Estimation Of Quality Factor Research Articles

Ohmic Quality Factor and Efficiency Estimation for a Gyrotron Cavity

Ohmic Quality Factor and Efficiency Estimation for a Gyrotron Cavity

ML Amplitude Tomography in North China

We have selected 10,899 M L amplitude readings from 1732 events re- corded by 91 stations, as reported in the Annual Bulletin of Chinese Earthquakes (ABCE), and have used tomographic imaging to estimate the lateral variations of the quality factor Q0 (Q at 1 Hz) within the crust of Northern China. Estimated Q0 values vary from 115 to 715 with an average of 415. Q0 values are consistent with tectonic and topographic structure in Eastern China. Q0 is low in the active tectonic regions having many faults, such as the Shanxi and Yinchuan Grabens, Bohai Bay, and Tanlu Fault Zone, and is high in the stable Ordos Craton. Q0 values are low in several topographically low-lying areas, such as the North China, Taikang-Hefei, Jianghan, Subei-Yellow Sea, and Songliao basins, whereas it is high in mountainous and uplift regions exhibiting surface expressions of crystalline basement rocks: the Yinshan, Yanshan, Taihang, Qinlin, Dabie and Wuyi Mountains, and Luxi and Jiaoliao Uplifts. Quality-factor estimates are also consistent with Pn- and Sn-velocity patterns. High- velocity values, in general, correspond with high Q0 and low-velocity values with low Q0. This is consistent with a common temperature influence in the crust and uppermost mantle.

Threshold-crossing counting technique for damping factor determination of resonator sensors

The behavior of resonator-type sensors at resonance is characterized by two fundamental parameters: resonance frequency and damping factor (or Q-factor). Practical applications require accurate and efficient measurements of these two parameters. Using magnetoelastic resonant sensors as a test case earlier work [K. Zeng, K. G. Ong, C. Mungle, and C. A. Grimes, Rev. Sci. Instrum. 73, 4375 (2002)] demonstrated the ability to determine resonance frequency by counting the number of cycles in the transient response of a pulsewise excited sensor. Presented in this paper is a novel technique for measuring the damping factor of a resonant magnetoelastic sensor, or any resonator type sensor, using threshold-crossing counting of the transient response. The damping factor determination technique eliminates the need for a lock-in amplifier or FFT analysis as in the conventional method of quality factor estimation from spectrum analysis, significantly simplifying the electronic implementation as well as improving measurement speed and accuracy.

Estimation of resonant frequencies and quality factors from time domain computations

A new frequency domain subspace algorithm for the estimation of resonant frequencies and quality factors given the output from time domain computations is developed and tested. It applies the discrete Fourier transform to the time domain signal and the estimates are computed from the frequency data within the frequency band of interest. Thus, out-of-band disturbances are suppressed through a band-pass filtering operation in frequency domain, which is free from the transient effects that are inevitable for standard time domain filtering techniques. We also propose an efficient procedure to generate short time domain excitations with an a priori specified frequency spectrum. By combining such excitations with the frequency domain subspace algorithm, we estimated to high accuracy the lowest 167 resonant frequencies of a three-dimensional bow-tie microwave resonator given two separate time domain computations with, in total, 23,000 time steps. A free-space computation for a cavity with an aperture shows that the estimation algorithm can be used to efficiently and accurately extrapolate time domain signals. The tests show that it is possible to reduce the overall computation time by several orders of magnitude for systems with undamped or weakly damped modes. It operates as a post-processing step and, thus, decouples the estimation of frequencies and amplitudes from the time-domain solver which offers a considerable flexibility.

Estimation of quality factors from CMP records

Estimates of the quality, Q, factor are commonly obtained from vertical seismic data or stacked surface seismic data. This paper describes a method that allows Q‐factor to be estimated directly from common midpoint (CMP) gathers. Absorption of the wavefield is dependent on three parameters: frequency, traveltime in the medium, and medium Q‐factor. Assuming that the amplitude spectrum of the seismic source signature may be modeled by that of a Ricker wavelet, we derive an analytical relation between Q‐factor and seismic data peak frequency variation both along offset and vertical time direction. The Q‐factor is estimated from CMP gathers using a layer‐stripping approach.

On determining the maximum emissions from electrically large sources

This paper examines the use of measurements of the total radiated power from an arbitrary source, combined with theory-based estimates of directivity or quality factor, to accurately predict the maximum electric field radiated by the source either at a line-of-sight distance or in a resonant volume. The approach using total radiated power avoids source rotations during testing and is an efficient alternative to current emission test methods. Examples of simulated (random source set) and measured (box with holes) planar-cut radiation-patterns for electrically large sources are presented. Both simulated and measured data agree well with theoretical estimates.

Accurate full wave estimation of quality factor and resonance frequency of HTS microstrip resonator

The spectral domain technique is employed to estimate characteristics of a high temperature superconducting (HTS) microstripline resonator taking into account most of the practical operating conditions to provide accurate representation of device performance. This analysis is expected to be quite useful in CAD of high Q resonators and sharp cutoff filters used in microwave communications.

Frequency dependent Lg attenuation in south‐central Alaska

The characteristics of seismic energy attenuation are determined using high frequency Lg waves from 27 crustal earthquakes, in south‐central Alaska. Lg time‐domain amplitudes are measured in five pass‐bands and inverted to determine a frequency‐dependent quality factor, Q(f), model for south‐central Alaska. The inversion in this study yields the frequency‐dependent quality factor, in the form of a power law: Q(f)=Q0 fη = 220(±30) f0.66(±0.09) (0.75≤f≤12Hz). The results from this study are remarkably consistent with frequency dependent quality factor estimates, using local S‐wave coda, in south‐central Alaska. The consistency between S‐coda Q(f) and Lg Q(f) enables constraints to be placed on the mechanism of crustal attenuation in south‐central Alaska. For the range of frequencies considered in this study both scattering and intrinsic attenuation mechanisms likely play an equal role.

S wave attenuation in the coastal region of Jalisco–Colima, México

Aftershock data from the October 9, 1995, M=7.6 earthquake, that occurred in the coastal subduction region of Colima–Jalisco, Mexico, are used to obtain estimates of the frequency independent quality factor Q s and spectral decay parameter κ, in the approximate frequency range 3 Hz≤ f≤40 Hz, as functions of hypocentral distance r. A regression analysis results in the relations for S waves: Q s =261.397+3.198r±15.536 κ=0.009651+0.000462r±0.0012. The observed distance dependence of Q s and κ is similar to that reported for the Mexican regions of Oaxaca and Guerrero. Our Q s values agree with those reported for Oaxaca and northern Baja CA for frequencies around 8 Hz, and are somewhat lower (a factor of ∼0.8 to ∼0.5) for higher frequencies around 20 Hz; however, they are significantly lower than all but the lowest values reported for the Guerrero region, attaining factors ∼0.25 and ∼0.13 for frequency ranges around 8 and 20 Hz, respectively. It thus appears that the Guerrero region has an anomalously low attenuation compared with the flanking coastal regions of Oaxaca–Chiapas to the SE and Jalisco–Colima to the NW.

Space radiation quality factor investigations with “NAUSICAA”-device on board the “MIR” space station

The estimation of radiation quality factor in space flights is a serious problem of space dosimetry. The solution of this problem is based on LET-spectra measurements. The “NAUSICAA”-device installed on the “MIR” station has a detector with a large geometric factor, that gives the possibility of measuring LET-spectra with sufficient statistic in relatively short time interval and hence the corresponding Q. LET-spectra are accumulated through 24 hour periods and equivalent dose (H), absorbed dose (D), quality factor and flux (F) are measured every 10 minutes. The obtained data permit the estimate of the diurnal Q and Q in South Atlantic Anomaly. These values vary in the range of 1.4 – 2.2. The analysis of these values including their comparison with the calculated results is given in this paper.

Hedonic Estimation of Quality Factors Affecting the Farm‐Retail Margin

AbstractA model of the farm‐retail marketing margin is tested using producer and retail prices of a perishable product in which time during season and quality characteristics are variable. Empirical analysis verifies that the marketing margin of California fresh peaches decreases during the season and increases with improved quality. Results identify potential producer gains from improving product quality early in the season, and from price signals compensating producers for quality characteristics other than weight.

Distributed parameter analysis of dark I–V characteristics of the solar cell: estimation of equivalent lumped series resistance and diode quality factor

The present investigation deals with the distributed parameter analysis of the p–n junction solar cell in the current-induced case at low level injection. The theory, for the first time, takes into account the metal–semiconductor contact resistance, along with the base bulk resistance and the diffused layer shear resistance. The transcendentally nonlinear differential equations for the emitter layer current and voltage have been solved analytically. Additionally, expressions for the I–V characteristic and equivalent ‘lumped’ series resistance have been established. Such physical parameters are very useful in the optimisation of the contact finger width and separation. Inclusion of the contact resistance, even for very small values, corresponds to the nonuniform carrier generation within the metallic grid. Therefore, the results are affected both qualitatively and quantitatively. The most important effect has been calculated in the I–V characteristics resulting from an additional contribution to the series resistance. Analysis reveals that the series resistance and the diode quality factor vary with applied current.

Local Characteristics of the fmax of Bedrock Motion in the Tokyo Metropolitan Area, Japan.

On the basis of S-wave acceleration data observed at the bottom of a 2.3 km borehole drilled at the Shimohsa Crustal Activity Observatory (SHM), we studied the source region dependence of the fmax of bedrock motion in the Tokyo metropolitan area. In order to study a variety of fmax in this area, we divided the earthquakes that occurred beneath the Kanto district into six source groups. This division of earthquake sources leads us to the conclusion that the fmax of events that occurred in the boundary zone where the Philippine Sea plate is colliding with the Pacific and Eurasian plates is lower than 10 Hz and that of interplate events is higher than 20 Hz. This conclusion is certified using data recorded at another deep borehole site at Iwatsuki. We cannot deny the existence of source-controlled fmax, on the assumption that the path attenuation effect is independent of source region. Using estimates of frequency-dependent quality factor for S-waves obtained by Aki (1980), we find that the fmax of the source spectrum from events that occurred in the boundary zone where the Philippine Sea plate is colliding with the Pacific plate is about 10 Hz and that from events that occurred in other source regions which do not include the active seismic region in eastern Yamanashi Prefecture, is higher than 25 Hz.

Quality-factor estimation for varicap bodies

Quality-factor estimation for varicap bodies

Estimation of quality factor and RBE for degraded fission neutron spectra.

A number of fission neutron spectra which were obtained under various conditions of neutron moderation and shielding have been analysed to yield distribution of dose in LET. From this analysis parameters such as the capture gamma contribution and the quality factor (QF) for chronic exposures and Relative Biological Effectiveness (RBE) for acute exposures have been calculated at various depths in an athropomorphic phantom. These calculations show that: (i) The LET distribution of dose is dependent upon the shape of the incident neutron spectrum. (ii) the contribution from intermediate energy neutrons to the total neutron dose increases with increasing neutron moderation and becomes a significant part of the total neutron dose from heavily moderated fission spectrum. (iii) the contribution from the capture gamma rays increases with the softening of the neutron spectrum and hence with the depth in the phantom. (iv) the QF and RBE as obtained for the surface element of the phantom are not strongly dependent upon the degree of moderation undergone by the incident fission spectrum. (v) the variation of QF with depth in the phantom is significant when one goes from a pure fission spectrum to a highly moderated incident fission spectrum. However the corresponding variation in RBE is not significant. Based on this analysis a quality factor value of 9 and an RBE of 2 for fission neutrons have been suggested for personnel doses received under chronic and acute exposure conditions respectively without any reference to the exact shape of the neutron spectrum.

Estimation of dose equivalent and average quality factors for pi- and pi+ beams.

A Monte Carlo computer program, used previously to compute absorbed dose as a function of position in a water phantom exposed to pion beams, is used to study dose equivalent and average quality factors. Detailed calculations for a typical beam (∼6 cm diameter, 175 MeV/c mean momentum) of negative pions show that the average quality factor is 1.6 to a depth of about 16 cm, after which it rises to a maximum of 6.4 at a depth of 22 cm, some 2 cm beyond the depth at which the absorbed dose is maximum. Similar calculations for positive pions show that the quality factor decreases with depth, because of the decreasing cross section for nuclear interactions. Adding muons and electrons to the pi− beam changes only slightly the relative contributions made by heavy fragments (atomic mass number > 1) and neutrons to the dose equivalent in the region where it is greatest. Average quality factors are also computed as a function of depth for pi− beams with mean momenta of 150 and 190 MeV/c. The maximum value of the average quality factor changes only slightly (from 5.5 to 7.0) over this momentum range.