Nonrotational States Research Articles

Vibration Reduction on Circular Disks with Vibroacoustic Metamaterials

Vibroacoustic metamaterials represent an innovative technology developed for broadband vibration reduction. They consist of an array of local resonators and are able to reduce vibrations over a wide frequency range, commonly referred to as a stop band. Vibroacoustic metamaterials may be a promising strategy to reduce out-of-plane vibrations of thin-walled, disk-shaped structures, such as saw blades. However, their behavior in rotating systems has not yet been fully understood. In this study, a vibroacoustic metamaterial integrated into a circular disk for the reduction of out-of-plane vibrations is experimentally investigated in the rotating and non-rotating state. Derived from the predominant frequency range of noise emitted by saw blades, a vibroacoustic metamaterial with a numerically predicted stop band in the frequency range from 2000 Hz to 3000 Hz, suitable for integration into a circular disk, is designed. The resonators of the metamaterial are realized by cutting slots into the disk using a waterjet cutting machine. To experimentally examine the structural dynamic behavior, the disk is excited by an impulse hammer and observed by a stationary optical velocity sensor on a rotor dynamics test stand. The results of the rotating and the non-rotating state are compared. The measurements are carried out at two different radii and at speeds up to 3000 rpm. A distinct stop band characteristic is shown in the desired frequency range from 2000 Hz to 3000 Hz in the rotating and non-rotating state. No significant shift of the stop band frequency range was observed during rotation. However, adjacent modes were observed to propagate into the stop band frequency range. This work contributes to a better understanding of the behavior of vibroacoustic metamaterials in the rotating state and enables future applications of vibroacoustic metamaterials for vibration reduction in rotating, disk-shaped structures such as saw blades, brake disks or gears.

A novel algorithm to the shell model study of heavy deformed nuclei using the variation after projection approach

We introduce an extension to the conventional variation after projection (VAP) method, in which wave functions of different spin states projected from a shared intrinsic wave function are first varied simultaneously. Then a second variation is carried out for each individual state starting from the obtained intrinsic wave function. This novel algorithm enables the efficient extraction of a rotational band from chaotic non-rotational states by adopting only one Slater determinant, which can not be reached by the conventional VAP method. Some examples including the heavy deformed nuclei in the jj56 model space have been calculated. The calculated results show that this new method could be a useful tool to systematically study the collective rotational states in heavy deformed nuclei. Furthermore, the present method holds potential for probing significant correlations, such as octupole correlations, within nuclear structures.

Mistuning identification and model updating of a blisk with piezoelectric excitation components

Integrally bladed disks (blisks) are extensively used in military and commercial aircraft engines. There are inevitable deviations between blades called mistuning, leading to the vibration localization of blisks, which potentially results in high cycle fatigue (HCF). Furthermore, the dynamic performance is sensitive to mistuning patterns. Hence, to predict the vibration response of mistuned blisks accurately, the mistuning pattern needs to be identified experimentally and verified under traveling wave excitation (TWE). Piezoelectric TWE is a promising testing technique for blisk dynamics in a non-rotating state, offering advantages such as high excitation force, wide bandwidth, and a simple setup. However, piezoelectric materials are generally arranged on blades forming an electromechanically coupled structure, which challenges the existing mistuning identification methods. In this paper, an integral mistuning identification and model updating method with traveling wave excitation verification is developed. The detuning strategy is used to split natural frequencies of blades, whereupon the response is measured blade by blade. Measured response functions of isolated blades can be retrieved by data reconstruction. Then, the mistuning patterns of elastic modulus and damping ratio are identified by Kirchhoff-plate theory and half-power bandwidth method, respectively. Experimental studies are carried out to validate the method. A dummy blisk with piezoelectric patches is designed and the dynamic properties are calculated. Blade-by-blade measurement and TWE test are conducted. Results show that natural frequencies of the updated model are in excellent agreement with the measured ones. Under TWE, the deviations of natural frequencies for all blades are less than 0.25%. The response deviation of the updated model is decreased by 89.4% on average compared with the original model and the average response deviation of the updated model is 7.4%.

Experimental investigation of heat transfer in the trapezoidal channel with lateral outflow under rotation conditions

The heat transfer characteristics of wedge-shaped transverse outflow channels with different pin-fins under rotating conditions were measured experimentally. The Reynolds number varies from 10,000 to 70,000, and the rotation number varies from 0 to 0.6. For non-rotating state, the Nussel number decrease along the flow direction on the pin–fin rough surface as inner smooth area, albeit marginally. For rotating state, the enhancement of Nusselt number ratio in the outer pin-fins area is significantly weaker than inner smooth area. The heat transfer of the leading and trailing surfaces shows an increasing trend with the ascend of the rotation number. At the same time, due to the Coriolis force, the heat transfer of the trailing surface is stronger than that of the leading surface. Results show that the total heat transfer of the four experimental models intensify with the increase of the total cross-sectional area of the pin-fins. In particular, the total cross-sectional area of pin fin is increased by 3 times, and the heat transfer of channel can be strengthened by 46–77%. The effective method to increase the total cross-sectional areas of the pin fins is to increase their diameters.

Conformational dynamics of eukaryotic translation.

The ribosome is a molecular machine that adopts multiple conformations during translation. The body of the small ribosomal subunit rotates relatively to the large ribosomal subunit by about 9 degrees. This movement reconfigures tRNA binding sites, which results in a partial movement of tRNAs on the ribosome. At the beginning of the elongation cycle, the ribosome awaits A-site decoding and occupies the non-rotated conformation. Upon A-site tRNA binding, the ribosome rapidly catalyzes peptidyl transfer. It is followed by counterclockwise rotations of the small ribosomal subunit that puts the ribosome into the rotated state. The resultant pre-translocation complex is dynamic and exchanges between rotated and non-rotated conformations. Eukaryotic elongation factor 2 (eEF2) catalyzes translocation, which moves tRNA-mRNA and resets the ribosome into the non-rotated state. Despite extensive biochemical and structural studies, the underlying mechanism of translation elongation remains elusive. We developed a single-molecule fluorescence resonance energy transfer (smFRET) system that allows the observation of intersubunit conformational change of yeast ribosomes in real-time. We followed the ribosome conformational change in pre- and post-translocation ribosome complexes. To interrogate the mechanism of translocation, we applied antifungal sordarin. Sordarin stabilizes eEF2 on the ribosome after GTP hydrolysis and phosphate release. Our results suggest that in the presence of sordarin, the mid and late stages of translocation are thermally driven.

Experimental and Numerical Study of Heat Transfer and Turbulent Flow in a Rotating channel with V Rib-Dimple Hybrid Structures

Heat transfer and turbulent flow structure of novel hybrid structures with V rib-dimple arrays in channels with a sudden contraction have been investigated through experimental and numerical studies for the Reynolds number (Re) from 10,000 to 200,000 and Rotation number (Ro) from 0 to 0.413, which are also compared with those of a smooth and a dimpled only channel. For rotating smooth channels, sudden contraction can significantly enhance heat transfer in the entrance region for the first 4 times Dh of the channel, and heat transfer rates for trailing and leading walls are higher compared with those of static channels. For the rotating V rib-dimple channel at Re = 10,000, heat transfer rates of the trailing wall significantly increase by about 39.13% at Ro = 0.413 compared with those under the non-rotating state, which is because the longitudinal vortex on the trailing side becomes stronger with the actions of the Coriolis force produced by the rotation, thus significantly enhancing heat transfer there. It is also noted that strong longitudinal vortex pairs from inside the dimples of the V rib-dimple structure can partially offset influences of the rotation effects. Therefore, the maximum heat transfer difference between leading and trailing sides of rotating V rib-dimple channels is just 22.57%, which is much smaller than the difference of 107.25% of the rotating dimpled only channel.

Analysis of a Novel Mechanically Adjusted Variable Flux Permanent Magnet Homopolar Inductor Machine with Rotating Magnetic Poles for Flywheel Energy Storage System

Permanent magnet homopolar inductor machine (PMHIM) has attracted much attention in the field of flywheel energy storage system (FESS) due to its merits of simple structure, brushless excitation, and rotor flywheel integration. However, the air-gap flux generated by the PM cannot be adjusted, which would cause large electromagnetic losses in the standby operation state of FESS. To solve this problem, a novel mechanically adjusted variable flux permanent magnet homopolar inductor machine with rotating magnetic poles (RMP-PMHIM) is proposed in this paper. The permanent magnet poles are rotated by an auxiliary rotating device and the purpose of changing the air-gap flux is achieved. First, the structure and operation principle of the proposed RMP-PMHIM are explained. Second, the flux weakening principle of the RMP-PMHIM is analyzed and the equivalent magnetic circuit models under different flux weakening states are built. Third, the parameters of the PM and its fixed structure are optimized to obtain the good electromagnetic performance. Fourth, the electromagnetic performance, including the air-gap flux density, back-EMF, flux weakening ability, loss, etc. of the proposed RMP-PMHIM are investigated and compared. Compared with the non-rotating state of the PM of RPM-PMHIM, the air-gap flux density amplitude can be weakened by 99.95% when the PM rotation angle is 90 degrees, and the no-load core loss can be suppressed by 99.98%, which shows that the proposed RPM-PMHIM is a good candidate for the application of FESS.

Nonlinear forced transient response of rotating ring on the elastic foundation by using adaptive ANCF curved beam element

Based on the Euler-Bernoulli beam theory, nonlinear axial Lagrangian strain and simplified curvature, the nonlinear differential equations of motion for rotating ring on the elastic foundation (RREF) are established by absolute nodal coordinate formulation curved beam element. In non-rotating state, the double modes at the same frequency are observed. In rotating state, the first-order critical angular speed, the frequency of forward traveling wave and backward traveling wave are obtained. Then, the nonlinear forced transient response (radial deformation rate) of the RRE under the action of concentrated load at bottom point is analyzed. In order to improve computational efficiency, the adaptive ANCF curved beam element is proposed, and reasonable range of two key parameters, i.e., element length and rotation angle of adjacent nodal tangential vector are determined. And it is used to analysis the influences of internal pressure, radial and tangential elastic support stiffness, and Young's modulus on nonlinear transient response characteristics of RREF. In order to study the standing wave phenomenon for a period, the RREF-hub contact model is established and used to analyze the nonlinear transient response of RREF at the first-order critical angular speed.

Annealing synchronizes the 70S ribosome into a minimum-energy conformation

Researchers commonly anneal metals, alloys, and semiconductors to repair defects and improve microstructures via recrystallization. Theoretical studies indicate that simulated annealing on biological macromolecules helps predict the final structures with minimum free energy. Experimental validation of this homogenizing effect and further exploration of its applications are fascinating scientific questions that remain elusive. Here, we chose the apo-state 70S ribosome from Escherichia coli as a model, wherein the 30S subunit undergoes a thermally driven intersubunit rotation and exhibits substantial structural flexibility as well as distinct free energy. We experimentally demonstrate that annealing at a fast cooling rate enhances the 70S ribosome homogeneity and improves local resolution on the 30S subunit. After annealing, the 70S ribosome is in a nonrotated state with respect to corresponding intermediate structures in unannealed or heated ribosomes. Manifold-based analysis further indicates that the annealed 70S ribosome takes a narrow conformational distribution and exhibits a minimum-energy state in the free-energy landscape. Our experimental results offer a facile yet robust approach to enhance protein stability, which is ideal for high-resolution cryogenic electron microscopy. Beyond structure determination, annealing shows great potential for synchronizing proteins on a single-molecule level and can be extended to study protein folding and explore conformational and energy landscapes.

Holographic and QFT complexity with angular momentum

We study the influence of angular momentum on quantum complexity for CFT states holographically dual to rotating black holes. Using the holographic complexity=action (CA) and complexity=volume (CV) proposals, we study the full time dependence of complexity and the complexity of formation for two dimensional states dual to rotating BTZ. The obtained results and their dependence on angular momentum turn out to be analogous to those of charged states dual to Reissner-Nordström AdS black holes. For CA, our computation carefully accounts for the counterterm in the gravity action, which was not included in previous analysis in the literature. This affects the complexity early time dependence and its effect becomes negligible close to extremality. In the grand canonical ensemble, the CA and CV complexity of formation are linear in the temperature, and diverge with the same structure in the speed of light angular velocity limit. For CA the inclusion of the counterterm is crucial for both effects. We also address the problem of studying holographic complexity for higher dimensional rotating black holes, focusing on the four dimensional Kerr-AdS case. Carefully taking into account all ingredients, we show that the late time limit of the CA growth rate saturates the expected bound, and find the CV complexity of formation of large black holes diverges in the critical angular velocity limit. Our holographic analysis is complemented by the study of circuit complexity in a two dimensional free scalar model for a thermofield double (TFD) state with angular momentum. We show how this can be given a description in terms of non-rotating TFD states introducing mode-by-mode effective temperatures and times. We comment on the similarities and differences of the holographic and QFT complexity results.

Dynamical evolution study of exciton–polariton Bose–Einstein condensate with vortex manipulation

For the exciton–polariton BEC system modulated by vortex light, we study its evolution based on the driven-dissipative Gross–Pitaevskii equation model. Via modified variational method, we first derive the two-dimensional system’s evolution pattern from the initially coherent state prepared by vortex light modulation for non-rotating states and rotating states with various angular velocities. We identify close qualitatively matched patterns by comparing our theoretically derived evolution patterns with that from pure numerical simulation, demonstrating the applicability of our theoretical treatment presented. The derived exciton–polariton evolution pattern formulation can then be used to guide experimental observations of vortex manipulation effects for the exciton–polariton BEC system, with the possible identification of quantum gyroscopic effects.

New solutions for rotating boson stars

It has been shown that scalar fields can form gravitationally bound compact objects called boson stars. In this study, we analyze boson star configurations where the scalar fields contain a small amount of angular momentum and find two new classes of solutions. In the first case all particles are in the same slowly rotating state, and in the second case the majority of particles are in the nonrotating ground state and a small number of particles are in an excited rotating state. In both cases, we solve the underlying Gross-Pitaevskii-Poisson equations that describe the profile of these compact objects both numerically as well as analytically through series expansions.

Structure of Gcn1 bound to stalled and colliding 80S ribosomes

The Gcn pathway is conserved in all eukaryotes, including mammals such as humans, where it is a crucial part of the integrated stress response (ISR). Gcn1 serves as an essential effector protein for the kinase Gcn2, which in turn is activated by stalled ribosomes, leading to phosphorylation of eIF2 and a subsequent global repression of translation. The fine-tuning of this adaptive response is performed by the Rbg2/Gir2 complex, a negative regulator of Gcn2. Despite the wealth of available biochemical data, information on structures of Gcn proteins on the ribosome has remained elusive. Here we present a cryo-electron microscopy structure of the yeast Gcn1 protein in complex with stalled and colliding 80S ribosomes. Gcn1 interacts with both 80S ribosomes within the disome, such that the Gcn1 HEAT repeats span from the P-stalk region on the colliding ribosome to the P-stalk and the A-site region of the lead ribosome. The lead ribosome is stalled in a nonrotated state with peptidyl-tRNA in the A-site, uncharged tRNA in the P-site, eIF5A in the E-site, and Rbg2/Gir2 in the A-site factor binding region. By contrast, the colliding ribosome adopts a rotated state with peptidyl-tRNA in a hybrid A/P-site, uncharged-tRNA in the P/E-site, and Mbf1 bound adjacent to the mRNA entry channel on the 40S subunit. Collectively, our findings reveal the interaction mode of the Gcn2-activating protein Gcn1 with colliding ribosomes and provide insight into the regulation of Gcn2 activation. The binding of Gcn1 to a disome has important implications not only for the Gcn2-activated ISR, but also for the general ribosome-associated quality control pathways.

Parameter Identification of a Strongly Nonlinear Rotor-Bearing System Based on Reconstructed Constant Response Tests

Abstract A strongly nonlinear rotor-bearing system often has multiple solutions under harmonic excitations and jump phenomena. For example, a hardening nonlinearity may include a jump-down in the acceleration process and jump-up in the deceleration process. It is challenging to measure all of these multiple responses and establish an accurate dynamic model from experimental data to predict these phenomena. This paper used a fixed frequency test method to measure all of these multiple responses under harmonic excitations and developed a novel strategy to characterize and identify nonlinearities in a strongly nonlinear rotor-bearing system based on reconstructing constant response tests from fixed frequency test data. The fixed frequency tests are achieved by monotonically increasing the voltage applied to the exciter at a fixed frequency and using the force drop-out phenomenon through the resonance to control the force applied to the structure. This test method could measure multivalued response curves of a strongly nonlinear rotor-bearing system in a nonrotating state. The constant response tests could be reconstructed from these multivalued response curves. The relationship of equivalent stiffness versus displacement can be established, and hence, the nonlinear stiffness is characterized and identified from constant response tests. A rotor-bearing system with a strongly nonlinear support is used to demonstrate the method, and the nonlinear support stiffness parameters are identified and validated in a nonrotating state. The identified nonlinear rotor-bearing model also could predict the jump phenomena in the acceleration or deceleration process. The results demonstrate the feasibility and effectiveness of the approach, and also show the potential for practical applications in engineering.

Structure and function of yeast Lso2 and human CCDC124 bound to hibernating ribosomes.

Cells adjust to nutrient deprivation by reversible translational shutdown. This is accompanied by maintaining inactive ribosomes in a hibernation state, in which they are bound by proteins with inhibitory and protective functions. In eukaryotes, such a function was attributed to suppressor of target of Myb protein 1 (Stm1; SERPINE1 mRNA-binding protein 1 [SERBP1] in mammals), and recently, late-annotated short open reading frame 2 (Lso2; coiled-coil domain containing short open reading frame 124 [CCDC124] in mammals) was found to be involved in translational recovery after starvation from stationary phase. Here, we present cryo-electron microscopy (cryo-EM) structures of translationally inactive yeast and human ribosomes. We found Lso2/CCDC124 accumulating on idle ribosomes in the nonrotated state, in contrast to Stm1/SERBP1-bound ribosomes, which display a rotated state. Lso2/CCDC124 bridges the decoding sites of the small with the GTPase activating center (GAC) of the large subunit. This position allows accommodation of the duplication of multilocus region 34 protein (Dom34)-dependent ribosome recycling system, which splits Lso2-containing, but not Stm1-containing, ribosomes. We propose a model in which Lso2 facilitates rapid translation reactivation by stabilizing the recycling-competent state of inactive ribosomes.

Heat transfer characteristics in a rotating wedge-shaped ribbed trailing edge with impingement jet

ABSTRACT The effect of impingement jet on heat transfer in a rotating wedge-shaped ribbed trailing edge was experimentally investigated in this study. The inlet Reynolds number varied from 10000 to 61000, and rotation number from 0.06 to 0.16. Four different impingement structures (angle, diameter and number of impingement jet holes) were selected for investigation in non-rotating state, whereas the basic model structure was explored under rotation state. The heat transfer inside the channel and at the slots was analyzed in detail. The results show that the heat transfer at the leading edge of L-after jet region (the impingement surface) is significantly stronger than that of T-after jet region. Variation of impingement structures has altered the jet Reynolds number. Specifically, when the hole diameter narrowed, the jet Reynolds number increased by 30%, and the heat transfer of L-after jet by 10%. As the number of holes increased, the distribution of mass flow was uneven. When trailing edge acted as the impingement target surface, the heat transfer of trailing edge surface was close to that of the leading edge surface. The effect of rotation on heat transfer was concentrated on inlet region and high-radius region. Enhancement of inlet region led to reduction of other positions (especially for high-radius regions).

Effects of Thermal Annealing and Selective Chemical Etching on Structural and Optical Properties of GaAsBi Epilayer with Droplet Systems.

A GaAs1-xBix layer was grown by molecular beam epitaxy (MBE) with a low Bi content (2.3%) on GaAs maintaining the substrate at a non-rotating state and was then annealed at 750 °C, 800 °C and 850 °C. Each sample that was covered with droplets was investigated by using the Atomic Force Microscopy (AFM), Electrostatic Force Microscopy (EFM) and Photoluminescence (PL) techniques. The surface properties of the GaAs1-xBix layer were investigated by AFM and observed to have a droplet system, which was composed of a donut and a tail. The optical quality of the samples was enhanced after thermal annealing up to 800 °C, and the maximum PL intensity was obtained at 750 °C. AFM images revealed that the shape of the droplet and tail changed with increasing annealing temperature. EFM images revealed a phase separation on the surface droplet system. To explore the nature of the droplets, previously claimed to be made of Ga and/or Bi, and their effect on PL spectrum, a chemical etch procedure was carried out by using diluted solutions of H₂SO₄ and/or HCl. We showed that droplets may be efficiently removed from the surface, and PL intensity could be improved by using a proper sequence of chemical etching procedures. Furthermore, the presence of two different phases for the droplet-system observed by EFM was also confirmed by the selective etching procedure.

Non-rotational States in Isotonic Chains of Heavy Nuclei

Non-rotational States in Isotonic Chains of Heavy Nuclei

Nonrotational states in isotonic chains of heavy nuclei

The ground-state deformations of heavy nuclei are explored with the microscopic-macroscopic approach using the single-particle Woods-Saxon potential of the quasiparticle-phonon model. The calculations of the energies of low-lying nonrotational states take into account the residual pairing and phonon-quasiparticle interactions. The spectra of these states are presented for the $N=147--161$ isotones. The sensitivity of the calculated results to the parameters of the model is studied. A rather good description of the available experimental data is demonstrated.

Operative Binding of Class I Release Factors and YaeJ Stabilizes the Ribosome in the Nonrotated State.

During translation, the small subunit of the ribosome rotates with respect to the large subunit primarily between two states as mRNA is being translated into a protein. At the termination of bacterial translation, class I release factors (RFs) bind to a stop codon in the A-site and catalyze the release of the peptide chain from the ribosome. Periodically, mRNA is truncated prematurely, and the translating ribosome stalls at the end of the mRNA forming a nonstop complex requiring one of several ribosome rescue factors to intervene. One factor, YaeJ, is structurally homologous with the catalytic region of RFs but differs by binding to the ribosome directly through its C-terminal tail. Structures of the ribosome show that the ribosome adopts the nonrotated state conformation when these factors are bound. However, these studies do not elucidate the influence of binding to cognate or noncognate codons on the dynamics of intersubunit rotation. Here, we investigate the effects of wild-type and mutant forms of RF1, RF2, and YaeJ binding on ribosome intersubunit rotation using single-molecule Förster resonance energy transfer. We show that both RF1 binding and RF2 binding are sufficient to shift the population of posthydrolysis ribosome complexes from primarily the rotated to the nonrotated state only when a cognate stop codon is present in the A-site. Similarly, YaeJ binding stabilizes nonstop ribosomal complexes in the nonrotated state. Along with previous studies, these results are consistent with the idea that directed conformational changes and binding of subsequent factors to the ribosome are requisite for efficient termination and ribosome recycling.