Showing papers by "Missouri University of Science and Technology published in 1987"
TL;DR: An exact analytical expression for P(omega) of a metal is derived by using a nonresonant cavity to measure at ambient temperature the angle averaged absorptance spectra of gold, nickel, and lead in the 30-300-cm(-1) wave-number region.
Abstract: Measurements of the optical properties, and thus the optical constants, of metals at submillimeter wavelengths are almost nonexistent. We used a nonresonant cavity to measure at ambient temperature the angle averaged absorptance spectra P(ω) of gold, nickel, and lead in the 30–300-cm−1 wave-number region. The real part of the normalized surface impedance spectrum z(ω) = r(ω) + ix(ω) was determined from P(ω). The r(ω) spectrum was combined with previous measurements by others at higher frequencies, and Kramers-Kronig analyses of the resultant r(ω) spectra provided ∊(ω) = ∊1(ω) + i∊2(ω) and N(ω) = n(ω) + ik(ω) for gold and nickel in the 35–15,000-cm−1 region and for lead in the 15–15,000-cm−1 region. We also derived an exact analytical expression for P(ω) of a metal.
251 citations
TL;DR: The retrospection results indicated that both low- and high-knowledge writers intermixed planning, translating, and reviewing during all phases of composing, and the secondary task results showed that the degree of cognitive effort devoted to planning, translate, and review depended on the task.
Abstract: Conditions of low and high knowledge about the topic of a writing task were compared in terms of the time and cognitive effort allocated to writing processes These processes were planning ideas, translating ideas into text, and reviewing ideas and text during document composition Directed retrospection provided estimates of the time devoted to each process, and secondary task reaction times indexed the cognitive effort expended Topic knowledge was manipulated by selecting subjects in Experiment 1 and by selecting topics in Experiment 2 The retrospection results indicated that both low- and high-knowledge writers intermixed planning, translating, and reviewing during all phases of composing There was no evidence that low- and high-knowledge writers adopt different strategies for allocating processing time About 50% of writing time was devoted to translating throughout composition From early to later phases of composing, the percentage of time devoted to planning decreased and that devoted to reviewing increased The secondary task results showed that the degree of cognitive effort devoted to planning, translating, and reviewing depended on the task Also, the high-knowledge writers expended less effort overall than did the low-knowledge writers; there was no difference in allocation strategy across planning, translating, and reviewing
207 citations
TL;DR: The glass formation region in the yttria-alumina-silica system was investigated in this paper, where properties of glasses containing 25 to 55 wt pct Yttria were measured and the effect of the composition was determined.
Abstract: The glass formation region in the yttria-alumina-silica system was investigated. Properties of glasses containing 25 to 55 wt pct yttria were measured and the effect of the composition was determined. The density, refractive index, thermal-expansion coefficient, and microhardness increased with increasing yttria content. The dissolution rate in 1N HCl increased with increasing yttria content and temperature. These glasses were also found to have high electrical resistivity.
164 citations
119 citations
TL;DR: In this article, the structures of phosphourus oxynitride glasses have been determined using a combination of solid-state 31P, 15N, and 23Na nuclear magnetic resonance and Raman spectroscopies.
Abstract: The structures of phosphourus oxynitride glasses have been determined using a combination of solid-state 31P, 15N, and 23Na nuclear magnetic resonance and Raman spectroscopies. Raman spectra of model phosphazene compounds with different types of P–N bonding have been used to confirm spectral assignments. Results indicate that nitrogen replaces oxygen in the phosphrus atoms (via one double bond and one single bond) and as nitrogen bonded to three phosphorus atoms via three single bonds. The observed structural features are consistent with data which show that nitrogen influences the chemical durability, thermal expansion, and other properties of phosphate glasses by cross-linking ploymeric phosphate chain to gether in the glass network.
112 citations
TL;DR: In this paper, simple shearing of a block simple (nonpolar) and dipolar thermoviscoplastic materials is studied with the objectives of exploring the initiation and growth of, and the interaction among, adiabatic shear bands.
91 citations
TL;DR: In this paper, a model was developed to investigate the question of congressional influence by combining two attributes of representatives and constitutents that may lead to a predisposition of labor support.
Abstract: Labor PACs are used to explore the potential congressional influence of campaign contributions from special interest groups. PACs of organized labor are particularly useful for two reasons. First, a set of labor issues are defined each year by the AFL-CIO and so ad-hoc decisions about pertinent legislation are not made by the researcher. Secondly, there are measurable traits of representatives and constitutents that may lead to a predisposition of labor support. By combining these two attributes, a model is developed to investigate the question of congressional influence.
85 citations
01 Jan 1987-International Journal of Radiation Applications and Instrumentation. Part B. Nuclear Medicine and Biology
TL;DR: Glass microspheres 20-30 microns in diameter containing either 31P or 89Y that can be activated by neutron bombardment to 32P or 90Y respectively, have been produced for intra-arterial radiotherapy of liver tumors and are entering limited human clinical trials.
82 citations
TL;DR: In this article, a study was conducted to investigate the stress ratio effect on cyclic debond growth behavior in adhesively bonded composite joints, which consisted of graphite/epoxy adherends bonded with a toughened epoxy adhesive.
80 citations
TL;DR: In this paper, the authors consider an experimental situation where prior knowledge indicates that all of the treatments are at least as effective as the control and the problem is to determine if any are significantly better than the control.
Abstract: A problem frequently encountered in the practice of statistics is the comparison of several treatments with a control or standard. We consider an experimental situation where prior knowledge indicates that all of the treatments are at least as effective as the control and the problem is to determine if any are significantly better than the control. A number of statistical procedures have been proposed for this situation, of which the best known is Dunnett's (1955) multiple comparison procedure. Dunnett's test rejects equality of the treatments and the control for a large value of the maximum contrast of the data vector with several vectors that are located “symmetrically” within the alternative region. We study a large class of such tests, which includes Dunnett's test as a particular case. One of these tests, which is based on the maximum contrast of the data vector with several orthogonal vectors, is very easy to implement and has an uncomplicated, good, and fairly uniform power function over t...
75 citations
TL;DR: In this article, the loading rate effect on delamination fracture initiation toughness of a thermoplastic composite was investigated, and the interlaminar fracture toughness was found to decrease with increasing loading rate, and this decrease was more than one hundred percent over the five decades of loading rate employed.
Abstract: A study was undertaken to investigate the loading rate effect on delamination fracture initiation toughness of a thermoplastic composite. For this purpose, double cantilever beam specimens of graphite/PEEK were tested in a displacement controlled mode using an Instron tensile test machine. Specimens were loaded at various crosshead speeds ranging from 0.05 cm/min to 100 cm/min. The interlaminar fracture toughness was found to decrease with increasing loading rate, and this decrease was more than one hundred percent over the five decades of loading rate employed.
TL;DR: Classical trajectory Monte Carlo calculations have been used to elucidate the collision mechanisms responsible for the differences in the single- and double-ionization cross sections of He atoms by protons and antiprotons in the energy range from 250 to 1000 keV.
Abstract: Classical trajectory Monte Carlo calculations have been used to elucidate the collision mechanisms responsible for the differences in the single- and double-ionization cross sections of He atoms by protons and antiprotons in the energy range from 250 to 1000 keV. The calculations employed the Bohr helium-atom model which includes the 1/r/sub 12/ electron-electron interaction. The unexpected large observed difference (Andersen et al., Phys. Rev. Lett. 57, 2149 (1986)) in the ratio R of double to single ionization for proton and antiproton collisions is reproduced by the calculations. The calculations indicate that the antiproton double-ionization cross section is larger than that for protons because of two effects. The first effect is that the antiproton can push one electron into the other from larger impact parameters than for protons which must be between the nucleus and the first electron in order to pull it into a trajectory which collides with the second electron. The most important effect, however, is that at small impact parameters the antiproton screens the helium nucleus causing a Coulomb explosion while the proton increases the binding of the two electrons. The calculations also show a component of the difference in the ratio R at low energies (Eless thanmore » or equal to500 keV) is due to the single-ionization cross sections with protons predicted to have a larger cross section than antiprotons (36% difference at 250 keV).« less
TL;DR: In this paper, a general finite element formulation for analysis of the sound field in a uniform flow duct with a bulk-reacting porous liner is given, and numerical results on rectangular ducts lined on all four sides are shown, and some of the lower order acoustic modes are described.
TL;DR: In this paper, the authors present cognitive strategies that may lessen a writer's work load by preparing a written outline during pre-writing and composing a rough rather than a polished first draft.
Abstract: Preparing a written outline during prewriting and composing a rough rather than a polished first draft are cognitive strategies that may lessen a writer's work load. The present laboratory and fiel...
TL;DR: In this paper, the authors extended the formal linear diffusion theory employed in an earlier paper to binary mixtures and used the simulation data to analyse the data and showed that it can be used to quantitatively predict the diffusion fluxes of small, nonadsorbing solutes as well as macromolecular solutes in micropores as long as the sum of the solute and solvent particle sizes is less than the size of the pore.
Abstract: Grand canonical ensemble Monte Carlo and molecular dynamics simulations of partitioning and diffusion of rigid sphere fluids and mixtures in cylindrical pores have been carried out for a wide range of pore sizes. The formal linear diffusion theory employed in an earlier paper is extended to binary mixtures and is used to analyse the simulation data. The results obtained show that continuum-mechanical theory may be used to quantitatively predict the diffusion fluxes of small, nonadsorbing solutes as well as macromolecular solutes in micropores as long as the sum of the solute and solvent particle sizes is less than the size of the pore. In addition, the existence of viscous slip for dense fluids observed earlier is confirmed, and it is shown that selective partitioning of solutes in simple fluid mixtures can lead to solvent diffusion barriers in very small pores.
TL;DR: It is shown that the ML estimator of d(t) can be implemented in any of four canonical forms which, in general, are time-varying systems, and reduce to a generalized cross correlator for the special case treated in [1].
Abstract: This paper presents, for the first time, the exact theoretical solution to the problem of maximum-likelihood (ML) estimation of time-varying delay d(t) between a random signal s(t) received at one point in the presence of uncorrelated noise, and the time-delayed, scaled version αs(t - d(t)) of that signal received at another point in the presence of uncorrelated noise The signal is modeled as a sample function of a nonstationary Gaussian random process and the observation interval is arbitrary The analysis of this paper represents a generalization of that of Knapp and Carter [1], who derived the ML estimator for the case that the delay is constant, d(t) = d 0 , the signal process is stationary, and the received processes are observed over the infinite interval (-∞, +∞) We show that the ML estimator of d(t) can be implemented in any of four canonical forms which, in general, are time-varying systems We also show that our results reduce to a generalized cross correlator for the special case treated in [1]
TL;DR: In this article, the preparation of Na-P-O-N glasses was investigated in dry ammonia, forming gas and 90% N2+ 10% CO atmospheres, and significant nitrogen dissolution, up to 13 wt% in a NaPO3 melt, occurred only in ammonia.
Abstract: The preparation of sodium phosphate oxynitride (Na-P-O-N) glasses was investigated in dry ammonia, forming gas and 90% N2+ 10% CO atmospheres. Significant nitrogen dissolution, up to 13 wt% in a NaPO3 melt, occurred only in ammonia. The kinetics of nitrogen dissolution was studied as a function of remelting time (1 to 96 h) and temperature (660° to 760°C). Higher temperature accelerates nitrogen dissolution, but the temperature should not exceed 760°C. Great improvement in chemical durability occurs with nitrogen dissolution in a NaPO3 melt. Other property changes reported include softening temperature, thermal expansion coefficient, refractive index, microhardness, etc. A double chain structure model is proposed for the Na-P-O-N glass.
TL;DR: In this paper, a single modified buoyancy parameter and a single curvature parameter are employed in the analysis such that a smooth transition from pure forced convection to pure free convection can be accomplished.
Abstract: Mixed convection along vertical cylinders and needles with uniform surface heat flux is investigated for the entire mixed convection regime. A single modified buoyancy parameter {chi} and a single curvature parameter {Lambda} are employed in the analysis such that a smooth transition from pure forced convection ({chi} = 1) to pure free convection ({chi} = 0) can be accomplished. For large values of the curvature parameter and/or Prandtl number, the governing transformed equations become stiff. Thus, a numerically stable finite-difference method is employed in the numerical solution in conjunction with the cubic spline interpolation scheme to overcome the difficulties that arise from the stiffness of the equations. Local Nusselt numbers are presented for 0.1 {le} Pr {le} 100 that cover 0 {le} {chi} {le} 1 ({infinity} {ge} {Omega}{sub x} {ge} 0) and 0 {le} {Lambda} {le} 50. For needles ({Lambda} {ge} 5), the local Nusselt numbers (Nu{sub x}/Re{sub x}{sup 1/2} + Gr{sub x}{sup 1/5}*) are found to be nearly independent of the buoyancy parameter {chi}. Correlation equations for the local Nusselt numbers are also presented.
TL;DR: In this paper, a Lyot filter and a thin etalon were used to tune the LNA laser output to the resonance transition of helium-4 (23S1-23P1) at 1.083 μm.
TL;DR: The chemical durability of PON glasses is directly related to their nitrogen content as mentioned in this paper, which improves the durability of phosphate glasses by cross-linking the polymeric phosphate chains in the network structure.
Abstract: Phosphorus oxynitride (PON) glasses, prepared by remelting phosphate glasses in anhydrous ammonia vapor, are more resistant to dissolution in water and corrosion in humid environments than the parent phosphate glasses. The chemical durability of PON glasses is directly related to their nitrogen content. Solution analyses, pH stat titrations, and hydrogen depth profiles suggest that nitrogen improves the durability of phosphate glasses by cross-linking the polymeric phosphate chains in the network structure.
TL;DR: In this article, the authors studied the thermomechanical problem involving simple shearing of a finite slab made of an isotropic and viscoplastic material with the objective of finding the effect of the strain hardening parameter, strain-rate hardening parameters, thermal softening coefficient and thermal conductivity on the initiation and growth of adiabatic shear bands.
TL;DR: In this article, a high-order plate bending displacement field is developed for the analysis of layered composite plates, where the parabolic distribution of the transverse shear strains is considered and a mixed finite element model is introduced from the equation.
01 Mar 1987
TL;DR: In this article, the conductivity measurements on a microemulsion system were interpreted in terms of percolation and effective medium theories, and the ratio of hexylamine to sodium dodecyl sulfate in the micro-emulsion droplet surfaces can be deduced.
Abstract: Conductivity measurements on this system are interpreted in terms of the percolation and effective medium theories. From this interpretation, the ratio of hexylamine to sodium dodecyl sulfate in the microemulsion droplet surfaces can be deduced. Following that determination it is possible to obtain approximate values for the radius of the water pools and the number and surface area of droplets per unit volume of the microemulsion system.
TL;DR: In this paper, a parallel-fibre model is presented to describe sound propagation in rigid-framed porous materials with internal mean fluid flow, and the results are compared to predicted data both with and without mean flow and generally good aggreement is noted.
TL;DR: In this paper, the authors present a new econometric and benefit/cost estimate for the automotive safety inspection, which is based on the benefits and benefits of the inspection process.
Abstract: (1987). Automobile safety inspection: new econometric and benefit/cost estimates. Applied Economics: Vol. 19, No. 6, pp. 763-771.
01 Mar 1987
TL;DR: In this article, a simple version of thermo/viscoplasticity is used to model the formation of adiabatic shear bands in high rate deformation of solids.
Abstract: A simple version of thermo/viscoplasticity is used to model the formation of adiabatic shear bands in high rate deformation of solids. The one dimensional shearing deformation of a finite slab is considered. Equations are formulated and numerical solutions are found for dipolar plastic materials. These solutions are contrasted and compared with previous solutions for simple materials.
TL;DR: In this article, a variety of crosslinked phenol-, or derivatized phenol-formaldehyde polymers have been synthesized, and the derivatives were copolymerized with phenol and formaldehyde using sulfuric acid as catalyst to yield novolak-type prepolymers, which were then cured with hexamethylenetetetramine.
Abstract: A variety of crosslinked phenol-, or derivatized phenol-formaldehyde polymers have been synthesized. The phenol derivatives included o- and p-cresol, p-nonylphenol, m-pentadecylphenol, and raw and distilled cashew nutshell liquid. The derivatives were copolymerized with phenol and formaldehyde using sulfuric acid as catalyst to yield novolak-type prepolymers, which were then cured with hexamethylenetetramine. Thermogravimetric analysis was used to evaluate the thermal stability of the cured resins. It was found that the thermal stability of the resins decreased with increasing amounts of cashew nutshell liquid, with distilled cashew resins being slightly more thermally stable than raw cashew resins. The thermal stability of resins containing substituted phenols with alkyl chains was observed to increase from n-pentadecylphenol to cresol to phenol. The trend in thermal stability of the resins may be explained on the basis of alkyl groups being less thermally stable than aromatic rings. The amount of hexamethylenetetramine used to cure the prepolymers also influences the thermal stability of the resins. It appears that a level of 10 to 15% hexamethylenetetramine maximizes the thermal stability of the resin.
TL;DR: In this paper, under certain assumptions concerning the disconjugacy or disfocality of the solution y(x) of (1), the authors considered the differentiability of solutions of (x) with respect to boundary conditions (both boundary values and boundary points) and proved an analogue of Peano's theorem of Hartman's text.