Design and Development of a New Edge Sensor for Web Guiding

Existing edge sensors use the concept of blocking/unblocking to determine web lateral position. The most commonly used sensors employ either ultrasonic or optical signals to detect the web edge position by measuring the amount of signal attenuation due to blocking/unblocking of the signal. The main drawback of this sensing method is nonuniform signal attenuation due to web material variations and opacity. The research in this paper develops a new sensor which utilizes the phenomena of light scattering from the web edge and the directional sensitivity of optical fibers to determine the web lateral position. A collimated light beam is incident on the web edge and scattered light is collected by a linear array of fibers spatially positioned above the web edge. Based on the intensity of light received by each fiber in the fiber array, lateral position of the web is determined. The theory of operation and the development of the sensor is described. Experiments are conducted with different web materials to validate the proposed sensing method. A representative sample of the results are presented and discussed     

Reduced-order model technique for the analysis of anisotropic inhomogeneous media: application to liquid-crystal displays

Electromagnetic wave propagation in anisotropic inhomogeneous media is computed by a novel reduced-order model technique, which is based on the restriction of the Marcuvitz-Schwinger equations on Krylov subspaces and on the application of the singular-value decomposition. The model is derived from the standard coupled-wave method and includes both wide-angle diffraction and light scattering at dielectric interfaces. The method, currently implemented for two-dimensional problems, was applied to the analysis of different liquid-crystal test cells. Numerical results are compared with those obtained through the application of the coupled-wave method and the Jones method and with experimental microscopic measurements.     

Atmospheric aerosol profiling with a bistatic imaging lidar system

Atmospheric aerosols have been profiled using a simple, imaging, bistatic lidar system. A vertical laser beam is imaged onto a charge-coupled-device camera from the ground to the zenith with a wide-angle lens (CLidar). The altitudes are derived geometrically from the position of the camera and laser with submeter resolution near the ground. The system requires no overlap correction needed in monostatic lidar systems and needs a much smaller dynamic range. Nighttime measurements of both molecular and aerosol scattering were made at Mauna Loa Observatory. The CLidar aerosol total scatter compares very well with a nephelometer measuring at 10 m above the ground. The results build on earlier work that compared purely molecular scattered light to theory, and detail instrument improvements.     

Determination of essential work of fracture in EPBC sheets obtained by different transformation processes

1 mm sheets of polypropylene and ethylene-propylene block copolymers (EPBC) have been obtained using different processing methods in order to study the influence of processing induced morphology in the fracture properties of these materials. The processing methods employed were compression moulding (CM), extrusion-calendering (EC) and injection moulding (IM). Additionally, the sheets obtained by extrusion and injection were submitted to an annealing process with the aim to obtain more homogeneous morphologies that would ease their characterization.The morphology has been characterized by different techniques: Polarizing light microscopy (MLP), differential scanning calorimetry (DSC), wide-angle X-ray diffraction scattering (WAXS) and scanning electron microscopy (SEM).The fracture properties were determined by the essential work of fracture (EWF) method for deeply double edge notched specimens (DDENT), since these materials show ductile and post-yielding fracture behaviour. The EWF technique was applied in both the melt flow (MD) and the transversal (TD) directions in the sheets obtained by extrusion and injection moulding.Results show that the sensitivity of the technique allows examining the effect of morphological variations of thin sheets, as well as a better characterization of the orientation level (versus other parameters like yielding stress or elastic modulus obtained by tensile test).     

Comparison of methods for reducing the effects of scattering in spectrophotometry

Light scattering provides a problem in optical spectroscopy as the relationship between attenuation and absorption in the presence of scattering is nonlinear. Three simple methods of reducing the effects of scattering and hence returning to an approximately linear relationship are considered in this paper, namely, extracting light that has maintained its original polarization state through subtraction of orthogonal polarization states, use of an added absorber, and spatial filtering. These can all be applied relatively easily to conventional spectrophotometers. However, there is an inevitable trade-off between the accuracy of the measurement and the signal-to-noise ratio as scattered light is rejected from the detector. It is demonstrated that polarization subtraction is the most efficient technique at selecting weakly scattered photons from a scattered light background as it enables the relationship between attenuation and absorption coefficient to become more linear while maintaining a higher number of detected photons. In practical use, the drawback of polarization subtraction over added absorber and spatial filtering methods is that a large dc background light level is maintained, which contributes to a higher shot noise. This means that when the scattering coefficient is high (micros > or = 7 mm(-1)) the added absorber method offers better performance for shot noise limited detection.     

New poly(butylene succinate)/layered silicate nanocomposites: preparation and mechanical properties

New poly(butylene succinate) (PBS)/layered silicate nanocomposites have been successfully prepared by simple melt extrusion of PBS and octadecylammonium modified montmorillonite (C18-mmt) at 150 degrees C. The d-spacing of both C18-mmt and intercalated nanocomposites was investigated by wide-angle X-ray diffraction analysis. Bright-field transmission electron microscopic study showed several stacked silicate layers with random orientation in the PBS matrix. The intercalated nanocomposites exhibited remarkable improvement of mechanical properties in both solid and melt states as compared with that of PBS matrix without clay.     

Self-consistent approach to the solution of the light transfer problem for irradiances in marine waters with arbitrary turbidity, depth, and surface illumination. I. Case of absorption and elastic scattering

A self-consistent variant of the two-flow approximation that takes into account strong anisotropy of light scattering in seawater of finite depth and arbitrary turbidity is presented. To achieve an appropriate accuracy, this approach uses experimental dependencies between downward and total mean cosines. It calculates irradiances, diffuse attenuation coefficients, and diffuse reflectances in waters with arbitrary values of scattering, backscattering, and attenuation coefficients. It also takes into account arbitrary conditions of illumination and reflection from the bottom with the Lambertian albedo. This theory can be used for the calculation of apparent optical properties in both open and coastal oceanic waters, lakes, and rivers. It can also be applied to other types of absorbing and scattering medium such as paints, photographic emulsions, and biological tissues.     

Selected-area small-angle electron diffraction

Selected-area electron diffraction capable of resolving spacings up to 2000 Å from first-order discrete reflections has been achieved using a standard, double-condenser electron microscope. The technique allows photographing of the selected area, at sufficient magnification, that gives rise to the small-angle scattering pattern, in addition to the normal capabilities of obtaining related wide-angle diffraction and wide-angle and small-angle dark-field micrographs. Most, but not all, of the results of discrete and diffuse, small-angle electron diffraction studies from a large variety of specimens including drawn, annealed polyethylene, latex particles, evaporated gold particles, grating replicas, and slit edges have been explained on the basis of the structures observed in the corresponding electron micrographs. Small-angle electron diffraction is found to be more sensitive to defects in the packing of the scattering centres than small-angle X-ray scattering.     

Attenuation of lateral propagating light in sea ice measured with an artificial lamp in winter Arctic

The attenuation property of a lateral propagating light (LPL) in sea ice was measured using an artificial lamp in the Canadian Arctic during the 2007/2008 winter. A measurement method is proposed and applied whereby a recording instrument is buried in the sea ice and an artificial lamp is moved across the instrument. The apparent attenuation coefficient μ(λ) for the lateral propagating light is obtained from the measured logarithmic relative variation rate. With the exception of blue and red lights, the attenuation coefficient changed little with wavelength, but changed considerably with depth. The vertical decrease of the attenuation coefficient was found to be correlated with salinity: the greater the salinity, the greater the attenuation coefficient. A clear linear relation of salinity and the lateral attenuation coefficient with R² = 0.939 exists to address the close correlation of the attenuation of LPL with the scattering from the brine. The observed attenuation coefficient of LPL is much larger than that of the vertical propagation light, which we speculate to be caused by scattering. Part of this scattered component is transmitted out of the sea ice from the upper and lower surfaces.     

Comparative Study of Light Scattering from Hepatoma Cells and Hepatocytes

Primary liver cancer is one of the highest mortality malignant tumors in the world. China is a high occurrence area of primary liver cancer. Diagnosis of liver cancer, especially early diagnosis, is essential for improving patients?? survival. Light scattering and measuring method is an emerging technology developed in recent decades, which has attracted a large number of biomedical researchers due to its advantages, such as fast, simple, high accuracy, good repeatability, and non-destructive. The hypothesis of this project is that there may be some different light scattering information between hepatoma cells and hepatocyte. Combined with the advantages of the dynamic light scattering method and the biological cytology, an experimental scheme to measure the light scattering information of cells was formulated. Hepatoma cells and hepatic cells were irradiated by a semiconductor laser (532?nm). And the Brookhaven BI-200SM wide-angle light scattering device and temperature control apparatus were adopted. The light scattering information of hepatoma cells and hepatic cells in vitro within the 15°C to 30°C temperature range was processed by a BI-9000AT digital autocorrelator. The following points were found: (a) the scattering intensities of human hepatic cells and hepatoma cells are nearly not affected by the temperature factor, and the former is always greater than the latter and (b) the relaxation time of hepatoma cells is longer than that of hepatic cells, and both the relaxation time are shortened with increasing temperature from 15°C to 25°C. It can be concluded that hepatoma cells could absorb more incident light than hepatic cells. The reason may be that there exists more protein and nucleic acid in cancerous cells than normal cells. Furthermore, based on the length relaxation time, a conclusion can be inferred that the Brownian movement of cancer cells is greater.     

Investigation of the effect of scattering agent and scattering albedo on modulated light propagation in water

A recent paper described experiments completed to study the effect of scattering on the propagation of modulated light in laboratory tank water [Appl. Opt.48, 2607 (2009)APOPAI0003-693510.1364/AO.48.002607]. Those measurements were limited to a specific scattering agent (Maalox antacid) with a fixed scattering albedo (0.95). The purpose of this paper is to study the effects of different scattering agents and scattering albedos on modulated light propagation in water. The results show that the scattering albedo affects the number of attenuation lengths that the modulated optical signal propagates without distortion, while the type of scattering agent affects the degree to which the modulation is distorted with increasing attenuation length.     

Airborne polarized lidar detection of scattering layers in the ocean

A polarized lidar technique based on measurements of waveforms of the two orthogonal-polarized components of the backscattered light pulse is proposed to retrieve vertical profiles of the seawater scattering coefficient. The physical rationale for the polarized technique is that depolarization of backscattered light originating from a linearly polarized laser beam is caused largely by multiple small-angle scattering from particulate matter in seawater. The magnitude of the small-angle scattering is determined by the scattering coefficient. Therefore information on the vertical distribution of the scattering coefficient can be derived potentially from measurements of the time-depth dependence of depolarization in the backscattered laser pulse. The polarized technique was verified by field measurements conducted in the Middle Atlantic Bight of the western North Atlantic Ocean that were supported by in situ measurements of the beam attenuation coefficient. The airborne polarized lidar measured the time-depth dependence of the backscattered laser pulse in two orthogonal-polarized components. Vertical profiles of the scattering coefficient retrieved from the time-depth depolarization of the backscattered laser pulse were compared with measured profiles of the beam attenuation coefficient. The comparison showed that retrieved profiles of the scattering coefficient clearly reproduce the main features of the measured profiles of the beam attenuation coefficient. Underwater scattering layers were detected at depths of 20-25 m in turbid coastal waters. The improvement in dynamic range afforded by the polarized lidar technique offers a strong potential benefit for airborne lidar bathymetric applications.     

Quantitative spectrophotometry of scattering media via frequency-domain and constant-intensity measurements

The attenuation of light by scattering and absorbing media is nonlinearly dependent upon the absorption coefficient, since detected light has experienced many different flight times. The frequency response of such a sample to modulated light is also nonlinear. We derive an expression for the attenuation that includes both the absorption coefficient and the modulation frequency. Its form is a power series whose coefficients are the cumulants of the temporal point-spread function (TPSF). Recasting this expression in terms of intensity leads to a similar expression with the cumulants replaced by the moments of the TPSF. A means of exploiting this relationship to produce estimates of the absolute concentration of the absorbing species is suggested.     

Light scattering by wood fibers

We consider the scattering of light by single wood fibers both theoretically and experimentally. We describe the size and the shape distributions and the internal structure and chemical composition of the wood fibers. We have modeled the random shape of the hollow, cylindrical wood fiber by using multivariate lognormal statistics. We have computed wood-fiber absorption and scattering cross sections, asymmetry parameters, and scattering phase matrices in the ray-optics approximation. Finally, we have provided experimental results from angular scattering measurements for wood fibers and present what we believe is the first comparison between these measurements and ray-optics computations for Gaussian random wood-fiber models. In spite of the complicated internal structure of the wood fiber, our model together with the ray-optics treatment explains the scattering measurements surprisingly well.     

Melting and crystallization of UHMWPE skived film

Commercial skived film from ultra-high molecular-weight polyethylene (UHMWPE) with considerable uniaxial orientation of lamellae is studied by ultra-small-angle X-ray scattering (USAXS) and wide-angle X-ray scattering (WAXS) during melting and crystallization in order to identify its mechanisms of crystallization. For the analysis of the nanostructure two-dimensional USAXS patterns are analyzed by means of the multidimensional chord distribution function (CDF) method. WAXS shows that crystallization is always isotropic and fast. WAXS reflections are observed before—under certain processing conditions—the SAXS pattern becomes anisotropic. Thus crystallization is decoupled from a slower process of oriented nanostructure formation (nanoforming). If nanoforming is performed isothermally at 105 °C, the evolving nanodomain layers obtain some preferential orientation, as long as the orientation of the melt has not previously been erased by melt-annealing at temperatures of 140 °C or above. Crystallization at temperatures ≥110 °C followed by quenching leads to isotropic nanostructure. Although crystallization is always observed early in the WAXS patterns, the USAXS patterns exhibit only weak discrete scattering during isothermal treatment at temperatures of 110 °C and higher. At 105 °C anisotropic isothermal nanoforming starts after 1.5 min. The melting of the original material resembles an inverted random car-parking mechanism. Only next-neighbor correlations are observed among the crystalline layers. The average nanodomain layer thickness is only slightly increasing (26–30 nm), whereas the long period increase is strong (from 60 nm to 140 nm).     

Wave dispersion and attenuation in fiber composites

 This work deals with the dispersion and attenuation of elastic plane waves propagating in a single layer fiber reinforced composite, in a direction which is perpendicular to the fibers. An iterative effective medium model, based on single scattering considerations, for the quantitative estimation of wave dispersion and attenuation is proposed. The single scattering problem is solved numerically by means of a 2-D boundary element methodology. Numerical results concerning the plane velocity and the attenuation coefficient of longitudinal or transverse SH, SV waves propagating in two types of fiber reinforced composite materials, are presented. The obtained results are compared to those taken either experimentaly or numericaly by other investigators.     

A wide-angle X-ray scattering study of the ageing of poly(hydroxybutyrate)

The ageing of poly(hydroxybutyrate) at room temperature has been studied using wide-angle X-ray scattering. The observed unit-cell parameters and crystal density did not change on ageing. A small increase in crystallinity was observed during the first 32 h storage. No change in crystallinity was detectable after this time. These results are discussed in the light of theories relating to the embrittlement of poly(hydroxybutyrate). © 1998 Chapman & Hall     

Asbestos real-time monitor in an atmospheric environment

The concentration of asbestos fiber aerosols can be monitored by measuring the polarization of laser light scattered by asbestos fibers. The principle of discriminating asbestos fibers is based on the theoretically expected difference in polarization at a scattering angle of 170 deg between cylindrical and spherical airborne particles; polarization at this scattering angle should be positive for cylindrical particles such as asbestos fibers but should be negative or close to zero for spherical mineral particles. We constructed an experimental asbestos real-time monitor that uses a strong electric field to align the airborne particles, that uses lasers having linear polarization with an equal amplitude in parallel and perpendicular components to the aligned long axis of particles, and that simultaneously detects the two components of the linear polarization of light scattered at 170 deg, i.e., close to the backscatter. Experiments that were performed to detect the light scattered from airborne standard asbestos fibers showed that the measured polarization fits theoretical prediction. The concentrations of airborne asbestos fibers obtained by the asbestos real-time monitor were consistent with those estimated by the standard phase contrast microscope method.     

Reflectance and transmittance model for recto-verso halftone prints

We propose a spectral prediction model for predicting the reflectance and transmittance of recto-verso halftone prints. A recto-verso halftone print is modeled as a diffusing substrate surrounded by two inked interfaces in contact with air (or with another medium). The interaction of light with the print comprises three components: (a) the attenuation of the incident light penetrating the print across the inked interface, (b) the internal reflectance and internal transmittance that accounts for the substrate's intrinsic reflectance and transmittance and for the multiple Fresnel internal reflections at the inked interfaces, and (c) the attenuation of light exiting the print across the inked interfaces. Both the classical Williams-Clapper and Clapper-Yule spectral prediction models are special cases of the proposed recto-verso reflectance and transmittance model. We also extend the Kubelka-Munk model to predict the reflectance and transmittance of recto-verso halftone prints. The extended Kubelka-Munk model is compatible with the proposed recto-verso reflectance and transmittance model. In the case of a homogeneous substrate, the recto-verso model's internal reflectance and transmittance can be expressed as a function Kubelka-Munk's scattering and absorption parameters, or the Kubelka-Munk's scattering and absorption parameters can be inferred from the recto-verso model's internal reflectance and transmittance, deduced from spectral measurements. The proposed model offers new perspectives both for spectral transmission and reflection predictions and for characterizing the properties of printed diffuse substrates.     

WAXD/SAXS study and 2D fitting (SAXS) of the microstructural evolution of PAN-based carbon fibers during the pre-oxidation and carbonization process北大核心CSCD

Microstructutal evolution in polyacrylonitrile (PAN) fibers at different temperatures during pre-oxidation and carbonization under stretching was studied by. synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS). Microvoids were characterized by the classical SAXS method, and were compared with simulation results obtained by fitting 2D SAXS patterns to a model based on a dilute system of cylindrical microvoids randomly distributed and preferentially orientated along the fiber axis and having a log-normal size distribution. The WAXD results showed that the crystal size, d-spacing and preferred orientation decreased during pre-oxidation, and increased during carbonization. A diffraction peak for PAN fibers at 2 theta = 13. 6 degrees disappeared during the final stage of pre-oxidation, meanwhile a new peak at 2 theta = 23.6 degrees appeared, whose intensity increased during carbonization, indicating the formation of the graphite structure. The average length of the microvoids increased, and new microvoids were formed, which became oriented along the fiber axis as the fiber manufacturing process proceeded. The length of microvoids from simulation results is consistent with that from the classical method, indicating that the model is valid to describe the microvoid structure of fibers.