Axial Patterns Research Articles

Variations of wood basic density with tree age and social classes in the axial direction within Pinus massoniana stems in Southern China

Reliable estimates of wood density (WD) within individual trees could maximize the value of Pinus massoniana for specific end-use. We examined and quantified the axial patterns of WD in trees with different social status in the stands. Wood disks were sampled at the bottom, breast height, and middle of each 1-m sections from 108 stems, harvesting from three social classes in subtropical forests. A mixed-effects model was designed to quantify axial variation. The WD at different height was significantly different from the whole-stem WD (WWD) except the relative height of 0.1. An overall decrease of 133.8 kg m−3 in WD was found from stem base to top. WD was significantly influenced by relative heights, tree age, and social class. WD of each relative height in mature trees was significantly higher than that of younger trees. Tree social class can affect WD development in the axial direction at age classes 2 and 3. Combining the fixed plus random effects, the final model explained 91 % of the observed variation in WD. The WD development patterns in the axial direction vary considerably among tree age, diameter at breast height, and social class. To distinguish and supply timber for specific end-uses, we should use the axial variation in disk WD (DWD) instead of WWD directly. The accurate predictions of WD provided by the model could be used to optimally classify logs into different product classes and maximize economic benefits. We can use DWD at the relative height of 0.1 instead of WWD of a single tree.

Comparison between experimentally measured flow patterns for straigth and helical type graft

The long-term success of arterial bypass surgery is often limited by the progression of intimal hyperplasia at the anastomosis between the graft and the native artery. The experimental models were manufactured from glass tubing with constant internal diameter of 8 mm, fashioned into a straight configuration and helical configuration. The aim of this study was to determine the three-dimensional flow structures that occur at the proximal anastomosis under pulsatile flow conditions, to investigate the changes that resulted from variations in the anastomosis angle and flow division, and to establishing the major differences between the straight and helical graft. In the anastomosis domain, a strong region of recirculation is observed near the occluded end of the artery, which forces the flow to move into the perfused host coronary artery. The proximal portion of the host tube shows weak counter-rotating vortices on the symmetry plane. The exact locations and strengths of the vortices in this region are only weakly dependent on Re. A detailed comparison of experimentally measured axial velocity patterns for straight and helical grafts confirm the very strong nature of the secondary flows in the helical geometry. The helical configuration promotes the mixing effect of vortex motion such that the flow particles are mixed into the blood stream disal to the anastomotic junction.

Numerical analysis for curved vortex tube optimization

Vortex tubes hold promise for developing low cost refrigeration and air conditioning systems. They do not require the use of any moving parts. Moreover, they also do not consume energy when compressed air is available. In this study, a CFD is conducted to determine the effect of vortex tube curvature on their performance. A three dimensional CFD model that utilizes the RNG k-ε turbulence model is employed for the numerical simulations. The flow and temperature field in curved vortex tubes with curvature angles are simulated in the range of 0° (straight) to 150°. The tangential (swirl), axial velocity components and flow patterns including secondary circulation flow are evaluated. The numerical simulations are verified through comparison with experimental data reported in the literature. The results are then used for evaluating the coefficient of performance (COP) of the vortex tube as a cooling solution.

Abnormal Axial Rotations in TKA Contribute to Reduced Weightbearing Flexion

Previous in vivo fluoroscopy studies have documented that axial rotation for patients having a TKA was significantly less than those having a normal knee. In fact, many subjects having a TKA experience a reverse axial rotation pattern where the femur internally rotates with increasing flexion. However, no previous studies have been conducted to determine if this reverse axial rotation pattern affects TKA performance. The purposes of this study were: (1) Do normal and reverse axial rotation patterns of a TKA affect the maximum flexion angle postoperatively? (2) Does the axial rotation angle of the knee at maximum flexion during weightbearing impact the magnitude of the maximum flexion achieved in weightbearing? One hundred twenty patients having TKA, previously analyzed under in vivo conditions using fluoroscopy and a three-dimensional model-fitting software package, were further evaluated to determine if reverse axial rotation patterns limit weightbearing TKA flexion. In this retrospective cohort, we identified 58 patients who had a normal axial rotation pattern (greater than 15° normal rotation). Sixty-two patients experienced greater than 3° of reverse axial rotation, defined as internal rotation of the femur relative to the tibia. Patients having a normal axial rotation achieved greater weightbearing knee flexion than those with reverse axial rotation (115° versus 109°, p = 0.02). Additionally, patients with greater than 3° of normal axial rotation at maximum flexion had more flexion than those with less than 3° of normal axial rotation at ending flexion (115° versus 107°, p < 0.001). These findings show reverse axial rotation and a smaller magnitude of normal axial rotation reduce weightbearing knee flexion. This is likely the result of increased posterior movement of the lateral condyle and is an important consideration in future implant designs.

Transition of axial segregation patterns in a long rotating drum

Axial segregation of a bidisperse mixture of particles in a long rotating drum is studied using the discrete element method. Simulation results show that particle interaction is responsible for axial segregation, the patterns of which are influenced by the end wall effect. Axial segregation patterns transform under competing influences of the end walls and the particle interaction forces. The two influential factors vary with various rotational speeds and end wall friction levels. The result is the transition of different axial segregation patterns: two large-particle bands at both ends, two small-particle bands at both ends, or a random segregation pattern where either a large-particle band or small-particle band may appear at either end.

A Salamander's Flexible Spinal Network for Locomotion, Modeled at Two Levels of Abstraction

Animals have to coordinate a large number of muscles in different ways to efficiently move at various speeds and in different and complex environments. This coordination is in large part based on central pattern generators (CPGs). These neural networks are capable of producing complex rhythmic patterns when activated and modulated by relatively simple control signals. Although the generation of particular gaits by CPGs has been successfully modeled at many levels of abstraction, the principles underlying the generation and selection of a diversity of patterns of coordination in a single neural network are still not well understood. The present work specifically addresses the flexibility of the spinal locomotor networks in salamanders. We compare an abstract oscillator model and a CPG network composed of integrate-and-fire neurons, according to their ability to account for different axial patterns of coordination, and in particular the transition in gait between swimming and stepping modes. The topology of the network is inspired by models of the lamprey CPG, complemented by additions based on experimental data from isolated spinal cords of salamanders. Oscillatory centers of the limbs are included in a way that preserves the flexibility of the axial network. Similarly to the selection of forward and backward swimming in lamprey models via different excitation to the first axial segment, we can account for the modification of the axial coordination pattern between swimming and forward stepping on land in the salamander model, via different uncoupled frequencies in limb versus axial oscillators (for the same level of excitation). These results transfer partially to a more realistic model based on formal spiking neurons, and we discuss the difference between the abstract oscillator model and the model built with formal spiking neurons.

High performance structured platelet milli-reactor filled with supported cobalt open cell SiC foam catalyst for the Fischer–Tropsch synthesis

The Fischer–Tropsch synthesis (FTS) was evaluated on a 30wt.% Co catalyst promoted with 0.1wt.% of Ru supported on a silicon carbide (SiC) foam in a platelet structured milli-reactor (PSR). The FTS was tested under isothermal conditions according to the Mear’s criterion. The tuneable morphology of the open cell foam (cell size, macroscopic porosity, strut diameter) allows an adjustment of both axial and radial flow patterns in the reactor and ensures local fluid recirculation, which are favorable to heat and mass transfer. The large pore size, i.e. meso- and macro-pores of the support allows a rapid escaping of the liquid products leading to a high FTS activity as well a good C5+ selectivity. The catalytic results obtained in the platelet milli-reactor were compared with those obtained in a ‘conventional’ packed bed tubular reactor (TR). The PSR shows a better FTS activity compared to that obtained in the TR and the FTS activity steadily increases with increasing the GHSV. Finally, a remarkably high C5+ selectivity (∼93%) and a negligible amount of methane formation (∼1%) were also obtained at a GHSV of 1900h−1 in the PSR.

Diffraction of fast H atoms during grazing scattering from an Al2O3(1 1 [formula omitted] 0) surface

H atoms with energies up to 1keV were scattered under a grazing angle of incidence from an Al2O3(112¯0) surface. After preparation of the target by annealing at a temperature of 1700°C well defined angular distributions for scattered projectiles are observed showing for scattering in the regime of axial channeling rich diffraction patterns. For scattering along the low indexed [1¯100] direction diffraction spots are arranged on a circle which is attributed to full coherence preserved during the collision with the surface. By an azimuthal rotation of the target surface by some degrees Laue circles of higher orders can be observed which is accompanied with a substantial enhancement of resolution for periodicity intervals of the target surface. This is demonstrated by results for the (12×4) phase of the Al2O3(112¯0) surface which indicate an overall transfer width for fast atom diffraction of several 100Å.

Behaviour of a binary particle system under the effects of simultaneous vertical vibration and rotation

We performed experiments to investigate the effects of simultaneous vertical vibration and rotation (around a vertical axis) on a binary particle system. In particular, the effects of vibration frequency f, dimensionless acceleration Γ, rotation angle velocity ω, and the total mass m of the particle system on the final separation results are investigated. The system exhibited transitional Brazilian Nut (BN) separation patterns in both the vertical and axial directions. The coupling of vertical and axial separation mechanisms determined the final spatial separation state. We defined the vertical and axial separation parameters λz and λr between −1 for Complete Reversed BN (RBN) and 1 for Complete BN to describe the separation states quantitatively. These experiments suggested that when no rotation is applied, the system exhibits mono-directional relations with f and Γ mainly. BN tendency is enhanced when f increases at a constant Γ, but is reduced when Γ increases at a constant f, and vice versa. When ω increases at constant f and Γ, the value of λz first rises as a result of enhanced BN tendency and then drops in response to vertical rotation. As ω increases, the surface of the particle mixture becomes hollow, and the λz–ω curve is partly dispersed. After the hollow touches the container bottom, the curve becomes fully dispersed. ω, f, Γ, and m all have significant effects on the final vertical and axial separation patterns. Stronger vibration generally increases RBN/Axial RBN, whereas stronger rotation helps form BN/Axial BN. We also established a geometrical model of the separation states to study the effect of ω, f, Γ, and m on the final separation results in delicate mathematical descriptions. This model agreed well with the experimental outcomes.

Tri-band circularly polarized annular slot antenna for GPS and CNSS applications

A novel single-feed tri-band circularly polarized (CP) annular slot antenna is presented. The antenna structure is composed of two nonconcentric annular slots that are fed by an L-shaped series step impedance microstrip line configuration. The proposed antenna is designed to operate at the L 1 and L 2 bands of the global positioning system and the operating band of the compass navigation satellite system. Compared to the most of the previously reported tri-band CP antenna structure, the proposed antenna has low profile, compact size, and easy fabrication on the single-layer PCB. The measured results show that the impedance bandwidths are good for all bands. The axial ratio bandwidth and radiation patterns are also measured at the three resonant frequencies. The proposed compact tri-band CP antenna design is suitable for mounting onto the mobile communication devices and portable positioning systems.

Influence of the Narrow{111}Planes on Axial and Planar Ion Channeling

We report channeling patterns where clearly resolved effects of the narrow {111} planes are observed in axial and planar alignments for 2 MeV protons passing through a 55 nm [001] silicon membrane. At certain axes, such as <213> and <314>, the offset in atomic rows forming the narrow {111} planes results in shielding from the large potential at the wide {111} planes, producing a region of shallow, asymmetric potential from which axial channeling patterns have no plane of symmetry. At small tilts from such axes, different behavior is observed from the wide and narrow {111} planes. At planar alignment, distinctive channeling effects due to the narrow planes are observed. As a consequence of the shallow potential well at the narrow planes, incident protons suffer dechanneled trajectories which are excluded from channeling within the wide planes, resulting in an anomalously large scattered beam at {111} alignment.

Su1425 Effect of Body Mass Index (BMI) and Procedure Difficulty on Force Applied During Colonoscopy

Colonoscopy requires a skilled endoscopist to advance and withdraw the instrument through a series of fixed and stationary loops. Procedure difficulty may depend on the patient's physical characteristics such as BMI and colonic redundancy. Prior studies of force application indicate that forces vary by endoscopist, anesthesia and gender. The purpose of this analysis was to measure differences in axial and longitudinal force patterns in obese, overweight and normal weight patients as well as those classified as having difficult colonoscopies.

Experimental study of density segregation at end walls in a horizontal rotating cylinder saturated with fluid: friction to lubrication transition

What is the effect of interstitial fluid viscosity on granular density segregation in a horizontal rotating cylinder? We conducted experiments in the rolling regime with equal amounts of equal sized high and low density, nearly spherical granular particles saturated with air, water, and water-glycerin mixtures. We held particle density, rotation rate and characteristic length scale constant to highlight differences due purely to the interstitial fluid. Images of the granular flow at an end wall were used to determine radial and axial density segregation rates and patterns. Over a four decade change in viscosity, segregation rates varied by only a factor of two. However, for ratios of lubrication to frictional stresses above one, segregation rates decreased by about 30%, and we observed several notable phenomena in the segregation pattern formation. These were a creeping mode of radial density segregation, a change in shape of the granular bed to kidney shaped from flat, and for cylinders more than half full the typically reported unsheared central portion of the granular bed (often referred to in the literature as a core region) was disrupted by a wavy instability where the rate of disappearance of the core region decreased as the fill level increased.

Axial multiple foci of radially polarized hollow Gaussian beam

Axial multiple foci patterns of radially polarized hollow Gaussian beam (HGB) with radial wavefront distribution is investigated theoretically. The wavefront phase distribution is cosine function of radial coordinate. Simulation results show that the multiple foci patterns can be adjusted considerably by the beam order of HGB and cosine parameter that indicates the phase change degree. The foci number fluctuates on increasing cosine parameter for certain beam order. And when the beam order is small, there occur five foci in focal region, and the cases are more frequently than that under the condition of higher beam order. Gradient force distributions are also given to show that the multiple foci of radially polarized HCB may be applied to construct tunable optical traps. OCIS codes: 140.3300, 260.5430, 140.7010.

Progressive disc degeneration at C5–C6 segment affects the mechanics between disc heights and posterior facets above and below the degenerated segment: A flexion–extension investigation using a poroelastic C3–T1 finite element model

Disc degeneration (DD) is often accompanied by a height reduction of the anterior and posterior discs (AD and PD, respectively), and this affect the way in which articulating posterior facets (PFs) come into contact during physiological motions. Any increase in the contact between overlapping articulating facet surfaces increases PF loading. Development of adjacent segment disease is a significant clinical concern. It still is not clear how degenerative motion changes in AD and PD heights affect the mechanics of adjacent segment discs and facets. We hypothesized that changes in axial height patterns (in the AD and PD) at the degenerated C5–C6 disc-segment would affect axial height patterns (in the AD and PD) above and below the degenerated disc-segment. A previously validated poroelastic three-dimensional finite element (FE) model of a normal C3–T1 segment was used. Two additional C3–T1 models were built with moderate and severe DD at C5–C6. The three FE models were evaluated in flexion and extension. With progressive C5–C6 DD, AD and PD flexibility (axial deformation or elongation per unit load) at C5–C6 decrease with a compensatory corresponding flexibility increase in adjacent segments (normal), whereas PF loading increased at all segments only during extension. Changes in AD and PD flexibility and PF loading were higher at inferior segments than at superior segments. This study confirmed the hypothesis that the anterior and posterior discs and articulating facets of cervical spine segments are affected during flexion and extension motions when a disc-segment degenerates. Motion changes involving a higher PD height loss, both at the degenerated and adjacent segments, would further increase PF loading along the posterior spinal column – a possible mechanism for the dysfunctioning of the facet joints. The current data should be compared to other multi-segmental cervical spine experiments.

Versatilidade do retalho bilobado

BACKGROUND: The bilobed flap is a double transposition flap. Its geometric structure enables a better distribution of tensile forces along its rotation axis, avoiding the skin distortions and redundancy generated by other flaps or primary sutures. The bilobed flap can be made with axial and random vascular patterns, depending on the anatomical region. METHODS: This study reviews 45 surgical cases, describing in detail the technique used to produce the bilobed flap. Defects were classified as small, medium, or large, and several clinical cases are presented in order to explore the versatility of this flap in various etiological diagnoses and anatomical sites. RESULTS: In 93% of the cases, the bilobed flap was used for oncologic reconstructions, and the cephalic segment was affected in 71% of cases. Postoperative complications were absent in 85% of the cases. The rates of infection, trapdoor scar, and epitheliosis and necrosis were 4.4%, 4.4%, and 11.1%, respectively. The overall complication rate was 15%. However, these complications did not compromise the clinical evolution of the cases, and the bilobed flap proved to be resolutive in various situations, providing good functional and aesthetic results. CONCLUSIONS: The bilobed flap is versatile, easy to implement, and is widely used in plastic surgery.

CFRP-Confined Square RC Columns. II: Cyclic Axial Compression Stress-Strain Model

AbstractFor the seismic design of fiber reinforcement polymer (FRP) confined reinforced concrete (RC) columns, the development of an accurate axial stress-strain model that considers cyclic compression is necessary. In light of such a demand, this paper presents a cyclic axial stress-strain model for FRP-confined RC square columns. The model is informed from physical observations and test measurements obtained from an experimental investigation reported in the companion paper, in which FRP-confined square unreinforced and reinforced concrete columns of larger size under varying cyclic axial compression patterns were tested. In the current paper, the proposed stress-strain model is presented and it consists of three main components, namely (1) a monotonic stress-strain model to describe the envelope curve, (2) a polynomial expression for the unloading path, and (3) a straight line for the reloading path. The influence of internal longitudinal and hoop steel reinforcement is also considered in the proposed ...

Dispersion Control in Plasmonic Open Nanocavities

We experimentally demonstrate the dependence of plasmonic resonant properties on cavity height in open circular cylinder nanocavities as a result of a strong three-dimensional confinement of the electromagnetic field, which shows a new way to tailor the dispersion of surface plasmon polaritons in cavities. The azimuthal and the axial symmetric plasmonic mode patterns are directly observed at resonant wavelengths using cathodoluminescence spectroscopy. Plasmonic modes and optical vertical cavity modes can be simultaneously excited and can coexist in a nanocavity with sufficient height. The highest quality factor, which is up to 73, is obtained in a 500 nm high cavity. The smallest mode volume is only 0.031 λ(SPP)(3), and the corresponding Purcell factor is 71. Open nanocavities provide space for the interaction between an optical emitter and a confined electromagnetic field. Many applications can be expected, such as plasmonic light-emitting devices and nanolasers.

Identifying multiple axial load patterns using measured vibration data

Multiply redundant frames possess as many linearly independent axial load patterns as their degree of static indeterminacy. Any state of equilibrium can be described as the linear sum of these axial load patterns. As a frame is loaded in the multiple patterns, the changes in member axial loads affect the frame frequencies and mode shapes in a complicated way through geometric stiffening. By representing this behaviour in a finite element model (FEM), it is possible to measure the dynamic characteristics of a physical frame, update the axial loads in the FEM until the difference between measured and model frequencies is minimised and thus infer the member axial loads. What is updated is the factors on the axial load patterns and this is done iteratively using traditional model updating (Newton's method). Thus, all member axial loads can be identified using just a set of updating parameters equal in number to the degree of static indeterminacy. A numerical simulation and, for the first time, an implementation on a physical realisation of a multiply redundant frame using measured vibration data are presented herein and show that member loads can be identified to an encouraging degree of accuracy. Beneficial strategies such as formulating the problem on an orthonormal basis for the axial load patterns and a ‘modal tagging’ scheme, which helps to conserve the strength of the necessary, but otherwise typically compromised, pairing of mode shapes of the FEM to those measured, are discussed.

Numerical simulation of novel axial impeller patterns to compress water vapor as refrigerant

Through means of 3-D CFD (Computational Fluid Dynamics) method, a novel axial compressor with different impeller shapes compressing water vapor as refrigerant was investigated. The numerical simulation focuses on the fluid flow from compressor impeller inlet to outlet. The overall performance level and range are predicted. Different blade patterns with different hub sizes were compared regarding the aerodynamic performance. Independent of the blade pattern, in this numerical investigation the largest hub diameter shows the highest pressure ratio and efficiency at narrowest operating range.