Showing papers by "Rensselaer Polytechnic Institute published in 1979"
TL;DR: For peraluminous melts and melts lying in the quartz-orthoclase-albite composition plane, less than 100 ppm Zr is required for zircon saturation as mentioned in this paper.
Abstract: Hydrothermal experiments were carried out at 2 kbar water pressure, 700 °–800 ° C, with the objective of determining the level of dissolved Zr required for precipitation of zircon from melts in the system SiO2-Al2O3-Na2O-K2O. The saturation level depends strongly upon molar (Na2O + K2O)/Al2O3 of the melts, with remarkably little sensitivity to temperature, SiO2 concentration, or melt Na2O/ K2O. For peraluminous melts and melts lying in the quartz-orthoclase-albite composition plane, less than 100 ppm Zr is required for zircon saturation. In peralkaline melts, however, zircon solubility shows pronounced, apparently linear, dependence upon (Na2O + K2O)/Al2O3, with the amount of dissolvable Zr ranging up to 3.9 wt.% at (Na2O + K2O)/Al2O3 = 2.0. Small amounts (1 wt.% each) of dissolved CaO and Fe2O3 cause a 25% relative reduction of zircon solubility in peralkaline melts. The main conclusion regarding zirconium/zircon behavior in nature is that any felsic, non-peralkaline magma is likely to contain zircon crystals, because the saturation level is so low for these compositions. Zircon fractionation, and its consequences to REE, Th, and Ta abundances must, therefore, be considered in modelling the evolution of these magmas. Partial melting in any region of the Earth's crust that contains more than ∼ 100 ppm Zr will produce granitic magmas whose Zr contents are buffered at constant low (< 100 ppm) values; unmelted zircon in the residual rock of such a melting event will impart to the residue a characteristic U- or V-shaped REE abundance pattern. In peralkaline, felsic magmas such as those that form pantellerites and comendites, extreme Zr (and REE, Ta) enrichment is possible because the feldspar fractionation that produces these magmas from non-peralkaline predecessors does not drive the melt toward saturation in zircon. Zircon solubility in felsic melts appears to be controlled by the formation of alkali-zirconosilicate complexes of simple (2:1) alkali oxide: ZrO2 stoichiometry.
564 citations
TL;DR: In this article, the hydration of soda-lime glass is studied using resonant nuclear reactions to measure the hydrogen and sodium profiles of hydrated glasses, and the measured hydration profiles are discussed in relationship to the Doremus model of interdiffusing ions.
Abstract: The hydration of soda-lime glass is studied using resonant nuclear reactions to measure the hydrogen and sodium profiles of hydrated glasses. The rate of growth of the surface layer of hydrated glass is initially proportional to the square root of time as is characteristic of diffusion controlled processes. After longer exposure a steady-state hydration profile is observed, which indicates that in addition to the diffusion controlled reaction there is a slow etching of the glass surface. The measured hydration profiles are discussed in relationship to the Doremus model of interdiffusing ions, which is found to be in good agreement with the data. This model is also discussed in relationship to measured hydration profiles of vacuum heated samples of hydrated glass.
281 citations
TL;DR: In this article, the so-called virtual mass force during the acceleration of a two-phase mixture was studied and it was shown that this interfacial force must be objective and invariant under a change of reference frame.
266 citations
TL;DR: In this paper, the process of determining appropriate constitutive equations for multidimensional time averaged two-phase flow equations is studied from the point of view of starting from general principles, and proceeding to specific constitutive equation which contain known physical effects.
225 citations
TL;DR: In this article, the effect of depositional processes on various parameters of the size-frequency distribution of sands has been investigated, and it has been shown that the distribution of particles in sands will be influenced by the conditions that determine what happens in the depositional environment, hence statistical parameters that define the sizefrequency distribution may be related to formative process.
Abstract: This address reminisces and reflects on a subject in which I have been involved for more than twenty years: the effect of depositional processes on various parameters of the size-frequency distribution of sands. Movements of air and water generally separate particles by their sizes; the distribution of sizes relates to (1) the availability of different sizes of particles in a parent material, (2) processes operating where the sediments are deposited, particularly the competency of flow, and (3) concentrations of particles in suspension. Differences in size-frequency distributions among sands correlate with various origins, that is with their terminal depositional environments. Reminiscences in this address express my personal experience, both its up and downs, in advocating the study of this relationship, particularly in applying the method of moments on the basis of the concept that one statistical function expresses the characteristics of the population of particles.
This address re-emphasizes some points made in previous studies (Friedman, 1961, 1962b, 1967) on the interrelationship between textural parameters and depositional processes for beach, dune, and river sands and then complements and supplements data which have not been presented before. These new data are grouped on scatter plots for sands of various origins. Finally, this address displays on maps regional trends of process-induced changes in size distributions of populations of particles in sands of four different settings: (1) a beach-dune setting, as exemplified by Padre Island, Texas, on the shores of the Gulf of Mexico; (2) a point-bar setting in the Arkansas River of Oklahoma; (3) a continental shelf-slope setting in the Gulf of Mexico off Louisiana, Mississippi, and Alabama; and (4) a continental shelf setting of the western Atlantic Ocean off New Jersey.
This address concludes with the observation that the distribution of particles in sands will be influenced by the conditions that determine what happens in the depositional environment, hence statistical parameters that define the size-frequency distribution may be related to formative process.
193 citations
TL;DR: The temperature dependence of the viscoelastic response was found to be thermorheologically complex, which implies that bone experiments must be done at body temperature to be relevant to the in vivo situation, and that time-temperature superposition is of questionable validity for bone.
174 citations
TL;DR: In this article, a sufficient condition for feedback stabilization for a semilinear control system is given and applications to hyperbolic boundary value problems are presented, where the condition is based on the assumption that the generator of a linear C0 semigroup of contractions on a Hilbert space is a nonlinear operator.
Abstract: This paper considers feedback stabilization for the semilinear control system\(\dot u(t) = Au(t) + \upsilon (t)B(u(t)).\) HereA is the infinitesimal generator of a linearC0 semigroup of contractions on a Hilbert spaceH andB : H → H is a nonlinear operator. A sufficient condition for feedback stabilization is given and applications to hyperbolic boundary value problems are presented.
163 citations
TL;DR: In this paper, a line-drawing method for quadric surfaces is described. Butler et al. used matrix algebra and parametric equations to compute intersections of two or three quadric surface surfaces.
161 citations
TL;DR: In this paper, the viscoplastic behavior of AISI Type 304 stainless steel was investigated by tensile tests at various strain-rates (10−8−10−2s−1), and by short-term creep and relaxation tests up to 5 h.
Abstract: T he spuniaxial viscoplastic behavior of AISI Type 304 stainless steel was investigated by tensile tests at various strain-rates (10−8−10−2s−1), and by short-term creep and relaxation tests up to 5 h. Instantaneous large changes in strain-rate were also performed during monotoniC and cyclic loading. A servocontrolled testing machine and displacement measurement on the specimen gage length were used for all tests. The results show significant rate-sensitivity, creep and relaxation. Test histories involving loading and unloading with positive loads up to 15% strain show that the relaxation behavior in the plastic range depends only on the strain-rate preceding the relaxation test and is independent of the strain magnitude. Also, the relaxation behavior is uniquely related to the stress changes corresponding to instantaneous large changes in the strain-rate during tensile tests. Completely reversed strain-controlled loading gradually changes the stress change/strain-rate change behavior. Annealed specimens and specimens loaded to a cyclic steady-state differ not only in their work-hardening characteristics but also in their rate-dependent behavior. In the cyclic steady-state, different hysteresis loops are traced for different strain-rates with fully reversible transitions from one hysteresis loop to another under strain-rate changes. These results support the notion that the viscoplastic behavior can be represented by piecewise nonlinear viscoelasticity.
159 citations
TL;DR: The definition of network medians is extended to the case where travel times on network links are random variables with known discrete probability distributions and the well known “facilities at nodes” theorems can be extended to such stochastic networks.
Abstract: The definition of network medians is extended to the case where travel times on network links are random variables with known discrete probability distributions. Under a particular set of assumptions, it is shown that the well known “facilities at nodes” theorems of Hakimi and of Levy can be extended to such stochastic networks. The concepts are further extended to the case of stochastic oriented networks. A particular set of applications, as well as mathematical programming formulations of the problem, are also discussed briefly.
159 citations
TL;DR: The results indicate that cells of flowering plants exhibit a heat-shock response similar to that observed in animal cells and at least some HSPs may not be due to activation of new genes.
Abstract: Tobacco (Nicotiana tabacum) and soybean (Glycine max) tissue culture cells were exposed to a heat shock and protein synthesis studied by SDS-polyacrylamide gel electrophoresis after labeling with radioactive amino acids. A new pattern of protein synthesis is observed in heat-shocked cells compared to that in control cells. About 12 protein bands, some newly appearing, others synthesized in greatly increased quantities in heat-shock cells, are seen. Several of the heat-shock proteins (HSPs) in both tobacco and soybean are similar in size. One of the HSPs in soybean (76K) shares peptide homology with its presumptive 25°C counterpart, indicating that the synthesis of at least some HSPs may not be due to activation of new genes. The optimum temperature for maximal induction of most HSPs is 39–40°C. Total protein synthesis decreases as heat-shock temperature is increased and is barely detectable at 45°C. The heat-shock response is maintained for a relatively short time in tobacco cells. After 3 hr at 39°C, a decrease is seen in the synthesis of the HSPs, and after 4 hr practically no HSPs are synthesized. After exposure to 39°C for 1 hr, followed by a return of tobacco cells to 26°C, recovery to the control pattern of synthesis requires greater than 6 hours. These results indicate that cells of flowering plants exhibit a heat-shock response similar to that observed in animal cells.
TL;DR: When Chinese subjects tried to name the color of characters which represented conflicting color words, they showed markedly greater interference than did English speaking readers performing an English version of the same task.
TL;DR: In this paper, the authors compared the theoretical excitation functions for heavy-ion induced reactions over a wide mass range with results calculated with a classical dynamical model based on the proximity nuclear potential of Blocki et al., the Coulomb potential of Bondorf et al.
TL;DR: In this article, a novel process was described for preparing dense, polycrystalline tricalcium phosphates, which achieved a compression strength of 687 MN m−2 and a tensile strength of 154 MNm−2.
Abstract: A novel process is described for preparing dense, polycrystalline tricalcium phosphates. Singleβ-phase compositional integrity is achieved by introducing catalytic amounts of sulphate ion and this pore free material has close to theoretical density. Preliminary mechanical properties include a compression strength of 687 MN m−2 and a tensile strength of 154 MN m−2. The relationship between processing variables and phase composition, microstructure, strength and translucence is described. The material has promise for bone implant applications.
TL;DR: A combined source-channel coding approach is described for the encoding, transmission and remote reconstruction of image data, resulting in a relatively robust design which is reasonably insensitive to channel errors and yet provides performance approaching the rate-distortion bound.
Abstract: A combined source-channel coding approach is described for the encoding, transmission and remote reconstruction of image data. The source encoder employs two-dimensional (2-D) differential pulse code modulation (DPCM). This is a relatively efficient encoding scheme in the absence of channel errors. In the presence of channel errors, however, the performance degrades rapidly. By providing error control protection to those encoded bits which contribute most significantly to image reconstruction, it is possible to minimize this degradation without sacrificing transmission bandwidth. The result is a relatively robust design which is reasonably insensitive to channel errors and yet provides performance approaching the rate-distortion bound. Analytical results are provided for assumed 2-D autoregressive image models while simulation results are described for real-world images.
TL;DR: In this paper, the effects of the insulating layer on barrier height and carrier transport are delineated by an activation energy analysis, and a capacitance anomaly consistently noticed in MIS Schottky barriers is resolved by stipulating a non-uniform interfacial layer.
Abstract: The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of GaAs metal-insulator-semiconductor (MIS) Schottky barrier diodes are investigated over a wide temperature range and compared with MS diodes. The effects of the insulating layer on barrier height and carrier transport are delineated by an activation energy analysis. Excess currents observed at low forward and reverse bias have also been analyzed and their cause identified. A capacitance anomaly consistently noticed in MIS Schottky barriers is resolved by stipulating a non-uniform interfacial layer, and a self-consistent model of the GaAs MIS Schottky barrier is developed by analyzing I-V and C-V data of both MIS and MS diodes.
TL;DR: The role of inhomogeneous deformation and molecular modes in collagen as viscoelastic mechanisms is considered and experimental evidence is discussed.
TL;DR: In this article, a method for designing laminated plates with orthotropic layers under uniaxial and biaaxial compression is presented. The objective is to find the fiber direction of all the layers that give the highest buckling stress; therefore, it is necessary to solve an unconstrained maximization problem.
Abstract: The paper presents a method for designing laminated plates with orthotropic layers under uniaxial and biaxial compression. The objective is to find the fiber direction of all the layers that give the highest buckling stress; therefore, it is necessary to solve an unconstrained maximization problem. The optimization technique used is Powell's conjugate direction method. Numerical calculations were made for plates with three, four, and six layers.
TL;DR: In this article, the authors give simple criteria for feedback stabilization in the case when (1.1) is bilinear, i.e., B linear, which is a consequence of both [20] and [24] that if the only solution of the uncontrolled system is O(1.ii(t)+Au (t)+p(t) B(u(t)) =O.
Abstract: ii(t)+Au(t)+p(t) B(u(t)) =O. Here A is a densely defined positive selfadjoint linear operator on a real Hilbert space H with inner product ( , ), B is a locally Lipschitz map from D(A”2) (endowed with the graph norm) into H, and p(t) is a real-valued control. The finite-dimensional stabilization problem H = IW” has been considered in the recent papers of Jurdjevic and Quinn [20] and Slemrod [24]. In the case when (1.1) is bilinear, i.e., B linear, these papers give simple criteria for feedback stabilization. Specifically, it is a consequence of both [20] and [24] that if the only solution of the uncontrolled system
TL;DR: In this paper, a closed-form analytical circuit model and a detailed computer-simulation model are used to obtain the output dc load line of the rectifier, and the efficiency degradation is nearly identical with series and parallel combining.
Abstract: Microwave power rectifiers have been developed previously with greater than 85-percent RF-to-dc conversion efficiency. To obtain useful power levels for proposed free-space microwave power transmission applications, numerous rectifier outputs are interconnected in series and/or parallel to share a common dc load. This work analyzes the resultant efficiency degradation when identical rectifiers operate at different RF power Ievels as caused by the power beam taper. Both a closed-form analytical circuit model and a detailed computer-simulation model are used to obtain the output dc load line of the rectifier. The efficiency degradation is nearly identical with series and parallel combining, and the closed-form analytical model provides results which are similar to the detailed computer-simulation model.
TL;DR: Diazepam will induce feeding in rats, which has a rather stable latency and does not wane with repeated doses, and naloxone hydrochloride inhibited the feeding induced by diazepam.
TL;DR: Throttling of freshwater inputs into the meromictic Dead Sea weakened the long-term stability of the water column, and complete overturn finally took place during the winter of 1978-1979.
Abstract: Throttling of freshwater inputs into the meromictic Dead Sea weakened the long-term stability of the water column. Between 1975 and 1978 successive deepenings of the pycnocline from 70 meters to beyond 200 meters were recorded. Complete overturn finally took place during the winter of 1978-1979. This unique process was accompanied by changes in the geochemistry of several components.
TL;DR: In this article, the authors investigate the problem of representing an arbitrary class of real functions f(·) in terms of their sampled values along the radius r and at equal angular increments of the azimuthal angle θ.
Abstract: We investigate the problem of representing an arbitrary class of real functions f(·) in terms of their sampled values along the radius r and at equal angular increments of the azimuthal angle θ. Two different bandwidth constraints on f(r,θ) are considered: Fourier and Hankel. The end result is two theorems which enable images to be reconstructed from their samples. The theorems have potential application in image storage, image encoding, and computer-aided tomography.
TL;DR: In this article, a nonlinear differential constitutive equation (E.R.Cernocky and E. K rempl, 1979a, b) is specialized to an overstress model.
Abstract: A previously proposed, uniaxial differential constitutive equation (E.R. C ernocky and E. K rempl , 1979a, b), nonlinear in the Cauchy stress and the engineering strain but linear in the stress and strain-rates, is specialized to an overstress model. It is shown by qualitative arguments that the solutions correspond to typical room-temperature viscoplastic behavior of AISI type 304 stainless steel. Two unknown coefficient functions are determined by extrapolation of room temperature relaxation data for this steel. The stiff first-order nonlinear differential equations are then numerically integrated for a variety of test histories. These include strain control with strain-rates from 10 −6 to 800s −1 , stress control with stressrates from 1.95 kPa s −1 to 19.5 MPa s −1 , instantaneous large changes in strain-rate and stress-rate, and partial unloading and reloading in strain and stress control and tension-tension cyclic creep. The computed results show good qualitative agreement with tests. Based on these results we consider that the model is a good representation of metal deformation behavior as long as the overstress does not change sign.
TL;DR: In this article, the photon absorption cross section by lead can be fitted from 35 to 106 MeV by a 12 year old modified quasi-deuteron model, with a damping factor D of 60 MeV.
TL;DR: Bigrams were processed by boys as shapes and by girls as words, which suggests a sexual dimorphism of brain functioning for bigrams and a relative specialization of the hemisphere for stereognostic processing is suggested.
Abstract: Children identified nonsense shapes by touch better with their left hand and words better with their right hand. Bigrams were processed by boys as shapes and by girls as words, which suggests a sexual dimorphism of brain functioning for bigrams. A relative specialization of the hemisphere for stereognostic processing is also suggested, since the accuracy of identification by both hands was greater than chance for all three types of stimuli.
TL;DR: The valid junction transitions provide a new set of edge semantics for line labeling and an ability to verify whether a given sequence of junctions forms a realizable configuration.
Abstract: A line and junction labeling scheme is introduced that is valid for both planar and curved-surface bodies. Seven generalized junction types are defined and shown to cover all valid projections for a wide class of planar and curved-surface bodies. It is further shown that there are limitations on the permissible junction types as one moves from one end of a line segment to the other. The valid junction transitions provide 1) a new set of edge semantics for line labeling and 2) an ability to verify whether a given sequence of junctions forms a realizable configuration.
TL;DR: In this article, the authors examined the implications of penalties for output not equalling demand by employing a general stochastic model for a firm facing an uncertain demand with a known probability density function.
Abstract: This paper examines some of the implications of introducing penalties for output not equalling demand by employing a general stochastic model for a firm facing an uncertain demand with a known probability density function. Several alternative objectives of the firm are considered: (1) maximization of expected profits; (2) maximization of the probability of achieving a particular target level of profits; and (3) maximization of target profits, given a target level of the probability of their being achieved. It is shown that the resulting probability density function of profits is not well defined. The shape and location of the function depend on the relative magnitudes of the model parameters and the output decision. Several important implications of this result for cost-volume-profit analysis are discussed.
TL;DR: A method of introducing general constraint equations into finite element matrix equations is described that requires no reordering or condensation of the equations, no large matrix operations, and no increase in the number of unknowns.
Abstract: A method of introducing general constraint equations into finite element matrix equations is described. The characteristics of the method are that it requires no reordering or condensation of the equations, no large matrix operations, and no increase in the number of unknowns. The method is suitable for application in minicomputer implementations of finite element analysis unless a large number of constraints is to be applied.