Approximate operational calculus in chemical engineering

Approximations are suggested to extend the usefulness of operational calculus in solving boundary-value problems of interest to the chemical engineer. General approximations are outlined and specific ones illustrated. The use of computing machines with operational calculus is also considered.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37293/1/690030229_ftp.pd

Bounded and patched solutions for boundary value problems

The technique of bounding, that is of constructing general solutions for all ranges of the variables and parameters from solutions for a few limiting and special cases, is outlined and illustrated for problems in conduction and convection. The technique of patching, that is of constructing approximate solutions for multiphase media by the combination of pseudo solutions for the different regions, is also outlined and illustrated for problems in conduction and freezing. The shortcomings and possible inaccuracies of these two techniques are indicated as well.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37334/1/690110312_ftp.pd

Distribution and Environmental Tolerances of Aquatic Macroinvertebrate Families in the Agricultural Zone of Southwestern Australia

The agricultural zone of southwestern Australia is an extensively modified landscape. Ninety percent of the perennial native vegetation has been cleared and replaced by annual cereal crops and pasture. Consequently, groundwater has risen and much of the region is affected by dryland salinity. River geomorphology and water quality have been severely impacted by land clearing, anthropogenic patterns of land use, and secondary salinization. The objectives of this study were to determine patterns of distribution of aquatic macroinvertebrates in the region, and to identify environmental variables influencing these patterns. Aquatic macroinvertebrates were sampled at 176 river sites during spring 1997 and a range of environmental data were collected at each site. Eighty-one families were collected, with the fauna being dominated by insects. At the family level, macroinvertebrate communities were homogeneous and depauperate, and consisted of families that tolerated a broad range of environmental conditions. The fauna was particularly resilient to high salinities, with some families tolerating salinities orders of magnitude greater than previously reported for lotic waters. The most significant environmental factors influencing the distribution of aquatic invertebrates were rainfall, salinity, land use, and instream habitat

Paroxysmal Bundle Branch Block of Supraventricular Origin: A Possible Source of Misdiagnosis in Detecting Ventricular Tachycardia Using Time Domain Analyses of Intraventricular Electrograms

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72385/1/j.1540-8159.1990.tb02060.x.pd

Telangiectasia macularis eruptiva perstans: More Than Skin Deep

Systemic mastocytosis is a rare disease involving the infiltration and accumulation of active mast cells within any organ system. By far, the most common organ affected is the skin. Cutaneous manifestations of mastocytosis, including Urticaria Pigmentosa (UP), cutaneous mastocytoma or telangiectasia macularis eruptive perstans (TMEP), may indicate a more serious and potentially life-threatening underlying disease. The presence of either UP or TMEP in a patient with anaphylactic symptoms should suggest the likelihood of systemic mastocytosis, with the caveat that systemic complications are more likely to occur in patients with UP. TMEP can usually be identified by the typical morphology, but a skin biopsy is confirmative. In patients with elevated tryptase levels or those with frequent systemic manifestations, a bone marrow biopsy is essential in order to demonstrate mast cell infiltration. Further genetic testing for mutations of c-kit gene or the FIP1L1 gene may help with disease classification and/or therapeutic approaches. Rarely, TMEP has been described with malignancy, radiation therapy, and myeloproliferative disorders. A few familial cases have also been described. In this review, we discuss the clinical features, diagnosis and management of patients with TMEP. We also discuss the possible molecular pathogenesis and the role of genetics in disease classification and treatment

Radiant heat transfer in packed beds

The effective scattering and absorption cross sections were determined from measurements of radiant transmission through isothermal beds of glass, aluminum oxide, steel and silicon carbide spheres, cylinders, and irregular grains. The radiant conductivities were calculated from these cross sections. Back scattering was found to be the principal mechanism of attenuation for all of the packings. Absorption was a significant mechanism only for the silicon carbide grains. At 2,000°F. The radiant contribution to the total heat flux was estimated to vary from 35% for the silicon carbide packings to 85% for the glass packings.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37327/1/690090108_ftp.pd

Stability of a fluid in a rectangular region heated from below

Finite-difference methods were used to compute hydrodynamic instability due to natural convection in an enclosed horizontal rectangular region heated from below. Critical Rayleigh numbers were determined for a series of Prandtl numbers and length-to-height ratios. For Prandtl numbers greater than unity excellent agreement was obtained between these calculations and the values predicted by Kurzweg on the basis of a linearized theory. However, for Prandtl numbers less than unity the critical Rayleigh numbers exhibited a dependence on N Pr , which was not predicted by the linearized theory. For Rayleigh numbers greater than the critical, complete temperature and velocity fields were determined. The calculations assumed that the fluid motion is two dimensional. Experiments have indicated that the flow may be two or three dimensional depending on minor perturbations in the boundary conditions. Although a number of metastable two-dimensional circulations are possible for symmetrical initial conditions, the calculation always converged to a single, unique solution for any asymmetric initial condition.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37346/1/690130115_ftp.pd

Convective heat transfer from hightemperature air inside a tube

Local rates of convective heat transfer from air at high temperature to a cold wall were measured in the inlet region of a circular tube. Air entered the tube with a flat velocity and temperature profile at temperatures from 480° to 2,000°F. and flow rates corresponding to Reynolds numbers from 4,500 to 22,500. The inner surface of the 1.0-in. I.D. tube was maintained at approximately 100°F. by water cooling. Local rates of heat transfer were determined at 1.5, 4, 7, and 10 tube diameters from the entrance by measuring the radial temperature profile in thermally isolated, annular sections of the tube wall. The local rate data for all gas temperatures are well represented by previous correlations for small temperature differences if the gas properties are evaluated at the bulk temperature rather than at the film temperature. The data agree well with the data of previous investigators wherever the experimental ranges overlap.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37295/1/690040108_ftp.pd

Transient and steady state, free and natural convection, numerical solutions: Part I. The isothermal, vertical plate

Numerical values are presented for the transient velocity field, temperature field, and local heat transfer coefficient. These results were obtained by solving the partial differential equations describing the conservation of mass, momentum, and energy on an IBM-704 computer with finite difference methods in time-dependent form. The computed values for short times agree very well with the analytical solution for conduction only, and the limiting values for long time agree well with previous solutions for the steady state. The existence of a temporal minimum in the heat transfer coefficient is confirmed. The time required for the heat transfer coefficient to approach its steady state is shown to be less than previously predicted.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37326/1/690080525_ftp.pd

Heat transfer by radiation through porous insulations

Radiant transfer through fibrous and foamed insulating materials was investigated theoretically and experimentally. Transmission measurements were made under isothermal conditions with a black-body source varying from 200° to 800°F. Bulk density and fiber and pore size were also varied. These data were interpreted successfully in terms of a simple theoretical model. The results provide design information and define the contributions of the several mechanisms of transfer.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37305/1/690050413_ftp.pd