Showing papers by "Georgia Institute of Technology published in 1968"
375 citations
TL;DR: The detailed allocation method of system reliability discussed in this paper is designed to select the optimal solution in the context of the trade-off analysis.
Abstract: The detailed allocation method of system reliability discussed in this paper is designed to select the optimal solution in the context of the trade-off analysis. It is noted that the problem may be structured as an n-stage sequential decision problem. A computational algorithm is developed using dynamic programming.
343 citations
117 citations
74 citations
TL;DR: In this article, methods for preparing pure magnesium and beryllium alkyls, aryls, and halides have been investigated and evaluated, and some previously reported methods were found to produce impure products whereas one method for each class of compounds was found that produced an unusually pure product.
65 citations
TL;DR: In this article, a drift-tube mass spectrometer at room temperatures was used to measure the transport parameters of low-energy mass-identified ions in the gas and to determine ion-molecule reaction rates.
Abstract: Measurements of transport parameters of low-energy mass-identified ions in ${\mathrm{H}}_{2}$ and ${\mathrm{D}}_{2}$ gases have been made in a drift-tube mass spectrometer at room temperatures. In addition, the variable drift distance of this apparatus has been used to vary the residence time of the ions in the gases to determine ion-molecule reaction rates. The zero-field reduced mobilities of ${\mathrm{H}}^{+}$ and $\mathrm{H}_{3}^{}{}_{}{}^{+}$ in ${\mathrm{H}}_{2}$ were found to be 15.7 \ifmmode\pm\else\textpm\fi{} 0.6 and 11.1 \ifmmode\pm\else\textpm\fi{} 0.5 ${\mathrm{cm}}^{2}$/V sec, respectively. Those for ${\mathrm{D}}^{+}$ and $\mathrm{D}_{3}^{}{}_{}{}^{+}$ in ${\mathrm{D}}_{2}$ were found to be 11.2 \ifmmode\pm\else\textpm\fi{} 0.5 and 8.0 \ifmmode\pm\else\textpm\fi{} 0.3 ${\mathrm{cm}}^{2}$/V sec, respectively. The zero-field reduced mobilities for ${\mathrm{Li}}^{+}$, ${\mathrm{Na}}^{+}$, and ${\mathrm{K}}^{+}$ ions in ${\mathrm{H}}_{2}$ were measured to be 12.3 \ifmmode\pm\else\textpm\fi{} 0.6, 12.2 \ifmmode\pm\else\textpm\fi{} 0.6, and 12.8 \ifmmode\pm\else\textpm\fi{} 0.6 ${\mathrm{cm}}^{2}$/V sec. The zero-field reduced mobilities for these same alkali ions in ${\mathrm{D}}_{2}$ were measured to be 9.6 \ifmmode\pm\else\textpm\fi{} 0.5, 8.9 \ifmmode\pm\else\textpm\fi{} 0.4, and 9.4 \ifmmode\pm\else\textpm\fi{} 0.5 ${\mathrm{cm}}^{2}$/V sec, respectively. The mobilities of ${\mathrm{H}}^{+}$, $\mathrm{H}_{3}^{}{}_{}{}^{+}$, ${\mathrm{Li}}^{+}$, ${\mathrm{Na}}^{+}$, and ${\mathrm{K}}^{+}$ in ${\mathrm{H}}_{2}$ were found to be related to the mobilities of ${\mathrm{D}}^{+}$, $\mathrm{D}_{3}^{}{}_{}{}^{+}$, ${\mathrm{Li}}^{+}$, ${\mathrm{Na}}^{+}$, and ${\mathrm{K}}^{+}$ in ${\mathrm{D}}_{2}$, respectively, by the appropriate ratios of the square roots of the reduced masses in each case, as predicted by Langevin's theory. However, the mobilities within either set of ions in a given gas did not follow the ${{M}_{r}}^{\frac{\ensuremath{-}1}{2}}$ reduced mass dependence. The three-body reaction rate coefficients for the reactions ${\mathrm{H}}^{+}$ + 2${\mathrm{H}}_{2}$ \ensuremath{\rightarrow} $\mathrm{H}_{3}^{}{}_{}{}^{+}$ + ${\mathrm{H}}_{2}$ and ${\mathrm{D}}^{+}$ + 2${\mathrm{D}}_{2}$ \ensuremath{\rightarrow} $\mathrm{D}_{3}^{}{}_{}{}^{+}$ + ${\mathrm{D}}_{2}$ were found to be (3.2 \ifmmode\pm\else\textpm\fi{} 0.3) and (3.0 \ifmmode\pm\else\textpm\fi{} 0.4) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}29}$ ${\mathrm{cm}}^{6}$/sec, respectively, and were observed to be independent of $\frac{E}{N}$ in the thermal range ($\frac{E}{N}l28\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}$ V ${\mathrm{cm}}^{2}$) and independent of the gas pressure from 0.1 to 0.6 Torr. A classical calculation shows that the assumption of Langevin-type spiraling collisions between the ions and gas molecules does not yield collision times long enough to account for the large three-body rate coefficients measured. Finally, a few measurements of the radial diffusion coefficient for $\mathrm{H}_{3}^{}{}_{}{}^{+}$ ions in ${\mathrm{H}}_{2}$ have been made, and they agree with those reported by Dutton et al., within the scatter in the data, but not with those reported by Skullerud.
64 citations
TL;DR: The drift velocities of mass-identified ions in hydrogen gas at room temperature were measured in this paper, and the reduced zero-field mobilities were deduced from these measurements, which introduced no ambiguity in ascribing the above zero field mobilities to single ionic species.
Abstract: The drift velocities of mass-identified $\mathrm{H}_{3}^{+}$ and ${\mathrm{H}}^{+}$ ions in hydrogen gas at room temperature were measured. The $\mathrm{H}_{3}^{+}$ ions were found to be in thermal equilibrium with the gas at $\frac{E}{{p}_{0}}$ less than about 10 V/cm Torr; the ${\mathrm{H}}^{+}$ ions, at $\frac{E}{{p}_{0}}$ less than about 5 V/cm Torr. From these measurements, the reduced zero-field mobilities were deduced: $\mathrm{H}_{3}^{+}$, 11.1\ifmmode\pm\else\textpm\fi{}0.6 ${\mathrm{cm}}^{2}$/V sec; ${\mathrm{H}}^{+}$, 16.0\ifmmode\pm\else\textpm\fi{}0.8 ${\mathrm{cm}}^{2}$/V sec. This investigation was performed with a long, low-pressure drift tube using a pulsed time-of-flight technique. The arrival-time histograms presented evidence of hydrogen ion-molecule reactions. It is shown that these reactions introduce no ambiguity in ascribing the above zero-field mobilities to single ionic species. Only a negligible fraction of the detected $\mathrm{H}_{3}^{+}$ ions were formed by the three-body conversion of ${\mathrm{H}}^{+}$ into $\mathrm{H}_{3}^{+}$. Above an $\frac{E}{{p}_{0}}$ of about 54 V/cm Torr, the disruption of $\mathrm{H}_{3}^{+}$ ions contributes substantially to the ${\mathrm{H}}^{+}$ signal. The reactive formation of $\mathrm{H}_{5}^{+}$ from $\mathrm{H}_{3}^{+}$ was evident in the $\mathrm{H}_{5}^{+}$ arrival-time histograms. The zero-field mobility of potassium ions in hydrogen was also determined, and the close agreement with the data of other investigators demonstrates that the apparatus is relatively free of unknown systematic uncertainties.
60 citations
55 citations
TL;DR: In this article, the Auger spectra resulting from low energy electron bombardment have been used to study the electronic structure in the surface region of graphite using a retarding grid technique, and the results are compared with the previous work of Hagstrum on ion neutralization spectroscopy.
48 citations
TL;DR: In this article, the surface plasmon loss peak was identified in the copper energy loss spectrum from its intensity dependence on the dielectric constant at the surface, which implies that the d-electrons in copper do participate in the plasma oscillation.
41 citations
TL;DR: In this article, nonlinear combustion instability in liquid propellant rocket engines, describing nonsteady combustion process with aid of Crocco time lag hypothesis, is described with the aid of the Croccco-time lag hypothesis.
Abstract: Nonlinear combustion instability in liquid propellant rocket engines, describing nonsteady combustion process with aid of Crocco time lag hypothesis
TL;DR: In this article, experiments performed on elastic, complete spherical shells of large radius-to-thickness ratio, pressure and volume-displacement instrumentation and photography were used to study postbuckling behavior.
Abstract: In experiments performed on elastic, complete spherical shells of large radius-to-thickness ratio, pressure and volume-displacement instrumentation and photography were used to study postbuckling behavior. Photographs of a number of the distinct modes observed are presented.
TL;DR: In this paper, a synchronous machine with a fault in its armature winding is represented by an equivalent circuit in three symmetrical components, and the line and neutral terminals of the equivalent circuit are connected to a system network in each sequence.
Abstract: A synchronous machine with a fault in its armature winding may be represented by an equivalent circuit in three symmetrical components. The line and neutral terminals of the equivalent circuit are connected to a system network in each sequence. The fault point of the positive sequence is connected to the neutral of the negative sequence, and so forth, representing a single phase- to-ground, or turn-to-turn, fault. Electromotive forces behind the corresponding reactance are introduced in every branch of the positive-sequence network of the faulty machine and an equivalent electromotive force of the system is considered. The resulting network consists of three loops with four electromotive forces. The calculation of the current flow in this network is programmed for solution on the IBM-7090 digital computer.
TL;DR: In this paper, coupled oscillations of sloshing liquid in elastic rectangular and cylindrical tank, noting frequency changes due to level and container configuration were reported. But the authors did not specify the level and the container configuration.
Abstract: Coupled oscillations of sloshing liquid in elastic rectangular and cylindrical tank, noting frequency changes due to level and container configuration
TL;DR: Quinol-clathrates of Kr and Xe were used as solid target powders for neutron activation and cross sections for 16 (n 2n), 7 (n, p), and one reaction at 14.4±0.3 MeV have been measured; of these, 23 cross sections are reported for the first time as discussed by the authors.
01 Jan 1968
TL;DR: In this paper, the problem of partially filling a cylindrical tank with rigid side walls and a flat flexible bottom is investigated, where the liquid is assumed to be inviscid, homogeneous and incompressible.
Abstract: The problem of hydroelastic sloshing of a liquid, partially filling a cylindrical tank with rigid side walls and a flat flexible bottom, has been investigated. The liquid is assumed to be inviscid, homogeneous and incompressible; the flexible bottom is assumed to be a stretched membrane. An approximate solution is given and numerical examples are discussed. The data obtained show good agreement with experimental results reported by other authors.
TL;DR: In this paper, a tabulation of relative dielectric constant and loss tangent is presented for a number of common materials, using an interference spectrometer to measure insertion loss and phase shift.
Abstract: A tabulation of relative dielectric constant and loss tangent is presented for a number of common materials. Measurements were made by using an interference spectrometer to measure insertion loss and phase shift of dielectric samples.
TL;DR: Two proteolytic strains of Clostridium botulinum type F have been isolated from crabs from the York River in Virginia for the first time and the first demonstration of the presence of type F on the eastern coast of the United States.
Abstract: Two proteolytic strains of Clostridium botulinum type F have been isolated from crabs (Callinectes sapidus) from the York River in Virginia. This is the first time proteolytic strains of this type have been isolated in the United States and the first demonstration of the presence of type F on the eastern coast of the United States.
TL;DR: In this article, a dark zone pattern which is asymmetric with respect to the overall crystallographic pattern is shown to be related to the orientation of the ordered β structure with relative to the disordered face-centred cubic α structure.
Abstract: Field ion images from ordered Ni4Mo with He and He–Ne mixtures are very stable and contain a variety of interesting crystallographic features. Translational antiphase boundaries are readily identified because of the layered structure of Ni4Mo and the prominence of the Mo atoms in the images. Although the Ni atoms do not image readily they are faintly visible on certain superlattice planes where they occur in layers. A dark zone pattern which is asymmetric with respect to the overall crystallographic pattern is shown to be related to the orientation of the ordered β structure with respect to the disordered face-centred cubic α structure.
TL;DR: This work has shown thatFerroelectrics, which display dielectric hysteresis, are characterized by the presence of spontaneous dipole moments which can be oriented by the application of electric fields to the material.
Abstract: RECENT experiments have implied an intimate association of ribonucleic acid (RNA) in the memory processes of platyhelminths and in mammals1–3. It is therefore of interest to determine any physical, as well as chemical or physiological, properties that pertain to mechanisms of information storage. Hysteresis is a phenomenon that permits a material in which this property is inherent to maintain a physical state dependent on the history of the material. Ferroelectrics, which display dielectric hysteresis, are characterized by the presence of spontaneous dipole moments which can be oriented by the application of electric fields to the material. In such a material, the state of polarization represents a memory of its electrical history.
TL;DR: Digital computer predictions of aperture antenna patterns are shown to be far more complete, in terms of information concerning the field vectors over virtually unrestricted angular sectors and even at short distances, when vector rather than scalar diffraction theory is applied.
Abstract: Digital computer predictions of aperture antenna patterns are shown to be far more complete, in terms of information concerning the field vectors over virtually unrestricted angular sectors and even at short distances, when vector rather than scalar diffraction theory is applied.
TL;DR: In this article, a single-wire proportional counter containing the gaseous source was used to measure the capture ratio in the decay of 35-day ODEs in the presence of variable paralysis times, 2.0 and 3.8 msec.
Abstract: The ratio of $M$- to $L$-orbital electron capture in the decay of 35-day ${\mathrm{Ar}}^{37}$ has been measured in a single-wire proportional counter containing the gaseous source. This counter was operated with variable paralysis times, 2.0 and 3.8 msec being used in the present experiments to minimize the contribution from afterpulses. Recent investigations of the pulse-height distribution from proportional counters due to single-and multiple-electron events make it possible to measure single-electron spectra down to essentially zero energy with much greater accuracy than heretofore. The experiment was undertaken because of the considerable disagreement between experimental and theoretical $\frac{M}{L}$ capture ratios, particularly in the low-$Z$ region. A survey of all experimental work on $M$ capture is included for comparison with available theoretical results. In the decay of ${\mathrm{Ar}}^{37}$ the experimental value for the $\frac{M}{L}$ capture ratio is $\frac{{P}_{M}}{{P}_{L}}={{0.104}_{\ensuremath{-}0.003}}^{+0.006}$, where the error limits have been subjected to careful detailed analysis. From this result, a value of ${k}_{\ensuremath{\alpha}}=0.980\ifmmode\pm\else\textpm\fi{}0.015$ for chlorine was determined, where ${k}_{\ensuremath{\alpha}}$ is the fraction of ${K}_{\ensuremath{\alpha}}$ x rays in the $K$ series of chlorine. The theoretical predictions of Bahcall for $\frac{{P}_{M}}{{P}_{L}}$ lie about 23% above the experimental point, for a theory with exchange correction. The older theoretical value due to Wapstra et al. is in no better agreement with experiment, even if a correction for exhange is applied. An intensive effort is reported to measure the $\frac{L}{K}$ capture ratio in the decay of 53.5-day ${\mathrm{Be}}^{7}$, as gaseous ${({\mathrm{C}}_{2}{\mathrm{H}}_{5})}_{2}$${\mathrm{Be}}^{7}$ in the single-wire proportional counter, but owing to the low energy of the $K$-capture events (55 eV) and very low counting statistics, this measurement appears to be beyond the present state of the proportional-counter art.
TL;DR: In this article, the application of lossy line filters in cascade with and integrated into conventional reactive filters is discussed, and a significant size reduction of conventional transmission line reactive filters can also be realized along with the reduction of spurious passbands by combining a lossy dielectric with the conventional reactive elements.
Abstract: Reactive bandpass and low-pass filters often exhibit spurious responses in the frequency region above the design passband. The spurious responses limit the effectiveness of the filter in preventing interference by out-of-band signals. A simple and inexpensive technique for reducing or eliminating these passbands is to add short sections of an appropriate lossy transmission line in series with the conventional filter. A significant size reduction of conventional transmission line reactive filters can also be realized along with the reduction or elimination of spurious passbands by combining a lossy dielectric with the conventional reactive elements. This paper discusses the application of lossy line filters in cascade with and integrated into conventional reactive filters. The design of lossy transmission line sections and wide-band impedance matching techniques are described.
TL;DR: The role of Mg as a reversible-vacancy trap is also established in this article, where changes in Guinier-Preston (G-P) zone size are observed to follow the same pattern as changes in hardness.
Abstract: Small-angle X-ray scattering techniques and hardness measurements have been used to study preprecipitation in two Al/Zn/Mg alloys containing the same Zn content (2.46 at. %) but different Mg contents. Changes in Guinier-Preston (G-P) zone size are observed to follow the same pattern as changes in hardness. It is also observed that a critical zone size is required for the nucleation of the intermediate precipitate,η∼'; the size being dependent on the Mg content. The role of Mg as a reversible-vacancy trap is also established.
TL;DR: Measurements of the initial slope of the Feulgen hydrolysis curve under various conditions of preparation, temperature, and acid concentration demonstrate that this slope has the kinetic properties of the reaction rate of a simple hydrolytic reaction.
Abstract: Measurements of the initial slope of the Feulgen hydrolysis curve under various conditions of preparation, temperature, and acid concentration demonstrate that this slope has the kinetic properties of the reaction rate of a simple hydrolytic reaction. This result allows a considerable refinement in both the kinetic analysis of chromatin fractions and the cytophotometric measurement of DNA amounts.