Iteration of transmit-beam aberration correction in medical ultrasound imaging
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Simulations of iterative transmit-beam aberration correction using a time-delay and amplitude filter have been performed to study the convergence of such a process. Aberration in medical ultrasonic imaging is usually modeled by arrival-time and amplitude fluctuations concentrated on the transducer array. This is an approximation of the physical aberration process, and may be applied to correct the transmitted signal using a time-delay and amplitude filter. Estimation of such a filter has proven difficult in the presence of severe aberration. Presented here is an iterative approach, whereby a filter estimate is applied to correct the transmit-beam. This beam induces acoustic backscatter better suited for arrival-time and amplitude estimation, thus facilitating an improved filter estimate. Two correlation-based methods for estimating arrival-time and amplitude fluctuations in received echoes from random scatterers were employed. Aberration was introduced using eight models emulating aberration produced by the human abdominal wall. Results show that only a few iterations are needed to obtain corrected transmit-beam profiles comparable to those of an ideal aberration correction filter. Furthermore, a previously developed focusing criterion is found to quantify the convergence accurately.Keywords:
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Experimental studies were made, with the following briefly stated results, on the discrimination of amplitude in case of whole body vibration.1) Δ a mm, the discriminated amplitudes from several amplitudes, in case of increased series existed in the range from 0.24 to 0.63 mm and in case of decreased series existed in the range from 0.17 to 0.73 mm.2) The higher the frequency of vibration, the smaller was the Δ a mm in case of transversal and longitudinal vibration.3) Δ a/a in case of the smallest amplitude was greatest than in case of the other amplitude.4) The discrimination in case of amplitude was weaker than in case of frequency.
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Most investigators emphasize the importance of detecting the reflected signal from the defect to determine if the pipe wall has any damage and to predict the damage location. However, often the small signal from the defect is hidden behind the other arriving wave modes and signal noise. To overcome the difficulties associated with the identification of the small defect signal in the time history plots, in this paper the time history is analyzed well after the arrival of the first defect signal, and after different wave modes have propagated multiple times through the pipe. It is shown that the defective pipe can be clearly identified by analyzing these late arriving diffuse ultrasonic signals. Multiple reflections and scattering of the propagating wave modes by the defect and pipe ends do not hamper the defect detection capability; on the contrary, it apparently stabilizes the signal and makes it easier to distinguish the defective pipe from the defect-free pipe. This paper also highlights difficulties associated with the interpretation of the recorded time histories due to mode conversion by the defect. The design of electro-magnetic acoustic transducers used to generate and receive the guided waves in the pipe is briefly described in the paper.
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Electromagnetic acoustic transducer
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Amplitudes are presented which fit extensive spin-dependent data from 450 to 800 MeV. The energy dependence of 3P2, 1D2 and 3F3 amplitudes agrees in both magnitude and phase with pi d to Delta N, with the nucleon playing the role of a spectator; the phases are close to delta NN+ delta pi d, the sum of elastic phase-shifts for NN and pi d scattering. The 3P1 amplitude is the sum of a repulsive threshold contribution and an attractive contribution due to the formation of an intermediate Delta . Data from 578 to 800 MeV give reliable determinations of the 1S0 amplitude and a rough determination of the 3F2 amplitude.
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The nonlinear optoelectronic (NLOE) filter represents a novel class of filters whose filtering operation is based a signal reaching a specific amplitude rather than falling within a specific range of frequencies. This amplitude filtering aspect carries with it a stringent amplitude stability requirement where the input signal must be precisely maintained at a specific level for the signal to be rejected. In many real-world settings, the signal amplitudes are not precisely known or held constant over long periods of time, which greatly inhibits the application of this filter outside the laboratory. We report here a novel amplitude-stabilization scheme that locks the signal amplitude (<; 0.004 dB) to the precise level required for filter operation. Using this stabilization technique, we demonstrate a record NLOE filter suppression of 71 dB for a 3.1 GHz interferer signal relative to a second RF signal located at an 8-kHz offset. We also show the ability to maintain a >50 dB level of suppression over a period of one hour or more.
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Amplitude distortion
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Different time gain and amplitude-color arranging for ground penetrating radar data: Applied samples
We introduced a simple time gain approximation with a functioned amplitude-color range to image all amplitudes or only selected amplitudes. First, we reduced ground wave amplitudes near to the maximum reflected / diffracted wave amplitudes of the data. Thus amplitude range of the two dimensional (2D) GPR profile section (radargram) was rescaled by maximum reflected/ diffracted wave amplitude values only for displaying the radargram. Second, we rearranged amplitude-color range with a functional approximation which was very important as well as time gain application to pick events according to the aim of the research. Third, we functioned an opaque range to obtain transparent three dimensional (3D) image of the aligned 2D radargrams. We presented 2D and 3D applications to show our approximations.
Ground-Penetrating Radar
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Dispersion relation
Formalism (music)
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Бұл зерттеужұмысындaКaно моделітурaлы жәнеоғaн қaтыстытолықмәліметберілгенжәнеуниверситетстуденттерінебaғыттaлғaн қолдaнбaлы (кейстік)зерттеужүргізілген.АхметЯссaуи университетініңстуденттеріүшін Кaно моделіқолдaнылғaн, олaрдың жоғaры білімберусaпaсынa қоятынмaңыздытaлaптaры, яғнисaпaлық қaжеттіліктері,олaрдың мaңыздылығытурaлы жәнесaпaлық қaжеттіліктерінеқaтыстыөз университетінқaлaй бaғaлaйтындығытурaлы сұрaқтaр қойылғaн. Осы зерттеудіңмaқсaты АхметЯсaуи университетіндетуризмменеджментіжәнеқaржы бaкaлaвриaт бaғдaрлaмaлaрыныңсaпaсынa қaтыстыстуденттердіңқaжеттіліктерінaнықтaу, студенттердіңқaнaғaттaну, қaнaғaттaнбaу дәрежелерінбелгілеу,білімберусaпaсын aнықтaу мен жетілдіружолдaрын тaлдaу болыптaбылaды. Осы мaқсaтқaжетуүшін, ең aлдыменКaно сaуaлнaмaсы түзіліп,116 студенткеқолдaнылдыжәнебілімберугежәнеоның сaпaсынa қaтыстыстуденттердіңтaлaптaры мен қaжеттіліктерітоптықжұмыстaрaрқылыaнықтaлды. Екіншіден,бұл aнықтaлғaн тaлaптaр мен қaжеттіліктерКaно бaғaлaу кестесіменжіктелді.Осылaйшa, сaпa тaлaптaры төрт сaнaтқa бөлінді:болуытиіс, бір өлшемді,тaртымдыжәнебейтaрaп.Соңындa,қaнaғaттaну мен қaнaғaттaнбaудың мәндеріесептелдіжәнестуденттердіңқaнaғaттaну мен қaнaғaттaнбaу деңгейлерінжоғaрылaту мен төмендетудеосытaлaптaр мен қaжеттіліктердіңрөліaйқын aнықтaлды.Түйінсөздер:сaпa, сaпaлық қaжеттіліктер,білімберусaпaсы, Кaно моделі.
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Small oscillating amplitudes (~0. 1°) and larger (> 1°) can both lead to wear, which complicates the evaluation of the operating conditions. In this work, a simulation model is used to discuss critical amplitudes. The parametric study, which includes 125 simulations, shows the effect of load and coefficient of friction on the frictional work density for amplitudes ranging from 0.1 to 2.5°. The study concludes that the frictional work density increases with the oscillating amplitude up to a certain point, where it becomes almost constant in relation to the amplitude. This point is reached when the amplitude is so large that a continuous overlapping of the contact zone no longer occurs. It is precisely this point that marks the critical oscillation amplitude.
Oscillation (cell signaling)
Critical point (mathematics)
Constant (computer programming)
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