Conical End Research Articles

Numerical investigation on the characteristics of coolant flow, heat absorption and phase change in transpiration cooling process

Transpiration cooling using liquid water as coolant has been confirmed as a promising thermal protection method due to the huge phase change latent heat. A multi-region numerical strategy is developed and presented in this paper, to simulate directly the liquid transpiration cooling process within a wedge-shaped porous cone. An experiment was conducted to validate the numerical strategy. Using the validated strategy, five series of numerical simulations under different coolant mass fluxes were carried out. The numerical results revealed some interesting and valuable characteristics of fluid flow, heat absorption and phase change of liquid coolant in the porous cone and on the impermeable surface. When the liquid coolant is vaporized incompletely in the porous region, one can find two interesting phenomena: 1) A large amount of coolant flow towards the end of the porous cone, while only a small part of coolant can be transferred into the leading edge region; 2) An increase in inlet coolant mass flux causes a decrease of the coolant ejected from the leading edge. However, these phenomena are absent when the liquid coolant is vaporized completely in porous region. Another important phenomenon demonstrated in this work is an additional thermal protection effect on the downstream impermeable surface. This additional thermal protection effect increases with the inlet coolant mass flux, but at the price of a larger wastage of coolant phase change latent heat.

New Host and Locality Record of Parapharyngodon Japonicus (Nematoda: Oxyuroidea) from the Egyptian Changeable Lizard Agama Mutabilis (Agamidae): A Light and Scanning Electron Microscopy.

SummaryParapharyngodon (Oxyurida) is a lizard gastrointestinal nematode parasite with a life cycle including lizards as main hosts. However, some species are known to parasitize anurans. In the present study, P. japonicus isolated from the large intestine of the Egyptian changeable lizard, Agama mutabilis was described and illustrated. Forty five specimens of these animals were collected from south Sinai desert, Egypt during the period from May to September 2017. After necropsy, the body was opened by a longitudinal incision from vent to throat, and the gastrointestinal tract was removed. The esophagus, stomach, small and large intestines were examined separately for helminthes. The recovered nematodes were examined by light and scanning electron microscopy. Thirty six specimens (80.0 %) were found to be naturally infected. The parasite was robust with prominent cuticular transverse annulations. Mouth surrounded by three bilobed lips, each with tiny labial papillae. Three pairs of caudal papillae were observed in male worms; 1 pair precloacal, 1 pair sublateral in cloacal opening line, 1 pair in proximal region of caudal appendage on its narrowed point. The posterior extremity beard dorsally directed caudal appendages. Females were with a conical posterior end terminated at a terminal spike. Ovaries reached esophageal isthmus but not wrapped around corpus. The parasite recorded was compared morphologically and morphometrically with the most similar species, it was found that it was most similar to P. japonicus with new host and locality records.

A Leaky Dielectric Drop with Conical Ends in An Electric Field

There has long been interest in the existence of stationary shapes with conical ends for drops freely suspended in an ambient fluid and subjected to a uniform electric field. If the two phases are ...

Index estimate of self-shrinkers in $\mathbb {R}^3$ with asymptotically conical ends

Index estimate of self-shrinkers in $\mathbb {R}^3$ with asymptotically conical ends

Cheeger–Müller theorem on manifolds with cusps

We prove equality between the renormalized Ray–Singer analytic torsion and the intersection R-torsion on a Witt-manifold with cusps, up to an error term determined explicitly by the Betti numbers of the cross section of the cusp and the intersection R-torsion of a model cone. In the first step of the proof we compute explicitly the renormalized Ray–Singer analytic torsion of a model cusp in general dimension and without the Witt-condition. In the second step we establish a gluing formula for renormalized Ray–Singer analytic torsion on a general class of non-compact manifolds in any dimension that includes Witt-manifolds with cusps, but also scattering manifolds with asymptotically conical ends. In the final step, a Cheeger–Muller theorem on cusps follows by a combination of the previous explicit computation and the gluing formula.

Mechanical micro-texturing of Ti-6Al-4V surfaces for improved wettability and bio-tribological performances

The present work focuses on the improvement in wettability and bio-tribological performance of Ti-6Al-4V titanium alloy using mechanically micro-textured surfaces. Three types of mechanical micro-tools, namely, micro flat-end mill, micro ball-end mill and micro-drill having equal diameter of 200 μm each, are used to fabricate circular micro-dimples with flat, semi-hemispherical and conical end geometries, respectively, on Ti-6Al-4V surface. The effects of micro-textured geometries on surface roughness, microhardness, surface wettability and coefficient of friction (COF) are estimated. Surface wettability is measured in terms of pure water contact angle, whereas, COF is estimated under in vitro condition of a hip joint prosthesis. Among different micro-dimpled surfaces, semi-hemispherical end micro-dimpled surface is found to be more suitable for hip joint prosthesis due to its extremely good surface wettability and lower COF. Results of this study also indicate that the mechanical micromachining processes are efficient methods for the fabrication of functional surfaces on titanium alloys and similar biomaterials.

Moduli spaces of meromorphic functions and determinant of the Laplacian

The Hurwitz space is the moduli space of pairs $(X,f)$ where $X$ is a compact Riemann surface and $f$ is a meromorphic function on $X$. We study the Laplace operator $\Delta^{|df|^2}$ of the flat singular Riemannian manifold $(X,|df|^2)$. We define a regularized determinant for $\Delta^{|df|^2}$ and study it as a functional on the Hurwitz space. We prove that this functional is related to a system of PDE which admits explicit integration. This leads to an explicit expression for the determinant of the Laplace operator in terms of the basic objects on the underlying Riemann surface (the prime form, theta-functions, the canonical meromorphic bidifferential) and the divisor of the meromorphic differential $df$. The proof has several parts that can be of independent interest. As an important intermediate result we prove a decomposition formula of the type of Burghelea-Friedlander-Kappeler for the determinant of the Laplace operator on flat surfaces with conical singularities and Euclidean or conical ends. We introduce and study the $S$-matrix, $S(\lambda)$, of a surface with conical singularities as a function of the spectral parameter $\lambda$ and relate its behavior at $\lambda=0$ with the Schiffer projective connection on the Riemann surface $X$. We also prove variational formulas for eigenvalues of the Laplace operator of a compact surface with conical singularities when the latter move.

Prediction of oxygen mass transfer of plunging hollow jets using regression models

Jet aerator finds an essential application in the treatment of liquid wastes by increasing the microbial activity and decomposition of organic matter into liquid waste. Diverging plunging jet emitted from the conical end of hollow jet aerators enhances the surface disturbances to a large extent and signifies its usefulness in gas mass transfer and liquid mixing applications. The present study’s focus is on the application of soft computing approaches in estimating oxygen mass transfer by plunging hollow jets. The data observed experimentally from the oxygen transfer study conducted on hollow jet aerators having jet angles of 30°, 45° and 60° are used for modelling. The efficacy of Support Vector Machines (SVM) regression, M5 tree and multiple nonlinear regression is explored with both dimensional and non-dimensional data-sets. SVM regression approach (with RBF and PUK as kernel functions) is observed to be more accurate than M5 tree and multiple non-linear regression methods. The evaluation of the results using all the computing techniques tested indicates the improved performance using non-dimensional data-set as compared to dimensional data-set. Moreover, a parametric study based on SVM modelling is conducted to analyse the influence of jet parameters on the prediction of oxygen transfer.

Safety and Functionality of a Guidewire Fixator: Clinical Investigation of a New Endovascular Tool.

A new endovascular tool, the Liungman Guidewire Fixator, has been developed to simplify endovascular treatment in complex aortic aneurysms. The device has been extensively tested in bench models and animal trials. To verify the safety and functionality demonstrated in the porcine model, the device was tested in ten patients undergoing endovascular aortic repair (EVAR) or fenestrated endovascular aortic repair (f-EVAR) treatment for abdominal aortic aneurysm. The Liungman Guidewire Fixator consists of a braided stent-like, cylindrical structure with conical ends and a central channel for a 0.035″ guidewire. When in use, it is slid along the guidewire and positioned in the target artery, where the Liungman Guidewire Fixator interacts with the arterial wall by anchoring the guidewire to the wall through a radial force. The Liungman Guidewire Fixator allows for uninterrupted blood flow passed the point of fixation. In this study, the Liungman Guidewire Fixator was tested in ten patients undergoing EVAR or f-EVAR treatment for abdominal aortic aneurysm. The device was deployed and retrieved crossover into the hypogastric artery, and the occurrence of thrombotic occlusion, arterial dissection, and vascular rupture or trauma was studied using angiography, as well as device ability to withstand guidewire tension. There were no instances of occlusion, dissection, or vascular trauma detected using angiography. In all cases, deployment and retrieval were successful, and the devices could withstand an applied tension of 3 N. In one instance, retrieval was challenging because of significant tortuosity, which was resolved by a coaxial catheterization. Deployment was uneventful in all ten patients. Retrieval according to the intended instruction for use was performed in nine of the patients. In one patient, a coaxial catheterization was necessary. All devices withstood a retention force of 3 N.

The role of surface charge convection in the electrohydrodynamics and breakup of prolate drops

The deformation of a weakly conducting, ‘leaky dielectric’, drop in a density matched, immiscible weakly conducting medium under a uniform direct current (DC) electric field is quantified computationally. We exclusively consider prolate drops, for which the drop elongates in the direction of the applied field. Furthermore, for the majority of this study, we assume the drop and medium to have equal viscosities. Using axisymmetric boundary integral computations, we delineate drop deformation and breakup regimes in the $Ca_{E}-Re_{E}$ parameter space, where $Ca_{E}$ is the electric capillary number (ratio of the electric to capillary stresses); and $Re_{E}$ is the electric Reynolds number (ratio of charge relaxation to flow time scales), which characterizes the strength of surface charge convection along the interface. For so-called ‘prolate A’ drops, where the surface charge is convected towards the ‘poles’ of the drop, we demonstrate that increasing $Re_{E}$ reduces the critical capillary number for breakup. Moreover, surface charge convection is the cause of an abrupt transition in the breakup mode of a drop from end pinching, where the drop elongates and develops bulbs at its ends that eventually detach, to a breakup mode characterized by the formation of conical ends. On the contrary, the deformation of ‘prolate B’ drops, where the surface charge is convected away from the poles, is essentially unaffected by the magnitude of $Re_{E}$.

Dispersion of near-infrared laser energy through radicular dentine when using plain or conical tips.

The aim of this study was to investigate the influence of tip design on patterns of laser energy dispersion through the dentine of tooth roots when using near-infrared diode lasers. Diode laser emissions of 810 or 940nm were used in combination with optical fiber tips with either conventional plain ends or conical ends, to irradiate tooth roots of oval or round cross-sectional shapes. The lasers were operated in continuous wave mode at 0.5W for 5s with the distal end of the fiber tip placed in the apical or coronal third of the root canal at preset positions. Laser light exiting through the roots and apical foramen was imaged, and the extent of lateral spread calculated. There was a significant difference in infrared light exiting the root canal apex between plain and conical fiber tips for both laser wavelengths, with more forward transmission of laser energy through the apex for plain tips. For both laser wavelengths, there were no significant differences in emission patterns when the variable of canal shape was used and all other variables were kept the same (plain vs conical tip, tip position). To ensure optimal treatment effect and to prevent the risks of inadvertent laser effects on the adjacent periapical tissues, it is important to have a good understanding of laser transmission characteristics of the root canal and root dentine. Importantly, it is also essential to understand transmission characteristics of plain and conical fibers tips.

Thermal stress analysis on 2D C/SiC composites of thin-walled structure of anti-heat head cone

The thermal protection performance of C/SiC composites can be improved by coating the thermal barrier coating on the surface of C/SiC composites.The wall heat flux density distribution of the 2D C/SiC composite thermal insulation structure at the front end of the hyper-sonic vehicle was calculated by steady state heat transfer at different Mach numbers in the atmosphere. In the thermal stress calculation, an effective finite element numerical model is established by the method of partitioning and based on the flexible gradient density method. The model was treated as heterogeneous materials which consists of C/SiC composite region, the coating zone and transition zone, and the results show that the maximum thermal stress appears near the end of the head cone.

Method and technology of delivering optical radiation to biological micro-objects

Subject of Research. We propose a method and technology of delivering optical radiation to biological single micro-objects at wavelength equal to 650 nm. The delivering optical radiation is implemented by a fiber optic system that is a standard optical fiber with a reduced diameter at the output end (cone optical fiber, or fiber optic taper). Method. The method essence appears as the creation of a fiber optic system for delivering optical radiation. A sampling method of fiber optic tapers by a fusion splicer for optical fibers is proposed in this paper. The process of protective coating formation, opaque to optical radiation exiting through the side surface of the fiber taper, is described. The end of the fiber optic taper is prepared to obtain a uniform intensity distribution of the outgoing optical radiation. The study of the divergence of optical radiation exiting from the taper end is carried out. Main Results. The proposed method has enabled creation of a fiber-optic taper with a waist diameter of 15±5 μm. The carried out study of optical radiation divergence has shown that the field diameter at a distance of not more than 200 μm to the micro-object is approximately 19 μm and does not exceed the taper waist diameter. Practical Relevance. Unlike other existing methods of delivering optical radiation, a fiber taper with a waist diameter of 15 ± 5 μm provides an impact not only on individual cells but also specific regions of cells with the size that exceeds the taper waist diameter. With the help of the manipulator, the end of the fiber taper can be placed into the required area without overlapping the object to the required distance directly in the environment where biological objects are located (cell cultures).

Existence of self-shrinkers to the degree-one curvature flow with a rotationally symmetric conical end

Given a smooth, symmetric, homogeneous of degree one function f(λ1,⋯,λn) satisfying ∂if>0 for all i=1,⋯,n, and a rotationally symmetric cone C in Rn+1, we show that there is a f self-shrinker (i.e. a hypersurface Σ in Rn+1 which satisfies f(κ1,⋯,κn)+12X⋅N=0, where X is the position vector, N is the unit normal vector, and κ1,⋯,κn are principal curvatures of Σ) that is asymptotic to C at infinity.

EFFECT OF ATOMIZER INTERNAL GEOMETRY ON THE INTERNAL AND EXTERNAL TWO-PHASE FLOW IN EFFERVESCENT ATOMIZATION

An experimental study was conducted to study the internal and external two-phase flow in an effervescent atomizer using high-speed imaging. The impact of the aerator tube configuration and mixing zone length on the size of bubbles inside the mixing zone and the spray droplet characteristics at different gas-to-liquid flow rates ratios were studied. An aerator tube with the conical end base was manufactured and tested. It is observed that the separation bubble at the trailing edge is suppressed by this configuration, which resulted in more uniform and smaller bubbles compared to the standard aerator tube with a flat base. The length of the mixing zone was found to have an impact on the bubble size distribution inside the mixing zone; more uniform and smaller bubbles are generated in the shorter mixing zone. The mixing zone length, however, does not show a distinct impact on the droplet velocity and size. It is concluded that a conical base aerator tube and a shorter mixing zone could significantly improve the spray steadiness and the atomization process.

Description of two new species of Seinura Fuchs, 1931 (Nematoda: Aphelenchoididae) from Iran.

Two new species of Seinura are described and illustrated using both morphological and molecular characters. Seinura persica n. sp. is characterized by having females with a distinct cephalic region, stylet 19.5 (18-20) μm long, four incisures in the lateral fields, position of excretory pore anterior to the base of metacorpus, post-uterine sac 54.8 (50-60) μm long, and an elongate-conoid tail with a shallow depression on the dorsal side ending in a sharply pointed tip. Males have body length of 467 and 592 μm, spicules 15 and 16 μm long with a prominent triangular-shaped rostrum, developed condylus and no cucullus. Seinura hyrcania n. sp. is characterized by having an offset lip region, stylet 21.5 (18-24) μm long, three incisures in the lateral fields, excretory pore anterior to the base of the metacorpus, post-uterine sac 19 (12-25) μm long and conical tail ending in a filiform terminus. Morphological and morphometric diagnostic characters together with molecular data based on partial sequences of SSU and LSU of the ribosomal DNA gene are provided for these new species.

The angular distribution at the outlet of a capillary in a wide range of rarefaction

The angular distribution at the outlet of a capillary is an important topic in rarefied gas dynamics. Here the procedure to calculate the near field angular distribution based on velocity distribution function or DSMC (Direct Simulation Monte Carlo) method was proposed. Then, the angular distribution at the outlet of cylindrical capillary was evaluated with different rarefaction parameter δ using DSMC method with open source solver dsmcFoam. The results showed that the normalized flux intensity at small polar angle decreased with δ when δ was smaller than 10, and the distribution did not approximate the cosine distribution when δ at the inlet was large enough. Besides, capillary with conical end was also evaluated. The results showed that the conical end could decrease the divergence of the beam even δ at the inlet increased to 50 when the outlet was set as vacuum. Last, the influence of CL (Cercignani Lampis) accommodation coefficients and VSS (Variable Soft Sphere) parameters on the angular distribution was studied.

Description of Cryptaphelenchus iranicus n. sp. (Nematoda: Ektaphelenchinae) recovered from bark samples of Pinus nigra from Iran.

Cryptaphelenchus iranicus n. sp., recovered from bark and wood samples of a weakened Pinus nigra in Kermanshah Province, western Iran, is described. The new species has females with body length of 250-330 µm and males 230-275 µm long, lip region set-off from body contour, 7-8 μm long stylet with small basal swellings, excretory pore located at 1.5-2.0 body diam. posterior to median bulb, post-vulval uterine sac short, 7-10 µm long and conical female posterior body end (tail) ending to a pointed tip. Males of the new species have seven (1+2+2+2) caudal papillae and a short mucro at tail tip. Based on morphological characters, the new species is close to C. cirrus, C. latus and C. leptocaudus. Phylogenetic analyses using the D2/D3 fragment of 28S rDNA show the new species forming a clade with other Cryptaphelenchus species with maximal (1.00) Bayesian posterior probability (BPP) in Bayesian inference and 100% bootstrap value (BS) in the maximum likelihood method. The Cryptaphelenchus clade forms a monophyletic group with members of subfamily Ektaphelenchinae.

Ultrastructure and Morphology of Compound Eyes of the Scorpionfly Panorpa dubia (Insecta: Mecoptera: Panorpidae).

Mecoptera are unique in holometabolous insects in that their larvae have compound eyes. In the present study the cellular organisation and morphology of the compound eyes of adult individuals of the scorpionfly Panorpa dubia in Mecoptera were investigated by light, scanning electron, and transmission electron microscopy. The results showed that the compound eyes of adult P. dubia are of the apposition type, each eye comprising more than 1200 ommatidia. The ommatidium consists of a cornea, a crystalline cone made up of four cone cells, eight photoreceptors, two primary pigment cells, and 18 secondary pigment cells. The adult ommatidium has a fused rhabdom with eight photoreceptors. Seven photoreceptors extend from the proximal end of the crystalline cone to the basal matrix, whereas the eighth photoreceptor is shorter, extending from the middle level of the photoreceptor cluster to the basal matrix. The fused rhabdom is composed of the rhabdomeres of different photoreceptors at different levels. The adult ommatidia have the same cellular components as the larval ommatidia, but the tiering scheme is different.

Buckling of externally pressurized steel toriconical shells

The inclusion of toroidal (knuckle) segment between cylinder and conical vessel end closure is a natural way for diffusing the stress jump at the junction. But there is very little experimental data in support of the knuckle’s role and its influence. Hence eight steel toriconical shells have been buckled by quasi-static external pressure in order to measure this problem. Diameter of all models was 200 mm at the base and their wall thickness was 2 mm. The apex semi-angle was 45 deg for all shells. Experimental buckling pressures varied from 3.9 MPa to 4.4 MPa despite large variations in shape. Comparisons of experimental failure pressures with numerical predictions based on several approaches to modelisation are given. The latter are based on axisymmetric modelling as well as on measured geometry and wall thickness. The ratio of experimental to numerical failure loads varies from 1.05 to 1.16.