Sound Absorbing Resonator Based on the Framed Nanofibrous Membrane

The sound absorbing means are based on a resonance membrane formed by a layer of polymeric nanofibers, which is restricted by a frame. The resonance membrane is then, upon impact of sound waves, brought into forced vibrations, whereby the kinetic energy of the membrane is converted into thermal energy by friction of individual nanofibers, by the friction of the membrane with ambient air and possibly with other layers of material arranged in its proximity. Moreover, part of the kinetic energy of the membrane is transmitted to the frame, to which the membrane is securely attached, and other part is converted into thermal energy due to increased friction in its inner structure, which is caused by the fact that the neighboring parts of the membrane, separated at least partially by the frame or its elements, may vibrate with mutually different periods and/or deviations. The frame is formed by a mesh of grid that can be regular in order to obtain uniform properties over the whole area of the sound absorbing material. The size and shape of the mesh affect the sound absorption or more precisely resonance behavior of the means. To obtain desired sound absorbing characteristics, the resonance membrane is connected to the frame with positive, zero, or negative tension

Resonance Effect of Nanofibrous Membrane for Sound Absorption Applications

Nanofibrous layers have unique acoustic properties due to the large specific surface area of the nanofibers, where viscous losses may occur and also the ability of the nanofiber layer to resonate at its own frequency. The resonance membrane is then, upon impact of sound waves of low frequency, brought into forced vibrations, whereby the kinetic energy of the membrane is converted into thermal energy by friction of individual nanofibers, by the friction of the membrane with ambient air, and possibly with other layers of material arranged in its proximity, and part of the energy is also transmitted to the frame, by which means the vibrations of the resonance membrane are damped. When sound waves hit the nanofiber membrane, they introduce forced vibrations in the case of resonance which have maximal amplitude. The principle of the technology is achieved by the synergy of perforated plate in the form of a cavity resonator with nanofibrous layer in the form of resonant membrane. The parameters of the resonant nanofibrous membrane together with the shape and volume of the perforations then determine which sound frequencies will be damped and to what extent

The inner mass distribution of late-type spiral galaxies from SAURON stellar kinematic maps

We infer the central mass distributions within 0.4-1.2 disc scale lengths of 18 late-type spiral galaxies using two different dynamical modelling approaches - the Asymmetric Drift Correction (ADC) and axisymmetric Jeans Anisotropic Multi-gaussian expansion (JAM) model. ADC adopts a thin disc assumption, whereas JAM does a full line-of-sight velocity integration. We use stellar kinematics maps obtained with the integral-field spectrograph SAURON to derive the corresponding circular velocity curves from the two models. To find their best-fit values, we apply Markov Chain Monte Carlo (MCMC) method. ADC and JAM modelling approaches are consistent within 5% uncertainty when the ordered motions are significant comparable to the random motions, i.e, $\overline{v_{\phi}}/\sigma_R$ is locally greater than 1.5. Below this value, the ratio $v_\mathrm{c,JAM}/v_\mathrm{c,ADC}$ gradually increases with decreasing $\overline{v_{\phi}}/\sigma_R$, reaching $v_\mathrm{c,JAM}\approx 2 \times v_\mathrm{c,ADC}$. Such conditions indicate that the stellar masses of the galaxies in our sample are not confined to their disk planes and likely have a non-negligible contribution from their bulges and thick disks.Comment: 44 pages, 60 figures, MNRAS accepted. The ADC-MCMC and JAM-MCMC python codes are available at: https://github.com/Kalinova/Dyn_models. The Multi-Gaussian Expansion (MGE) results are also available in the Appendi

Theoretical assessment of sound absorption coefficient for anisotropic nonwovens

The anisotropy factor as a function of fiber arrangement, fiber fineness and sample thickness has been derived from the theories of soundwave transformation due to phase changing. The sound absorption coefficient of the anisotropic fibrous material is then theoretically calculated. The fibrous materials were prepared so that the fibers are arranged parallel (perpendicularly laid fiber web called STRUTO technology) in the direction of soundwave propagation or perpendicularly (longitudinally laid fiber web) to the direction of sound propagation. The sound absorption coefficient was measured due to the Impedance tube. The theoretical results are in good agreement with experimental findings

Pěstování obilnin a pseudoobilnin v ekologickém zemědělství

V metodice je zpracována problematika pěstování obilnin a pseudoobilnin jako hlavních tržních plodin ekologického zemědělství v ČR. První část zahrnuje obecné zásady pěstování rostlin (obilnin a pseudoobilnin). Zpracovány jsou základní legislativní normy a dotační tituly. Dále je důraz kladen na volbu vhodných druhů a odrůd. Významná je část věnovaná výživě a hnojení, osevním postupům, regulaci škodlivých činitelů, ale také finalizaci celoroční práce farmáře a to sklizni a posklizňové úpravě bioprodukce. V části věnované pěstování konkrétních druhů je kladen důraz na pěstování pšenice seté (ozimé i jarní formy), opomíjeny ale nejsou ani další pluchaté pšenice jako je špalda, dvouzrnka nebo jednozrnka. Další druhy jsou reprezentovány ječmenem, tritikalem, žitem, ovsem a v neposlední řadě zástupcem skupiny pseudoobilnin - pohankou

Mass Distributions of Galaxies from SAURON and CALIFA Stellar Kinematic Maps

The amount and distribution of dark matter in galaxies defines the formation, evolution and dynamics of these systems. In this thesis we infer the internal mass distributions of 26 E–Sd galaxies using SAURON and CALIFA two-dimensional stellar kinematic maps. We compare two modeling approaches – fitting a solution of the axisymmetric Jeans equations and the commonly applied asymmetric drift correction (ADC). We show that ADC underestimates the enclosed mass by a factor of ∼3-4 once random motion (velocity dispersion) becomes significant com- pared to ordered motion (streaming), that is, when the ratio of ordered-over-random motion is less than about 1.5. Such kinematics indicate that the stellar mass of the galaxy is not confined to the disk plane, as happens in bulges and thick disks of spiral galaxies, as well as in elliptical galaxies. Since this is frequently realized in our sample, as well as in the general galaxy population, a full line-of-sight integration as provided by solutions of the axisymmetric Jeans equation is needed to reliably infer mass distributions in galaxies. We henceforth use the more realistic Jeans models to estimate the dark matter fraction (fDM), by modeling the total (dynamical) mass-to-light ratio and comparing it with the value derived for stars (baryons) from stellar population models. We find several trends of dark matter fraction with global galaxy properties. Ellipticals (E) and late-type spiral (Scd–Sd) galaxies are the most dark matter-dominated objects, while lenticular (S0) and early-type spirals (Sa–Sb) have significantly smaller dark matter fractions. On average, fDM increases both at highest and lowest galaxy (stellar) masses, and is smaller at intermediate masses. Further, it is also anticorrelated with the ratio of ordered-over-random motion, that is dispersion-dominated galaxies show a higher dark matter fraction. Finally, we investigate the maximum circular velocities and qualitative shape of rotation curves as a function of galaxy morphological type along the Hubble sequence. Peaked rotation curves are found in early-type galaxies, while slowly rising rotation curves are typical for late-type spirals. This confirms predictions of recent simulations of galaxy evolution with local photoionization feedback. More generally, our results for dark matter content and dynamics provide empirical constraints on current and future theoretical models of galaxy evolution across a wide range of galaxy morphological types and masses, and thereby will help us to understand the relevant physical processes

Pěstování rostlin v ekologickém zemědělství

Skripta předkládají problematiku pěstování hlavních plodin na orné půdě a trvalých travních porostů v systému ekologického zemědělství. Pěstování rostlin je rozděleno do skupin dle hospodářského významu (obilniny, pseudoobilniny, luskoviny, okopaniny, olejniny, pícniny a meziplodiny na orné půdě). U každé skupiny plodin student nalezne informace o významu pěstování plodiny a její vhodnosti pro ekologické zemědělství, hlavní agrotechnické zásady (osevní postup, výživa a hnojení, příprava pozemku, osivo a odrůdy, předpěstování sadby, regulace plevelů, ochrana rostlin, sklizeň a posklizňová úprava) a ekonomika pěstování