Showing papers by "Lehigh University published in 1980"
TL;DR: Baraff, Kane, and Schluter as discussed by the authors showed that interstitial boron has negative-$U$ properties with a single donor level (0/+) at ${E}_{c}\ensuremath{-}013$ eV.
Abstract: Experimental evidence is presented in support of a recent suggestion by Baraff, Kane, and Schl\"uter that the isolated lattice vacancy in silicon is an Anderson negative-$U$ system The second donor level (+/++) (of charge state + if defect level is occupied by an electron; ++, if unoccupied) is located at ${E}_{v}+013$ eV, above a first donor level (0/+) at ${E}_{v}+005$ eV Evidence is presented that interstitial boron has negative-$U$ properties with a single donor level (0/+) at ${E}_{c}\ensuremath{-}013$ eV, above a single acceptor level (-/0) at ${E}_{c}\ensuremath{-}045$ eV
227 citations
TL;DR: In this article, the authors developed a predictive capability for the quantitative assessment of crack growth under fatigue loadings, which can be applied expediently to examine the combined influence of crack geometry, complex loadings and material properties.
223 citations
TL;DR: In this paper, over 1000 sets of data for forced convective boiling of distilled water, distilled glycol and aqueous mixtures of ethylene glycol are reported, showing that a significant reduction in the heat transfer coefficient is observed for mixtures attributable to mass transfer effects.
Abstract: Over 1000 sets of data for forced convective boiling of distilled water, ethylene glycol and aqueous mixtures of ethylene glycol are reported. Most of these data were taken in the annular flow regime. These data indicate a previously unrecognized Prandtl number effect on the boiling heat transfer for both pure components and mixtures. A significant reduction in the heat transfer coefficient is observed for mixtures attributable to mass transfer effects. An expression is developed which accounts for both of these effects and correlates the experimental data to within a mean deviation of 14.9%. This correlation reduces to the standard Chen correlation for pure fluids with Prandtl numbers close to unity.
216 citations
TL;DR: A strong positive relationship between the number of intersections along a traversed linear pathway and the estimated length of that path was revealed and the findings are discussed in relation to information processing/storage and pathway segmentation models.
Abstract: Two experiments were performed to assess the effects of intersections on distance cognition in the urban environment. A laboratory study examined estimated traversed distance as a function of the n...
193 citations
TL;DR: In this paper, the α + γ two-phase fields of the Fe-Ni and F-Ni (P saturated) phase diagrams have been determined in the composition range 0 to 60 wt pet Ni and in the temperature range 700 to 300 °C.
Abstract: The α + γ two-phase fields of the Fe-Ni and Fe-Ni (P saturated) phase diagrams have been determined in the composition range 0 to 60 wt pet Ni and in the temperature range 700 to 300 °C. The solubility of Ni in (FeNi)3P was measured in the same temperature range. Homogeneous alloys were austenitized and quenched to form α2, martensite, then heat treated to formα (ferrite) + γ (austenite). The compositions of the α and γ phases were determined with electron microprobe and scanning transmission electron microscope techniques. Retrograde solubility for the α/(α + γ) solvus line was demonstrated exper-imentally. P was shown to significantly decrease the size of the α + γ two-phase field. The maximum solubility of Ni in α is 6.1 ± 0.5 wt pct at 475 °C and 7.8± 0.5 wt pct at 450 °C in the Fe-Ni and Fe-Ni (P saturated) phase diagrams, respectively. The solubility of Ni in α is 4.2 ± 0.5 wt pct Ni and 4.9 ± 0.5 wt pct Ni at 300 °C in the Fe-Ni and Fe-Ni (P saturated) phase diagrams. Ternary Fe-Ni-P isothermal sections were constructed between 700 and 300 °C.
177 citations
TL;DR: In this article, the elasticity problem for an orthotropic strip or a beam with an internal or an edge crack under general loading conditions is considered and numerical results are given for four basic loading conditions, namely, uniform tension, pure bending, three point bending, and concentrated surface shear loading.
Abstract: The elasticity problem for an orthotropic strip or a beam with an internal or an edge crack under general loading conditions is considered. The numerical results are given for four basic loading conditions, namely, uniform tension, pure bending, three point bending, and concentrated surface shear loading. For the strip with an edge crack additional results regarding the crack opening displacements are obtained by using the plastic strip model. A critical quantity which is tabulated is the maximum compressive stress in the plane of the crack. It is shown that this stress may easily exceed the yield limit in compression and hence may severely limit the range of application of the plasticity results.
139 citations
01 Nov 1980
TL;DR: In this article, the equilibrium spreading pressure of a spreading liquid or vapor on polyethylene polymers was predicted exactly by π e = 2(γ d L γ d S ) 1 2 −2γ L where γLd is the dispersion force contribution to the surface tension of the spreading liquid and γSd is a contribution to surface energy of the substrate.
Abstract: When a spreading liquid or vapor can interact with a substrate only by dispersion forces, as with alkanes on any substrate, or with any spreading liquid on saturated hydrocarbon polymers, the equilibrium spreading pressure is shown to be predicted exactly by: π e =2(γ d L γ d S ) 1 2 −2γ L where γLd is the dispersion force contribution to the surface tension γL of the spreading liquid and γSd is the dispersion force contribution to the surface energy of the substrate. A new laboratory technique is introduced for direct measurement of πe of a spreading vapor on hydrophobic solids, using the difference in contact angles of a test liquid on the solid in air and in the presence of the spreading vapor. For cyclohexane on polyethylene at 20°C πe is found to be 7.19 dyn/cm; the above equation predicts 7.15 dyn/cm. By using this new technique it is proven unequivocably that high-energy liquids such as methylene iodide and water do not adsorb or spread on low-energy surfaces such as polyethylene or polytetrafluoroethylene.
126 citations
TL;DR: In this article, the authors investigated the influence of water vapor on fatigue crack growth in aluminum alloys and showed that at a frequency of 5 Hz, the rate of crack growth is essentially unaffected by water vapor until a threshold pressure.
Abstract: Fracture mechanics and surface chemistry studies were carried out to develop further understanding of the influence of water vapor on fatigue crack growth in aluminum alloys. The room temperature fatigue crack growth response was determined for 2219-T851 aluminum alloy exposed to water vapor at pressures from 1 to 30 Pa over a range of stress intensity factors (K). Data were also obtained in vacuum (at < 0.50 μPa), and dehumidified argon. The test results showed that, at a frequency of 5 Hz, the rate of crack growth is essentially unaffected by water vapor until a threshold pressure is reached. Above this threshold, the rates increased, reaching a maximum within one order of magnitude increase in vapor pressure. This maximum crack growth rate is equal to that obtained in air (40 to 60 pct relative humidity), distilled water and 3.5 pct NaCl solution on the same material. Parallel studies of the reactions of water vapor with fresh alloy surfaces (produced either byin situ impact fracture or by ion etching) were made by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). The extent of surface reaction was monitored by changes in the oxygen AES and XPS signals. Correlation between the fatigue crack growth response and the surface reaction kinetics has been made, and is consistent with a transport-limited model for crack growth. The results also suggest that enhancement of fatigue crack growth by water vapor in the aluminum alloys occurs through a “hydrogen embrittle ment” mechanism.
123 citations
01 Jan 1980
TL;DR: In this paper, the authors present a classical example of selectivity for partial oxidation to ethylene oxide versus complete combustion to carbon dioxide and water, which is a classic example of a selectivity problem for catalysts.
Abstract: Selective oxidation of ethylene to ethylene oxide over supported silver catalysts is not only one of the very few uses of that element as n catalyst of industrial importance, it also has been the basis for the manufacture of an important chemical intermediate that underlies the large glycol industry as well as the manufacture of a varied array of solvents and related chemical materials, The chemical reactions offer a classical example of selectivity for partial oxidation to ethylene oxide versus complete combustion to carbon dioxide and water
120 citations
TL;DR: The pendant amino and mercapto groups on 4-amino-3-mercapto-4-H-4H-1,2,4-triazoles can be cyclized by phenylpropargyl aldehydes as discussed by the authors.
105 citations
01 Feb 1980
TL;DR: A new “serum replacement” method is described, which gives results in much better agreement with those of ion exchange than those of dialysis, yet avoids the arduous purification of the ion exchange resins.
Abstract: Latexes have been cleaned for surface characterization by ion exchange and dialysis. Ion exchange is rapid and gives quantitative results, but requires purification of the ion exchange resins. Dialysis is slow and removes only part of the adsorbed emulsifier and replaces only part of the counterions with H+ ions. This paper describes a new “serum replacement” method, which gives results in much better agreement with those of ion exchange than those of dialysis, yet avoids the arduous purification of the ion exchange resins. Distilled, deionized water is pumped through the latex while the particles are confined in a stirred cell by a Nuclepore filtration membrane. This washing with water removes the solute electrolyte and adsorbed emulsifier, but does not completely replace the Na+ and K+ counterions with H+ ions. Further washing with 5 × 10−4 N hydrochloric acid, followed by water to remove excess acid, replaces these counterions completely. Seven polystyrene latexes prepared with persulfate ion initiator—three prepared with conventional emulsifier and four with sulfonated comonomeric emulsifiers—were cleaned by serum replacement, ion exchange, and dialysis. The surface charges after cleaning with serum replacement were in good agreement with those after cleaning with ion exchange to constant charge, while those after dialysis were much lower. All latexes contained only strong-acid groups; no weak-acid groups were found. For latexes prepared with comonomeric emulsifiers, serum replacement can separate the water-soluble polymer in a form suitable for analysis. The removal of solute electrolyte and adsorbed emulsifier by serum replacement can be predicted by mathematical models. The rate of removal of solute electrolyte is slower than predicted by theory for reasons not yet determined. The rate of removal of adsorbed sodium lauryl sulfate indicates that equilibrium between the adsorbed and solute species is not attained during the serum replacement process.
TL;DR: Optically detected magnetic resonance of isolated zinc vacancies (V−Zn) was observed for a distant donor-acceptor recombination luminescence band at 720 nm in ZnSe Vacancies with adjacent chlorine donors (A-centers) as discussed by the authors.
TL;DR: An experiment was performed to evaluate the utility of an information storage model of distance cognition, and the route with more remembered attributes was consistently estimated as longer than an equivalent route with difficult-to-remember attributes.
Abstract: An experiment was performed to evaluate the utility of an information storage model of distance cognition. Subjects walked matched routes segmented with either easily memorable or difficult-to-remember proper names. In accord with the information storage model, the route with more remembered attributes was consistently estimated as longer than an equivalent route with difficult-to-remember attributes.
TL;DR: In this paper, a differentially-aspirated superheat probe was developed to measure vapor temperatures in postcritical-heat-flux, dispersed-flow boiling, which indicated very significant nonequilibrium, with vapor superheats of several hundred degrees (/sup 0/C).
Abstract: A differentially-aspirated superheat probe was developed to measure vapor temperatures in post-critical-heat-flux, dispersed-flow boiling. Measurements obtained for water, at low-to-moderate pressures and mass flow rates in a tube, indicated very significant nonequilibrium, with vapor superheats of several hundred degrees (/sup 0/C). Predictions of published correlations showed unsatisfactory agreement with the experimental results.
TL;DR: In this article, the root-square-mean residence times were used in a modified packet model to predict effective heat transfer coefficients, and the model was applied to a vertical tube in fluidized beds.
Abstract: Heat transfer from a vertical tube in fluidized beds was investigated by measurement of emulsion packet residence times. The root-square-mean residence times were then used in a modified packet model to successfully predict effective heat transfer coefficients.
TL;DR: In this article, the kinetic effects of total surface area, average silver crystallite size, and the morphology of supported silver catalysts were investigated under ethylene oxidation conditions, and specific activity and selectivity of the catalysts are found to be strong functions of the total area.
TL;DR: In vitro apparatus is described which simulates conditions in the acetabulum during the Charnley-Muller type low friction arthroplasty procedure, providing a direct measurement of the temperature history of the surface where the bone would be in contact, and data indicate that the temperature at the bone-cement interface is linearly dependent on local cement thickness.
TL;DR: In this paper, the influence of coupled diffusion of heat and moisture on the transient stresses in a composite was investigated analytically where the moisture diffusion coefficient is taken to be temperature dependent while the thermal diffusion coefficient was kept constant.
TL;DR: In this paper, the boundary-layer structure on the side walls of a rectangular cavity filled with a porous material is determined using an integral relations approach, which leads to results for the core mass flux, for core-temperature gradient and for the heat transfer characteristics which are in excellent agreement with numerical solutions of the boundary layer equations.
TL;DR: The present experiment involved a greater variety of forms of retrieval question and search words were selected independently by two different people for each retrieval question, producing average recall ratios and false retrieval rates.
Abstract: Passage retrieval (already operational for lawyers) has advantages in output form over reference retrieval and is economically feasible. Previous experiments in passage retrieval for scientists have demonstrated recall and false retrieval rates as good or better than those of present reference retrieval services. The present experiment involved a greater variety of forms of retrieval question. In addition, search words were selected independently by two different people for each retrieval question. The search words selected, in combination with the computer procedures used for passage retrieval, produced average recall ratios of 72 and 67%, respectively, for the two selectors. The false retrieval rates were (except for one predictably difficult question) respectively 13 and 10 falsely retrieved sentences per answer-paper retrieved.
TL;DR: In this article, a theoretical model for core fracture in bimetal rods during extrusion has been developed and a fracture criterion established, based on the upper bound theorem in limit analysis, and the analysis can be extended to develop criteria for sleeve fracture and for both core and sleeve fracture during drawing.
Abstract: Based on the upper-bound theorem in limit analysis, a theoretical model for core fracture in bimetal rods during extrusion has been developed and a fracture criterion established. The variables affecting core fracture are: reduction in area (r%), die geometry, friction (m), relative size of the core and relative strength of the core. Within the wide range of possible combinations of these process variables, only a small range permits extrusion without fracture. With suitable modifications the present analysis can be extended to develop criteria for sleeve fracture during extrusion and for both core and sleeve fracture during drawing.
TL;DR: It was found that sex-role socialization is more influential for automony development than is either level of parental power or age, and both age and father's use of democracy were the most influential variables on identity development.
Abstract: Two studies were undertaken to examine parental influences on autonomy and identity development In Study 1, 262 adolescents in seventh and eleventh grades were given Kurtines's autonomy measure, Simmons's identity measure, and Elder's questions regarding the adolescents' perceptions of their parents' autocratic, democratic, or permissive parenting styles Study 2 was a replication with 168 subjects Across both studies it was found that sex-role socialization is more influential for automony development than is either level of parental power or age Both age and father's use of democracy were the most influential variables on identity development
TL;DR: In this article, the blue donor-acceptor pair luminescence in $6H$-SiC containing nitrogen and aluminum was reported, with the nitrogen donor resonance is isotropic, with $g=2.004 and the aluminum acceptor resonance is 0.002.
Abstract: Optical detection of magnetic resonance is reported for the blue donor-acceptor pair luminescence in $6H$-SiC containing nitrogen and aluminum. The nitrogen donor resonance is isotropic, with $g=2.004\ifmmode\pm\else\textpm\fi{}0.002$. Resonances for the aluminum acceptor in three inequivalent silicon lattice sites are detected with ${g}_{\ensuremath{\parallel}}=2.412\ifmmode\pm\else\textpm\fi{}0.002, 2.400\ifmmode\pm\else\textpm\fi{}0.002, \mathrm{and} 2.325\ifmmode\pm\else\textpm\fi{}0.002$; and ${g}_{\ensuremath{\perp}}=0$. This indicates an effective-mass-like character for the acceptor, but with reduced orbital contribution due to the localization. Evidence for corresponding reduction in the spin-orbit splitting is cited.
TL;DR: In this article, a general numerical method of solution to the transverse normal stress and longitudinal shear stress distributions in the adhesive layers of bonded stiffener plates, double lap joints, and strap joints, all of dissimilar orthotropic adherends, was presented.
Abstract: The paper presents a general numerical method of solution to the transverse normal stress and longitudinal shear stress distributions in the adhesive layers of bonded stiffener plates, double lap joints, and strap joints, all of dissimilar orthotropic adherends. The bending deformations and the transverse shear deformations are included in the analytical model. The present influence of bending deformations of adherends on both the normal and shear stresses in adhesive layers is discussed in detail for practical cases.
TL;DR: Polymethyl methacrylate bone cement is tested for the strength and toughness of bone cement involved in total hip replacement operations.
Abstract: Polymethyl methacrylate bone cement is tested at the Institute of Fracture and Solid Mechanics Laboratory, Lehigh University. Standard tensile coupon and compact tension specimens are molded under varying conditions of temperature and pressure. Test results are obtained for the strength and toughness of bone cement involved in total hip replacement operations.
TL;DR: In this paper, an analytical scanning transmission electron microscopy (AEM) was used to study grain-boundary solute segregation in the systems MgO-NiO, A12O3-Y, O3, NiO-Cr2O3, and NiOAl 2O3.
Abstract: Analytical scanning transmission electron microscopy (AEM) was used to study grain-boundary solute segregation in the systems MgO-NiO, A12O3-Y, O3, NiO-Cr2O3, and NiO-Al2O3. Electron beam spreading within the specimen was incorporated into a model to quantitatively measure solute segregation. Grain-boundary segregation occurred in A12O3-Y2O3 and NiO-Cr2O3 but was not detected in MgO-NiO and NiO-Al2O3 specimens. These results and the quantitative measurements agree with equilibrium solute segregation theories. Microhard-ness measurements indicate no difference in hardness between the grain boundary and the matrix for Cr-doped NiO, a system in which segregation was detected.