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	Heinrich Barkhausen - Wikipedia, the free encyclopedia
		Heinrich Georg Barkhausen (December 2, 1881 - February 20, 1956), born at Bremen was a German physicist.
		He discovered in 1919 an effect named after him, the Barkhausen effect, which suggested that ferromagnetic materials contain regions of like-oriented atoms.
		Another contribution of his, the Barkhausen Criterion states that an oscillator will oscillate when the total phase shift from input to output back to input is 360 degrees and the system gain is at least 1.
	en.wikipedia.org /wiki/Heinrich_Barkhausen (220 words)

	barkenhausen effect scalar detector zpe bearden bifilar caduceus
		The Barkhausen effect detector detects minute modulations of the intensity of the field of a set of shielded permanent magnets that bias a specially selected nonlinear magnetic core material to a critical level of magnetization, the most non linear region of the B / H curve for the core material used.
		In the Barkhausen effect scalar detector, the core material is biased to the critical point in a divergent magnetic field produced by permanent magnets that are shielded from external electromagnetic fields.
		The Barkhausen effect detector, and other magnetostatic detectors, may be given a slight "directional" preference to their response by making the path of the magnetic flux through the core larger in area than the remainder of the magnetic flux circuit.
	www.amasci.com /freenrg/bark.html (6391 words)

	Harmonic frequency analysis of acoustic Barkhausen noise on neutron irradiated material
		The neutron irradiation caused the coercivity to increase, whereas susceptibility to decrease.
		The Barkhausen noise signals reflect the statistical nature of both the number of event and individual pulse height via the degree of overlapping in the detector coil, in which the individual pulse is signified by the irreversible wall motion.
		Therefore, the decrease of Barkhausen noise amplitude in neutron irradiated specimen is attributed to the hindrance of the domain wall induced by defect clusters.
	www.ndt.net /article/wcndt00/papers/idn337/idn337.htm (1769 words)

	The Barkhausen effect \| Plant Services
		Barkhausen emission technique is an easy-to-use, semi-quantitative technique for monitoring changes in near surface stress distribution or microstructure of ferromagnetic machinery components.
		Because Barkhausen signals originating near the surface of the sample are richer in high-frequency components than signals originating deeper in the material, bandwidth filters provide a way to estimate the depth from which the MBE activity is occurring.
		Barkhausen emission analysis is a relatively inexpensive nondestructive evaluation method for monitoring changes in the condition of ferromagnetic components during service.
	www.plantservices.com /articles/2006/075.html (1742 words)

	Heinrich Barkhausen
		Barkhausen attended the universities of Munich and Berlin before earning his doctorate in 1907 from Göttingen.
		His work in acoustics and magnetism led to the discovery in 1919 of the Barkhausen effect, which provided evidence that magnetization affects whole domains of a ferromagnetic material, rather than individual atoms alone.
		In 1920 Barkhausen developed, with Karl Kurz, the Barkhausen-Kurz oscillator for ultrahigh frequencies (a forerunner of the microwave tube), which led to the understanding of the principle of velocity modulation.
	www.fys.kuleuven.ac.be /pradem/fysici/Barkhausen.htm (170 words)

	Barkhausen Noise Analysis by Surrounding Coil by J (Site not responding. Last check: 2007-10-30)
		Understanding and analyzing variations of Barkhausen signals from different investigations and applications (microstructural changes, internal stresses, etc.) needs a knowledge of physical mechanisms that occur in the measuring process.
		It is based on the fact that an initial Barkhausen event is attenuated with the distance between the source (Bloch wall motion) and the detecting coil.
		Barkhausen, H. Zwei mit Hilfe der neuen Verstärker entdeckte Erscheinungen.
	www.cnde.iastate.edu /QNDEDatabase/Vol.14B/p1693-1700.html (331 words)

	Barkhausen
		Barkhausen's work in acoustics and magnetism led to the discovery in 1919 of the Barkhausen effect, which provided evidence that magnetization affects whole domains of a ferromagnetic material, rather than individual atoms alone.
		Heinrich Barkhausen discovered that a slow, smooth increase of a magnetic field applied to a piece of ferromagnetic material, such as iron, causes it to become magnetized, not continuously but in minute steps.
		Barkhausen Noise Analysis (BNA) method is based on the Barkhausen effect.
	www.geocities.com /neveyaakov/electro_science/barkhausen.html (645 words)

	Stresstech - Barkhausen Noise Analysis
		Barkhausen Noise Analysis (BNA) method, also referred to as the Magnetoelastic or the Micromagnetic method is based on a concept of inductive measurement of a noise-like signal, generated when magnetic field is applied to a ferromagnetic sample.
		After a German scientist Professor Heinrich Barkhausen who explained the nature of this phenomenon already in 1919, this signal is called Barkhausen noise.
		Barkhausen noise has a power spectrum starting from the magnetizing frequency and extending beyond 2 MHz in most materials.
	www.stresstech.fi /products?id=85&c=1&l=1&parent=1&s=2 (666 words)

	Barkhausen Demodulation by B (Site not responding. Last check: 2007-10-30)
		Unfortunately, Barkhausen noise signals are broadband, weak, and, hence, difficult to measure.
		An alternative method of measuring Barkhausen noise based on the Loomis effect is described in which an amplitude modulated, high frequency magnetic field is demodulated in the presence of a ferromagnetic material subjected to a slowly varying magnetic field.
		A particular application in which Barkhausen Demodulation was used to measure the hardness of X40 grade pipeline steel is described.
	www.cnde.iastate.edu /qndedatabase/Vol.14B/p1709-1716.html (259 words)

	Southwest Research Institute (SwRI) News Release
		Known as the Barkhausen Noise Stress Measurement System, Series 200, the development was selected as a winner in the 1981 I-R 100 competition conducted by Industrial Research and Development, officials of the publication announced Thursday in Chicago.
		To detect and measure stresses such as these, the Barkhausen noise method makes use of the distinctive behavior of magnetic domains, small regions of local magnetization oriented in various directions within a ferromagnetic material (such as iron, steel, nickel, cobalt, or alloys of like magnetic character).
		The amplitude of Barkhausen signals, for instance, is known to increase with increasing tensile stress, and to decrease with growing compressive stress.
	www.swri.org /9what/releases/Pre1996/noisestr.htm (649 words)

	Residual Stress Measurement in Steel Mill Rolls Using Magnetic Barkhausen Noise Analysis
		The exact choice of the steel alloy composition used for a steel mill roll, the prediction of its performance as well as the monitoring of its condition in operation are difficult and responsible tasks of metallurgists.
		Barkhausen noise has a power spectrum starting from the magnetising frequency and extending beyond 2 MHz in most ferromagnetic materials.
		Calibration curves are obtained by measuring the level of Barkhausen noise while stressing the test piece in compression and tension.
	www.ndt.net /article/v04n08/wojtas/wojtas.htm (2543 words)

	The Barkhausen Effect experiment by Jean-Louis Naudin
		The sudden, discontinuous jumps in magnetization may be detected by a coil of wire wound on the ferromagnetic material; the sudden transitions in the magnetic field of the material produce pulses of current in the coil that, when amplified, produce a series of clicks in a loudspeaker.
		I recommend you use a current transformer with a ferrite core instead of a simple coil with a ferrite core, because you will a avoid some interferences with the parasitic EM induction from the 50 or 60 Hz coming from the power grid.
		The most interesting in the Barkhausen effect is that there are no magnetic links between the source (the 2Hz flat excitation coil) and the EM induction produced by the Barkhausen jumps inside ferrite toroid core.
	jlnlabs.imars.com /spgen/barkhausen.htm (392 words)

	HCGL Manuscripts: GLMS-46, Henry N. Barkhausen Collection
		A native of Green Bay, Wisconsin, Barkhausen was born in 1914 into a community actively engaged in the commercial and recreational exploitation of the Great Lakes environment.
		With a growing reputation as an effective business manager and as a committed environmentalist, Barkhausen was able to enter the Illinois political structure with a goal of harmonizing seemingly incompatible constituencies.
		With his quarries located near the federal wetland area, Barkhausen was able to show businessmen and environmentalists a clear example of harmonized goals coming from antagonistic sources.
	www.bgsu.edu /colleges/library/hcgl/glms0046.html (806 words)

	Illinois Conservation Foundation (ICF) Press Releases
		Barkhausen led an unprecedented land acquisition effort resulting in more than 15,000 acres being added and developed in the state park system.
		Barkhausen established the Department's natural heritage division to enhance protection of non-game fish and wildlife and unique natural areas.
		Barkhausen's greatest legacy may be his work of more than 30 years on protection, restoration and preservation of the Cache River wetlands in southern Illinois.
	www.ilcf.org /PR3Inductees.htm (955 words)

	Barkhausen effect and hysteresis
		The Barkhausen effect was first observed in 1919 in the magnetization curve of ferromagnets.
		The Barkhausen effect is due to the disorder in the material wich is responsible for the jerky motion of domain walls.
		We investigated the scaling properties of the Barkhausen effect, recording the noise in several soft ferromagnetic materials: polycrystals with different grain sizes and amorphous alloys.
	pil.phys.uniroma1.it /~zapperi/bark.html (586 words)

	Barkhausen Effect (Site not responding. Last check: 2007-10-30)
		When the array is tapped sharply, it will be seen that the needles on the boundaries of the domains are the least stable (vibrate the most), and some of them realign causing one domain to grow at the expense of another.
		In the Barkhausen effect, a large coil of fine wire is connected through an amplifier to a speaker.
		When an iron rod is placed within the coil and stroked with a magnet, an audible roaring sound will be produced from the sudden realignments of the magnetic domains within the rod.
	www.physics.ucla.edu /demoweb/demomanual/electricity_and_magnetism/magnetostatics/barkhausen_effect.html (212 words)

	diyAudio Forums - Barkhausen noise in drivers and inductors (Site not responding. Last check: 2007-10-30)
		Well, the resolution (or dynamic range) of a system is limited by on the one hand the max level, on the other hand the noise floor.
		And with loudspeaker drivers that have significant peak-to-peak stroke (woofers, full-range units etc.), the inductance of the voice-coil will change depending on where it is in the gap.
		I could be wrong, but in principle, why would the Barkhausen effect apply to speakers, since my understanding is that you are not magnetizing or demagnetizing anything (at least in the ideal case).
	www.diyaudio.com /forums/showthread.php?postid=60559 (900 words)

	Research - Mechanical and Systems Engineering - University of Newcastle
		Magnetic Barkhausen emission technique for detecting the overstressing during bending fatigue in case-carburised En36 steel.
		Magnetic Barkhausen emission technique for evaluation of residual stress alteration by grinding in case-carburised En36 steel.
		Magnetic Barkhausen Noise: The Influence of Microstructure and Deformation in Bending.
	www.ncl.ac.uk /mech/research/publications?staff=0739 (315 words)

	Barkhausen Stability Criterion
		The Barkhausen Stability Criterion is simple, intuitive, and wrong.
		During the study of the phase margin of linear systems, this criterion is often suggested by students grasping for an intuitive understanding of stability.
		The history of the Barkhausen Stability Criterion is an unfortunate one.
	web.mit.edu /klund/www/weblatex/node4.html (588 words)

	The eBearing Glossary of Bearing Industry Terms > B
		Named for Heinrich Barkhausen (1881-1956), German professor who predicted the phenomenon of small magnetization "jumps" between Weiss domains in magnetized ferrous materials.
		In 1919, Professor Barkhausen induced and detected the shocks or jumps, feeding the energy to a loudspeaker.
		In the bearing industry, BNA is used to determine case depth, pinpoint metal fatigue, identify grinding abuse, generate stress profiles and identify other material attributes.
	www.ebearing.com /glossary/b.html (811 words)

	NDT & E International, 29 (5) "Special Issue: 8TH APCNDT". (Site not responding. Last check: 2007-10-30)
		Barkhausen noise used as a nondestructive evaluation technic of mechanical damage (In French)
		Magnetic Barkhausen effect studies in the evaluation of neutron irradiation degradation in nuclear pressure vessel steels
		Application of the Barkhausen effect in inspection of the state of stress of parts made of high-strength steel
	www1.elsevier.com /cdweb/journals/09638695/viewer.htt?vol=29&viewtype=issue&iss=5 (1814 words)

	Paging Dr. Barkhausen... - Designing Ideas - Blog on EDN - 910000091
		Another staffer at EDN inserted a last-minute reference to the Barkhausen Effect, which has nothing to do with the Barkhausen Criterion for Oscillation.
		I'm not quite done with Dr. Barkhausen yet— the legacy of his work spans an amazing range from VLF radio phenomena to the first transit-time microwave vacuum tubes.
		Early-model television receivers occasionally suffered from undesirable Barkhausen oscillations (sometimes referred to as "snivets") generated by electrons trapped and recirculated between the screen grid and plate of the receiver's horizontal output tube.
	www.edn.com /blog/910000091/post/1070002707.html?nid=2786 (737 words)

	Micromagnetic Surface Measurements for Evaluation of Surface Modifications Due to Cyclic Stress -- from Mathematica ...
		The magnetic hysteresis method can detect fatigue damage in the later stages of fatigue life.
		Magnetic Barkhausen signals, being highly sensitive to the surface condition of a material, show a continuous change during the whole fatigue process.
		Barkhausen effect measurement, aided by signal processing techniques, is therefore capable of monitoring surface modifications due to cyclic stress.
	library.wolfram.com /infocenter/Articles/1864 (98 words)

	PIRA 5G20.00 MAGNET DOMAINS AND MAGNETIZATION (Site not responding. Last check: 2007-10-30)
		A set of magnetic needles on pivots orients randomly until a magnet is brought close.
		Barkhausen model - A compass array above an electromagnet will show that the needles align discontinuously as the field is increased.
		A simple mechanical model demonstrates phase transitions in a Heisenberg antiferromagnet.
	www.physics.ncsu.edu /pira/5eandm/5G20.html (781 words)

	Analysis of the Barkhausen Effect (Site not responding. Last check: 2007-10-30)
		Ferromagnetic materials exhibit jumps in magnetization in the presence of an applied magnetic field of increasing strength.
		This phenomenon is commonly known as the Barkhausen effect.
		The effect is a result of the motion of domain wall boundaries of the material in response to a fluctuating field.
	math.nist.gov /reports/division/yearly/subsection2_2_1_11.html (154 words)

	Daubechies Wavelets and Mathematica -- from Mathematica Information Center
		Examples of the wavelet transform applied to selected time series are presented to highlight the advantages of wavelets.
		We indicate an application of wavelets to sampled Barkhausen noise, a nonlinear phenomenon encountered in magnetic systems.
		The elements of the WaveletTransform package are discussed, with the emphasis being on the calculation of filter coefficients and their application to the discrete wavelet transform (DWT) and its inverse.
	library.wolfram.com /infocenter/Articles/1984 (158 words)

	Magnetic Barkhausen Noise (Site not responding. Last check: 2007-10-30)
		Our magnetic Barkhausen noise (MBN) probes are based on the Barkhausen effect.
		The figure below shows a typical magnetization curve, with B, the flux density, appearing to be a continuous function of H, the magnetic field.
		These discontinuous changes are a result of the Barkhausen effect - small magnetization 'jumps' due to domain walls becoming pinned and released from microstuctural obstacles such as grain boundaries, second phase particles, and non-metallic inclusions.
	www.physics.queensu.ca /~lynann/mbnoise.html (170 words)

	Mathematical modelling of barkhausen jump size distributions by Fern Y. Hunt
		Ferromagnetic materials exhibit jumps in magnetization in the presence of an applied magnetic field of increasing strength, a phenomenon that is commonly known as the Barkhausen effect.
		The pattern of jumps gives important information about the material microstructure and the Barkhausen signal is used to characterize photo-optical devices, computer storage and recording media.
		The pinning field associated with the movement of magnetic domain walls is modelled as a reversible Markov Chain.
	www.ima.umn.edu /hpc/wkshp_abstracts/hunt1.html (152 words)

	Brown County Parks - Barkhausen Waterfowl Preserve (Site not responding. Last check: 2007-10-30)
		Located along the west shore of the Bay of Green Bay, the Barkhausen Waterfowl Preserve has 920 acres of forest, meadows and wetlands where prehistoric Indian tribes once hunted, fished, and camped.
		Today this natural area is home and refuge for a wide variety of waterfowl, wildlife, and plant species.
		Park entrance is about half mile ahead on the right.
	www.co.brown.wi.us /Parks/parks/barkhausen/index.shtml (158 words)

	The Barkhausen effect (Site not responding. Last check: 2007-10-30)
		The Barkhausen effect occurs during the magnetization process of a ferromagnetic material.
		It is due to the jerky motion of the Domain Walls, under a variable external field.
		This is a simulation of the Barkhausen noise (see the other pages for real signals, sounds, and associated hysteresis loops)
	www.ien.it /~durin/barkh.html (230 words)

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