bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solar Thermoelectric Generators
Authors: Telkes Maria 
Published: April 2005

The physical characteristics, thermoelectric power, resistivity, specific heat conductivity, and the temperature difference between hot and cold junctions determine the efficiency of thermocouple materials. These data have been determined for Chromel P-constantan, bismuth alloys, and the intermetallic compound ZnSb, containing small amounts of added metals.
The optimum characteristics of flat-plate type solar energy collectors have been evaluated in combination with thermocouples, designed for maximum energy conversion. Using flat-plate collectors with 2 glass panes, an efficiency of 0.63 percent was obtained with the ZnSb-type alloys in combination with a negative Bi-alloy. The commercially available ductile alloys Chromel P-constantan, produced ten times lower efficiency. Calculations indicate that the efficiency may be increased to 1.05 percent by using 4 panes of low-reflection characteristics.
With solar energy concentrating means (lenses), the efficiency was increased to 3.35 percent, using the above mentioned best alloy combination.
The maximum allowable cost of thermoelectric generators has been evaluated, by comparison with present methods of electric power generation.
Solar thermoelectric generators may find useful application in the tropics, as they do not contain moving parts and require very little attention. Further development is needed to determine their economical value.
Steady-State Solution of the Two-Dimensional Diffusion Equation for Transistors
Authors: Schaffner J. S. , Suran J. J. 
Published: April 2005

The diffusion equation is solved for transistors for (a) linear flow of minority carriers and (b) non-uniform flow of minority carriers due to a metal contact applied to the base region. The current transport ratio β is calculated for both of these cases as a function of frequency.
Frequency response characteristics of a transistor, as predicted by the one-dimensional diffusion equation, give excellent results for junction transistors having base length-to-base width ratios greater than ten and having negligible surface recombination rates. For transistors where these conditions are not applicable, the two-dimensional diffusion equation must be used in the calculation of β.
On the Nature of Radiation Damage in Metals
Authors: Brinkman John A. 
Published: April 2005

The nature of the permanent damage retained in metals from irradiation has been investigated in somewhat greater detail than has been done in the past. The usual assumption has been that the damage in all metals consists chiefly of interstitial-vacancy pairs. The model presented in this paper reduces to this picture for the light elements but introduces a new concept in the case of damage in the heavy metals, called a displacement spike. Calculations are made from which one can estimate the relationship between the density of interstitial-vacancy pairs and the temperature of the associated thermal spike. An assumption regarding the extent to which interstitial-vacancy pairs persist throughout the duration of the thermal spike has been made, based upon these calculations. The number of interstitial-vacancy pairs predicted in the heavy elements is considerably smaller than that predicted by the former model. A mechanism is proposed by which small dislocation loops can be produced in the heavier metals by irradiation.
This article is based upon studies conducted for the U. S. Atomic Energy Commission under Contract AT-11–1-GEN-8.
Relaxation Time Spectrum of Dough and the Influence of Temperature, Rest, and Water Content
Authors: Cunningham J. R. , Hlynka I. 
Published: April 2005

The effect of temperature, rest period, and water content on stress relaxation in doughs held at constant extension has been studied with a relaxometer previously described. Temperature was varied from 13 to 35°C, rest period from 2 to 120 min, and water content from 74.4 percent to 86.0 percent dry basis. It is found that the shape of the relaxation curves on a log time plot does not change with temperature in the above range but that the curve is shifted laterally along the log time axis. This permits the construction of master curves valid in the temperature range and extends the time scale of observation. The long relaxation time end of the distribution of relaxation times is affected most by rest period, decreasing as rest period is increased, and the short time end increases as water content is decreased. Activation energies from 11 to 24 kcal per mole are calculated for relaxation from the shift of the curve on the log time axis. There is an indication that the activation energy depends on temperature and increases with rest period.
A mathematical framework, based on the general Maxwell model, is discussed and the distribution function on the log time axis is interpreted in terms of viscosity and modulus of the relaxing mechanisms. Special reference is made to the ``box distribution'' and a viscosity is calculated.
Constant Stress Elongation of Soft Polymers: Plasticizer Studies
Authors: Hatfield Marshall R. , Rathmann George B. 
Published: April 2005

Constant stress measurements have been made on lightly cross linked GR-S and polyisobutylene of 7 million molecular weight. The modulus values as a function of temperature, time, and concentration of mineral oil plasticizer have been treated according to the ``reduced variables'' principles.
Since both plasticized and unplasticized samples showed the expected equivalence of temperature and time, the modulus values could be shifted to produce master curves for each composition. In the case of GR-S the concentration of plasticizer could be similarly reduced to yield a single curve for all the data.
The polyisobutylene results, however, showed quite clearly that the plasticizer had a unique effect not paralleled by temperature or time. This effect has been attributed to the pseudoequilibrium modulus which apparently results from chain entanglements. Since the pseudoequilibrium modulus should be proportional to the number of chain entanglements per gram of polymer, it should vary as the square of the volume fraction of polymer. It is shown that a correction of this type improves the shift of the curves for polyisobutylene.
Changes in activation energy with the addition of plasticizer are apparently within experimental error (±2 kcal) in all cases.
The Statistical Properties of the Output of a Frequency Sensitive Device
Authors: Arthur George R. 
Published: April 2005

Frequently it is desirable to know the statistical properties of the output of certain frequency sensitive devices when some type of random signal is impressed. Since most devices of this type are followed by low pass filters, this problem is one of determining the statistics of a filtered signal.
The problem of finding the probability density of the difference of two dependent random variables has not been solved in any general way. Also, the problem of finding the statistical properties of the output of a linear filter upon which a non-Gaussian random signal is impressed has been considered by only a very few writers.
The first sections of this paper gives a solution of the case of a frequency discriminator with no low pass filter, excited by a narrow band spectrum, and is solved by expressing the output of the device as the difference of two independent random quantities, which allows the use of the characteristic function method.
The later sections contain a solution of the problem when a low pass filter is present at the discriminator output. This is done by obtaining the predominant moments of the density from a series expansion which gives a good approximation to the nature of that density Also, in this regard, the approach of the density to a Gaussian one, as the output filter band is made very narrow, is clearly shown.
Amplification Factor and Perveance of an Elliptic Triode
Authors: Deb S. , Sanyal G. S. 
Published: April 2005

An attempt has been made to derive, in terms of valve geometry, theoretical expressions for the constants of an elliptic triode, the shape of the electrodes of which belongs to a family of confocal ellipses. The amplification factor (μ) is derived by following the method of conformal transformation. Result shows that in general it varies with the parametric angle θ of the ellipse—decreasing from the direction of minor to that of the major axis. The average value of μ increases with increasing value of the eccentricity of the grid and with decreasing value of the eccentricity of the anode. Curves for ready evaluation of μ for any value of θ are given. The problem of design of an elliptic triode having a constant μ for all values of θ is also considered and its method of solution indicated. An expression for the perveance (P) has also been obtained by adopting the procedure followed by O'Neill for determining the perveance of a plane diode having filamentary cathode. The expression shows that the value of perveance is determined mainly by the eccentricity of the grid and the focal distance.
To illustrate the practical applications of the various deductions made, a numerical example, involving the design of a 6C5-GT/G type triode, is given.
Spectroscopic Studies of Highly Ionized Argon Produced by Shock Waves
Authors: Petschek H. E. , Rose Peter H. , Glick Herbert S. , Kane Anne , Kantrowitz Arthur 
Published: April 2005

For the study of high-temperature gas dynamics, shock-tube techniques have been developed earlier to produce shock waves strong enough to heat gases to high and accurately known enthalpy (for argon up to 18 000°K or 40 percent ionization at equilibrium). This paper reports a study of the visible radiation from the highly luminous argon following strong shock waves.
Preliminary spectrograms showed a strong continuum and that the prominent argon lines were broadened and shifted to the red. Correlation of the frequency shifts with theoretical treatments permitted an evaluation of the ion density in the gas. Development of a drum camera spectrograph (film speed 700 ft/sec) in which time effects could be resolved to about 1 μsec indicated that equilibrium ion density was reached rapidly, and provided a rough measurement of the rate of decline of ion density due to cooling.
Absolute photoelectric spectrophotometric measurements of the continuum radiation were made and correlated with theoretical expectations. Confirmation of the expected variation of continuum intensity with wavelength and temperature was obtained and an undetermined factor on the theoretical intensity was evaluated. Determinations of the cooling rate of the high-temperature argon from time variation of the continuum intensity, the line shift, and the electrical conductivity (by others) are in agreement and show that continuum radiation was the dominant heat loss.
Outgassing of Glass
Authors: Todd B. Johnson 
Published: April 2005

The gas evolved from glass at temperatures below the softening point, which is of interest in bake-out problems, is primarily water. The water evolved from unit surface at constant temperature above 300°C is linear with respect to the square root of the time of bake-out. The intercept of the linear plot, which can be altered by different surface treatments, is a measure of the easily removed water residing at the surface. The slope is a measure of the rate of evolution of water that has diffused to the surface from the interior.
Values of the diffusion constant for water and concentration gradients after bake-out have been calculated for a soda-lime glass. The diffusion constant is an exponential function of the reciprocal of the absolute bake-out temperature. Values of the activation energy for the diffusion process are given for eight glasses.
A method of calculating the amount of water that will diffuse from glass for any time-temperature conditions following any bake-out is presented.
Conduction and Breakdown in Hexane
Authors: Green W. B. 
Published: April 2005

Conduction currents in hexane, studied as a function of spacing, metal, and heat treatment of the electrodes over the field-strength range from 0 to 250 kv/cm, obey neither a field-enhanced thermionic emission nor the customary field emission relation. The most important factor determining the currents appears to be a surface layer on the cathode. Exposing the liquid to gamma rays increases the current in a fashion that indicates a decrease of the effective work function rather than merely a collection of ionization products. Heat treatment of the cathode, by changing the nature of the surface layer, changes the emission. It appears that positive ions collect on the more or less insulating surface layer and build up intense local fields that cause electron emission. The size of the local field depends on the number of the ions arriving per second and on the thickness, homogeneity, and conductivity of the surface layer.
For some electrodes the current increases with gap width for constant field; previous investigators have interpreted this fact as evidence of impact ionization in the liquid. However, change of current with gap width proves to be an electrode property; some electrodes do not show it.
In one case the current was measured up to breakdown (1060 kv/cm). There is an indication that impact ionization may exist above 800 kv/cm; if so, the ionization factor is very small.
A variety of purification systems was tried but no influence of the purification treatment on the conduction currents was found.
Calculation of the Complex Modulus of Linear Viscoelastic Materials from Vibrating Reed Measurements
Authors: Bland D. R. , Lee E. H. 
Published: April 2005

Two methods of determining the variation of real and complex modulus with frequency from vibrating reed test results are detailed. One is based on measurements of the relative amplitude and phase lag of the motion of the free and driven ends of the reed, the other on amplitude resonance measurements only. The analysis is based on a general linear viscoelastic law, and takes into account the influence of the frequency dependent moduli of the material on the frequency and amplitude of the resonance peaks. This influence has not been correctly accounted for in previous analyses which have included the assumption that the material behaves according to a particular, simple viscoelastic law, which will in general not be borne out by the final results.
The method is applied to a series of tests. For the material and frequency range used the imaginary part of the complex modulus was small compared with the real part, and the influence mentioned in the foregoing was small. A simpler method of analysis might thus be justified, but in other cases it will be necessary to carry out the complete analysis in order to obtain a satisfactory interpretation of test results.
Information Theory Aspects of Propagation through Time-Varying Media
Authors: Feinstein Joseph 
Published: April 2005

The channel capacity of a communications system which utilizes wave propagation through a time-varying medium such as the ionosphere or troposphere is evaluated in terms of the statistical properties of the medium and of the noise. The signal fading in such a system reduces the capacity. Rayleigh fading is found to give rise to an equivalent signal to noise ratio of 1.72, while shallow fading of the Gaussian type augments the noise in the channel by a fraction of the signal power proportional to the fading depth. An optimum manner of band width subdivision is shown to exist when selective fading is present.
Information theory concepts are broadened to include the possibility of multiple reception at spaced receiving sites, and the consequent increase in theoretical channel capacity is computed as a function of the number of such sites and the signal statistics. The method of maximum liklihood is utilized to obtain optimum combinatorial laws for the multiple signals. The commonly employed maximum signal selection diversity system is shown to perform as well as the optimum system in the presence of Rayleigh fading, for a small number of receiving sites.
Radiation Characteristics of a Conical Helix of Low Pitch Angle
Authors: Chatterjee J. S. 
Published: April 2005

The present work is an extension of the author's prior work on the radiation characteristics of and current distribution in a conical helix, the helix used in the present case having a pitch angle much lower than of that studied previously. In this case the condition of the phase velocity adjusting itself automatically to maintain maximum directivity condition (which enables the radiation to be confined in the axial mode over a large band of frequencies) does not hold. Nevertheless the major fraction of energy could be radiated in the axial direction when the geometry of the helix and the distance of the apex from the ground were properly chosen, the conical helix together with the ground being regarded as tapered transmission lines (with the ground as one and the helix wire—with the distance of its elements from the ground line increasing continually,—as the other line).
Measurements of the field intensity and the current distribution were made in the frequency range of 100 Mc/sec to 500 Mc/sec with a conical helix antenna arrangement as follows. The helix was of six turns, the radius increasing uniformly from 5 cm at the apex to 65 cm at the base within an axial distance of 60 cm. The apex of the helix was placed at a distance of 17.5 cm from the ``ground'' provided by a 6-ft square copper netting of close mesh. It was found that within the range of frequency measured the major fraction of the energy was radiated in the axial direction. Theoretical expressions for Eφ and Eθ were derived by assuming a linear current distribution, and the calculated radiation patterns were found to agree with the experimentally determined ones.
Nucleation of Ammonium Iodide Crystals from Aqueous Solutions
Authors: Newkirk J. B. , Turnbull D. 
Published: April 2005

Ammonium iodide crystals nucleate at a sensible rate in small drops (10–50 micron diameter) of solution only if the supersaturation ratio S equals or exceeds a value of 1.21. This critical supersaturation ratio corresponds to an interfacial energy σ between ammonium iodide crystals and solution equal to or greater than 15.4 ergs/cm2. However, for sensible nucleation of NH4I on a freshly cleaved surface of one of the mica minerals, S is related to the disregistry δ between atom sites on the mica surface and the atom sites on a {111} plane of NH4I. This dependence can be described by the equation lnS=3.8δ2+0.0059. This equation is in agreement with the theory of Turnbull and Vonnegut relating disregistry to the potency of nucleation catalysts. However, the coefficient of δ2 is about 1 to 2 orders of magnitude smaller than the theoretical expectation.
Our results are consistent with Bradley's hypothesis that S, for sensible 2-dimensional nucleation of NH4I on its own perfect {111} planes, is remarkably small, viz. S≃1.01.
Equivalent-Radius Method for Determination of Non-Newtonian Flow Curves from Viscometric Data
Authors: Cram K. H. , Whitwell J. C. 
Published: April 2005

A rapid and precise method is presented for approximating absolute flow curves (shear rate vs shear stress) of non-Newtonian liquids from data obtained with rotational or capillary viscometers. It is shown that the apparent Newtonian flow curve computed from a single measurement (i.e., a single flow rate) in either type of viscometer crosses the true flow curve at a shear stress corresponding to some intermediate radius between the bob and cup radii or less than the capillary radius. If shear rate and stress are computed at the common point using the ordinary Newtonian relations for shear stress and shear rate, the point so calculated will lie on the absolute flow curve. An ``equivalent radius'' rather than a wall radius is used in the conventional Newtonian equations.
The position of the equivalent radius is fairly insensitive to changes in the form of the flow curve, particularly in the case of the rotational viscometer. A method for determining the proper intermediate radius is developed and graphs are presented to facilitate this determination and permit estimation of the accuracy of the method. An example is given using data from the literature [I. M. Krieger and S. H. Maron, J. Appl. Phys. 25, 72 (1954)] for a 62.2 percent GR-S Latex slurry. Within the range of the data (slope of the log-log flow curve varying from 1.5 to 3.0), the maximum error incurred by use of a single equivalent radius for each of two rotational viscometers was 0.1 percent for the instrument with a cup/bob radius ratio of 1.064, and 0.4 percent for the instrument with a ratio of 1.113. Accuracy can be increased by use of an iterative procedure.
The method has been developed in detail only for the case of pseudo-plastic flow, but the principle can be applied to other types of flow.
Theoretical and Experimental Study of Electromagnetic Scattering by Two Identical Conducting Cylinders
Authors: Row R. V. 
Published: April 2005

The scattering of a cylindrical TEM wave by two parallel, identical conducting circular cylinders is developed as a special case of a theoretical analysis which treats the scattering by an arbitrary array of cylinders. Only the case with the incident E-vector parallel to the axes of the cylinders is considered, and attention is focused on the mutual effects present when the cylinder diameter and spacing are comparable to a wavelength.
The approximations made in the theory are tested experimentally using 3 cm microwaves in a parallel plate region. Significant departures from the results of the independent scattering hypothesis as predicted by the theory have been confirmed experimentally.
Performance of the Nonmagnetic Radio-Frequency Mass Spectrometer Tube
Authors: Wherry T. C. , Karasek F. W. 
Published: April 2005

The nonmagnetic radio-frequency principle of mass selection appears attractive because it promises to result in a mass spectrometer of simple construction and rugged nature. Accurate evaluation of the use of this principle is difficult because of the lack of published performance data. In an effort to obtain performance data a 5-stage Bennett-type tube with stage separation of 5–9-4–7 cycles has been constructed and operational variables studied theoretically and experimentally.
The experimental results are encouraging. They indicate the tube is capable of sufficient stability, resolving power, and sensitivity to be used for many analytical and research problems. Electronic circuits required to achieve a reasonable stability are relatively simple.
Silicon n-p-n Grown Junction Transistors
Authors: Tanenbaum M. , Valdes L. B. , Buehler E. , Hannay N. B. 
Published: April 2005

Silicon n-p-n junction transistors have been made from rate-grown single crystals. Using gallium and antimony as doping agents, single crystals of n-type silicon have been grown containing up to five p-regions from 0.0005 to 0.002 inches wide which are suitable for the production of transistors. The ohmic contact to the p-type base region was made by alloying an aluminum wire using techniques similar to those employed in the fabrication of aluminum-silicon diodes.
The electrical evaluation of n-p-n transistors produced from these single crystals is described. Alphas in excess of 0.9 at −1 ma emitter current have been obtained, and collector saturation currents of 10−6ampere/cm2 are common. With base-layer widths of about 0.0005 inch, the alpha cutoff occurs at approximately 5 megacycles. The units (approximately 0.04×0.04×0.5 inches in size) have been operated at power levels in excess of 1.5 watts in air with no special provision for heat dissipation.