High‐Quality Speech Compression ‐ Expansion Method

1962 ◽  
Vol 34 (5) ◽  
pp. 725-725 ◽  
Author(s):  
Oliver Johnson
Keyword(s):  
Expansion Method ◽  
Speech Compression ◽  
High Quality

A speech compression/expansion method based on subband filtering of the signal envelope

2003 ◽  
Vol 114 (4) ◽  
pp. 2360-2360
Author(s):  
Aslak Bjerkvik ◽  
Asbjorn Krokstad ◽  
Barbara Resch
Keyword(s):  
Expansion Method ◽  
Speech Compression ◽  
Signal Envelope

scholarly journals REVERSE TIME MIGRATION IN THE FREQUENCY DOMAIN BY THE RAPID EXPANSION METHOD

2017 ◽  
Vol 35 (4) ◽  
pp. 287
Author(s):  
Protásio Nery Andrade ◽  
Reynam Cruz Pestana ◽  
Daniel E. Revelo
Keyword(s):  
Frequency Domain ◽  
Expansion Method ◽  
Frequency Component ◽  
Rapid Expansion ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
High Quality ◽  
Depth Migration ◽  
Time Migration ◽  
Seismic Images

ABSTRACT.  This paper proposes and describes the implementation of a new depth migration method in the frequency domain. The method, based in the reverse time migration (RTM) technique, extrapolates wavefields from the source and receivers to obtain migrated seismic images that are built directly into the frequency domain. In the proposed method, wavefields are propagated in the time domain and are then transformed into the frequency domain at each time extrapolation step through the discrete Fourier transform. Neither the forward nor backward wavefield is needed to be stored in memory or read from disk storage. To speed up the migration algorithm, the discrete Fourier transform kernel for each frequency is computed and salved before the time extrapolation procedure. At the imaging condition phase, both source and receiver wavefields are at the same frequency, so that, the construction of the image occurs by multiplying the forward source propagated wavefield with the backward propagated of the receivers wavefield for each frequency component. Subsequently, saving the source field at each step to later correlate it with the backpropagated receiver wave field, usually done in conventional RTM, becomes unnecessary. Nor is it necessary to invert a matrix for each frequency component, which is done in the migration technique that uses the Helmholtz equation solution in the frequency domain. Thus, the migration procedure in the frequency domain being proposed is more efficient from a computational point of view, and can also produce high quality migrated images as those produced by conventional RTM. The rapid expansion method (REM) is used for seismic forward modeling, which extrapolated data with good precision and free of numerical dispersion. Thus, with the transformed data at each step in the frequency domain, it is possible to construct high quality, in-depth seismic images at a lower computational cost. Moreover, this frequency domain migration with REM is an atractive strategy to design robust inverse algorithms, especially for 3D problems. To demonstrate the efficiency and applicability of the proposed method, two synthetic models were used and their results showed high quality images equivalent to those obtained by conventional RTM and thus proving the vality of the method. Keywords: wave equation migration, depth migration, imaging condition, frequency domain migration. RESUMO. Um método de migração em profundidade no domínio da frequência é proposto e implementado. O método consiste na extrapolação dos campos de ondas da fonte e dos receptores e baseia-se na técnica de migração reversa no tempo (da sigla em inglês, RTM), obtendo imagens sísmicas migradas, construídas diretamente no domínio da frequência. No método que estamos propondo, os campos de ondas são propagados no domínio do tempo e a cada passo de extrapolação são transformados para o domínio da frequência, através da transformada de Fourier discreta (do inglês, on-the-fly transform). Para acelerar o algoritmo de migração, o kernel da transformada de Fourier é calculado fora do loop do tempo. Além disso, na etapa de condição da imagem, os campos de onda, tanto da fonte como dos receptores, são calculados no mesmo instante de tempo, ou seja, a construção da imagem se dá através da multiplicação do campo de onda da fonte com o campo retropropagado dos receptores, para cada componente de frequência. Portanto, não precisamos salvar o campo da fonte a cada passo no tempo para posteriormente correlacionar com o campo de onda retropropagado dos receptores, como é usualmente feito na RTM convencional, nem é preciso inverter uma matriz para cada componente de frequência, como é realizado normalmente pela técnica de migração no domínio da frequência, utilizando a solução da equação de Helmholtz. Desta forma, o procedimento de migração no domínio da frequência que estamos propondo se torna mais eficiente do ponto de vista computacional, podendo produzir imagens migradas de alta qualidade, quando comparadas às obtidas através da RTM convencional no domínio do tempo. Para a extrapolação dos campos de ondas no tempo foi empregado o método de expansão rápida (da sigla em inglês, REM), que permite a extrapolação dos dados com boa precisão e livres de dispersão numérica. Desta forma, com os dados transformados para o domínio da frequência, a cada passo no tempo, é possível a construção de imagens sísmicas em profundidade de boa qualidade e a um menor custo computacional. Para demonstrar a eficiência e aplicabilidade do método proposto, dois modelos sintéticos foram usados e seus resultados apresentaram imagens de alta qualidade equivalentes às obtidas pela RTM convencional. Palavras-chave: equação de migração da onda, migração, condição de imagem, migração no domínio da frequência.

Adaptive nonuniform polar quantization application to high quality speech compression

2009 ◽  
Vol 54 (12) ◽  
pp. 1384-1396 ◽  
Author(s):  
Z. Perić ◽  
A. Jovanović ◽  
O. Milanović ◽  
V. Manojlović ◽  
M. Dinčić
Keyword(s):  
Speech Compression ◽  
High Quality

Some problems of objective-prism spectra classification

1966 ◽  
Vol 24 ◽  
pp. 51-52
Author(s):  
E. K. Kharadze ◽  
R. A. Bartaya
Keyword(s):  
Short Wave ◽  
High Quality ◽  
Stellar Spectra ◽  
Objective Prism

The unique 70-cm meniscus-type telescope of the Abastumani Astrophysical Observatory supplied with two objective prisms and the seeing conditions characteristic at Mount Kanobili (Abastumani) permit us to obtain stellar spectra of a high quality. No additional design to improve the “climate” immediately around the telescope itself is being applied. The dispersions and photographic magnitude limits are 160 and 660Å/mm, and 12–13, respectively. The short-wave end of spectra reaches 3500–3400Å.

A non-cyanide method of electropolishing silver

1978 ◽  
Vol 36 (1) ◽  
pp. 146-147
Author(s):  
R. L. Lyles ◽  
S. J. Rothman ◽  
W. Jäger
Keyword(s):  
Electron Microscopy ◽  
Sulphuric Acid ◽  
Methyl Alcohol ◽  
Health Hazards ◽  
Silver Alloy ◽  
High Quality ◽  
Silver Alloys ◽  
Free Sample ◽  
Specimen Quality ◽  
Standard Techniques

Standard techniques of electropolishing silver and silver alloys for electron microscopy in most instances have relied on various CN recipes. These methods have been characteristically unsatisfactory due to difficulties in obtaining large electron transparent areas, reproducible results, adequate solution lifetimes, and contamination free sample surfaces. In addition, there are the inherent health hazards associated with the use of CN solutions. Various attempts to develop noncyanic methods of electropolishing specimens for electron microscopy have not been successful in that the specimen quality problems encountered with the CN solutions have also existed in the previously proposed non-cyanic methods.The technique we describe allows us to jet polish high quality silver and silver alloy microscope specimens with consistant reproducibility and without the use of CN salts.The solution is similar to that suggested by Myschoyaev et al. It consists, in order of mixing, 115ml glacial actic acid (CH3CO2H, specific wt 1.04 g/ml), 43ml sulphuric acid (H2SO4, specific wt. g/ml), 350 ml anhydrous methyl alcohol, and 77 g thiourea (NH2CSNH2).

A High Resolution Scanning Microscope

1968 ◽  
Vol 26 ◽  
pp. 356-357
Author(s):  
A. V. Crewe ◽  
J. Wall ◽  
L. M. Welter
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Spherical Aberration ◽  
Focal Length ◽  
Spot Size ◽  
Emission Source ◽  
Field Of View ◽  
Scanning Microscope ◽  
Magnetic Lens ◽  
High Quality

A scanning microscope using a field emission source has been described elsewhere. This microscope has now been improved by replacing the single magnetic lens with a high quality lens of the type described by Ruska. This lens has a focal length of 1 mm and a spherical aberration coefficient of 0.5 mm. The final spot size, and therefore the microscope resolution, is limited by the aberration of this lens to about 6 Å.The lens has been constructed very carefully, maintaining a tolerance of + 1 μ on all critical surfaces. The gun is prealigned on the lens to form a compact unit. The only mechanical adjustments are those which control the specimen and the tip positions. The microscope can be used in two modes. With the lens off and the gun focused on the specimen, the resolution is 250 Å over an undistorted field of view of 2 mm. With the lens on,the resolution is 20 Å or better over a field of view of 40 microns. The magnification can be accurately varied by attenuating the raster current.

Quantitative defect studies in semiconductor TEM samples prepared by low angle ion milling

1995 ◽  
Vol 53 ◽  
pp. 512-513
Author(s):  
L. Mulestagno ◽  
J.C. Holzer ◽  
P. Fraundorf
Keyword(s):  
Sample Preparation ◽  
Milling Time ◽  
High Density ◽  
Low Density ◽  
Ion Milling ◽  
High Quality ◽  
Variable Angle ◽  
Major Disadvantage ◽  
Induced Defects

Due to the wealth of information, both analytical and structural that can be obtained from it TEM always has been a favorite tool for the analysis of process-induced defects in semiconductor wafers. The only major disadvantage has always been, that the volume under study in the TEM is relatively small, making it difficult to locate low density defects, and sample preparation is a somewhat lengthy procedure. This problem has been somewhat alleviated by the availability of efficient low angle milling.Using a PIPS® variable angle ion -mill, manufactured by Gatan, we have been consistently obtaining planar specimens with a high quality thin area in excess of 5 × 104 μm2 in about half an hour (milling time), which has made it possible to locate defects at lower densities, or, for defects of relatively high density, obtain information which is statistically more significant (table 1).

Structural changes in silicon-on-insulator material during post-implantation annealing

1986 ◽  
Vol 44 ◽  
pp. 736-737
Author(s):  
C. O. Jung ◽  
S. J. Krause ◽  
S.R. Wilson
Keyword(s):  
Integrated Circuits ◽  
Oxide Layer ◽  
High Speed ◽  
Structural Changes ◽  
Device Fabrication ◽  
Silicon On Insulator ◽  
High Quality ◽  
Radiation Hardened ◽  
Post Implantation ◽  
Very High

Silicon-on-insulator (SOI) structures have excellent potential for future use in radiation hardened and high speed integrated circuits. For device fabrication in SOI material a high quality superficial Si layer above a buried oxide layer is required. Recently, Celler et al. reported that post-implantation annealing of oxygen implanted SOI at very high temperatures would eliminate virtually all defects and precipiates in the superficial Si layer. In this work we are reporting on the effect of three different post implantation annealing cycles on the structure of oxygen implanted SOI samples which were implanted under the same conditions.

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