Triangle Cross Section Research Articles

Low Loss Vertical Optical Path Conversion Using 45° Mirror for Coupling between Optical Waveguide Devices and Planar Devices

To realize low loss optical interconnects between optical waveguide devices and two dimensional array-type devices, we investigated a novel 45° mirror device buried by index matching epoxy resin and coated with an anti-reflection layer. A groove with an isosceles right triangle cross section was formed using a dicing saw so as to cut into the single-mode optical waveguide, and aluminum thin film was obliquely deposited on the 45° side wall of the groove to increase the reflectance. The groove was filled with a spin-coating of UV-curable epoxy resin to planarize the top surface, and low index polymer (Teflon) was formed on the top surface as the anti-reflection layer. The optimum depth of the groove for reducing shadowing of the deflected beam was analyzed. As a result the insertion loss of the 45° mirror was reduced 1.3 dB compared to the insertion loss of straight waveguide. In addition, a novel optical tap device is proposed and demonstrated using a similar fabrication process to that of the 45° mirror device. The isosceles right triangle-shaped groove was formed on the upper cladding layer so as to almost touch the core layer. After filling it in and finishing it with the epoxy resin and AR coating used in the 45° mirror device, the loss of the through port was reduced 0.5 dB compared to the insertion loss of straight waveguide and -14 dB (4.0%) of the optical power was transmitted to the tap port. Lastly as a model of the coupling between waveguide devices and two-dimensional arrayed devices such as vertical cavity surface emitting lasers (VCSEL's), the vertical port of the 45° mirror device was connected to a single mode fiber with a very small mode field diameter (3.6 µm). This configuration transmitted -11.8 dB (6.6%) of the input power from the input port to the vertical tap port and vice versa.

Self-Organized Microcones Grown on Si Substrate by Microwave Plasma Chemical Vapor Deposition

Self-organized microcones were grown on an n-Si(100) substrate by microwave plasma chemical vapor deposition. It was found that microcones having a cross section of an isosceles triangle were successfully grown on the Si substrate and that all the microcones had almost the same sizes. From the results of X-ray photoelectron spectroscopy (XPS), we concluded that the microcones consist of SiC covered with a thin carbon-based material. A model of the growth mechanism of the microcones was derived assuming that thermally assisted field emission and bombardment with ions accelerated by an electric field in the ion sheath of microwave plasma play an important role in the growth of the microcones. The field dependence of emission current from the microcones in vacuum agreed with the Fowler–Nordheim model, which indicates that these microcones can be used as field emission arrays.

Stationary Fluid Dynamic Behaviour of V-Shaped Diffuser/Nozzle Elements for Valveless Micropump

A novel type of V-shaped (isosceles triangle cross-section) diffuser/nozzle element is proposed for use for valveless micropump. Stationary fluid dynamic behaviour of V-shaped diffuser/nozzle elements in a valveless micropump is investigated by experiment and simulation. Both the results agree well with each other when the Reynolds number is higher than 100 and the pressure loss coefficient ratio of micropump nearly always keeps a constant. For a single V-shaped diffuser, the general trends of variation of pressure loss coefficient with opening angle and Reynolds number are opposite in small and large angles. Compared with conical and flat-wall diffusers, V-shaped diffuser shows the smallest pressure loss when the Reynolds number is 200.

Viscous flow through pipes of various cross-sections

An interesting variety of pipe cross-sectional shapes can be generated, for which the Navier–Stokes equations can be solved exactly. The simplest cases include the known solutions for elliptical and equilateral triangle cross-sections. Students can find pipe cross-sections from solutions of Laplace's equation in two dimensions, and then plot the velocity distribution in the pipe. The total flow for a given pressure gradient and pipe area can be readily compared for different pipe shapes.

Large scale tapered GaN rods grown by chemical vapour deposition

Large quantities of gallium nitride-tapered rods with sharp-tip were synthesized by a chemical vapour deposition method using the reaction of ammonia with the mixture of gallium oxide and carbon. The as-prepared rods have triangle cross section with lateral slope tapered to their ends; they are single-crystalline wurtzite structure crystals grown with the [ 1 1 2 ¯ 0 ] direction. The axial self-catalytic vapour–liquid–solid (VLS) growth and radial vapour–solid (VS) growth mechanism as well as the change of reactive atomic ratio (Ga/N) during growth process were believed to contribute to the formation of tapered rods.

Heterogeneous Nucleation With Artificial Cavities

Bubble incipience in artificial cavities manufactured from silicon has been studied using gas nucleation and pool boiling. Moderately wetting water and highly wetting ethanol have both been used as the bulk fluid with cylindrical cavities, as well as those with a triangle, square, and rectangle shape cross section. Nominal cavity sizes range from 8to60μm. The incipience conditions observed for water using both gas nucleation and pool boiling suggest that bubble initiation originates from a concave meniscus. Cornwell’s contact angle hysteresis theory for vapor-trapping cavities is used to explain the gas nucleation results. The pool boiling results are more difficult to explain. Using ethanol, cavities appeared to be completely flooded and were not activated using either gas nucleation or pool boiling. Using water and gas nucleation, cavities were almost always activated, provided the incipience criterion was satisfied; in contrast cavities in pool boiling with water activated with different superheats during different experiments. The difference in incipience behavior between gas nucleation and pool boiling with water is explained based on vapor-trapping and thermal suppression considerations. Based on limited experimental results, it appears that the backpressure does not influence gas bubble incipience, provided the pressure difference is the same. The experimental results presented affirm the theory of heterogeneous nucleation from vapor-trapping cavities provided contact angle hysteresis and vapor trapping are fully accounted for. However, the results also suggest that the theoretical considerations required for a deterministic model for incipience from vapor-trapping cavities during boiling is more complex than previously hypothesized.

Non-spherical Carbon Composite Agglomerates: Lab-scale Manufacture and Quality Assessment

For recycling steel work dust and improving blast furnace (BF) performance, a few types of non-spherical carbon-iron oxide agglomerates were manufactured in laboratory scale and their strength and reducibility were evaluated using a shatter and a tumbler tester, a simulator for lumpy zone in BF and a softening/melting tester. The flat or ragged shape was expected to enhance reducibility and to prevent the agglomerate from unwilling rolling down to the center of BF. Agglomerate in the shape of column with concave triangle cross-section (Tetra) showed the highest yield during extruding and almost same strength compared with a commercial spherical cold-bond pellet. In reducibility Tetra excelled sinter but spherical carbon composite pellet, which denied shape effect. Reduction disintegration of Tetra initiated at 600°C and reached to the maximum of 60% at 860°C, the entrance of thermal reserve zone, meaning the issue of cement bonding on disintegration remained unsolved. In case of single use, Tetra did not melt down up to the upper limit temperature of the softening/melting tester, causing S-value enlarged. Using Tetra mixed with sinter was recommended as a trial of admixing 50% Tetra to sinter accelerate reduction rate of sinter, improving BF efficiency by 45 kg/t decreases in RAR; moreover, the mixture remarkably reduced the pressure loss of cohesive zone.

Mixing and Entrainment Characteristics of Circular and Noncircular Confined Jets

The present work deals with the experimental investigation of entrainment characteristics of confined/semiconfined circular and noncircular jets. The jet fluid, after issuing out of a nozzle of circular or noncircular cross section, enters a circular mixing tube of larger area, and during this process it entrains some ambient fluid into the mixing tube. The flow is incompressible and isothermal at a jet Reynolds number of 7200. The experimental results obtained in the study are first validated with the approximate theoretical analysis of Pritchard et al. (1997) and also with the similarity solution proposed by Becker et al. (1963) for circular nozzles. It is observed that the similarity solution is applicable for circular as well as noncircular jets in the region close to the jet axis and away from the nozzle exit plane. The entrainment ratio increases to a maximum value as the jet location is shifted away from the tube inlet; for the configurations studied, enhancement up to 30% has been observed in the entrainment ratio with shift in jet location. For a smaller mixing tube diameter and jet located at the inlet of the mixing tube, the circular jet entrains more than noncircular jets. For a larger mixing tube or shifted jet locations, the noncircular jets entrain more of ambient fluid, in general. Among the different noncircular geometries considered, the jet having the cross section of an isosceles triangle causes maximum entrainment.

Between two limits: Flow separation behind a bluff body close to a wall

There are two classical cases of a considerable flow separation: A body in a flow without limits is leading to a separation behind the body, a wall with a remarkable change of contour is leading to a separation region at the wall. Here, both situations are considered for the two-dimensional case of a flow past a cylinder with a triangle cross section. The free flow case and the flow at a cylinder directly placed at a wall is investigated. An intermediate situation can be observed, when the cylinder is placed close to the wall. The occurring complex separation region can be interpreted in that way, that both separation regions, body and wall related, are existing.

Triangular gallium nitride nanorods

Gallium nitride nanorods were synthesized by a chemical vapor deposition using the reaction of gallium/gallium nitride with ammonia. All nanorods have, exclusively, a triangle cross section with an average diameter of 50 nm. They consist of single-crystalline wurtzite structure crystal grown with the [010] direction. X-ray diffraction and Raman spectroscopy data suggest no shift of the lattice constants from those of the bulk. Temperature-dependent photoluminescence exhibits the I2 and free-to-bound emission peaks. The present triangular gallium nitride nanorods would be free from the stress, having the band-gap energy of the bulk.

Conductance calculation of a long tube with equilateral triangle cross section

Using the stratified gas flow model for calculating the conductance of long tubes with constant cross section, an analytical expression for calculating the conductance of a long tube with equilateral triangle cross section has been derived. The formula given is applicable to the full pressure range. A minimum in the conductance in the intermediate flow state is shown.

Optimal Design of Parabolic-Bottomed Triangle Canals

The characteristics of a parabolic-bottomed triangle cross section are introduced. For this geometry the “best” hydraulic cross section is determined by using the undetermined multipliers method of Lagrange. For a given flow, roughness coefficient, and longitudinal slope, the best hydraulic section is the channel section having the least wetted perimeter or cross-sectional area. The cross-sectional parameters of this novel geometry are compared with those of trapezoidal, parabolic, and round-bottomed triangle cross sections. It is shown that for all values of side slopes, the flow area and wetted perimeter in a parabolic-bottomed triangle cross section are less than those of trapezoidal and parabolic cross sections for the same discharge. This indicates that less excavation and linings are involved and therefore implies that the parabolic-bottomed triangle cross section is more economical than trapezoidal and parabolic cross sections.

Parametric investigation of a basin-type-multiple-effect coupled solar still

Parametric analysis was performed for the basin-type multiple-effect coupled solar still with a triangle cross-section consisting of a horizontal basin liner and a number of vertical parallel partitions in contact with saline-soaked wicks with narrow gaps between the partitions, under dry weather conditions at 26.1 °N latitude. The productivity of the still increased in winter with an increase in the angle between the glass cover and the basin and decreased in summer. In the spring and autumn seasons productivity had a gentle peak between a 40° and 45° angle. Increasing supply rates of saline water to the wicks and increasing initial mass of the basin water decreased productivity. With a decrease in diffusion gaps between partitions, productivity exponentially increased, and it also showed exponential increases with an increase in the number of distillation cells between the partitions. The productivity of the still of 13 partitions with 5-mm gaps and a 40° angle of the glass cover was four times more than the basin-type stills, and the still was more productive than the conventional multiple-effect stills by about 40% or more.

A highly productive basin-type-multiple-effect coupled solar still

A newly designed multiple-effect solar still with a triangle cross-section consisting of a horizontal basin liner, a tilted double glass cover and the vertical parallel partitions in contact with saline-soaked wicks is presented and theoretically analyzed. Solar radiation is absorbed in the basin and in the first partition, and the partition section recycles the energy from the basin as well as solar energy, which is directly absorbed by the first partition. A single distillation cell with a 5-mm diffusion gap between vertical partitions has been experimentally explored. No contamination of distillate with saline water was experimentally detected in the single distillation cell, and the experimental observation of the wick and the measurements of the temperature drop through the cell with the 5-mm gap showed that dry patches hardly appear on the wick. The proposed still with 5-mm diffusion gaps is theoretically predicted to produce distillate of 15.4kg −2 m −2d −1 on a sunny day of G ti =22.4 MJ/m −2d −1 solar radiation, and its efficiency is about 3.5 times larger than the average experimental value for the conventional basin type stills by Cooper [20] and 1.2-1.6 times larger than the experimental maximum values of the conventional multiple-effect stills [3,9].

Study of dry oxidation of triangle-shaped silicon nanostructure

Silicon nanostructures along [011] direction with upside down triangle cross sections on the top of the sawtooth structure with (111) facets are prepared by using the lithography technique, reactive ion etching, and anisotropic wet chemical etching. These triangle-shaped silicon nanostructures are thermally oxidized in dry oxygen over a range of temperature from 850 to 1000 °C, which is characterized by scanning electron microscopy. The self-limiting oxidation phenomenon observed in silicon nanostructures is discussed. Cross-sectional shape change of the silicon nanostructure under different oxidation temperatures is demonstrated. A silicon quantum wire is successfully fabricated by two-step thermal oxidation of the silicon nanostructures.

Imbibition of Oil in Film Form over Water Present in Edges of Capillaries with an Angular Cross Section

In this paper it is shown, for the first time, that a nonspreading oil can form films over water films present in the edges of pores in a water-wet porous medium. Both the water and the oil wet the solid surface preferentially to air, but water wets the solid preferentially to oil. The mechanism of the film formation is capillary imbibition, i.e., spontaneous displacement of air by the oil, and it is similar to the formation of water films in the edges of a clean glass capillary of angular cross section filled with air. The principal difference is that, whereas the water imbibes over a solid surface, the oil imbibes over a surface consisting partly of water and partly of a solid wetted by oil. It is shown, by a combination of applications of Laplace's equation of capillarity with the condition of minimum surface free energy, that if a "critical" oil film thickness is exceeded by the addition of excess oil, then this excess oil will imbibe over the water film in the edge until the equilibrium critical oil film thickness is established. The equations have been solved by iteration for the critical oil film thickness, using representative values of the parameters involved. Further, it is shown that an oil blob placed in a capillary of polygonal (e.g., square or equilateral triangle) cross section, containing water films in the edges of the capillary, will imbibe in the form of films over the water present in the edges, subject to certain limitations, specified in the paper. The theoretical predictions are supported by photomicrographs showing imbibition of benzene equilibrated with water and a paraffin oil over water present in the edges of a 2D glass micromodel. The spreading coefficient is negative for both systems.

Epitaxial overgrowth of apatite crystals on the thin-ribbon precursor at early stages of porcine enamel mineralization

The aim of the present work was to investigate changes in cross-sectional morphologies of enamel crystallites as a function of location in secretory porcine enamel. Enamel tissues were obtained from 5- to 6-month-old slaughtered piglets. For examination by electron microscopy, a portion of the secretory enamel was embedded in resin and ultrathin sections were prepared with a diamond knife. In parallel studies, compositional and structural changes of enamel mineral were assessed by chemical analysis and Fourier transform infrared (FTIR) spectroscopy. For this purpose, two consecutive layers of the outer secretory enamel, each approximately 30 microns thick, were separated from the labial side of permanent incisors. Using high-resolution electron microscopy, early events of enamel crystal growth were characterized as the epitaxial growth of small apatite units on the lateral surfaces of the initially precipitated thin ribbon. These apatite units had regular triangle or trapezoid cross-sections. After fusions of those isolated trapezoids on both lateral sides of the platy template, the resulting enamel crystallites had the well-documented flattened-hexagonal shapes in cross-sections. The initially precipitated thin plate was buried inside the overgrown apatite lamella and then retained as a central dark line. Similar morphological evidence for the epitaxial nucleation and overgrowth of carbonatoapatite on the platy template was obtained in vitro. Chemical and FTIR analyses of the enamel layer samples showed that the characteristics of the youngest enamel mineral were distinct from those of enamel crystals found in older secretory enamel.(ABSTRACT TRUNCATED AT 250 WORDS)

Aerodynamic forces on noncircular cross-section missile forebodies

A numerical investigation is performed to develop the aerodynamic characteristics of forebodies with noncircular cross sections in supersonic cruise. A robust, second order accurate Euler code, is utilized to determine CLj CD, and CM for forebodies with circular, square, diamond, triangle, and inverted triangle cross sections. The predictions at Mach 2.01 compare well with wind tunnel data for angles of attack from 0 to 6 deg. Computed results at Mach 3.0 show that distinct aerodynamic advantages may be obtained by using forebodies with noncircular cross sections. In supersonic cruise, forebodies with noncircular cross sections develop considerably greater lift and lift/drag ratios than forebodies with circular cross sections.

Integral Equations Obtained From the Probabilistic Strength of Bars Subjected to Pure Torsion

The present work is a collection of results relating to the application of the integral equations method to the case of prismatic bars subjected to pure torsion. The specific risk of fracture functions are independently obtained for volume and surface brittlenesses, and when the material of the bar simultaneously exhibits the two types of brittleness, both can be separated. In the cases of a square bar and a bar having a regular polygon cross section of n sides, a simple stress field is used. The particular cases of equilateral triangle, square, and circular cross section are explicitly indicated in the formulas. On the other hand, the cases of a round, a rectangular, and an elliptical bar are treated, knowing exactly the stress field acting in the bar’s cross section. The particular cases of a square, a thin rectangular, and a round bar are also studied. The purpose of this review is to emphasize that the specific risk of fracture function can be obtained without knowing previously its analytical form by solving an integral equation.

The mechanical resonances of a human tibia: Part I— In vitro

This paper represents the beginning of a research programme whose aim is to develop a practical method of monitoring the healing progress of fractures. The objectives of the following are to identify the various resonances, and to show the types of modes which exist in long bones in vitro. A model has been evaluated to predict the tibial resonance frequencies. It is composed of a homogeneous, hollow beam with the constant cross section of an isosceles triangle. Such a beam can explain the two main types of fundamental transverse mode along with their triple resonances. The predicted resonances of the transverse waves are less than 5.8% in error in comparison to the measured values. This error increases to 23.8% for the torsional waves due to their different characteristics.