Effect of Fe on ductility and cavitation in the superplastic Zn-22 Pct Al eutectoid

In this investigation, the ductility and cavitation behavior of five grades of the superplastic Zn-22 pct Al were studied under identical conditions of grain size, temperature, and initial strain rate. These five grades were prepared from high-purity Al and Zn using the same procedure but different Fe impurity levels; grades A, B, C, D, and E contain 1, 40, 120, 400, and 1460 ppm of Fe, respectively. A comparison between the present results and those reported earlier for the creep behavior of the five grades of Zn 22 pct Al demonstrates that while the presence of Fe has no noticeable effect on the steady-state creep rates during deformation in the superplastic region (where maximum ductility occurs), it has a pronounced effect on the ductility and fracture behavior of the alloy. The experimental data show that there is a significant drop in the average elongation to fracture when Fe concentration exceeds 125 ppm, and that the ductility of grade E is approximately 50 pct of grade A for initial strain rates less than 10⁻² s⁻¹. In addition, the data reveal two important findings regarding cavitation behavior. First, neither the initial grain size nor the occurrence of grain growth has an effect on cavitation that is as significant as that arising from the presence of excessive impurities. Second, the presence of other impurities in addition to Fe in Zn-22 pct Al has the effect of enhancing cavitation. The effect of Fe, alone or in the presence of other impurities, on ductility and cavitation in Zn 22 pct Al is examined in terms of phenomena associated with impurity segregation at boundaries. Formerly Research Associate, Materials Section, Department of Mechanical and Aerospace Engineering, University of California, Irvine, CA Formerly Graduate Research Assistant, Materials Science & Engineering, Department of Chemical and Biochemical Engineering, University of California, Irvine, CA This article is based on a presentation made at the “High Temperature Fracture Mechanisms in Advanced Materials” symposium, as a part of the 1994 Fall meeting of TMS, October 2-6, 1994, in Rosemont, Illinois, under the auspices of the ASM/SMD Flow and Fracture Committee.     

Needle track seeding following percutaneous ethanol injection for treatment of hepatocellular carcinoma

We report two cases of needle track seeding in the subcutaneous tissue and intercostal muscles following percutaneous ethanol injection for the treatment of hepatocellular carcinoma. In one patient, tumor seeding was observed 11 months after a total of 12 alcohol injections, and in the other patient, tumor seeding was observed 30 months after a total of 18 alcohol injections. The cases reported in the literature are discussed.     

Iterative solution of the global element equations

A previous paper [4]discussed in detail techniques for setting up the defining equations for the Global Element Method for elliptic partial differential equations, and sketched an iterative method for their solution. For a calculation in two-dimensions using M elements (with a basis of degree N - 1 in each element), operation counts of O(MN⁴) were achieved for both set-up and solution phases. Timings were included demonstrating this count for the set-up, but not the solution, phase. In this paper we describe a modified and simpler version of the iterative solution scheme and report timings obtained with an exploratory implementation of the scheme. These demonstrate the rapid convergence and O(MN⁴) behaviour predicted for it.     

Analysis of microwave ovens loaded with lossy process materials using the transmission-line-matrix method

The transmission-line-matrix (t.l.m.) numerical analysis technique is used in this paper to evaluate resonant frequencies and field parameters of the generated modes in microwave ovens loaded with lossy process materials. Analysis is made for the variation of resonant frequencies with the loss factor of the loading material. Temperature rise profile through the load is predicted from the calculated results of field parameters of sustained modes. The demonstrated data are for the dimensional parameters of a rectangular cavity of a commercial microwave oven operating at the standard heating frequency 915 MHz.     

A Generalized Analysis of Zero Cross over Timing Systems for Semiconductor Detectors

A generalized analysis of zero cross-over timing systems is developed and applied to the case of germanium planar detectors to determine operating parameters which give smallest timing dispersion under the constraints of available charge-sensitive preamplifier risetimes. Charts are given using normalized values to indicate these parameters. The conclusions are verified by experimental results published elsewhere.     

Persistence of some phenylamide pesticides in the aquatic environment—II. Adsorption on clay minerals

Adsorption of IPC, CIPC, Linuron, Neburon and Vitavax on bentonite clays (H-, Fe- and Ca-forms) was investigated. Adsorption was found to conform with Freundlich's equation and to depend on the nature of saturating cation as well as the chemical structure of phenylamides. Considerable amounts of bentonite are needed to bring about effective removal of these pesticides from polluted water. The role of suspended clay minerals in the decontamination of surface waters will be rather limited.     

Hydrothermal phase equilibria in Ln2O3-H2O-CO2 systems for Tm,Yb and Lu

Phase diagrams for Tm₂O₃-H₂O-CO₂. Yb₂O₃-H₂O-CO₂ and Lu₂O₃-H₂O-CO₂ systems at 650 and 1300 bars have been investigated in the temperature range of 100–800°C. The phase diagrams are far more complex than those for the lighter lanthanides. The stable phases are Ln(OH)₃, Ln₂(CO₃)₃.3H₂O (tengerite phase), orthorhombic-LnOHCO₃, hexagonal-Ln₂O₂CO₃. LnOOH and cubic-Ln₂O₃. Ln(OH)₃ is stable only at very low partial pressures of CO₂. Additional phases stabilised are Ln₂O(OH)₂CO₃and Ln₆(OH)₄(CO₃)₇ which are absent in lighter lanthanide systems. Other phases, isolated in the presence of minor alkali impurities, are Ln₆O₂(OH)₈(CO₃)₃. Ln₄(OH)₆(CO₃)₃ and Ln₁₂O₇(OH)₁₀,(CO₃)₆. The chemical equilibria prevailing in these hydrothermal systems may be best explained on the basis of the four-fold classification of lanthanides.     

Nonlinear distortion in common-emitter transistor amplifiers operated in the normal domain

Three nonlinear-distortion sources are analysed separately for polarity and magnitude of harmonics. If magnitudes are small, the resultant harmonic from these sources is the vector sum of its separated magnitudes. Universal charts are computed, to design amplifier circuits with simultaneous zero second and third harmonics. Experiments on an OC44 confirmed the theory, giving 2.5 mW with second to sixth harmonics better than ?75 dB, power gain 40 dB, and no feedback or push-pull.