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Articles 1141 - 1153 of 1153

Full-Text Articles in Physical Sciences and Mathematics

A Unified Topological Approach To Electromagnetic Environmental Effects Protection, George H. Baker, J. Philip Castillo, Edward F. Vance Jun 1995

A Unified Topological Approach To Electromagnetic Environmental Effects Protection, George H. Baker, J. Philip Castillo, Edward F. Vance

George H Baker

The presentation recommends an approach for unifying electronic system protection designs for a wide spectrum of electromagnetic environments. A general electromagnetic topological construct is developed as the basis for a consistent shielding and terminal protection methodology. Spectral characteristics of multiple interfering electromagnetic sources, both internal and external, are described. Effects addressed include EMI/EMC, lightning, nuclear EMP, and RF weapons. Protection practices for individual effects are discussed and means for integrating these into a single protection topology.

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The Spectral Center Of Gravity Effect And Auditory Filter Bandwidth, Marc Fagelson, Linda M. Thibodeau Nov 1994

The Spectral Center Of Gravity Effect And Auditory Filter Bandwidth, Marc Fagelson, Linda M. Thibodeau

Marc A. Fagelson

The spectral center of gravity refers to a listener’s averaging of frequency and intensity components when formant peaks in a speechlike signal are separated by 3.5 Bark units or less. In this paper a total of 18 synthetic vowels whose spectra approximated /ae/ or /inverted vee/ were generated digitally; each stimulus contained the first 40 harmonics of a 100‐Hz fundamental. Nine spectra contained three formants, while the balance contained only two. Subjects with normal hearing and mild high‐frequency hearing loss above 3000 Hz were instructed to identify synthetic vowels as either /ae/ or /inverted vee/ as F2 frequency was …

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Click‐Evoked Otoacoustic Emissions In Normal‐Hearing Children, Jacek Smurzynski Jan 1994

Click‐Evoked Otoacoustic Emissions In Normal‐Hearing Children, Jacek Smurzynski

Jacek Smurzynski

Click‐evoked otoacoustic emissions (CEOEs) were collected from 167 ears of 106 normal‐hearing children using the ILO88 system with the stimuli presented at 80±2 dB pe SPL. Subjects were divided into five age groups: 13–24 months (24 ears), 25–36 months (49 ears), 37–48 months (31 ears), 49–60 months (34 ears), and 61–72 months (29 ears). All subjects had normal middle ear function and their audiological data were within normal limits. Mean overall CEOE level was calculated for each age group. None was statistically different from any other. However, the data of the 167 ears showed small but statistically significant decrease in …

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Comparison Of Suppression Across Frequencies, Linda M. Thibodeau, Marc A. Fagelson Nov 1993

Comparison Of Suppression Across Frequencies, Linda M. Thibodeau, Marc A. Fagelson

Marc A. Fagelson

Although much research has focused on the temporal, spectral, and intensity relationships between a masker and a suppressor, there has been little attention directed towards relative amounts of suppression in different frequency regions. The purpose of this experiment was to compare the magnitude of suppression at 500 and 2000 Hz in two forward‐masking experiments with seven normal‐hearing persons. In the first experiment, the threshold for a 10‐ms probe was determined as the bandwidth of a 400‐ms masker increased from 0.05 to 1.6 times the probe frequency. Suppression was determined by observing a decrease in threshold when the masker bandwidth exceeded …

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Strength Of Bentonite Water-Well Annulus Seals In Confined Aquifers, Fred Ogden Feb 1993

Strength Of Bentonite Water-Well Annulus Seals In Confined Aquifers, Fred Ogden

Fred L. Ogden

The advantages of bentonite clay for sealing applications are well known. Bentonites have extremely low permeability, do not affect formation water chemistry, and have the ability to swell and deform in response to subsurface changes. The major limitation on the applicability of bentonite for water well annulus sealing is strength. Strength tests conducted in a physical model of a water well identified the expected magnitude of shear strength for several commercially available bentonite well-sealing products. The dependence of bentonite strength in the annulus of a water well on both setting time and borehole geometry is discussed. Force balance calculations for …

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Sliding Mode Control Of The Systems With Uncertain Direction Of Control Vector, Sergey V. Drakunov Dec 1992

Sliding Mode Control Of The Systems With Uncertain Direction Of Control Vector, Sergey V. Drakunov

Sergey V. Drakunov

No abstract provided.

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Nuclear Emp Hardening Approach As The Basis For Unified Electromagnetic Environmental Effects Protection, George H. Baker Iii Dec 1991

Nuclear Emp Hardening Approach As The Basis For Unified Electromagnetic Environmental Effects Protection, George H. Baker Iii

George H Baker

Operation DESERT STORM demonstrated the clear military advantage that was provided by our sophisticated electronic C4I and weapons systems. High tech means so dominate the battlefield that the outcome of future conflicts could be decided by electronics attrition rather than human casualties. However, the electromagnetic threat landscape is highly complex. The already formidable list of environments (EMI, lighting, ESD, EMP, HERO, TEMPEST, EW, etc.) is lengthened by emerging threats from high power microwave (HPM) and ultra-wide band (UWB) electromagnetic weapons. Many of these environments overlap in the frequency and amplitude of the electrical stresses they create.

The large number of …

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Sliding-Mode Observers Based On Equivalent Control Method, Sergey V. Drakunov Dec 1991

Sliding-Mode Observers Based On Equivalent Control Method, Sergey V. Drakunov

Sergey V. Drakunov

No abstract provided.

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Setting Time Effects On Bentonite Water-Well Annulus Seals, Fred L. Ogden Jun 1991

Setting Time Effects On Bentonite Water-Well Annulus Seals, Fred L. Ogden

Fred L. Ogden

Shear strength tests are conducted in a model of a water well on four, commercially available, granular bentonite well sealing products. The time dependency of annulus seal shear strength and resistance to piping is examined. Dry bentonite samples are placed through water in the annular space between the casing and borehole and allowed to set for a specified time. Pressure is applied at a constant rate to one end of the clay seal until shear or piping failure occurs. Pressure and seal displacement data are recorded on a digital data acquisition system. Annulus seal strength and resistance to piping increase …

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Progress In The Development Of Hemp Protection Standards For C3i Facilities, George H. Baker, Clinton R. Gordon Apr 1989

Progress In The Development Of Hemp Protection Standards For C3i Facilities, George H. Baker, Clinton R. Gordon

George H Baker

DoD is involved in EMP standards development efforts which culminate 25 years of research. This paper previews an EMP protection standard for fixed, ground-based communication facilities. The standard uses a low-risk hardening approach which depends on an electromagnetic barrier comprised of a conducting shield to prevent harmful transients from reaching communication electronics. The standard is the first of its kind and is being instituted as MIL-STD-188-125.

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Pitch Of Complex Tones With Many High‐Order Harmonics, Adrianus J. M. Houtsma, J. Smurzynski Jan 1989

Pitch Of Complex Tones With Many High‐Order Harmonics, Adrianus J. M. Houtsma, J. Smurzynski

Jacek Smurzynski

Pitch identification and pitch discrimination experiments were performed for complex tones with missing fundamentals between 200 and 300 Hz and with many successive harmonics varying from low (below the 10th) to high (above the 25th) harmonic order. Identification performance was found to degrade with increasing harmonic order from an essentially perfect to an asymptotic level that was clearly less than perfect but much better than chance. Just‐noticeable differences in (missing) fundamental frequency were found to increase, with increasing harmonic order, from a fraction of 1 Hz to an asymptotic level of about 5 Hz. Influence of phase was found only …

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Electro-Optics Applications For Alleviating Emi/Emc/Emp Problems, George H. Baker, Walter H. Hardwick Apr 1982

Electro-Optics Applications For Alleviating Emi/Emc/Emp Problems, George H. Baker, Walter H. Hardwick

George H Baker

No abstract provided.

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Emp Analysis Of An Fm Communications Radio With A Long Wire Antenna, George H. Baker Iii, Werner J. Stark May 1978

Emp Analysis Of An Fm Communications Radio With A Long Wire Antenna, George H. Baker Iii, Werner J. Stark

George H Baker

A Norton equivalent circuit is developed for a long-wire antenna used with a VHF man-pack FM radio exposed to an incident electromagnetic pulse (EMP). The required short-circuit current and antenna impedance are computed by use of a transmission-line model for the antenna, and the computations are compared with measurements of the short-circuit current and antenna impedance. The comparison shows that the transmission-line model for the antenna is adequate for performing a vulnerability analysis of the radio. A network model is developed for a portion of the radio and is used as the load in the Norton equivalent circuit. Load currents …

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