Asymmetric Cross Section Research Articles

Symbolic boundary integral equation formulation for coupled vibrations of asymmetric beams

Symbolic computer algebra systems relieve one from the tedious task of different mathematical operations which are essential to obtain solutions. Due to their highly advanced features they have come to be used widely in computational mechanics. This paper describes an application of the modern computer algebra system Mathematica to the derivation of fundamental solutions necessary for the application of the boundary integral equation method. The problem treated is an asymmetric cross-section Timoshenko beam in free vibration. For this problem, the derivation of fundamental solutions involves lengthy mathematical operations which are very tedious if performed explicitly by hand. Therefore, using Mathematica we derive the fundamental solutions and generate the influence matrices from which the natural frequencies can be found. © 1998 John Wiley & Sons, Ltd.

Impact of Surface Band Bending at the Rear Si–SiO2 Interface on Conversion Efficiency of Rear Locally-Contacted Silicon Solar Cells

The dependence of the conversion efficiency of rear locally-contacted p-type silicon solar cells on surface band bending at the rear Si–SiO2 interface is studied for several substrate resistivities and rear oxide thicknesses through two-dimensional device simulations. Conventionally, the cell efficiency was thought to increase as the band bending induced by work function difference and positive oxide charge increases. However, this is not necessarily true. Under the assumption of asymmetrical capture cross sections (σn/σp=102 at midgap) at the rear interface, the cell efficiency has a maximum value and then decreases gradually as the band bending increases. This is because a large number of generated electrons (minority carriers) are pulled into the rear surface and the greater part of the accumulated electrons flow into the rear p+-contact for large band bending.

Microscopic study on the solidification of aqueous solutions using laser interferometry

Solidification of an aqueous solution was studied using a laser interferometry technique combined with an optical microscope. In order to measure the concentration distribution in an aqueous NaCl solution near an ice crystal and the three-dimensional shape of the ice crystal in a known temperature field, a directional solidification stage was used. This was composed of low- and high-temperature blocks and a moving bed. In our experiment, ice crystals showed four shapes: flat, treelike, swordlike, and needlelike. As a result of the interferometry experiment, it was observed that the concentration increases in the bulk solution for thick samples, swordlike ice crystals have an asymmetric triangular cross section, and treelike crystals have a flat and low top. We also studied ice formation response to injection of a high-concentration solution. © 1998 Scripta Technica, Heat Trans Jpn Res, 27(5): 353–364, 1998

2×2 fused fiber null couplers with asymmetric waist cross sections for polarization independent (>0.01 dB) switching

Polarization independent (<0.01 dB) switching is achieved at 1.55 /spl mu/m in a strongly guiding, fused tapered fiber null coupler acoustooptic switch. An intermediate degree of fusion of the dissimilarly sized fibers is shown experimentally to have the form birefringence required to render the mode-splitting coupler polarization insensitive. The effect of the degree of fiber fusion on the acoustic wavelength of flexural waves is studied theoretically and experimentally, and precise control over the degree of fiber fusion is obtained for coupler waist cross-sectional dimensions as small as 6 /spl mu/m.

Microscopic study on the solidification of aqueous solutions using laser interferometry

Solidification of an aqueous solution was studied using a laser interferometry technique combined with an optical microscope. In order to measure the concentration distribution in an aqueous NaCl solution near an ice crystal and the three-dimensional shape of the ice crystal in a known temperature field, a directional solidification stage was used. This was composed of low- and high-temperature blocks and a moving bed. In our experiment, ice crystals showed four shapes: flat, treelike, swordlike, and needlelike. As a result of the interferometry experiment, it was observed that the concentration increases in the bulk solution for thick samples, swordlike ice crystals have an asymmetric triangular cross section, and treelike crystals have a flat and low top. We also studied ice formation response to injection of a high-concentration solution.

Characterization of Stream Meanders for Stream Restoration

Recently increased emphasis and attention has been given to river management and restoration of modified streams. A variety of restoration techniques and objectives exist, including asymmetrical cross-section construction, point bar development, two-stage channel design, floodplain approaches, pools and riffles re-creation, and sinuosity and meander restoration. Modifications of the planform geometry can induce undesirable morphological and ecological consequences and significant channel adjustments that, depending on the energy of the flow, can result in failure of the restoration design through either erosion or sedimentation. In this study we provide an analysis of the accuracy of empirical relations of meander parameters for use in meander restoration procedures. A case study in central Maryland is used to demonstrate this analysis. It is suggested that the combination of a field reconnaissance and analytical study should be used to determine the appropriateness of using published regression equations...

Dynamic stress analysis and a fracture mechanics approach to life prediction of turbine blades

Emerging blade technologies are finding it increasingly essential to correlate blade vibrations to blade fatigue in order to assess the residual life of existing blading and for development of newer designs. In this paper an analytical code for dynamic stress analysis and fatigue life prediction of blades is presented. The life prediction algorithm is based on a combination method, which combines the local strain approach to predict the initiation life and fracture mechanics approach to predict the propagation life, to estimate the total fatigue life. The conventional stress based approach involving von Mises theory along with S-N-Mean stress diagram suffers from the drawback that it does not make allowance for the possibility of development of plastic strain zones, especially in cases of low cycle fatigue. In the present paper, strain life concepts are employed to analyse the crack initiation phenomenon. Dynamic and static stresses incurred by the blade form inputs to the life estimation algorithm. The modeling is done for a general tapered, twisted and asymmetric cross section blade mounted on a rotating disc at a stagger angle. Blade damping is non-linear in nature and a numerical technique is employed for estimation of blade stresses under typical nozzle excitation. Critical cases of resonant conditions of blade operation are considered. Neuber's rule is applied to the dynamic stresses to obtain the elasto-plastic strains and then the material hysteresis curve is used to iteratively solve for the plastic stress. Static stress effects are accounted for and crack initiation life is estimated by solving the strain life equation. Crack growth formulations are then applied to the initiated crack to analyse the propagation of crack leading to failure. The engineering approximations involved are stated and the algorithm is numerically demonstrated for typical conditions of blade operations.

Study on Solidification of Aqueous Solution Using Laser Interferometry.

Solidification of an aqueous solution is studied using a laser interferometry technique combined with an optical microscope. In order to measure the concentration distribution in an aqueous NaCl solution near an ice crystal and three-dimensional shape of the ice crystal under a known temperature field, a directional solidification stage is used, which is composed of low-and high-temperature blocks and a moving bed. In this experiment ice crystals showed four shapes : flat, treelike, swordlike and needlelike. As a result of the interferometry experiment, it was observed that concentration increases in bulk solution for thick samples, swordlike ice crystal has an asymmetric triangular cross section, and that treelike crystal has a flat and low top. Also, ice formation response to injection of a high concenttration solution was studied.

A finite element model for static and dynamic analysis of thin-walled beams with asymmetric cross-sections

The fourth order governing differential equations for thin-walled beams with asymmetric cross-sections under coupled bending and torsion are derived in this paper. The stiffness matrix and the consistent mass matrix of a thin-walled beam element with an asymmetric cross-section is established by using the homogeneous solutions to the fourth order governing differential equations as interpolation functions between the degrees of freedom at each node of the element. The shear effect and the coupling between bending and torsion are fully taken into account in the finite element model developed in this paper. This model can be used in static and dynamic analysis of the thin-walled beams with asymmetric cross-sections.

Modelling of optical fibre couplers with weakly fused asymmetrical cross-sections based on superposition of normal modes

Wavelength-flattened optical fibre couplers can be designed by employing guided cores with different dimensions. We perform modelling of such couplers with weakly fused cross-sections based on accurate modal analysis and superposition of normal modes. Vectorial normal modes on asymmetrical weakly fused couplers involving touching fibres with different radii are solved by the circular harmonics expansion method; thus our model can treat the effects of different polarizations. The step approximation is adopted in modelling the tapered structure.

A new short and low-loss passive polarization converter on InP

We propose an improved polarization converter in InGaAsP-InP. It contains a series of waveguide sections with asymmetric cross-sections with angled facets. A 09-mm-long TE/TM-converter at a wavelength of 1.5 μm is simulated. It contains 10 sections and has an excess loss of 0.25 dB. Both coupled mode theory and beam propagation method (BPM) simulations are included.

Velocity and boundary shear in a wide compound duct

Mean flow distributions of primary velocity and boundary shear stress were measured in a wide closed duct with a range of asymmetric compound cross-sections. The cross-sectional geometries included three different wall angles, vertical, 1:1 and 1:2 (vertical:horizontal) at the interface between the shallow and deep subsections. Results are presented for the effect of relative depth and wall angle upon primary velocity, boundary shear stress and friction factors. The particularly detailed boundary shear stress measurements indicate the presence of secondary flow on the flood plain even at the lowest relative depths, where it would not normally be identified by coarser spacing of the data.

New Concept of Machining by Means of Six-Axis Control

Summary The study deals with a new machining concept by making use of 6-axis control. 6-axis control implies that a cutting tool allows three rotational movements for positioning as well as three translational ones. A 6-axis control machining center equipped with a main spindle capable of tool orientation in addition to conventional 5-axis control structure is developed. A non-rotational cutting tool is mounted at the main spindle to carry out the 6-axis control machining, which allows a variety of machining possibilities. In the study, a control software for grooving with an asymmetric cross section is presented together with experimental cutting results.

Nonuniform elastic torsion and flexure of members with asymmetric cross-section

In a previous paper, the authors considered the linear response of a solid prismatic elastic member to a torque which varied along the length of the member. The cross-section considered was only restricted by the requirement of two axes of symmetry. That restriction is removed in the present work, but its removal implies that the response to torque will generally now involve bending, so the treatment has been extended to allow arbitrary loading in torsion/flexure. It transpired that a satisfactory analysis is incompatible with the concept of a “shear centre”, and the existence of a shear centre, as part of a rigorous theory or as an approximation, is clarified in the paper.

Inhomogeneities in single-crystal components

The temperature distribution during single-crystal solidification of the Ni-based superalloys SRR99 and CMSX-6 by the Bridgman process was measured at various withdrawal rates in dummy turbine blades. Asymmetric heat flux and cross-section transients influence the geometrical formation of the liquidus isotherm and consequently of dendritic growth. The probability of the formation of structural inhomogeneities such as microporosity, zebras, mosaic structures, etc. is largely dependent on the curvature of the solidification front, which in turn depends on the geometrical arrangement of the ceramic cluster and on the withdrawal rate. The proneness to recrystallization during γ′ solutioning at cross-section transients due to casting-induced deformation and misaligned dendrites was also examined. Recrystallization remains confined to highly deformed areas as long as microscopic inhomogeneities acting as obstacles are present during heat treatment. High cycle fatigue tests showed that defects such as porosity and local recrystallization reduce the fatigue strength to about half the fatigue strength of the defect-free materials.

Polarized q--> Lambda fragmentation functions from e+e---> Lambda + X.

Measurement of the helicity asymmetric cross section for semi-inclusive production of $\Lambda$-hyperons in $e^+e^-$ annihilation near the $Z^0$ resonance allows a complete determination of the spin-dependent fragmentation functions for the different quark flavors into the $\Lambda$. The parity violating, self analyzing, decay of the final state $\Lambda$ makes the experimental analysis of the helicity asymmetry possible. This experiment should be practical with present day technology at the LEP collider at CERN or at SLC at SLAC.

Structure and tectonic setting of the 77°E and 75°E Grabens, Kerguelen Plateau, South Indian Ocean

The Central Kerguelen Plateau (South Indian Ocean) is characterized by abundant north‐south striking normal faults, which comprise two prominent north‐south rifts known as the 77°E and 75°E grabens. The 77°E Graben is a well‐defined structure which extends over some 800 km from the eastern margin of the Kerguelen Plateau to about 58.5°S. Over most of its length it is associated with a 10–30 km wide axial rift and with a 100–150 km wide uplift. The 75 °E Graben is less well documented, but the available data suggest that its dimensions and internal structure resemble that of the 77°E Graben. In the better documented 77°E Graben, six rift segments, 50–100 km long, are identified. Faulting is more developed at the northern and southern ends of the 77°E Graben, possibly resulting from the interaction with other rifts. To the north, the 77°E Graben abuts the highly faulted eastern margin of the Kerguelen Plateau and the northern part of an even larger rift zone, the Plate Boundary Rift Zone, which extends along the boundary with the Australian‐Antarctic Basin. To the south, the 77°E Graben adjoins the northwestern end of the Southern Kerguelen Plateau Rift Zone. The 77°E and 75°E grabens, and the other rift zones on the Kerguelen Plateau, appear to have been formed at approximately the same time, between 72 and 60 Ma. They are all part of an important extensional phase which occurred in the region and mark the beginning of the process which led to the development of the Plate Boundary Rift Zone into the Southeast Indian Ridge, between 46 and 43 Ma. The north‐south trend of the 77°E and 75°E grabens is different from that of the other rift zones, which are oriented northwest‐southeast. This geometry suggests that some strike‐slip motion may have occurred along the north‐south trending grabens as a result of extension on the northwest‐southeast trending rifts, particularly the Southern Kerguelen Plateau Rift Zone. However, since near‐surface extension estimates for the Southern Kerguelen Plateau Rift Zone are small, the strike‐slip motion along the 77°E Graben must be equivalently small. Also, the available seismic data from this graben do not show typical seismic characteristics of a strike‐slip environment, such as zones of compression or flower structures. Thus the results of this work are inconsistent with any model for the development of the South Indian Ocean which requires significant amount of transform motion on the 77°E or 75°E grabens. Finally, the seismic data from this area provide a unique opportunity to compare rifting on an oceanic plateau environment with continental rifting. We find great similarities between the two processes, in the segmentation of the rifts, the asymmetric cross section, and the associated shoulder uplifts.

Capsular polysaccharide is linked to the outer surface of type 6A pneumococcal cell walls

The in situ attachment of capsular polysaccharide of type 6A pneumococci was examined by immunoelectron microscopy using anti-type 6A monoclonal antibody. The result discloses an asymmetrical cross-section of pneumococcal cell walls because capsular polysaccharides are located on the outer surface of the walls only, in contrast to the cell wall polysaccharide, which has been shown to be located on both surfaces.

Application of a refraction method for determining the profile of the index of refraction of fiber light conductors with asymmetric transverse cross sections

Application of a refraction method for determining the profile of the index of refraction of fiber light conductors with asymmetric transverse cross sections

Electron-microscopic investigation of 132Xe ion tracks in a single crystal volume of gypsum

A surface cleavage in an irradiated single crystal of gypsum, crossed by volume tracks of 132 Xe ions in the cleaved plane, has been investigated by transmission electron-microscopy (TEM). It has been found that the most defective region (the core) of a volume track is a hollow channel of asymmetric cross-section found along almost the entire ion range.