The Foundations of Alternate Current Theory

Nature ◽  
1910 ◽  
Vol 84 (2123) ◽  
pp. 6-7
Author(s):  
GISBERT KAPP
Keyword(s):  
Alternate Current ◽  
Current Theory

scholarly journals Alternate current measurement

1908 ◽  
Vol 80 (539) ◽  
pp. 310-352
Keyword(s):  
Alternate Current ◽  
Current Theory ◽  
High Ratio ◽  
Quadratic Functions ◽  
Wave Form ◽  
Numerical Comparison ◽  
Sine Law ◽  
The Magnetic Field ◽  
Exciting Voltage ◽  
Careful Design

The lack of precision of measurements with alternate currents, as compared with those using direct currents, is mainly due to the relative sensitiveness of the instruments available for such tests. The fact that the turning moment acting on the moving system depends in one case on the square of the current and in the other on the first power of the current, readily explains the high ratio between the currents needed to cause the minimum measurable deflection in the two cases, but this ratio is, nevertheless, most striking when a numerical comparison is actually made on some fair basis. The only likely way at present of improving alternate current instruments is to use iron cored electromagnets to increase the strength of the magnetic field. I have found that the difficulties due to varying permeability and hysteresis of the iron can be avoided by exciting the electromagnet in shunt. It proves possible, with careful design, to construct an electromagnet whose flux is connected with the exciting voltage by a strict mathematical law involving no variable physical properties like permeability, etc. Such an electromagnet is eminently suited for measuring purposes. The theoretical and experimental study of instruments constructed on this principle has brought out certain novel points which are set forth in the present paper. The first part discusses the mathematical relations of cyclic quantities having a common fundamental period, and constitutes a development of a method already published. This method is the only one known to me which is independent of assumptions in regard to the wave form of the quantities dealt with. The usual methods, which are based on the erroneous assumptions of sine law wave form, are not any simpler in working, and are most unsatisfactory when the accuracy of new results has to be critically examined. All alternate current measurements refer to mean squares or to mean products, and the natural method of obtaining the connections between such squares and products is to study the properties of quadratic functions of the variables. The earliest instance of this in alternate current theory was in connection with the “three voltmeter method.” Such processes lead to a very simple form of calculus appropriate to cyclic quantities.

I/O Psychology: A Volume on Current Theory and Method

1995 ◽  
Vol 40 (12) ◽  
pp. 1142-1145
Author(s):  
Mary Roznowski
Keyword(s):  
Current Theory

Alternate Current Transformers

1896 ◽  
Vol 42 (1084supp) ◽  
pp. 17330-17331
Author(s):  
J. A. Fleming
Keyword(s):  
Alternate Current ◽  
Current Transformers

Radical Islamism as a Mode of Production

2019 ◽  
Vol 9 (1) ◽  
pp. 81-108
Author(s):  
Masdar Hilmy
Keyword(s):  
Social Sciences ◽  
Current Theory ◽  
Production Theory ◽  
Social Sciences And Humanities ◽  
Norms And Values ◽  
Dominant Structure ◽  
Political Economic ◽  
Theoretical Paradigms ◽  
Epistemological Basis ◽  
Mode Of Production

This article attempts to provide a breakthrough which I call mode of production theory. This theory will be employed to analyze the contemporary phenomenon of radical Islamism. The mode of production theory is meant to bridge the two clashing theoretical paradigms in social sciences and humanities, i.e., Weberian and Marxian. Despite its bridging nature, the paper argues that the two cannot be merged within one single thread. This is because each paradigm has its own epistemological basis which is irreconcilable to one another. Mostly adapted from Marx’s theory, the current theory of the mode of production covers five interrelated aspects, namely social, political, economic, cultural, and symbolic structures. If Marx’s mode of production theory heavily relies on a material and economic basis, the theory used in this paper accommodates cultural and symbolic structures that are Weberian in nature. Although the two paradigms can operate together, the strength of structure (Marxian) overpowers the strength of culture (Weberian). This paper further argues that such cultural-based aspects as ideology, norms, and values play as mobilizing factors under a big schematic dominant structure in the rise and development of the radical Islamist groups.

An easy and low-cost biomagnetic methodology to study regional gastrointestinal transit in rats

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Leonardo Pinto ◽  
Guilherme Soares ◽  
André Próspero ◽  
Erick Stoppa ◽  
Gabriel Biasotti ◽  
...  
Keyword(s):  
Low Cost ◽  
Gastrointestinal Transit ◽  
Alternate Current ◽  
Phenol Red ◽  
Distal Small Intestine ◽  
Reliable Assessment ◽  
Imaging Approach ◽  
Magnetic Tracer ◽  
Tracer Distribution ◽  
Gi Transit

Abstract The identification of gastrointestinal (GI) motility disorders requires the evaluation of regional GI transit, and the development of alternative methodologies in animals has a significant impact on translational approaches. Therefore, the purpose of this study was to validate an easy and low-cost methodology (alternate current biosusceptometry – ACB) for the assessment of regional GI transit in rats through images. Rats were fed a test meal containing magnetic tracer and phenol red, and GI segments (stomach, proximal, medial and distal small intestine, and cecum) were collected to assess tracer’s retention at distinct times after ingestion (0, 60, 120, 240, and 360 min). Images were obtained by scanning the segments, and phenol red concentration was determined by the sample’s absorbance. The temporal retention profile, geometric center, gastric emptying, and cecum arrival were evaluated. The correlation coefficient between methods was 0.802, and the temporal retention of each segment was successfully assessed. GI parameters yielded comparable results between methods, and ACB images presented advantages as the possibility to visualize intrasegmental tracer distribution and the automated scan of the segments. The imaging approach provided a reliable assessment of several parameters simultaneously and may serve as an accurate and sensitive approach for regional GI research in rats.

scholarly journals Sexual selection favours male parental care, when females can choose

2011 ◽  
Vol 279 (1734) ◽  
pp. 1784-1790 ◽  
Author(s):  
Suzanne H. Alonzo
Keyword(s):  
Sexual Selection ◽  
Parental Care ◽  
Female Choice ◽  
Mating Success ◽  
Current Theory ◽  
Sharp Contrast ◽  
Recent Theory ◽  
Extra Pair Paternity ◽  
Female Promiscuity ◽  
Male Care

Explaining the evolution of male care has proved difficult. Recent theory predicts that female promiscuity and sexual selection on males inherently disfavour male care. In sharp contrast to these expectations, male-only care is often found in species with high extra-pair paternity and striking variation in mating success, where current theory predicts female-only care. Using a model that examines the coevolution of male care, female care and female choice; I show that inter-sexual selection can drive the evolution of male care when females are able to bias mating or paternity towards parental males. Surprisingly, female choice for parental males allows male care to evolve despite low relatedness between the male and the offspring in his care. These results imply that predicting how sexual selection affects parental care evolution will require further understanding of why females, in many species, either do not prefer or cannot favour males that provide care.

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