Showing papers by "Michigan Technological University published in 1976"

Nuée ardente eruption from the foot of a dacite lava flow, Santiaguito volcano, Guatemala

Abstract: Field observations of the zone affected by a small nuee ardente which issued from Santiaguito volcanic dome on 15 September 1973, have established clearly that the eruption came from the distal end of a blocky dacite lava flow. This emphasizes that such eruptions need not be related to an underground magma storage.

Application of heterogeneous nucleation theory to precipitate nucleation at GP zones

Abstract: The accelerated nucleation of precipitates at GP zones is explained using heterogeneous nucleation theory. Nucleation at zone : matrix boundaries is encouraged by several factors: 1) the chemical interfacial energy of zone : matrix boundaries can significantly decrease the interfacial energy barrier to nucleation; 2) destruction of quenched-in excess vacancies at incoherent portions of the nucleus surface may make the change in the volume free energy significantly more negative; 3) the crystal structures of the zone and matrix are identical and parallel which permits the nucleus to be faceted in both phases. Some additional assistance to nucleation at GP zones is provided by: 4) the accelerated diffusivity resulting from the presence of excess vacancies and 5) the large area of zone : matrix boundary per unit volume of matrix. These factors can more than compensate for the decreased solute supersaturation due to the formation of GP zones and provide an explanation for the enhanced nucleation of precipitates in the presence of GP zones.

The kinetics of coarsening in the Al-Al 3 Ni System

Abstract: The kinetics of coarsening of the Al-Al3Ni system during the stage of coarsening during which the microstructure is nearly representative of a random array of dispersed fibers is adequately expressed by conventional kinetics,i.e. Δr 3 ≅t wherer is average fiber radius andt coarsening time. The activation energy for the coarsening process is ∼315 kJ/mol and is composed of two terms: 1) the volume diffusion activation energy for nickel in the aluminum matrix and 2) the heat of solution of nickel in solid aluminum. It is pointed out that the conventional expressions for coarsening kinetics in this system can only be applied over a limited range of coarsening time since the microstructure is not generally representative of microstructures envisaged for coarsening process. Several comments and comparisons regarding the initiation of three-dimensional coarsening in this and other systems are made.

An efficient computational procedure for solving the multi-facility rectilinear facilities location problem

Abstract: The multi-facility location problem with rectilinear distances is considered. A necessary and sufficient optimality condition is stated and proved. An algorithm is developed and computational results are given. A new lower bound for multi-facility problems with lp distances is also given.

Microprocessors: Technology, architecture, and applications

Abstract: methods used for managing large systems. These include techniques such as work breakdown structure, management information systems, and risk assessments. In addition, the chapter concludes by emphasizing the importance of communicative ability in systems management. The final chapter presents a set of interesting practical problems which the author selected to enhance the presentation and emphasize salient points. A strong merit of this very recommendable book is that it emphasizes the author's strong industrial experience which has been coupled with extensive teaching experience in industrial and university programs. Having an author with this excellent and rare background is a very important asset for a book of this kind. In summary, I believe that this book will be very useful and stimulating to practicing engineers engaged in systems engineering, to program managers, and to students. The book is very suitable for a one-term introductory course on systems engineering/system management at either the undergraduate or graduate level. Instructors will find the course outline and solutions in the accompanying "Instructor's Guide and Solutions Manual" very useful. The reader will appreciate the abundance of examples and explanatory material in the book. Finally, I want to congratulate the author for writing a book which is a welcome contribution to the field and which will provide a better understanding of the system engineering and system management process.

The thermal stability of the fibrous copper-chromium eutectic

Abstract: The elevated temperature stability of the fibrous copper-chromium eutectic was studied and found to depend strongly upon the extent of structural defects in the as-grown eutectic. Both highly branched and nearly “ideal,” or regular, fibrous structures were obtained by controlling the crystal growing conditions. The branched structure coarsens at a much faster rate than the regular structure. In the regular structure, the initial stage of coarsening is described by a simple two-dimensional Ostwald ripening mechanism modified to take into account the effects of fiber geometry and volume fraction. The coarsening rate is limited by volume diffusion of the chromium solute in the copper matrix. The activation energy for coarsening is approximately 298 kJ/mol. After long time annealing, the chromium-rich fibers begin to pinch off and three dimensional coarsening is initiated which leads to a rapid increase in the coarsening rate. Application of theoretical analyses to the observed coarsening rate yields the productDΣ as 1.3 × 10−13 J/s at 1000°C, whereD is the diffusivity of Cr in solid Cu and Σ the Cu-Cr interfacial energy. Using reported values ofD, Σ is bracketed between 0.27 and 2.5 J/m2. The latter is quite high for a solid-solid interfacial energy, but is consistent with the rapid coarsening observed in this system.

Introduction to microcomputers and microprocessors

Abstract: One day, you will discover a new adventure and knowledge by spending more money. But when? Do you think that you need to obtain those all requirements when having much money? Why don't you try to get something simple at first? That's something that will lead you to know more about the world, adventure, some places, history, entertainment, and more? It is your own time to continue reading habit. One of the books you can enjoy now is introduction to microcomputers and the microprocessors here.

On the Kröner approach to the strain energy of an incoherent spherical precipitate

Abstract: Comparison of the results of the Kroner approach with the exact results provided by the Eshelby method for the strain energy associated with a spherical precipitate shows a noticeable error in the Kroner approach when the anisotropy of the matrix phase is severe. As a typical example, when the matrix anisotropy ratio is 3·5, the errors are found to be ca. 8·9 and 6·8% in the compression modulus and strain energy calculations, respectively. It is therefore concluded that higher-order terms, in addition to Kroner's lower-order terms, must be included when calculating the strain energy associated with an incoherent precipitate if a highly anisotropic matrix is involved and quite accurate results are required.

Flow stress asymmetry and cyclic stress-strain response in a BCC Ti-V alloy

Abstract: The cyclic stress-strain response of relatively stable bcc ..beta..-phase Ti--40 percent V alloy single crystals was studied. Flow stress asymmetry found in the alloy is attributed to the fact that screw dislocations, when gliding on a (211) plane, are more mobile in the twinning direction than in the antitwinning direction. Thus the flow stress of the crystal is greater when it is sheared in the antitwinning direction than in the twinning direction (the latter case results when crystals of the 100 orientation are stressed in tension and those of the 110 orientation are stressed in compression). Such behavior can be a result of the core of a screw dislocation being asymmetric under stress which causes the flow stress asymmetry observed. It should be noted that screw dislocations dominate the low temperature deformation structure of Ti-40V, which strongly suggests deformation is controlled by screw dislocation motion. The observation in Mo that the microyield stress is independent of crystal orientation could be a result of edge dislocation motion controlling microyield in that instance and this observation would not be inconsistent with screw dislocation motion controlling the macroscopic (epsilon/sub p/ greater than 0.05 percent) deformation measured here. (JRD)

The Effect of Fe Additions on the Embrittlement of Cu-Bi Alloys

Abstract: The effect of iron additions on the embrittlement of Cu-Bi alloys was studied by monitoring the ductility and grain boundary chemistry of embrittled specimens as a function of iron content. Mechanical properties improved for the same embrittling heat treatment as the bulk iron level increased, and this was correlated with a decrease in bismuth segregation to the grain boundaries. No iron was detected segregated to the boundaries, and several possible mechanisms were proposed to explain the beneficial effect of the iron additions. It was also found that approximately 70 min at 530°C is required to attain equilibrium for segregation of bismuth to the grain boundaries, and a diffusion coefficient derived from this data was found to be reasonable for bulk diffusion of bismuth in copper.

Magnetoelastic buckling: Theory vs. experiment: Paper presents an investigation of the conditions which must be satisfied in an experimental program in order to check theoretical predictions of magnetoelastic buckling fields

Abstract: Existing theoretical values and experimental values of magnetoelastic critical buckling fields for ferromagnetic beams and plates differ by a factor of two. The usual theoretical treatment assumes that the plate (a) is immersed in an infinite uniform field, (b) is infinitely wide and long, and (c) is made of a linearly magnetic material. We present an experimental investigation, combined with a simple analysis, which determines specific criteria which must be satisfied by experimental programs in order to validate the three assumptions. It is shown that experimental arrangements which validate (a) and (c) are feasible, but not (b). Hence, there is need for improved theoretical treatments which take into account the finite size of the specimens.

Agglomeration of steel plant waste dusts - by hydrothermal treatment of an aged wet mixt of dust, bonding agent and silica

Abstract: Hard agglomerates are made from steel plant waste dust contg. a hydrateable matl. of overburned lime and/or slag matl. by (a) forming a moist mixt. of the waste dust, 2-20 wt % (dry wt.) Ca and/or Mg (hydr)oxides and carbonates and 0.5-5 wt % Si matl. capable of forming a silicate bond with the bonding agent, the solids being 10 mesh size (b) ageing the mixt. to hydrate the hydrateable matl (c) forming into discrete masses (d) drying to 5 wt % moisture, and (e) hydrothermally hardening by contact with satd. steam at 100-244 degrees C. Compressive strength can be enhanced by drying after hydrothermal hardening to remove at least part of the moisture. Prod. may be used as a steel making process charge.