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A stochastic mathematical model is developed to describe the probability distribution of dissolved oxygen in streams which have received an input of both thermal and organic pollution. The stochastic model is simulated under conditions of constant and variable temperature, and the results of the simulation are compared with the mean values predicted by recent deterministic models. The simulation provides an estimate of the variability of the DO level to be expected at different points as well as a means of generating typical oxygen sag curves for a stream.

Three electrical effects in an approximately stoichiometric propane-oxygen flame seeded with aluminum powder were studied: a) increase in flame current caused by the addition of aluminum, b) effect of transverse electrical field on the rate of aluminum oxide deposition onto a solid surface, c) effect of the field on the rate of heat transfer to a flat plate immersed in the flame. The maximum field was limited by breakdown to about 450 v/cm. It appears that the oxide deposition rate and the heat transfer rate can be influenced by relatively small electric fields. On a etudie trois effets electriques dans une flamme de propane et d'oxygene (en quantites approximativement stoichiometriques), ou l'on avait jete de la poudre d'aluminium; ces effets sont les suivants: a Augmentation du courant de la flamme par l'addition d'aluminium. b Influence du champ electrique transversal sur la vitesse a laquelle l'oxyde d'aluminium se depose sur une surface solide. c Effet du champ sur la vitesse du transfert de la chaleur a une plaque unie qu'on introduit dans la flamme. On a limite, par rupture, le champ maximum a environ 450 volts par centimetre. La vitesse a laquelle l'oxyde se depose et celle du transfert de la chaleur ont paru eCtre influencees par des champs eAlectriques relativement faibles.

An equation was obtained that would establish the growth kinetics under batch conditions in an aerobic system of organic wastes. The growth kinetics equation was then combined with a linear relationship between sludge growth and BOD removal in order to develop a second equation that expressed the BOD removal under batch conditions. The two equations were combined with a mass balance to determine the treatment efficiency in a completely mixed-continuous flow system. The equations thus developed for these two systems (batch and completely mixed-continuous flow) were checked against experimental results obtained with a synthetic activated sludge at 25○C.

Synopsis In this note an approximate but very convenient method for analysing the stability of soil adjacent to a sheet piling against seepage forces is presented. The errors introduced by the approximation are discussed. Graphs facilitating the computation and estimation of errors are presented. A solvedexample is presented to illustrate the method. The method is based upon a principle analogous to that of St Venant in elasticity coupled with simple analytic solutions of the Laplace equation. Cette note présente une méthode approximative mais très pratique d'analyse de la stabilitié du sol adjacent à des palplanches centre les forces de filtration. On discute des erreurs causées par l'approximation. Des graphiques facilitent les calculs et les évaluations d'erreurs. Un exemple résolu illustre la méthode. La méthode est basée sur un principe analogue à celui de St Venant en élasticité associé à des solutions analytiques simples de l'equation de Laplace.

SURFACE WAVE MEASUREMENTS ARE USED IN EVALUATING A PAVEMENT SYSTEM FOT STUDYING PERFORMANCE, MAINTENANCE, AND ESTABLISHING CONSTRUCTION CONTROL. THE EXPERIMENTAL PROCEDURE IS DESCRIBED, AND THE THEORETICAL BASIS FOR INTERPRETING THE EXPERIMENTAL DATA IS REVIEWED. AVAILABLE INFORMATION SHOWS THE USE OF THE WAVE PROPAGATION METHOD IN THE PRACTICE OF PAVEMENT ENGINEERING. THE ADVANTAGES AND LIMITATIONS OF THE METHOD ARE ANALYZED. /AUTHOR/

A deterministic model is developed for the oxygen sag curve for a variable temperature condition under thermal overload. With the help of this model, optimal locations of thermal and organic outlets with respect to each other can be determined for a predetermined minimum dissolved oxygen concentration in the river. In the presence of the thermal overload, the critical oxygen concentration (lowest) is much lower than that under constant temperature conditions of the stream, and it occurs earlier, the recovery of DO could be faster, and indeed the DO level downstream may be higher than under the constant temperature condition. The critical DO concentration and the critical oxygen deficit do not necessarily occur at the same point in the presence of the thermal overload. The mathematical models presented herein could be used in place of the constant temperature models.

The differential equation of beams of finite length, resting on a Winkler foundation is solved in terms of the initial conditions, i.e., the conditions at one of the ends of the beam. With the solution in this form, which contains the initial conditions as the constants of integration, it is then possible to write merely by inspection the equation of the elastic line. The solution of the resulting boundary value problem is simplified through the use of special functions, which possess interesting properties, and a table of values of these special functions.

The ignition of aluminum particle streams was studied in a steady-flow experiment in which aluminum powder carried in oxygen was ignited by a propane-oxygen pilot flame. Two measured particle size distributions were used, with average diameters of 25 μ and 120μ. Particle-to-gas weight fractions were in the range from 0.1 to 0.5. Ignition times were deduced from flame photographs and high-speed motion pictures were used to follow the ignition event. A simple thermal ignition model was used to predict particle ignition times. The model takes into account the radiation from the burning stream of particles to the unignited particle, as well as to the heating of this particle by a finite volume of hot gas. The measured ignition times were independent of metal concentration. The stream with 35 μ mean size ignited at 0.5 ms and the stream with 120μ mean size at 1.1 ms after injection into the flame, both independent of the metal flow rate. Comparison with the predicted ignition times for the two particl...

An experimental and theoretical study of the axisymmetric turbulent boundary layer on circular cylinders over a range of radius Reynolds numbers Ra from 425 to 2 × 105, suggests the existence of a law of the wall in the form u* = A log Y* + B, where Y* = (uτa/ν) log (r/a). The constant A depends only on Ra while B has been found to depend on Ra as well as auτ/ν. It was observed that from the beginning of transition to turbulent flow in the boundary layer, there was a “negative wake” region in the outer part of the boundary layer which progressively disappeared as the flow was swept downstream, giving, at some station, a velocity profile (called here the “marginal profile”), which had no wake component. Further downstream, there was progressively increasing positive wake component. In these regions, it is surmized that the penetration of the viscous effect from the wall to larger distances across the boundary layer (as indicated by the absence of a constant stress layer), as well as the probable effect of viscosity in the wake portion (as in a purely axisymmetric wake), yielded similarlity of the defect (U − u)/uτ, only in terms of the quantity (ruτ/ν) for a given Ra. From a study of the rate of decrease of Cf with Rx in laminar and turbulent flows, there is reason to believe that an initially turbulent boundary layer will undergo relaminarization if Ra is less than about 15,000 which may be compared with the stability limit of 11,000 found by Rao [6].

Incoherent radiation is usually observed emanating from the p or n region of a wafer containing a p-n junction. In the region in which the radiative recombination occurs, the P/I ratio is 1.5 watts per ampere at 77° K for unity quantum efficiency. The ratio of the maximum power which may exit either the p or n surface to that generated within the crystal is approximately 1 : 57. This relationship results in an upper limit of 26.3 milliwatts per ampere. The small ratio is a consequence of the small critical angle in gallium arsenide. When the p-surface is employed as the exit surface, for junction areas approaching 1 cm2, the highest value obtained at 77°K is 14 milliwatts per ampere. For junction areas of 10-2cm2, values of 20 milliwatts per ampere have been observed. The maximum average current which may be passed by such a junction and still maintain a positive slope for dP/dI is 10 to 20 amperes. Thus, the total power obtainable from 1 cm2is less than 0.280 watt. This limitation arises primarily because of the excessive joule dissipation present in such large area junctions. This investigation has resulted in geometrical configurations suitable for average power output in excess of 10 watts and configurations for pulse power output in excess of 1 kilowatt. The total semiconductor area for each of the above systems is less than 20 cm2. The measurement technique and method of calibration is briefly discussed. The data obtained from these structures shows that P/I values as high as 170 milliwatts per ampere have been obtained. It is shown that one of the structures regularly achieves 40 to 60 milliwatts per ampere. Moreover the structures exhibit much less power dissipation which permits a higher power output than present junction structures. The radiation characteristics of the present junction structure are compared to the new structures for dc, average and peak power. For pulsed operation, the average and peak power are given as a function of the period. The maximum peak power is at least 100 times greater than the average power at low duty cycle operation. Under this condition the quantum efficiency is several times greater than the dc value. This is also true for duty cycles of 1 to 10 percent for which the junction heating effect is appreciable. Junction heating becomes appreciable at a duty cycle of 10 percent for junctions exhibiting a resistance value of 0.04 ohms and a current value of 2 amperes. Absorption of the radiation at the contacts also contributes to junction heating, however, to a lesser degree.

The use of metal-nitride-oxide-semiconductor structure as a storage element was reported by Szedon at the 1967 Device Research Conference. When such a structure is used as p-channel enhancement mode device, a positive gate voltage exceeding a certain critical value changes the device into depletion mode. Later when a negative gate voltage of the order of this critical voltage is applied, the device changes back to enhancement mode. This phenomenon has been explained as electron tunneling from the semiconductor through the oxide into the traps in the nitride with a positive gate bias, and from traps into the semiconductor with negative gate bias. This can be used as a nonvolatile memory element.