Showing papers by "Michigan Technological University published in 1973"

Studies of volcanic ash from two recent Central American eruptions

Abstract: The 1971 eruptions of Cerro Negro volcano in Nicaragua and Fuego volcano in Guatemala produced ash blankets with minimum volumes of 7 × 107 m3 and 6 × 107 m3, respectively. Seven new chemical analyses show that ash produced by both eruptions was basaltic and similar to previously — erupted lavas of both volcanoes. Both ash blankets were sampled areally and stratigraphically before they were affected by rain. Chemical analyses of soluble materials leached from these ashes show that near the end of both eruptions the concentrations of soluble materials increased by about an order of magnitude. These changes are believed to reflect changes in the composition of eruptive gases.

Chemical composition and age determination of Tholeiitic rocks in the basic igneous complex, Ecuador

Abstract: Two new chemical analyses show that tholeiitic lava on the coastal plain of Ecuador is similar to basalt on Nicoya Peninsula of Costa Rica and other basalt found along the Pacific Coast of northwestern South America. Harzburgite is found in the same group of mafic volcanic and intrusive rocks here called basic igneous complex. K:Ar age determinations of basaltic lava in this complex show that igneous activity continued at least until early Eocene, although most of the hypabyssal rocks could be Late Jurassic to Late Cretaceous. Discussion includes possible correlation of the basic igneous complex of Ecuador, the Nicoya Complex of Costa Rica, similar rocks along the Pacific Coast of Panama and Colombia, and the basaltic floor of Nazca plate.

Lengthening kinetics of ferrite and bainite sideplates

Abstract: The rate of lengthening of ferrite and bainite sideplates and the radius of curvature of the plate edges were measured as a function of reaction temperature in three Fe-C alloys. These data were analyzed on the basis of an equation due to Trivedi. The analysis proved that the mobility of the sideplate edges is limited. The interfacial energy of these edges is of the order of 200 erg/cm2. Most of the supersaturation is used to drive the diffusion of carbon in austenite; comparatively little is accounted for by capillarity and by the finite mobility of the interface. On the basis of both the present results and of published micro-structural observations, it was concluded that ferrite and bainite sideplates lengthen by a ledge mechanism.

Influence of al, co, and si upon the kinetics of the proeutectoid ferrite reaction

Abstract: The effects ofca. 3 at. pct of Al, Si, or Co upon the kinetics of grain boundary ferrite allotriomorph formation (and thus upon hardenability) relative to those in Fe-C alloys of comparable carbon content were evaluated. All three alloying elements displace the TTT curve for the initiation of transformation to shorter times at the higher reaction temperatures. Both aluminum and silicon increase the parabolic rate constant for allotriomorph thickening,α, relative to that in their counterpart Fe-C alloys; the influence of cobalt uponα, if any, is appreciably less. In the Fe-C-Al and Fe-C-Si alloys, thickening proceeds noticeably less rapidly than volume diffusion control (as assessed by Atkinson’s analysis of the growth of an oblate ellipsoid) allows. In the Fe-C-Co and Fe-C alloys, the average calculated and experimental α’s are in better agreement but, evidently as a result of the presence of dislocation facets at a broad face of allotriomorphs, some allotriomorphs actually thickened more rapidly than calculated. The substantial scatter inα in all alloys was also attributed to these facets. Indirect determinations indicated that all three elements increased the rate of nucleation of ferrite allotriomorphs.

Pattern and mechanism of volcanic activity at the Santiaguito Volcanic Dome, Guatemala

Abstract: Santiaguito volcano has shown a continuous slow extrusion of dacite lava since 1922. In the 50 years of activity there have been four periods of abnormally high extrusion rates, interspersed by periods of little magma production. The type of activity shown by the volcano has been varied and crudely cyclic. Dome extrusion periods are accompanied by pyroclastic activity and followed by lava flows. There are now 16 time stratigraphic units delineated on the dome. Activity since 1967 has been especially closely observed. Dome extrusion at the west end of the complex has been accompanied by pyroclastic cruptions and plug dome extrusion at the east end. The eurrent extrusion rate has remained essentially constant since 1967 at about 5×106 m3/yr, far below Santiaguito’s 1922–71 average of 14×106 m3/yr. The active vent at the east end of the volcano (Caliente vent) has been the principal vent of the volcano since the creation of the explosion crater in 1902. After its initial period of dome extrusion (1922–25), the Caliente vent has chiefly produced pyroclastic eruptions as well as at least 95% of the dome’s lumarolic activity, while lateral vents have continued to give rise to lavas. Lava flows at Santiaguito have effective viscosity values of about 106 poises, while dome lavas are significantly more viscous. The differences in viscosity are in part related to volatile content of the lava when it reaches the surface. During dome extrusion, lavas lose their volatiles through pyroclastic activity before they reach the surface. Lava flows at Santiaguito occur when lava reaches the surface with higher volatile content. Obstruction of either the central (pyroclastic) vent or the lateral (dome extrusion) vent or both vents has an important influence on succeeding activity. In June 1972, at the time of this writing, the outbreak of new lava flows at both the Caliente and lateral El Brujo vents has just occurred, resulting from obstruction of pyroclastic activity by a large plug dome at the Caliente vent.

An investigation of grain-boundary embrittlement in Fe−P, Fe−P−S, and Fe−Sb−S alloys

Abstract: Grain-boundary embrittlement of pure iron due to phosphorous, antimony and sulfur is studied using fracture appearance transition temperature measurements and Auger electron emission spectroscopy chemical analysis of fractured surfaces. Phosphorus and sulfur are found to segregate to grain boundaries in the entire ferrite range. Segregation to grain boundaries of these elements in the austenite appears to be negligible. It is shown that the segregation of these elements to grain boundaries in iron does not conform to the Gibb's equilibrium segregation model. Sulfur appears to be a more severe embrittler of iron than does phosphorous.

Reactor for wet oxidation of organic matter

Abstract: A reactor for wet oxidation of organic matter in solution or dispersion in aqueous medium in which the reactor is in the form of an elongate horizontally disposed cylindrical housing subdivided into compartments by vertical walls having passages therethrough for communicating one compartment with the other and which subdivide the compartments into an upper vapor zone and a lower liquid zone and which includes means for high agitation of the aqueous medium within the liquid zone and the introduction of oxygen containing gas into the compartments in the vicinity of high agitation for distribution of the oxygen containing gas as fine bubbles into the aqueous medium for intimate association with the organic matter to provide active oxidation sites and for rapid transport of free radicals that are formed to the active oxidation sites to enable wet oxidation reaction to be carried out at lower temperatures and whereby unreacted oxygen in the vapor zone is re-entrained within the aqueous medium in the compartment and in adjacent compartments for fuller utilization of the oxygen and for more efficient oxidation reaction.

Solid Solution strengthening of high purity niobium alloys

Abstract: Athermal solid solution strengthening was examined in substitutional Nb(Cb)-Hf, Nb-W, and Nb-Ta alloys deformed at 900 K. Ultrahigh vacuum degassed single crystals were tested in compression. The concentration dependence of the yield stress is nearly linear in Nb-Hf and Nb-W alloys for the range of compositions tested (< 6 at. pct). The rate of hardening with solute addition was the greatest for the Nb-Hf alloys, considerably less for the Nb-W alloys, and the least for the Nb-Ta alloys which exhibited little strengthening. The results indicate that athermal strengthening in these alloys appears to be primarily dependent on the atomic size misfit between solvent and solute atoms and not on the elastic modulus mis-fit. Results on the slip behavior are also presented.

Synthesis of two discrete vibratory systems using eigenvalue modification.

Abstract: without an axial force. If the force P in each segment is specified, the analysis of either static or dynamic problems is straightforward. This is the case, for example, for beam-columns and for rotating beams. Problems in the elastic stability of columns can be handled by applying an arbitrary lateral force (or moment) and calculating the deflection with a series of successively greater axial forces. Southwell's method4 can then be applied to determine the buckling load. Incidentally, for a uniform column with any combination of end conditions, the exact expression for the elastic buckling load can be found directly from the stiffness matrix of the single beam segment. If the ends of the beam are restrained so as to prevent axial displacements, the axial force P is a nonlinear function of the lateral displacements. The customary assumption3 is that the deflection curve is a cubic. In this case, the axial force due to the stretching of the neutral axis of the beam segment shown in Fig. 3 is

Cl, F, and SO2 in Central American volcanic gases

Abstract: The Cl, F, SO2 contents and Cl/F and Cl/SO4 ratios in Central American volcanic gases are examined. 103−105 tons SO2 per day are given off during eruptions and 102 when a prominent vapor cloud persists between eruptive periods. Data regarding Cl and F and SO4 from leachates, condensates, and incrustations are compared. Our data suggest circumpacific volcanoes are SO2 poor relative to Cl and may be F poor although F is higher in basaltic Central American volcanoes than others.

Thermal energy storage material

Abstract: A thermal energy storage material which is stable at atmospheric temperature and pressure and has a melting point higher than 32°F. is prepared by dissolving a specific class of clathrate forming compounds, such as tetra n-propyl or tetra n-butyl ammonium fluoride, in water to form a substantially solid clathrate. The resultant thermal energy storage material is capable of absorbing heat from or releasing heat to a given region as it transforms between solid and liquid states in response to temperature changes in the region above and below its melting point.

Nuée ardente from santiaguito volcano April 1973

Abstract: The largest nuee ardente eruption of Santiaguito since November 1929, occurred April 19, 1973. The nuee descended the valley of the Rio Nima II for a distance of about 4 km. The ash flow itself was restricted to the river bed, but the hot gas cloud devastated an area of more than 3 square kilometers extending hundreds of meters on both sides of the river bed. Because the ash cloud stopped about 2 km from the nearest habitations, there were no fatalities.

The rate of γ‐benzyl‐L‐glutamate NCA polymerizations

Abstract: The primary amine initiated homopolymerization of γ-benzyl-L-glutamate NCA in dioxane at 25°C, 35°C, 50°C, and 65°C has been investigated. The reactions were virtually independent of temperature indicating an activation energy of less than 1 kcal/mole. The entropy of activation was estimated to be −65 entropy units at 300°K. The reaction proceeded in two stages. The first stage was zero-order with respect to monomer, whereas the second was first-order with respect to monomer. Both stages were first-order with respect to initiator. These results were interpreted by assuming that the rate constant for propagation was not independent of the degree of polymerization up to the point where a conformational transition to α-helix occurred.

Copolymerization of γ‐benzyl‐D,L‐glutamate NCA

Abstract: The copolymerization of γ-benzyl D- and L-glutamates has been investigated in dioxane at 25,35,50, and 65°C using hexylamine as initiator. Temperature changes had remarkably little effect on the overall rate constants indicating an activation energy of less than 1 kcal/mol. The rate curves indicated two stages in the polymerization process: an initial reaction of random coil with monomer which was independent of monomer composition and a final reaction between α-helical polymer and monomer which occurred stereoselectively. The conclusion was reached that the origin of the stereoselectivity was a specific adsorption of monomer at a site between the α-helical polymer and the “random” three or so end units of each polymer molecule. Die Copolymerisation von γ-Benzyl-D- und L-glutamat wurde in Dioxan bei 25, 35, 50 und 65°C untersucht. Die Bruttogeschwindigkeitskonstanten wurden auffallig wenig von der Temperatur beeinflust, was auf eine Aktivierungsenergie von weniger als 1 kcal/mol hinweist. Die Umsatz/Zeit-Kurven zeigen zwei unterschiedliche Prozesse an: eine anfangliche, von der Monomerzusammensetzung unabhangige Reaktion des wachsenden Polymeren in der Konformation eines statistischen Knauels mit dem Monomeren und eine zweite, stereoselektiv verlaufende Wachstumsreaktion des Polymeren in der Konformation einer α-Helix. Die Stereoselektivitat der Polymerisation ruhrt vermutlich von einer spezifischen Adsorption des Monomeren an einer Stelle zwischen dem helixartigen und etwa dem drittletzten Grundbaustein des nicht-helixartigen Teils jedes wachsenden Polymermolekuls her.

The eutectoid region of the ti-pd system

Abstract: DURING the course of an inves t iga t ion of eutectoid decomposi t ion m e c h a n i s m s in T i -X eutectoid sy s t ems , the authors l ea rned of the r e m a r k a b l e confusion which exis t s with r e spec t to the deta i led conf igura t ion of the eutectoid region (and other a r ea s ) of the T i P d phase d i ag ram. Three v e r s i o n s of the eutectoid reg ion p r e v ious ly repor ted a re shown by the light l ines in Fig. 1 ; the f i r s t three en t r i e s in Table I s u m m a r i z e the p r i n cipal f ea tu res of each ve r s ion . The Table shows that th ree d i f ferent i n t e rme ta l l i c compounds have been p r o posed as the s o l u t e r i c h phase in equ i l i b r ium with a at t e m p e r a t u r e s below that of the eutectoid, and that eutectoid t e m p e r a t u r e s va ry ing over a range of 115~ and eutectoid composi t ions rang ing f rom 25 to 41 wt pet have been repor ted . An inves t iga t ion of the T i P d eutectoid reg ion was there fore under taken in an effort not only to r e so lve these s e r ious confl ic ts but a lso to a s c e r t a i n why they may have occur red . The composi t ions of the al loys employed a re l i s ted in Table II. Approximate ly 30 g of each al loy were a rc mel ted by the tungs ten e l e c t r o d e i n e r t gas p ro c e s s on a water cooled copper hear th . Each al loy was mel ted twelve t imes , and both al loy and tungs ten e lec t rode were weighed before and af ter mel t ing to ensu re that no tungs ten con tamina t ion occur red . Mte r mel t ing the a l loys were wrapped in t an ta lum foil, sea led in evacuated s i l i ca capsu les , homogenized for 5 d at 1000~ and water quenched. Individual s l i ces , c a . 0.05 cm. thick, were cut f rom the a l loys , rewrapped in tan ta lum foil, and sea led again in evacuated s i l i ca capsules . These samples were then heat t r ea ted in the following sequence to de t e rmine the phase boundar i e s . Mte r solut ion annea l ing for 30 min at 950~ the spec imens were r eac ted in a lead bath for c a . 16 h at 550~ in o rde r to fo rm la rge amounts of f inely divided a and compound. The samples were then up quenched to a higher equ i l ib ra t ion t e m p e r a t u r e in another lead bath and f ina l ly quenched into iced 10 pct b r ine . The capsu les were sha t te red dur ing the quench. Anneal ing t imes of 8 h were employed for de t e rmina t i ons of the eutectoid t e m p e r a t u r e . Depending upon the t e m p e r a ture involved, t imes as shor t as 1 h were found suff i c ient to a s c e r t a i n points on t he /3 / ( a + [3) or the /3/(/3 + compound) phase boundary or " t r a n s u s " curve. Compar i son of Figs. 2(a) and (b) shows that, because of the f i ne sca l e of the d i spe r s ion of the cons t i tuents , opt ical mic roscopy was of l i t t le value in de t e rmi n i ng

Laboratory investigation of the effect of particle shape characteristics and gradation of aggregates on the skid resistance of asphalt surface mixtures

Abstract: This paper presents the results of a laboratory study concerning the effects of the particle shape characteristics and gradation of aggregates on the skid resistance of asphalt surface mixtures, as determined by the British portable skid tester. Four coarse aggregates and two fine aggregates, representing both natural and crushed materials, were used. The particle shape characteristics of these materials were determined by the particle index test for positive, quantitative identification. The aggregate materials were combined to form three different gradations, and mixed with the optimum content of an 85 to 100 penetration grade asphalt cement, as determined by the Marshall method of mixture design. Circular specimens 6 in. in diameter and 2 in. in thickness were used for the laboratory skid test. An accelerated polishing device similar to the one previously used by the investigators at Purdue University was employed to polish the surface of the test specimens. Skid resistance values were determined both before the specimens were polished and after different stages of polishing. The results of this investigation show that, within the range of the variables studied, the antiskid properties of the experimental surface mixtures improved with increasing values of the particle index of the fine aggregate. The skid resistance was also affected significantly by the gradation, as represented by the composition index, of the aggregates. For the unpolished specimens, the British portable number (BPN) is shown to increase with increasing values of the composition index. The trend was reversed for the polished specimens in that the BPN was increased as the values of the composition index were decreased.