Stationary Fiber Research Articles

The SDSS-V Local Volume Mapper (LVM): Scientific Motivation and Project Overview

We present the Sloan Digital Sky Survey V Local Volume Mapper (LVM). The LVM is an integral-field spectroscopic survey of the Milky Way, Magellanic Clouds, and a sample of local volume galaxies, connecting resolved parsec-scale individual sources of feedback to kiloparsec-scale ionized interstellar medium (ISM) properties. The 4 yr survey covers the southern Milky Way disk at spatial resolutions of 0.05–1 pc, the Magellanic Clouds at 10 pc resolution, and nearby large galaxies at larger scales totaling >4300 deg2 of sky and more than 55M spectra. It utilizes a new facility of alt–alt mounted siderostats feeding 16 cm refractive telescopes, lenslet-coupled fiber optics, and spectrographs covering 3600–9800 Å at R ∼ 4000. The ultra-wide-field integral-field unit has a diameter of 0.°5 with 1801 hexagonally packed fibers of 35.″3 apertures. The siderostats allow for a completely stationary fiber system, avoiding instability of the line-spread function seen in traditional fiber feeds. Scientifically, LVM resolves the regions where energy, momentum, and chemical elements are injected into the ISM at the scale of gas clouds, while simultaneously charting where energy is being dissipated (via cooling, shocks, turbulence, bulk flows, etc.) to global scales. This combined local and global view enables us to constrain physical processes regulating how stellar feedback operates and couples to galactic kinematics and disk-scale structures, such as the bar and spiral arms, as well as gas in- and outflows.

Определение теплофизических характеристик тропических фруктов для их использования при производстве сухих молочных продуктов

Introduction. Canning requires thermophysical calculations for thermal or cold processing. These calculations are based on thermophysical characteristics of raw materials. The research objective was to analyze the thermophysical characteristics of tropical fruits.
 Study objects and methods. The study featured kiwi, papaya, avocado, and figs. Their thermal conductivity was analyzed with the help of stationary fiber plate method. The cryoscopic temperature was determined from the flat area of the thermogram obtained during freezing. The heat capacity and the amount of frozen moisture were determined by calculation based on the available data on the chemical composition of the fruits. The density was defined by using the hydrostatic weighing method, the sugar content – by the refractometric method, the moisture content – by drying to constant mass.
 Results and discussion. The research revealed the physicochemical parameters of kiwi, avocado, papaya, and figs. Papaya demonstrated the highest moisture content – 86.32 ± 0.02%, while kiwi appeared to have the highest density – 1,065 ± 1 kg/m3. Figs had the highest sugar content – 16.0 ± 0.1%. The thermal conductivity coefficient of fresh and frozen tropical fruits was determined experimentally and increased after freezing. Frozen avocado showed only a slight increase in thermal conductivity coefficient because of its low moisture content while frozen figs demonstrated a significant increase in the thermal conductivity coefficient – by 3.3 times. This product possessed the highest thermal conductivity: 0.63 ± 0.02 W/(m·K) for the fresh samples and 2.06 ± 0.02 W/(m·K) for the frozen samples. The thermal conductivity coefficient of kiwi and papaya increased by 2 and 4.2 times, respectively. The experiment also examined the effect of protective plastic wrap and ripeness on the thermal conductivity coefficient. The film proved to have a negative effect on the reliability of thermophysical analysis. The cryoscopic temperature was determined empirically. Such thermophysical properties as heat capacity, thermal diffusivity, and frozen moisture were based on the available chemical composition.
 Conclusion. The research revealed the physicochemical parameters of kiwi, avocado, papaya, and figs. It included a set of experiments on the thermal conductivity coefficient of fresh and frozen tropical fruits. The obtained values can be used to develop the optimal parameters of thermal processing, refrigeration, and thermal treatment of new products. They can also be useful for fortifying dairy and bakery products with exotic fruits.

Numerical investigation of dilute aerosol particle transport and deposition in oscillating multi-cylinder obstructions

The transport and deposition of aerosol particles through a fibrous filter is encountered in many natural and industrial processes. As the filtration performance for a stationary filter has been extensively studied in the literature, the present work focuses on the effect of fiber oscillation in a filter where the fibers are allowed to vibrate periodically. The transport and deposition of dilute aerosol particles in such a system is simulated using an efficient numerical model, where an iterative immersed-boundary lattice Boltzmann method is applied to solve the background flow with finite-size moving fibers, and the motion of aerosol particles is then tracked by a one-way coupling Lagrangian approach. In the present scheme, the no-slip boundary condition at the fiber surface can be exactly enforced with an iterative approach and the numerical stability is improved by adopting the MRT collision model. After the model validation in the two special cases of flow over an oscillating fiber in a quiescent fluid and particle capture by a stationary fiber, the filtration performance of an oscillating multi-fiber filter is investigated to study the effects of fiber number, arrangement and vibration mode. It is found that the oscillating motion of fiber has significant influence on the filtration performance. For a single fiber, with larger oscillation amplitude, the distribution ranges of the release position and impact angle of captured particles both increase. On the other hand, a larger fiber oscillation frequency tends to reduce the width of release position but increase the width of impact angle of deposited particles. Furthermore, the collection efficiency is found to be linearly related to the oscillation amplitude or frequency. For multiple fibers, the collection efficiency always increases with larger fiber number, but it is a non-monotonic function of the arrangement parameters, i.e., the longitudinal and transverse spacings, and the vibration parameters such as the amplitude, frequency and vibration mode. It is interesting to find that the in-phase mode can usually lead to excellent collection efficiency.

Large area laser scanning optical resolution photoacoustic microscopy using a fibre optic sensor.

A laser scanning optical resolution photoacoustic microscopy (LS OR-PAM) system based on a stationary fibre optic sensor is described. The sensor comprises an optically resonant interferometric polymer cavity formed on the tip of a rounded single mode optical fibre. It provides low noise equivalent pressure (NEP = 68.7 Pa over a 20 MHz measurement bandwidth), a broad bandwidth that extends to 80 MHz and a near omnidirectional response. The latter is a significant advantage, as it allows large areas (>1cm2) to be imaged without the need for translational mechanical scanning offering the potential for fast image acquisition. The system provides a lateral resolution of 8 µm, an axial resolution of 21 µm, and a field of view up to 10 mm × 10 mm. To demonstrate the system, in vivo 3D structural images of the microvasculature of a mouse ear were obtained, showing single capillaries overlaying larger vessels as well as functional images revealing blood oxygen saturation.

In-process workpiece based temperature measurement in cylindrical grinding

In conventional grinding processes a huge partition of the machining energy is received by the workpiece. Damage due to high thermal load might happen on the surface as well as in sublayers of the workpiece where favourable process parameters and optimized coolant supply are stringent to avoid them. To detect thermal damage known as grinding burn various established techniques like barkhausen noise measurement for ferromagnetic materials or the NITAL-etching test are available for measurement after the workpiece is machined. In this work the development and influencing factors of grinding burn are studied by a continuously in-process and workpiece based measurement of the temperatures in cylindrical grinding. A two-color pyrometer is used with a rotary joint between the rotating and stationary fibre from the workpiece to the sensor element. The radial and circumferential temperature profiles below the workpiece surface are measured to determine the thermal limits and temperature gradients. Due to the high temporal resolution the temperature gradient for single workpiece revolutions can be shown and evaluated. The heating and cooling rates are calculated and compared for different depths in the workpiece, where the heating rates are up to 50 times higher than the cooling rates depending on the distance to the surface. The knowledge can help to model grind hardening processes which rely on finite element simulations of the temperature distribution in the workpiece.

Analysis and Estimation of Errors in Measuring the Tension of Aluminum Oxide Fibers on an Experimental Stand

This article examines aspects of analyzing and estimating the systematic error in measuring the tension of alumina fibers on a tension tester with stationary fiber guides. The measurements are made during the rewinding and twisting of the fibers on an experimental stand. Calculations are performed to determine the components of the systematic error for the given testers. Among these components are the constant error and the periodic error, which in turn depend on the conditions of motion of the fibers in the tester’s guides, the fibers’ geometric characteristics, and the changes in the friction coefficient in relation to fiber velocity.

Two-dimensional simulations of resin flow in dual-scale fibrous porous medium under constant pressure

In liquid composite molding (LCM), the resin is filled into the stationary fiber to impregnate all the empty space. Because the use of fiber features the double-scale porous property, partially saturated region phenomenon will occur during the process of resin flow. Therefore, a non-zero sink-function appears on the right side of the equation of mass conservation in fluid dynamics. In this paper, the control volume/finite element method is applied to simulate the flowing characteristics of resin in two-dimensional mold under constant pressure. A corresponding algorithm is designed, and a two-dimensional program for finite element algorithm based on both dual-scale and single-scale is compiled. Compared with the flowing characteristics of resin in single-scale fibrous porous medium under the same conditions, it can be concluded that there is an unsaturated flow front in the resin flowing of the dual-scale fibrous porous medium according to the unsaturated region. The pressure distribution and filling time make huge difference when they reach the same flow front. Changing the initial pressure of resin in dual-scale fibrous porous medium will greatly affect the distribution of pressure and fill time.

Asymptotic Properties of the Approximate Inverse Estimator for Directional Distributions

For stationary fiber processes, the estimation of the directional distribution is an important task. We consider a stereological approach, assuming that the intersection points of the process with a finite number of test hyperplanes can be observed in a bounded window. The intensity of these intersection processes is proportional to the cosine transform of the directional distribution. We use the approximate inverse method to invert the cosine transform and analyze asymptotic properties of the estimator in growing windows for Poisson line processes. We show almost-sure convergence of the estimator and derive Berry–Esseen bounds, including formulae for the variance.

Asymptotic Properties of the Approximate Inverse Estimator for Directional Distributions

For stationary fiber processes, the estimation of the directional distribution is an important task. We consider a stereological approach, assuming that the intersection points of the process with a finite number of test hyperplanes can be observed in a bounded window. The intensity of these intersection processes is proportional to the cosine transform of the directional distribution. We use the approximate inverse method to invert the cosine transform and analyze asymptotic properties of the estimator in growing windows for Poisson line processes. We show almost-sure convergence of the estimator and derive Berry–Esseen bounds, including formulae for the variance.

INTENSITY ESTIMATION OF STATIONARY FIBRE PROCESSES FROM DIGITAL IMAGES WITH A LEARNED DETECTOR

Stationary fibre processes are processes of curves in a higher dimensional space, whose distribution is translation invariant. In practical applications, they can be used to model several real objects, such as roots, vascular networks and fibres of materials. Often it is required to compare processes showing similar shape, thus a quantitative approach to describe their stochastic geometry is necessary. One of the basic geometric characteristics of these processes is the intensity (i.e., mean total length per unit area or volume). Here, a general computational-statistical approach is proposed for the estimation of this quantity from digital images of the process, thus only planar fibre processes or projections of processes onto a plane are considered. Differently from approaches based on segmentation, it does not depend on the particular application. The statistical estimator of the intensity is proportional to the number of intersections between the process under study and an independent motion invariant test fibre process. The intersections are detected on the real digital image by a learned detector, easily trained by the user. Under rather mild regularity conditions on the fibre process under study, the method also allows to estimate approximate confidence intervals for the intensity, which is useful especially for comparison purposes.

Generation of longitudinal modes in an active Fabry-Perot fiber interferometer pumped by a low-power single-frequency semiconductor laser

The results of experiments on taking beat spectra at the exit of a stationary (modulator-free) fiber Mach-Zender interferometer are presented. The interferometer is excited by a single-frequency semicon-ductor laser with an output power varying from 0.65 to 2.00 mV and a line-width of less than 20 kHz. The observed line beat spectrum is explained based on the fact that the extended (several kilometers long) arm of the interferometer serves as an active fiber Fabry-Perot interferometer. In this case, the effects of enhancement of stimulated Mandel’shtam-Brillouin scattering in the fiber and the Fresnel reflection of light from the end faces of the fiber play a decisive role. Remarkably, these effects are observed at a low (less than 0.3 mW) power deposited into the fiber. The features of beat signals are considered, and the feasibility of applying this effect in high-sensitive field and displacement optical sensors is indicated.

On the generation of lift forces in random soft porous media

In this paper, we examine the generation of pressure and lift forces in a random soft fibrous media layer that is confined between two planar surfaces, an infinite horizontal lower boundary and a horizontal inclined upper boundary, in the lubrication limit where the characteristic thickness of the fibre layerH≪Lthe length of the inclined surface. The model for the fibre layer is a Brinkman equation and the Darcy permeabilityKpis described by the widely used Carman–Kozeny equation for random porous media. Two cases are considered: (a) an inclined upper boundary which slides freely on top of a stationary fibre layer which is firmly attached to the lower boundary and (b) an inclined stationary upper boundary with an attached fibre layer in which the horizontal lower boundary slides freely in its own plane beneath it. Superficially, the problems appear equivalent to the classical problem for a slider bearing where the solutions for the pressure distribution and lift force are independent of which boundary is moving. In this problem there is an optimum compression ratiok=h1/h2= 2.2, whereh1andh2are the heights at the leading and trailing edges, for maximum lift force. However, this symmetry is lost if the intervening space is filled with a soft porous fibrous material since the Brinkman equation is not invariant under a transformation of coordinates in which the inherently unsteady problem in case (a) is transformed to a steady reference frame in which the inclined upper boundary is stationary and the horizontal boundary with the adhered fibre layer moves below it. Although in the steady reference frame case (a) now appears to resemble case (b), the solutions are strikingly different and depend critically on the value of the dimensionless fibre interaction layer thickness$\alpha\,{=}\, H/\sqrt{K_p}$. For α ≪ 1 the solutions for both cases approach the classical solution for a slider bearing. For α ≫ 1 we show, using asymptotic analysis that the solutions diverge dramatically. In case (a) the pressure and lift force increase as α2and asymptotically approach a limiting behaviour for large values of α, first predicted in Feng and Weinbaum (J. Fluid Mech., vol. 422, 2000, p. 288), while in case (b) the pressure and lift force decay as α−2since the inclined upper boundary is screened by the fibre layer and the amount of fluid dragged through the fluid gap decreases as α increases and vanishes for α ≫ 1. The solution in case (a), where the inclined upper boundary moves, is of particular interest since it reveals the potential to generate enormous lift forces using commercially available inexpensive soft porous materials provided the lateral leakage at the edge of the planform can be eliminated through the use of a channel with impermeable sidewalls as first proposed in the work by Wu, Andreopolous and Weinbaum (Phys. Rev. Lett., vol. 93, 2004, p. 194501). The behaviour is illustrated for both a toboggan sliding in such a channel and a larger planform that might be useful in commercial transportation.

A closed form solution for flow in dual scale fibrous porous media under constant injection pressure conditions

In liquid composite molding (LCM), the resin is infused into stationary fiber reinforcements to impregnate all the empty spaces between the fibers. Most fabric reinforcements used in such processes consist of fiber tows or bundles that are woven, stitched, or braided to create a mat. The fiber tows and the spaces between the fiber tows saturate with resin at different rates and hence the use of a single permeability parameter to describe the flow using Darcy’s law is insufficient. An analytic solution for resin flow through such dual scale porous media is presented. It introduces the use of two distinctly different permeability values that describe the resin flow in these types of fabrics. The first permeability parameter is the bulk permeability ( K), which characterizes the overall resistance to flow. The second is the tow permeability ( K t ), which represents the resistance to flow inside each individual fiber tow. A closed form solution is developed to characterize the bulk and the tow permeability for a one-dimensional constant injection pressure experiment in which the flow front position during the filling is recorded. It is also mathematically proven that the partially saturated region remains constant if the mold is sufficiently long. The analytical methodology is validated by using a numerical simulation technique that allows one to predict the motion of the fully and partially saturated flow fronts by assigning bulk and tow permeabilities.

On Some Characteristics of Anisotropic Fibre Processes

This paper derives properties of various estimators of length intensity of stationary random fibre processes in Rd. The projections of the process onto R1 and intersections with a system of parallel (d - 1)-dimensional hyperplanes are studied. The estimation variances are expressed by means of pair correlation functions of appropriate random measures. The results are formulated for the anisotropic models in arbitrary dimension. Explicit formulas are obtained for the anistropic Boolean segment process.

Convergence of algorithms for reconstructing convex bodies and directional measures

We investigate algorithms for reconstructing a convex body $K$ in $\mathbb {R}^n$ from noisy measurements of its support function or its brightness function in $k$ directions $u_1,...,u_k$. The key idea of these algorithms is to construct a convex polytope $P_k$ whose support function (or brightness function) best approximates the given measurements in the directions $u_1,...,u_k$ (in the least squares sense). The measurement errors are assumed to be stochastically independent and Gaussian. It is shown that this procedure is (strongly) consistent, meaning that, almost surely, $P_k$ tends to $K$ in the Hausdorff metric as $k\to\infty$. Here some mild assumptions on the sequence $(u_i)$ of directions are needed. Using results from the theory of empirical processes, estimates of rates of convergence are derived, which are first obtained in the $L_2$ metric and then transferred to the Hausdorff metric. Along the way, a new estimate is obtained for the metric entropy of the class of origin-symmetric zonoids contained in the unit ball. Similar results are obtained for the convergence of an algorithm that reconstructs an approximating measure to the directional measure of a stationary fiber process from noisy measurements of its rose of intersections in $k$ directions $u_1,...,u_k$. Here the Dudley and Prohorov metrics are used. The methods are linked to those employed for the support and brightness function algorithms via the fact that the rose of intersections is the support function of a projection body.

Algorithms to estimate the rose of directions of a spatial fibre system

Summary The directional measure (which is up to normalization the rose of directions) is used to quantify anisotropy of stationary fibre processes in three-dimensional space. There exist a large number of approaches to estimate this measure from the rose of intersections (which is the mean number of intersections of fibres with lower dimensional test sets). Three recently suggested nonparametric algorithms to solve this problem are reviewed and compared. They were obtained from solutions of a least squares problem, a more general convex optimization problem and a linear program, respectively. Application to two different carbon fibre architectures and to simulated data allow an empirical comparison of these approaches. In addition, estimators for the associated zonoid (or Steiner compact) are suggested. This set turns out to be an intuitive tool for visualization.

Simulation of LCM processes involving induced or forced deformations

Resin Transfer Molding (RTM) is part of Liquid Composites Molding technologies in which composites are manufactured by the impregnation of a stationary fiber preform by a low viscosity resin system. Competitive simulation tools for RTM modeling are widely spread in the composites world. However, other LCM processes need also to be modeled, especially those that imply deformation of the fiber bed. By using LIMS, a code initially developed to model the RTM process, has been introduced a routine that can manage forced deformations due to external stress, such as in the injection/compression process, as well as induced deformations of a non-rigid insert such as in sandwich manufacturing techniques, where the pressure of the flowing resin can locally compress the foam core. The routine implemented compares the liquid pressure profile with the mechanical properties of the solid entities and sets the deformations induced by changing geometrical features. The preform characteristics (fiber volume content and permeability) are then updated. The mass conservation principle is respected by keeping the injected amount of resin constant through an artificial injection stage. Computed pressure and deformation are compared to experimental data from injection of a sandwich structure where foam core deformation occurs and from injection of a hollowed part molded with an inflatable bladder, and with an analytical solution in the case of the injection/compression process of a cylindrical part.

Evaluation of Local Gas Exchange in a Pulsating Respiratory Support Catheter

An intravenous respiratory support catheter, the next generation of artificial lungs, is being developed in our laboratory to potentially support acute respiratory failure or patients with chronic obstructive pulmonary disease with acute exacerbations. A rapidly pulsating 25 ml balloon inside a bundle of hollow fiber membranes facilitates supplemental oxygenation and CO2 removal. In this study, we hypothesized that non-uniform gas exchange in different regions of this fiber bundle was present because of asymmetric balloon collapse and the interaction of longitudinal flow. Four quarter regions and two rings around the central balloon were selectively perfused to evaluate local gas exchange in a 3.18 cm test section using helium as the sweep gas. Quarter region CO2 exchange rates at 400 beats per minute were 156.8 +/- 0.8, 162.5 +/- 1.8, 157.2 +/- 0.2, and 196.6 +/- 0.8 ml/min/m2 (top, front, bottom, and back, respectively). The back section, adjacent to convex balloon collapse, had 17-20% higher exchange than the other sections caused by higher relative velocities past its stationary fibers. Inner and outer ring maximum pulsation gas exchange rates were 174.4 +/- 1.8 and 174.6 +/- 0.9 ml/min/m2, respectively, showing that fluid flow was equally distributed throughout the fiber bundle.

Network formation during cocure of phenolic resins with vinyl‐ester and epoxy‐amine systems for use in multifunctional composites

AbstractTraditionally, multilayered composites have been manufactured in multiple steps that involve the fabrication of each layer separately and the bonding them together by using adhesives or secondary bonding. More recently, manufacturing techniques have been developed that enable the manufacture of multilayered hybrid composite parts in a single step. In one such technique known as coinjection resin transfer molding (CIRTM), two or more resins are simultaneously injected into a mold filled with a stationary fiber bed. This method not only cuts down manufacturing costs and time, but also offers the potential of cocure of the adjacent thermosetting resins inside the mold, which could aid in the formation of a tougher interphase between the layers and improve long‐term durability. The advantages offered by coinjection are, however, dependent on the successful cocure of the resins involved, and hence, there exists a need to determine compatible resin systems for coinjection. By compatible, it is meant that the resins must cure when in contact with each other, have compatible cure cycles (i.e., cure temperature, cure time, etc.), and result in acceptable physical and mechanical properties. The most commonly used matrix resins are vinyl‐ester resins. The cure of vinyl‐ester resin was found to be severely limited by contact with phenolic resin. This necessitates an impermeable separation layer between phenolic and vinyl‐ester resins in CIRTM manufacture. A possible candidate for this separation layer was epoxy‐amine‐based prepregs or adhesive layers. Thus, the cocure of mixtures of phenolic with epoxy‐amine was studied, and it was found that phenolic resin significantly affects the cure of epoxy‐amines. A model to quantify the effect of phenolic resin on the cure of epoxy‐amines has been proposed. By using this model, the fraction of primary amine consumed by the phenolic can be estimated. It was found that increasing the initial amine concentration in the cocure reaction mixture leads to an increase in the epoxy conversion as well as the Tg of the material. Therefore, it is recommended that, in cocure of epoxy‐amine and phenolic resins, the initial concentration of amine must be greater than the stoichiometric amount to compensate for the loss of amine to the phenolic resin. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3107–3119, 2004

Heat transfer of fibre beds in resin transfer moulding: an experimental approach

Resin transfer moulding is a fibre impregnation process which is widely used for manufacturing of lightweight fibre reinforced plastic components for automotive and aircraft industry. For economic manufacturing of larger series of production lower cycle times must be achieved, thus injection strategies which allow a rapid infusion of the resin and impregnation of the fibres must be applied. For process optimisation numerical methods are increasingly applied to reduce time to market, cost and risk. Since temperature has an impact on flow and curing of the injected resin, heat transfer mechanisms between the tool and the uncured composite part is of major importance to achieve reliable numerical results. When fluid flows through stationary fibre beds, hydrodynamic dispersion plays an important role in heat transfer and is found to be a function of Peclet number. To understand the hydrodynamic dispersion phenomena, a test rig was designed to measure heat transfer at steady state conditions. The transverse effective diffusivity was investigated, whereas the influence of cavity thickness, porosity and resin flow velocity on effective thermal diffusivity was evaluated. Based on experimental data a model for heat transfer was developed. Because resin flows through a porous media, thermal diffusion is expected to be a combination of conduction and convection. Therefore the model for transverse diffusion for non-crimped fabrics was found to be a function of the thermal properties of the constituent materials, the fibre volume fraction, the degree of filling and the Peclet number. The model is suitable for all process stages, such as preheating, form filling and curing.