Extra Mode Research Articles

Structural Health Monitoring of Steel Frame Structure by Experimental Modal Parameter Identification

Structural health monitoring (SHM) is a modern technique f or damage identification in the e xis ting structure. The structural stiffness, frequency, damping, and dominant mode shapes represent the actual operating conditions of the structure. The main principle of structural health monitoring is to identif y the mod al parameters from experime ntal resu lts both damaged and undamaged conditions. Damage is much effective to decrease stiffness and strength of structural components and it changes dynamic behaviour and damping ratio of whole structures. Bruel & Kjaer experi mental modal analys is technique is r ecently used for civil engineering structures for modal parameters estimation. The paper describes the initial structural health monitoring of a steel frame . The modal parameters were estimated for undamaged condition s a nd these result s are verified and up dated by the numerical FEM tool SAP2000. For the undamaged structure , mode shapes and frequencies were calibrated properly. In the second step, damaged was initiated by dismantling one element from the lower part of the frame. The estimat ed m odal parameter s were compared to the initial one. The mode shapes and frequencies are quite different for some specific mode due to damage initiation . One extra mode was created for the damaged frame due to damage initiation. The 4 th mode was not found f or the initial m easurement because of presence of lower beam. Lower beam restraints the 4 th mode and the frame behaves more flexible. Keywords: SHM , Modal parameters, FEM modelling, Damage characterization, Experimental mo dal analysis (EMA) .

A wideband and multi-mode metasurface antenna with gain enhancement

A metasurface radiator composed of nonuniform patches with gain improvement is proposed in this paper. On the center of the ground plane, an anomalous slot is etched to feed the antenna by a microstrip line. Along the slotline resonate, two uniform slot stubs are added symmetrically near the nulls of the electric field. And an extra radiation mode is introduced. Then, through merging with the full-wavelength provided by the initial slot, a wideband slot antenna with two resonances is obtained. The operating bandwidth is broadened from 17.8% to 27.2%. Besides, nonuniform patches are introduced to modify the gain of the antenna with 1.5 dBi. A 2 × 2 array is fabricated to validate the design, and the whole dimension is 2.26λ0 × 2.26λ0 × 0.08λ0. The simulated and measured results exhibit that the impedance bandwidth is 43.3% and the gain is 13.4–17.6 dBi during the operating band.

An Error Amplifier With a Low Power Multi-Mode Voltage Clamper for Transient Enhancement and High Reliability

This paper proposes a low power area-efficient multi-mode voltage clamper circuit called pseudo differential pair and applies it into an error amplifier (EA) which can be used in DC-DC converters as a practical design example. In addition to a normal amplifying mode, the error amplifier has two extra operation modes with the help of the voltage clamper, which can limit the maximum output voltage and the maximum sink current, respectively. By inserting this pseudo differential pair of only three transistors in the intermediate stage of the amplifier, a voltage-current feedback is introduced to achieve the voltage limiting function without bringing resistive load to the output stage or unwanted effects to the input stage. The frequency compensation of the EA is also reused in the voltage limiting loop to make the whole block more compact. The circuit is implemented in a $0.35~\mu \text{m}$ BCD process. The verification results match the theoretical analysis very well, which proves that the proposed voltage clamper can effectively enhance transient response of the converter control loop and improve system reliability. Only additional 0.001689 mm2 active area is occupied for about 2X transient speed improvement with fair open loop amplifying performance.

The Hamiltonian dynamics of Ho\u0159ava gravity

We consider the Hamiltonian formulation of Hořava gravity in arbitrary dimensions, which has been proposed as a renormalizable gravity model for quantum gravity without the ghost problem. We study the full constraint analysis of the non-projectable Hořava gravity whose potential, mathcal{V}(R), is an arbitrary function of the (intrinsic) Ricci scalar R but without the extension terms which depend on the proper acceleration a_i. We find that there exist generally three distinct cases of this theory, A, B, and C, depending on (i) whether the Hamiltonian constraint generates new (second-class) constraints or just fixes the associated Lagrange multipliers, or (ii) whether the IR Lorentz-deformation parameter {lambda } is at the conformal point or not. It is found that, for Cases A and C, the dynamical degrees of freedom are the same as in general relativity, while, for Case B, there is one additional phase-space degree of freedom, representing an extra (odd) scalar graviton mode. This would achieve the dynamical consistency of a restricted model at the fully non-linear level and be a positive result in resolving the long-standing debates about the extra graviton modes of the Hořava gravity. Several exact solutions are also studied as some explicit examples of the new constraints. The structure of the newly obtained, “extended” constraint algebra seems to be generic to Hořava gravity and its general proof would be a challenging problem. Some other challenging problems, which include the path integral quantization and the Dirac bracket quantization are discussed also.

Ultrafast laser induced precessional dynamics in antiferromagnetically coupled ferromagnetic thin films

Antiferromagnetically coupled ferromagnetic thin films have recently attracted significant attention in magnonics because of the possibility to tune the spin-wave dispersion by altering the interlayer exchange coupling. To implement such coupled films in magnonic devices, a detailed understanding of the precessional dynamics of magnetization in such systems is required. Here, we present a systematic characterization of the precessional dynamics for systems with the layer magnetization going from nearly antiparallel to parallel alignment in a magnetic field. Experimentally, we have measured the ultrafast-laser-induced magnetization precession in samples with different interlayer exchange coupling strengths using the time-resolved magneto-optical Kerr effect. In our measurements, in addition to the acoustic and optical modes, an extra mode is observed that is due to the laser-induced decoupling of the two ferromagnetic layers. The observed precessional dynamics is in good agreement with our theoretical model based on the Landau-Lifshitz-Gilbert equation, and can be separated into three different field regions determined by the relationship between the Zeeman energy and the energy associated with the interlayer exchange coupling. This systematic paper, which gives a detailed description of how the interlayer exchange coupling and Zeeman energy influence the precessional dynamics, provides an important guide to implement antiferromagnetically coupled films in functional magnonic devices.

Boson peak in ultrathin alumina layers investigated with neutron spectroscopy

Bulk glasses exhibit extra vibrational modes at low energies, known as the boson peak. The microscopic dynamics in nanoscale alumina impact the performance of qubits and other superconducting devices, however the existence of the boson peak in these glasses has not been previously measured. Here we report neutron spectroscopy on Al/Al$_2$O$_{3-x}$ nanoparticles consisting of spherical metallic cores from 20 to 1000 nm surrounded by a 3.5 nm thick alumina glass. An intense low-energy peak is observed at $\omega_{BP}$ = 2.8 $\pm$ 0.6 meV for highly oxidised particles, concurrent with an excess in the density of states. The intensity of the peak scales inversely with particle size and oxide fraction indicating a surface origin, and is red-shifted by 3 meV with respect to the van-Hove singularity of $\gamma$-phase Al$_2$O$_{3-x}$ nanocrystals. Molecular dynamics simulations of $\alpha$-Al$_2$O$_{3-x}$, $\gamma$-Al$_2$O$_{3-x}$ and a-Al$_2$O$_{3-x}$ show that the observed boson peak is a signature of the ultrathin glass surface, and the frequency is softened compared to that of the hypothetical bulk glass.

Overtones or higher harmonics? Prospects for testing the no-hair theorem with gravitational wave detections

In light of the current (and future) gravitational wave detections, more sensitive tests of general relativity can be devised. Black hole spectroscopy has long been proposed as a way to test the no-hair theorem, that is, how closely an astrophysical black hole can be described by the Kerr geometry. We use simulations from the Simulating eXtreme Spacetimes project to assess the detectability of one extra quasinormal mode in the ringdown of a binary black hole coalescence, with numbers $(\ell,m,n)$ distinct from the fundamental quadrupolar mode (2,2,0). Our approach uses the complex waveform as well as the time derivative of the phase in two prescriptions that allow us to estimate the point at which the ringdown is best described by a single mode or by a sum of two modes. By scaling all amplitudes to $t_{\rm peak}+10M$, our results for non-spinning binaries indicate that for mass ratios of 1:1 to 5:1 the first overtone (2,2,1) will always have a larger excitation amplitude than the fundamental modes of other harmonics, making it a more promising candidate for detection. Even though the (2,2,1) mode damps about three times faster than the higher harmonics and its frequency is very close to that of the (2,2,0) mode, its larger excitation amplitude still guarantees a more favorable scenario for detection. In particular, for equal-mass binaries the ratio of the amplitude of the first overtone (2,2,1) to the fundamental mode (2,2,0) will be $> 0.65$, whereas the corresponding ratio for the higher harmonics will be $< 0.05$. For binaries with mass ratios larger than 5:1 we find that the modes (2,2,1), (2,1,0) and (3,3,0) should have comparable amplitude ratios in the range 0.3 - 0.4. The expectation that the (2,2,1) mode should be more easily detectable than the (3,3,0) mode is confirmed with an extension of the mode resolvability analysis for larger mass ratios.

Probing cosmological fields with gravitational wave oscillations

Gravitational wave (GW) oscillations occur whenever there are additional tensor modes interacting with the perturbations of the metric coupled to matter. These extra modes can arise from new spin-2 fields (as in e.g. bigravity theories) or from non-trivial realizations of the cosmological principle induced by background vector fields with internal symmetries (e.g. Yang-Mills, gaugids or multi-Proca). We develop a general cosmological framework to study such novel features due to oscillations. The evolution of the two tensor modes is described by a linear system of coupled second order differential equations exhibiting friction, velocity, chirality and mass mixing. We follow appropriate schemes to obtain approximate solutions for the evolution of both modes and show the corresponding phenomenology for different mixings. Observational signatures include modulations of the wave-form, oscillations of the GW luminosity distance, anomalous GW speed and chirality. We discuss the prospects of observing these effects with present and future GW observatories such as LIGO/VIRGO and LISA.

A Compact Single-Layer Wideband Microstrip Antenna With Filtering Performance

A compact single-layer filtering microstrip antenna with diverse characteristics of low profile, high gain, wide band, and high selectivity is proposed in this letter. Simple structure as it is, the presented antenna mainly consists of a rectangle driven patch, four parasitic strips, a pair of symbiotic strips, and a set of shorting pins. By attaching four parasitic strips to the original rectangular patch antenna, an additional resonance can be excited while the high-band edge selectivity is greatly improved due to the formation of a radiation null outside. Then, two symbiotic strips are embedded on both sides of the driven patch, which in turn creates an extra resonance mode and a lower-band radiation null. The set of shorting pins are applied to further improve operating and filtering response. Finally, the use of two parasitic patches can effectively improve the level of impedance bandwidth (IBW) and upper-band suppression. To verify this design, the corresponding antenna is fabricated and tested. The measured and simulated results are highly consistent, which reveals that it owns a wide IBW of 20.1% (2.19-2.68 GHz) with three resonance points, a higher average gain larger than 9.5 dBi, and a flat radiation efficiency above 88% in-band. The suppression level of the out-of-band gain on both sides can reach 14.5 dB.

Stress Relaxation above and below the Jamming Transition.

We numerically investigate stress relaxation in soft athermal disks to reveal critical slowing down when the system approaches the jamming point. The exponents describing the divergence of the relaxation time differ dramatically depending on whether the transition is approached from the jammed or unjammed phase. This contrasts sharply with conventional dynamic critical scaling scenarios, where a single exponent characterizes both sides. We explain this surprising difference in terms of the vibrational density of states, which is a key ingredient of linear viscoelastic theory. The vibrational density of states exhibits an extra slow mode that emerges below jamming, which we utilize to demonstrate the anomalous exponent below jamming.

Compact coaxial slotted‐cavity feed antenna with shaped‐beam pattern for high‐power microwave using high‐order modes and polarisation cancellation techniques

The coaxial slotted-cavity antenna is an easily-manufactured, novel high-power microwave antenna developed specifically for its compact and shaped-beam characteristics. It can directly cascade with the high-power microwave source, and radiate linear-polarisation electromagnetic wave without extra power dividers and mode converters, which obtains a low profile. In this study, a double-layer coaxial cavity operating in two high-order modes is introduced to eliminate the high-order interference modes caused by structural discontinuities, and three shaped beams on the compact aperture can be achieved by the polarisation cancellation technique. Unique proprieties of three shaped beams, namely the peak of gain enhancement beam, the ripple of Gaussian beam and the null depth of conical beam are investigated, all of which can be controlled by the rotation angle of three phase adjusted slot pairs. This study demonstrates the design process of such antenna, and verifies it against simulation and experimental results. The measured return-loss of all three shaped beams are higher than 13 dB, while the corresponding radiation efficiencies are not lower than 98.9%. Furthermore, the estimated minimum power capacity of such antenna exceeds 1.26 GW at 9.375 GHz, making it a highly potential candidate in application towards high-power microwave.

Collective modes of plasma formed by multiphoton ionization of rarefied gas

High-frequency collective modes in plasma with strongly anisotropic velocity distribution of photoelectrons formed by multiphoton or above-threshold ionization of gas atoms are studied. In the case of multiphoton ionization, along with the usual electromagnetic wave, there are two additional modes. In the region of large wavelengths, the higher-frequency mode is similar to the electron Langmuir wave. Its group velocity is mainly determined by the average photoelectron velocity, and Cherenkov damping is due to small velocity dispersion of photoelectron distribution. In the region of short waves, but with a small Cherenkov damping, the group and phase velocities of this wave are close to the average electron velocity. The second mode, which has lower frequency, in the region of wavelengths smaller than the ratio of average electron velocity to the plasma frequency, corresponds to quasi-potential wave. Its dispersion law is close to the linear one. In contrast, in the region of large wavelengths, this mode corresponds to aperiodic instability, the maximum growth rate of which is comparable to the plasma frequency. The distribution of photoelectrons formed during above-threshold ionization is characterized by the large number of energy peaks, which is accompanied by increasing in the number of collective modes. In particular, in plasma with photoelectron distribution which has two energy peaks, in addition to the electromagnetic mode four extra modes are possible. In the shortwave region, all four modes correspond to the waves that are damped due to Cherenkov interaction with photoelectrons. Two of these modes in the region of relatively long wavelengths are unstable. One of these unstable modes corresponds to quasi-potential wave whose amplitude aperiodically increases with time. The reason for the instabilities is the presence of counter streams of photoelectrons.

Constraining Screened Modified Gravity with Spaceborne Gravitational-wave Detectors

Abstract Screened modified gravity (SMG) is a unified theoretical framework that describes scalar–tensor gravity with a screening mechanism. Based on the gravitational-wave (GW) waveform derived in our previous work, in this article we investigate the potential constraints on SMG theory through GW observation by future spaceborne GW detectors, including the Laser Interferometer Space Antenna (LISA), TianQin, and Taiji. We find that, for the extreme-mass-ratio inspirals (EMRIs) consisting of a massive black hole and a neutron star, if the EMRIs are at the Virgo cluster, the GW signals can be detected by the detectors at quite high significance level, and the screened parameter ϵ NS can be constrained at about , which is more than one order of magnitude tighter than the potential constraint given by a ground-based Einstein telescope. However, for the EMRIs consisting of a massive black hole and a white dwarf, it is more difficult to detect them than in the previous case. For the specific SMG models, including chameleon, symmetron, and dilaton, we find these constraints are complementary to that from the Cassini experiment, but weaker than those from lunar laser ranging observations and binary pulsars, due to the strong gravitational potentials on the surface of neutron stars. By analyzing the deviation of the GW waveform in SMG from that in general relativity, as anticipated, we find the dominant contribution of the SMG constraint comes from the correction terms in the GW phases, rather than the extra polarization modes or the correction terms in the GW amplitudes.

Pharmacophore-guided fragment-based design of novel mammalian target of rapamycin inhibitors: extra precision docking, fingerprint-based 2D and atom-based 3D-QSAR modelling

Rapamycin and their derivatives known as rapalogs were the first-generation mTOR inhibitors which interacted with mTORC1 but not with the mTORC2 protein. Second-generation inhibitors could bind with both and showed excellent anti-proliferative activity. Our aim was to design novel mTOR inhibitors which could bind at both the allosteric and the kinase site. The FRB domain is present in both the mTORC1 and mTORC2 protein complexes. We have employed e-pharmacophore-guided fragment-based design to develop novel mTOR inhibitors. The affinity of designed molecules at both the sites was analysed using molecular docking in extra precision mode. The atom-based 3D-QSAR model was developed to predict the activity while the fingerprint-based 2D-QSAR model was employed to refine an identified hit as potent dual mTOR inhibitor. Ligand ASK23 showed a docking score of −15.452 kcal/mol at the allosteric site (PDB ID 5GPG) while ASK38 showed a docking score of −11.535 kcal/mol at the kinase site (PDB ID 4JT6). Ligand ASK12 showed binding energy of −106.23 kcal/mol at the allosteric site. Refined molecule ASK12a from ASK12 showed the highest predicted activity (pIC50: 6.512). The stability of the best hits and receptor complex was analysed using molecular dynamics simulation studies. Herein we report five potential mTOR dual inhibitors based on the predicted activity, drug-likeness analysis and off-target effects. To the best of our knowledge, this is the first report on pharmacophore-guided fragment-based drug design for mTOR inhibitors. This design strategy can be used for the rational drug design against other proteins for which only apo-structures are available. Communicated by Ramaswamy H. Sarma

Fabricating C and O co-doped carbon nitride with intramolecular donor-acceptor systems for efficient photoreduction of CO2 to CO

Photocatalytic reduction of CO2 to hydrocarbon fuels is an ultimate and utmost strategy to resolve the ever-increasing environmental problems and energy crisis. Our study aimed to develop a specific type of photocatalysts with increasing light utilization efficiency, reducing electron-hole recombination rate and enhancing photocatalytic activity by integrating unique donor-acceptor systems into the polymeric network of graphitic carbon nitride (g-CN). The results of the characterization showed that C and O are successfully integrated into the framework of g-CN. The O-containing and C-containing section of the as-prepared catalysts (OCCNx) play the role of donor and acceptor, respectively. The donor-acceptor systems of OCCNx offer an extra electron transfer transition mode, which dramatically extends the optical absorption range, and narrows down the bandgap of g-CN from 2.74 to 2.03 eV. Also, the donor-acceptor systems significantly improve the delocalized ability of the photoinduced charge carriers, which efficiently prolongs the lifetime of the charge carriers and reduces the electron-hole recombination rate, as all of these are all beneficial for boosting the photocatalytic activity of the catalysts. Experimental results show that OCCN0.25 displays the best photocatalytic CO2 reduction performance with a CO production rate of 34.97 μmol g−1 in 4 h, which is 4.3-fold higher than that obtained in the case of bulk g-CN. Moreover, the reaction is performed in water without any co-catalyst and sacrificial agent, which makes it a green and environmentally friendly reaction. Results obtained from DFT simulation agree well with the empirical results, and a possible reaction mechanism is suggested based on these calculations.

Domain walls in neutron P23 superfluids in neutron stars

We work out domain walls in neutron $^{3}P_{2}$ superfluids realized in the core of neutron stars. Adopting the Ginzburg-Landau (GL) theory as a bosonic low-energy effective theory, we consider configurations of domain walls interpolating ground states, i.e., the uniaxial nematic (UN), ${\mathrm{D}}_{2}$-biaxial nematic (${\mathrm{D}}_{2}$-BN), and ${\mathrm{D}}_{4}$-biaxial nematic $({\mathrm{D}}_{4}$-BN) phases in the presence of zero, small and large magnetic fields, respectively. We solve the Euler-Lagrange equation from the GL free energy density, and calculate surface energy densities of the domain walls. We find that one extra Nambu-Goldstone mode is localized in the vicinity of a domain wall in the UN phase while a U(1) symmetry restores in the vicinity of one type of domain wall in the ${\mathrm{D}}_{2}$-BN phase and all domain walls in the ${\mathrm{D}}_{4}$-BN phase. Considering a pile of domain walls in the neutron stars, we find that the most stable configurations are domain walls perpendicular to the magnetic fields piled up in the direction along the magnetic fields in the ${\mathrm{D}}_{2}$-BN and ${\mathrm{D}}_{4}$-BN phases. We estimate the energy released from the deconstruction of the domain walls in the edge of a neutron star, and show that it can reach an astrophysical scale such as glitches in neutron stars.

Monomer release from bulk-fill composite resins in different curing protocols.

The purpose of this study was to determine the depth of cure and the type and amount of monomers released from bulk-fill composites in different curing protocols. Five different composite resins Filtek Bulk-Fill Posterior, Filtek Bulk-Fill Flowable, SureFil SDR, X-tra Fil, and X-tra base, were used. A light-emitting diode (LED) device was used in 3 different modes (standard, high power, and extra power mode), and a halogen light device was also used as a control. Surface hardness was measured and the depth of cure was calculated. Monomer analysis was performed using high performance liquid chromatography (HPLC). The data were analyzed using Tamhane's T2 post-hoc test (α = 0.05). The cure depth for all materials except for Filtek Bulk-Fill Posterior (extra power mode) and Filtek Bulk-Fill Flowable (high power and extra power modes) was over 80%. Under the conditions of this study, the amount of monomer released from composite resins changed according to the type of composite resin and the light mode used.

Characterization and Design of Wideband Penta- and Hepta-Resonance SIW Elliptical Cavity-Backed Slot Antennas

Substrate integrated waveguide (SIW) elliptical cavity-backed slot antennas (CBSAs) with either penta- or hepta-resonance are characterized and designed for wideband performance in this paper. First, the resonant behavior of the elliptical cavity is explored. Then the SIW CBSA with penta-resonance is designed by introducing a cross-shaped slot and a pair of unbalanced shorting vias into the cavity to excite two additional odd- and even- half degenerate quasi-TM 110 modes, besides other three modes of half quasi-TM 010 , and odd- and even- quasi-TM 110 . Further, by adding another pair of unbalanced shorting vias, two extra higher-order modes, i.e., odd- and even- quasi-TM 210 modes are successfully introduced to design a hepta-resonance antenna. The corresponding mode analysis and design guidelines are discussed in detail. Two prototypes are fabricated and measured at X-band, exhibiting the measured bandwidths of 21.8% and 22.7%, respectively. Measured results agree well with simulations, thus validating the design concept.

Admet, molecular docking studies and binding energy calculations of pyrimidine-2-thiol derivatives as cox inhibitors

Cyclooxygenase (COX), is an enzyme that is responsible for the formation of prostanoids, including thromboxane and prostaglandins. Prostaglandins promote inflammation. Blockage of COX enzymes reduces prostaglandins and thus their effects are reduced. The present study focuses on In silico ADMET, molecular docking studies and binding energy calculations of ten pyrimidine derivatives as cox-1 and cox-2 inhibitors. Molecular docking studies were conducted on two target enzymes. Energy minimisation of the ligands was carried out using ligprep. They were docked to the active site of the proteins using the extra precision mode of glide module. The docked poses were ranked according to their docking score and binding energy with the enzymes. Compound PY4 showed better docking score with cox-1 (−6.081 kcal/mol) and compound PY5 showed good docking score with cox-2 (−8.602 kcal/mol). All compounds were found to have good docking and binding affinity scores when compared to the standards. Thus it reveals that the synthesised compounds act as anti-inflammatory agents by inhibiting cox-1 and cox-2 enzymes.

Indolizine: In-silico identification of inhibitors against mutated BCR-ABL protein of chronic myeloid leukemia

Unusual and rapid reproductions of oncogene BCR-ABL protein in the stem cells has been established as the major cause of Chronic Myeloid Leukemia. It has been recognized that tyrosine kinase province of BCR-ABL protein is a possible healing target for the action of Chronic Myeloid Leukemia. First generation drug Imatinib could impede the enzymatic action by impeding the ATP binding with BCR-ABL protein. Second generation drugs Bosutinib, Nilotinib, Dasatinib, Ponatinib, Bafetinib can also against the mutated province of ABL tyrosine kinase protein. The purpose of the present study was to virtually screen the Indolizine databases compound library downloaded. The structure-based virtual screening on BCR-ABL was downloaded from protein data bank. The exhaustive docking approach on BCR-ABL has been performed using simple precision and extra precision mode and the findings of most potent compounds have been evaluated for their absorption, distribution, metabolism and excretion.