An Enhanced Multi-frequency Distorted Born Iterative Method for Ultrasound Tomography based on Fundamental Tone and Overtones

Conventional Distorted Born Iterative Method (DBIM) using single frequency has low resolution and is prone to creating images with high-contrast subjects. We propose a productive frequency combination method to better result in tomographic ultrasound imaging based on the multi-frequency technique. This study uses the natural mechanism of emitting oscillators' frequencies and uses these frequencies for imaging in iterations. We use a fundamental tone (i.e., the starting frequency f0) for the first iteration in DBIM, then consecutively use its overtones for the next ones. The digital simulation scenarios are tested with other multi-frequency approaches to prove our method's feasibility. We performed 57 different simulation scenarios on the use of multi-frequency information for the DBIM method. As a result, the proposed method for the smallest normalization error (RRE = 0.757). The proposed method's imaging time is not significantly longer than the way of using single frequency information.

Fundamental Tone and Overtones of Quasinormal Modes in Ringdown Gravitational Waves: A Detailed Study in Black Hole Perturbation

Ringdown gravitational waves of compact object binaries observed by ground-based gravitational-wave detectors encapsulate rich information to understand remnant objects after the merger and to test general relativity in the strong field. In this work, we investigate the ringdown gravitational waves in detail to better understand their property, assuming that the remnant objects are black holes. For this purpose, we perform numerical simulations of post-merger phase of binary black holes by using the black hole perturbation scheme with the initial data given under the close-limit approximation, and we generate data of ringdown gravitational waves with smaller numerical errors than that associated with currently available numerical relativity simulations. Based on the analysis of the data, we propose an orthonormalization of the quasinormal mode functions describing the fundamental tone and overtones to model ringdown gravitational waves. Finally, through some demonstrations of the proposed model, we briefly discuss the prospects for ringdown gravitational-wave data analysis including the overtones of quasinormal modes.

“ROLE OF ULTRASOUND IN VOCAL CORD PALSY”

Phonation is beyond doubt one of the highest functions of the human larynx. The vocal cords, also known as vocal cords, as the name suggests are infolding of mucosa aligned horizontally. The phonatory process, or voicing, occurs when air is expelled from the lungs through the glottis, creating a pressure drop across the larynx. When this drop becomes sufciently large, the vocal cords start to oscillate. The motion of the vocal cords during oscillation is mostly lateral, though there is also some superior component as well. However, there is almost no motion along the length of the vocal cords. The oscillation of the vocal cords serves to modulate the pressure and ow of the air through the larynx, and this modulated airow is the main component of the sound. The sound that the larynx produces is a harmonic series. In other words, it consists of a fundamental tone (called the fundamental frequency, the main acoustic cue for the percept pitch) accompanied by harmonic overtones, which are multiples of the (1) fundamental frequency .

Intonation of the Altai language (simple one-component imperative utterances)

The paper presents the results of studying the Altai language intonation on the experimental material recorded from six speakers fluent in the Altai language from different regions of the Altai Republic. The recording program consisted of situational single-component imperative utterances. Twenty sentences were pronounced three times each in positive and negative versions, in singular and plural, having different degrees of imperativeness, but without any expressive emotional load. The single-compound motivational statements considered are expressed by imperative or desirable verb forms in the first-, second-, and third-person singular and plural in the affirmative and negative variants. The experimental phonetic study has revealed rising tone to be characteristic for positive and negative imperative one-component sentences, with fundamental tone frequency peaks at the last syllable and there being a possibility for intensity, presumably marking the stressed syllable, to shift within a word-form. The analysis showed the intonation marking of motivational statements to depend on their type: action stimulation, order or demand, are characterized by inclination, a request - by a combined ascending-descending tone, a ban - by a descending tone, advice - both by ascending-descending intonation and declination. In the negative version, in singular and plural, in three or more syllabic sentences on the negative particles -ba / -be, -pa / -pe, etc., there is an even tone or a decrease in the frequency of the fundamental tone. The peak of intensity in such sentences is realized on the last syllable of the verb. In addition, the vowel of the final syllable is usually prolonged.

Генерация когерентного рентгеновского излучения гармоник в однопроходном лазере на свободных электронах со сдвигом фаз электронов относительно фотонов

Theoretical study of the radiated FEL power and bunching is conducted in single-pass free electron laser (FEL) with repetitive shift of the photon pulse with respect to the electron bunch in between the sections of the undulator with field harmonics. Using the analytical calculations, the asymmetric elliptic and planar undulator fields are identified for the undulators to be able to reduce the fundamental tone and enhance the harmonic radiation. This effect is amplified by the phase shift kπ/n, k=2,4,6… of the electrons and photons between the undulator sections. This allows n-th FEL harmonic reach its peak power beyond the fundamental saturation FEL length. It is not possible to achieve in a common FEL due to fast increase of the energy spread, induced by the fundamental tone along FEL and its early saturation. The phenomenological model of the FEL is used for the analysis of the bunching coefficients and harmonic powers evolution in the FEL. The model describes the debunching between the undulator sections, where the phase shift is imposed, and accounts for the higher sensitivity to losses of the electron-photon interaction at high harmonic wavelengths. The losses are due to the beam energy spread and emittance, deviation off the axis, diffraction etc. Explicit expressions for the Bessel coefficients of the planar and elliptic undulators with field harmonics are obtained and analyzed. The combination of the undulator field harmonics is identified, which reduces the fundamental tone and enhances the 3rd and 5th UR harmonics as compared with the radiation from a planar undulator. We propose the use of these undulators in a FEL with the electron-photon phase shift, which increases high harmonic powers in X-ray band by ~100 times with respect to common FELs.

“Nichts als der Tod und die Satire”

Grimmelshausen’s Simplicius Simplicissimus, the classic novel of the Thirty Years War, is a unique critique in an exuberant narrative form. The double perspective (the hero narrates, as an old man, his own life), the doubt as a principle, irony as the fundamental tone – these are his main strategies to analyse the ambivalence of human behaviour as well as to check critically social models of a more peaceful society. Grimmelshausen refuses any philosophical, political or theological justification of violence. However, his irony, his humour and his narrative power make the lecture of his work a pleasure until today. The comparison with a modern African novel, Ahmadou Kouroumas Allah Is Not Obliged, reveals similarities as well as differences and proves one more time the topicality and constant relevance of this Baroque novel.

Method for determining the rational parameters of dynamic dampers of low-frequency vibrations

The problems have been considered of natural nonlinear vibrations of an absolutely rigid semiball and a semicylinder on a horizontal plane, assuming that there is no energy dissipation, sliding and tipping on foundation. To adjust the damper to a frequency close to the fundamental tone of vibrations, it is necessary to assess the natural frequency of the damper, which is determined under the assumption on smallness of the vibrations amplitude. This paper represents the comparison of the natural frequency of linearized and nonlinear system. The relative error has been estimated of the natural frequency calculation, which is caused by linearization. It is shown that the ratio of the natural frequency of the linearized system to the natural frequency of the nonlinear system does not depend on the mass and radius. This conclusion made it possible to generalize the results of particular computational solutions and to obtain a formula which takes into account the amplitude influence on the natural vibrations frequency and helps to determine the natural frequency for the initial angles to ninety degrees.