Showing papers on "Analytical technique published in 1988"
TL;DR: In this article, two different techniques for the calculation of optical modes of Ti: LiNbO/sub 3/ channel waveguides and finite element method are presented, and the effective indices and field distributions obtained by both techniques are compared for wavelengths of 0.6 and 1.2 mu m, for both quasi-TE and -TM polarization, considering Y-cut and Z-cut crystal orientation and both isotropic and anisotropic Ti/sup 4+/ diffusion.
Abstract: Two different techniques for the calculation of optical modes of Ti:LiNbO/sub 3/ channel waveguides are presented. The first one is an almost analytical technique based on the effective-refractive-index method. The second one is based on the well-known finite-element method. Both approaches use a rather realistic waveguide model considering crystal anisotropy, wavelength dispersion of the refractive index distributions, and also the nonlinear dependence of the ordinary refractive index on the Ti/sup 4+/ concentration. Effective indices and field distributions obtained by both techniques are compared for wavelengths of 0.6 and 1.2 mu m, for both quasi-TE and -TM polarization, considering Y-cut and Z-cut crystal orientation and both isotropic and anisotropic Ti/sup 4+/ diffusion. >
171 citations
TL;DR: Laser-Induced Thermal Emission (LITE) spectroscopy is introduced as an analytical technique for condensed-phase specimens as mentioned in this paper, where a laser beam is used to locally heat the specimen, and the mid-infrared thermal emission is observed.
Abstract: Laser-Induced Thermal Emission (LITE) spectroscopy is introduced as an analytical technique for condensed-phase specimens. In this technique, a laser beam is used to locally heat the specimen, and the mid-infrared thermal emission is observed. Two different materials and different thicknesses of each material were examined with LITE. The equilibrium temperature attained during a LITE measurement was estimated to be about 50°C. The advantages of LITE over conventional thermal emission are noted. The multiple dimensions of information present and some of the potential analytical applications of LITE are discussed.
39 citations
TL;DR: In this paper, an approximate technique to solve guidance problems in dielectric waveguides having almost arbitrary cross-section index distribution is presented, which consists of reducing the solution of the three-dimensional guide to a solution of two unidimensional slabs.
Abstract: An approximate technique to solve guidance problems in dielectric waveguides having almost arbitrary cross-section index distribution is presented. The technique consists of reducing the solution of the three-dimensional guide to the solution of two unidimensional slabs. By starting with the circular-cylinder coordinate system instead of the Cartesian one, the results are found to be more precise and far more informative than those derived from any other approximate analytical technique. The ideas presented here may be easily extended to solve more sophisticated structures such as couplers and cavities. >
22 citations
TL;DR: In this article, the applicability of dynamic headspace analyses for viscous liquids and solid samples is demonstrated, and some comments on the usefulness of this technique for quantifying volatiles in polymeric matrices are made.
Abstract: The applicability of dynamic headspace analyses for viscous liquids and solid samples is demonstrated. Some comments on the usefulness of this technique for quantifying volatiles in polymeric matrices are made.
18 citations
TL;DR: Capillary electrophoresis is expected to be the fastest-growing analytical technique since HPLC as mentioned in this paper, and it has already shown its utility in a variety of applications, such as medical applications.
Abstract: High performance capillary electrophoresis is expected to be the fastest-growing analytical technique since HPLC. The method has already shown its utility in a variety of applications.
16 citations
TL;DR: In this article, a brief review of the general requirements for handling real world thin film and interfacial analysis in the thickness region of 50 to 5000 A is offered, and an attempt has been made to demonstrate that variable exit angle X-ray fluorescence spectrometry is the only surface analytical technique which has the inherent capability to meet all such requirements.
15 citations
TL;DR: In this paper, a new method for measuring the spatial distribution of combined polarization and space charge in various ferroelectric materials has been developed, called the Laser Intensity Modulation Method (LIMM).
Abstract: A new method for measuring the spatial distribution of combined polarization and space charge in various ferroelectric materials has been developed. The technique, called the Laser Intensity Modulation Method (LIMM), is based upon measurement of the pyroelectric current generated by the material when it is heated with a laser beam which is intensity-modulated over a range of frequencies. A special analytical technique is used to transform the current—frequency measurements to spatial distributions. The method gives high resolution and is very stable with respect to measurement errors. The technique can be easily implemented in a laboratory with conventional equipment. The advantages and limitations of LIMM are illustrated by means of calculations based upon simulated data. Experimental results on polymers and ceramics are presented.
7 citations
TL;DR: In this paper, the authors describe a scheme whereby standard finite element/boundary element coupling theory may be applied to yield a method which is both simple and consistent in terms of radiative exchange.
Abstract: In order to solve problems of re-radiation and reflection in finite element thermal analysis, a discretization consisting of flat isothermal surfaces is usually assumed. Such an approximation is clearly inconsistent if an isoparametric model is used for any surrounding solid. In addition, geometric view-factors are often required explicitly, but their calculation is generally considered to be tedious and error prone. The representation of radiative exchange by a boundary integral equation is a standard analytical technique. The use of such a representation in conjunction with finite element analysis, however, appears to be quite recent. The present work describes a scheme whereby standard finite element/boundary element coupling theory may be applied to yield a method which is both simple and consistent. The use of isoparametric elements allows varying temperatures and curved surfaces to be modelled. For an empty enclosure the kernel of the integral equation is simply related to the differential geometric view-factor. Re-radiation and reflection are implicit.
4 citations
01 Jan 1988
2 citations
TL;DR: The Marine Analytical Chemistry Standards Program (MACSP) of the National Research Council of Canada has certified 8 marine reference materials for trace metal concentrations, including sediments, 3 biological tissues and 3 seawater CRMs as discussed by the authors.
Abstract: Despite significant progress in instrumental analytical techniques, concentration data on many trace heavy metals in environmental and biological materials are unreliable. Valid laboratory analyses and associated quality control procedures pertinent to the monitoring or pollutants depend upon the availability and use of appropriate (certified) reference materials (CRM). CRMs play a vital role in improving the accuracy and precision of data and aid in the establishment of reliable and consistent sets of baseline data in environment samples and monitoring programs. The demand for standards and reference materials in marine chemistry programs is accelerating. In accordance with one of the basic objectives of the Marine Analytical Chemistry Standards Program (MACSP) of the National Research Council of Canada, i.e., to provide analytical reference materials and standards in types and quantities sufficient to serve the needs of the marine science community, our laboratory has, since 1976, issued 8 marine reference materials certified for trace metal concentrations. These include 2 sediments, 3 biological tissues and 3 seawater CRMs. A symbiotic production-certification process has evolved from this program in that the need to provide certified values of trace metal contents in such complex materials has fostered development of new more sensitive, reliable and faster methods of analysis. An overview of MACSP will be given and some analytical techniques in use in our laboratory for ultratrace analysis will be described, including chelationion exchange using immobilized ligands, novel hydride generation-preconcentration methodology and rapid sample dissolution techniques using microwave heating. Emphasis will be placed on use of graphite furnace atomic absorption spectrometry as the analytical technique of choice.
2 citations
TL;DR: The problems of sample preparation and system maintenance are addressed to ensure the most sensitive, durable, and efficient results for trace analysis by GC in this industry.
Abstract: Gas chromatography (GC) is the most widely used analytical technique in the food and beverage industry. This paper addresses the problems of sample preparation and system maintenance to ensure the most sensitive, durable, and efficient results for trace analysis by GC in this industry.
02 Oct 1988
TL;DR: In this article, the concept of the merit index is introduced to quantize the way in which novel designs are measured, and a design methodology is provided to simplify the design process by utilizing analytical, rather than subjective approaches to optimize product development.
Abstract: A method of measurement is needed to define quantitatively the performance index for optimum design. Typically, designs are judged subjectively rather than by analytical techniques in which the engineer is trained. To alleviate this problem, the concept of the merit index is introduced to quantize the way in which novel designs are measured. This analytical technique is used as a method in selecting the optimal design. The merit index is a function of the design adequacy, producibility, compatibility, reliability, and cost effectiveness. The design objectives are expressed as probabilities and assigned individual weights to represent the relative importance in the performance index. A design methodology is provided to simplify the design process by utilizing analytical, rather than subjective approaches to optimize product development. The development of a variable-reluctance servo-motor controller is used as a case study to illustrate the technique. >
01 Jan 1988
TL;DR: In this paper, the authors present analytical expressions for predicting distillate and bottoms composition transient responses due to changes in manipulative and disturbance variables of a tower, which is relatively simple to use and much less time consuming compared to dynamic simulation.
Abstract: This paper presents analytical expressions for predicting distillate and bottoms composition transient responses due to changes in manipulative and disturbance variables of a tower. The authors in an earlier paper showed that towers are inherently recyle structures and linearization techniques should be applied at perturbed conditions of tower models to evaluate realistic tower time constants. In this earlier paper, a numerical approach to estimating time constants was presented. The numerical approach is extended in this paper to an analytical approach that requires only steady state and design information of a tower. The analytical approach is relatively simple to use and much less time consuming compared to dynamic simulation. Further, the analytical technique gives insight into why towers respond nonlinearly.