摘要:

Theoretical expressions are found for the displacement of points on an ideal clamped‐end string relative to the end points when the supports are given an acceleration normal to the string length att=0. The accelerations considered have the form of (1) the Heaviside unit function, (2) the Dirac &dgr; function, and (3) the doublet impulse function. Approximate formulas for the maximum displacement of the string are derived for each of the three cases. Possible applications of the results to the problem of filament‐grid shorts in certain vacuum tubes are briefly discussed.

ISSN:0021-8979    

DOI:10.1063/1.1721175

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

In the development of high‐speed aircraft, rockets, missles, etc., wind‐tunnel pressure measurements at supersonic velocities are necessary to determine certain aerodynamic characteristics. Because of the lack of knowledge concerning the proper choice of parameters in the design of pressure instrumentation, the response time has been known to exceed the running time in the case of the intermittent tunnel. Pressure systems consisting of an orifice, a capillary tube, a length of connecting tubing, and a pressure‐sensitive element connected in series are analyzed. The time required for the pressure in the pressure‐sensitive element to reach within 1 percent of the equilibrium pressure is defined as the response time of the system. Experiments are conducted to determine the effect of the various geometric and dynamic parameters on the response time. Analytical solutions of the flow equations by numerical integration are carried out for the special case of a length of capillary tubing connected to the pressure‐sensitive element for three different inside diameters.The data indicate that the response time can be maintained within acceptable limits for present‐day supersonic wind‐tunnel installations by proper choice of the geometric and dynamic parameters. The agreement between theory and experiment, being quite satisfactory for the special case solved analytically, indicated that the approximations in the derived flow equations are justified.

ISSN:0021-8979    

DOI:10.1063/1.1721176

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

An analysis of the transient response of transistor amplifiers necessitates the consideration of transit time effects. Transit time behavior of minority carriers is described by the diffusion equation. Since the diffusion equation applies to minority carriers in the base region of a transistor, a current transfer function may be derived from the diffusion equation relating the collector current to the emitter current. This transfer function is valid only when the transistor is operated as a linear amplifier with small load impedance. For these conditions, the transfer function is solved for the collector current response to a step in emitter current by use of Laplace transform techniques. The collector current rise time, as a function of the &agr; cut‐off frequency, is derived from the theoretical equations and compared to measured values.

ISSN:0021-8979    

DOI:10.1063/1.1721177

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Approximate formulas for the complex propagation constant and characteristic field configuration for dielectric‐filled traveling wave slot antennas are obtained by a variational procedure. To set up the variational method, the generalized reciprocity theorem for traveling wave line sources is deduced; it differs considerably from the reciprocity theorem for point sources. A perturbation technique for solving the variational equations is given. Formulas are worked out for rectangular wave guides and good agreement with available measurements is obtained.

ISSN:0021-8979    

DOI:10.1063/1.1721178

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A variational method of determining the attenuation and phase constants for the fields along a slotted wave guide is presented. Calculated and experimental values for a slotted circular wave guide excited in theTE11andTM01modes are included.

ISSN:0021-8979    

DOI:10.1063/1.1721179

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Experiments are described which measure the threshold acoustic pressures necessary for cavitation which can destroy certain biological cells. These thresholds are in the neighborhood of 0.3 atmospheres in the frequency range from 0.4 to 500 kc. At lower frequencies much greater pressures appear necessary and the type of biological damage is different. An interpretation of these results is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1721180

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Computations have been made of the total beta activity of the fission products arising from the slow neutron fission of U235. A curve is given exhibiting the activity per unit fission, for time intervals after fission ranging from 0.01 second to 10 years. This influence function is compared with some published experimental data and with the statistical curve of Way and Wigner. A curve of its integral as a function of the upper limit is also given. This latter curve facilitates estimation of the activity in the particular case where the fission rate has been constant throughout a known time interval. Finally, an influence function for the particular group of fission products consisting of complete and partial chains having volatile first members is given.

ISSN:0021-8979    

DOI:10.1063/1.1721181

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Equivalent reactances of inductors and capacitors with moderate nonlinearity may be approximated by the usual linear expressions plus terms which depend on the square of the current. With the help of this approximation, the total impedance of anLRCcircuit is obtained and plotted in theI‐Zplane with frequency as a parameter. The current for any given frequency and voltage may be easily obtained from this plot by graphical means. This method gives an interpretation of the triple‐valued frequency response curve in terms of circuit concepts.

ISSN:0021-8979    

DOI:10.1063/1.1721182

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Transient one‐dimensional flows have been produced by accelerating a piston in a gas‐filled tube. Accelerations of the order of 2.5×104m/sec2produced shocks within 5 m of the initial piston position. The piston was propelled pneumatically. Shocks formed at the head and in the interior of the compression waves. By optically detecting the piston and shock positions and recording the corresponding times on a rotating drum chronograph with microsecond accuracy, the properties of the compression wave and resulting shock were determined. The formation and growth of shocks were calculated from the compression wave measurements using the method of characteristics and the assumptions employed by Chandrasekhar and Friedrichs. The observed and calculated shock properties were in reasonably good numerical agreement. Consistent lagging of the observed behind the calculated shock positions (order of 0.05 m at 5 m from initial piston position) is attributed to the interaction of the flow with the tube walls.

ISSN:0021-8979    

DOI:10.1063/1.1721183

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Fringe shifts on interferograms of flows atM= 2.45 about variously truncated 15° (half‐angle) cone cylinders in free flight in a pressurized range have been examined for similarity of the flow fields, occurrence of scale effects, and convergence to conical flow. It was found that flows over similar objects with equal tip Reynolds numbers were similar and that convergence to conical flow occurred before the disturbance at the tip had been reflected the second time along characteristics to the body. Density distributions have been determined, and a number of comparisons have been made with theoretical predictions.

ISSN:0021-8979    

DOI:10.1063/1.1721184

出版商:AIP    

年代:1953

数据来源: AIP