Rows Of Elements Research Articles

MULTI-TWISTED ACOUSTIC ARRAY FOR MEDICAL ULTRASOUND

Multiple twisted or rotated arrays are provided. For example, a memory alloy may allow manufacture of multiple rows of elements on a flat substrate. The memory of the alloy is activated to twist different rows in different ways, such as two adjacent substantially parallel but oppositely rotated arrays. By selecting different apertures along a given twist, different planes are scanned due to the difference in direction of the elements of the aperture. By selecting different apertures on differently rotated arrays, a larger volume may be scanned.

INTERACTION OF IDEALIZED URBAN INFRASTRUCTURE AND LONG WAVES DURING RUN-UP AND ON-LAND FLOW PROCESS IN COASTAL REGIONS

This paper reports experimental results of long wave run-up climbing up a 1:40 sloping beach. The resulting maximum run-up is compared with analytical results and a good agreement is found for single sinusoidal waves with uniform wave period and varying amplitude. Subsequently, the interaction with macro-roughness elements on the beach is investigated for different long-shore obstruction ratios. The reduction in wave run-up is expressed by means of a nomogram relating the wave run-up without macro-roughness elements present to those cases where on-land flow is modified by macro-roughness. The presented results mainly focus on a non-staggered and non-rotated macro-roughness
 configuration. In addition to the run-up reduction, surface elevation profiles on the shore are presented, that address the shock wave generation when the wave tongue approaches the first row of macro-roughness elements.

Numerical modeling of diffuse transverse cracks and induced delamination using cohesive elements

This article is devoted to the modeling of spread kind of damages such as matrix cracking and induced delamination in symmetric and asymmetric cross-ply laminates of composite materials using cohesive elements. For matrix crack modeling, parallel rows of cohesive elements are used between every row of 2D elements in 90° layers. Delamination is also modeled by cohesive elements at the 90°/0° interface. Since matrix cracking is a diffuse kind of damage mechanism, application of cohesive elements is not straightforward, and special techniques are necessary to resolve the modeling difficulties. For this purpose, two techniques of “bisecting” and “random distribution of strength of cohesive elements” are proposed here. Both techniques are applied to various symmetric laminates of [0/903]s and [90n/0]s (n = 1 to 3). The predicted stiffness and damage progresses from both techniques are in good agreement with the experimental results. Then, asymmetric cross-ply laminates of [90n/0] (n = 1 to 3) are analyzed to show the capability of this method in progressive damage analyses. The proposed method is less restricted in comparison with available micromechanical methods and is able to predict damage initiation, propagation and damage-mode transition for any symmetric and asymmetric cross-ply sequence. Therefore, this method can be used for development of “in-plane damage” of constitutive laws especially when specimens are subjected to complex loading and boundary conditions.

Flexural vibration analysis of an automobile water pump bearing-rotor system with a modified transfer matrix method

The loading, elastic deformation and hydrodynamic film effect at each rolling element–raceway contact of automobile water pump bearing are analyzed. Based on this analysis, the total radial stiffness, angular stiffness and radial damping of the two rolling element rows are modelled. These stiffness and damping are taken into the transfer matrix to evaluate the lateral vibration characteristics of a rotor-automobile water pump bearing system. The natural frequencies, mode shapes and unbalance responses of the system are calculated. The effects of the pulley and fan unbalances on the system response under different spindle speeds are studied. The calculation results show that the unbalance response of the system can be reduced by fixing the pulley and fan with the initial phase difference between their unbalances to be 180°, and by increasing the pulley unbalance appropriately when keeping the fan unbalance constant.

Definitive Callose Deposition in Tapping Panel Dryness Affected Bark of Hevea brasiliensis

The structural and functional aspects of sieve elements in Tapping Panel Dryness (TPD) affected bark of Hevea brasiliensis, with special reference to definitive callose deposition, have been studied using histochemical methods. The effect of ethephon in definitive callose deposition in TPD affected bark also has been investigated, as the ethylene is reported to have a major role in TPD. The phloem of Hevea is characterized by sieve elements with compound sieve plates. The deposition of definitive callose on the sieve areas following TPD limits the translocation of sap through sieve elements. The amount of functional phloem was narrow and the accumulation of definitive callose was more in the sieve elements of TPD affected bark compared to that of unaffected bark of the same tree and of healthy trees. The affected area showed an increment in deposition of definitive callose in both vertical and horizontal extent of sieve areas; and there was a reduction in length of sieve plate, density of sieve pores, length of inter-sieve area wall, and number of sieve element rows in the inner bark. The lateral walls of non-functional sieve elements became thick and lignified. The anatomical changes in the sieve elements of TPD affected bark suggest that the translocation of phloem sap is regulated by deposition of definitive callose and less differentiation of sieve elements from vascular cambium. The external application of ethephon on bark enhanced the definitive callose deposition on sieve elements. The findings from the study reveal that ethylene plays a major role in the senescence of sieve elements.

Ductile crack growth and constraint in pipelines subject to combined loadings

An important failure mode of offshore pipelines is ductile fracture of the pipe wall triggered by a hypothetical welding defect. In this study, pipelines having an external part-through semi-circumferential crack of various sizes, subject to combined internal pressure and inelastic bending are considered. This is done to assess the response of pipelines during both their installation and operational conditions. Detailed 3D nonlinear finite element (FE) models of pipelines are developed. A row of elements ahead of the initial crack front are modeled using a voided plasticity material model, which enables simulation of crack growth and the subsequent fracture failure mode (denoted by the critical curvature, κ crit ). After discussing the typical response characteristics of such pipelines, the FE model is used to parametrically investigate the influence of varying pipe and crack dimensions, and also the internal pressure levels, on κ crit . In the second part of this paper, the crack tip constraint ahead of a growing crack in such pipes is evaluated and systematically compared to the crack tip constraint of both the traditionally used deeply cracked Single Edge Notch Bend (SENB) specimens and the constraint-matched Single Edge Notch Tensile (SENT) specimens. This is achieved by comparing the crack resistance curves ( R-curves) along with stress triaxiality and equivalent plastic strain fields evaluated ahead of a growing crack of the three systems. The results present grounds for justification of usage of SENT specimens in fracture assessment of such pipes as an alternative to the traditional overly conservative SENB specimens.

Algebraic/transcendental disturbance growth behind a row of roughness elements – ERRATUM

It has come to our attention that in the printed version of Goldstein et al. (2011) figures 8, 9, 10 and 11 were printed in black and white when they should have appeared in colour. The reader is referred to the online version of this article where the colour is correct for all figures.

Algebraic/transcendental disturbance growth behind a row of roughness elements

This paper is a continuation of the work begun in Goldstein et al. (J. Fluid Mech., vol. 644, 2010, p. 123), who constructed an asymptotic high-Reynolds-number solution for the flow over a spanwise periodic array of relatively small roughness elements with (spanwise) separation and plan form dimensions of the order of the local boundary-layer thickness. While that paper concentrated on the linear problem, here the focus is on the case where the flow is nonlinear in the immediate vicinity of the roughness with emphasis on the intermediate wake region corresponding to streamwise distances that are large in comparison with the roughness dimension, but small in comparison with the distance between the roughness array and the leading edge. An analytical O(h2) asymptotic solution is obtained for the limiting case of a small roughness height parameter h. These weakly nonlinear results show that the spanwise variable component of the wall-pressure perturbation decays as x−5/3 ln x when x → ∞ (where x denotes the streamwise distance scaled on the roughness dimension), but the corresponding component of the streamwise velocity perturbation (i.e. the wake velocity) exhibits an O(x1/3 ln x) algebraic/transcendental growth in the main boundary layer. Numerical solutions for h = O(1) demonstrate that the wake velocity perturbation for the fully nonlinear case grows in the same manner as the weakly nonlinear prediction – which is considerably different from the strictly linear result obtained in Goldstein et al. (2010).

Influences of eccentric unbalances on loads and life of auto water pump bearing

The life of auto water-pump bearing is closely related to its loads which are affected by the eccentric unbalances of rotational components in the structure system of the bearing. However, since the bearing structure in auto water-pump is complicated, the exact load calculations and the life prediction for this kind of bearing are difficult. In this paper, the WR3258152 auto water-pump bearing is investigated. The load and life calculation models for the bearing are developed with considering the eccentric unbalances of the cooling fan and the driving wheel. The influences of the fan and the wheel unbalances on the loads and life of the bearing are studied. The calculation and analysis results show that the radial loads on rolling element rows of the auto water-pump bearing fluctuate significantly under the actions of the fan and the wheel unbalances and the bearing life reduces regularly with the eccentric unbalances changing.

Beamforming for vibro-acoustography using a 1.75D array transducer.

Vibro-acoustography is an ultrasound-based imaging modality that maps the acoustic response of an object induced by acoustic radiation force. The method employs two ultrasound beams with frequencies separated by a small difference, typically in the kilohertz range. Using a 1.75D array transducer, which has multiple rows of elements, offers an advantage over linear array transducers because it allows for focusing in the elevation direction. We have performed simulations of different arrangements for the apertures assigned to the two ultrasound frequencies and evaluated resolution and sidelobe levels for different arrangements. However, the large size of the elements produces grating lobes in the transmitted fields. We will describe metrics for evaluating grating lobe levels compared to the main lobe of the transmitted field as a quantitative approach to optimize aperture design. We present experimental measurements of the transmitted field and compare with simulation results. Finally, we present imaging results from phantom experiments. This beamforming study is directed toward improving vibro-acoustography image formation using a General Electric Vivid 7 scanner for breast and thyroid imaging. [Mayo Clinic and two of the authors have potential financial interest related to devices or technology referenced above. Work supported by NIH Grant No. R21CA121579 and AIUM Award No. AIUM-EER#1.]

Fast array processor for the noiselet reverberation model.

The noiselet reverberation model, instead of transmitting the pulse itself, transmits a superposition of many copies of the pulse, each copy with a random amplitude and phase. This allows the simulation to mimic the point scatterer method without requiring a prohibitively large number of scatterers. It uses the GRAB ray model to introduce the propagation information. It provides a real-time high-fidelity simulation, providing element-level time series as an output for a planar array of receivers. However, it is presently limited by the phase shift calculations required by the frequency-domain beamformer to about 20 receivers without an unacceptable trimming of the number of rays used. Here, an approach is demonstrated that significantly improves the speed of this computation by identifying those receivers requiring the same phase shift to within a given specified error, such that only a single phase shift computation is required. These receivers fall onto a finite width strip, or quasi stave, that is not required to be parallel to element rows or columns. Along with providing a significant speed-up to the calculation, the approach becomes more efficient as the number of receivers increases, thereby allowing real time simulations using receiver arrays of over 100 elements.

The long range persistence of wakes behind a row of roughness elements

We consider a periodic array of relatively small roughness elements whose spanwise separation is of the order of the local boundary-layer thickness and construct a local asymptotic high-Reynolds-number solution that is valid in the vicinity of the roughness. The resulting flow decays on the very short streamwise length scale of the roughness, but the solution eventually becomes invalid at large downstream distances and a new solution has to be constructed in the downstream region. This latter result shows that the roughness-generated wakes can persist over very long streamwise distances, which are much longer than the distance between the roughness elements and the leading edge. Detailed numerical results are given for the far wake structure.

Pharmacognostical studies ofBauhinia variegatalinn root

The present study deals with the macroscopical and microscopical studies of Bauhinia variegata Linn root. Some distinct and different characters were observed with sections of young, thick and very old and thick roots. The anatomy of the root was studied by taking transverse section. Secondary phloem and secondary xylem were seen distinctly. Secondary phloem had fairly wide rays, dense masses of phloem Þ bers and radial rows of phloem elements. Secondary xylem had much wider, thin-walled vessels which were either solitary or in radial multiples. The xylem Þ bers constituted gelatinous type and normal type. Calcium oxalate crystals were predominantly prismatic type. Powder microscopical examination showed presence of xylem parenchyma cells, xylem Þ bers and vessel elements. Physicochemical parameters and preliminary phytochemical studies of the root powder were also carried out. The present study on pharmacognostical investigation of B. variegata L. root might be useful to supplement information in regard to its identiÞ cation parameters assumed signiÞ cantly in the way of acceptability of herbal drugs in present scenario lacking regulatory laws to control quality of herbal drugs. Key words: Bauhinia variegata, root

Distribution of groups I and II elements between liquidus phases of fluorine-saturated Si-Al-Na-K-Li-H-O system

Experimental data allow modeling the behavior of the named elements during formation of fluorine- saturated leucocratic rocks of silicic and alkaline compositions. The distribution of alkaline and alkaliearth elements is discussed at equilibrium between the silica-alumina melt with fluoride phases (crystalline and liquid) and with feldspar. Cryolite crystals form during saturation of silica-alumina melt of normal alkalinity with fluorine. Continuous solid solution of sodium-potassium cryolite is stable at 800°C. The equilibrium between melt and crystals continues up to the maximum molar fraction of 0.1 lithium end member in cryolite, at which two fluoride phases (crystalline and liquid) coexist with the silica-alumina melt of fixed composition. Separation of salt melts during late differentiation stages of granite and alkaline rocks is a regular process continuing the natural evolution of ore-magmatic systems. At equilibrium of two liquid phases, the silica phase is relatively enriched in potassium, and the fluoride phase is substantially enriched in sodium. This detected effect is the only currently possible mechanism for the occurrence of the potassium differentiation trends of granite melts. All effects related to crystallization cause enrichment in sodium. In other cases (with Ca, Sr, Mg, Rb, and Cs), separation of the second liquid phase acts in the same direction and enhances the action of crystallization. Comparison between partition coefficients allows derivation of the following affinity rows of alkaline elements for fluoride melt: Li > Na > K > Rb≈Cs and Mg > Ca > Sr > Ba. Hence, the known rule for joining strong bases with strong acids and weak bases with weak acids is fulfilled.

IMPLICATIONS OF RELATIVISTIC CONFIGURATIONS AND BAND STRUCTURES IN THE PHYSICS OF BIO-MOLECULES AND SOLIDS

Beyond the second row of elements in the Mendeleev periodic table, the consideration of the relativistic effect is important in determining proper configurations of atoms and ions, in many cases. Many important quantities of interest in determining physical and chemical properties of matter, such as the effective charge, root mean square radii, and higher moments of radii used in many calculations, e.g. in the determinations of legend stabilization bond energies depend on whether the treatment is relativistic or not. In general, these quantities for a given l-orbital having two different j-values, e.g. [Formula: see text] and [Formula: see text], differ from each other, hence, making it necessary to treat them as separate orbitals. This also necessitates characterizing bands with their j-values in many instants and not l-values, particularly for “d” and f-orbitals. For example, in Au , [Formula: see text] and [Formula: see text] are to be dealt with as two distinct bands. The observed enhancement of laser induced field emission in W, which is not understood in terms of non-relativistic band-structures, can be explained in terms of the expected relativistic band structure. Spin-orbit coupling, which is the manifestation of the relativistic effect, is a prime factor in facilitating intersystem crossing in bio-molecules.

Stability of the laminar boundary layer flow encountering a row of roughness elements: Biglobal stability approach and DNS

The stability of the laminar boundary layer developing on a flat plate in the presence of a periodic row of roughness elements is investigated. A Direct Numerical Simulation is performed to compute the steady flow downstream of the roughness elements, which contains a pair of two counter-rotating streamwise vortices per element, which can be considered as a “pre-streaky” structure. The linear stability of this base flow is analyzed by means of the so-called “biglobal” stability approach. Three-dimensional eigenmodes are found, which are shown to be the continuation of the Tollmien–Schlichting waves present in the case of an unperturbed boundary layer. Moreover, a stabilizing effect due to the roughness-induced vortices is found. A Direct Numerical Simulation of the interaction between a two-dimensional Tollmien–Schlichting wave and the roughness array is also performed. The computed perturbation traveling downstream of the roughness elements is shown to be a linear combination of the biglobal eigenmodes.

Assembling ordered hexagonal fiber and capillary structures

Using as an example the simplest shape of a truncated hexagon, which differs from a regular hexagon by the absence of one row of elements on one side, this paper discusses assembly errors and the causes that generate them. A general-purpose method for the oriented assembly of an ordered hexagonal structure is proposed that can be used in both a one-stage and in a two-stage process. It essentially consists of introducing additional relief into the original shape that provides reliable identification of the position of the assembly element and that eliminates the effect of azimuthal and mirror rotations. A patent has been obtained on the method, and its efficiency has been confirmed by fabricating fiber structures with a resolution of 90 line/mm, using the two-stage process.

WE‐C‐L100J‐04: The Solid State X‐Ray Image Intensifier (SSXII): A Next‐Generation High‐Resolution Fluoroscopic Detector System

Purpose: Present the design for the new SSXII high‐resolution fluoroscope capable of overcoming lag, noise, and resolution limitations of current flat‐panel devices (FPDs). Method and Materials: The SSXII consists of an array of modules each featuring an electron multiplying (EM) CCD which views a structured phosphor through a fiber‐optic taper (FOT). The EMCCD operates like a standard frame‐transfer CCD; however, an additional row of multiplication elements enables on‐chip signal gains up to 2000X to overcome subsequent instrumentation‐noise degradation. The SSXII therefore has quantum‐limited performance at both fluoroscopic exposures with moderate gain, and radiographic exposures with low gain. The SSXII array design, through pixel binning and module selection, will enable rapid sequence and fluoroscopic imaging for either the full field‐of‐view (FOV) or high‐resolution regions‐of‐interest (ROIs). Results: A SSXII module was assembled with direct fiber‐optic coupling of the 350 micron thick CsI(Tl) phosphor and the EMCCD (Texas Instruments TC285SPD chip with 1004×1002 pixels). Operation at fluoroscopic and angiographic exposure levels was verified experimentally for gains of ∼80X and 1X, respectively, demonstrating sequences of a moving stent with no lag and bar‐pattern resolution up to 20 1p/mm with a 1:1 FOT. An array of four modules each with 6:1 FOTs will have an effective pixel size of 48 microns covering a FOV of 10×10 cm, sufficient for region‐of‐interest and neurovascular imaging. Larger arrays may be constructed to satisfy both cardiac imaging and general fluoroscopic applications. Module alignment, digital stitching, and distortion correction issues are being addressed. Conclusion: When assembled in an array of sufficient size, the new SSXII can be used in the same applications as current FPD's with advantages of high frame rates with no lag, high resolution due to the smaller pixels possible, and low‐effective‐noise, quantum‐limited fluoroscopic performance due to the on‐chip gain.(Support: UB Foundation, NIH grants R01‐EB002873, R01‐NS43924).

Hybrid reordering strategies for ILU preconditioning of indefinite sparse matrices

Incomplete LU factorization preconditioning techniques often have difficulty on indefinite sparse matrices. We present hybrid reordering strategies to deal with such matrices, which include new diagonal reorderings that are in conjunction with a symmetric nondecreasing degree algorithm. We first use the diagonal reorderings to efficiently search for entries of single element rows and columns and/or the maximum absolute value to be placed on the diagonal for computing a nonsymmetric permutation. To augment the effectiveness of the diagonal reorderings, a nondecreasing degree algorithm is applied to reduce the amount of fill-in during the ILU factorization. With the reordered matrices, we achieve a noticeable improvement in enhancing the stability of incomplete LU factorizations. Consequently, we reduce the convergence cost of the preconditioned Krylov subspace methods on solving the reordered indefinite matrices.

Atom–Molecule Interactions on Transition Metal Surfaces: A DFT Study of CO and Several Atoms on Rh(100), Pd(100) and Ir(100)

Density functional theory (DFT) calculations have been performed to determine the interaction energy between a CO probe molecule and all atoms from the first three rows of the periodic table coadsorbed on Rh(100), Pd(100) and Ir(100) metal surfaces. Varying the coverage of CO or the coadsorbed atom proved to have a profound effect on the strength of the interaction energy. The general trend, however, is the same in all cases: the interaction energy becomes more repulsive when moving towards the right along a row of elements, and reaches a maximum somewhere in the middle of a row of elements. The absolute value of the interaction energy between an atom-CO pair ranges from about -0.40 eV (39 kJ mol(-1)) attraction to +0.70 eV (68 kJ mol(-1)) repulsion, depending on the coadsorbate, the metal and the coverage. The general trend in interaction energies seems to be a common characteristic for several transition metals.