摘要:

This paper deals with the problem of finding the ``optimum'' method of detecting a sine wave of known frequency and amplitude in the presence of noise. The type of noise considered is the so‐called Gaussian process, which is obtained when thermal noise is passed through an arbitrary linear passive device.The analysis takes into account the fact that in practice only a finite sample of observed signal is available.The optimum detection method is defined as that which maximizes the probability of recognizing the presence of a sine wave if one has actually appeared; while the probability of falsely announcing the presence of a sine wave, if none has actually appeared, does not exceed some prechosen value.It is shown that when the noise has a flat spectrum, all the relevant information is contained in the amplitude and phase of the Fourier transform of the received sample at the frequency of the sine wave. Almost the same result holds in the case where the noise has an exponentially decaying autocorrelation, except that in this case the values of the observed sample at the end points of the sample also play a role.

ISSN:0021-8979    

DOI:10.1063/1.1721267

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

An exact expression for the temperature difference between the inside and outside of an infinitely long cylinder heated inductively has been derived in terms of Bessel functions. A numerical comparison shows that for small cylinders (radius about 0.3 cm) an assumed parabolic distribution of the magnetic intensity agrees with the exact solution within two percent.

ISSN:0021-8979    

DOI:10.1063/1.1721268

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A method is demonstrated for synthesizing an unbalanced RLC network with lossy coils, i.e., each inductance has an associated series resistance. The network realizes a minimum phase transfer function whose numerator and denominator are of degree not higher than the third and fourth, respectively, and whose poles and zeros may lie anywhere in the left half of the complex frequency plane. It is shown that in many cases higher degree functions may be realized as one network. For a transfer function of arbitrary degree, factoring into component transfer functions is carried out, each component having the above characteristics; the components are then realized separately and isolated from each other by vacuum tubes supplying gain.The method makes use of the following new features:1. A breakdown of a Hurwitz polynomial into two Hurwitz polynomials so that a division by one of them yields a sum of unity plus a positive real RLC function,each of whose partial‐fraction terms(complex poles taken in pairs, or course) is positive real.2. An application of a network theorem which divides the desired network into two networks, thus simplifying the synthesis problem.3. A method of zero shifting to any point in the left half‐plane with at least one pair of complex poles.A further advantage of the procedure is that the network may be designed to possess input and output shunt capacitances so that tube capacitances may be automatically provided for.

ISSN:0021-8979    

DOI:10.1063/1.1721269

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

In the following, the author explains the principle of the double resonant circuit method as used in measuring the electrical characteristics of extremely poor insulating materials such as wood or textile containing much moisture. The characteristics of the measuring circuit and the results obtained thereby are studied.

ISSN:0021-8979    

DOI:10.1063/1.1721270

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Series circuits of ordinary light bulbs and iron‐core transformer coils are found to have properties of the different types of multivibrators and ring circuits. Besides their intrinsic interest value these circuits have application to a diversity of processes, e.g, switching, counting, and time delaying. They can all indicate their action and immediate state by switching on or off large incandescent lamps.

ISSN:0021-8979    

DOI:10.1063/1.1721271

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The amplifying properties of electron streams passing near nonpropagating or lossy walls have been calculated. The method of field analysis is used to obtain values of gain and phase velocity for walls of arbitrary complex admittance. It is shown how one may find easily and quickly these values for actual tube design through use of two contour maps of the complex functions encountered. The gain is found to be zero for open or short circuit, or capacitive wall impedance, low for resistive‐capacitive, higher for resistive and resistive‐inductive, and highest for inductive walls. The behavior of a physically realizable model of the resistive‐capacitive wall is determined. In conclusion, some comment is offered concerning the usefulness of these structures in the realm of microwave tubes.

ISSN:0021-8979    

DOI:10.1063/1.1721272

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The internal friction of quartz was studied by measuring the logarithmic decrement of a bar vibrating in resonance at its fundamental mode at 21 kilocycles per second and at its second harmonic mode at 42 kilo‐cycles per second as a function of temperature from 200°C to 440°C. The logarithmic decrement was found to rise rapidly to a maximum of 16×10−5at about 240°C, then fall slowly to a minimum of about 8×10−5at about 350°C, and then rise rapidly up to and beyond 460°C. The high temperature portion shows a temperature hysteresis in which the cooling curve is lower than the heating curve. Furthermore the magnitude and, to a certain extent, the position of the peak may depend upon previous history but heating in a vacuum can reduce the logarithmic decrement curve to a reproducible one, independent of room temperature handling and thermal gradients (up to 1.5°C/cm) or stress amplitudes (up to 10 g/mm2) applied at higher temperatures.The measured curve can be considered as the sum of two relaxation peaks and an exponential curve. One peak has an activation energy of 27.2×103calories per mole, and the other, 12.6×103calories per mole. The exponential curve appears to be characterized by an activation energy of about 22×103calories per mole but may vary with heat treatment.

ISSN:0021-8979    

DOI:10.1063/1.1721273

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The linear rf mass spectrometer previously described is analyzed for small signal operation. The results are obtained in a closed form for any entrance phase where previously only a graphical solution for an optimized entrance phase was obtained. Expressions for resolving power and current efficiency are derived for both sine wave and square wave operation. It is shown that although high resolving power may be more readily obtained with square wave operation, the product of resolving power and efficiency is approximately the same for sine or square waves. Loss of resolving power caused by the thermal energies of the ions is shown to be less troublesome with square wave operation.

ISSN:0021-8979    

DOI:10.1063/1.1721274

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Young's moduli (E) of the directions ⟨100⟩ and ⟨111⟩ and the shear modulus (G) for ⟨100⟩ were determined in germanium from −195 to 255, 275, and 140°C, respectively. From these moduli, the elastic parameters, the compressibility, and Poissons's ratio were calculated.The thermal expansion was measured from −196 to 275°C.

ISSN:0021-8979    

DOI:10.1063/1.1721275

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The solution is given for the electric field of a small current‐carrying loop which is immersed in a dissipative medium and is energized by a step‐function current. Approximate expressions for the magnetic fields are also derived. The propagation of an electromagnetic pulse in sea water is then discussed.

ISSN:0021-8979    

DOI:10.1063/1.1721276

出版商:AIP    

年代:1953

数据来源: AIP