Slender Surface Research Articles

Nonlinear thermal radiation in flow induced by a slendering surface accounting thermophoresis and Brownian diffusion

.Our attention here in this research is on scrutinizing the nonlinear convection characteristics in a flow induced by a slendering surface. Flow expression is developed through electrically conducting Williamson nanomaterial. Nonlinear forms of stretching and free stream velocities are imposed. Consideration of nonlinear thermal radiation, non-uniform heat generation/absorption, Joule and convective heating aspects describe the phenomenon of heat transfer. The zero-mass condition for concentration is also considered. The compatible transformations produce strong nonlinear differential systems. The problems are computed analytically utilizing the bvp4c procedure. Heat transfer rate and drag force are also explained for various physical variables. Our analysis reveals that the heat transfer rate augments via larger radiation parameter and Biot number. Moreover, larger Brownian motion and thermophoresis parameters have opposite characteristics on concentration field. For the verification of the present findings, the results of the presented analysis have been compared with the available works in particular situations and reasonable agreement is noted.

On Cattaneo–Christov heat flux model for Carreau fluid flow over a slendering sheet

The underlying intentions of this article are to investigate the impact of non-Fourier heat flux model on the stagnation-point flow of non-Newtonian Carreau fluid. In this study, the innovative Cattaneo–Christov constitutive model is introduced to study the characteristics of thermal relaxation time. The flow is impelled by a slendering surface which is of the variable thickness. In the model, the physical mechanism responsible for homogeneous–heterogeneous reactions are further taken into account. Also, the diffusion coefficients of the reactant and auto catalyst are considered to be equal. The governing non-linear partial differential equations consisting of the momentum, energy and concentration equations are reduced to the coupled ordinary differential equations by means of local similarity transformations. The transformed ODEs are tackled numerically by employing an effective shooting algorithm along with the Runge–Kutta Fehlberg scheme. The physical characteristics of the fluid velocity, temperature and concentration profiles are illuminated with the variation of numerous governing factors and are presented graphically. For instance, our result indicates that the temperature and thermal boundary layer thickness are lower in case of Cattaneo–Christov heat flux model when compared to classical Fourier’s heat model. Meanwhile, the rate of heat transfer is significantly improved by a high wall thickness parameter and an opposite influence is found due to the thermal relaxation parameter. We further noticed that a higher value of homogeneous and heterogeneous reaction parameter corresponds to a deceleration in the concentration field and it shows an inverse relation for the Schmidt number. A correlation with accessible results for specific cases is found with fabulous consent.

Advances in Research on Tea Species Adaptive to Climatic Changes

Research done by small scale farmers through simple random sampling in Nyagesenda village, Sensi location, Kisii County, indicated five species of tea plants apart from Assam and china planted in mixed mode in their farms. The research was on experimental basis on the behavior, characteristic or features and appearance of tea harvested on production stage. The farmers experienced changes in tea behavior and characteristic in wet and dry seasons, as some ripen quickly after plucking during rainy season and others dry quickly during drought season. The farmers needed to identify a variety drought resistant, qualitative and quantitative production throughout the year. True experimental research was deliberately manipulated for ten years through observation method, on the alternating climatic changes of the area, in relation to occurrence of hail stones and drought. The research key findings of the varieties were; first, Tea leaves-slow to ripen rainy season, dark green, slender and small surface, soft plucking, and drought resistant, low weights and slow to ripen after hail stones. Second, tea leaves-quick to ripen rainy season, dark green, wide and large surface, softer plucking, dries quickly in drought season, weighs high and quick to ripen after hail stones. Third, tea leaves-quick to ripen rainy season, dark green, slender and small surface, softer plucking,drys in drought, weighs low, quick to ripen after hail stones. Fourth, Tea leaves-slow to ripen rainy season, yellowish green, wide and large surface, hard plucking, drought resistant weights low, slow to ripen after hail stones. Fifth, tea leaves-quick to ripen rainy season and never dry up in drought, yellowish green, average surface, softer to pluck rainy season and hard dry season, adaptive to all seasons, weighs high during rainy season and low dry season and ripens quickly after hail stones. It is concluded as the best variety followed by second and first and third varieties and lastly fourth variety. It is recommended all varieties are significant, therefore, should be grown in sections in the farm not in a mixed variety as it is done in tea farms.

Study on Laser Measurement Technology of Inner Surfaces

Aiming at the traditional measurement methods and equipment cannot meet the accurate measurement problems of complex inner surface geometry parameters. This paper proposes combining the laser displacement sensors, rotary encoders and machine control system to build the measurement system. This system overcomes the traditional contact measurement of the low efficiency, low velocity, low accuracy, and realizes measuring slender and long inner surface. Through analysis and processing of the acquisition of point cloud data, draw a cross-sectional contour of the workpiece to achieve a precise measurement of the internal surface.

Global optimization of tool path for five-axis flank milling with a conical cutter

In this paper, optimum positioning of the conical cutter for five-axis flank milling of slender surfaces is addressed from the perspective of approximating the tool envelope surface to the data points on the design surface following the minimum zone criterion recommended by ANSI and ISO standards for tolerance evaluation. Based on the observation that a conical surface can be treated as a canal surface, i.e. envelope surface of one-parameter family of spheres, the swept envelope of a conical cutter is represented as a sphere-swept surface. Then, an approach is presented to efficiently compute the signed distance between a point in space and the swept surface without constructing the swept surface itself. The first order differential increment of the signed point-to-surface distance with respect to the differential deformation of the tool axis trajectory surface is derived. By using the distance function, tool path optimizations for semi-finish and finish millings are formulated as two constrained optimization problems in a unified framework, and a sequential approximation algorithm along with a hierarchical algorithmic structure is developed for the optimization. Numerical examples are given to confirm the validity and efficiency of the proposed approach. Comparing with the existing approaches, the present one improves the machining accuracy greatly. The rationale developed applies to general rotary cutters.

Mechanical and Superhydrophobic Stabilities of Two-Scale Surfacial Structure of Lotus Leaves

To understand why lotus leaf surfaces have a two-scale structure, we explore in this paper two stability mechanisms. One is the stability of the Cassie-Baxter wetting mode that generates the superhydrophobicity. A recent quantitative study (Zheng et al., Langmuir 2005, 21, 12207) showed that the larger the slenderness ratio of the surface structures was, the more stable the Cassie-Baxter wetting mode would be. On the other hand, it is well-known that more slender surface structures can only sustain lower critical water pressures for structure buckling, or Euler instability, while in the natural environments, the water pressure impacting on the lotus surface can reach a fairly high value (105 Pa in a heavy rain). Our analysis reveals that the two-scale structure of the lotus leaf surfaces is necessary for keeping both the structure and the superhydrophobicity stable. Furthermore, we find that the water-air interfacial tension makes the slender surface structure more instable and the two-scale structure a necessity.

Ultrastructure of Enterococcus faecalis biofilms

Enterococcus faecalis is known to produce biofilms on biomaterials, but the manner in which this occurs is unknown. Herein we report that adhesion of E. faecalis in biofilms appeared to be mediated by cell wall surface projections attaching cells to the substratum. Biofilm formation was observed on the polystyrene surface of 96-well plates and also on the surface of cellulose kidney dialysis tubing used as a model for biofilm formation on catheters. Qualitative differences involved the packing of E. faecalis cells in biofilms, with greater intercellular spacing detected in the 96-well plate, whereas bacteria were tightly packed on the surface of cellulose catheters. Distribution of adherent bacterial cells accumulating on the two surfaces revealed obvious differences, with most of the bacteria attaching to the polystyrene surface as single cells or diplococci separated from neighboring organisms by intervals of uncolonized surface. In contrast, enterococci on the cellulose surface were found as multi-layer cellular aggregates or microcolonies, even when much of the total surface was free from attached bacteria. Microcolonies stained intensely for neutral hexose sugars using the periodic acid–Schiff (PAS) stain. Surface projections, presumably exopolysaccharide, anchored bacteria to the substratum and appeared to elevate the cells above the surface. These slender surface projections could be seen over the entire enterococcal cell wall, with the exception of areas adjacent to septal regions where new cell wall formation was occurring. Rod-like interconnections were also observed between adjacent diplococci. These results suggested that biofilm formation varies on different substrates and that enterococcal surface projections may be involved in E. faecalis colonization and adhesion within biofilms.

Nonlinear effects in 2D transient nonbreaking waves in a closed flume

The nonlinear effects deriving from the focussing of unidirectional waves propagating in a wave flume are analysed by direct fully nonlinear numerical simulation. The main aim of this study is to evidence the features of the wave–wave interaction in the spatial region, where the maximum elevation of the component waves of a given wave group is almost in phase. It will be shown that in the frame of the inviscid fluid hypothesis, the nonlinear interaction of waves leads to an evident space variation of the amplitude spectrum with a large magnification factor of the focused wave elevation compared to the result from linear superposition, a phase shift of the component waves occurs and part of the energy content is shifted to frequencies well above the highest frequency in the input spectrum. These features have basic consequences on the safety and design aspects of ships and marine structures: for instance, this regards the ringing response of large offshore structures. At the same time the availability of kinematic data from the simulation of large waves can be useful for the evaluation of the forces exerted on slender surface piercing bodies in inertia-drag regime method without semi-empirical stretching methods. Moreover the controlled generation of deterministic wave groups with a given frequency content, aimed at the development of new techniques for seakeeping tests, is one of the subjects of interest in ITTC (23rd International Towing Tank Conference).

Tanycytic Ependymoma

Tanycytic ependymoma is an uncommon fibrillar variant of ependymoma characterized by streams of piloid, or hair-like, cells having “ependymal” nuclei. True ependymal rosettes are absent, and perivascular rosettes are inconspicuous. Misinterpretation as schwannoma or astrocytoma is a diagnostic problem and well-documented cases are scarce. The purpose of this report is to document the ependymal features of the neoplasm and to increase awareness of the entity's existence. Biopsy tissues from three patients with tanycytic ependymoma were examined. All tumors consisted of sheets of spindle cells that were positive for glial fibrillary acidic and S-100 proteins. Ultrastructural examination showed characteristic ependymal features, including intracytoplasmic intermediate filaments, prominent intercellular junctions, numerous slender surface microvilli, and microvilli-lined lumina. Accurate recognition of the ependymal nature of this spindle neoplasm requires a high index of suspicion. Because the spindle cells are immu-noreactive with antibodies to both glial fibrillary acidic and S-100 proteins, ultrastructural confirmation of ependymal features is necessary.

走査型振動腐食評価法の効率的境界要素解析

A new effective three-dimensional boundary element method of analyzing electric field produced by localized corrosions has been developed to estimate the accuracy of SVET (Scanning Vibrating Electrode Technique). With decreasing height of the electrode probe from the surface of a sample in an attempt to improve the resolution of SVET, the electrode probe disturbs the electric field and the measuring error of the current distribution increases. It is, therefore, desirable that this error is corrected by numerical analysis considering the disturbance of the electrode probe. However the scale ratio of the whole vessel of the instrument to the measurement area is larger than a factor of 105, so that the conventional BEM has a difficulty in treating such a huge number of elements. In this study, at first the distribution of current density on the slender surface of a sample where current flows out was analyzed with the two-dimensional BEM and then a three-dimensional Boundary Element analysis was performed by considering the slender surface as a simple line-shape element which has the characteristics obtained by the first 2-D analysis. By using the proposed method, the number of elements and repetitive calculations due to scanning of electrode probe can be decreased. A few numerical examples are presented to demonstrate the practical applicability of the proposed method.

The spray sheets produced during vertical wedge impact and steady planing

“Added mass” theory is usually employed in a momentum analysis. In connection with the vertical impact of a wedge, Pierson noted an anomaly when it is employed in an energy analysis, because the two approaches yielded different results. This led the writer to conjecture that the “difference” might be due to the energy dissipated in the spray sheets. The analysis which follows appears to support that conjecture, in that the size of the spray sheets so calculated is the same as those of Pierson's [(1950), The penetration of a fluid surface by a wedge. Stevens Institute of Technology Report No. 381 (July) (IAS paper FF-3)] numerical calculations. The theory predicts, for both vertical wedge impact at constant vertical velocity and for the steady high speed planing of a slender prismatic hull, that half the pressure drag energy ( Du o ) appears as kinetic energy in the spray sheets, the other half being absorbed by the downward deflection of the main body of water. This does not agree with the conclusions drawn from the experimental work of Latorre and Tamiya [(1975), An experimental technique for studying the planing boat spray. Proceedings of the Fourteenth International Towing Tank Conference, Ottawa, Canada, Vol. 4, pp. 562–571] and Latorre [(1983), Study of prismatic planing model spray and resistance components. J. Ship Res. 27, 187–196]. Nor does it agree with two-dimensional planing theory [summarized in ch. 3 of Payne [(1988), Design of High-speed Boats, Volume I: Planing. Fishergate, Inc., Annapolis, Maryland]] where all the energy appears in the spray sheet at very high Froude numbers. But the equal division of energy into spray and water deflection for slender surfaces was predicted for a high speed slender planing surface by both Wagner [(1932), Uber Stoss-und Gleitvorgänge an der Oberfläche von Flüssig-keiten.

Development of Effective BEM for Galvanic Corrosion Analysis of a Slender Structure.

An effective three-dimensional boundary element method was developed for predicting electrogalvanic field response of a structure which consists of slender parts. First, the corrosion field which has slender surfaces is analyzed by the boundary element method with simple line-shape elements. By this method, the axial distributions of potential and current density of slender parts can be obtained, but not circumferential distributions. Then, the cross section of the slender part considered is discretized with two-dimensional elements, and the circumferential distributions of potential and current density are obtained, using the values which were obtained with the simple line-shape elements. By using the proposed method, the CPU time is decreased. A few numerical examples are presented to demonstrate the practical applicability of the proposed method.

Surface and branching of placental villi in early abortion: relationship to karyotype Scanning electron microscopic study

The placental villi of 61 early abortions with known karyotype and 7 legally induced abortions were investigated by scanning electron microscopy and documented in standardised enlargements. Five groups were established from the findings: uniformly branched villi with a velvety surface (group A) were found in 4 of the 7 induced abortions, abundant syncytial sprouts (group B) in 4 of the 6 cases with monosomy X; all 5 cases of triploidy were classified in the group bulbous or spherical villi (group C); 13 out of 25 cases of trisomy were found to have little branching and a surface densely covered with microvilli (group D), while 14 out of the 25 cases of euploidy belonged in the group with slender villi and surface with focal areas of denudation (group E). Forty of the 68 cases were properly assignable to the correct groups (58.8%). The non-uniformity of the villous morphology in the case of induced abortions shows that there is no uniform development of the (early) placenta. The variable morphology seen in abortions with euploidy reflects the various mechanisms of abortion applicable to this group.

Linearized dynamics of two-dimensional bubbly and cavitating flows over slender surfaces

The present work investigates the dynamics of two-dimensional, steady bubbly flows over a surface and inside a symmetric channel with sinusoidal profiles. Bubble dynamics effects are included. The equations of motion for the average flow and the bubble radius are linearized and a closed-form solution is obtained. Energy dissipation due to viscous, thermal and liquid compressibility effects in the dynamics of the bubbles is included, while the relative motion of the two phases and viscous effects at the flow boundaries are neglected. The results are then generalized by means of Fourier synthesis to the case of surfaces with slender profiles of arbitrary shape. The flows display various flow regimes (subsonic, supersonic and super-resonant) with different properties according to the value of the relevant flow parameters. Examples are discussed in order to show the effects of the inclusion of the various energy dissipation mechanisms on the flows subject to harmonic excitation. Finally the results for a flow over a surface with a Gaussian-shaped bump are presented and the most important limitations of the theory are briefly discussed.

Axisymmetric Motion of a Viscous Fluid Inside a Slender Surface of Revolution

Starting with the exact three-dimensional equations for an incompressible linear viscous fluid, an approximate system of one-dimensional nonlinear equations is derived for axisymmetric motion inside a slender surface of revolution. These equations are obtained by introducing an approximate velocity field into weighted integrals of the momentum equation over the circular cross-section of the fluid. The general equations may be specialized to reflect specific conditions on the lateral surface of the fluid, such as the presence of surface tension, a confining elastic membrane, or a rigid tube. Two specific examples are considered which involve flow in a rigid tube: (1) unsteady starting flow in a nonuniform tube, and (2) axisymmetric swirl superimposed on Poiseuille flow. In each case comparison is made with earlier, more restricted results derived by perturbation methods.

Stress intensity factor analysis of surface crack.

In order to solve slender surface crack problems by boundary element technique, stress-type singular element is introduced to the programme, and a new method combining displacement and stress solutions is proposed to calculate stress intensity factors. The results show that the present approach gives accurate and stable apparent stress intensity factors F(r) near crack tip.

Stress Intensity Factors for slender surface cracks

AbstractA calculation procedure for plates with semi‐elliptical surface cracks under tension and bending with aspect ratios of a/c ≤ 0.2 and arbitrary relative crack depths a/t is presented. For the computation an improved line spring model is used. K1‐values are calculated along the crack contour.For the deepest point of a surface crack the K1‐values are terminated by two well known threshold curves: The upper bound curve is identical with the solution for the edge crack (a/c = 0). The lower bound is described by the results after Newman and Raju for a/c = 0.2. The present K1‐values are in good agreement with both curves.For high a/t‐ratios the maximum K1‐value is found between the deepest and the surface edge point (Q′ and Q″) of the crack. This result could explain among others that crack growth does not conserve the semi‐elliptical shape sometimes.

The normal force on a flat planing plate, including low length to beam ratios

Abstract A previous paper (Payne, 1980) developed the theory of a slender planing surface from first principles, and found it to agree with experiment without the need for “factors determined from experiments”. The theory broke down, however, for low wetted length to beam ratios because the flow is then no longer two-dimensional in character in respect to a section normal to the flow. It is in a transition to the condition where, at very small length to beam ratios, it is two-dimensional in a vertical plane parallel to the flow, rather than normal to it. In the present paper we determine, albeit somewhat heuristically, the virtual mass coefficient of a flat plate in the transition region. This is then employed to compute the normal force on a planing plate in both steady state and transient motion. For both conditions the agreement with the available experimental data is within the accuracy of the data. Both theory and experiment lead to the conclusion that certain traditional concepts in the of trim angle and Pierson's suggestion that ‘wetted length’ is more fundamental than the length of intersection with the still water surface. The widespread acceptance of this latter suggestion has meant that a key parameter in the present theory—the nominal or undisturbed water intersection length—is almost never measured in modern experiments. Thus, since we could not find any modern data, we had to appeal to the classical experimental papers which originated the scientific study of planing in the thirties and forties. Oddly, the earliest papers gave data which had much less scatter than the later papers.

Morphological aspects of glucocorticoid-induced cell death in human lymphoblastoid cells.

Morphological aspects of cell death associated with a cytolethal concentration of methylprednisolone sodium succinate (500 micrograms/ml) on the BLA1 lymphoblastoid cell line were studied over a 48-hr incubation period by light, transmission and scanning electron microscopy. Studies revealed two distinctive morphological changes induced by the steroid from 1 hr onwards after treatment. One showed contortion and "blebbing" of the cytoplasm and nucleus accompanied or followed by nuclear pyknosis, resulting in the formation of membrane-bounded bodies containing apparently normal cytoplasmic organelles with or without nuclear fragments. The other showed "rounding up" of the cell with loss of cytoplasmic protrusions and long slender surface processes, aggregation of well-preserved cytoplasmic organelles, accompanied by nuclear pyknosis and fragmentation. In both cases many of the features are typical of apoptosis. The subsequent degeneration of cells and fragments not unexpectedly resembled in vitro autolysis. This in-vitro system is suitable for studying the early biochemical events and intracellular control mechanisms of apoptosis.

Inviscid hypersonic flow on cusped concave surfaces

An analysis of the exact equations of the inviscid flow of a perfect gas over cusped concave bodies is described. The field is examined in the limit of infinite free-stream Mach numberM∞. The slope of the shock wave in a small region adjacent to the leading edge is strongly dependent onM∞, while much further downstream the shock-wave slope is controlled primarily by the body slope. Consequently the region near the leading edge introduces into the field downstream a thin layer of gas, adjacent to the body, where the entropy is much lower than that of the gas above it. This layer is so dense that the gas velocity along it is not appreciably slowed by the pressure gradient along the body. However, it is so thin that there is little pressure change across it.The well-known self-similar solutions to the hypersonic small-disturbance equations have previously only been used to study the flow on blunted slender convex surfaces. They are known to behave singularly at the body. It is shown that there is a region on concave power-law shapes where the self-similar solutions are the correct first approximation to the exact inviscid equations in the limitM∞→ ∞; and that, further, they predict the correct first-order surface pressure.Numerical results for surface pressure from the similar solutions are presented, and comparisons are made with certain approximate theories available for more general shapes. Pressure measurements taken on a cubic surface in the Imperial College gun tunnel are presented and compared with the theoretical distributions.