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  • Analytical Chemistry and Spectroscopy  (3,996)
  • Chemical Engineering  (2,232)
  • 1990-1994  (2,087)
  • 1980-1984  (4,141)
  • 1925-1929
  • 1991  (2,087)
  • 1984  (1,450)
  • 1982  (1,364)
  • 1980  (1,327)
Collection
Keywords
Publisher
Years
  • 1990-1994  (2,087)
  • 1980-1984  (4,141)
  • 1925-1929
Year
  • 1
    Electronic Resource
    Electronic Resource
    Crystallization kinetics of poly(ethylene terephthalate). Part I: Kinetic equation with variable growth rate (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 110-115 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new crystallization kinetic equation has been derived considering the decrease in growth rate. The average linear growth rate of spherulite was assumed to be proportional to the m-th order of the uncrystallized fraction of the crystallizing material. A modified Avrami equation, 1 - Vc = exp[-Kf(t)n], was used where f(t) is the integral of the growth function, (1 - Vc)m. The validity of the equation was tested by analyzing the isothermal crystallization kinetic data of poly(ethylene terephthalate) from the melt using differential scanning calorimetry.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310209
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  • 2
    Electronic Resource
    Electronic Resource
    The coupled relaxation model for toner melt rheology (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 99-103 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Process changes aimed at improving printer engine performance must take into consideration not only the process variables (such as nip temperature and pressure and process time to), but also the melt rheological variables (such as the characteristic time scale of the toner Tc). The melt rheology relevant to the electrophotographic toner fusing process is discussed. One criterion for toner quality can be conveniently measured through the Deborah number De, which is the ratio of Tc to to. Modification of the melt rheology by matrix polymer composition and carbon black size and concentration has previously been explored. Here, the melt rheology of toners with a range of gel content was studied using a step shear test. The coupled relaxation model was employed to fit the stress relaxation data. The viscoelastic properties were calculated from the melt data with this model. These properties were then used to estimate the strain deformation of the toner as it passes through the nip with arbitrary residence time and nip pressure as a function of gel content. This method can be used to match the toner melt properties with the processing conditions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310207
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  • 3
    Electronic Resource
    Electronic Resource
    Masthead (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310301
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  • 4
    Electronic Resource
    Electronic Resource
    A unified simulation of the filling and postfilling stages in injection molding. Part II: Experimental verification (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 125-139 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The unified numerical simulation of the filling/postfilling stages of the injection-molding process described in Part I is compared in the present paper with experimental results obtained with instrumented test molds. Flush-mounted pressure traces in the delivery system as well as in the cavity are favorably compared with corresponding predictions for both an amorphous and a semicrystalline polymer. It is demonstrated that the present unified formulation is well suited to handle complicated molds where compressibility effects can become important even during the filling stage, as portions of the cavity fill and undergo a packing behavior even when other regions of the cavity are still only partially filled.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310211
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  • 5
    Electronic Resource
    Electronic Resource
    A unified simulation of the filling and postfilling stages in injection molding. Part I: Formulation (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 116-124 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This study employs a unified theoretical model to simulate the filling and postfilling stages of the injection-molding process. Implementation of such a model is based on a hybrid finite-element/finite-difference numerical solution of the generalized Hele-Shaw flow of a compressible viscous fluid under nonisothermal conditions. The shear viscosity of the polymeric material is represented by a Cross model for the shear-rate dependence and a WLF-type functional form for the temperature and pressure dependence, whereas the specific volume is modeled in terms of a double-domain Tait equation. The analysis also handles variable specific heat and thermal conductivity of the polymer as a function of temperature. Complex thin parts of variable thickness can be modeled and discretized by flat, triangular finite elements which may have arbitrary orientation in three-dimensional space, whereas runners and possible round pins or bosses in the part are represented as one-dimensional circular-tube elements. A control-volume scheme is employed that leads to automatic melt-front advancement during the cavity-filling stage.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310210
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  • 6
    Electronic Resource
    Electronic Resource
    Models for the compressibility of layered polymeric sponges (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 140-144 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The characteristic sigmoid compressive stress-strain relationships of sponges and their layered arrays are described by two kinds of mathematical models having three experimentally determined parameters. Since sponge compression is not accompanied by a significant cross-sectional area expansion, it was assumed that the stress in a multilayered array is the same in each layer. This enables prediction of the array's stress-strain relationship from the parameters of the individual layers and their known thickness. The applicability of the method is demonstrated with experimental data of two kinds of double-layered arrays of polyurethane sponges. It is shown that the arrays' compressive behavior can be satisfactorily predicted irrespective of the mathematical form of the model and whether the strain is expressed as engineering strain or Hencky's.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310212
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  • 7
    Electronic Resource
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    Development of density distributions in injection molded amorphous engineering plastics. Part I (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 145-152 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The gapwise density distributions of the injection molded specimens of two engineering thermoplastics, i.e., poly(phenylene ether) and poly(ether imide), were characterized employing the density gradient column technique. The samples were molded using a 40t Van Dorn injection molding machine. The effects of the thermal history on the density distribution of unconstrained quenched specimens were also investigated. In addition, various material properties, such as pressure-volume-temperature, isothermal contraction, and pressure induced densification behavior were characterized, for the two resins employed in this study. The moldings of the two resins exhibited different trends in their density distributions. These findings were explained in terms of the competing effects of cooling rate and the pressure history experienced by the engineering plastic resins during the molding cycle. The data collected were also used as input to mathematical modeling of density distributions in injection molded articles, which is reported in Part II of this article.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310302
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  • 8
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    Steady solidification of non-Newtonian fluid flowing in a round tube (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 191-196 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The problem of steady solidification of a power law fluid flowing in a round tube was solved numerically. The fluid considered was a polymer with temperature dependent viscosity. The mathematical solution was obtained by using an implicit finite difference method. Results are presented to show the effects of the Peclet number, Nahme number, and the power law index on the profiles of the frozen layer. Melt temperature profiles at different axial locations are also presented.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310306
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  • 9
    Electronic Resource
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    Masthead (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310401
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  • 10
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    A study on bicomponent two-layer slot cast coextrusion (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 197-203 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Extensional flow of a bicomponent two-layer slot cast coextrusion process has been studied. A Newtonian and an upper-convected Maxwell fluid were considered to be the two layers, respectively, and the two-layer flow was assumed to be steady and isothermal. This choice was made as a simple model for a system which consists of two distinctly different fluids in terms of their extensional behaviors. Present study considered only the draw-down region where the film thickness changes slowly with the distance from the die exit. For this region, asymptotic solutions could be obtained for two limiting cases in which the elasticity effect of the Maxwell fluid layer is small and the applied tension at the take-off is large, respectively. When the elasticity effect is small, the melt thickness and the velocity profiles are exponential as in the case of a Newtonian single-layer flow. When the applied tension is large, on the other hand, the velocity profile is shown to be near linear. Furthermore, the viscoelasticity effect of the Maxwell fluid layer becomes so dominant that it dictates the mechanics of the coextrusion flow even when its flow rate and shear viscosity may be much smaller than those of the Newtonian layer.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310307
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  • 11
    Electronic Resource
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    Masthead (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310501
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  • 12
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    An experimental study of multiobjective dynamic optimization of a semibatch copolymerization process (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 353-364 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Optimal open loop control strategies are developed for a semibatch free radical copolymerization of methyl methacrylate and vinyl acetate using the multiobjective dynamic optimization method. A detailed kinetic model is validated through experimentation and used for the design of optimal controls. Both monomer feed rate and reactor temperature are varied to produce the copolymer of desired composition and molecular weight. The open loop control policies are implemented in a process control computer and tested on an experimental stirred tank polymerization system. Excellent agreement between the model predictions and the experimental data have been obtained.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310507
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  • 13
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    Dynamics of a cascade of two continuous stirred tank polymerization reactors with a binary initiator mixture (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 333-352 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The dynamic behavior of two continuous stirred tank reactors in series has been investigated for free radical solution polymerization of styrene with a binary mixture of two initiators having different thermal decomposition activities. For a wide range of initiator feed composition, both reactors exhibit quite complex nonlinear steady state and transient behavior. When the reactor residence time is used as a bifurcation parameter, the second reactor can have up to five steady states. For certain range of reactor operating conditions, bifurcations to various types of periodic solutions have been observed, such as Hopf bifurcation, isolas, period doubling, period-doubling cascade, and homoclinics. The effects of other reactor variables, such as total initiator concentration, coolant temperature, and reactor volume ratio on the reactor dynamics, are illustrated to show the complex dynamic behavior of the two-reactor system catalyzed by a mixture of t-butyl perbenzoate and benzoyl peroxide.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310506
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  • 14
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    Development of an in-line rheometer suitable for reactive extrusion processes (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 365-375 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper presents the development of a novel in-line extrusion rheometer based on the flow of polymer through a wedge (vertically tapered slit). This rheometer is suitable for measuring changes in rheological properties on-line during reactive extrusion, because it can be used to estimate the viscosity for a range of shear rates without the need to change the polymer flow rate (i.e., extruder throughput). Equations have been developed to estimate the parameters of the power-law equation, used to describe the viscosity-shear rate relationship, from measurements of pressure drops along the wedge. An experimental in-line wedge rheometer has been built and used to measure the viscosity for a series of polypropylenes prepared via reactive extrusion. Viscosity measurements from the experimental in-line wedge rheometer are compared with measurements from a capillary rheometer. Good agreement is found between the capillary and wedge rheometer measurements.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310508
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  • 15
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    Correction (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 391-391 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310511
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  • 16
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    Masthead (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310101
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  • 17
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    The design and manufacture of a graphite fiber reinforced poly(ether ether ketone) (PEEK) tetrahedron truss array (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1-5 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Orbital space structures are required to be lightweight, have high specific stiffness, have near-zero coefficient of thermal expansion, exhibit low outgassing, and be cost-effective. Graphite-reinforced thermoplastics have the potential to satisfy the criteria noted. However, prior to committing the materials to specific projects, technology demonstration and risk reduction is necessary. In order to demonstrate the application of fiber-reinforced thermoplastic composites for truss structure applications, a graphite-reinforced poly(ether ether ketone) (PEEK) composite tetrahedron truss array was designed and manufactured. The resulting structure clearly demonstrated that fiber-reinforced thermoplastic composites are a viable alternative to epoxy composites for orbital structures.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310102
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  • 18
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    371°C (700°F) properties of celion 6000/N-phenylnadimide modified pmr polyimide compositesPart of this work was performed under the auspice of the Polymer Composite Branch of the Materials Division, NASA-Lewis Research Center, Cleveland, Ohio. (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 14-19 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The 371°C (700°F) properties of Celion 6000/N-phenylnadimide modified PMR-15 polyimide composites were investigated to determine the feasibility of using these materials at a 371°C (700°F) service temperature. The processing characteristics and physical and mechanical properties of the composite systems are presented. The results of the 371°C thermooxidative stability study suggest that the composite materials can be considered for short-term (at least 100 hours) application at 371°C.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760310104
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  • 19
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    Mechanical properties and mechanism of the degradation process of 316°C isothermally aged graphite fiber/PMR-15 composites (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 6-13 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A series of graphite fiber/PMR-15 polyimide composites, isothermally aged at 316°C in flowing air (100 cc/min) for time periods up to 2000 h, were investigated for mechanical property changes, fiber/resin interface changes, overall dimensional changes, and weight loss. The mechanism of the degradation process is suggested based on shear and flexural property measurements at room temperature and 316°C, optical micrographs of composite cross sections, and SEM analysis of fractured surfaces. The fiber materials investigated in composite form were Celion 6000 unsized and epoxy sized. G40-700 unsized and epoxy sized, and T40R and IM6 both unsized.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760310103
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  • 20
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    Interpenetrating polymer network approach to tough and microcracking resistant high temperature polymers. Part III. LaRC-RP71 (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 28-33 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A high performance semi-interpenetrating polymer network (semi-IPN) has been synthesized from Thermid-600 and LARC-TPI. Notable improvements in resin fracture toughness and graphite fiber reinforced composite microcracking resistance over the unmodified Thermid-600 neat resin and composite have been realized. The chemistry, processing, physical and mechanical properties, and phase morphology of the neat resin and composite reinforced with graphite fibers are presented.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760310106
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  • 21
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    Interpenetrating polymer network approach to tough and microcracking resistant high temperature polymers. Part II. LaRC-RP41 (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 20-27 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Recently, we reported on the interpenetrating polyimide network (IPN) approach to develop tough and microcracking resistant high temperature matrix resins for use in aircraft/aerospace structural components. One such polymer developed is designated LaRC-RP40. This new simultaneous semi-IPN was prepared from easy-to-process but brittle crosslinking PMR-15 and tough but difficult-to-process linear NR-150B2. Significantly improved toughness, microcracking resistance, and glass transition temperature over PMR-15 were realized from the combination. These property improvements were achieved without compromising ease of processing, high temperature mechanical performance, and cost effectiveness compared to PMR-15. These results encouraged us to further explore this approach for the development of a wider range of polymers of basic technological and economic interest. In the present work, we combine crosslinking PMR-15 and linear LaRC-TPI to provide a new sequential semi-2-IPN called LaRC-RP41. The physical and mechanical properties of the neat resin and composite reinforced with graphite fibers are presented. The phase morphology and phase stability of the neat resin and composite studied by various techniques are also discussed.
    Additional Material: 15 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760310105
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  • 22
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    Mechanical properties in multidimensional composites (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 40-46 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The mechanical properties of three dimensional stitched composites were compared against those of the traditional two dimensional laminates. An attempt was made to correlate the change in properties to the change in the third directional fiber density. Tests conducted were the impact, three-point bending, damage tolerance, end notched flexure, and bending fatigue test. The results of these tests show that the third directional fibers can effectively inhibit delamination by increasing the interlaminar shear strength. Three dimensional composites also possess better damage tolerance, fracture toughness, and fatigue life. However, a high stitching density can degrade the in-plane properties of the composites.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760310108
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  • 23
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    Environmental effects on the water absorption and mechanical properties of carbon fiber reinforced PPS and PEEK composites. Part II (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 34-39 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Research has been conducted to investigate the water absorption in carbon fiber reinforced poly(ether ether ketone) (PEEK/CF) and poly(phenylene sulfide) composites (PPS/CF). Effect of humidity and temperature on tensile, flexural, and impact strength of these composites were also studied. Results indicated that the water absorbed in PPS/CF and PEEK/CF are 0.059 %wt, 0.130 %wt, 0.138 %wt, and 0.153 %wt at 80°C. 75 %RH and 85 %RH, respectively. The diffusion process is a classical Fickian diffusion in the temperature range investigated. The activation energies of diffusion are 667 cal/g-mole (for PPS/CF) and 8934 cal/g-mole (for PEEK/CF) at 80°C and 75 %RH. The retention of mechanical properties of these composites is very good under hot-wet conditions. These composite materials can be served as high performance materials even in the hostile environment. PEEK/CF composites shows excellent mechanical properties retention even at 80°C, 75 %RH, and 85 %RH.
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    URL: http://dx.doi.org/10.1002/pen.760310107
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    Vibration based non-destructive evaluation of polymer composites (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 47-55 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A feasibility study on the use of vibration spectrum analysis as a tool for nondestructive evaluation (NDE) of polymer composites was conducted. Material integrity of polymer composite samples was determined from the vibrational measurements by analyzing the resonant frequency and damping information. A number of important “states” in the composites tested could be characterized by this analysis. The vibration tehnique was found to be sensitive to physical flawing (fiber breakage, delamination, and matrix cracking). Vibrational NDE has many potential advantages that make it very attractive for composite applications. These include the ability to make global measurements of large structures in real-time, no geometry restrictions, and high sensitivity to a wide variety of damage states.
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    URL: http://dx.doi.org/10.1002/pen.760310109
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    In-situ monitoring of the resin transfer molding impregnation and cure process (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 56-60 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Resin transfer molding (RTM) of advanced fiber architecture materials promises to be a cost effective process for obtaining composite parts with exceptional strength. However there are a larger number of material processing parameters that must be observed, known, and/or controlled during the resin transfer molding process. These include the viscosity both during impregnation and cure. In-situ sensors which can observe these processing properties within the RTM tool during the fabrication process are essential. This paper will discuss recent work on the use of frequency dependent electromagnetic sensing (FDMS) techniques to monitor these properties in the RTM tool. Our objective is to use these sensing techniques to address problems of RTM scaleup for large complex parts and to develop a closed loop, intelligent, sensor controlled RTM fabrication process.
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    Factor analysis in chemistry, (2nd edition), E. R. Malinowski, Wiley-Interscience, 1991. ISBN 0-471-53009-3. Price £43.70 (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 545-545 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050607
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    Diagnostika Sostava Materialov Rentgenodifrakcionnimi I Spektralnymi Metodami (Identification of materials by X-ray diffraction and spectroscopical Techniques) (in Russian), M. S. Nakhmanson and V. G. Feklitschev, Mashinostroenie, Leningrad, 1990. 357 pages. ISBN 5-217-00915-2, Rubl 5.40 (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 546-547 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050608
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    Recent developments in multivariate calibrationInvited Paper. (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 129-145 
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    ISSN: 0886-9383
    Keywords: Multivariate calibration ; Biased regression ; Partial least squares (PLS) ; Principal component regression (PCR) ; Model validation ; Non-linear calibration ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: With the goal of understanding global chemical processes, environmental chemists have some of the most complex sample analysis problems. Multivariate calibration is a tool that can be applied successfully in many situations where traditional univariate analyses cannot. The purpose of this paper is to review multivariate calibration, with an emphasis being placed on the developments in recent years. The inverse and classical models are discussed briefly, with the main emphasis on the biased calibration methods. Principal component regression (PCR) and partial least squares (PLS) are discussed, along with methods for quantitative and qualitative validation of the calibration models. Non-linear PCR, non-linear PLS and locally weighted regression are presented as calibration methods for non-linear data. Finally, calibration techniques using a matrix of data per sample (second-order calibration) are discussed briefly.
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    URL: http://dx.doi.org/10.1002/cem.1180050303
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    Real-time filtering of data from mobile, passive remote infrared sensors with principal component models of backgroundInvited Paper. (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 147-161 
    Details
    ISSN: 0886-9383
    Keywords: Digital filtering ; Real-time analysis ; Kalman filtering ; Infrared spectroscopy ; Principal components regression ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Real-time monitoring of pollutant levels from a mobile measuring platform requires fast, flexible data analysis methods. This paper reports a method for rapid analysis of passive remotely sensed infrared data with the aid of a Kalman filter. The background spectra produced by emission from the atmosphere are modelled at the start of the data collection sequence with a simple principal components model obtained by eigenanalysis of the initial ‘blank’ data taken with the spectrometer. The species of interest are included in the state space model by a separate measurement of their infrared spectra. It is demonstrated that for best filter performance in detecting the simulated pollutant species SF6 in the atmosphere, a filter model with two principal components describing the emission background works best. The filter ‘maps’ of SF6 closely follow the integrated spectral intensities measured after removal of suitable backgrounds.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/cem.1180050304
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    Examining large databases: A chemometric approach using principal component analysisInvited Paper. (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 163-179 
    Details
    ISSN: 0886-9383
    Keywords: Principal component analysis ; Factor analysis ; Chemometrics ; Exploratory data analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Principal component analysis is used to examine large multivariate databases. The graphical approach to exploratory data analysis is described and illustrated with a single example of chemical composition data obtained on environmental dust particles. While the graphical approach to exploratory data analysis has certain advantages over the numerical procedures, the empirical approach described here should be viewed as complementary to the more robust treatments that statistical methodologies afford.
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    Box-Cox transformations in the analysis of compositional data (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 227-239 
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    ISSN: 0886-9383
    Keywords: Unit-sum constraint ; Mixing proportions ; Ratio data ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The statistical analysis of compositional data is of fundamental importance to practitioners in general and to chemists in particular. The existing methodology is principally due to Aitchison, who effectively uses two transformations, a ratio followed by the logarithmic, to create a useful, coherent theory that in principle allows the plethora of normal-based multivariate techniques to be used on the transformed data. This paper suggests that the well-known class of Box-Cox transformations can be employed in place of the logarithmic to significantly improve the existing methodology. This is supported in part by showing that one of the most basic problems that Aitchison managed to overcome, namely the specification of an interpretable covariance structure for compositional data, can be resolved, or nearly resolved, once the ratio transformation has been applied. Hence the resolution is not directly dependent on the logarithmic transformation. It is then verified that access to the general Box-Cox family will allow a more accurate use of the normal-based multivariate techniques, simply because better fits to normality can be achieved. Finally, maximum likelihood estimation and some associated asymptotics are employed to construct confidence intervals for ratios of the true, unknown compositional constituents. Heretofore this had not been done even in the context of the logarithmic transformation. Applications to real data are presented.
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    Finding causes of outliers in multivariate environmental data (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 241-248 
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    ISSN: 0886-9383
    Keywords: Multivariate kurtosis ; Generalized distance ; Multivariate outliers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Multivariate outliers in environmental data sets are often caused by atypical measurement error in a single variable. From a quality assurance perspective it is important to identify these variables efficiently so that corrective actions may be performed. We demonstrate a procedure for using two multivariate tests to identify which variable ‘caused’ each outlier. The procedure is tested with simulated data sets have have the same correlation structure as selected water chemistry variables from a survey of lakes in the Western United States. The success rates are evaluated for three of the variables for sample sizes of 50 and 100, significance levels of 0.01 and 0.05 and various amounts of mean shift. The procedure works best for highly correlated variables.
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    A statistical procedure to evaluate clean-up standards (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 249-261 
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    ISSN: 0886-9383
    Keywords: Asymptotic power ; Clean-up standard ; Gamma distribution ; Likelihood ratio test ; Uniformly most powerful unbiased test ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The object of this paper is to develop a suitable statistical procedure to evaluate clean-up standards at hazardous waste sites. Under the assumptions that contaminant masses at a site follow a gamma distribution and that the data from the pre-remediation baseline sample as well as from the interim or final sample taken after a certain period of operation are both distributed as gamma with the same shape parameter but different scale parameters, we derive a uniformly most powerful unbiased test of the hypothesis that a specified percentage of contaminant mass has been reduced. A large-sample approximation of the exact test procedure and a comparison with the likelihood ratio test are provided.
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    URL: http://dx.doi.org/10.1002/cem.1180050312
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    The quality of mean and variance estimates for normal and lognormal data when the underlying distribution is misspecified (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 263-271 
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    ISSN: 0886-9383
    Keywords: Mean ; Variance ; Lognormal ; Optimal estimators ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Theoretical and simulation results are employed to evaluate mean and variance estimates for normal data when a lognormal distribution is assumed and for lognormal data when a normal distribution is assumed. Misspecifying the distribution leads to the use of suboptimal estimation methods. However, the results show that the suboptimal methods still produce estimators of good quality (low bias and variance) relative to the minimum variance unbiased estimators for each distribution, at least when practical efficiency is considered.
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    Correspondence analysis used in the evaluation of lakewater chemistry in the Adirondacks (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 273-290 
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    ISSN: 0886-9383
    Keywords: Correspondence analysis ; Eastern Lake Survey - Phase I data ; Acidic deposition ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Correspondence analysis (CA) was applied to lakewater data in order to study the effects of acidic deposition on the geochemical composition of lakes in the Adirondacks. The lake chemistry data analyzed were taken from the Eastern Lake Survey - Phase I (ELS-I) conducted by the U.S. Environmental Protection Agency. CA was used to identify ‘outlying’ lake samples as well as ‘superflous’ and ‘unresolved’ analytes. Correlational relationship among analytes were also examined.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/cem.1180050314
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    Estimation of errors in absorbance ratio measurements (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 291-298 
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    ISSN: 0886-9383
    Keywords: Absorbance ratio ; Statistical confidence ; Quality control ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ratio measurements are commonly used to address a variety of analytical problems in environmental, forensic and pharmaceutical laboratories. In absorbance ratioing techniques, analytical chemists rely on the spectral features of the analyte(s) of interest. The absorbances at two wavelengths are monitored and the ratio of these two absorbances is computed. This ratio is then used to confirm the identity of the analyte(s) of interest, the purity of a product of the overlap of chromatographic peaks. These decisions often have far-reaching consequences (e.g. the identification of the source, biogenic or petrogenic, of hydrocarbons in biological tissues or water). Given the cost and the liabilities associated with such decisions, it is unfortunate that these ratios are seldom reported with any statistical confidence. The purpose of this study is to delineate the parameters that affect absorbance ratio measurements. The models that can be used to estimate the statistical confidence in these measurements are derived and evaluated experimentally. The results show that these models can estimate the relative standard deviations in absorbance ratios accurately. They can also estimate the effect of signal-to-noise ratio and the choice of wavelengths on the precision of absorbance ratios.
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    URL: http://dx.doi.org/10.1002/cem.1180050315
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    Likelihood techniques for interlaboratory calibration in the national stream survey (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 299-308 
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    ISSN: 0886-9383
    Keywords: Errors in variables ; Orthogonal regression ; Latent variables ; Acid rain ; Acidic deposition ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Techniques for testing for and estimating relative bias between two laboratories are developed and applied to a survey of the chemistry of streams in the United States. The design of the quality assurance program allows estimation of linear corrections for bias as well as testing of the hypothesis of linearity. Designs of this type are useful, but improvements are suggested.
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    On confidence intervals for the product of three means of three normally distributed populations (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 309-319 
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    ISSN: 0886-9383
    Keywords: Confidence intervals ; Products of normal random variables ; Risk/exposure modeling ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In many environmental applications, such as exposure assessment and risk modelling, the desired estimate is a random variable computed as the product of three independently distributed random variables. These variables may not necessarily have the same mean and variance. The method for finding the 100(1 - α)% confidence interval for the mean of the product random variable has been proposed by some practitioners as the product of the 100(1 - α)% confidence interval of the three means. In this paper we show that the distribution of the product of three independent normal variables is not normal. We find the mean and variance of the product distribution. Further, we show that although the mean of the product is equal to the product of the means, the product of the three confidence intervals is not a good approximation of the confidence intervals for the mean of the product variable. The confidence interval of the mean of the product variable may be estimated by computer simulation. An algorithm for estimating the confidence interval for the mean of the product random variable is given. The program implementing this algorithm is given as an appendix.
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    URL: http://dx.doi.org/10.1002/cem.1180050317
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    Comparison of two screening methods for the detection of volatile organic compounds in ground water (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 321-331 
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    ISSN: 0886-9383
    Keywords: Screening ; Ground-water quality ; Monitoring ; Volatile organic compounds (VOCs) ; Optimization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that the presence of 31-35 commonly measured volatile organic compounds (VOCs) in ground water can be detected with small error rates by using screening methods which analyze for a subset of such VOCs. A study of selected data sets indicates that analytical determinations of only from two to eight VOCs will suffice to detect 95% of all VOC hits. It is also shown that a serially optimal algorithm for selecting the VOCs for screening is very nearly as accurate as a globally optimal algorithm and much easier to implement. These conclusions are supported by empirical evidence from two drinking-water data sets and one hazardous waste site data set. Additional research areas are also outlined.
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    Masthead (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991) 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050401
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    Diary (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. i 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050402
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    A bootstrap resampling scheme for using the canonical correlation technique in rank estimation (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 333-343 
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    ISSN: 0886-9383
    Keywords: Rank estimation ; Bootstrap resampling ; Canonical correlation ; Excitation-emission matrix ; Singular value decomposition ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rank estimation by canonical correlation analysis in multivariate statistics has been proposed as an alternative approach for estimating the number of components in a multicomponent mixture. A methodological turning point of this new approach is that it focuses on the difference in structure rather than in magnitude in characterizing the difference between the signal and the noise. This structural difference is quantified through the analysis of canonical correlation, which is a well-established data reduction technique in multivariate statistics. Unfortunately, there is a price to be paid for having this structural difference: at least two replicate data matrices are needed to carry out the analysis.In this paper we continue to explore the potential and to extend the scope of the canonical correlation technique. In particular, we propose a bootstrap resampling method which makes it possible to perform the canonical correlation analysis on a single data matrix. Since a robust estimator is introduced to make inference about the rank, the procedure may be applied to a wide range of data without any restriction on the noise distribution. Results from real as well as simulated mixture samples indicate that when used in conjunction with this resampling method, canonical correlation analysis of a single data matrix is equally efficient as of replicate data matrices.
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    Three-way methods for the calibration of chromatographic systems: Comparing PARAFAC and three-way PLS (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 345-360 
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    ISSN: 0886-9383
    Keywords: Three-way PCA ; Three-way PLS ; PARAFAC ; Trilinear ; Unfolding ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For the calibration of chromatographic systems, different methods can be used. One class of methods utilizes three-way approaches. The calibration problem is stated in such a way that the decomposition of a three-way array can serve for the prediction of retention on new stationary phases.Two three-way approaches are presented: the Unfold-PCA and PARAFAC models. The theory of both methods is presented and the differences are highlighted, the main difference being that PARAFAC is a trilinear decomposition whereas Unfold-PCA is not. Both three-way methods are evaluated on a small data set consisting of retention measurements of eight solutes at six mobile phase compositions on six stationary phases. The differences in performance of the two models are minor.For calibration purposes, two variants of the methods are discussed: three-way PLS and an extension of PARAFAC. Again the theory and differences between the two methods are explained. The predictive performance of the two methods is compared using the same data set as earlier. The differences in predictive performance, however, are minor. Both methods are capable of predicting 98% of the variation in the test sets. Yet, there are other considerations when comparing methods than predictive performance, e.g. the quality of the predictions.
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    Estimation in compositional data analysis (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 361-374 
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    ISSN: 0886-9383
    Keywords: Closure ; Normalization ; Multivariate trimming ; Minimum distance ; Bootstrap ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Compositional data arise naturally in several branches of science, including chemistry, geology, biology, medicine, ecology and manufacturing design. In chemistry, these constrained data seem to occur typically when raw data are normalized or when output is obtained from a constrained estimation procedure, such as might be used in a source apportionment problem. It is important not only for chemists to be aware that the usual multivariate statistical techniques are not applicable to constrained data, but also to have access to appropriate techniques as they become available. The currently available methodology is due principally to Aitchison and is based on log-normal models. This paper suggests new parametric and non-parametric approaches to significantly improve the existing methodology. In the parametric setting, some recent work of Rayens and Srinivasan is extended and a practical regression model is proposed. In the development of the non-parametric approach, minimum distance methods coupled with multivariate bootstrap techniques are used to obtain point and region estimators.
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    A test of three fitting criteria for multiresponse non-linear modeling (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 375-387 
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    ISSN: 0886-9383
    Keywords: Determinant criterion ; Multiresponse non-linear fitting ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This work evaluates objective functions for multiresponse non-linear modeling using computer simulations. Tests are performed under a variety of signal-to-noise ratios and noise variance-covariance structures. The standard error of prediction for the model parameters, computed from 50 trials, is used for performance comparisons. The full rank and rank-deficient problems are considered. For the full rank problem one model was investigated, a first-order two-step consecutive reaction model, and two objective functions were considered, the total sum of squares and the determinant criterion. No distinction could be made between the two objective functions for this model.For the rank-deficient case two models were investigated, a first-order two-step consecutive reaction as in the full rank case, and a pH titration model described by the Henderson-Hasselbalch equation. Three objective functions were investigated for the rank-deficient case, the total sum of squares, a weighted total sum of squares and the determinant criterion. The total sum of squares was found to perform poorly under all conditions tested compared to the weighted total sum of squares and the determinant criterion. The determinant criterion was found to perform much better than the other two criteria when the data have a combination of a low signal-to-noise ratio and high variance-covariance noise structure.
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    The chemometrics team of MITAC (Micro and Trace Analysis Center), University of Antwerp, Belgium (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 405-409 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180050408
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    Comparison of pattern recognition descriptors for chemical acoustic emission analysis (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 389-403 
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    ISSN: 0886-9383
    Keywords: Acoustic emission ; Pattern recognition ; Feature selection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Features used to characterize acoustic emission signals from chemical systems are evaluated with regard to their potential for pattern recognition. Eight chemical systems involving phase transitions, hydration, dissolution and effervescence are employed and treated as separate signal classes. These are compared pairwise and the discriminatory capabilities of about 50 features are investigated by computing Fisher weights. Time domain and frequency domain descriptors are examined. Correlations among the features evaluated are also reported. Recommended descriptors are the mean and median frequencies, frequency bandwidth, number of level crossings (0% and 25%), crest factor (time and frequency domains), half-life, kurtosis and normalized percentiles of the signal and its power spectrum. The effectiveness of the recommended descriptors is demonstrated through the separation of signal classes in two different systems (melting ice and an enzyme-catalyzed gas formation reaction) by principal components analysis.
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    Scientific computing and automation (Europe) 1990 (Proceedings of the Scientific Computing and Automation (Europe) Conference, 12-15 June 1990, Maastricht, The Netherlands), edited by E. J. Karjalainen for the series Data Handling in Science and Technology, 6, Elsevier Science Publishers, Amsterdam, 1990, 514 pp., ISBN 0-444-88949-3, US$220.00/Dfl. 385.00 (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 411-412 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    UNSCRAMBLER 11, version 3.10: A program for multivariate analysis with PLS and PCA/PCR. Available from CAMO AS, Jarlevn. 4, Trondheim, Norway. Price $3000; academic discount price $1500 (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 413-415 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180050410
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    Announcement (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 416-416 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Masthead (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991) 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180050501
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    Diary (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. i 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180050502
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    Rapid estimation of the number of coeluting components in liquid chromatography by factor analysis (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 417-434 
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    ISSN: 0886-9383
    Keywords: Factor analysis ; Power density distribution ; Chromatography ; Absorption spectroscopy ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Evaluation of the results of factor analysis of sets of spectroscopically detected chromatograms is carried out by examining the shapes of the abstract factors. This is done either by visual inspection or by analysis of the power density spectra produced from them. Owing to constraints imposed by the column function and the spectroscopic instrument function, the information content of the chromatograms necessarily occurs at low spatial frequencies. As a consequence, it appears as relatively broad features in the abstract chromatograms and as a peak in the low-frequency region of the corresponding power density plot. On the basis of examination of the power density distribution, a well-defined distinction is made between primary and secondary abstract factors. The major uncertainty encountered in determining the number of chemical components appears to arise from effects of contaminants in reagents.
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    A class-modelling technique based on potential functions (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 435-453 
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    ISSN: 0886-9383
    Keywords: Class-modelling methods ; Potential functions ; Pattern recognition ; Discriminant analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A probabilistic and distribution-free class-modelling technique is developed from potential function discriminant analysis. In the multidimensional space of variables the class boundary is built either by the sample percentile of the probability density estimated by means of potential functions, or by the estimate of the ‘equivalent’ determinant of the variance-covariance matrix. The equivalent determinant is that of a hypothetical multivariate normal distribution whose mean probability density was obtained by potential functions. The bases of this modelling rule are evaluated by means of Monte Carlo experiments. The results on four datasets are used to measure the performances of this method, which equal and sometimes exceed the performances of parametric class-modelling methods based on linear and quadratic discriminant analysis which were used for comparison.
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    Correspondence analysis and adsorbate selection for chemical sensor arrays (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 455-465 
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    ISSN: 0886-9383
    Keywords: Correspondence analysis ; Cluster analysis ; Optimization ; Eigenanalysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carey et al. utilized principal components analysis (PCA) to analyze frequency shift data obtained from piezoelectric sensors formed by coating quartz crystals with 27 different GC stationary phases and tested using 14 analytes. The objective of the analysis was to determine an optimal reduced set of coatings for detection of the analytes. The results were correlated with those obtained from cluster analysis. In this paper the data are re-analyzed using correspondence analysis (CA). The advantage of using CA include a symmetric treatment of sensor coatings and analytes and better identification of the representation of the analytes in terms of the detection components. The results obtained by the conjunctive use of PCA, a varimax rotation and cluster analysis were obtained by CA.
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    Fuzzy multivariate rule-building expert systems: Minimal neural networks (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 467-486 
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    ISSN: 0886-9383
    Keywords: Expert system ; Neural network ; Fuzzy entropy ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A fuzzy multivariate rule-building expert system (FuRES) has been devised which also functions as a minimal neural network. This system builds rules from training sets of data that use feature transformation in their antecedents. The rules are constructed using the ID3 algorithm with a fuzzy expression of classification entropy. The rules are optimal with respect to fuzziness and can accommodate overlapped and underlapped clusters of data. The FuRES algorithm combines the benefits obtained from simulated annealing and gradient optimization, which provide robustness and efficiency respectively. FuRES classification trees support OR logic in their inference. The system automatically generates meaningful and consistent certainty factors during rule construction. Unlike other neural networks, FuRES uses local processing which furnishes qualitative information in the rule structure of its classification trees and variable loadings of the weight vectors.
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    Masthead (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991) 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050601
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    Diary (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. i 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050602
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    Multivariate calibration when data are split into subsets (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 487-501 
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    ISSN: 0886-9383
    Keywords: Calibration ; Locally linear models ; Discrimination ; Optimality ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A calibration situation is considered where the calibration data are split into subsets with good linear relationship between y and x within each group. Different strategies for good prediction in this case are proposed. Modifications for collinear data are considered and a simple simulated data set is used for illustration.
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    Rank-order analysis for robust multiresponse, multiblock comparisons: Evaluation of herbicide interactions (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 503-521 
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    ISSN: 0886-9383
    Keywords: Antagonism ; Bounded ordinal scale ; Herbicide interaction ; Inter block comparisons ; Non-parametric ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Studies of interactions among bioactive compounds are often difficult to interpret unambiguously. A priori assumptions about the nature of such interactions can seriously distort analysis of the data. By applying a rank order analysis appropriate to the naturally ordinal scale of response to xenobiotic insult, several co-herbicides were successfully identified from among numerous candidates in an experiment involving multiple blocks, rates and species. Moreover, underlying herbicide interactions were substantiated and identified which were not apparent by more traditional parametric analysis.
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    Laboratorio di Chemiometria, University of Perugia, Italy (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 537-543 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/cem.1180050606
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    Comparison of measurement methods based on a model for the error structure (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 523-536 
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    ISSN: 0886-9383
    Keywords: Measurement errors ; Method comparison ; Mean square successive difference ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Comparison of methods is a technique often used for investigation of systematic errors of measurement methods. As concerns the design and analysis of such comparisons, much variety of opinion and practice exists. In one approach a few specimens are measured several times by different operators in different laboratories (reproducibility conditions) and in another approach several specimens are measured on one or a few occasions by one operator in the same laboratory (repeatability conditions). In this paper a model for the error structure of measurements is formulated and it is emphasized that one has to distinguish between two types of systematic errors: the first type depends only on the level of the measured quantity and the second type is specific for the separate specimens. On the basis of this model the information which can be obtained from the different designs of method comparisons is discussed. A new approach for the analysis of method comparisons with many specimens is also proposed.
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    Masthead (1991)
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    Journal of Chemometrics 5 (1991) 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180050101
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    Diary (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. i 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180050102
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    Tutorial to robust statistics (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 1-20 
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    ISSN: 0886-9383
    Keywords: Averaging ; Median ; Outliers ; Regression ; Residuals ; Robustness ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this tutorial we first illustrate the effect of outliers on classical statistics such as the sample average. This motivates the use of robust techniques. For univariate data the sample median is a robust estimator of location, and the dispersion can also be estimated robustly. The resulting ‘z-scores’ are well suited to detect outliers. The sample median can be generalized to very large data sets, which is useful for robust ‘averaging’ of curves or images. For multivariate data a robust regression procedure is described. Its standardized residuals allow us to identify the outliers. Finally, a survey of related approaches is given. (This review overlaps with earlier work by the same author, which appeared elsewhere.)
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    Use of the Wronskian determinant in the study of multicomponent systems (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 21-35 
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    ISSN: 0886-9383
    Keywords: Wronskian determinant ; Multicomponent systems ; Derivative spectroscopy ; Spline functions ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of Wronskian determinants in the study of multicomponent systems is proposed. The general theory is presented and applied to the spectrophotometric determination of the number of linearly independent components-absorbers. A detailed study of a two-component system is presented and analysed. Numerical methods for smoothing and differentiation of digitized spectra via cubic splines are used.
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    Announcement (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 69-69 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180050109
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    Masthead (1991)
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    Journal of Chemometrics 5 (1991) 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180050201
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    Diary (1991)
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    Journal of Chemometrics 5 (1991), S. i 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180050202
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    Editorial (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 71-71 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180050203
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    The use of a ratio method as an alternative to constrained deconvolution (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 85-95 
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    ISSN: 0886-9383
    Keywords: Deconvolution ; Gold's ratio ; Iterative deconvolution ; Chromatographic deconvolution ; Peak restoration ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper will consider the use of an iterative ratio technique called Gold's ratio method as an alternative to iterative constrained deconvolution methods for the restoration of overlapped and noisy chromatograpic peaks. The study will consist of first describing the technique and then evaluating its performance with respect to Jansson's deconvolution procedure. A Hewlett-Packard 5890A gas chromatograph will be used to generate most of the test data. The evaluation criteria will include convergence rates, peak area errors and variances, retention time variances and noise performance.
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    A new serial method for searching the optimum operating conditions of a technological process (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 73-84 
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    ISSN: 0886-9383
    Keywords: Optimization ; Technological process ; COMPLEX algorithm ; ANTICOMPLEX algorithm ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new program, named ANTICOMPLEX, has been specially written for searching the optimum conditions of a technological process. The algorithm is based on an iterative procedure with, at each step, a random sampling for a better exploration of the hyperspace of the parameters. Since the process is considered as a ‘black box’, the program operates by successive reductions of the variation domains with a strategy derived from some function optimization (COMPLEX). This approach is very flexible and the experimenter can stop the investigation at any series of experiments according to the desired accuracy for the optimum region. This program has been successfully tested on several real processes. This paper gives a complete description of the approach together with two illustrations on simulated processes.
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    The Laboratory for Chemometrics, University of Washington, Seattle (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 113-116 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180050207
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    Announcements (1991)
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    Journal of Chemometrics 5 (1991), S. 117-119 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180050208
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    Regression on multivariate images: Principal component regression for modeling, prediction and visual diagnostic tools (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 97-111 
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    ISSN: 0886-9383
    Keywords: Multivariate images ; Principal component regression ; Multivariate image regression ; Regression model ; Predicted image(s) ; Prediction quality scatter plot ; Visual diagnostic tools ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Regression between two blocks (usually called ‘dependent’ or Y and ‘independent’ or X) of data is a very important scientific and data-analytical tool. Regression on multivariate images is possible and constitutes a meaningful addition to existing univariate and multivariate techniques of image analysis. The regression can be used as a modeling tool or for prediction. The form of the regression equation chosen is dependent upon problem specification and information at hand. This paper describes the use of principal component regression (PCR). Both model building and prediction are presented for continuous Y-variables. The final goal is to supply new image material that can be used for visual inspection on a screen. Also, visual tools for diagnosis of model and prediction are provided, often based on derived image material. Examples of modeling and prediction are given for six channels in a seven-channel satellite image.
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    Masthead (1991)
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    Journal of Chemometrics 5 (1991) 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050301
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    Some issues in chemometrics with environmental applications (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 121-128 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
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    Splitting of calibration data by cluster analysis (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 49-65 
    Details
    ISSN: 0886-9383
    Keywords: Calibration ; Cluster analysis ; Local linearity ; Mahalanobis distance ; Residual distance ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The topic of the present paper is the splitting of calibration data into subgroups with improved linearity in each group. The method proposed is based on a criterion which is a weighted average of a Mahalanobis distance and a squared regression residual. The algorithm used to find the solution is based on fuzzy clustering. Two examples are given to illustrate the theory.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/cem.1180050106
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    Generalized simulated annealing for calibration sample selection from an existing set and orthogonalization of undesigned experiments (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 37-48 
    Details
    ISSN: 0886-9383
    Keywords: Optimization ; Simulated annealing ; Calibration ; Experimental design ; Multicomponent analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Generalized simulated annealing (GSA) is an optimization procedure for locating the global optimum (maximum or minimum) of multidimenisonal continuous functions. GSA has been modified for optimization of discrete functions. Selection of calibration samples from an existing set defines discrete optimization and GSA is used to select optimal sets of calibration samples for specific analysis samples. The procedure is applied to near-infrared spectra. When compared to using the complete set of 37 calibration samples, concentration prediction errors were reduced 50%-100% by using select sets of two to seven calibration samples. Additionally, GSA was able to improve a poorly designed experiment. GSA devised augmented experimental designs such that the overall experimental design (original plus augmented) was more orthogonal than the original.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/cem.1180050105
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    Computational methods in the chemical sciences, A. F. Carley and P. H. Morgan, Ellis Horwood, Ltd, Chichester, U.K., 1989. ISBN 0-85312-746-8 (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 68-69 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050108
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    Computerized multiple input chromatography, M. Kaljurand and E. Küllik, Ellis Horwood, Chichester, U.K., 1989. No. of pages: 225. ISBN 0-7458-0120-X. Price £45.00 (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 67-67 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050107
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    Experimental design in chemometricsInvited Paper. (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 181-192 
    Details
    ISSN: 0886-9383
    Keywords: Chemometrics ; Systems theory ; Experimental design ; Multivariate analysis ; Measurement science ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemometrics is defined as the application of mathematical and statistical methods to chemical systems. Systems theory is seen to be useful for organizing and categorizing the inputs to and outputs from chemical systems. Advances in measurement science in the 1950s and 1960s, particularly in analytical chemistry, created a need for a multivariate approach to data analysis. Early chemometrics emphasized the use of structure-finding methods for existing data sets. In many instances, data sets can be obtained from designed experiments. Such data sets are more likely to contain the desired information and the data can usually be acquired at less cost. Renewed interest in statistical process control will provide many new, more robust data sets in the future.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/cem.1180050306
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    Simultaneous analysis of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) by spectrophotometry and the Kalman filter (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 193-199 
    Details
    ISSN: 0886-9383
    Keywords: Kalman filter ; Chemometrics ; 5-Br-PADAP ; Metallic ions ; Simultaneous spectrophotometric determination ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper describes the simultaneous determination of cobalt, nickel, copper, zinc and cadmium by spectrophotometry and the Kalman filter method. Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) react with 5-bromo-2-(2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) in the presence of cationic surfactant cetyl pyridinium bromide (CPB) to form five different coloured ternary complexes. The absorption curves of these complexes overlap severely in the scanning range 500-620 nm. The Kalman filter algorithm is successfully applied to resolve the overlapped absorption curves and therefore makes the simultaneous determination of these metallic ions possible without tedious pretreatment. The proposed method is applied to analyse the titled elements in synthetic samples and in environmental samples such as hair, fingernail and river water samples with satisfactory results.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/cem.1180050307
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    Step function technique for estimating data uncertainty in experimental results (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 201-209 
    Details
    ISSN: 0886-9383
    Keywords: Uncertainty ; Step function ; Additive model ; Transformation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An additive model is used to express the observed value of a sample characteristic as the sum of the true sample characteristic and a value of the data collection error, commonly known as experimental error. The data uncertainty of the experimental results (or of a survey data set) is defined as the expected squared error. The expected squarred error may change with the sample characteristic, e.g. the error moment could be concentration-dependent. The relationship between the error variance and the analyte concentration may not be very distinct. In such a case the data transformation to stabilize the error moments may not be appropriate. A step function is proposed as an alternative way to represent the second moment of the error. The data uncertainty is defined as the weighted average of the step values of the second raw moment of the error, using the appropriate proportions of the routine samples as weights. The data uncertainties associated with the different data collection stages were evaluated by using regional soil survey data.
    Additional Material: 3 Tab.
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    URL: http://dx.doi.org/10.1002/cem.1180050308
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    Expectation-maximization algorithm for regression, deconvolution and smoothing of shot-noise limited data (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 211-225 
    Details
    ISSN: 0886-9383
    Keywords: Shot noise ; Expectation-maximization ; Regression ; Deconvolution ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simple algorithm for deconvolution and regression of shot-noise-limited data is illustrated in this paper. The algorithm is easily adapted to almost any model and converges to the global optimum. Multiple-component spectrum regression, spectrum deconvolution and smoothing examples are used to illustrate the algorithm. The algorithm and a method for determining uncertainties in the parameters based on the Fisher information matrix are given and illustrated with three examples. An experimental example of spectrograph grating order compensation of a diode array solar spectroradiometer is given to illustrate the use of this technique in environmental analysis. The major advantages of the EM algorithm are found to be its stability, simplicity, conservation of data magnitude and guaranteed convergence.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/cem.1180050309
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    Gas-liquid two-phase flow in symmetrically dividing horizontal tubes (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 111-122 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The time-averaged void fraction, pressure drop and flow regime transition behavior of horizontal air-water two-phase flows is studied experimentally and numerically for 2-cm-inner-diameter tubes with various flow dividing junctions at its end. The time-average void and pressure drop behavior along the channel is simulated using a two fluid separated flow model. The results show that two-phase behavior (flow regime, void fraction, and pressure drop) is affected strongly by the presence of a flow division in the system. These effects extend far upstream of the junction for low-momentum flows and far downstream for high-momentum flows. Both numerical and experimental results show that there occurs a large increase in void just downstream of the junction owing to the halving of the fluid volume flow rates and the liquid deceleration.
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    URL: http://dx.doi.org/10.1002/aic.690370110
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    Fault diagnosis in complex chemical plants using artificial neural networks (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 137-141 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690370112
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    Masthead (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991) 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690370201
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    Influence of chemical and electrostatic gradients on diffusion in microemulsions (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 169-181 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Nonequilibrium diffusion behavior in nonionic and ionic surfactant microemulsion systems has been studied experimentally using the open-ended capillary method. Experimental results for these systems have been compared with a drop theory of diffusion for microemulsions under conditions where large concentration and electrostatic gradients exist. The results show good agreement in concentration profiles between theory and experiment for the microemulsion components - water, benzene, and phenol. Furthermore, under certain conditions the theory predicts that over a limited time interval phenol will diffuse from low-concentration regions to regions of higher concentration. This phenomenon has been observed.
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    Use of a second endothermic reaction to desensitize a tubular reactor (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 225-232 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Three parametric sensitivity criteria were examined for application to a pseudohomogeneous tubular reactor system, in which both methanol dehydration (exothermic) and methanol dissociation (endothermic) were catalyzed. The addition of the endothermic reaction was shown to lead to a desensitized reactor. It was illustrated, however, that the relative activities of the two catalysts should be somewhat similar to maintain the overall conversion of the resulting reactor for a given residence time.The three criteria investigated tended to disagree with one another more, as the system was made less sensitive by the addition of more endothermic catalyst. A potential application of the resulting nonsensitive reactor design would be in methanol-fueled vehicles.
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    Spray-to-bubbly transition for distillation systems containing two liquid phases (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 597-606 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The tray hydrodynamics were determined for a system containing water and kerosene as immiscible liquids. Plates with hole diameters ranging from 3.18 to 12.70 mm were used in a 44.5-cm2 perspex air-water-kerosene simulator. Experiments were also carried out in a 50-mm-ID column using different depths of oil and water mixtures to study the drop and bubble mechanisms. A spray-to-bubble transition occurred for the two liquid-phase system experiments. The liquid holdup at the transition increased directly with gas velocity and hole diameter, and decreased with increasing free area. At the same hole velocity, the presence of two liquid phases caused the transition to occur at different liquid holdups than for the single pure liquid. Two different modes of coalescence were observed in the small column work. New correlations have been proposed for the liquid holdup at the transition which allow for the presence of two liquid phases.
    Additional Material: 21 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690370413
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    Letters to the editor (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 791-799 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690370517
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    In transition (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 803-803 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690370603
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    Masthead (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991) 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690370701
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    Gas-solid flow in vertical tubes (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 1009-1018 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A computational study of fully-developed flow of gas-particle suspensions in vertical pipes was carried out, using the model proposed recently by Sinclair and Jackson (1989), to understand the predicted scale-up characteristics. It was shown that the model can capture the existence of steady-state multiplicity wherein different pressure gradients can be obtained for the same gas and solids fluxes. A pronounced and nonmonotonic variation of the pressure gradient required to achieve desired fluxes of solid and gas with tube diameter was predicted by the model, and this is explained on a physical basis. The computed results were compared with the experimental data. The model manifests an unsatisfactory degree of sensitivity to the inelasticity of the particle-particle collisions and the damping of particle-phase fluctuating motion by the gas.
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    Liquid saturation data in trickle beds operating under elevated pressure (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 1109-1112 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690370717
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    L-serine obtained by methanol addition in batch crystallization (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 1121-1128 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The solubility of L-serine in water was measured as a function of temperature, and the solubility in methanol-water solutions was determined as a function of temperature and methanol concentration. Solubility in aqueous solutions was found to be a linear function of temperature. Additionally, a statistical design of experiments was used to identify the kinetic variables that influence the purity of L-serine crystals recovered by batch crystallization. Agitation and the rate at which super-saturation was generated through cooling and methanol addition were found to influence the methanol content of the recovered crystals. The size of the recovered crystals also was found to depend on agitation and the rate at which methanol was added to the L-serine mother liquor.
    Additional Material: 9 Ill.
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    Emulsion layer model for wall heat transfer in a circulating fluidized bed (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 1139-1150 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An emulsion layer model is presented which predicts the thickness of a downward-moving emulsion layer along the wall of a circulating fluidized bed, the mean solids velocity, and the solids flux in the layer. Also presented is a heat transfer model which, in combination with the emulsion layer model, predicts the low-temperature data very well. An alternate slab model proposed for the radiative component in a high-temperature circulating fluidized bed agrees well with experimental data. The heat transfer predictions of the overall model for such operating parameters as solid circulation flux, suspension temperature, length of the heat transfer surface, superficial gas velocity, and mean particle size are in good agreement with the published data for long surfaces.
    Additional Material: 15 Ill.
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    Water and ethanol sorption phenomena on starch (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 1187-1195 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The sorption behavior of water and ethanol on starch material has been investigated in relation to the adsorptive separation of water from ethanol. The adsorption isotherms of water-starch, ethanol-starch and water-ethanol-starch were measured using a Cahn electrobalance. Careful examination of the many sorption isotherm models resulted in selection of Sircar's model and the potential theory to best represent the isotherm data of water-starch and ethanol-starch adsorption. Experimental results showed that ethanol as well as water can adsorb on starch. The adsorption rate of ethanol, however, is much slower than that of water. This suggests that the selective removal of water from ethanol vapor in a packed-bed adsorber is likely a rate-dependent, not an equilibrium-dependent, process.
    Additional Material: 7 Ill.
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    Influence of operating and physical variables on interfacial area determination (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 1196-1204 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of various operating and liquid-phase physical variables on interfacial area ab in cylindrical and spherical gas-liquid stirred contactors was studied using the sulfite method. Studied were stirring speed, sparger porosity, gas flow rate, liquid-phase temperature, surface tension, and pH.The results show that the influence of operating variables (gas flow rate Qg, stirring speed ω, and the average pore radius of the sparger used rp) on ab, for both types of contactors, can be given by the equation: \documentclass{article}\pagestyle{empty}\begin{document}$$ a_b = Q_g^{0.5} \left({\frac{{k_1 }}{{k_2 }} + \frac{{k_2 }}{{r_p^{1.5} }}\omega } \right) $$\end{document} Dependency of ab on surface tension observed was believed to be caused by a rising rate of bubble coalescence with increased surfactant concentration. The higher the surfactant concentration, the lower ab, tending to a limit that depends on both the type of surfactant and the average size of sparger pore used. Due to the measurement method used, solution pH and temperature were also observed to influence ab.
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    URL: http://dx.doi.org/10.1002/aic.690370809
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