Significant Curvature Research Articles

Curvature Evolution of Porcelain Tile during Firing

Planarity is one of indispensable attribute of a ceramic tile quality. During the firing changes on curvature may be permanent causing damage on quality and productivity. The objective was to evaluate curvature evolution on porcelain tile during heating stage of firing. Effects of engobe and glaze coating were evaluated. The performance of two compositions of porcelain tile was studied on industrial (1000 mm x 500 mm x 10 mm) and laboratorial (100 mm x 50 mm x 6 mm) scale. Industrial test pieces were fired at 950 and 1200 °C. Final curvature was measured by conventional dial indicator. Curvature evolution of laboratorial test pieces was evaluated by thermal fleximetry from 25 to 1200 °C. This characterization was capable to identify very significant positive curvature deflection on temperature range from 930 to 1200 °C, directly associated to permanent planarity defects. Differences on composition affect significantly the curvature evolution.

Wind-blown pool fire, Part I: Experimental characterization of the thermal field

Experiments were conducted to investigate the macroscopic thermal behaviour of 2m diameter Jet A fires in crosswinds of 3–10m/s. This scenario simulated an outdoor transportation accident with the fire representing a burning pool of aviation fuel. To date, the limited number of experiments that have been conducted to examine wind effects on fire behaviour have generally been performed at small scale, which does not fully simulate the physics of large fires, or in outdoor facilities, with poorly controlled wind conditions. This paper presents the first systematic characterization of the thermal environment in a large, turbulent, pool fire under controlled wind conditions. Three parameters describing flame geometry – flame tilt, flame length and flame drag – were measured using temperature contour plots and video images. The temperature-based method of estimating flame geometry provided considerable improvement over visually based methods, particularly when significant smoke blockage of the luminous flame envelope occurred. At low wind speeds, significant plume curvature was observed, hindering description of flame tilt by a single angle. As the wind speed increased up to 10m/s, extremely high levels of flame tilt, flame drag and flame length occurred.

QTAIM-based comparison of agostic bonds and intramolecular charge-inverted hydrogen bonds.

Using DFT-based calculations with seven exchange-correlation functionals (BP86, B3LYP, B3PW91, PBE0, TPSSh, M06-L, M06) we have performed comparative studies on α-, β-, γ-, and δ-agostic bonds (ABs) and intramolecular charge-inverted hydrogen bonds (IMCIHBs). Our detailed analysis of values of QTAIM parameters computed at bond (BCP) and ring critical points (RCP) as well as of the curvatures of bond paths tracing agostic bonds and intramolecular charge-inverted hydrogen bonds gives the opportunity to distinguish between both these types of interactions. In the case of molecules with agostic bonds, the BCP is significantly closer to the agostic hydrogen, whereas in systems with IMCIHB the BCP is, instead, somewhat closer to the metal atom. Agostic bonds are characterized by H···M bond paths being straight in the BCP···M section and then highly curved near the agostic hydrogen, whereas in the case of IMCIHB any substantial curvature of BP in the vicinity of hydrogen is not present. Quite the contrary, the significant curvature of BP near the metal atom can be obtained, instead. One can also distinguish IMCIHBs and ABs on the basis of values of bond ellipticity at BCP and the electron density at RCP which are either somewhat (PBE0) or considerably (M06) greater for the latter type of interaction. It has also been shown that, in general, the exchange-correlation functional has small influences on most of QTAIM parameters computed at BCP and RCP. More significant influences have only been obtained for Laplacian of the electron density, some its components, and the bond ellipticity.

Effects of the HCN adsorption on the structural and electronic parameters of the beryllium oxide nanotube

The adsorption behavior of the HCN on the surface of beryllium oxide nanotube (BeONT) is studied by the density functional theory. Geometrical parameters, electronic properties and adsorption energies have been calculated for the BeONT and fourteen different HCN configurations on the nanotube. According to the obtained results, the process of the HCN molecule adsorption on different sites on the external surface of the nanotube is exothermic and all of the configurations are stable, while the process of HCN molecule adsorption on the internal surface of the BeONT is endothermic. The adsorption energy values indicate that the HCN molecule can be physically adsorbed on the surface of the BeONT. Furthermore, the HOMO–LUMO gap (Eg) of the BeONT decreases upon the HCN adsorption, resulting in the enhancement of the electrical conductivity. The AIM theory has been also utilized to analyze the properties of the bond critical points: their electron densities and their Laplacians. NBO analysis indicates that the HCN molecule can be adsorbed on the surface of the nanotube with a charge transfer from nanotube to HCN molecule. Due to the physisorption, NQR parameters of nanotube are also altered. In order to examine the deformation degree of the nanotube after HCN molecule adsorption, deformation energy is calculated, which indicates that no significant curvature in the geometry of the nanotubes is occurred when HCN adsorbs onto the surface of BeONT.

Simultaneously measuring ocular aberration and anterior segment biometry during accommodation

In the human eye, accommodation is essential for functional vision. However, the mechanisms regulating accommodation and the ocular parameters affecting aberrations remain to be explored. In order to measure the alterations of ocular aberration and crystalline lens biometry during dynamic accommodative stimuli, we designed an optical coherence tomography with ultra-long penetration depth (UL-OCT) combined with a Shack–Hartmann wavefront sensor (SHWFS). This integrated set up measures human eye's anterior segment as well as monochromatic high-order aberrations (HOAs) with 6 μm resolution and (1/20) λ accuracy. A total of 10 healthy volunteers without ocular diseases were examined. Upon exposure to accommodative stimuli, the wavefront aberrations became larger. Among the anterior segment biometry, the anterior crystalline lens demonstrated significant curvature during accommodation and was the major cause of high-order aberration. These findings suggest that the front surface of the crystalline lens can significantly affect variation among aberrations, which is a key factor underlying the quality of human vision.

Strategies for penile prosthesis placement in Peyronie's disease and corporal fibrosis.

Peyronie's disease (PD) is a wound healing disorder of the tunica albuginea of the penis. PD is generally categorized into two phases: the early acute inflammatory and late chronic fibrotic. Surgical reconstruction is only recommended during the latter established phase. There are a variety of options when erections are functional. However, when erectile dysfunction is present, the gold standard treatment is the placement of an inflatable penile prosthesis with or without additional straightening procedures. General recommendations include that after implanting and inflating the cylinders, if a clinically significant curvature is present, manual modeling is performed. If a residual curve >30° remains after modeling, then various techniques, including plaque releasing incision, is the next step. Grafting can be considered if tunical defects are >2.0 cm. Causes of corporal fibrosis include complications from an infected implant such as explantation, priapism, penile trauma, and prolonged use of an intracavernosal injection agent. Implant placement in the setting of corporal fibrosis can be technically challenging. Available strategies include incision or excision of the scar, corporotomies with or without grafting, the use of cavernotomes, or other specialized dilators, implant downsizing, and transcorporeal resection.

One-Dimensional Molecular Crystal of Phthalocyanine Confined into Single-Walled Carbon Nanotubes

New one-dimensional (1D) hybrid nanosystems are elaborated with metalated or metal free phthalocyanine molecules encapsulated into the hollow core of single-walled carbon nanotubes. The X-ray diffraction experiments coupled to simulation allow evidencing the 1D structural organization of the molecules inside the nanotubes. The angle between the molecule ring and the nanotube axis is close to 32° as determined from our density functional theory calculations. Confined molecules display Raman spectra hardly altered with respect to the bulk phase, suggesting a rather weak interaction with the tubes. For comparison, noncovalent functionalization at the outer surface of the tube is also investigated. The vibrational properties of the molecules functionalized at the outer surface of tubes display important modifications. A significant curvature of the phthalocyanine is induced by the interaction with the tube walls, leading to change of the central atom position within the molecular ring, in good agreement with our first-principles calculations.

Stabilized quasi-Newton optimization of noisy potential energy surfaces.

Optimizations of atomic positions belong to the most commonly performed tasks in electronic structure calculations. Many simulations like global minimum searches or characterizations of chemical reactions require performing hundreds or thousands of minimizations or saddle computations. To automatize these tasks, optimization algorithms must not only be efficient but also very reliable. Unfortunately, computational noise in forces and energies is inherent to electronic structure codes. This computational noise poses a severe problem to the stability of efficient optimization methods like the limited-memory Broyden-Fletcher-Goldfarb-Shanno algorithm. We here present a technique that allows obtaining significant curvature information of noisy potential energy surfaces. We use this technique to construct both, a stabilized quasi-Newton minimization method and a stabilized quasi-Newton saddle finding approach. We demonstrate with the help of benchmarks that both the minimizer and the saddle finding approach are superior to comparable existing methods.

FERMIMONITORING OF RADIO-LOUD NARROW-LINE SEYFERT 1 GALAXIES

We present detailed analysis of the gamma-ray flux variability and spectral properties of the five radio-loud narrow line Seyfert 1 (RL-NLSy1) galaxies, detected by the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope, namely 1H 0323+342, SBS 0846+513, PMN J0948+0022, PKS 1502+036, and PKS 2004$-$447. The first three sources show significant flux variations including the rapid variability of a few hours by 1H 0323+342. The average gamma-ray spectrum of 1H 0323+342 and PMN J0948+0022 shows deviation from a simple power law (PL) behavior, whereas for other three sources, PL model gives better fit. The spectra of 1H 0323+342, SBS 0846+513, and PMN J0948+0022, respectively in low, flaring, and moderately active states, show significant curvature. Such curvature in the gamma-ray spectrum of 1H 0323+342 and PMN J0948+0022 can be due to emission region located inside the broad line region (BLR) where the primary mechanism of the gamma-ray emission is inverse-Compton (IC) scattering of BLR photons occurring in the Klein-Nishina regime. The gamma-ray emission of SBS 0846+513 is explained by IC scattering of dusty torus photons which puts the emission region to be outside the BLR and thus under the Thomson regime. Therefore, the observed curvature of SBS 0846+513 could be intrinsic to the particle energy distribution. The presence of curvature in the gamma-ray spectrum and flux variability amplitudes of some of the RL-NLSy1 galaxies suggest that these sources could be akin to low/moderate jet power flat spectrum radio quasars.

Thin film properties of tetracyanoquinodimethane (TCNQ) with novel templating effects

Film properties and new templating behaviours in strong electron acceptor TCNQ.

A Rare Consequence of Chronic Graft Versus Host Disease - Peyronie's Disease.

Chronic graft versus host disease (GvHD) after allogeneic stem cell transplantation (SCT) may involve any organ system, but male genital involvement is rare. Peyronie's Disease (PD) is an acquired, localized fibrotic disorder of the tunica albuginea, which leads to penile deformity, pain, and eventually to erectile dysfunction. We report the case of a 52 year old African American male with Acute Myeloid Leukemia who underwent human leucocyte antigen (HLA) matched sibling allogeneic peripheral blood SCT. His post transplant course was complicated by development of acute and multi-organ chronic GvHD requiring prolonged immunosuppression. He developed progressive dorsal curvature of the penis with erections within 1 year of ultra low dose interleukin -2 (IL2) treatment for his chronic GvHD but concealed symptoms for several months. Color Doppler Duplex ultrasound evaluation of the erect penis revealed a 75-degree curvature and appropriate hemodynamic response to prostaglandin injection. He underwent successful incision and grafting of the penile plaque. There is no significant residual curvature and is now able to engage in intercourse. A strong temporal association between GVHD (or its treatment) and Peyronie's is documented here. Awareness of the possible link between PD and chronic GVHD is required in this era of rapid growth in numbers of SCT.

High-velocity Wind from IRS 1 in the NGC 2071IR

AbstractWe present the results of 1.3 and 3.6 cm radio continuum emission toward the NGC 2071IR star-forming region, carried out with the VLA in its A configuration. We detect continuum emission toward the infrared sources IRS 1 and IRS 3 at both wavelengths. In particular, IRS 1 breaks up into three continuum peaks (IRS 1E, 1C, and 1W), aligned in the east-west direction, being IRS 1 the central source. The morphology of the condensation IRS 1W is very interesting, which has an elongated structure and shows a significant curvature towards the north. We suggest that this morphology could be explained as the impact of a high-velocity wind or jetlike outflow from IRS 1 on a close companion or other obstruction, which also explains the strong water maser emission observed toward IRS 1W.

Cyclogenesis Downstream of Extratropical Transition Analyzed by Q-Vector Partitioning Based on Flow Geometry

Abstract During extratropical transition (ET), tropical cyclones exert a significant impact on the midlatitude circulation. Archetypical features of this impact are jet streak formation, amplification of the downstream trough, and modification of the associated downstream cyclogenesis. This study investigates the relative importance of the jet streak and the upper-level trough for cyclone development by quantifying the respective contributions to midtropospheric vertical motion using the Q-vector partitioning by J. C. Jusem and R. Atlas. Their framework is here extended from quasigeostrophic theory to alternative balance. The Q vector under alternative balance involves the nondivergent wind, instead of the geostrophic wind, and therefore represents more accurately the balanced dynamics associated with vertical motion, in particular downstream of ET where the flow often exhibits significant curvature associated with the amplified trough. An idealized ET scenario and three real cases, the cyclones downstream of Hanna (2008), Choi-wan (2008), and Jangmi (2009), are analyzed. In all cases, the trough plays a prominent role in cyclone development. The jet streak plays a prominent, favorable role in the idealized ET scenario and downstream of Hanna. In contrast, the role of the jet streak downstream of Choi-wan is clearly of secondary importance. Interestingly, downstream of Jangmi the jet streak has a prominent but detrimental impact. It is concluded that amplified jet streaks associated with ET have the potential to be of significant importance for downstream cyclone development. The few cases considered in this study, however, point to a large case-to-case variability of the role of the jet streak.

Population dynamics of redbay (Persea borbonia) after laurel wilt disease: an assessment based on forest inventory and analysis data

Laurel wilt disease (LWD) is a lethal fungal infection of woody plants in the Lauraceae, including redbay (Persea borbonia). We used forest inventory and analysis (FIA) data from 2003 to 2011 to estimate redbay populations and see if any decline could be observed since the introduction of LWD. Throughout its entire range, the population estimate of redbay was about 862.2 ± 89.8 million in 2003, increasing to 951.8 ± 87.1 million in 2011. However, population estimates from 2003 to 2011 displayed a significant negative curvature, suggesting that the population might start to decline. The population in Georgia significantly decreased from 241.1 ± 11.9 million stems in 2003 to 150.3 ± 7.9 million in 2011. Results at the range-wide scale should be taken with caution, since the FIA estimates are based on a 5-year moving average. However, we show that the FIA data can also be used on a smaller scale. Redbay densities decreased significantly in plots surveyed before and after the reported infection by an average of 89.6 live redbay stems/ha. Density in plots without reported LWD were not statistically different between survey years. We developed a logistic regression model to predict the probability of redbay mortality due to LWD. Number of years since LWD infection was the most significant variable, with every increase in 1 year resulting in a 153.7 % increase in odds of death. Diameter was also a significant predictor, with an increase of 1 cm DBH resulting in a 5.0 % increase in odds of death.

DECOMPOSING 3D OBJECTS IN SIMPLE PARTS CHARACTERIZED BY RECTILINEAR SPINES

The distance labeled curve skeleton of a 3D object is used to guide the decomposition of the object into disjoint parts. To this aim, the skeleton is polygonally approximated by taking into account spatial coordinates and distance values of its voxels. The obtained skeleton segments are characterized by the absence of significant changes of curvature. Moreover, along each skeleton segment distance values are constant or show a linearly changing trend. Each segment can be interpreted as the spine of a simple part, which is characterized by the absence of significant curvature changes along its boundary, and by local thickness that is constant or evolves linearly along the part. By using exclusively the spatial coordinates and distance values of the vertices of the spines, quantitative information on shape, size, position and orientation of the corresponding simple parts can be obtained. Alternative decompositions of the object can be computed by selecting different values for the threshold used during polygonal approximation of the skeleton. Some criteria are also discussed for the selection of optimal threshold values originating approximated skeletons having a small number of segments, but still producing decompositions rather well adapting the input object boundary.

Degradation of burazol blue ED by heterogeneous fenton process: simultaneous optimization by central composite design

This work is an application of the response surface methodology (RSM) to determine the effects of operational parameters on the heterogeneous Fenton-type oxidation of the burazol blue ED (BB). The study was conducted using a Fe (III) sepiolite catalyst in the presence of hydrogen peroxide (H2O2) in a batch process. The effects of operational parameters such as the pH of the reaction, catalyst concentration, stirring speed, and reaction time were examined under the following conditions: a temperature of 25°C, 100 ppm initial dye concentration, and 0.5 mM H2O2 concentration. Because of the significant curvature effect, central composite design (CCD) was preferred to full-factorial experimental design for the simultaneous optimization of color and chemical oxygen demand (COD) removals. Optimized reaction conditions were established as pH 2, 1 g/250 mL catalyst dose, 250-rpm stirring speed, and 60-min reaction time. Contour plots and a desirability function were used to find the local points of optimization. After conformation, under the optimized reaction conditions, 96% color and 75% COD removals were obtained experimentally. These values were in the prediction interval and were in agreement with the quadratic polynomial model predictions.

The origin of noise and magnetic hysteresis in crystalline permalloy ring-core fluxgate sensors

Abstract. Developed in the 1960s for use in high-performance ring-core fluxgate sensors, 6–81.3 Mo permalloy remains the state of the art for permalloy-cored fluxgate magnetometers. The magnetic properties of 6–81.3, namely magnetocrystalline and magnetoelastic anisotropies and saturation induction, are all optimum in the Fe–Ni–Mo system. In such polycrystalline permalloy fluxgate sensors, a single phenomenon may cause both fluxgate noise and magnetic hysteresis; explain Barkhausen jumps, remanence and coercivity; and avoid domain denucleation. This phenomenon, domain wall reconnection, is presented as part of a theoretical model. In the unmagnetized state a coarse-grain high-quality permalloy foil ideally forms stripe domains, which present at the free surface as parallel, uniformly spaced domain walls that cross the entire thickness of the foil. Leakage flux "in" and "out" of alternating domains is a requirement of the random orientation, grain by grain, of magnetic easy axes' angles with respect to the foil free surface. Its magnetostatic energy together with domain wall energy determines an energy budget to be minimized. Throughout the magnetization cycle the free-surface domain pattern remains essentially unchanged, due to the magnetostatic energy cost such a change would elicit. Thus domain walls are "pinned" to free surfaces. Driven to saturation, domain walls first bulge then reconnect via Barkhausen jumps to form a new domain configuration that I have called "channel domains", which are attached to free surfaces. The approach to saturation now continues as reversible channel domain compression. Driving the permalloy deeper into saturation compresses the channel domains to arbitrarily small thickness, but will not cause them to denucleate. Returning from saturation the channel domain structure will survive through zero H, thus explaining remanence. The Barkhausen jumps, being irreversible exothermic events, are sources of fluxgate noise powered by the energy available from domain wall reconnection. A simplified domain energy model can then provide a predictive relation between ring-core magnetic properties and fluxgate sensor noise power. Four properties are predicted to affect noise power, two of which are well known: saturation total magnetic flux density and magnetic anisotropy. The two additional properties are easy axes alignment and foil thickness. Flux density and magnetic anisotropy are primary magnetic properties determined by an alloy's chemistry and crystalline lattice properties. Easy axes alignment and foil thickness are secondary, geometrical properties related to an alloy's polycrystalline fabric and manufacture. Improvements to fluxgate noise performance can in principle be achieved by optimizing any of these four properties in such a way as to minimize magnetostatic energy. Fluxgate signal power is proportional to B − H loop curvature [d2B/dH2]. The degree to which Barkhausen jumps coincide with loop curvature is a measure of noise that accompanies the fluxgate signal. B − H loops with significant curvature beyond the open hysteresis loop may be used to advantage to acquire the fluxgate signal with reduced noise.

Shock wave–boundary layer interactions in rectangular inlets: three-dimensional separation topology and critical points

AbstractThe interaction between two separated flow regions was studied for the fundamental problem of a shock wave–boundary layer interaction (SBLI) within a rectangular inlet. One motivation is that the inlet of an engine on a supersonic aircraft may contain separation zones on the sidewalls and the bottom wall; if one region separates first it can alter the flow on the other wall and lead to engine unstart. In our work an oblique shock wave was generated by a wedge suspended from the upper wall of a Mach 2.75 wind tunnel. Stereo particle image velocimetry (PIV) measurements were recorded in 25 planes that include all three possible orthogonal orientations. The lateral velocity and vorticity measurements help to explain the underlying flow structure and these quantities were not measured previously for this problem. It is concluded that the sidewall and bottom wall separation zones interact due to an underlying flow structure that is similar to the two types of 3-D separation patterns previously described by Tobak & Peake (Annu. Rev. Fluid Mech., vol. 14, 1982, pp. 61–85). Separation first occurs at an upstream location where the shock interacts with the sidewall. Lateral velocities direct flow toward the centreline to cause separation on the bottom wall. This causes significant curvature of the shock wave, so that even the region near the tunnel centreline cannot be explained by conventional 2-D concepts. A number of critical points (saddle points, nodes, focus points) were identified. Results are consistent with the general ideas of Burton & Babinsky (J. Fluid Mech., vol. 707, 2012, pp. 287–306) and help to provide details of how the sidewalls redistribute the adverse pressure gradient in space.

Steady spatially-periodic eutectic growth with the effect of triple point in directional solidification

The present paper investigates steady spatially periodic eutectic growth during directional solidification with isotropic surface tension in terms of analytical approach. We consider the case when the Péclet number ∊ is small and the segregation coefficient κ is close to unit, and obtain a family of the global, steady-state solutions with two free parameters: the tilt angle φ and the Péclet number ∊. The corresponding interfacial patterns of the steady states are spatially periodic, and may be tilted or non-tilted. The results show that near the triple point, there is a boundary layer O∊12 thick, where the isotropic surface tension plays a significant role, the slope and curvature of interface may be very large and the undercooling temperatures of interface may have a noticeable non-uniformity. Quantitative comparisons between theoretical predictions and recent experimental data are made without making any adjustments to parameters, and show good agreement.

Systematic effects on the size–luminosity relations of early- and late-type galaxies: dependence on model fitting and morphology

We quantify the systematics in the size–luminosity relation of galaxies in the Sloan Digital Sky Survey main sample (i.e. at z ∼ 0.1) which arise from fitting different one- and two-component model profiles to the r-band images. For objects brighter than L_*, fitting a single Sersic profile to what is really a two-component SerExp system leads to biases: the half-light radius is increasingly overestimated as n of the fitted single component increases; it is also overestimated at B/T ∼ 0.6. For such objects, the assumption of a single Sersic component is particularly misleading. However, the net effect on the R-L relation is small, except for the most luminous tail. We then study how this relation depends on morphology. Our analysis is one of the first to use Bayesian-classifier-derived weights, rather than hard cuts, to define morphology. For the R-L relation Es, S0s and Sas are early types, whereas Sbs and Scds are late, although S0s tend to be 15 per cent smaller than Es of the same luminosity, and faint Sbs are more than 25 per cent smaller than faint Scds. Neither the early- nor the late-type relations are pure power laws: both show significant curvature, which we quantify. This curvature confirms that two mass scales are special for both early- and late-type galaxies: M_* ∼ 3 × 10^10 and 2 × 10^11 M_⊙. Also, although the R_disc-L_disc and R_disc-M_*disc relations of discs of disc-dominated galaxies run parallel to the corresponding relations for the total light in late types (i.e. they are significantly curved), R_bulge-L_bulge and R_bulge-M_*bulge for bulge-dominated systems show almost no curvature (i.e. unlike for the total light of early-type galaxies). Finally, the intrinsic scatter in the R-L relation decreases at large L and/or M_* and should provide additional constraints on models of how the most massive galaxies formed.