Showing papers by "Michigan Technological University published in 1986"
TL;DR: In this article, a new framework for considering the localization of deformation and illustrate it for the case of hyperelastic materials is proposed, where strain-induced localized deformation patterns are accounted for by adding a second deformation gradient-dependent term to the expression for the strain energy density, leading to equilibrium equations which remain always elliptic.
Abstract: By utilizing methods recently developed in the theory of fluid interfaces, we provide a new framework for considering the localization of deformation and illustrate it for the case of hyperelastic materials. The approach overcomes one of the major shortcomings in constitutive equations for solids admitting localization of deformation at finite strains, i.e. their inability to provide physically acceptable solutions to boundary value problems in the post-localization range due to loss of ellipticity of the governing equations. Specifically, strain-induced localized deformation patterns are accounted for by adding a second deformation gradient-dependent term to the expression for the strain energy density. The modified strain energy function leads to equilibrium equations which remain always elliptic. Explicit solutions of these equations can be found for certain classes of deformations. They suggest not only the direction but also the width of the deformation bands providing for the first time a predictive unifying method for the study of pre- and post-localization behavior. The results derived here are a three-dimensional extension of certain one-dimensional findings reported earlier by the second author for the problem of simple shear.
361 citations
TL;DR: Values of the fundamental band gap as a function of Mn molar fraction x and temperature are determined and appear to be related to the presence of s-d and p-d interactions.
Abstract: Photoluminescence and reflectivity measurements have been carried out on ${\mathrm{Zn}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Mn}}_{\mathrm{x}}$Se solid solutions in the complete range of crystal compositions, 0\ensuremath{\le}x\ensuremath{\le}0.55. The features of the photoluminescence and reflectivity data near the band edge enabled us to determine values of the fundamental band gap as a function of Mn molar fraction x and temperature (8 K\ensuremath{\le}T\ensuremath{\le}300 K). The energy gap in crystals with compositions in the vicinity of the zinc-blende--wurtzite structural transition (0.2\ensuremath{\lesssim}x\ensuremath{\lesssim}0.3) exhibited a scatter of values, probably associated with the presence of various polytypes (as evidenced by transmission-electron-microscopy measurements). The dependence of ${E}_{g}$ on x is anomalous for 0\ensuremath{\le}x\ensuremath{\le}0.2, showing a minimum in the ${E}_{g}$ vs x curve. A simple model (in terms of second-order perturbation theory in s-d and p-d interactions) relates this minimum to a maximum observed in the magnetic susceptibility as a function of x. For samples with x\ensuremath{\gtrsim}0.35, the ${E}_{g}$ dependence on T shows an onset of an additional blue shift as the temperature is lowered below \ensuremath{\sim}150 K. This onset, though not reproduced by our simple calculation, appears to be also related to the presence of s-d and p-d interactions.
296 citations
TL;DR: The influence of porosity on the deformation and fracture behavior of two alloys, powder-fabricated Ti and Ti-6Al-4V, with differing levels of matrix strain hardening has been examined both experimentally and analytically.
144 citations
TL;DR: In this article, the formation and stability of dislocation patterns are interpreted on the basis of instabilities occurring in partial differential equations modelling the dynamics of dislocations species under certain circumstances, these equations are shown to be a coupled system of the diffusion reaction type for the densities of immobile and mobile dislocation populations.
109 citations
TL;DR: In this paper, the crumpling of thin-walled frusta, under axial compression, in the ‘concertina’ mode is studied, where the energy expended in bending at the plastic hinges and in stretching the metal between the hinges is minimized for the total decrease in height due to collapse.
106 citations
TL;DR: In this article, airborne correlation spectrometry (COSPEC) was used to measure the rate of SO2 emission at White Island on three dates, i.e., November 1983, 1230 ± 300 t/d; November 1984, 320 ± 120 t/D; and January 1985, 350 ± 150 t/t (t = metric tons).
Abstract: Airborne correlation spectrometry (COSPEC) was used to measure the rate of SO2 emission at White Island on three dates, i.e., November 1983, 1230 ± 300 t/d; November 1984, 320 ± 120 t/d; and January 1985, 350 ± 150 t/d (t = metric tons). The lower emission rates are likely to reflect the long-term emission rates, whereas the November 1983 rate probably reflects conditions prior to the eruption of December 1983. The particle flux in the White Island plume, as determined with a quartz crystal microbalance/cascade in November 1983, was 1.3 t/d, unusually low for volcanic plumes. The observed plume particles, as shown from scanning electron microscopy, include halite, native sulfur, and silicates and are broadly similar to other volcanic plumes. Gas analyses from high-temperature volcanic fumaroles collected from June 1982 through November 1984 werde used together with the COSPEC data to estimate the flux of other gas species from White Island. The rates estimated are indicative of the long-term volcanic emission, i.e., 8000–9000 t/d H2O, 900–1000 t/d CO2, 70–80 t/d HCl, 1.5–2 t/d HF, and about 0.2 t/d NH3. The long-term thermal power output at White Island is estimated at about 400 MW.
95 citations
TL;DR: Plagioclase and biotite phenocrysts in ignimbrites erupted from the Toba caldera, Sumatra, show microstructures and textures indicative of shock stress levels higher than 10 GPa as discussed by the authors.
Abstract: Plagioclase and biotite phenocrysts in ignimbrites erupted from the Toba caldera, Sumatra, show microstructures and textures indicative of shock stress levels higher than 10 GPa. Strong dynamic deformation has resulted in intense kinking in biotite and, with increasing shock intensity, the development of plagioclase of planar features, shock mosaicism, incipient recrystallization, and possible partial melting. Microstructures in quartz indicative of strong shock deformation are rare, however, and many shock lamellae, if formed, may have healed during post-shock residence in the hot ignimbrite; they might be preserved in ash falls. Peak shock stresses from explosive silicic volcanism and other endogenous processes may be high and if so would obviate the need for extraterrestrial impacts to produce all dynamically deformed structures, possibly including shock features observed near the Cretaceous/Tertiary boundary. 38 references, 3 figures.
74 citations
TL;DR: The use of writing in the mathematics curriculum has recently received increased attention, due in large part to the recommendations of the National Council of Teachers of Mathematics (N.C.T.M). as discussed by the authors has indicated that the ability to express mathematical observations in writing can serve as a positive force in one's continued development as a mathematics student.
Abstract: The use of writing in the mathematics curriculum has recently received increased attention, due in large part to the recommendations of the National Council of Teachers of Mathematics (N.C.T.M.). Research has indicated that the ability to express mathematical observations in writing can serve as a positive force in one’s continued development as a mathematics student. The implementation of writing in the mathematics class can utilize several approaches.
67 citations
TL;DR: Inextensional collapse mechanisms for axial crumpling of thin-walled circular cones and frusta (truncated circular cones) are presented in this paper, where shortening of the (thin) shell height is achieved by folding in a non-symmetric diamond mode about stationary circumferential and inclined plastic hinges; collapse proceeds progressively from the narrower end of the conical shell during the passage of a travelling hinge.
65 citations
TL;DR: In this paper, a new analysis of idealized class E frequency multipliers similar to that used by Raab in his description of class E amplifiers, in that the equations describing multiplier operation are obtained from Fourier series methods and the assumption of an infinite output network Q, are used to determine 1) optimum operation (maximum power output capability at 100-percent efficiency) at any harmonic, and 2) design equations that yield the requisite component values for optimum operation.
Abstract: The theoretical performance of class E frequency multipliers described by Kozyrev bears little resemblance to the observed performance of such circuits. This paper provides a new analysis of idealized class E frequency multipliers similar to that used by Raab in his description of class E amplifiers, in that the equations describing multiplier operation are obtained from Fourier series methods and the assumption of an infinite output network Q . The equations so obtained are used to determine 1) optimum operation (maximum power output capability at 100-percent efficiency) at any harmonic, and 2) design equations that yield the requisite component values for optimum operation. The equations provide an easily used design method for optimum class E multipliers but allow the implementation of nonoptimum multipliers to suit any design objective. Class E multipliers with moderate values of output network Q were constructed and tested. The measured performance of these experimental circuits shows excellent agreement to the theoretical performance predicted by the equations.
60 citations
TL;DR: Sodium appeared to be the element attracting moose to licks where they ingest copious amounts of water, and observed sodium ingestion rates at licks indicate that licks provide a more concentrated source of sodium compared to aquatic plants.
Abstract: Natural mineral licks and their use by moose (Alces alces) on Isle Royale National Park, Michigan, were studied during 1982–85. The distribution of known licks suggested that they occurred in association with glacial debris, primarily in the western portions of the island. Moose utilized mineral springs extensively during the spring-summer period, and at least 5 licks were used year-round. During summer, a pronounced diel pattern of moose visitation was apparent, with peak use occurring between 0400–0800 h. Although daytime lick use declined by late June, morning and evening use continued to be relatively high throughout the study period. Peak lick use coincided with leaf-emergence in spring. Moose continued to utilize mineral licks despite the availability of ponds containing aquatic plants. Sodium appeared to be the element attracting moose to licks where they ingest copious amounts of water. Observed sodium ingestion rates (0.35 g/min) at licks indicate that licks provide a more concentrated source of sodium compared to aquatic plants (0.023 g/min). Based on the data presented, we reject the conclusions of earlier workers that aquatic plants constitute the only significant source of sodium for Isle Royale moose.
Patent•
30 Jun 1986TL;DR: In this paper, a loosely fitted mat of wood flakes is formed by depositing a first plurality of layers of wood flake onto a supporting surface with a flake aligner provided for causing alignment of those flakes which will form legs of the pallet.
Abstract: A method for molding articles such as pallets from flake-like wood particles mixed with binder, the pallets housing a deck and integral molding legs. A loosely fitted mat of wood flakes is formed by depositing a first plurality of layers of wood flakes onto a supporting surface with a flake aligners provided for causing alignment of those flakes which will form legs of the pallet. A second plurality of layers are formed with a flake aligner provided for causing alignment of flakes which will form the legs of the pallet and in a direction transverse to the direction of alignment of the flakes of the first layers.
TL;DR: In this article, the major and trace element data can be obtained by automated x-ray fluorescence (XRF) analysis of pressed rock powder pellets, and the precision of the major element results are generally better than ± 1% of the amount determined, whereas the trace element precisions are generally less than 5% except when the value determined is close to the detection limit.
Abstract: Rapid and high-quality major and trace element data can be obtained by automated x-ray fluorescence (XRF) analysis of pressed rock powder pellets. The sample preparation procedure is simple, quick and can be done well with minimal supervision. Analysis of the rock pellet for 22 elements requires about 1 h of machine time. The system is calibrated by use of multiple international rock standards and employs a ratio standard for all measurements. Most calibrations are simple linear fits between intensity and concentration. The precision of the major element results are generally better than ±1% of the amount determined, whereas the trace element precisions are generally less than 5%, except when the value determined is close to the detection limit. Accuracies are comparable to those of other published XRF rock analysis procedures.
TL;DR: In this paper, an inextensional collapse mechanism is used to describe a non-symmetrical diamond mode shell folding which takes into account the concept of stationary circumferential and inclinded travelling hinges.
TL;DR: In this paper, theoremes d'existence et d'unicite for des problemes de Cauchy correspondant aux equations abstraites de la forme d(B(t)u(t))/dt+A(t,u(T))=f(t), ou B(t ) est une famille dependante du temps d'operateurs lineaires
Abstract: On presente des theoremes d'existence et d'unicite pour des problemes de Cauchy correspondant aux equations abstraites de la forme d(B(t)u(t))/dt+A(t,u(t))=f(t), ou B(t) est une famille dependante du temps d'operateurs lineaires
TL;DR: The results suggest that S. setonii produces a cytochrome P-450 that is involved in the demethylation of veratrole and guaiacol to catechol, which is then catabolized by the beta-ketoadipate pathway.
Abstract: The actinomycete Streptomyces setonii 75Vi2 demethylates vanillic acid and guaiacol to protocatechuic acid and catechol, respectively, and then metabolizes the products by the β-ketoadipate pathway. UV spectroscopy showed that this strain could also metabolize veratrole (1,2-dimethoxybenzene). When grown in veratrole-containing media supplemented with 2,2′-dipyridyl to inhibit cleavage of the aromatic ring, S. setonii accumulated catechol, which was detected by both liquid chromatography and gas chromatography. Reduced cell extracts from veratrole-grown cultures, but not sodium succinate-grown cultures, produced a carbon monoxide difference spectrum with a peak at 450 nm that indicated the presence of soluble cytochrome P-450. Addition of veratrole or guaiacol to oxidized cell extracts from veratrole-grown cultures produced difference spectra that indicated that these compounds were substrates for cytochrome P-450. My results suggest that S. setonii produces a cytochrome P-450 that is involved in the demethylation of veratrole and guaiacol to catechol, which is then catabolized by the β-ketoadipate pathway.
TL;DR: This article used an airborne quartz crystal microbalance cascade impactor instrument together with a correlation spectrometer to determine the flux of particles and their size distribution in the Erebus plume.
Abstract: Use of an airborne quartz crystal microbalance cascade impactor instrument together with a correlation spectrometer has allowed the flux of particles and their size distribution to be determined at Mount Erebus. The plume contributes 21±3 metric tomnes/day of aerosol particles to the Antarctic upper troposphere. The aerosol particles consist of larger (5–25 μm) particles of elemental sulfur and silica, a middle sized group of iron oxides and smaller particles (less than 1 μm) of complex liquids. Unlike many volcanic plumes, the Erebus plume has only a small amount of sulfate particles. The concentrations of particles in the Erebus plumes was 70–370 μm/m3. Limited sampling of the Antarctic atmosphere at 8 km altitude but hundreds of km away from Erebus obtained a few large particles of sulfur and silicates, suggesting a similarity with the Erebus plume. The fallout of these particles occurs slowly over a broad area of the Antarctic continent.
TL;DR: The electrophoretic properties of purified corn and squash NADH:nitrate reductases in both native and denatured states were shown to be similar using western blotting with mouse ascitic fluid, and the detection of proteolytic degradation products usingWestern blotting was inconsistent and remains to be established.
Abstract: NADH:nitrate reductase was extracted from corn leaves (Zea mays L. W64A × W182E) and purified on blue Sepharose. After the nitrate reductase was further purified by polyacrylamide gel electrophoresis, it was used to immunize mice and a rabbit. Western blots of crude leaf extracts were used to demonstrate monospecificity of the mouse ascitic fluids and the rabbit antiserum. The electrophoretic properties of purified corn and squash NADH:nitrate reductases in both native and denatured states were shown to be similar using western blotting with mouse ascitic fluid. The corn leaf enzyme has a 115,000 polypeptide subunit like that of squash. Western blots could detect 3 to 10 nanograms of nitrate reductase protein. But the detection of proteolytic degradation products using western blotting was inconsistent and remains to be established. An enzyme-linked immunosorbent assay (ELISA) was developed for quantifying nitrate reductase protein in the crude extracts of corn leaves. Using a standard curve based on nitrate reductase activity, the ELISA for corn nitrate reductase could detect 0.5 to 10 nanograms of nitrate reductase protein and was adequately sensitive for quantitative analysis of nitrate reductase in crude extracts of leaves even when activity levels were very low. When the ELISA was used to compare the nitrate reductase protein content of corn roots and leaves, these tissues were estimated to contain 0.24 to 0.5 and 4 to 5 micrograms nitrate reductase protein/gram root and leaf, respectively.
01 Mar 1986
TL;DR: In this paper, the effect of exhaust gas recirculation (EGR) on engine wear and lubricating oil degradation in a heavy duty diesel engine using a newly developed methodology that uses analytical ferrography in conjunction with short term tests.
Abstract: A study was undertaken to investigate the effect of exhaust gas recirculation (EGR) on engine wear and lubricating oil degradation in a heavy duty diesel engine using a newly developed methodology that uses analytical ferrography in conjunction with short term tests. Laboratory engine testing was carried out on a Cummins NTC-300 Big Cam II diesel engine at rated speed (1800 RPM) and 75% rated load with EGR rates of 0, 5, and 15% using a SAE 15W40 CD/SF/EO-K oil. Dynamometer engine testing involved collecting oil samples from the engine sump at specified time intervals through each engine test. These oil samples were analyzed using a number of different oil analysis techniques that provide information on the metal wear debris and also on the lubricating oil properties. The results from these oil analysis techniques are the basis of determining the effect of EGR on engine wear and lubricating oil degradation, rather than an actual engine tear down between engine tests.
TL;DR: In this article, the extent to which job satisfaction and several of its correlates influence levels of reported absenteeism in a sample of American workers was investigated, and the regression of absences on job satisfaction was performed.
Abstract: This research estimates the extent to which job satisfaction and several of its correlates influence levels of reported absenteeism in a sample of American workers. The regression of absences on ov...
TL;DR: In this article, the effect of changing the content of Ta on the gamma/gamma-prime carbide microstructure was investigated in two crystalline nickel-base superalloys.
Abstract: The effect of changing the content of Ta on the gamma/gamma-prime carbide microstructure was investigated in two crystalline nickel-base superalloys: conventionally cast B-1900 + Hf, and both conventionally cast and directionally solidified MAR-M247. The changes occurring in the microstructure effects were similar in both alloys. The gamma-prime and carbide volume fractions increased linearly with Ta additions, while the gamma-prime phase compositions did not change. Bulk Ta additions increased the levels of Cr and Co (in addition to that of Ta) of the gamma phase, a result of the approximately constant partitioning ratios for these two elements. The addition of Ta led to a partial replacement of Hf in the MC carbides. In addition, Cr-rich M(23)C(6) carbides formed as a result of MC carbide decomposition during heat treatment.
TL;DR: In this paper, the authors consider the motion and interaction of positive and negative mobile dislocations and derive an expression for their effective diffusivity, and show how these effects together with secondary slip activity may trigger the formation of walls in different directions in analogy with observations of labyrinth structures.
TL;DR: In this paper, a method for optimizing the field stress on HV insulators by modifying their profile, seeking a uniform distribution of the tangential field along the insulator surface, results in an increase of the onset voltage for surface flashover and in a significant saving of the space of the HV installation.
Abstract: A method is described for optimizing the field stress on HV insulators by modifying their profile, seeking a uniform distribution of the tangential field along the insulator surface. This results in an increase of the onset voltage for surface flashover and in a significant saving of the space of the HV installation. The optimization process was achieved by an algorithm developed for calculating the tangential field component and mathematical expressions of the profile to be corrected through an iterative procedure. The algorithm was based on a modified charge simulation technique to satisfy a better matching of the boundary conditions to the electrode and insulator surfaces involved in the HV installation. The algorithm is expanded to study the effect of contamination on the tangential field distribution. It is found that the higher the conductivity of the contamination layer, the higher is the field uniformity along the insulator surface.
TL;DR: In this paper, a mathematical model to calculate the trap binding energy and trap density is suggested considering the theories of hydrogen trapping and hydrogen retrapping, which indicates that the Al2O3/lattice interface acts as an irreversible trapping site for hydrogen.
Abstract: A mathematical model to calculate the trap binding energy and trap density is suggested considering the theories of hydrogen trapping and hydrogen retrapping. When iron containing 2.0 wt pct Al2O3 is heated with a uniform heating rate of 3 K-min-1, a hydrogen peak is observed at 853 K in the evolution ratevs temperature plot. This is due to hydrogen evolution from the Al2O3/lattice interface. The trap activation energy and trap binding energy of hydrogen at the Al2O3/lattice interface are estimated as 79 kJ ⋅ mol-1 and 71.4 kJ ⋅ mol-1, respectively, fitting experimental data to the model. This indicates that the Al2O3/lattice interface acts as an irreversible trapping site for hydrogen. By combining the trap binding energy and trap activation energy, the energy level of hydrogen around the Al2O3/lattice interface is suggested. The saddle point energy of hydrogen at Al2O3/lattice interface, 7.56 kJ ⋅ mol-1 is nearly equivalent to the activation energy for hydrogen diffusion through a normal lattice, 6.9 kJ ⋅ mol-1.
TL;DR: The predominant 4-desmethylsterols from the leaves of 12 species in 11 genera of the family Caryophyllaceae are 24-ethyl-Δ7-sterols, with spinasterol at more than 60% of the desmethylsterol in the latter six species.
Abstract: The predominant 4-desmethylsterols from the leaves of 12 species in 11 genera of the family Caryophyllaceae are 24-ethyl-Δ7-sterols. In eight species,Scleranthus annus L.,Paronychia virginica Spreng.,Lychnis alba Mill.,Silene cucubalus Wibel,Dianthus armeria L.,Gypsophilia paniculata L.,Saponaria officinales L. andMyosoton aquaticum (L.) Moench, the major sterols are spinasterol (24α-ethylcholesta-7,22E-dien-3β-ol) and 22-dihydrospinasterol (24α-ethylcholest-7-en-3β-ol), with spinasterol at more than 60% of the desmethylsterol in the latter six species. Both 24α-and 24β-ethyl-Δ7-sterols are present in two species,Minuartia caroliniana Walt. andSpergula arvensis L., which possess 24β-ethylcholesta-7,25(27)-dien-3β-ol and 24β-ethylcholesta-7,22E,25(27)-trien-3β-ol as well as spinasterol and 22-dihydrospinasterol.Cerastium arvense L.,C. vulgatum L. andArenaria serpyllifolia L. possess 24-alkyl-Δ5 and Δ7-sterols. These three species synthesize sitosterol (24α-ethylcholest-5-en-3β-ol), 24ζ-methylcholest-5-en-3β-ol, spinasterol, 22-dihydrospinasterol and the stanols, sitostanol (24α-ethyl-5α-cholestan-3β-ol) and 24ζ-methyl-5α-cholestan-3β-ol. Avenasterol (24-ethylcholesta-7,24(28)Z-dien-3β-ol) was also isolated from five species. Sterol biosynthetic capability may be a useful characteristic in examining the taxonomic relatedness of plants in the Caryophyllaceae.
01 Nov 1986
TL;DR: The application of mathematical models in the design and evaluation of lake restoration programs must include due consideration of three basic concepts of model development; 1) that the model framework is appropriately matched to the intended management use, 2) selection of the proper degree of model complexity is fundamental to the achievement of model credibility and 3) field and laboratory studies must be designed and interpreted with the aid of the model to insure development of a comprehensive, integrated tool as discussed by the authors.
Abstract: Application of mathematical models in the design and evaluation of lake restoration programmes must include due consideration of three basic concepts of model development; 1) that the model framework is appropriately matched to the intended management use, 2) that selection of the proper degree of model complexity is fundamental to the achievement of model credibility and 3) that field and laboratory studies must be designed and interpreted with the aid of the model to insure development of a comprehensive, integrated tool.
TL;DR: In this paper, the effects of Mo and Ti additions on the yield strength and rate of work hardening for cast alloys near Fe3Al were examined and significant improvements in high temperature compressive properties on alloying have been related to increases in the DO3→B2 transition temperature and associated changes in the nature of the dislocations involved in the deformation processes.
Abstract: Hot compression testing has been used to examine the effects of Mo and Ti additions on the yield strength and rate of work hardening for cast alloys near Fe3Al. A few powder processed materials have also been studied. Significant improvements in high temperature compressive properties on alloying have been related to increases in the DO3→B2 transition temperature and the associated changes in the nature of the dislocations involved in the deformation processes.
TL;DR: A complex caliche profile and numerous widespread zones of carbonate cement occur in a thick sequence of fluvial siliciclastic sandstones and conglomerates that were deposited in the Lake Superior basin during and after continental basaltic volcanism as discussed by the authors.
TL;DR: In this paper, an algorithme pour calculer inf θ ou θ(k,l) = k+bl+c/dk+el+f, a,...,f etant des nombres reels, (k, l) une paire d'exposants, l'infinum etant pris sur tous les produits par les processus A et B
Abstract: On presente un algorithme pour calculer inf θ ou θ(k,l)=ak+bl+c/dk+el+f, a,...,f etant des nombres reels, (k, l) une paire d'exposants, l'infinum etant pris sur tous les (k, l) produits par les processus A et B