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1
Alekseev, Yu I., and I. V. Maliev. "High-Q microwave chamber providing Gunn diodes operation in the oscillation and amplification modes." Instruments and Experimental Techniques 49, no. 3 (May 2006): 391–94. http://dx.doi.org/10.1134/s0020441206030158.
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Platz, Daniel, Daniel Forchheimer, Erik A. Tholén, and David B. Haviland. "Interpreting motion and force for narrow-band intermodulation atomic force microscopy." Beilstein Journal of Nanotechnology 4 (January 21, 2013): 45–56. http://dx.doi.org/10.3762/bjnano.4.5.
Повний текст джерелаАнотація:
Intermodulation atomic force microscopy (ImAFM) is a mode of dynamic atomic force microscopy that probes the nonlinear tip–surface force by measurement of the mixing of multiple modes in a frequency comb. A high-quality factor cantilever resonance and a suitable drive comb will result in tip motion described by a narrow-band frequency comb. We show, by a separation of time scales, that such motion is equivalent to rapid oscillations at the cantilever resonance with a slow amplitude and phase or frequency modulation. With this time-domain perspective, we analyze single oscillation cycles in ImAFM to extract the Fourier components of the tip–surface force that are in-phase with the tip motion (F I ) and quadrature to the motion (F Q ). Traditionally, these force components have been considered as a function of the static-probe height only. Here we show that F I and F Q actually depend on both static-probe height and oscillation amplitude. We demonstrate on simulated data how to reconstruct the amplitude dependence of F I and F Q from a single ImAFM measurement. Furthermore, we introduce ImAFM approach measurements with which we reconstruct the full amplitude and probe-height dependence of the force components F I and F Q , providing deeper insight into the tip–surface interaction. We demonstrate the capabilities of ImAFM approach measurements on a polystyrene polymer surface.
3
Yoshiki, Wataru, Akitoshi Chen-Jinnai, Tomohiro Tetsumoto, and Takasumi Tanabe. "Observation of energy oscillation between strongly-coupled counter-propagating ultra-high Q whispering gallery modes." Optics Express 23, no. 24 (November 17, 2015): 30851. http://dx.doi.org/10.1364/oe.23.030851.
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Pinçon, C., M. J. Goupil, and K. Belkacem. "Probing the mid-layer structure of red giants." Astronomy & Astrophysics 634 (February 2020): A68. http://dx.doi.org/10.1051/0004-6361/201936864.
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Context. The space-borne missions CoRoT and Kepler have already brought stringent constraints on the internal structure of low-mass evolved stars, a large part of which results from the detection of mixed modes. However, all the potential of these oscillation modes as a diagnosis of the stellar interior has not been fully exploited yet. In particular, the coupling factor or the gravity-offset of mixed modes, q and εg, are expected to provide additional constraints on the mid-layers of red giants, which are located between the hydrogen-burning shell and the neighborhood of the base of the convective zone. The link between these parameters and the properties of this region, nevertheless, still remains to be precisely established. Aims. In the present paper, we investigate the potential of the coupling factor in probing the mid-layer structure of evolved stars. Methods. Guided by typical stellar models and general physical considerations, we modeled the coupling region along with evolution. We subsequently obtained an analytical expression of q based on the asymptotic theory of mixed modes and compared it to observations. Results. We show that the value of q is degenerate with respect to the thickness of the coupling evanescent region and the local density scale height. On the subgiant branch and the beginning of the red giant branch (RGB), the model predicts that the peak in the observed value of q is necessarily associated with the important shrinking and the subsequent thickening of the coupling region, which is located in the radiative zone at these stages. The large spread in the measurement is interpreted as the result of the high sensitivity of q to the structure properties when the coupling region becomes very thin. Nevertheless, the important degeneracy of q in this regime prevents us from unambiguously concluding on the precise structural origin of the observed values. In later stages, the progressive migration of the coupling region toward the convective zone is expected to result in a slight and smooth decrease in q, which is in agreement with observations. At one point just before the end of the first-dredge up and the luminosity bump, the coupling region becomes entirely located in the convective region and its continuous thickening is shown to be responsible for the observed decrease in q. We demonstrate that q has the promising potential to probe the migration of the base of the convective region as well as convective extra-mixing during this stage. We also show that the frequency-dependence of q cannot be neglected in the oscillation spectra of such evolved RGB stars, which is in contrast with what is assumed in the current measurement methods. This fact can have an influence on the physical interpretation of the observed values. In red clump stars, in which the coupling regions are very thin and located in the radiative zone, the small variations and spread observed in q suggest that their mid-layer structure is very stable. Conclusions. A structural interpretation of the global observed variations in q was obtained and the potential of this parameter in probing the dynamics of the mid-layer properties of red giants is highlighted. This analytical study paves the way for a more quantitative exploration of the link of q with the internal properties of evolved stars using stellar models for a proper interpretation of the observations. This will be undertaken in the following papers of this series.
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Clementi, Marco, Andrea Barone, Thomas Fromherz, Dario Gerace, and Matteo Galli. "Selective tuning of optical modes in a silicon comb-like photonic crystal cavity." Nanophotonics 9, no. 1 (November 19, 2019): 205–10. http://dx.doi.org/10.1515/nanoph-2019-0395.
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AbstractRealizing multiply resonant photonic crystal cavities with large free spectral range is key to achieve integrated devices with highly efficient nonlinear response, such as frequency conversion, four-wave mixing, and parametric oscillation. This task is typically difficult owing to the cavity modes’ sensitivity to fabrication disorder, which makes it hard to reliably achieve a comb-like spectrum of equally spaced modes even when a perfect matching is theoretically predicted. Here we show that a comb-like spectrum of up to eight modes with very high quality factor and diffraction limited volumes can be engineered in the bichromatic-type potential of a two-dimensional photonic crystal cavity fabricated in a thin silicon membrane. To cope with the tight tolerance in terms of frequency spacings and resonance linewidths, we develop a permanent post-processing technique that allows the selective tuning of individual confined modes, thus achieving an almost perfect frequency matching of high Q resonances with record finesse in silicon microresonators. Our experimental results are extremely promising in view of ultra-low power nonlinear photonics in silicon.
6
Li, Haohua, Xiaobo Wang, Tian Yang, and Ji Zhou. "A Mechanical Sensor Using Hybridized Metamolecules." Materials 12, no. 3 (February 3, 2019): 466. http://dx.doi.org/10.3390/ma12030466.
Повний текст джерелаАнотація:
Hybridized metamaterials with collective mode resonance are usually applied as sensors. In this paper, we make use of one Mie-based hybridized metamolecule comprising of dielectric meta-atoms and an elastic bonding layer in order to detect the distances and applied forces. The hybridization induced splitting results in two new collective resonance modes, of which the red-shifted mode behaves as the in-phase oscillation of two meta-atoms. Owing to the synergy of the oscillation, the in-phase resonance appears as a deep dip with a relatively high Q-factor and figure of merit (FoM). By exerting an external force, namely by adjusting the thickness of the bonding layer, the coupling strength of the metamolecule is changed. As the coupling strength increases, the first collective mode dip red-shifts increasingly toward lower frequencies. By fitting the relationship of the distance–frequency shift and the force–frequency shift, the metamolecule can be used as a sensor to characterize tiny displacement and a relatively wide range of applied force in civil engineering and biological engineering.
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SIMÃO, ANDRÉ G., and LUIZ G. GUIMARÃES. "Tunneling effects in resonant acoustic scattering of an air bubble in unbounded water." Anais da Academia Brasileira de Ciências 88, no. 2 (June 2016): 765–90. http://dx.doi.org/10.1590/0001-3765201620150403.
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Abstract The problem of acoustic scattering of a gaseous spherical bubble immersed within unbounded liquid surrounding is considered in this work. The theory of partial wave expansion related to this problem is revisited. A physical model based on the analogy between acoustic scattering and potential scattering in quantum mechanics is proposed to describe and interpret the acoustical natural oscillation modes of the bubble, namely, the resonances. In this context, a physical model is devised in order to describe the air water interface and the implications of the high density contrast on the various regimes of the scattering resonances. The main results are presented in terms of resonance lifetime periods and quality factors. The explicit numerical calculations are undertaken through an asymptotic analysis considering typical bubble dimensions and underwater sound wavelengths. It is shown that the resonance periods are scaled according to the Minnaert’s period, which is the short lived resonance mode, called breathing mode of the bubble. As expected, resonances with longer lifetimes lead to impressive cavity quality Q-factor ranging from 1010 to 105. The present theoretical findings lead to a better understanding of the energy storage mechanism in a bubbly medium.
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Ziping Zhang, Ziping Zhang, Yitang Dai Yitang Dai, Feifei Yin Feifei Yin, Pan Ou Pan Ou, Yue Zhou Yue Zhou, Jianqiang Li Jianqiang Li, and and Kun Xu and Kun Xu. "Single-longitudinal-mode, narrow-linewidth oscillation from a high-Q photonic-electronic hybrid cavity." Chinese Optics Letters 15, no. 1 (2017): 010010–10014. http://dx.doi.org/10.3788/col201715.010010.
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Mondal, Sirshendu, Samadhan A. Pawar, and R. I. Sujith. "Forced synchronization and asynchronous quenching of periodic oscillations in a thermoacoustic system." Journal of Fluid Mechanics 864 (February 1, 2019): 73–96. http://dx.doi.org/10.1017/jfm.2018.1011.
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We perform an experimental and theoretical study to investigate the interaction between an external harmonic excitation and a self-excited oscillatory mode ($f_{n0}$) of a prototypical thermoacoustic system, a horizontal Rijke tube. Such an interaction can lead to forced synchronization through the routes of phase locking or suppression. We characterize the transition in the synchronization behaviour of the forcing and the response signals of the acoustic pressure while the forcing parameters, i.e. amplitude ($A_{f}$) and frequency ($f_{f}$) of forcing are independently varied. Further, suppression is categorized into synchronous quenching and asynchronous quenching depending upon the value of frequency detuning ($|\,f_{n0}-f_{f}|$). When the applied forcing frequency is close to the natural frequency of the system, the suppression in the amplitude of the self-excited oscillation is known as synchronous quenching. However, this suppression is associated with resonant amplification of the forcing signal, leading to an overall increase in the response amplitude of oscillations. On the other hand, an almost 80 % reduction in the root mean square value of the response oscillation is observed when the system is forced for a sufficiently large value of the frequency detuning (only for $f_{f}<f_{n0}$). Such a reduction in amplitude occurs due to asynchronous quenching where resonant amplification of the forcing signal does not occur, as the frequency detuning is significantly high. Further, the results from a reduced-order model developed for a horizontal Rijke tube show a qualitative agreement with the dynamics observed in experiments. The relative phase between the acoustic pressure ($p^{\prime }$) and the heat release rate ($\dot{q}^{\prime }$) oscillations in the model explains the occurrence of maximum reduction in the pressure amplitude due to asynchronous quenching. Such a reduction occurs when the positive coupling between $p^{\prime }$ and $\dot{q}^{\prime }$ is disrupted and their interaction results in overall acoustic damping, although both of them oscillate at the forcing frequency. Our study on the phenomenon of asynchronous quenching thus presents new possibilities to suppress self-sustained oscillations in fluid systems in general.
10
Liu, Xiao, J. F. Vignola, S. F. Morse, D. M. Photiadis, A. Sarkissian, M. H. Marcus, and B. H. Houston. "The modes and loss mechanisms of a high Q mechanical oscillator." Journal of the Acoustical Society of America 108, no. 5 (November 2000): 2623. http://dx.doi.org/10.1121/1.4743765.
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Liu, Xiao, S. F. Morse, J. F. Vignola, D. M. Photiadis, A. Sarkissian, M. H. Marcus, and B. H. Houston. "On the modes and loss mechanisms of a high Q mechanical oscillator." Applied Physics Letters 78, no. 10 (March 5, 2001): 1346–48. http://dx.doi.org/10.1063/1.1350599.
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Milic, Miljana, and Vanco Litovski. "Oscillation-based testing method for detecting switch faults in High-Q SC biquad filters." Facta universitatis - series: Electronics and Energetics 28, no. 2 (2015): 223–36. http://dx.doi.org/10.2298/fuee1502223m.
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Testing switched capacitor circuits is a challenge due to the diversity of the possible faults. A special problem encountered is the synthesis of the test signal that will control and make the fault-effect observable at the test point. The oscillation based method which was adopted for testing in these proceedings resolves that important issue in its nature. Here we discuss the properties of the method and the conditions to be fulfilled in order to implement it in the right way. To achieve that, we have resolved the problem of synthesis of the positive feed-back circuit and the choice of a proper model of the operational amplifier. In that way, a realistic foundation to the testing process was generated. A second order notch cell was chosen as a case-study. Fault dictionaries were developed related to the catastrophic faults of the switches used within the cell. The results reported here are a continuation of our previous work and are complimentary to some other already published.
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Zadorin, A. S., and A. A. Lukina. "A RESONANCE SYSTEM OF AN OPTOELECTRONIC OSCILLATOR BASED ON A TRANSMISSIONTYPE PLANAR OPTICAL DISK MICROCAVITY." Computer Optics 42, no. 1 (March 30, 2018): 60–66. http://dx.doi.org/10.18287/2412-6179-2018-42-1-60-66.
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It is noted that the best technical characteristics of optoelectronic microwave self-oscillators (OESO) are reached in schemes employing high-Q optical microresonators (OMR) working in the traveling wave modes (TWM). A possibility of using disk OMRs excited by fundamental whispering gallery modes (WGM) has been considered. Multielement coupling devices (CD) for such resonators have been investigated. They are constructed on the basis of planar optical waveguides (POWG) located over the disk resonator surface in a region bounded by the outer and inner caustics of the WGM. Models of this device have been proposed. The corresponding calculations have been provided.
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Kocharovskaya, Ekaterina, Alexey Mishin, and Ivan Ryabinin. "Features of mode selection in a combined Fabry-Perot cavity with distributed feedback of counter-propagating waves." ITM Web of Conferences 30 (2019): 08009. http://dx.doi.org/10.1051/itmconf/20193008009.
Повний текст джерелаАнотація:
An analysis is made of the possibility of isolating relatively high-Q modes or groups of such modes in low-Q combined Fabry-Perot cavities with distributed feedback of counter-propagating waves in order to ensure resonant interaction of the electromagnetic field with the polarization oscillations of an amplifying or absorbing medium filling the cavity. We considered two-level active media with homogeneous or inhomogeneous broadening of a spectral line, which can be both smaller or larger than the photon bandgap of a cavity. Particular attention is paid to the change in the well-known spectrum of polariton modes which takes place due to the transition from an absorbing to an amplifying medium under conditions that allow the realization of spontaneous or laser generation of the so-called superradiant modes.
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Zhao, Peng, Rongxun Piao, and Zongshu Zou. "Mesoscopic Fluid-Particle Flow and Vortex Structural Transmission in a Submerged Entry Nozzle of Continuous Caster." Materials 15, no. 7 (March 29, 2022): 2510. http://dx.doi.org/10.3390/ma15072510.
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Understanding the essence of the flow oscillations within a submerged-entry nozzle (SEN) is essential to control flow patterns in the continuous casting mold and consequently increase the superficial quality of steel products. A numerical study of the mesoscopic fluid-particle flow in a bifurcated pool-type SEN under steady operating conditions is conducted using the lattice Boltzmann method (LBM) coupled with the large eddy simulation (LES) model. The accuracy of the model has been verified by comparing vortex structures and simulated velocities with published experimental values. The LBM modeling is also verified by comparing the “stair-step” jet patterns observed in the experiment. The geometrical parameters and operational conditions of physical experiments are reproduced in the simulations. By comparing the time-averaged velocities of Reynolds-averaged Navier–Stokes equations (RANS) with LBM models, transient mesoscopic fluid-particles and related vortex structures can be better reproduced within the SEN. The visualization of internal flow within the SEN is illustrated through the mass-less Discrete Phase Model (DPM) model. The trajectories show that the LBM–LES–DPM coupled model is good at predicting the transient vortical flow within the SEN. A large vortex is found inside the exit port and continuously changes in shape and size therein. The monitoring points and lines within the SEN are selected to illustrate the velocity variations and effective viscosity, which can reflect the oscillating characteristics even under stable operating conditions without changes at the exit from the SEN. Furthermore, the formation, development, diffusion, and dissipation of the vortex structures from the exit port of the SEN are also investigated using the Q criteria. The comparison of the power spectrum with high-frequency components along the exit port indicates that the flow oscillations must originate from within the SEN and are intensified in the exit port. The mesoscopic LBM model can replicate the fluid-particle flow and vortex structure transmission as well as their turbulence effects inside the SEN in detail.
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LEELAMMA, K. K., V. C. KURIAKOSE, and K. BABU JOSEPH. "LATTICE HEAT CAPACITY OF CRYSTALS: A q-OSCILLATOR DEBYE MODEL." International Journal of Modern Physics B 07, no. 14 (June 30, 1993): 2697–706. http://dx.doi.org/10.1142/s0217979293003000.
Повний текст джерелаАнотація:
The Debye model for lattice heat capacity is modified retaining all the basic assumptions except that each mode is here treated as a q-deformed quantum harmonic oscillator. The lattice heat capacity Cv is evaluated in the high and low temperature limits. When T≪θD, Cv∝T3 and when T ≫θD, Cv∝T2. In the case of the alkali elements Rb, Cs and K whose Debye temperatures are relatively low, the calculated values compare remarkably well with experimental results over a wide range of temperatures.
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Mukhin, Sergei. "Euclidean Q-Balls of Fluctuating SDW/CDW in the ‘Nested’ Hubbard Model of High-Tc Superconductors as the Origin of Pseudogap and Superconducting Behaviors." Condensed Matter 7, no. 2 (March 31, 2022): 31. http://dx.doi.org/10.3390/condmat7020031.
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The origin of the pseudogap and superconducting behaviors in high-Tc superconductors is proposed, based on the picture of Euclidean Q-balls formation that carry Cooper/local-pair condensates inside their volumes. Euclidean Q-balls that describe bubbles of collective spin-/charge density fluctuations (SDW/CDW) oscillating in Matsubara time are found as a new self-consistent solution of the Eliashberg equations in the ‘nested’ repulsive Hubbard model of high-Tc superconductors. The Q-balls arise due to global invariance of the effective theory under the phase rotation of the Fourier amplitudes of SDW/CDW fluctuations, leading to conservation of the ‘Noether charge’ Q in Matsubara time. Due to self-consistently arising local minimum of their potential energy at finite amplitude of the density fluctuations, the Q-balls provide greater binding energy of fermions into local/Cooper pairs relative to the usual Frohlich mechanism of exchange with infinitesimal lattice/charge/spin quasiparticles. We show that around some temperature T* the Q-balls arise with a finite density of superconducting condensate inside them. The Q-balls expand their sizes to infinity at superconducting transition temperature Tc. The fermionic spectral gap inside the Q-balls arises in the vicinity of the ‘nested’ regions of the bare Fermi surface. Solutions are found analytically from the Eliashberg equations with the ‘nesting’ wave vectors connecting ‘hot spots’ in the Brillouin zone. The experimental ‘Uemura plot’ of the linear dependence of Tc on superconducting density ns in high-Tc superconducting compounds follows naturally from the proposed theory.
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Nassiri, Ali, Hafida Idrissi-Saba, and Abdelkader Boulezhar. "Analysis and Design of Coherent Combining of two Q-Switched Fiber Laser in Mach-Zehnder Type Cavity." Journal of Optical Communications 40, no. 4 (October 25, 2019): 393–400. http://dx.doi.org/10.1515/joc-2017-0110.
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Abstract In this work, we have developed an analytical model of an actively Q-switched Ytterbium-doped fiber laser by using two coupled cavities with amplifying fibers in Mach–Zehnder interferometer configuration. This oscillator system provides high peak power and high energy nanosecond pulse. The pulse energy is almost twice the energy of an individual fiber laser with a combining efficiency goes up 99%. This concept brings some novel perspectives for scaling the high energy and high peak power of nanosecond pulse fiber laser.
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van der Slot, Peter J. M., and Henry P. Freund. "Three-Dimensional, Time-Dependent Analysis of High- and Low-Q Free-Electron Laser Oscillators." Applied Sciences 11, no. 11 (May 28, 2021): 4978. http://dx.doi.org/10.3390/app11114978.
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Free-electron lasers (FELs) have been designed to operate over virtually the entire electromagnetic spectrum, from microwaves through to X-rays, and in a variety of configurations, including amplifiers and oscillators. Oscillators can operate in both the low and high gain regime and are typically used to improve the spatial and temporal coherence of the light generated. We will discuss various FEL oscillators, ranging from systems with high-quality resonators combined with low-gain undulators, to systems with a low-quality resonator combined with a high-gain undulator line. The FEL gain code MINERVA and wavefront propagation code OPC are used to model the FEL interaction within the undulator and the propagation in the remainder of the oscillator, respectively. We will not only include experimental data for the various systems for comparison when available, but also present, for selected cases, how the two codes can be used to study the effect of mirror aberrations and thermal mirror deformation on FEL performance.
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Kocharovskaya, E. R., A. V. Mishin, I. S. Ryabinin, and V. V. Kocharovsky. "Features of the Simultaneous Generation of Low-Q and High-Q Modes in Heterolasers Based on Quantum Dots with a Long Incoherent Relaxation Time of Optical Dipole Oscillations." Semiconductors 53, no. 10 (October 2019): 1295–303. http://dx.doi.org/10.1134/s1063782619100099.
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Chen, Gang, Laurentiu S. Popa, Xinming Wang, Wangcai Gao, Justin Barnes, Claudia M. Hendrix, Ellen J. Hess, and Timothy J. Ebner. "Low-Frequency Oscillations in the Cerebellar Cortex of the Tottering Mouse." Journal of Neurophysiology 101, no. 1 (January 2009): 234–45. http://dx.doi.org/10.1152/jn.90829.2008.
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The tottering mouse is an autosomal recessive disorder involving a missense mutation in the gene encoding P/Q-type voltage-gated Ca2+channels. The tottering mouse has a characteristic phenotype consisting of transient attacks of dystonia triggered by stress, caffeine, or ethanol. The neural events underlying these episodes of dystonia are unknown. Flavoprotein autofluorescence optical imaging revealed transient, low-frequency oscillations in the cerebellar cortex of anesthetized and awake tottering mice but not in wild-type mice. Analysis of the frequencies, spatial extent, and power were used to characterize the oscillations. In anesthetized mice, the dominant frequencies of the oscillations are between 0.039 and 0.078 Hz. The spontaneous oscillations in the tottering mouse organize into high power domains that propagate to neighboring cerebellar cortical regions. In the tottering mouse, the spontaneous firing of 83% (73/88) of cerebellar cortical neurons exhibit oscillations at the same low frequencies. The oscillations are reduced by removing extracellular Ca2+and blocking L-type Ca2+channels. The oscillations are likely generated intrinsically in the cerebellar cortex because they are not affected by blocking AMPA receptors or by electrical stimulation of the parallel fiber–Purkinje cell circuit. Furthermore, local application of an L-type Ca2+agonist in the tottering mouse generates oscillations with similar properties. The beam-like response evoked by parallel fiber stimulation is reduced in the tottering mouse. In the awake tottering mouse, transcranial flavoprotein imaging revealed low-frequency oscillations that are accentuated during caffeine-induced attacks of dystonia. During dystonia, oscillations are also present in the face and hindlimb electromyographic (EMG) activity that become significantly coherent with the oscillations in the cerebellar cortex. These low-frequency oscillations and associated cerebellar cortical dysfunction demonstrate a novel abnormality in the tottering mouse. These oscillations are hypothesized to be involved in the episodic movement disorder in this mouse model of episodic ataxia type 2.
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Ruiz-Díez, Víctor, Javier Toledo, Jorge Hernando-García, Abdallah Ababneh, Helmut Seidel, and José Sánchez-Rojas. "A Geometrical Study on the Roof Tile-Shaped Modes in AlN-Based Piezoelectric Microcantilevers as Viscosity–Density Sensors." Sensors 19, no. 3 (February 6, 2019): 658. http://dx.doi.org/10.3390/s19030658.
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Cantilever resonators based on the roof tile-shaped modes have recently demonstrated their suitability for liquid media monitoring applications. The early studies have shown that certain combinations of dimensions and order of the mode can maximize the Q-factor, what might suggest a competition between two mechanisms of losses with different geometrical dependence. To provide more insight, a comprehensive study of the Q-factor and the resonant frequency of these modes in microcantilever resonators with lengths and widths between 250 and 3000 µm and thicknesses between 10 and 60 µm is presented. These modes can be efficiently excited by a thin piezoelectric AlN film and a properly designed top electrode layout. The electrical and optical characterization of the resonators are performed in liquid media and then their performance is evaluated in terms of quality factor and resonant frequency. A quality factor as high as 140 was measured in isopropanol for a 1000 × 900 × 10 µm3 cantilever oscillating in the 11th order roof tile-shaped mode at 4 MHz; density and viscosity resolutions of 10−6 g/mL and 10−4 mPa·s, respectively are estimated for a geometrically optimized cantilever resonating below 1 MHz.
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Lenstra, Daan, Alexis P. A. Fischer, Amani Ouirimi, Alex Chamberlain Chime, Nixson Loganathan, and Mahmoud Chakaroun. "Ultra-short optical pulse generation in micro OLEDs and the perspective of lasing." Journal of Optics 24, no. 3 (February 4, 2022): 034007. http://dx.doi.org/10.1088/2040-8986/ac4cd1.
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Abstract We report experimental and theoretical investigations with an in-house fabricated tris(8‐hydroxyquinoline)‐aluminum (Alq3)-based high-speed micro-organic light-emitting diodes (μ-OLEDs) and demonstrate very promising optical pulse responses as short as 400 ps. With a model for an electrically pumped OLED, we simulate the emission of sub-nanosecond optical pulses. The model includes field-dependent (Poole-Frenkel) Langevin recombination and reabsorption of photons by singlets (Stokes-shifted), and by triplets (TA). The good agreement between the measurement and the simulation is the basis for further study of the prospects on the ps time scale, i.e. stimulated emission and conditions for laser operation. For an Alq3-based micro-OLED with high-Q optical cavity, we predict pulsed laser operation with damped relaxation oscillations in the GHz regime and several orders of magnitude linewidth narrowing, but only during 3 ns at most. The simulated current density threshold values vary from 10 kA cm−2 for Q= 500 to less than 1 kA cm−2 for Q = 1000. No continuous-wave (CW) lasing is found due to the accumulation of triplet excitons for t > 5 ns, which has two deteriorating effects, (a) suppression of the gain-providing singlet excitons due to singlet-triplet absorption and (b) suppression of the photon density due to photon absorption by triplets (TA). Prospects for CW-lasing with other organic molecules are discussed.
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Wang, Fu Zhong, and Qiong Xia Yu. "Speed-Regulation System of PMLSM Based on BP Neural Network PID Control." Advanced Materials Research 466-467 (February 2012): 1217–21. http://dx.doi.org/10.4028/www.scientific.net/amr.466-467.1217.
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For the characteristics of permanent magnet linear synchronous motor (PMLSM) hoisting system’s nonlinear, time-varying and vulnerable to disturbance, based on the established PMLSM d-q axis dynamic model, designed of an improved BP neural network PID speed controller. Modified the fixed learning rate in BP neural network to adaptive adjustable, and added the momentum to reduce the oscillation tendency in the learning process, greatly improved the convergence speed and avoided the network into a local minimum. Compared with the simulations of traditional PID and the improved BP network PID speed controller, the results showed that the improved BP neural network PID speed controller had the high quality and it can make the system with better dynamic performance and robustness.
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Dai, Aiguo. "Recent Climatology, Variability, and Trends in Global Surface Humidity." Journal of Climate 19, no. 15 (August 1, 2006): 3589–606. http://dx.doi.org/10.1175/jcli3816.1.
Повний текст джерелаАнотація:
Abstract In situ observations of surface air and dewpoint temperatures and air pressure from over 15 000 weather stations and from ships are used to calculate surface specific (q) and relative (RH) humidity over the globe (60°S–75°N) from December 1975 to spring 2005. Seasonal and interannual variations and linear trends are analyzed in relation to observed surface temperature (T) changes and simulated changes by a coupled climate model [namely the Parallel Climate Model (PCM)] with realistic forcing. It is found that spatial patterns of long-term mean q are largely controlled by climatological surface temperature, with the largest q of 17–19 g kg−1 in the Tropics and large seasonal variations over northern mid- and high-latitude land. Surface RH has relatively small spatial and interannual variations, with a mean value of 75%–80% over most oceans in all seasons and 70%–80% over most land areas except for deserts and high terrain, where RH is 30%–60%. Nighttime mean RH is 2%–15% higher than daytime RH over most land areas because of large diurnal temperature variations. The leading EOFs in both q and RH depict long-term trends, while the second EOF of q is related to the El Niño–Southern Oscillation (ENSO). During 1976–2004, global changes in surface RH are small (within 0.6% for absolute values), although decreasing trends of −0.11% ∼ −0.22% decade−1 for global oceans are statistically significant. Large RH increases (0.5%–2.0% decade−1) occurred over the central and eastern United States, India, and western China, resulting from large q increases coupled with moderate warming and increases in low clouds over these regions during 1976–2004. Statistically very significant increasing trends are found in global and Northern Hemispheric q and T. From 1976 to 2004, annual q (T) increased by 0.06 g kg−1 (0.16°C) decade−1 globally and 0.08 g kg−1 (0.20°C) decade−1 in the Northern Hemisphere, while the Southern Hemispheric q trend is positive but statistically insignificant. Over land, the q and T trends are larger at night than during the day. The largest percentage increases in surface q (∼1.5% to 6.0% decade−1) occurred over Eurasia where large warming (∼0.2° to 0.7°C decade−1) was observed. The q and T trends are found in all seasons over much of Eurasia (largest in boreal winter) and the Atlantic Ocean. Significant correlation between annual q and T is found over most oceans (r = 0.6–0.9) and most of Eurasia (r = 0.4–0.8), whereas it is insignificant over subtropical land areas. RH–T correlation is weak over most of the globe but is negative over many arid areas. The q–T anomaly relationship is approximately linear so that surface q over the globe, global land, and ocean increases by ∼4.9%, 4.3%, and 5.7% per 1°C warming, respectively, values that are close to those suggested by the Clausius–Clapeyron equation with a constant RH. The recent q and T trends and the q–T relationship are broadly captured by the PCM; however, the model overestimates volcanic cooling and the trends in the Southern Hemisphere.
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Lankisch, Tim O., Yasuhiro Tsunoda, Yuanxu Lu, and Chung Owyang. "Characterization of CCKA receptor affinity states and Ca2+ signal transduction in vagal nodose ganglia." American Journal of Physiology-Gastrointestinal and Liver Physiology 282, no. 6 (June 1, 2002): G1002—G1008. http://dx.doi.org/10.1152/ajpgi.00313.2001.
Повний текст джерелаАнотація:
CCKA receptors are present on vagal afferent fibers. The objectives of this study were to identify the presence of high- and low-affinity CCKA receptors on nodose ganglia and to characterize the intracellular calcium signal transduction activated by CCK. Stimulation of acutely isolated nodose ganglion cells from rats with 1 nM CCK-8 primarily evoked a Ca2+ transient followed by a sustained Ca2+plateau (45% of cells responded), whereas 10 pM CCK-8 evoked Ca2+ oscillations (37% of cells responded). CCK-OPE, a high-affinity agonist and low-affinity antagonist of CCKAreceptors, primarily elicited Ca2+ oscillations (29% of cells responded). CCK-OPE inhibited the Ca2+ transient induced by 1 nM CCK-8 but not by carbachol and high K+. This result suggests the presence of high- and low-affinity states of CCKA receptors on nodose ganglia. We further demonstrated that nicardipine (10 μM) but not ω-conotoxins GVIA and MVIIC (10–100 nM) abolished Ca2+ signaling induced by CCK-8, indicating that an L-type voltage-dependent Ca2+ channel and not an N- or Q-type Ca2+ channel is coupled to CCKA receptors. In a separate study, we showed that the G protein activator NaF (10 mM) elicited a Ca2+ transient and inhibited CCK-8-evoked Ca2+ signaling, indicative of G protein(s) involvement in CCKA receptor activity. The Gq protein antagonist Gp antagonist-2A (10 μM) also abolished the action of CCK-8. This study indicates that CCKA receptors exist in both high- and low-affinity states in the nodose ganglia. Activation of high-affinity CCKAreceptors elicits Ca2+ oscillations, whereas stimulation of low-affinity CCKA receptors evokes a sustained Ca2+ plateau. These Ca2+-signaling modes are mediated through the L-type Ca2+ channel and involve the participation of Gq protein.
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Olkhovskiy, Ivan, and Anatoliy Fursov. "QUASIOPTICAL SOLID-STATE GENERATOR WITH OPEN QUASI-FREQUENCY SPHEREOSELETAL OSCILLATING SYSTEM." Bulletin of the National Technical University «KhPI» Series: New solutions in modern technologies, no. 2(8) (June 15, 2021): 30–37. http://dx.doi.org/10.20998/2413-4295.2021.02.05.
Повний текст джерелаАнотація:
The results of research related to the development of an effective high-Q open oscillatory system of quasi-optical solid-state generators of millimeter and submillimeter wavelength ranges are presented. It is shown that for the stable operation of solid-state generators based on Gunn diodes and avalanche-transit diodes (ATDs) located inside an open resonator (OR), a significant rarefaction of the resonance frequency spectrum is required, which excludes jumps of the generation frequency. Taking this requirement into account, a spheroechelett open resonator (SE OR) is proposed as an open oscillatory system of solid-state generators, one of the mirrors of which is a reflective lattice of the “echelette” type. The paper presents the results of “cold” measurements of the spectrum of resonance frequencies of the SE OP, which indicate that the SE OP indeed has a significantly rarefied spectrum both in transverse and, which is very important, in longitudinal modes of oscillations. The conditions necessary for the excitation of high-quality stable oscillations with high energy efficiency in a solid-state generator based on an SE OR are discussed and implemented. The results of an experimental study of a quasi-optical generator based on an 8-mm ATD wavelength range are presented. The analysis of the obtained characteristics and their qualitative explanation on the basis of the proposed model of the processes occurring in the investigated generator are presented. It is shown that the SE OR can be used as a resonant system in the entire EHF range of not only solid-state, but also electronic-vacuum devices. Finally, a way is outlined in the direction of further rarefaction of the spectrum of the SE OR in order to create a really single-frequency open oscillatory system.
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Bonnet-Bidaud, J. M., M. Mouchet, E. Falize, L. Van Box Som, C. Busschaert, D. A. H. Buckley, H. Breytenbach, T. R. Marsh, R. P. Ashley, and V. S. Dhillon. "Fast quasi-periodic oscillations in the eclipsing polar VV Puppis from VLT and XMM-Newton observations." Astronomy & Astrophysics 633 (January 2020): A145. http://dx.doi.org/10.1051/0004-6361/201935741.
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We present high time resolution optical photometric data of the polar VV Puppis obtained simultaneously in three filters (u′, HeII λ4686, r′) with the ULTRACAM camera mounted at the ESO-VLT telescope. An analysis of a long 50 ks XMM-Newton observation of the source, retrieved from the database, is also provided. Quasi-periodic oscillations (QPOs) are clearly detected in the optical during the source bright phase intervals when the accreting pole is visible, confirming the association of the QPOs with the basis of the accretion column. QPOs are detected in the three filters at a mean frequency of ∼0.7 Hz with a similar amplitude ∼1%. Mean orbitally-averaged power spectra during the bright phase show a rather broad excess with a quality factor Q = ν/Δν = 5−7 but smaller data segments commonly show a much higher coherency with Q up to 30. The X-ray Multi-mirror Mission XMM (0.5–10 keV) observation provides the first accurate estimation of the hard X-ray component with a high kT ∼ 40 keV temperature and confirms the high extreme ultraviolet (EUV)-soft/hard ratio in the range of 4−15 for VV Pup. The detailed X-ray orbital light curve displays a short Δϕ ≃ 0.05 ingress into self-eclipse of the active pole, indicative of an accretion shock height of ∼75 km. No significant X-ray QPOs are detected with an amplitude upper limit of ∼30% in the range 0.1–5 Hz. Detailed hydrodynamical numerical simulations of the post-shock accretion region with parameters consistent with VV Pup demonstrate that the expected frequencies from radiative instability are identical for X-rays and optical regime at values ν ∼ 40–70 Hz, more than one order magnitude higher than observed. This confirms previous statements suggesting that present instability models are unable to explain the full QPO characteristics within the parameters commonly known for polars.
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Cheng, Lijing, Kevin E. Trenberth, John T. Fasullo, Michael Mayer, Magdalena Balmaseda, and Jiang Zhu. "Evolution of Ocean Heat Content Related to ENSO." Journal of Climate 32, no. 12 (May 23, 2019): 3529–56. http://dx.doi.org/10.1175/jcli-d-18-0607.1.
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Abstract As the strongest interannual perturbation to the climate system, El Niño–Southern Oscillation (ENSO) dominates the year-to-year variability of the ocean energy budget. Here we combine ocean observations, reanalyses, and surface flux data with Earth system model simulations to obtain estimates of the different terms affecting the redistribution of energy in the Earth system during ENSO events, including exchanges between ocean and atmosphere and among different ocean basins, and lateral and vertical rearrangements. This comprehensive inventory allows better understanding of the regional and global evolution of ocean heat related to ENSO and provides observational metrics to benchmark performance of climate models. Results confirm that there is a strong negative ocean heat content tendency (OHCT) in the tropical Pacific Ocean during El Niño, mainly through enhanced air–sea heat fluxes Q into the atmosphere driven by high sea surface temperatures. In addition to this diabatic component, there is an adiabatic redistribution of heat both laterally and vertically (0–100 and 100–300 m) in the tropical Pacific and Indian oceans that dominates the local OHCT. Heat is also transported and discharged from 20°S–5°N into off-equatorial regions within 5°–20°N during and after El Niño. OHCT and Q changes outside the tropical Pacific Ocean indicate the ENSO-driven atmospheric teleconnections and changes of ocean heat transport (i.e., Indonesian Throughflow). The tropical Atlantic and Indian Oceans warm during El Niño, partly offsetting the tropical Pacific cooling for the tropical oceans as a whole. While there are distinct regional OHCT changes, many compensate each other, resulting in a weak but robust net global ocean cooling during and after El Niño.
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Younesi, Abdollah, Hossein Shayeghi, and Pierluigi Siano. "Assessing the Use of Reinforcement Learning for Integrated Voltage/Frequency Control in AC Microgrids." Energies 13, no. 5 (March 8, 2020): 1250. http://dx.doi.org/10.3390/en13051250.
Повний текст джерелаАнотація:
The main purpose of this paper is to present a novel algorithmic reinforcement learning (RL) method for damping the voltage and frequency oscillations in a micro-grid (MG) with penetration of wind turbine generators (WTG). First, the continuous-time environment of the system is discretized to a definite number of states to form the Markov decision process (MDP). To solve the modeled discrete RL-based problem, Q-learning method, which is a model-free and simple iterative solution mechanism is used. Therefore, the presented control strategy is adaptive and it is suitable for the realistic power systems with high nonlinearities. The proposed adaptive RL controller has a supervisory nature that can improve the performance of any kind of controllers by adding an offset signal to the output control signal of them. Here, a part of Denmark distribution system is considered and the dynamic performance of the suggested control mechanism is evaluated and compared with fuzzy-proportional integral derivative (PID) and classical PID controllers. Simulations are carried out in two realistic and challenging scenarios considering system parameters changing. Results indicate that the proposed control strategy has an excellent dynamic response compared to fuzzy-PID and traditional PID controllers for damping the voltage and frequency oscillations.
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Ojaimi, Hasan F. "Nucleon momentum distributions and elastic electron scattering form factors for 58Ni, 60Ni, 62Ni, and 64Ni isotopes using the framework of coherent fluctuation model." Iraqi Journal of Physics (IJP) 12, no. 24 (February 17, 2019): 33–42. http://dx.doi.org/10.30723/ijp.v12i24.318.
Повний текст джерелаАнотація:
The nucleon momentum distributions (NMD) and elastic electron scattering form factors of the ground state for some 1f-2p-shell nuclei, such as 58Ni, 60Ni, 62Ni, and 64Niisotopes have been calculated in the framework of the coherent fluctuation model (CFM) and expressed in terms of the weight function lf(x)l2 . The weight function (fluctuation function) has been related to the nucleon density distribution (NDD) of the nuclei and determined from the theory and experiment. The NDD is derived from a simple method based on the use of the single particle wave functions of the harmonic oscillator potential and the occupation numbers of the states. The feature of the long-tail behavior at high momentum region of the NMD’s has been obtained by both the theoretical and experimental weight functions. The calculated elastic electron scattering form factors for considered isotopes are in reasonable agreement with those of experimental data throughout all values of momentum transfer q.
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Tsarev, V. A., A. Yu Miroshnichenko, A. V. Gnusarev, and N. A. Akafyeva. "Investigation of the Two-Mode Regime of Two-Gap Photonic-Crystal Resonance Systems Produced on a Printed Circuit Board with Fractal Elements "Minkowski Island." Journal of the Russian Universities. Radioelectronics 24, no. 5 (November 29, 2021): 80–88. http://dx.doi.org/10.32603/1993-8985-2021-24-5-80-88.
Повний текст джерелаАнотація:
Introduction. The development of new amplifiers and generators of the Ku- and K-bands (12…27 GHz) for use in onboard equipment is increasingly attracting research interest. Low-voltage multi-beam klystrons (LMBK) can be a promising element base for such devices. Serious problems are associated with the need to suppress parasitic modes of oscillations in NMLK operating in the centimeter and millimeter range. A possible solution is to use double-gap photonic-crystal resonators (DPCR) in LMBK. Another promising direction for improving the characteristics of such resonators is to use resonant segments of strip lines with fractal elements. In this case, the strip lines are placed on a dielectric substrate in the interaction space. Such resonators exhibit new properties that are useful for klystrons (an increase in characteristic impedance, suppression of the spectrum of unwanted frequencies, a reduction in mass and dimensions).Aim. Determination of an optimal set of electrodynamic and electronic parameters of double-gap photonic-crystal resonance systems with fractal elements "Minkowski Island" when operated as part of the LMBK resonator system, excited on π- and 2π-modes of oscillation.Materials and methods. To calculate the electrodynamic parameters of resonators, the method of finite differences in the time domain was used. The well-known Wessel-Berg method was used to calculate electronic parameters, such as the Ge / G0 electronic conductivity and the coupling coefficient M.Results. The main electrodynamic parameters of the resonator – Q-factor, resonant frequency and characteristic impedance – were investigated. The electronic parameters of the resonator, the coefficient of coupling with the electron beam, and the relative electronic conductivity for π- and 2π-modes of oscillations were calculated. In this case, three variants of the resonator with zero, first and second iterations of the fractal element were investigated. The amplitude-frequency characteristics of the resonator were investigated with a change in the pitch of the photonic crystal lattice. An estimation of the inhomogeneity of the high-frequency field in the interaction spaces of the resonator was carried out. Operational conditions were determined simultaneously for two types of oscillations without self-excitation.Conclusion. The results can find application in the development of resonator systems for klystron-type devices in the centimeter and millimeter ranges.
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Flaiyh, Ghaith N. "Nucleon momentum distributions and elastic electron scattering form factors for 48Ti and 54Fe nuclei." Iraqi Journal of Physics (IJP) 12, no. 24 (February 18, 2019): 100–109. http://dx.doi.org/10.30723/ijp.v12i24.327.
Повний текст джерелаАнотація:
The nucleon momentum distributions (NMD) for the ground state and elastic electron scattering form factors have been calculated in the framework of the coherent fluctuation model and expressed in terms of the weight function (fluctuation function). The weight function has been related to the nucleon density distributions of nuclei and determined from theory and experiment. The nucleon density distributions (NDD) is derived from a simple method based on the use of the single particle wave functions of the harmonic oscillator potential and the occupation numbers of the states. The feature of long-tail behavior at high momentum region of the NMD has been obtained using both the theoretical and experimental weight functions. The observed electron scattering form factors for 48Ti and 54Fe nuclei are in reasonable agreement with the present calculations throughout all values of momentum transfer q.
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Hayrapetyan, Yegisabeth, Hovseph Petrosyan, Hovnan Hunanyan, and Artyom Tsaturyan. "High-precision two-phase laser rangefinder PFSD-1,2." E3S Web of Conferences 97 (2019): 06042. http://dx.doi.org/10.1051/e3sconf/20199706042.
Повний текст джерелаАнотація:
Performing high-precision linear measurements is one of the main tasks of modern engineering geodesy. Consequently, the development and creation of high-precision laser rangefinders and refractometers with a relative measurement error of not more than 3.10-7, becomes an urgent scientific and technical problem. Wide theoretical and experimental studies in the problem laboratory of geodetic measurements of NUACA have accumulated a sufficient amount of experimental results for the construction of modern high-precision light meter with the determination of the residual part of the phase cycle with an error of 0.03-0.05 mm. The article discusses issues related to improving the accuracy of linear measurements developed in the NUACA of high-precision light rangefinder. A two-phase modulation measurement method is proposed, when signals shifted by 180° are formed optically using a phase plate at λ/2. This modulation method of linear measurements provided the phase error of linear measurements mφ = 0.03-0.05 mm. The article also discusses the issue of reducing the modulation power. For this purpose, it is proposed to install a high-quality buffer Q-resonator between the high-quality light modem and the low-quality microwave oscillator.
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Mrad, Mohamad, Ahmad Tarhini, Pierre-Yves Bourgeois, and Vincent Giordano. "Physics of the sapphire whispering-gallery-mode solid-state MASER oscillator." European Physical Journal Applied Physics 91, no. 3 (September 2020): 31001. http://dx.doi.org/10.1051/epjap/2020200107.
Повний текст джерелаАнотація:
The Cryogenic Sapphire Oscillator (CSO) is currently the best available technology that can provide a relative frequency stability better than 10−15 with integration times between 1 s and 10,000 s. But, the CSO remains a complex instrument that requires multiple loop controls to achieve the best frequency stability. The possibility to use the sapphire resonator in a self-sustained MASER oscillator presents an elegant alternative to the CSO. Here, sustaining the amplification is achieved through the interaction between a high-Q factor whispering gallery mode and the paramagnetic Fe3+ ions, which are present in small concentration in the sapphire crystal. The Fe3+ ion exhibits three energy states enabling to realize a self-sustaining solid-state maser. Although, this principle has been already experimentally demonstrated few years ago, its development as a truly usable ultra-stable source has not yet been completed, mainly due to the lack of control of the complex physical phenomena involved. This paper complements the previous theoretical work based on the rate equations model. Here we derive the full quantum equations describing the evolution of the Fe3+ ions inside the sapphire lattice and submitted to a pump and a maser signal. The influence of the ions concentration and spin-spin relaxation time will be pointed out.
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Dong, Runnan, Shi Liu, and Geng Liang. "Research on Control Parameters for Voltage Source Inverter Output Controllers of Micro-Grids Based on the Fruit Fly Optimization Algorithm." Applied Sciences 9, no. 7 (March 29, 2019): 1327. http://dx.doi.org/10.3390/app9071327.
Повний текст джерелаАнотація:
Due to the strong intermittency of micro-resources, the poor grid-tied power quality, and the high generation-demand sensitivity in micro-grids, research into the control methods of micro-grid systems has always been a notable issue in the field of micro-grids. The inverter is the core control equipment at the primary control level of the micro-grid, and the key factors affecting its output performance can be divided into three categories: control methods, hardware configuration, and control parameter design. Taking the classical active and reactive power (P-Q) control structure and the three-phase, two-stage inverter topology model as an example, this paper designs a parameter for offline tuning, and an online self-tuning optimization method for an inverter control system based on the fruit fly optimization algorithm (FOA). By simulating and comparing the inverter controllers with non-optimized parameters in the same object and environment, the designed parameter tuning method is verified. Specifically, it improves the dynamic response speed of the inverter controller, reduces the steady-state error and oscillation, and enhances the dynamic response performance of the controller.
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Kogan, A. Ya. "Mathematical model of the formation and development of wave-shaped rail wear when an electric locomotive operates in the traction mode in tangent sections of the track." Vestnik of the Railway Research Institute 78, no. 3 (July 28, 2019): 131–40. http://dx.doi.org/10.21780/2223-9731-2019-78-3-131-140.
Повний текст джерелаАнотація:
The problem of wave-shaped rail wear is highly relevant for rail transport. The paper presents a mathematical model of the formation and development of wave-shaped rail wear. The task of estimating vertical wear of the rail head under the axles of electric locomotives passing in the traction mode is considered. A technique has been developed that allows building chain of calculations that determine the formation and development of a wave-shaped rail head wear. A specific calculation example is given, illustrating the process of propagation of a wave-shaped wear from the source of its formation in the direction of train motion. An example of the calculation allows drawing the following conclusions:1. Wave-shaped wear primarily occurs when the shock interaction of the wheel of an electric locomotive moving in the traction mode and a rail thread having imperfections of the rolling surface. Such imperfections, among others, may be a joint with a significant gap or a “step down” in the direction of the locomotive, as well as a welded joint with defect 46.3-4.2. Wavelength of the wave-shaped rail wear, its configuration and amplitude of the fundamental tone are determined mainly by joint oscillations of the wheel-motor unit of the locomotive and the track infrastructure in the field of high-frequency oscillations (120 – 180 Hz).3. Multivariate calculations showed that in steady state, the distribution speed of wave-shaped rail wear in the direction of train motion (as a function of the number of axles of electric locomotives passed in traction mode) is directly proportional to the vertical load at the wheel and rail contact in the slip zone 0≤Q≤F/(2nψk), is inversely proportional to wear resistance C and significantly depends on the parameters of the undercarriage of the electric train and the track superstructure.
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Lu, Yifan, Marco Amabili, Jian Wang, Fei Yang, Honghao Yue, Ye Xu, and Hornsen Tzou. "Active vibration control of a polyvinylidene fluoride laminated membrane plate mirror." Journal of Vibration and Control 25, no. 19-20 (July 11, 2019): 2611–26. http://dx.doi.org/10.1177/1077546319862445.
Повний текст джерелаАнотація:
Lightweight optical mirrors usually play key roles in aerospace and optical structural systems applied to space telescopes, radars, solar collectors, communication antennas, etc. Due to their high flexibility and low damping properties, external excitations such as orbital maneuver may induce unexpected oscillations and thus reduce their working performance. Active vibration control is therefore essential for the lightweight optical mirror systems. In this spirit, a lightweight mirror structronic system with a linear quadratic optimal controller is presented. The mirror is modeled as a membrane plate with pretension and distributed polyvinylidene fluoride sensors and actuators. The sensing sensitivity of the piezoelectric (PVDF) sensors and the modal actuation factor of the PVDF actuators are derived. The state-space equations are established and the feedback control gains between sensing and control signals are obtained. Sensor and actuator of different shape, size, and position are employed to actively control the first four natural modes of the mirror. The influences of mode order, pretension, and the two weighting factors Q and R on the control performance are also investigated. Analytical results in this paper could guide the design and layout of the PZT sensor and actuator on lightweight membrane plate mirrors.
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Pei, Lijun, Hongyang Zhang, and Yueli Chen. "Sudden Transition from Equilibrium to Hybrid Chaos and Periodic Oscillations of the State-Dependent Round-Trip Delayed Nonsmooth Compound TCP with GRED Congestion Control System via HB-AFT." Complexity 2020 (November 21, 2020): 1–15. http://dx.doi.org/10.1155/2020/5982403.
Повний текст джерелаАнотація:
In this paper, the nonsmooth compound transmission control protocol (TCP) with the gentle random early detection (GRED) system with the state-dependent round-trip delay is investigated in detail. Uniqueness of the positive equilibrium is proved firstly. Then, the closed approximate periodic solutions in this state-dependent delayed nonsmooth compound TCP with the GRED model are obtained by employing the harmonic balance and alternating frequency/time domain (HB-AFT) method. Then, we compare the results generated by numerical simulations with those of the closed approximate expressions obtained by HB-AFT. It indicates that HB-AFT is simple, correct, and powerful for state-dependent delayed nonsmooth dynamical systems. Finally, we find the complicated dynamic: chaos. It is a grazing chaos with a hybrid property, i.e., where usually w oscillates at a very low frequency and q oscillates at a very high frequency. And, the route to chaos is a very rare route, i.e., the instantaneous and local transition of stable equilibrium to chaos. So, to the end of stability and good performance, we should adjust the parameters carefully to avoid the periodic and chaotic oscillations.
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Nguyen, Van Luc, Tomohiro Degawa, and Tomomi Uchiyama. "Numerical simulation of the interaction between a vortex ring and a bubble plume." International Journal of Numerical Methods for Heat & Fluid Flow 29, no. 9 (September 2, 2019): 3192–224. http://dx.doi.org/10.1108/hff-12-2018-0734.
Повний текст джерелаАнотація:
Purpose This paper aims to provide discussions of a numerical method for bubbly flows and the interaction between a vortex ring and a bubble plume. Design/methodology/approach Small bubbles are released into quiescent water from a cylinder tip. They rise under the buoyant force, forming a plume. A vortex ring is launched vertically upward into the bubble plume. The interactions between the vortex ring and the bubble plume are numerically simulated using a semi-Lagrangian–Lagrangian approach composed of a vortex-in-cell method for the fluid phase and a Lagrangian description of the gas phase. Findings A vortex ring can transport the bubbles surrounding it over a distance significantly depending on the correlative initial position between the bubbles and the core center. The motion of some bubbles is nearly periodic and gradually extinguishes with time. These bubble trajectories are similar to two-dimensional-helix shapes. The vortex is fragmented into multiple regions with high values of Q, the second invariant of velocity gradient tensor, settling at these regional centers. The entrained bubbles excite a growth rate of the vortex ring's azimuthal instability with a formation of the second- and third-harmonic oscillations of modes of 16 and 24, respectively. Originality/value A semi-Lagrangian–Lagrangian approach is applied to simulate the interactions between a vortex ring and a bubble plume. The simulations provide the detail features of the interactions.
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Idini, Benjamin, and David J. Stevenson. "The Gravitational Imprint of an Interior–Orbital Resonance in Jupiter–Io." Planetary Science Journal 3, no. 4 (April 1, 2022): 89. http://dx.doi.org/10.3847/psj/ac6179.
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Abstract At mid-mission perijove 17, NASA’s Juno mission has revealed a 7σ discrepancy between Jupiter’s observed high-degree tidal response and the theoretical equilibrium tidal response, namely, the Love number k 42. Here we propose an interpretation for this puzzling disagreement based on an interior–orbital resonance between internal gravity waves trapped in Jupiter’s dilute core and the orbital motion of Io. We use simple Jupiter models to calculate a fractional correction Δk 42 to the equilibrium tidal response that comes from the dynamical tidal response of a g–mode trapped in Jupiter’s dilute core. Our results suggest that an extended dilute core (r ≳ 0.7 R J) produces an interior–orbital resonance with Io that modifies Jupiter’s tidal response in Δk 42 ∼ −11%, allowing us to fit Juno’s k 42. In our proposed self-consistent scenario, Jupiter’s dilute core evolves in resonant locking with Io’s orbital migration, which allows the interior–orbital resonance to persist over geological timescales. This scenario requires a dilute core that becomes smoother or shrinks over time, together with a 4 2 g 1 mode (ℓ, m, n = 4, 2, 1) with resonant tidal dissipation reaching Q 4 ∼ 1000. Jupiter’s dilute core evolution path and the dissipation mechanism for the resonant 4 2 g 1 mode are uncertain and motivate future analysis. No other alternative exists so far to explain the 7σ discrepancy in Juno k 42. Our proposed interior–orbital resonance can be tested by Juno observations of k 42 tides raised on Jupiter by Europa, as obtained at the end of the extended mission (mid-2025), and by future seismological observations of Jupiter’s 4 2 g 1 mode oscillation frequency.
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Kalaga, Joanna K., Wiesław Leoński, and Radosław Szczęśniak. "Quantum steering in an asymmetric chain of nonlinear oscillators." Photonics Letters of Poland 9, no. 3 (September 30, 2017): 97. http://dx.doi.org/10.4302/plp.v9i3.759.
Повний текст джерелаАнотація:
We discuss here a possibility of generation of steerable states in asymmetric chains comprising three Kerr-like nonlinear oscillators. We show that steering between modes can be generated in the system and it strongly depends on the asymmetry of internal couplings in our model. We can lead to the appearance of new steering effects, which were not present in symmetric models already studied in the literature. Full Text: PDF ReferencesE. Schrödinger, "Discussion of Probability Relations between Separated Systems", Math. Proc. Camb. Phil. Soc. 31, 555 (1935). CrossRef M.D. Reid, "Demonstration of the Einstein-Podolsky-Rosen paradox using nondegenerate parametric amplification", Phys. Rev. A 40, 913 (1989). CrossRef E.G. Cavalcanti, M.D. Reid, "Uncertainty relations for the realization of macroscopic quantum superpositions and EPR paradoxes", Journal of Modern Optics 54, 2373 (2007). CrossRef S.P. Walborn, A. Salles, R.M. Gomes, F. Toscano, P.H. Souto Ribeiro, "Revealing Hidden Einstein-Podolsky-Rosen Nonlocality", Phys. Rev. Lett. 106, 130402 (2011). CrossRef H.M. Wiseman, S.J. Jones, A.C. Doherty, "Steering, Entanglement, Nonlocality, and the Einstein-Podolsky-Rosen Paradox", Phys. Rev. Lett. 98, 140402 (2007). CrossRef S.J. Jones, H.M. Wiseman, A.C. Doherty, "Entanglement, Einstein-Podolsky-Rosen correlations, Bell nonlocality, and steering", Phys. Rev. A 76, 052116 (2007). CrossRef J.K. Kalaga, W. Leoński, "Quantum steering borders in three-qubit systems", Quantum Inf Process 16, 175 (2017). CrossRef Q. He, Z. Ficek, "Einstein-Podolsky-Rosen paradox and quantum steering in a three-mode optomechanical system", Phys. Rev. A 89, 022332 (2014). CrossRef S. Kiesewetter, Q.Y. He, P.D. Drummond, M.D. Reid, "Scalable quantum simulation of pulsed entanglement and Einstein-Podolsky-Rosen steering in optomechanics", Phys. Rev. A 90, 043805 (2014). CrossRef K. Bartkiewicz, A. Cernoch, K. Lemr, A. Miranowicz, F. Nori, "Experimental temporal quantum steering", Scientific Reports 6, 38076 (2016). CrossRef A. Barasiński, B. Brzostowski, R. Matysiak, P. Sobczak, D. Woźniak, In: R. Wyrzykowski, J. Dongarra, K. Karczewski, J. Wasniewski editor, Parallel Processing and Applied Mathematics (PPAM 2013), Lecture Notes in Computer Science, vol 8385. Springer, Berlin, Heidelberg (2014). CrossRef A. Drzewiński, J. Sznajd, "On the real-space renormalization-group study of some 2D quantum spin systems", Physica A 170, 415 (1991). CrossRef G.J. Milburn, C.A. Holmes, "Quantum coherence and classical chaos in a pulsed parametric oscillator with a Kerr nonlinearity", Phys. Rev. A 44, 4704 (1991). CrossRef W. Leoński, "Quantum and classical dynamics for a pulsed nonlinear oscillator", Physica A 233, 365 (1996). CrossRef A. Kowalewska-Kudłaszyk, J.K. Kalaga, W. Leoński, "Long-time fidelity and chaos for a kicked nonlinear oscillator system", Physics Letters A 373, 1334 (2009). CrossRef J.K. Kalaga, W. Leoński, "Two proposals of quantum chaos indicators related to the mean number of photons: pulsed Kerr-like oscillator case", Proc. SPIE 10142, 101421L (2016). CrossRef A. Barasiński, W. Leoński, T. Sowiński, "Ground-state entanglement of spin-1 bosons undergoing superexchange interactions in optical superlattices", J. Opt. Soc. Am. B 31, 1845 (2014). CrossRef A. Barasiński, W. Leoński, "Symmetry restoring and ancilla-driven entanglement for ultra-cold spin-1 atoms in a three-site ring", Quantum Inf Process 16, 6 (2017). CrossRef D. Woźniak, A. Drzewiński, G. Kamieniarz, "Relaxation Dynamics in the Spin-1 Heisenberg Antiferromagnetic Chain after a Quantum Quench of the Uniaxial Anisotropy", Acta Physica Polonica A 130, 1395 (2016). CrossRef R. Szczęśniak, D. Szczęśniak, E.A. Drzazga, "Superconducting state in the atomic metallic hydrogen just above the pressure of the molecular dissociation", Solid State Communications 152, 2023 (2012). CrossRef A. P. Durajski, R. Szczęśniak, M.W. Jarosik, "Properties of the superconducting state in compressed sulphur", Phase Transitions 85, 727 (2012). CrossRef R. Szczęśniak, A. P. Durajski, "The thermodynamic properties of the high-pressure superconducting state in the hydrogen-rich compounds", Solid State Sciences 25, 45 (2013). CrossRef X. Wang, A. Miranowicz, H.R. Li, F. Nori, "Multiple-output microwave single-photon source using superconducting circuits with longitudinal and transverse couplings", Phys. Rev. A 94, 053858, (2016). CrossRef Y.X. Liu, X.W. Xu, A. Miranowicz, F. Nori, "From blockade to transparency: Controllable photon transmission through a circuit-QED system", Phys. Rev. A 89, 043818 (2014). CrossRef M.K. Olsen, "Spreading of entanglement and steering along small Bose-Hubbard chains", Phys. Rev. A 92, 033627 (2015). CrossRef E.G. Cavalcanti, Q.Y. He, M.D. Reid, H.M. Wiseman, "Unified criteria for multipartite quantum nonlocality", Phys. Rev. A 84, 032115 (2011). CrossRef
43
Jerman, Igor, and Vesna PeriÄek Krapež. "UHD, electronic homeopathy and organisms – do they share a common language?" International Journal of High Dilution Research - ISSN 1982-6206 15, no. 4 (August 18, 2021): 43–44. http://dx.doi.org/10.51910/ijhdr.v15i4.867.
Повний текст джерелаАнотація:
Introduction
Homeopathy, at least in its UHD aspect, proves that the biological function of molecules (their “messageâ€) can be transmitted from some original material substance through pure water to living systems (1). Even if in general this transmission is based on serial dilutions of mother tinctures, experiments demonstrate it can be realized also via modified environmental EM fields, i.e. through the air as is known from the experiments performed by Montagnier (2), Endler and our group (3). It is also known as electronic homeopathy and is capable of a very similar achievement to UHD homeopathy without any chemical continuity between mother tincture and the final informed water. Quantum field theory developed by Preparata and Del Giudice brings theoretical ground to understanding and explaining this, for contemporary physicists, seemingly impossible phenomenon (4). Namely, it is not only that molecular information can be transmitted and stored in pure (UHD) water, but also that it can provoke changes in organisms.
Theoretical model
According to quantum electrodynamics, the interactions between an original substance, water and an organism are enabled by coherent domains (CDs). Many experiments corroborate the capacity of CDs to get entangled (phase locking) with the complex field of mother tincture’s substance(s) and consequently to encode the message of the tincture. However this is not the end of the process; this code must later be decoded from the side of the organism (and it seems that it can be even decoded by chemical systems, according to Elia (5)) and make an appropriate reaction. We assume that in case of organisms the endogenous coherent EM field first proposed by Fröhlich is responsible for the decoding; however a homeostatic energy barrier must be broken. Many experiments confirm that even physiological states, not only chemical messages ((6, 7) can be transmitted through the same channel.
The language of CDs and other EM coherent modes is not violent – the message of a molecule is presented in a way that provokes a reaction but cannot force the organism into a pathological or dead state. Therefore we can speak of a subtle (bio)chemistry and pharmacology, based on coherent modes and using a universal common language understandable to molecules and organisms.
Conclusion
ï€ Chemicals, water coherent domains, endogenous coherent oscillations of organisms and physiological responses must share a common denominator;
ï€ quantum field oscillations and their wave structures could represent the denominator and therefore the active molecular information;
ï€ potentization somewhat sharpens these wave structures, gives them more penetrative power, which makes higher potencies (dilutions) generally more effective – as they must break the homeostatic barrier of organismic endogenous EM field.
ï€ understanding the language implied in the first point as well as deeper mechanisms of sharpening the molecular information will enable us to enter a new era of subtle (bio)chemistry and pharmacology, surpassing not only contemporary pharmaceutical practice, but also the homeopathic one.
References
[1] P. Bellavite, M. Marzotto, D. Olioso, E. Moratti, A. Conforti, High-dilution effects revisited. 1. Physicochemical aspects. Homeopathy. 103(1):4-21 (2014).
[2] Monatagnier et al., DNA waves and water, arXiv:1012.5166v1 [q-bio.OT] (2010).
[3] I. Jerman, R. RužiÄ, R. KraÅ¡ovec, M. Å karja, L. Mogilnicki, Electrical transfer of molecule information into water, its storage and bioeffects on plants and bacteria. Electromagnetic Biology and Medicine. 24(3): 341-354 (2005).
[4] E. Del Guidice, P. R. Spinetti, A. Tedeschi, Water Dynamics at the Root of Metamorphosis in Living Organisms. Water. 2010, 2, 566-568; doi:10.3390/w2030566.
[5] Elia V. in Niccoli M. 1999. Thermodynamics of extremely diluted aqueous solutions. Annals of the New York Academy of Sciences, 879: 241-248.
[6] C. W. Smith, Quanta and Coherence Effects in Water and Living Systems. The Journal of Alternative and Complementary Medicine. 10(1):69-78. (2004).
[7] A. Foletti, J. Pokorny, Biophysical approach to low back pain: a pilot report. Electromagnetic Biology and Medicine. 34 (2): 156-159 (2015).
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Yetirmishli, Gurban, and Sabina Kazimova. "The first results of estimating the depth of the Moho surface by the method of converted Ps-waves for the Azerbaijan part of the Greater Caucasus." Russian Journal of Seismology 2, no. 3 (September 30, 2020): 78–87. http://dx.doi.org/10.35540/2686-7907.2020.3.07.
Повний текст джерелаАнотація:
The methodology of the converted waves, or as it is commonly called, the "Receiver function" method, is well known and is widely used throughout the world to study the deep structure of the Earth up to 800 km. The method is based on the registration and interpretation of converted Ps waves. These studies were carried out as part of the International Seismotomo-graphic Laboratory using a software package developed at the University of Missouri (USA). One of the best regions for studying the early stages of mountain building is the Greater Caucasus, where most of the volcanism and mountain building appears to be 5 million years. Of particular interest is the immersion zone of the Kura Basin beneath the Greater Caucasus, the so-called subduction zone, which has not been sufficiently studied to date. To this end, we began our studies of the depth of the Moho border with this region. Thus, for the first time on the basis of the analysis of the wave characteristics of distant earthquakes recorded at seismic and telemetric stations of the RSSC, within the framework of the international project "Transect", the depths of the Moho border for the Azerbaijan part of the Greater Caucasus were refined by the method of exchange reflected Ps waves ("Receiver function"). Seismo-grams of the selected earthquakes were processed using the Seismic Analysis Code (SAC) software package under the MacOs operating system. The study examined seismological data recorded by a network of telemetry stations (N=20) for 2009-2019. In total, 2428 earth-quakes recorded at an epicenter distance of 35 to 90 degrees were analyzed. At the first stage, frequency filtering was carried out in order to eliminate oscillations that were too high, containing the effects of random scattering on inhomogeneities, and too low frequencies that re-duce the resolution. The working range of the periods ranged from two to 10 seconds. Next, two-dimensional and three-dimensional rotation of the axes was carried out. The summation of all traces was carried out with time shifts relative to some reference epicentral distance, which is assumed to be 60 degrees. On the summarized Q-tracks of the receiving functions, the Moho boundary with a delay time of 4.0 sec is clearly distinguished. Thus, a map of iso-lines of the depths of the Moho surface was constructed and depths were determined for the territory of the Guba-Gusar region 48-50 km, the Zagatala-Balakan region 46-47 km, the Shamakhi-Ismayilli region 48-52 km. As it was said earlier, the first definitions of the depth of the surface of Moho in Azerbaijan were made based on the data from the state earthquake and the gravitational model of the Earth's crust. R.M. Gadzhiev in 1965 and E.Sh. Shikhalibeyli in 1996 built such models. The data obtained are consistent with the available data, but discrepancies have been received. Compared with the map constructed according to the GSZ-KMPV and gravimetric data by R.M. Gadzhiev (1965), the difference in the thickness of the earth's crust was from one to 15 km. Compared with the map constructed according to the FGP and gravimetric data by E.Sh Shikhalibeyli (1996), the difference in the thickness of the earth's crust varied from one to 10 km.
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Minh, Pham Thi, Bui Thi Tuyet, Tran Thi Thu Thao, and Le Thi Thu Hang. "Application of ensemble Kalman filter in WRF model to forecast rainfall on monsoon onset period in South Vietnam." VIETNAM JOURNAL OF EARTH SCIENCES 40, no. 4 (September 18, 2018): 367–94. http://dx.doi.org/10.15625/0866-7187/40/4/13134.
Повний текст джерелаАнотація:
This paper presents some results of rainfall forecast in the monsoon onset period in South Vietnam, with the use of ensemble Kalman filter to assimilate observation data into the initial field of the model. The study of rainfall forecasts are experimented at the time of Southern monsoon outbreaks for 3 years (2005, 2008 and 2009), corresponding to 18 cases. In each case, there are five trials, including satellite wind data assimilation, upper-air sounding data assimilation, mixed data (satellite wind+upper-air sounding data) assimilation and two controlled trials (one single predictive test and one multi-physical ensemble prediction), which is equivalent to 85 forecasts for one trial. Based on the statistical evaluation of 36 samples (18 meteorological stations and 18 trials), the results show that Kalman filter assimilates satellite wind data to forecast well rainfall at 48 hours and 72 hours ranges. With 24 hour forecasting period, upper-air sounding data assimilation and mixed data assimilation experiments predicted better rainfall than non-assimilation tests. The results of the assessment based on the phase prediction indicators also show that the ensemble Kalman filter assimilating satellite wind data and mixed data sets improve the rain forecasting capability of the model at 48 hours and 72 hour ranges, while the upper-air sounding data assimilation test produces satisfactory results at the 72 hour forecast range, and the multi-physical ensemble test predicted good rainfall at 24 hour and 48 hour forecasts. The results of this research initially lead to a new research approach, Kalman Filter Application that assimilates the existing observation data into input data of the model that can improve the quality of rainfall forecast in Southern Vietnam and overall country in general.References Bui Minh Tuan, Nguyen Minh Truong, 2013. 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Soc., 131C, 3269-3289.Hunt B.R., Kostelich E., Szunyogh I., 2007. Efficient data assimilation for spatiotemporal chaos: a local ensemble transform Kalman filter. Physica D., 230, 112-126.Kalnay E., 2003. Atmospheric modeling, data assimilation and predictability. Cambridge University Press, 181.Kalnay et al., 2008. A local ensemble transform Kalman filter data assimilation system for the NCEP global model. Tellus A, 60(1), 113-130.Kato T., Aranami K., 2009. Formation Factors of 2004 Niigata-Fukushima and Fukui Heavy Rainfalls and Problems in the Predictions using a Cloud-Resolving Model. SOLA. 10, doi:10.2151/sola.Kieu C.Q., 2010. Estimation of Model Error in the Kalman Filter by Perturbed Forcing. VNU Journal of Science, Natural Sciences and Technology, 26(3S), 310-316.Kieu C.Q., 2011. Overview of the Ensemble Kalman Filter and Its Application to the Weather Research and Forecasting (WRF) model. VNU Journal of Science, Natural Sciences and Technology, 27(1S), 17-28.Kieu C.Q., Truong N.M., Mai H.T., and Ngo Duc T., 2012. Sensitivity of the Track and Intensity Forecasts of Typhoon Megi (2010) to Satellite-Derived Atmosphere Motion Vectors with the Ensenble Kalman filter. J. Atmos. Oceanic Technol., 29, 1794-1810.Kieu Thi Xin, 2005. Study on large-scale rainfall forecast by modern technology for flood prevention in Vietnam. State-level independent scientific and technological briefing report, 121-151.Kieu Thi Xin, Vu Thanh Hang, Le Duc, Nguyen Manh Linh, 2013. Climate simulation in Vietnam using regional climate nonhydrostatic NHRCM and hydrostatic RegCM models. Vietnam National University, Hanoi. Journal of Natural sciences and technology, 29(2S), 243-25.Krishnamurti T.N., Bounoa L., 1996. An introduction to numerical weather prediction techniques. CRC Press, Boca Raton, FA.Lau K.M., Yang S., 1997. Climatology and interannual variability of the Southeast Asian summer monsoon. Adv. Atmos. Sci., 14,141-162.Li C., Qu X., 1999. Characteristics of Atmospheric Circulation Associated with Summer monsoon onset in the South China Sea. Onset and Evolution of the South China Sea Monsoon and Its Interaction with the Ocean. Ding Yihui, and Li Chongyin, Eds, Chinese Meteorological Press, Beijing, 200-209.Lin N., Smith J.A., Villarini G., Marchok T.P., Baeck M.L., 2010. Modeling Extreme Rainfall, Winds,and Surge from Hurricane Isabel, 25. Doi: 10.1175/2010WAF2222349.Lu J., Zhang Q., Tao S., and Ju J., 2006. The onset and advance of the Asian summer monsoon. Chinese Science Bulletin, 51(1), 80-88.Matsumoto J., 1997. Seasonal transition of summer rainy season over Indochina and adjacent monsoon region. Adv. Atmos. Sci., 14, 231-245.Miyoshi T., and Kunii M., 2012. The Local Ensenble Transform Kalman Filter with the Weather Rearch and Forecasting Model: Experiments with Real Observation. Pure Appl. Geophysic, 169(3), 321-333. Miyoshi T., Yamane S., 2007. Local ensemble transform Kalman filtering with an AGCM at a T159/L48 resolution. Mon. Wea. Rev., 135, 3841-3861.Nguyen Khanh Van, Tong Phuc Tuan, Vuong Van Vu, Nguyen Manh Ha, 2013. The heavy rain differences based on topo-geographical analyse at Coastal Central Region, from Thanh Hoa to Khanh Hoa. J. Sciences of the Earth, 35, 301-309.Nguyen Minh Truong, Bui Minh Tuan, 2013. A case study on summer monsoon onset prediction for southern Vietnam in 2012 using the RAMS model. VNU Journal of Science, 29(1S), 179-186.Phillips N.A., 1960b. Numerical weather prediction. Adv. Computers, 1, 43-91, Kalnay 2004.Phillips N., 1960a. On the problem of the initial data for the primitive equations, Tellus, 12, 121126.Phuong Nguyen Duc, 2013. Experiment on combinatorial Kalman filtering method for WRF model to forecast heavy rain in central region in Vietnam. The Third International MAHASRI/HyARC Workshop on Asian Monsoon and Water Cycle, 28-30 August 2013, Da Nang, Viet Nam, 217-224.Richardson L.F., 1922. Weather prediction by numerical process. Cambridge University Press, Cambridge. Reprinted by Dover (1965, New York).Routray, Mohanty U.C., Niyogi D., Rizvi S.R., Osuri K.K., 2008. First application of 3DVAR-WRF data assimilation for mesoscale simulation of heavy rainfall events over Indian Monsoon region. Journal of the Royal Meteorological Society, 1555.Schumacher, R. S., C. A. Davis, 2010. Ensemble-based Forecast Uncertainty Analysis of Diverse Heavy Rainfall Events, 25. Doi: 10.1175/2010WAF2222378.Snyder C., Zhang F., 2003. Assimilation of simulated Doppler radar observations with an Ensemble Kalman filter. Mon. Wea. Rev., 131, 1663.Szunyogh I., Kostelich E.J., Gyarmati G., Kalnay E., Hunt B.R., Ott E., Satterfield E., Yorke J.A., 2008. A local ensemble transform Kalman filter data assimilation system for the NCEP global model. Tellus A., 60, 113-130.Tanaka M., 1992. Intraseasonal oscillation and the onset and retreat dates of the summer monsoon east, southeast Asia and the western Pacific region using GMS high cloud amount data. J. Meteorol. Soc. Japan, 70, 613-628.Tan Tien Tran, Nguyen Thi Thanh, 2011. The MODIS satellite data assimilation in the WRF model to forecast rainfall in the central region. VNU Journal of Science, Natural Sciences and Technology, 27(3S), 90-95.Tao S., Chen L., 1987. A review of recent research on East summer monsoon in China, Monsoon Meteorology. C. P. Changand T. N. Krishramurti, Eds, Oxford University Press, Oxford, 60-92.Tippett M.K., Anderson J.L., Bishop C.H., Hamill T.M., Whitaker J.S., 2003. Ensemble square root filters. Mon. Wea. Rev., 131, 1485.Thuy Kieu Thi, Giam Nguyen Minh, Dung Dang Van, 2013. Using WRF model to forecast heavy rainfall events on September 2012 in Dong Nai River Basin. 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Sci., 80, 629-638.Webster P.J., Magana V.O., Palmer T.N., Shukla J., Tomas R.A., Yanai M., Yasunari T., 1998. Monsoons: Processes, predictability, and teprospects for prediction, J. Geophys. Res., 103, 14451-14510.Wilks Daniel S., 1997. Statistical Methods in the Atmospheric Sciences. Ithaca New York., 59, 255.Whitaker J.S., Hamill T.M., 2002. Ensemble data assimilation without perturbed observations. Mon. Wea. Rev., 130, 1913.Wu G., Zhang Y., 1998. Tibetan plateau forcing and the timing of the monsoon onset over South Asia and the South China Sea. Mon.Wea.Rev., 126, 913-927.Zhang Z., Chan J.C.L., and Ding Y., 2004. Characteristics, evolution and mechanisms of the summer monsoon onset over Southeast Asia. J.Climatology, 24, 1461-1482.http://weather.uwyo.edu/upperair/sounding.html and http://tropic.ssec.wisc.edu/archive/
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"Design Modifications in RF Interaction Cavity of a 140 GHZ Gyrotron to Achieve Wide Tunable Bandwidth for DNP NMR Applications." International Journal of Engineering and Advanced Technology 9, no. 1 (October 30, 2019): 6456–62. http://dx.doi.org/10.35940/ijeat.a2241.109119.
Повний текст джерелаАнотація:
The tapered RF interaction cavity of 140 GHz tunable continuous wave (CW) gyrotron operating in TE0,3,q mode has been tailored with the aim of providing RF power over a tunable bandwidth for 212 MHz DNP NMR spectroscopy applications. Gyrotron device RF interaction cavity design, its beam absent RF characteristics as well as electron beam and RF wave interaction behavior, both analytical and Particle-in-Cell (PIC) simulation studies have been presented. Using linear analysis, the start oscillation currents and the RF field profiles for the various axial operating modes indices q = 1, 2, 3 have been determined. Suitable modifications in the interaction cavity have been incorporated for the enhancement of device tunable bandwidth by operating the gyrotron in the high order axial indices via magnetic tuning. Gyrotron beam-wave interaction behaviour explored using time dependent non-linear multi-mode analysis for various beam currents and magnetic fields and more than >15W of RF power over a tunable bandwidth of 400MHz has been achieved through magnetic field tuning. This tunable bandwidth gyrotron design will of immense use for enhancement of sensitivity of the DNP NMR spectroscopy.
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Belov, Yu G., V. V. Biryukov, and I. A. Egorov. "Nondestructive method of measurement of laminated plates dielectric parameters." Antennas, 2021. http://dx.doi.org/10.18127/j03209601-202102-11.
Повний текст джерелаАнотація:
The methods for measuring the parameters of dielectric materials of foil plates have been considered. It has been shown that for “non-destructive measurements” (i.e., without removing the metal foil from the dielectric plate), a method based on the excitation of electromagnetic oscillations in a rectangular plate considered as a resonator can be used. Based on the results of measurements of their resonant frequencies and Q-factors, the relative permittivity and the tangent of the dielectric loss angle of the material can be determined. The calculated relations obtained by the authors of the article in one of the early works using the electrodynamic model of a resonator with “magnetic walls” at the ends have been presented. The Q-factor of the resonator has been calculated by the perturbation method, taking into account the losses in the plate dielectric and metallization layers. The results of measurements for four samples from different dielectrics in the frequency range 200...1000 MHz have been presented. The experimental method has been described, in particular, the method of identifying the type of oscillation, the procedure for processing the measurement results. Due to the high sensitivity of the vector analyzer, measurements have been made with a possible small connection of the resonator (metallized plate) with the measuring circuit. This made it possible to minimize the influence of the coupling elements on the measured Qfactor of the oscillations and to consider this Q-factor close to its own. The presented results are in good agreement with the reference data for the materials. The conducted studies have shown the possibility of using a resonator model with “magnetic walls” at the ends for the analysis of electromagnetic oscillations in a foil dielectric plate and, accordingly, using the relations obtained in this case to determine the parameters of the dielectric plate. The conditions for using this model are the small thickness of the plate in comparison with its transverse dimensions and relatively low operating frequencies. The method, which is based on the calculated ratios of the electrodynamic model of the resonator with “magnetic” walls at the ends, provides a sufficiently high accuracy of determining the relative permittivity of the plate material, which led to the use of it (the method) in practice to control the parameters of foil dielectric plates intended for the manufacture of microwave and UHF-band microcircuits. The studies, the results of which have been presented in this paper, allow us to conclude that this method can also be recommended for determining the tangent of the dielectric loss angle of the plate material.
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Yushuang Wang, Xuanxuan Ji, Ziyang Chen, and Jixiong Pu. "Q-switched partially coherent lasers with controllable spatial coherence." Optica Applicata 51, no. 2 (2021). http://dx.doi.org/10.37190/oa210208.
Повний текст джерелаАнотація:
We develop a Q-switched degenerate laser, delivering a partially coherent light pulse of duration about 16 ns. The spatial coherence of the output laser pulse can be varied by tuning the spatial filter inside the laser resonator, and the oscillating transverse mode structure can be determined by measuring the degree of coherence of the output laser pulse. It is shown that the larger is the diameter of the spatial filter, the more are the oscillating transverse modes, and the lower is the degree of coherence. Based on coherent-mode representation for the partially coherent source, we can estimate the transverse mode contribution to the output partially coherent laser. The experimental results on suppressing speckle demonstrate that the generated partially coherent light possesses the characteristics of rapid reduction of spatial coherence, making it an ideal source for high-speed imaging and ranging applications.
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Wang, Zhaodong, Pu Li, and Beibei Sun. "Squeeze-film damping of microbeam and microplate resonators in the free molecular regime." Micro and Nanosystems 14 (February 21, 2022). http://dx.doi.org/10.2174/1876402914666220221113221.
Повний текст джерелаАнотація:
Background: Correct modeling of squeeze-film damping (SFD) is an important consideration in the design of high-Q microresonators. In 2002, using the molecular dynamics (MD) approach, Bao et al. developed an analytical MD model for the evaluation of the SFD of a parallel-plate device in the free molecular regime. Their model was based on the energy exchange between the oscillating plate and gas molecules. Bao’s model is now widely used in microsystem design. However, Bao’s model cannot reduce to the air damping model in free space and is unsuitable for flexible microbeams. Objective: This paper first presents a more accurate analytical model for the evaluation of the SFD of the parallel plate. Then the present analytical model is extended to model the SFD of flexible microbeams with deformed shapes. Methods: This paper is based on the momentum transfer between the vibration plate and gas molecules. Results: The analytical results of the present model have shown a good agreement with the available experimental results. Conclusion: The limitations in the previous model are overcome.
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"Design of On chip Spiral Inductors for Millimeter Wave Frequency Synthesizers." International Journal of Circuits, Systems and Signal Processing 14 (May 25, 2020). http://dx.doi.org/10.46300/9106.2020.14.29.
Повний текст джерелаАнотація:
The energy storing element, inductor plays a vital role in CMOS based high frequency integrated circuits, especially in signal generation and impedance matching blocks.An on chip inductor is considered as a critical component because its performance directly impacts the associated circuitry when it is used as a load device or as a matching element. Out of the various requirements of an inductor which resides inside a chip, the inductance value,quality factor and self resonance frequency with smaller area is often preferred. This paper focuses on the lumped model of inductors for high frequency circuits working in the Millimeter wave region from 30 GHz to 300 GHz. For millimeter wave oscillators,inductance value in the range of pico Henry are essential and hence a complete model of an inductor is presented. Using electromagnetic simulator SONNET, all the parameters are extracted. The extracted model is used in the design of an LC Oscillator for millimeter wave band. A Q factor of 26 is achieved for an inductor value close to 153 pH at 60 GHz.The circuits employing this inductor shows promising results when simulated using 45 nm CMOS pdks