Showing papers by "Worcester Polytechnic Institute published in 1979"
TL;DR: In this article, a model of bandgap reduction in silicon through the stored electrostatic energy of majority-minority carrier pairs is developed and compared with experimental results in the doping range from 3 × 1017to 1.5 × 1020/cm3 at room temperature.
Abstract: A model of bandgap reduction in silicon through the stored electrostatic energy of majority-minority carrier pairs is developed and compared with experimental results in the doping range from 3 × 1017to 1.5 × 1020/cm3at room temperature. An analytic expression for the bandgap reduction in nondegenerate material is obtained \delta\epsilon _{g} = 3q^{2}/(16\pi \epsilon) \cdot (q^{2}n/\epsilon kT)1/2having a square-root dependence on the majority carrier concentration. At room temperature this becomes \delta\epsilon _{g} = 22.5 (n/10^{18})^{1/2} meV. In degenerate material, the bandgap reduction is independent of temperature, following the relationship \delta \epsilon _{g} = 162 (n/10^{20})^{1/6} meV. The experimental data at room temperature are in excellent agreement with this theory. Plots of bandgap narrowing as a function of doping level are presented for a number of temperatures.
160 citations
TL;DR: In this article, an isothermal metastable phase transformation diagram was developed for the Na-TPA system and a gismondine-like phase was added to the metastable phases coexisting with ZSM-5 and the crystallization sequence.
109 citations
TL;DR: In this article, the evolution of gamma-ray imaging is traced and a new gamma ray transverse section tomographic instrument is described which matches the favorable properties of wide-aperture focusing collimators to a form of the Radon equation which requires only angular averages of line integrals for reconstructions.
Abstract: The evolution of gamma-ray imaging is traced and a new gamma-ray transverse section tomographic instrument is described which matches the favorable properties of wide-aperture focusing collimators to a form of the Radon equation which requires only angular averages of line integrals for reconstructions. Single slice scans of less than 5 minutes are accomplished with amounts of radioactivity that are standard for procedures using gamma cameras.
50 citations
TL;DR: In this paper, the selective deuteration of 2.1 kN m −2 of a mixture containing 90% acetylene and 10% [ 14 C]ethylene in the presence of 8.4 kNm −2 deuterium gas was studied at 273 and 303 K over Pd black catalyst.
33 citations
TL;DR: In this paper, a frequency-response model applied to a series of idealized gas and liquid slugs yields a pulse propagation speed that approaches the homogeneous model value as the number of slugs is increased for a given void fraction.
Abstract: The simple model of pressure pulse propagation in slug flow proposed by Henry, Grolmes, and Fauske has been extended by considering wave reflection and wave transmission at gas-liquid interfaces. A frequency-response model applied to a series of idealized gas and liquid slugs yields a pulse propagation speed that approaches the homogeneous model value as the number of slugs is increased for a given void fraction. All characteristic roots from the solution to a three-equation drift-flux model are related to the velocity of the center of mass of the mixture. The pulse propagation speed relative to this velocity is exactly equal to the homogeneous model value, however. Measured pulse propagation speeds in vertically downward slug flow are, as anticipated, much less than those predicted by the simple model of Henry, Grolmes, and Fauske, but slightly greater than the homogeneous model value. Measured pressure surges produced by the rapid closure of a downstream valve in a pipeline are reasonably well predicted by the drift-flux model. For the range of void fractions, pressures, and velocities encountered in this study, it is concluded that pressure pulse speeds and the magnitude of pressure surges in slug flow can be adequately predicted by a homogeneous model.
33 citations
TL;DR: In this paper, a model for treatment of surfaces using nonrectangular patches is presented, and the results are shown to be reasonable even in cases where some of the quadrilaterals degenerate to triangles.
Abstract: A model is derived for treatment of surfaces using nonrectangular patches. Tests show good agreement, where comparison is possible, with results published elsewhere. The results are shown to be reasonable even in cases where some of the quadrilaterals degenerate to triangles.
29 citations
23 citations
TL;DR: Methods for nuclear transfer and fusion of individual viable nuclei into cells is described and Experimental binucleates have been formed by fusing nuclei from normal fibroblasts, SV40 virus-transformed fibro Blasts, and HeLa carcinoma cells into individual diploid fibroBlasts.
Abstract: Methods for nuclear transfer and fusion of individual viable nuclei into cells is described. Experimental binucleates have been formed by fusing nuclei from normal fibroblasts, SV40 virus-transformed fibroblasts, and HeLa carcinoma cells into individual diploid fibroblasts which have undergone their total “life span” (population doublings) and have been maintained in culture for a period of 10–12 weeks (late phase III) prior to the nuclear transfer. Many of the cells receiving additional nuclei replicate and form clones of cells with a limited life span, and the morphology of the cells remains fibroblast-like.
23 citations
TL;DR: Scanning electron microscopy revealed quantitative differences in both surface characteristics and spreading behavior of young and senescent WI38 human diploid fibroblasts, and suggested the importance of that structure in the phenomena of senescence.
21 citations
TL;DR: It is demonstrated that for a given voltage electrode separation, the proximity of the current electrodes determines the relative sensitivity to conductivity changes within the sampling field, a possibility which should aid the design of electrode configurations for specific applications of impedance plethysmography.
Abstract: Impedance plethysmography has been widely used clinically because of its convenience and sensitivity, but its use has been questioned by some investigators because of uncertainty concerning the source of the signal. Quantitative definitions of the sensitivity to conductivity changes as a function of position have been lacking. The present study defines the sampling efficiency for impedance measurements made with four electrodes on a uniform cylinder model of the calf. Predictions based on electric field theory compare favorably with results from an in vitro model (average rms error = 8 percent). These studies demonstrate that for a given voltage electrode separation, the proximity of the current electrodes determines the relative sensitivity to conductivity changes within the sampling field. For voltage and current electrode separations of 10 and 18 cm on a 37 cm circumference calf (typical measurements for clinical testing of the lower leg), the sampling field extends about 3 cm beyond the voltage electrodes and the deep vessels are sampled with at least 80 percent of the efficiency of the superficial vessels. These studies also indicate that it is possible to predict the sampling field associated with various electrode configurations, a possibility which should aid the design of electrode configurations for specific applications of impedance plethysmography.
18 citations
06 Nov 1979
TL;DR: It is shown that for small target perturbations the 2-D tracking problem may be approximated as a 1-D time-varying parameter estimation problem.
Abstract: The development of algorithms for real-time, automatic systems capable of tracking 2-D targets in complex scenes is discussed. The problems and constraints involved in such an undertaking as well as previous efforts are summarized. in addition, a mathematical model of scene spatial and temporal evolution is developed for certain classes of targets and target perturbations. It is shown that for small target perturbations the 2-D tracking problem may be approximated as a 1-D time-varying parameter estimation problem. Algorithms resulting from several estimation approaches are discussed.
TL;DR: A cyanobacterium (WPI-I) and cyanelles of Glaucocystis nostochinearum Itz, have been introduced into epidermal cells of Allium cepa and Daucus carota L. cv.
Abstract: A cyanobacterium (WPI-I) and cyanelles of Glaucocystis nostochinearum Itz, have been introduced into epidermal cells of Allium cepa L. cv. Downing Yellow Globe bulb scales by microinjection. Uptake of cyanelles into protoplasts of Allium cepa and Daucus carota L. cv. Imperator 58 has also been induced with polyethylene glycol. Protoplasts were cultured until new cell walls were synthesized.
01 Jan 1979
TL;DR: In this article, the authors describe the comparison theorems for systems of reaction-diffusion equations and present a particular application of a general method for obtaining comparison problems with the appropriate monotonicity properties.
Abstract: Publisher Summary This chapter describes the comparison theorems for systems of reaction–diffusion equations. Comparison theorems for systems of parabolic differential inequalities are useful tools for the qualitative analysis of the behavior of reacting systems. The chapter presents a particular application of a general method for obtaining comparison problems with the appropriate monotonicity properties. Bounding theorems used to study certain population models are, in fact, neither limited to spatially independent bounding problems nor to Neumann boundary data. Invariance results for such systems may be regarded as consequences of comparison theorems rather than the converse. The chapter describes a problem of nondimensionalized version of a prototype combustion problem proposed by Frank–Kamenetzky. The nonlinear terms in such a model cannot possibly be quasimonotone because temperature and species concentration must feed back upon one another in contrary ways.
TL;DR: A direct relationship exists between the expression of these proteins and the proliferative state of the culture and the urea extractable cell surface proteins were found to be present in increased amounts in transformed fibroblasts.
Abstract: The urea extractable cell surface proteins of WI-38 human embryonic fibroblasts and SV-40 transformed WI-38 fibroblasts were examined. Electrophoretic analysis on 5.6% SDS polyacrylamide gels revealed 10–15 discrete protein bands. Three of these bands, of molecular weight 50,000, 45,000 and 30,000 daltons, were found to be present in increased amounts in transformed fibroblasts. The expression of these proteins decreased with increasing culture age. Thus a direct relationship exists between the expression of these proteins and the proliferative state of the culture.
TL;DR: In this paper, the change in performance of induction warthour meters when measuring integral-cycle-controlled resistance loads was studied and a simple mathematical model was used to explain the main cause for error.
Abstract: The change in performance of induction watthour meters when measuring integral-cycle-controlled resistance loads was studied. A simple mathematical model is used to explain the main cause for error. Test results for representative meters show that meters on integral cycle speed up, resulting in substantial positive errors. When mixed loads are monitored, the error becomes small and within commercially acceptable limits.
TL;DR: A population balance model of fish population dynamics for batch systems was developed, and a growth rate expression was introduced and coupled with the population balance, illustrating that conditions conducive to high growth rates also resulted in broadening of size distributions.
TL;DR: During unsupervised exercise for cardiac rehabilitation or conditioning, it is desirable to reach and maintain a predetermined heart rate (without overshooting) selected according to age, health, and cardiac status of the patient.
Abstract: During unsupervised exercise for cardiac rehabilitation or conditioning, it is desirable to reach and maintain a predetermined heart rate (without overshooting) selected according to age, health, and cardiac status of the patient. Because there is no simple and inexpensive heart rate controller, most exercise protocols are specified in terms of patient work load-often speed and torque of a stationary bicycle. In these protocols the actual heart rate achieved will depend on the patients physical condition and fatigue as the exercise progresses.
TL;DR: Da aus 100 g lufttrockenem Bentonit nach Eintausch und Vakuumtrocknung 93,4 g S-Benzyl-tetrahydrothiophenium-Bentonit erhalten werden, verffigt der zur Reaktion eingesetzte BentonIt fiber einen SulfoniumIonengehalt von 71,2 mMol/100 g.
Abstract: Den Verlauf der SN-Reaktionen untersuchten wir in Abh/ingigkeit yon Temperatur und Zeit (Fig. 1). Die Eintauschkapazit/it des Na-Bentonits wurde zu 66,5 mMol Kationen/100 g lufttrockenem Na-Bentonit bestimmt [4]. Da aus 100 g lufttrockenem Bentonit nach Eintausch und Vakuumtrocknung (130 ~ 0,05 Torr, Gewichtskonstanz) 93,4 g S-Benzyl-tetrahydrothiophenium-Bentonit erhalten werden, verffigt der zur Reaktion eingesetzte Bentonit fiber einen SulfoniumIonengehalt von 71,2 mMol/100 g.
TL;DR: The photo-ring contraction of 50 percent H2SO4 cations was studied in this paper, where Dihydroxycyclopentenones were intermediates in these reactions. But the results were limited.
TL;DR: The triplet state zero-field splitting parameters and intersystem crossing (ISC) decay constants for the individual triplet spin sublevels of magnesium tetraphenylchlorin and magnesium porphin dissolved in pyridine are presented in this article.
TL;DR: In this paper, the authors generalize the theory of Reuter and Sondheimer for the anomalous skin effect in metals to take into account the motion of the lattice and develop a procedure for the calculation of the conversion efficiency of electromagnetic to acoustic energy when the electrons are scattered diffusely by the surface of the metal.
Abstract: The usual theory of direct ultrasonic generation by electromagnetic radiation in metals is based on the assumption that the conduction electrons experience specular scattering at the boundary of the metal. The present study generalizes the theory of Reuter and Sondheimer for the anomalous skin effect in metals to take into account the motion of the lattice. We develop a procedure for the calculation of the conversion efficiency of electromagnetic to acoustic energy when the electrons are scattered diffusely by the surface of the metal. The results show that this efficiency is comparable in the two cases of specular and diffuse scattering. For example, for metallic potassium under the conditions of the experiments by Chimenti et al. (incident radiation of frequency equal to 9 MHz and electron mean free path of the order of 1.4 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}2}$ cm) we find that the ratio of acoustic to electromagnetic fluxes is 4.5 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}12}$ for specular scattering and 4.7 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}12}$ for diffuse scattering.
TL;DR: A technique for the statistical analyses of errors in the forecasts produced by econometric forecasting models is described and applied to a realistic model for annual electric energy sales.
Abstract: A technique for the statistical analyses of errors in the forecasts produced by econometric forecasting models is described and applied to a realistic model for annual electric energy sales The technique considers uncertainties in the model parameters as well as in the exogenous (input) variables
TL;DR: In this paper, measurements of Zircaloy-steam oxidation kinetics on as-received and preoxidized cladding are reported, as well as measurements of the inside to outside diameter oxygen ratio following rupture of simulated fuel rods.
Abstract: Measurements of Zircaloy-steam oxidation kinetics on as-received and preoxidized cladding are reported, as are measurements of the inside to outside diameter oxygen ratio following rupture of simulated fuel rods. The kinetics data confirm the conservative nature of the Baker-Just equation and suggest that preoxidation effects would provide an additional element of conservatism in regard to the amount of oxidation that would be expected if a fuel rod were subjected to a pressurized water reactor (PWR)-type temperature transient. Although a great deal of scatter was found in the measured inside-outside diameter oxygen ratios, the average value even at the rupture position was less than unity. The strongest trends showed a decreasing inside-outside diameter oxygen ratio with decreasing test time and increasing distance from the rupture site. It was found that differences in values of published oxidation kinetics parameters can be reconciled if the procedure used to heat the test specimens is taken into account. A regression analysis of data reported from seven recent investigations showed that the activation energy for the oxidation process was about 7.6 kcal/mole less in experiments using internally heated specimens than in experiments using externally heated specimens. Similar effects are also seen in inside-outside diameter oxygen ratio data; values from externally heated specimens are larger than those from internally heated specimens.
01 Jan 1979
TL;DR: In this paper, a co-axial, ducted, turbulent, diffusion flame was mapped in terms of static pressure, impact pressure, and chemical composition, and the data set was used for evaluation of models of turbulent diffusion flames.
Abstract: With the objective of providing a data set for evaluation of models of turbulent diffusion flames, a co-axial, ducted, turbulent, diffusion flame was mapped in terms of static pressure, impact pressure, and chemical composition. From these data velocity components, densities, turbulent exchange coefficients, and reaction rates of O 2 , C 3 H 8 , CO, CO 2 , H 2 O, H 2 , CH 4 , and C 2 H x were computed. The overall fuel equivalence ratio of the flame was 0.615; the fuel and air entrance velocities were approximately equal at 13 m/s; and the overall heat release rate in the region studied was 50×10 6 j/(m 3 s). Soot formation was found to be negligible, and the mixing similarity principle of Browne and Powell was used in obtaining results. The maximum rate of oxygen consumption was found to be in regions of the flame where the equivalent unburned composition was either fuel rich or near stoichiometric. The rates of oxygen consumption are markedly less than for comparable premixed propane-air flames or hydrogen-air diffusion flames. It was found that the mol fraction of water and the sum of the mol fractions of CO and CO 2 were correlated with the mol fraction of oxygen. Only the principal results are summarized herein. The full data set is available elsewhere.
TL;DR: In this paper, the surface acidities of Na-Y zeolites were determined by means of n-butylamine titration in benzene using Hammett indicators in the range Ho: +68 to Ho: −82.
Abstract: Surface acidities of CeIII, CeIV and [CeIII, CeIV] containing Na-Y zeolites were determined by means of n-butylamine titration in benzene using Hammett indicators in the range Ho: +68 to Ho: −82 Total acidites of CeIVNaY zeolites until 51% CeIV exchange were found to be small (≤080 mequ/g at Ho: +68) but formed preferably strong acidic centers (Ho: −56) even at low degrees of exchange CeIIINaY displayed an acidity pattern similar to that which is known from lanthanum exchanged NaY faujasites under the same pretreatment conditions
TL;DR: In this article, concepts of n-person cooperative game theory are used to develop quantitative measures of equity and stability, which are incorporated into linear programming models that allow explicit equity-stability tradeoffs to be made in distributing the costs of the least-cost regional service plan.
Abstract: Regional systems to provide urban services must be designed not only on the basis of cost effectiveness but also with regard to a proper distribution of costs among the participants. The cost distribution should be equitable and stable (in the sense that incentives for groups to break away and form separate systems are minimized). Concepts of n-person cooperative game theory are utilized to develop quantitative measures of equity and stability. These measures are incorporated into linear programming models that allow explicit equity-stability tradeoffs to be made in distributing the costs of the least-cost regional service plan. Examples that demonstrate the use of the methods are provided.