconstruction of analytic expressions for the cone energetics and indicates different regimesof cone sizes in which cones with a particular number of disclinations are preferredenergywise. An important result of the study is that the energetics of various types of conesprofoundly depends upon whether the dangling carbon bonds at the cone basisare saturated by hydrogen atoms or not. This may be of use for explaining thedifferences in the yields of various cone types in different production processes.

Wavefront singularities associated with the conical point in elastic solids with cubic symmetry

The wavefronts from a point source in a solid with cubic symmetry are examined with particular attention paid to the contribution from the conical points of the slowness surface. An asymptotic solution is developed that is uniform across the edge of the cone in real space, the interior of which contains the plane lid wavefront analyzed by Burridge [R. Burridge, The singularity on the plane lids of the wave surface of elastic media with cubic symmetry, Q. J. Mech. Appl. Math. 20 (1967), 41–56]. The uniform solution also contains the regular wavefronts away from the cone edge, a delta pulse on one side and its Hilbert transform on the other. In the direction of the cone edge the three wavefronts merge to produce a singularity of the form H( t) t −3/4.

FRET imaging in nerve growth cones reveals a high level of RhoA activity within the peripheral domain

Rho-family GTPases play a central role in the regulation of neuronal morphogenesis. In growth cones, for example, Rho GTPases transduce extracellular stimuli into structural changes such as filopodia and lamellipodia. Although it is generally accepted that Rac1/Cdc42 and RhoA are positive and negative regulators of neurite outgrowth, respectively, the role of each Rho-family member in neuronal morphogenesis may change according to the cell context. At present, the mechanism underlying this complexity is largely unknown. In growth cones, this is partly due to a lack of information on the distribution of active Rho GTPases. Here, we visualized RhoA/Rac1/Cdc42 activities during laminin-induced growth cone advance of DRG neurons and N1E-115 neuroblastoma cells using probes based on fluorescence/Förster resonance energy transfer. The Rac1 and Cdc42 activities were high in the peripheral domain (P-domain) of growth cones. Active Rac1 was uniformly detected throughout the P-domain, whereas Cdc42 activity increased gradually toward the growth cone edge. Against a model involving RhoA down-regulation at the periphery of protruding growth cones, we found that the RhoA activity was higher in the P-domain than in the central domain and axon shaft, and that a high level of RhoA activity was maintained in the extending part of growth cones. In lysophosphatidic acid-treated N1E-115 cells, well-developed neurites with growth cones showed RhoA activation, but sustained their extended morphology until they were drawn toward the contracting somata. On the other hand, suppression of RhoA activity by C3 exoenzyme led to loss or deformation of actin bundles in the growth cones. Thus, RhoA activation in the shaft results in neurite retraction, whereas high RhoA activity in the P-domain is necessary to retain the spread morphology of nerve growth cone.

Kinesin Superfamily Protein 2A (KIF2A) Functions in Suppression of Collateral Branch Extension

Through interactions with microtubules, the kinesin superfamily of proteins (KIFs) could have multiple roles in neuronal function and development. During neuronal development, postmitotic neurons develop primary axons extending toward targets, while other collateral branches remain short. Although the process of collateral branching is important for correct wiring of the brain, the mechanisms involved are not well understood. In this study, we analyzed kif2a −/− mice, whose brains showed multiple phenotypes, including aberrant axonal branching due to overextension of collateral branches. In kif2a −/− growth cones, microtubule-depolymerizing activity decreased. Moreover, many individual microtubules showed abnormal behavior at the kif2a −/− cell edge. Based on these results, we propose that KIF2A regulates microtubule dynamics at the growth cone edge by depolymerizing microtubules and that it plays an important role in the suppression of collateral branch extension.

Features of the Application of Slender-Body Theory to the Calculation of Supersonic Water-Stream Cavitation Flow Past Cones

Features of the application of slender-body theory to the calculation of supersonic water-stream cavitation flows past cones are described. It is shown that the boundary condition on the cone edge in whose neighborhood Prandtl-Meyer flow develops cannot be satisfied within the framework of slender-body theory. The cone drag coefficients determined on the basis of slender-body theory are compared with the results of numerical calculations of conical flows.

A Hybrid GMT-PO Method for Calculating the NDC of the Irregular Edge of a Semi-Infinite Cone

In this paper, the GMT-PO hybrid method accompanying with the iterative technique is applied successfully to calculate 3-D diffraction coefficients(3D-NDC) of the irregular cone edge. The computed RCS (backward NDC) of a finite cone with regular top is in good agreement with the measured data from the reference.

On the influence of the initial pitch angle distribution on relativistic electron beam dynamics

Simulations of the evolution of a relativistic electron beam injected into the Earth's magnetosphere are examined. It is found that the lifetime of beam particles strongly depends on the initial pitch angle distribution and that lifetimes similar to those found for the radiation belts are obtained for nearly equatorially mirroring injections. It is concluded that the results of our previous study on beam propagation [Khazanov et al, 1999], which only considered upper ionospheric injections, are consistent with other relativistic electron studies and should be regarded as an examination of the loss cone edge population, whether naturally occurring or artificially injected into near‐Earth space.

Co-produced carbon and boron nitride helical cones and the nucleation of curved BN sheets

Abstract The structure of carbon (C) and boron nitride (BN) columnar particles produced alongside by heat-treating a turbostratic B—C—N compound was investigated by analytical transmission electron microscopy. The particles were shown to be helical cones with a well-defined apex, and a helical pitch equal to usually one and at most two layers. The cone apex angle distribution was found to be centred on different values for C and BN. These results strongly suggested that BN and C cones nucleated from different ring defects in the hexagonal networks: square-like ring defects in BN and pentagon-like ring defects in C. These observations were consistent with the supposition that the creation of non B—N bonds and hence odd-membered rings is avoided in BN. Such restriction in BN could also allow one to understand the observed morphological differences between C and BN cones, and in particular the relative difficulty for BN cone edges to join via curved sheets.

Aspects of thrust cone tribology: Part 2: Surface failure in thrust cones and the influence of rolling and sliding speeds in concentrated contacts

This paper outlines relevant aspects of the operation of thrust cones and describes salient features of an unexpected form of failure encountered in small-scale thrust cone simulation tests. Interpretation of the thrust cone simulation test results in the light of related twin-disc tests at the relevant low slide-roll ratio leads to two conclusions. Rather than scuffing, the limiting surface failure mechanism in small-scale thrust cone tests was general plastic deformation with cold pressure welding promoted by the lack of support at the cone edges and the prolate epicycloidal path followed by the contact. The limiting surface failure mechanism in full-scale thrust cone bearings, which have markedly lower curvature and higher rolling speed than used in small-scale simulation tests, was predicted to be scuffing delayed to relatively severe operating conditions by prior running-in. Further development of the insights gained from the related twin-disc work results in two recommendations. Future work should be directed to assessing the surface modification that follows transition from EHL to mixed lubrication and redefining the conditions in which transition to micro-EHL occurs in order to quantify the potential enhancement of scuffing resistance offered by controlled running-in. It should also concentrate on evaluating the combined effects of microgeometry conducive to lubricant film formation and material properties resistant to weld formation in order to obviate the difficulty of assigning a representative value to the operating friction coefficient that is common to a number of proposed failure criteria.

Collimating the ionizing radiation in AGN

The hard-edged ionization cone seen by the HST imaging of NGC 4151 and the line-of-sight gas observed in some Seyfert 1 galaxies present a strong challenge for the simplest version of the Unified Model of AGN, which predicts that bi-conically shaped EELR can be observed only in type 2 objects and the line-of-sight to type 1 nucleus must be clear. To accommodate these rather contradictory requirements we suggest a modification of the shadowing/obscuration scenario. In our model the collimation of the ionizing radiation is provided by a partially neutral atmosphere surrounding the physically thin, dense torus. This atmosphere provides a natural way of producing wide angle ionization cones and at the same time allows for a relatively clear view of the central regions for some angles outside the cone edges. The model has an observationally testable predictions. Recently discovered nuclear disks in some elliptical galaxies hosting AGN may provide a natural way of supplying the gas for both the torus and the atmosphere surrounding it.

TAURUS observations of the [O III] cone in NGC 1068

TAURUS observations of the [O III] λ5007 emission from NGC 1068 show that most of the high-excitation line emission originates in an edge-brightened cone. The morphology, excitation, and kinematic properties of this [O III] cone all imply that the line-emitting gas is photoionized by a highly anisotropic nuclear radiation field. The edge-brightening makes possible an accurate determination of the cone parameters, and hence the parameters of the collimated nuclear radiation field; we derive a PA of |$31^\circ \pm 3^\circ$| and a projected opening angle of |$40^\circ \pm 3^\circ$|⁠. It seems unlikely that the edge-brightening of the [O III] cone is intrinsic to the mechanism by which the radiation field is initially collimated. We suggest that the edge-brightening might be due either to the presence of relatively dense gas along the cone axis, associated with the radio components, or to a density enhancement along the cone edges, caused by a lateral expansion of the ionized material within the cone. The [O III] cone is closely aligned with the kpc-scale radio jet/lobe |$(\text{PA}=33^\circ)$|⁠. Furthermore, the [O III] and radio emission both show a side-to-side asymmetry in the same sense. This suggests a model for the collimation mechanism in which the radio jet clears a path through obscuring material surrounding the galactic nucleus, through which the ionizing radiation can then escape. However, this picture is complicated by the observation that the axis of the UV cone derived from spectropolarimetry of the optical nucleus lies in |$\text{PA}=2^\circ$|⁠, misaligned with the PA of the large-scale radio and [O III] structures, and by the fact that the subarcsecond radio structure appears to bend between these two PAs. We speculate that different collimation mechanisms may be relevant on different size-scales.

Calculation of electrostatic multitubular core-lenses for a 3D imaging electron microscope: Three-dimensionally imaging electron microscopes, (part IV)

Abstract Axially symmetric electrostatic multitubular core-lenses are especially suited for three-dimensional imaging by electron-optical tilting. Objective lenses of this type are calculated numerically and a lens system with a dispersion-free cone edge focus is found by optimization. For 50 keV electrons and a focal length of 1 cm, the coefficient of the third-order aperture aberration and the coefficient of the axial chromatic aberration of the first order are about 20 cm referred to the object plane. This yields a theoretical point resolution of 1.4 nm. Rotationally symmetric electrostatic multitubular core-lenses can also be used as high performance spectrometers for electrons or ions.

Film dosimetry of multiple electron beam ports with wedges

Treatment plans that call for the use of multiple adjacent electron beam ports over large areas require careful consideration of the dose in the zones of overlap. A method is described to reduce the inhomogeneity utilizing acrylic resin wedges placed over contiguous treatment cone edges and a water-filled extruded polystyrene container designed to simulate the contour of the patient. The resulting improvement is demonstrated by the film dosimetry of a patient planned for post-operative radiotherapy to an intercostal malignant schwannoma with a 27 cm. long scar.

Xeromammographic cone edge pressure to shift deep lesions into view: a simple modification and technique.

A straight lower edge on the flat side of an open-ended mammographic cone, applied firmly downward along the chest wall, may sometimes displace deepseated breast lesions into the mammography beam. This can be done with simple materials.