Showing papers by "Lehigh University published in 1979"

The organized nature of flow impingement upon a corner

Abstract: Oscillations of impinging flows, which date back to the jet-edge phenomenon (Sondhaus 1854), have been observed for a wide variety of impingement configurations. However, alteration of the structure of the shear layer due to insertion of an impingement edge (or surface) and the mechanics of impingement of vortical structures upon an edge have remained largely uninvestigated. In this study, the impingement of a shear layer upon a cavity edge (or corner) is examined in detail. Water is used as a working fluid and laser anemometry and hydrogen bubble flow visualization are used to characterize the flow dynamics. Reynolds numbers (based on momentum thickness at separation) of 106 and 324 are employed. Without the edge, the shear layer produces the same sort of non-stationary (variable) velocity autocorrelations observed by Dimotakis & Brown (1976). When the edge is inserted, the organization of the flow is dramatically enhanced as evidenced by a decrease in variability of autocorrelations and appearance of well-defined peaks in the corresponding spectra. This enhanced organization is not locally confined to the region of the edge but extends along the entire length of the shear layer, thereby reinforcing the concept of disturbance feedback. Comparison of spectra with and without insertion of the edge reveals a remarkable similarity to those of a non-impinging shear layer with and without application of sound at a discrete frequency (Browand 1966; Miksad 1972); with enhanced organization at the fundamental frequency, simultaneous enhancement occurs also at the sub- and higher-harmonics.

Principles of Thin Film X-Ray Microanalysis

Abstract: The scanning electron microscope-electron probe microanalyzer (SEM-EPMA) and transmission electron microscope (TEM) are two established tools for microscopy. The first instrument enables one to obtain high magnification pictures as well as microchemical information from micron sized areas in solid samples. The second instrument enables one to obtain high magnification pictures and diffraction data from electron transmission thin specimens. Over 10 years ago DUNCUMB (1968) mounted a wavelength dispersive x-ray spectrometer on a TEM in order to obtain chemical and structural as well as diffraction data from the same area of a thin specimen. This idea of a combination instrument has developed rapidly in the last few years into the scanning transmission electron microscope—analytical electron microscope (STEM-AEM) instrument of today. In the modern version of this instrument a 60 to 200 kV electron beam is focused to < 100 and often to < 10 nm diameter at the specimen surface. Scanning coils move the focused beam over the specimen to obtain a STEM image. The emitted x-rays are measured with an energy dispersive x-ray spectrometer (EDS). Quantitative electron probe microanalysis can be accomplished when the focused beam is positioned at selected points on a specimen. In addition, particle identification and x-ray scanning can be performed with this instrument.

A Comparison of Some Approximate Confidence Intervals for the Binomial Parameter

Abstract: We consider two confidence intervals for the binomial parameter that are frequently recommended for large samples. We show that one of these, which is in fact less popular in the literature, enjoys certain advantages over the other one. The criteria used for comparison are the confidence coefficients, the lengths, and the Neyman shortness of the intervals.

Fatigue Strength of Fillet Welded Cruciform Joints

Abstract: A method for determining the fatigue strength of fillet welded cruciform joints is presented. The inadequacy of the present fatigue specification is examined through comparison with experimental data. The significance of the lack of penetration occurring at the weld root upon experimental fatigue is presented. A fracture mechanics model of the fatigue behavior is developed and correlated with experimental results. Design equations based on the model and a design example are presented.

Recombination-enhanced migration of interstitial aluminum in silicon

Abstract: We report the first observation of recombination-enhanced recovery of a defect in silicon which is otherwise normally stable at room temperature. This defect, produced by 1.5-MeV electron irradiation of aluminum-doped material at room temperature, is identified as isolated interstitial aluminum through correlated deep-level transient-capacitance spectroscopy and EPR studies. The recovery rate constant in the absence of minority-carrier injection is 3(${10}^{9}$) exp(- 1.2\ifmmode\pm\else\textpm\fi{}0.1 eV/kT) ${\mathrm{sec}}^{\ensuremath{-}1}$. Under saturated injection conditions, it is 70 exp(- 0.27\ifmmode\pm\else\textpm\fi{}0.03 eV/kT) ${\mathrm{sec}}^{\ensuremath{-}1}$. This represents an enhancement of the recovery rate by a factor of \ensuremath{\sim} ${10}^{8}$ at room temperature. We conclude that this enhancement results from an efficient conversion of the electronic energy available upon carrier capture to local vibrational energy of the defect which assists it over the migration barrier. The second donor level of the defect ($\frac{{\mathrm{Al}}_{i}^{+}}{{\mathrm{Al}}_{i}^{++}}$) is determined to be at ${E}_{V}+0.17$ eV. We conclude, however, that the enhancement results from carrier capture and recombination at the first donor level ($\frac{{\mathrm{Al}}_{i}^{0}}{{\mathrm{Al}}_{i}^{+}}$) the position of which has not yet been determined. The implications of these results to the properties of the self-interstitial in silicon are discussed.

Some Relationships between Personality and Consumer Decision Making

Abstract: Data are reported supporting the hypothesis that the personality variables anxiety and self-confidence are related to consumer choice behavior. Post hoc analyses construct six personality factors w...

Extreme Sensitivity of Enveloped Viruses, Including Herpes Simplex, to Long-Chain Unsaturated Monoglycerides and Alcohols

Abstract: Unsaturated monoglycerides and alcohols of chain lengths of 16 or 18 carbons were found to be extremely potent inactivators of two enveloped viruses, herpes simplex virus type 2 and bacteriophage φ6. The lipid-containing bacteriophage PM2 was also inactivated by some of these amphiphilic molecules. Treatment of herpes simplex virus type 2 with these compounds at concentrations as low as 0.2 μM reduced virus survival to 50% in 30 min, making these agents the most potent inactivators of herpes simplex viruses discovered that are not cytotoxic to mammalian cells. Detailed characterizations of the effects of unsaturated monoglycerides and alcohols on bacteriophages φ6 and PM2 showed that the inactivated φ6 virion remained nearly intact but that PM2 was almost completely disrupted by the inactivating treatment. Some of the compounds inactivate the viruses even at low temperature (0°C). Excess amounts of diglycerides and phospholipids interfere with the inactivating abilities of some of the unsaturated monoglycerides and alcohols against φ6 and PM2. Our findings suggest that the unsaturated monoglycerides and some of the unsaturated alcohols should be further studied as potential antiviral agents, particularly for application to herpesvirus-infected areas of the skin and accessible epithelium.

A comparison of abused children and their nonabused siblings.

Abstract: We compared 295 targets of abuse to 284 nonabused siblings with reference to birth record data and maternal perceptions of the birth and subsequent development of the child Prematurity; Apgar scores: age of mother at child's birth; self-reports of postpartum depression; maternal perceptions of emotional difficulties of the child, of the child's ability to be influenced by the mother, and of negative characteristics of the child reminiscent of others were related to certain types of abuse and gross neglect Explanatory hypotheses include weakened attachment bonds and maternal projection of negative attributes and feelings of helplessness

Feeding in water snakes: An electromyographic study

Abstract: Synchronized cinematography and electromyography were used to study feeding behavior in water snakes, Nerodia rhombifera and Nerodia fasciata. While these species swallow their prey by alternate movements of the right and left toothed bones of the skull, the muscles show bilateral asymmetric activity during each movement. Opening of one side of the mouth is initiated by protraction of the palatomaxillary arch and slight depression of the mandible. These movements serve to disengage the teeth from the surface of the prey and correlate with activity of the protractors of the palatomaxillary arch and quadrate. Continued opening results primarily from rotation of the braincase around its longitudinal axis. During the latter half of the opening phase, the rates of protraction of both palatomaxillary arch and mandible increase; this correlates with increased activity of the depressor mandibulae, several of the mandibular adductors and three of the four cervical muscles analyzed. The cervical muscles appear to restrain the prey during the fast segment of mouth opening when the toothed bones reach their maximum displacements from the surface of the prey. Closing of the mouth is initiated by rapid depression of the palatopterygoid joint which correlates with a cessation of activity of the levator pterygoidei. Immediately thereafter, the posterior end of the maxilla is depressed and slightly retracted and the mandible tends to be protracted and slightly adducted. These movements correlate with synchronized activity of the palato-maxillary protractors, the pterygoideus and the depressor mandibulae. The rest of the closing phase consists primarily of adduction and retraction of the palatomaxillary and mandibular elements relative to the braincase; the toothed bones remain fixed to the surface of the prey while the braincase is moved forward. EMGs indicate that the complex bone movements of the latter stage of mouth opening and the initial stage of mouth closing are dependent upon the simultaneous firing of a number of morphologically antagonistic muscles.

Cues that Elicit Ultrasounds from Adult Male Mice

Abstract: Adult male mice (Mus musculus) which have a prior history of experience with other adult male and adult female mice readily produce 70 kHz ultrasonic vocalizations in the presence of urine from adult females but not in the presence of urine from adult males. Urine from immatures of either sex does not elicit ultrasounds from socially experienced adult males. The ultrasound eliciting potency of adult male urine was not improved substantially following castration of adult males, injection of testosterone propionate to castrated adult males, administration of estradiol benzoate to castrated adult males, or neonatal castration. Ovarian hormones do not appear to be necessary for either the appearance at puberty, or the maintenance during adulthood, of the ultrasound eliciting cues of female urine. Stage of estrus did not have a major modulating effect on urinary cues eliciling male ultrasounds. Treatments that did not substantially reduce the signal value of adult female urine include ovariectomy before or after puberty, ovariectomy with adrenalectomy, and neonatal administration of testosterone. The administration of testosterone to ovariectomized adult females, and hypophyseclomy, virtually eliminated the ability of urine from adult females to elicit ultrasounds from socially experienced adult males. The implication of pituitary hormones in the modulation of female urinary cues thai elicit ultrasounds is particularly interesting since pituitary factors are also implicated in the proximal causation of postparturient maternal aggression, which adult male ultrasounds may function to moderate.

Bonded orthotropic strips with cracks

Abstract: In this paper the elastostatic problem for a nonhomogeneous plane which consists of two sets of periodically arranged dissimilar orthotropic strips is considered. It is assumed that the plane contains a series of collinear cracks perpendicular to the interfaces and is loaded in tension away from and perpendicular to the cracks. First the problem of cracks fully imbedded into the homogeneous strips is considered. Then the singular behavior of the stresses for two special crack geometries is studied in some detail. The first is the case of a broken laminate in which the crack tips touch the interfaces. The second is the case of cracks crossing the interfaces. An interesting result found from the analysis of the latter which may have an important bearing on a possible delamination fracture initiation at stress-free boundaries in bonded orthotropic materials is that for certain orthotropic material combinations the stress state at the point of intersection of a crack and an interface may be bounded whereas in isotropic materials at this point stresses are always singular. A number of numerical examples are worked out in order to separate the primary material parameters influencing the stress intensity factors and the powers of stress singularity, and to determine the trends regarding the influence of the secondary parameters. Finally, some numerical results are given for the stress intensity factors in certain basic crack geometries and for typical material combinations.

Effect of grafting on phase volume fraction, composition, and mechanical behavior: Epoxy/poly (n‐butyl acrylate) simultaneous interpenetrating networks

Abstract: Grafted simultaneous interpenetrating polymer networks (SINs) were prepared from Epon 828 epoxy resin and n-butyl acrylate monomer. The amount of grafting monomer (glycidyl methacrylate) was found to effect profound changes in the morphology and mechanical behavior of these materials. While the size of the dispersed rubbery phase increased from approximately 2 microns to 20 microns, the number of domains decreased, with increasing amounts of grafting agent. The total dispersed phase volume decreased with increased grafting. At the highest level of grafting, the two-phase morphology disappeared, and only one phase was observed. With increased grafting, dynamic mechanical spectroscopy showed a movement of the loss modulus peaks toward each other, confirming an increase in compatibility in the system and showing that the compositions in each phase were becoming more alike. The SIN with the most glycidyl methacrylate (3.0 percent) showed only one peak in the loss modulus curve, supporting the single phase morphology found through microscopy. At the point of compatibility between the two networks, the SIN supermolecular structure may be visualized as becoming one complex network, where the number of grafts between the two polymer chains outnumbers the number of homopolymer crosslinks. The chemical grafts were also shown to significantly alter the free energy of mixing of the two polymers. A grafting level-composition phase diagram showed that at well defined levels of grafting the free energy of mixing goes from a positive value to a negative value.

Transverse shear effect in a circumferentially cracked cylindrical shell

Abstract: The objectives of the paper are to solve the problem of a circumferentially-cracked cylindrical shell by taking into account the effect of transverse shear, and to obtain the stress intensity factors for the bending moment as well as the membrane force as the external load. The formulation of the problem is given for a specially orthotropic material within the framework of a linearized shallow shell theory. The particular theory used permits the consideration of all five boundary conditions as to moment and stress resultants on the crack surface. The effect of Poisson's ratio on the stress intensity factors and the nature of the out-of-plane displacement along the edges of the crack, i.e., bulging, are also studied.

Influence of monomer preemulsification on formation of particles from monomer drops in emulsion polymerization

Abstract: Evidence was obtained supporting the theory that monomer droplets can become a locus of initiation and propagation in emulsion polymerization. This was done by reducing the size of the monomer droplets prior to initiation of polymerization using different preemulsification techniques for a typical latex recipe containing a common anionic surfactant. Monomer droplet size reduction caused an increase in the total surface area of the monomer droplets and thereby increased the competitiveness of these droplets for capturing active free radicals which are generated in the aqueous phase. As the total surface area of the monomer droplets was increased by preemulsification, a corresponding increase in the number of large particles formed by polymerization of these monomer droplets was experimentally measured. This work shows that monomer droplets are a locus of emulsion polymerization. However, the importance of monomer droplet polymerization is limited by their total surface area because of the competition for free radicals with other surfaces and/or particle nucleation processes. The results offer a basis for explaining why broad, and sometimes bimodal, particle size distributions are obtained in some commercial processes where the reactants are preemulsified prior to being charged into a reaction vessel.

Fatigue Crack Growth in 2-1/4-Cr-1Mo Steel Exposed to Hydrogen Containing Gases

Abstract: Steels used in coal gasification vessels and piping (externals) can be exposed to mixtures of hydrogen, water vapor (steam), hydrogen sulfide, methane, carbon monoxide, carbon dioxide, and other gases at temperatures and pressures up to 600/sup 0/K and 10 MPa. Such mixtures, under certain operating conditions, can either enhance or inhibit crack growth in these steels. As a part of a program to identify thermodynamic conditions for this enhancement or inhibition, fatigue crack growth experiments have been carried out on a 2 1/4Cr-1Mo (ASTM A542, Class 2) steel in hydrogen, water vapor, and hydrogen sulfide at low pressures (below 133 kPa). The results indicate considerable enhancement of fatigue crack growth by some of these environments and also indicate that the apparent immunity of this material to stress corrosion cracking does not imply the same immunity to corrosion fatigue. The results will be discussed in terms of the influences of temperature, gas pressure and loading variables, and will be interpreted in terms of chemical reaction kinetics.

Enveloped Virus Inactivation by Fatty Acid Derivatives

Abstract: The enveloped bacteriophage φ6 has been shown to be a valuable model system for the preliminary screening of compounds that might be expected to inactivate herpes simplex virus and other enveloped mammalian viruses. A variety of fatty acid derivatives that form fluid micelles in aqueous media have been found to be potent inactivators of φ6. The chemical nature of the polar head group, the length of the alkyl chain(s), and the extent and geometry of unsaturation are all important parameters in determining the antiviral effectiveness of this class of compounds.

Fluidized-bed immobilized-enzyme reactor for the hydrolysis of cornstarch to glucose

Abstract: We have developed an economical fluidized-bed immobilized-enzyme cornstarch hydrolysis reactor employing an inexpensive glucoamylase-on-alumina (covalently bonded) catalyst having a high initial activity (130 units/g) and excellent long term stability (t1/2 = 6450 hr at 50°C). The reactor can give higher yields of dextrose from streams containing ∼30% (wt) low dextrose equivalent (DE) cornstarch than can a comparable fixed-bed reactor because its design exploits the fact that fluidixation permits the use of very small catalyst particles (down to 50μm in our case) which overcomes the yield-limiting diffusion-associated problems encountered in the use of conventional fixed-bed cornstarch hydrolysis reactors. Furthermore, even when small catalyst particles are used the fluidized-bed reactor does not suffer from plugging and high pressure drop problems typical of fixed-bed reactors. The results of an initial economic analysis based on bench-scale results indicate that the processing cost for a plant using this new technology to produce 100 × 106lb dextrose/year from low DE cornstarch would be as much as 33% lower than for a comparable plant employing conventional soluble-enzyme technology.