scholarly journals The high-frequency resistance of multiply-stranded insulated wire

1917 ◽  
Vol 93 (654) ◽  
pp. 468-492 ◽  
Keyword(s):  
Magnetic Flux ◽  
High Frequency ◽  
Usual Method ◽  
Rate Of Change ◽  
Projected Area ◽  
Current Frequency ◽  
High Frequencies ◽  
Average Value ◽  
The Individual ◽  
Very High

Conductors which have to carry high-frequency currents are often made up of a large number of separately insulated fine wires stranded together, with the object of compelling the current to distribute itself over the whole cross-section of the conductor. This may be done for two different reasons: firstly, to decrease the variation of inductance and resistance with change of frequency; and, secondly, to decrease the effective resistance of the conductor at high frequencies. To be effective, it is necessary that every wire should occupy in turn the same relative position in the conductor, so that the electromotive force induced in each wire by the magnetic flux should have the same average value over the whole length of the wire. If every separate wire has the same resistance, the same applied P. D. and the same induced E. M. F., both in amplitude and phase, they will all necessarily carry the same current, and the total current will therefore be uniformly distributed between all the wires. The usual method of obtaining this similarity in the path of every strand is to make a conductor of three, four, or five wires twisted together, and then to twist three such conductors together, and so on until the resulting conductor contains the required number of wires. A large number of such multiple conductors are sometimes plaited or braided into a tubular con­ductor. Two of the individual wires of such a conductor may be in contact, except for the insulation, at a certain point, and then again further on at another point, one wire having followed an internal and the other an external path between the two points. From a knowledge of the current, frequency, and projected area of the loop formed by the two wires, measured normal to the magnetic flux, the E. M. F. induced in the loop can be calcu­lated; thus, if the multiple conductor has a diameter of 1 cm. and is wound into a coil with one turn per centimetre, and if the current is 100 amperes at a frequency of 10 6 , the E. M. F. induced in a loop of 5 sq. cm. is about 20 volts, giving 10 volts between the wires at each point of contact. In circuits containing spark-gaps the rate of change of the current may reach very high values and thus cause much greater potential differences between the separate strands, which must therefore be efficiently insulated to prevent sparking between them.

187. The effect of subclinical mastitis on the solids-not-fat content of milk

1938 ◽  
Vol 9 (2) ◽  
pp. 182-184 ◽  
Author(s):  
S. J. Rowland ◽  
M. Zein-El-Dine
Keyword(s):  
Subclinical Mastitis ◽  
Fat Content ◽  
Average Value ◽  
The Individual ◽  
Very High

The solids-not-fat content (expressed as a percentage of fat-free milk) has been determined for 247 samples of milk from the individual quarters of sixty-two cows. The samples were also examined bacteriologically for the presence of mastitis streptococci and 121 were found to be infected, 114 uninfected, and twelve “doubtful”.The solids-not-fat content of the uninfected samples varied from 8·24 to 10·28 and of the infected samples from 4·26 to 9·92. For the uninfected samples of the Shorthorn, Friesian, Ayrshire and Guernsey breeds it averaged 9·36, 9·11, 9·82 and 9·83 respectively, but in the infected samples only 8·44, 8·38, 8·28 and 9·49%.Of the 247 samples, 36 % were below 8·80 in solids-not-fat content. Of 121 infected samples, 63% were below while of the 114 uninfected samples only 9% were below this standard. Hence 88% of the samples below 8·80 were infected samples, thus showing that subclinical mastitis accounts for a very high percentage of samples low in solids-not-fat content. In these samples the average value for solids-not-fat was 7·93%. The few uninfected samples that were low in solids-not-fat averaged 8·56%.

scholarly journals Safety of Construction Components in a Very High Number of Load Cycles

2020 ◽  
Vol 2 (1) ◽  
pp. 199-206
Author(s):  
František Nový ◽  
Juraj Belan ◽  
Otakar Bokůvka
Keyword(s):  
Fatigue Resistance ◽  
High Frequency ◽  
Asymmetry Parameter ◽  
High Strength ◽  
Cyclic Stress ◽  
Average Value ◽  
Safety And Reliability ◽  
Important Position ◽  
Very High

AbstractProgressive, high-strength materials have an important position in the transport industry. In this industry, components are subject to high safety and reliability requirements because they often operate under long-term cyclic stress regimes. The paper presents results of fatigue resistance of high-strength materials such DOMEX 700MC, HARDOX 400, HARDOX 450, and INCONEL 718 (UTS from 850 to 1560 MPa) measured at high-frequency cyclic loading (f = 20 kHz, T = 20 ± 5 ° C, push-pull loading, cycle asymmetry parameter of R = -1) in the area from N = 2x106 to N = 2x108 cycles. Fatigue resistance showed a continuous decrease about average value Sa 2x108/Sa 2x106 = 19.1%.

scholarly journals AGENTS THAT CAUSE A HIGH FREQUENCY OF GENETIC CHANGE FROM [psi  +] TO [psi  -] IN SACCHAROMYCES CEREVISIAE

Genetics ◽  
1981 ◽  
Vol 98 (4) ◽  
pp. 691-711
Author(s):  
M F Tuite ◽  
C R Mundy ◽  
B S Cox
Keyword(s):  
Saccharomyces Cerevisiae ◽  
High Frequency ◽  
Guanidine Hydrochloride ◽  
Genetic Change ◽  
Phenotypic Change ◽  
Chromosomal Gene ◽  
High Frequencies ◽  
High Concentrations ◽  
Very High Frequencies ◽  
Very High

ABSTRACT The [psi] factor of yeast is cytoplasmically inherited. Singh, Helms and Sherman (1979) reported that high concentrations of KCl and of ethylene glycol induce the genetic change from [psi  +] to [psi  -]. In this study, the following agents have been shown to induce the same genetic change: guanidine hydrochloride at 1 mm, dimethyl sulfoxide at 2.5% v/v and ethanol or methanol at 10% v/v. It is likely that a number of other agents also cause the change, namely 2 m glycerol, m succinate, m glutamate and m MgCl2. Most of these agents induce the change at very high frequencies; with some, the frequency is 100%. Although the observed phenotypic change can also occur as a result of chromosomal gene mutation, no changes of this type were identified. Some of the agents also cause mutation from [rho  +] to [rho  -] and from killer to sensitive.

scholarly journals Evaluation of Meshed Reference Planes for High Performance Applications

2000 ◽  
Vol 22 (3) ◽  
pp. 175-187 ◽  
Author(s):  
N. D. Codreanu ◽  
P. Svasta ◽  
V. Golumbeanu ◽  
L. Gál
Keyword(s):  
Integrated Circuits ◽  
High Frequency ◽  
High Speed ◽  
High Performance ◽  
Network Analyzer ◽  
High Frequencies ◽  
High Speeds ◽  
University Of Budapest ◽  
Very High Frequencies ◽  
Very High

The actual generations of integrated circuits are characterized, inter alia, by very high frequencies or very high speeds. The dramatic evolution ofthe semiconductor's technology establishes a greater “pressure” to the design and the manufacturing of the passive interconnection structure from PCB/MCM electronic modules. In these conditions the reference planes (power and ground planes) have a more and more important contribution. The paper intents to present the effect of different configuration reference planes on the characteristics of the high speed/high frequency interconnection lines. The first part deals with modeling and simulation of usual practical interconnection geometries. A computer modeling of meshed structures was realized and Spice models for a good compatibility with circuit simulators were obtained.S-,Y-,Z- parameters and radiation patterns were calculated, too. The second part contains measurements made by a vector network analyzer as regards to different practical configurations manufactured at Technical University of Budapest.

Structural, Optical and Electrical Properties of μc-SiC:H Thin Films Deposited by the VHF-GD

1994 ◽  
Vol 358 ◽  
Author(s):  
Roger Fluckiger ◽  
J. Meier ◽  
A. Shah ◽  
J. Pohl ◽  
M. Tzolov ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Gas Phase ◽  
High Frequency ◽  
Input Power ◽  
Optical And Electrical Properties ◽  
Very High Frequency ◽  
Deposition Parameters ◽  
Temperature And Pressure ◽  
The Individual ◽  
Very High

ABSTRACTIn the present paper the authors present new results on thin (μc-SiC:H films deposited at low temperatures by the Very High Frequency - Glow Discharge technique (VHF-GD) at 70 MHz. The individual effects of each of the deposition parameters (methane and diborane gas phase ratios, input power, deposition temperature and pressure) are investigated with respect to the structural, optical and electrical properties of the films; the goal being the growth of optimised, thin μc-SiC:H layers for use as highly conductive and high gap window layers in solar cells.

Control Architecture for 30MHz Linear Imaging Array

2003 ◽  
Author(s):  
R. L. Tutwiler ◽  
J. P. Stitt ◽  
K. K. Shung ◽  
Q. Wu ◽  
T. A. Ritter ◽  
...  
Keyword(s):  
High Frequency ◽  
High Speed ◽  
Very High Frequency ◽  
Front End ◽  
High Speed Data Acquisition ◽  
Under Construction ◽  
The Individual ◽  
Test Phantom ◽  
Signal Interface ◽  
Very High

The purpose of this system is to have the capability to characterize the performance of very high frequency transducers and arrays. The analog front end is computer controlled by a set of de-multiplexers and multiplexers. The output of the multiplexer network is connected to a TGC array, which is interfaced to a high-speed data acquisition system. A software GUI (Graphical User Interface) has been designed to accomplish this task [1]. A programmable digital I/O interface allows collection of RF channel data and has the capability to be interfaced to a very high frequency analog beam-former under construction. The system front-end electronics (pulsers, receivers, T/R switches, multiplexers, and demultiplexers) have been characterized [2, 3]. The digital I/O signal interface has been integrated and tested. The hardware front end has been integrated to the array interface distribution panel. The individual transducer elements impulse responses have been evaluated and the performance of the array has been tested with a wire test phantom to characterize lateral and axial resolution.

scholarly journals Design and simulation of high frequency colpitts oscillator based on BJT amplifier

2020 ◽  
Vol 10 (1) ◽  
pp. 160
Author(s):  
Khalid A. Humood ◽  
Omar A. Imran ◽  
Adnan M. Taha
Keyword(s):  
High Frequency ◽  
Rapid Development ◽  
Advanced Technology ◽  
Colpitts Oscillator ◽  
High Frequencies ◽  
Bipolar Junction Transistor ◽  
Barkhausen Criterion ◽  
Junction Transistor ◽  
Very High Frequencies ◽  
Very High

Frequency oscillator is one of the basic devices that can be used in most electrical, electronics and communications circuits and systems. There are many types of oscillators depending on frequency range used in an application such as audio, radio and microwave. The needed was appeared to use high and very high frequencies to make the rapid development of advanced technology Colpitts oscillator is one of the most common types of oscillator, it can be used for radio frequency (RF), that its output signal is often utilized at the basic of a wireless communication system in most application. In this research, a Colpitts oscillator is comprised from a bipolar junction transistor (BJT) amplifier with <strong>LC</strong> tank. This design is carrying out with a known Barkhausen criterion for oscillation. Firstly, is carried out using theoretical calculation. The secondary is carried out using simulation (Multisim 13). All the obtained result from the above two approaches are 10 MHz and 9.745 MHz respectively. This result is seen to be very encouraging.

scholarly journals High frequency fatigue

1929 ◽  
Vol 125 (796) ◽  
pp. 83-119 ◽  
Keyword(s):  
High Frequency ◽  
Armco Iron ◽  
Fatigue Tests ◽  
Air Pressure ◽  
Magnetic Method ◽  
High Frequencies ◽  
Electro Magnetic ◽  
Very High Frequencies ◽  
Annealed Copper ◽  
Very High

The object of these researches was to determine the effect of the frequency of alternation of stress on the fatigue limits of various metals. The work was carried out in the Engineering Laboratories, Oxford. Tests were made on rolled, normalised and hardened steel; rolled aluminium; annealed copper and normalised armco iron. The ordinary frequency employed in fatigue tests is 50 periods per second. Jenkin in 1924 carried out tests up to 2000 periods per second and in the research described in this paper tests were made at frequencies up to 20,000 periods per second. In all the higher frequency tests the specimen counted of a bar supported at the nodes, and vibrating freely- Jenkin used an electro-magnetic method to produce the vibrations, but this will not work for very high frequencies and a new method had to be invented. In the experiments now described fluctuations of air pressure acting directly on the specimen were used to make them vibrate and a number of methods were tried before a successful apparatus was evolved. The apparatus consists essentially of the two blowers used to vibrate the specimen. Each blower consisted of a small adjustable resonating chamber, into which air was admitted by a throttle valve in the back, while the front was closed by one face of the specimen. The portion of the specimen was so arranged that as it vibrated to and fro it alternately released the air pressure or allowed it to mount up in the chamber. The strains were calculated on the assumption that the bar vibrated freely and the only measurement necessary was the amplitude of vibration at the centre of the bar. Lord Rayleigh has shown how the strains may be calculated for a long, thin vibrating bar. But using the method of vibrating by air, the bars had to have a moderate with and for the biggest speeds they had to be short, so that Lord Rayleigh's theory was no longer sufficiently accurate. The experiments would have been impossible but for the assistance of Prof. Love, who explained how the known theory could be applied to bars of moderate with, such as could be used in our apparatus.

A new method of fluxgate signal extraction

2017 ◽  
Vol 2017 (45) ◽  
pp. 83-89
Author(s):  
A.A. Marusenkov ◽  
Keyword(s):  
High Frequency ◽  
Second Harmonic ◽  
Excitation Frequency ◽  
Low Noise ◽  
Measuring System ◽  
Signal Extraction ◽  
Fluxgate Magnetometer ◽  
New Approach ◽  
Average Value ◽  
The Time Domain

Using dedicated high-frequency measuring system the distribution of the Barkhausen jumps intensity along a reversal magnetization cycle was investigated for low noise fluxgate sensors of various core shapes. It is shown that Barkhausen (reversal magnetization) noise intensity is strongly inhomogeneous during an excitation cycle. In the traditional second harmonic fluxgate magnetometers the signals are extracted in the frequency domain, as a result, some average value of reversal magnetization noises is contributed to the output signals. In order to fit better the noise shape and minimize its transfer to the magnetometer output the new approach for demodulating signals of these sensors is proposed. The new demodulating method is based on information extraction in the time domain taking into account the statistical properties of cyclic reversal magnetization noises. This approach yields considerable reduction of the fluxgate magnetometer noise in comparison with demodulation of the signal filtered at the second harmonic of the excitation frequency.

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