Series Of Plates Research Articles

Foot Sole Contact Forces vs. Ground Contact Forces to Obtain Foot Joint Moments for In-Shoe Gait-A Preliminary Study.

In-shoe models are required to extend the clinical application of current multisegment kinetic models of the bare foot to study the effect of foot orthoses. Work to date has only addressed marker placement for reliable kinematic analyses. The purpose of this study is to address the difficulties of recording contact forces with available sensors. Ten participants walked 5 times wearing two different types of footwear by stepping on a pressure platform (ground contact forces) while wearing in-shoe pressure sensors (foot sole contact forces). Pressure data were segmented by considering contact cells' anteroposterior location, and were used to compute 3D moments at foot joints. The mean values and 95% confidence intervals were plotted for each device per shoe condition. The peak values and times of forces and moments were computed per participant and trial under each condition, and were compared using mixed-effect tests. Test-retest reliability was analyzed by means of intraclass correlation coefficients. The curve profiles from both devices were similar, with higher joint moments for the instrumented insoles at the metatarsophalangeal joint (~26%), which were lower at the ankle (~8%) and midtarsal (~15%) joints, although the differences were nonsignificant. Not considering frictional forces resulted in ~20% lower peaks at the ankle moments compared to previous studies, which employed force plates. The device affected both shoe conditions in the same way, which suggests the interchangeability of measuring joint moments with one or the other device. This hypothesis was reinforced by the intraclass correlation coefficients, which were higher for the peak values, although only moderate-to-good. In short, both considered alternatives have drawbacks. Only the instrumented in-soles provided direct information about foot contact forces, but it was incomplete (evidenced by the difference in ankle moments between devices). However, recording ground reaction forces offers the advantage of enabling the consideration of contact friction forces (using force plates in series, or combining a pressure platform and a force plate to estimate friction forces and torque), which are less invasive than instrumented insoles (which may affect subjects' gait).

Numerical Investigation of Parameters Affecting Energy Losses in Multi-Stage Perforated Plates

Abstract Perforated plates are commonly used for flow control in pressurized systems. In different industrial applications, these devices are also used in series (multistage perforated plates) to manage high-pressure drop or reduce cavitation occurrence in industrial pipelines and enhance efficiency of gas turbines in power plants. In some specific conditions, the installation of perforated plates in series is a simple and cost-effective solution that increases plant efficiency. However, the large number of design parameters complicates the search for the optimal solution. With the aim of improving the knowledge of the most relevant design parameters, in the present investigation, the dissipation characteristics of multistage perforated plates are studied. Specifically, the analysis of the dependence of the pressure loss coefficient Eu on relative spacing and hole alignment for two subsequent identical plates is performed with CFD approach. Eight plates with different characteristics such as porosity, thickness, diameter, position, and number of holes are studied. The considered porosities vary in a range of 0.3–0.5, the ratio between plate thickness and hole diameter ranges between 0.7 and 1.3, and the number of holes between 4 and 26. A critical spacing between the plates, beyond which the pressure losses are independent of the alignment of the holes, has been calculated. The results obtained are relevant for a deeper understanding of the complex phenomenon of multistage perforated plates and can be used for the design and the installation of these devices commonly used in different engineering applications.

Study of a piezoelectric plate based self-sustained electric and electromechanical oscillator

This work deals with the electrical characterization of a piezoelectric plate and its use to generate self-sustained electrical and mechanical oscillations. An experimental frequency-impedance curve of the piezoelectric plate is obtained leading to the electric equivalent of the piezoelectric plate constituted of a capacitive branch in parallel with many RLC resonant branches. The values of the electric components for each branch are determined using the resonant and anti-resonant frequencies. It is demonstrated theoretically that these branches can be understood in terms of vibration modes of the plate; each of which has its own resonant frequency. It is then demonstrated theoretically and experimentally that putting the piezoelectric plate in series with a resistor presenting a nonlinear I − V characteristics having a negative slope, autonomous oscillations of the Van der Pol type can be observed. A theoretical development has led to the appearance of self-sustained periodic and mixed modes mechanical oscillations of the plate deflection.

Optimization Design of Self-Triggered Complex Detector for Space Range-Gated Imaging System

To further enhance transient characteristics of space range-gated imaging system and widen its application potential in astronomical and military domains, a self-triggered structure and complex detecting mechanism are proposed in this paper. There being delays restriction among multiple subsystem of range-gated imaging system and the robust performance of multiple optical axis adjusted are firstly discussed and analyzed. Based on these, by researching the work principle and coupling process of microchannel plates in series in image intensifier, taking advantages of the coupling loss electrons to realize self-triggered is studied and its prototype device structure is further proposed too. Then, the space optical transfer theory of new self-triggered component is deduced and its waveguide process is simulated in the software. Finally, the self-trigger performance and optical transfer effect of cutting edge invention is verified by vacuum test. And the test results basically match with theoretical model and simulation data.

Flow–pressure drop characteristics of perforated plates

PurposeThe purpose of this study is to quantify the relationship between the fluid flow and pressure drop for perforated plates. The homogenization of non-uniform fluid flows is often accomplished by passing the fluid through perforated plates. The underlying principle for the accomplishment of flow homogenization is a tradeoff of pressure drop for flow uniformity.Design/methodology/approachThe investigation, implemented by numerical simulation, is based on turbulent flow in pipes and across perforated plates. The approach is as follows: (a) to devise a model to determine pressure drop’s fluid flow information from a single-aperture, (b) to obtain this information for apertures of different shapes, (c) to determine this type of information for perforated plates situated in a circular pipe, (d) to compare the entire perforated-plate pressure drop with that for a single-aperture modular and (e) to analyze two identical perforated plates in series.FindingsThe pressure drop results for the single-aperture modular model agreed very well with those for a whole perforated plate in a round pipe, therefore negating the need to simulate the more complex situation. In addition to the parametric study with aperture shape and Reynolds number, porosities (20-60 per cent) and plate thicknesses were also varied. The results obtained here compared favorably with experimental data.Originality/valueThis work demonstrates an efficient method for analyzing and obtaining useful pressure drop information for perforated plates. For the first time, the porous media approach for modeling perforated plates is compared directly to complete, full-scale perforated plate applications and identical plates in series.

Lensing in the Ultrasonic Domain using Negative Refraction Induced by Material Contrast

The focusing of ultrasound using topographic lenses, typically made of plates with step changes that cause an interaction between forward- and backward-propagating guided waves, has been widely studied in recent years. However, such ‘step-change’ lenses require precise machining and moreover, the thick-thin structure can be unstable during deployment in practical inspection applications. The work reported here follows from the insight that perhaps any approach to induce a mismatch in acoustical impedance as achieved by the step-change can also lead to focusing of ultrasonic guided waves. By carefully choosing the impedance pairing, a novel material contrast lens stacking Aluminium and Molybdenum plates in series is shown to achieve focusing of ultrasound through negative refraction. The interface between the two metals causes the interaction of the forward-propagating second symmetric Lamb mode S2 into the backward- propagating first symmetric S2b. The focusing of Lamb waves is demonstrated using numerical simulations validated by experiments. Comparison with a simple Aluminium-Aluminium plate combination brings out the underlying physics of focusing using the proposed material contrast lens. Simulation results showing super-resolution imaging using the proposed material contrast lens are also presented, demonstrating the power of the proposed approach. This report opens up the possibilities of developing new lensing devices for use in medical imaging and nondestructive evaluation, among other possible applications.

Optimal Flow Control and Single Split Architecture Exploration for Fluid-Based Thermal Management

High-performance cooling is often necessary for thermal management of high power density systems. However, human intuition and experience may not be adequate to identify optimal thermal management designs as systems increase in size and complexity. This article presents an architecture exploration framework for a class of single-phase cooling systems. This class is specified as architectures with multiple cold plates in series or parallel and a single fluid split and junction. Candidate architectures are represented using labeled rooted tree graphs. Dynamic models are automatically generated from these trees using a graph-based thermal modeling framework. Optimal performance is determined by solving an appropriate fluid flow distribution problem, handling temperature constraints in the presence of exogenous heat loads. Rigorous case studies are performed in simulation, with components subject to heterogeneous heat loads and temperature constraints. Results include optimization of thermal endurance for an enumerated set of 4051 architectures. The framework is also applied to identify cooling system architectures capable of steady-state operation under a given loading.

Proof-of-Concept Static Thermomagnetic Generator Experimental Device

A thermomagnetic power conversion device is constructed using water flows with very low caloric energy. The device has two active regenerators built from (Mn,Fe)2(P,As) materials suspended in a magnetic circuit as proposed by Brillouin and Iskenderian. The final magnetic circuit design was further optimized with finite-element simulations. The permanent magnet acting as field source was 1.4 kg of NdFeB alloy. The active part of the generator consists of 48 disks of (Mn,Fe)2(P,As) material with four different Curie temperatures of 300 K, 304 K, 307 K, and 310 K (27 °C, 31 °C, 34 °C, and 37 °C) measured in 1 T. Into each plate, microchannels are laser cut. By stacking these plates in series, two regenerators with a gradient temperature span are built. Both generators have an exact weight of 26.9 g. The material was cycled at different speeds to find the maximum power output at the optimum frequency. Critical to a better design is a more tapered design and different materials. The tapered design ensures a greater external field and a larger external field change across the material. The materials for devices that use water as heat-transfer fluid in combination with this type of regenerator design should have a lower latent heat while maintaining their magnetic properties. This will increase the cycling speed and improve the power output of this type of device.

Double phase-retarder set-up at beamline P09 at PETRA III

Beamline P09 at PETRA III, DESY, is designed for general diffraction and resonant X-ray scattering experiments at low temperatures and high magnetic fields. The dependence of the X-ray cross-sections (Thomson, non-resonant magnetic, resonant exchange scattering, ATS) on the polarization state of the incident X-rays is an important property that one might want to capitalize on in a diffraction experiment. To that purpose, P09 is equipped with a double phase-retarder and diamond phase-plates making for the production of linearly and circularly polarized X-rays in the energy range between 3.5 and 8.5 keV as yet. Here we describe the double phase-retarder setup at P09, its principles of operation and its performances with respect to the generation of linearly polarized incident X-rays rotated by a variable angle η around the X-ray beam using two quarter-wave plates in series or a single half-wave plate.

Researching on Wide-Band Property of 1-3-2 Piezoelectric Composite

1-3-2 piezoelectric composite has been studied to fulfill the demand of wide-band transducer. The 1-3-2 piezoelectric composite is made of 1-3 piezoelectric composite and a ceramic plate in series. The mechanical quality factor of 1-3-2 composite have been deduced. The difference on wide-band property between the 1-3 and 1-3-2 piezoelectric composite is identified. In addition, some 1-3-2 composite samples are fabricated by dice-fill technology. The bandwidth of samples are investigated. The results show that the experiment agrees well with the calculation.

Concurrent measurement of linear and circular birefringence using rotating-wave-plate Stokes polarimeter

A novel technique is presented for obtaining concurrent measurements of the linear and circular birefringence properties of an optical sample by using a rotating-wave-plate Stokes polarimeter to extract the 2x2 central elements of the corresponding Mueller matrix via two linearly polarized probe lights. For a compound sample comprising a half-wave plate in series with a quarter-wave plate, the measured values of the principal angle and retardance of the quarter-wave plate are found to have average normalized errors of 0.56% and 1.16%, respectively, while the measured value of the rotation angle of the half-wave plate has an error of just 0.39%. When analyzing glucose solutions with concentrations ranging from 0-1.2 g/dl positioned in front of a half-wave plate, the average normalized errors in the principal axis angle and retardance measurements of the half-wave plate are 0.69% and 2.65%, respectively, while the error in the rotation angle measurements of the glucose solutions is 2.13%. The correlation coefficient between the measured rotation angle and the concentration of the glucose solution is determined to be 0.99985, while the standard deviation is just 0.0022 deg. Overall the experimental results demonstrate the ability of the proposed system to obtain highly accurate measurements of the linear and circular birefringence properties of an optical sample and to decouple the relationship between the principal axis angle and the rotation angle.

Two-dimensional optical beam deflector operated by wavelength tuning

A new method based on an optical delay line structure is proposed for two-dimensional raster optical beam steering. For one-dimensional beam steering, the laser beam to be deflected is split into N co-directional sub-beams of equal intensity with the aid of a plane-parallel plate. These sub-beams experience a relative time delay, which translates into a phase difference, thus forming a phased array. When the laser wavelength is tuned, the relative phase varies and the far-field interference footprint can be steered across a receive plane. By employing two plane-parallel plates in series, the described scheme can be extended to produce a two-dimensional N x N array of sub-beams, allowing two-dimensional beam steering via wavelength tuning. In this case, wavelength tuning over a larger range leads to a linear deflection which repeats itself in a raster-like fashion. One direction of deflection repeats itself multiple times as wavelength is scanned over larger range, that is, a raster effect. In this paper, the principle is theoretically derived and formulated, and the preliminary experimental results with four sub-beams are presented.

Tensegrity Architecture of an Agglutinated Foraminiferan Shell

Shells of agglutinated foraminiferan protists are composed of mineral grains bound by secreted adhesives. As such, they are useful models for examining the evolution of “primitive” exoskeletons. Previous studies revealed the ultrastructure of shells in the giant Antarctic foraminiferanAstrammina raraand demonstrated that shucked specimens would reconstruct shells using glass beads. Here we further investigate shell architecture in this model species.For micromechanical testing, an intactA. rarashell was placed between a fixed plate and a facing plate in series with a calibrated load cell. Displacement was effected by a high-precision drive, and 2-3 loading cycles were used to determine shell material properties. to assay tensile properties of the adhesive matrix, a network of pseudopodia and extracellular matrix fibers (i.e., the shell adhesive component) was obtained by incubating shucked cell bodies on 200-mesh gold grids. Pseudopodia were subsequently removed by detergent washes. Fibers in the resultant isolated matrix were severed with a Nd: YAG laser using an inverted DIC light microscope equipped with a 60× objective lens. Preliminary loading experiments using glass needles showed that Sepharose 2B beads were suitable strain gauges to assess compression within reconstructed shells (Fig. 1). in this assay, shucked cell bodies were incubated with a mixture of glass and Sepharose beads, and the reconstructed shells were examined by SEM.Repeated loading and unloading demonstrated the elastic behavior of intact shells (Fig. 2). Adhesive matrix fibers snapped towards their attachment sites within 2 sec after cutting with a laser (Fig. 3), demonstrating that they are deployed under tension. SEM images of shells reconstructed with Sepharose show compressed particle profiles (Fig. 4).

A simple analytical model for estimating air leakage through rotary valves

This paper presents an analytical model from which to estimate the air leakage through rotary valves feeding positive-pressure pneumatic conveying systems. Estimating air leakage through rotary valves is an important part of the design of certain pneumatic conveying systems. Accounting for leakage assists in estimating blower and bin vent requirements and reduces maintenance costs and downtime. An overestimate of the leakage can contribute to inefficiencies, excessive pipeline wear and particle attrition, while an underestimate can lead to blocked pipelines and severely reduced solid flowrates through the valve. The formulation of the analytical model presented in this paper is based on the principle of air flow through multiple orifice plates in series. The leakage rate across a pressure differential is determined by treating each constriction between rotor blade and casing as an orifice plate. The validity of the model is confirmed by comparing its results to previously recorded empirical data. Note that, while this paper addresses rotary valves feeding positive-pressure pneumatic conveying systems, the same principles can be used for the design of vacuum pneumatic conveying systems. For vacuum systems the air density and differential pressure must be accounted for in order to estimate the air leakage rate in the opposite direction through the valve. Accounting for this type of leakage is especially important for vacuum systems with (a) multiple feed points, in order to ensure that adequate upstream transport velocities are reached, and (b) inert gas as the transport medium, where air leakage into the system can dilute the conveying gas.

An experimental reactor to study the intrinsic kinetics of catalytic partial oxidation of methane in the presence of heat-transport limitations

The catalytic partial oxidation (CPO) of methane with oxygen was studied at atmospheric pressure in a continuous-flow reactor containing a single Pt metal gauze. Experiments were performed at catalyst temperatures and residence times in the range of 950–1200 K and 0.02–0.2 ms, respectively. Heat-transport limitations are taken into account explicitly, by measuring the catalyst temperature directly by means of a surface thermocouple. The experimental results indicated that the conversions of methane and oxygen were determined by transport phenomena; however, the CO selectivity appeared to be influenced significantly by the kinetics of the catalytic reactions. Hydrogen was found only at temperatures above 1273 K. In order to be able to derive intrinsic kinetic information from the experimental data, a reactor model consisting of two rows of parallel flat plates in series was developed, taking into account the relevant transport phenomena. This flat-plate reactor model was validated by comparing the model results to 3D fluent simulations of simultaneous heat and mass transfer in case of a simple surface reaction on the gauze catalyst. A series-parallel CPO reaction mechanism allowed simulation of the observed conversions and selectivities at different space-times. More detailed elementary-step reaction mechanisms can be developed, using both the experimental data and the flat-plate reactor model.

Simultaneous resolution of spectral and temporal properties of UV and visible fluorescence using single-photon counting with a position-sensitive detector

A new fluorescence spectrometer has been assembled at the U9B beamline of the National Synchrotron Light Source to allow simultaneous multiwavelength and time-resolved fluorescence detection, as well as spatial imaging of the sample fluorescence. The spectrometer employs monochromatized, tunable UV and visible excitation light from a synchrotron bending magnet and an imaging spectrograph equipped with a single-photon sensitive emission detector. The detector is comprised of microchannel plates in series, with a resistive anode for encoding the position of the photon-derived current. The centroid position of the photon-induced electron cascade is derived in a position analyzer from the four signals measured at the corners of the resistive anode. Spectral information is obtained by dispersing the fluorescence spectrum across one dimension of the detector photocathode. Timing information is obtained by monitoring the voltage divider circuit at the last MCP detector. The signal from the MCP is used as a ‘‘start’’ signal to perform a time-correlated single photon counting experiment. The analog signal representing the position, and hence wavelength, is digitized concomitantly with the start/stop time difference and stored in the two-dimensional histogramming memory of a multiparameter analyzer.

A double-element broad-band liquid crystal tunable filter-factors affecting contrast ratio

A double-element broad-band liquid crystal tunable filter consisting of a high-order quartz wave plate in series with a very-low-order electrooptically tunable liquid crystal phase plate and placed between crossed polarizers is described. A possible application for such a device is protection against intrusive laser radiation. The advantage of this double-element filter over a single-element low-order LC filter is that it increases the wavelength resolution of the device, which, when operated in the protect mode, allows continued sensing of the scene. Experimental and theoretical studies were made of the contrast ratios obtainable with such a filter.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Resistance and Interference of Multiple Orifice Plates in Series : Part 2-Interference of Twofold Multihole Plates

Resistance and Interference of Multiple Orifice Plates in Series : Part 2-Interference of Twofold Multihole Plates

Zone-plate Radial-shear Interferometers a Study of Possible Configurations

Two zone plates in series can be used to set up a simple radial-shear interferometer. The possible configurations for such an interferometer are analysed and their relative advantages are discussed. Experimental results with one configuration, which appears near optimum, are presented.

Resistance and Interference of Multiple Orifice Plates in Series

Resistance and Interference of Multiple Orifice Plates in Series