Showing papers by "Michigan Technological University published in 1993"

A simple approach to solve boundary-value problems in gradient elasticity

Abstract: We outline a procedure for obtaining solutions of certain boundary value problems of a recently proposed theory of gradient elasticity in terms of solutions of classical elasticity. The method is applied to illustrate, among other things, how the gradient theory can remove the strain singularity from some typical examples of the classical theory.

Rethinking Genre from a Sociocognitive Perspective.

Abstract: This article argues for an activity-based theory of genre knowledge. Drawing on empirical findings from case study research emphasizing “insider knowledge” and on structuration theory, activity the...

Multiframe blind deconvolution of astronomical images

Abstract: Maximum-likelihood estimation techniques are presented for the problem of forming object estimates from turbulence-degraded images when the point-spread functions are unknown. The inability of unconstrained maximum-likelihood methods to form meaningful estimates is acknowledged, and iterative algorithms are derived for estimating the object by using both a penalized maximum-likelihood method and a physically meaningful parameterization of the point-spread functions by phase errors distributed over an aperture.

The Technical Communicator as Author Meaning, Power, Authority

Abstract: The authors explore the parallels to be found by comparing descriptions of the technical communicator with differing views of the communication process—the transmission, translation, and articulation views of communication. In each of these views, the place of the technical communicator and of technical discourse shifts with respect to the production of meaning and relations of power. The authors argue from the standpoint of the articulation view for a new conception of the technical communicator as author and of technical communication as a discourse that produces an author.

Slice based metrics for estimating cohesion

Abstract: Previous work has shown that a relationship exists between cohesion and the slice profile of a program. The authors explore the use of several metrics based on such slice profiles to give a quantitative estimate of the level of cohesion in a module. Example modules are used to analyze the behavior of the metric values as the modules are modified such that the cohesion is changed. The sensitivity of the metrics to the various types of changes is discussed. >

Effects of Population Density and Pack Size on the Foraging Ecology of Gray Wolves

Abstract: A decline in the gray wolf ( Canis lupus ) population in Isle Royale National Park prompted an intensive study of radiocollared individuals in 1988–1991, complementing an ongoing study begun in 1958. During winter, 1959–1991, the proportion of lone wolves was higher when the population was at low levels, whereas average size of packs declined with density of wolves. Sizes of territories (1971–1991) were not related to size of packs. In winter, food availability (kg wolf−1 day−1) and kill interval (days/kill) varied inversely with size of packs. Social relationships of radiocollared lone wolves were flexible; they often formed temporary groups of two or three wolves. Small groups (less than four) and lone wolves roamed large areas of the island (300 km2 and 540 km2, respectively), frequently moving through territories of established packs. Solitary wolves and pairs readily killed adult moose, in contrast to a common belief that larger packs benefit from cooperative hunting.

Dynamic Analysis and Design of Laminated Composite Beams with Multiple Damping Layers

Abstract: This paper describes the formulation of a theory for the prediction of damping and natural frequencies of laminated composite beams with multiple viscoelastic damping layers. The damping layers are constrained (or sandwiched) by anisotropic laminates. The in-plane shear strains of the damping layers and the constraining layers are included in the model. Closed-form solutions for the resonance frequencies and modal loss factors of the composite beam system under simple supports are derived using the energy and Ritz method. A parametric study has been conducted to study the variation of dynamic stiffness and modal loss factor of the system with structural parameters (e.g., the ply orientations of laminas, thickness of the damping layers and the laminates), operating temperature, and damping material properties. The design of composite beams for maximizing the damping capacity is also presented in this paper which includes the determination of operating temperature range corresponding to given structural parameters and finding optimal structural parameters corresponding to given temperature range. Finally, some experimental results are compared with theory for the cases of single and double damping layer beam systems that show good agreement between predicted and measured natural frequencies.

Channel Convection in Partly Solidified Systems

Abstract: Channel plume flow arising from thermosolutal convection has been examined in metallic, aqueous and organic systems, covering a range of Prandtl numbers over three orders of magnitude. Observations were made directly in the transparent aqueous and organic systems and after the event in fully solidified metallic alloys. Plume dimensions and those of the concomitant channels are remarkably similar in all three materials, as are the composition differences between plumes or channels and the matrices. Detailed measurements and observations of these dimensions and of flow rates in the transparent materials are described and discussed. Analysis of plume flow rates in the transparent systems, if extrapolated to metals, would predict convective flow rates between 0.1 m s -1 and 0.2 m s -1 . The validity of this extrapolation is qualified by the way in which posthumous solute channels develop in the fully solidified metallic samples.

Method and apparatus for destroying organic compounds in fluid

Abstract: An apparatus for the photocatalytic oxidation of organic contaminants in fluid includes a reactor and a photocatalyst affixed to support material Preferably, the outer wall of the reactor is constructed of material transmissive of ultraviolet radiation The support material preferably is transmissive of ultraviolet radiation The support material can also be an adsorbent material Also, a method for photocatalytic oxidation of organic contaminants in fluid Also, a method for preparation of a supported photocatalyst Also, a supported photocatalyst adapted for the photocatalytic oxidation of organic contaminants in fluid Also, a method for preparing a photocatalyst adapted for the photocatalytic oxidation of organic contaminants in fluid

The kinetics of composite particle formation during mechanical alloying

Abstract: The kinetics of composite particle formation during attritor milling of insoluble binary elemental powders have been examined The effects of processing conditions (ie, mill power, temperature, and charge ratio) on these kinetics were studied Particle size distributions and fractions of elemental and composite particles were determined as functions of milling time and processing conditions This allowed the deduction of phenomenological rate constants describing the propensity for fracture and welding during processing For the mill-operating conditions investigated, the number of particles in the mill generally decreased with milling time, indicating a greater tendency for particle welding than fracture Moreover, a bimodal size distribution is often obtained as a result of preferential welding Copper and chromium 'alloy' primarily by encapsulation of Cr particles within Cu This form of alloying also occurs in Cu-Nb alloys processed at low mill power and/or for short milling times For other conditions, however, Cu-Nb alloys develop a lamellar morphology characteristic of mechanically alloyed two-phase ductile metals Increasing mill power or charge (ball-to-powder weight) ratio (CR) increases the rate of composite particle formation

Ab initio high-pressure structural and electronic properties of ZnS.

Abstract: The total energy of ZnS as a function of unit-cell volume has been calculated for the zinc-blende and rocksalt structures by the first-principles Hartree-Fock linear-combination-of-atomic-orbitals method. The calculated structural properties of both phases and the transition pressure between them agree very well with experiment. The band structure of the high-pressure phase is obtained and discussed in relation to zinc-blende ZnS and other IIB-VIA semiconductors.

Introductory remarks to the viewpoint set on propagative plastic instabilities

Abstract: Readers will certainly be familiar with the phenomenon of deformation bands occurring during plastic deformation of alloys. Lueders bands, which have been known for more than a century, as well as somewhat younger Portevin-Le Chatelier (PLC) bands associated with discontinuous yielding have occupied the metallurgists all these years, as their detrimental influence on the mechanical performance of alloys was creating significant technological problems. Though different in their nature, the two types of bands have one thing in common: they propagate across a material, usually a dilute alloy. While a single deformation front travels along a specimen in the Lueders band phenomenon, repetitive bands with well-defined front and rear edges accompany the PLC effect. Ways to avoid the Lueders and the PLC regimes have been empirically found in forming technologies, but mechanisms of band propagation are still not completely explained by theory.

A Simple Necessary and Sufficient Condition on Physically Realizable Mueller Matrices

Abstract: Development of simple tools to test physical realizability of measured or computed Mueller matrices is the subject of this paper. In particular, the overpolarization problem, i.e., the problem of ensuring that the output degree of polarization does not exceed unity is solved by finding an easily implementable necessary and sufficient condition. With G being the Lorentz metric, it states that a given matrix M is not overpolarizing if and only if the spectrum of GM T GM is real and an eigenvector associated with the largest eigenvalue is a physical Stokes vector. This result is used to characterize some M classes of special interest, and is used to test several examples from recent literature.

Measurement and verification of rates of sediment phosphorus release for a hypereutrophic urban lake

Abstract: The contribution of sediment release to the phosphorus budget of hypereutrophic Onondaga Lake was determined through laboratory measurements made on intact cores. Rates ranged from 9-21 mg P m-2 d-1 with a mean of 13 mg P m-2 d-1, values similar to those observed in other lakes of comparable trophic state. There was no statistically significant trend in rates in time (July versus September) or in space (location along the major N/S axis of the lake). Rates of sediment phosphorus release measured in the laboratory compared favorably with the observed rate of soluble reactive phosphorus accumulation in the lake’s hypolimnion. The sediments are the second largest source of phosphorus for Onondaga Lake, contributing 24% of the overall phosphorus load to the system.

Ductilization of Ti-Ni-Pd shape memory alloys with boron additions

Abstract: Although high transition temperature shape memory alloys (SMAs) are desirable for certain applications, most usable SMAs have upper transition temperature ranges (TTRs) less than 100°C It has been reported that Pd substitutions for Ni in Ni-Ti alloys can increase the TFR to 500°C for more than 15 atomic pct Pd[1, 2]; however, in addition to higher cost, these alloys have poor ductility at room temperature[3, 4]

Striving for Balance: A Hundred Years of the American Society for Engineering Education

Abstract: This paper provides an overview of the history of the American Society for Engineering Education (ASEE) from its founding in 1893 to the present. The authors see two major continuities in the organization’s hundred year history: the search for methods of improving classroom instruction and the pursuit of national recognition as the spokesman for engineering education. An organization concerned with classroom teaching draws its strength from the ranks of teaching faculty; an organization seeking national visibility must draw its leaders from administrators, especially deans. ASEE’s history is viewed as an continuing effort to balance these two broad purposes within a single organization.

Supply of phosphorus to the water column of a productive hardwater lake: controlling mechanisms and management considerations

Abstract: Onondaga Lake is a hypereutrophic, industrially polluted lake located in Syracuse, NY. High hypolimnetic concentrations of H2S that develop after anoxia restrict the accumulation of total Fe2+ due to the formation of FeS, and may limit Fe-PO4 interactions. High water column concentrations of Ca2+ and high rates of CaCO3 deposition occur due to inputs of Ca2+ from an adjacent soda ash manufacturing facility. Patterns of P concentration and other water chemistry parameters in the lower waters, and results from chemical equilibrium calculations, suggest that Ca-PO4 minerals may regulate the supply of P from sediments to the water column in Onondaga Lake. These findings have important management implications for Onondaga Lake. First, declines in water column Ca2+ concentrations due to reductions in industrial CaCl2 input may result in conditions of undersaturation with respect to Ca-PO4 mineral solubility and increases in the release of P from sediments to the water column. Second, introduction of O2 from hypolimnetic oxygenation, as a lake remediation initiative, may enhance P supply from sediments, because of increased solubility of Ca-PO4 minerals at lower pH.

Milling dynamics: Part I. Attritor dynamics: Results of a cinematographic study

Abstract: The motions of grinding media and powder in an attritor canister were studied by means of filming the agitated charge and frame-by-frame scrutiny of the footage. In conjunction with auxiliary experiments, this permitted semiquantitative analysis of the milling action. In particular, the mill can be divided into several regions characterized by different balances between direct impacts and rolling/sliding of the grinding media. Simple calculations suggest that impacts are more capable of effecting mechanical alloying (MA) than are rolling or sliding events in an attritor. Powder circulation within an operating mill was also investigated. Based on the results and the accompanying analysis, concepts for improved attritor design are presented.

Constraints on Mueller matrices of polarization optics.

Abstract: The issue of physical realizability constraints on depolarizing scattering or imaging systems is addressed. In particular, the overpolarization problem, i.e., the problem of ensuring that the output degree of polarization is always smaller than (or equal to) unity, is discussed in detail. A set of necessary conditions for the elements of a Mueller matrix is derived. These conditions can be used to test the accuracy of polarimetric measurements and computations. Several recent experimental examples from polarization optics and radar are discussed.

The cost of broadcasting on star graphs and k-ary hypercubes

Abstract: It is shown that for two common broadcasting problems, a star graph performs better than a k-ary hypercube with a comparable number of nodes only in networks consisting of an impractically large numbers of nodes. This result is based on a comparison of the costs of known solutions to the one-to-all broadcast and the complete broadcast problems for each network. It is suggested that the cost of solutions to these common problems is a better indication of the expected performance of an interconnection network than is a comparison of scalar measures such as the diameter and degree. >

Quasi-symmetric designs, codes, quadrics, and hyperplane sections

Abstract: It is proved that a quasi-symmetric design with theSymmetric Difference Property (SDP) is uniquely embeddable as a derived or a residual design into a symmetric SDP design. Alternatively, any quasi-symmetric SDP design is characterized as the design formed by the minimum weight vectors in a binary code spanned by the simplex code and the incidence vector of a point set in PG(2m-1, 2) that intersects every hyperplane in one of two prescribed numbers of points. Applications of these results for the classification of point sets in PG(2m-1, 2) with the same intersection properties as an elliptic or a hyperbolic quadric, as well as the classification of codes achieving the Grey-Rankin bound are discussed.