Suppression Characteristics Research Articles

Suppression of methane/air deflagration-to-detonation transition in the linked vessel

A set of experimental equipment for suppression of methane/air deflagration-to-detonation transition (DDT) was proposed. In this investigation, a 113-L cylindrical vessel and a 6-m long linked pipe with a 100-mm internal diameter were used to investigate the suppression characteristics of methane/air deflagration-to-detonation transition (DDT) in a linked vessel. The experimental results showed that multi-layer mesh and aluminum silicate wool were effective in preventing DDT in this setup. All the aluminum silicate wool and wire mesh used in the experiments except for the 5-layer 40-mesh mental wire mesh can suppress DDT in the linked vessel. There is a significant pressure difference at the end of pipe when multi-layer metal mesh was used. The suppression effect was obvious, the pressure at the end of the pipe was reduced by about 70% when 25 layers wire-mesh were used. With the increase of mesh layer, the suppression effect is better. In general, the explosion suppression effect of mesh layers on 40 mesh wire mesh is more significant than that on 60 mesh wire mesh. In addition, an increase of thickness and length of aluminum silicate wool can enhance the explosion suppression performance. The aluminum silicate wool with a length of 900 mm and a thickness of 5 mm reduces the maximum pressure by about 61%.

Interrupted sampling repeater jamming countermeasure technology based on random interpulse frequency coding LFM signal

Interrupted sampling repeater jamming (ISRJ) is an active coherent jamming with the characteristic of suppression and deception, which poses a great threat to modern radars. In this work, a false target identification and suppression method based on random interpulse frequency coding linear frequency modulation (RIFC-LFM) signal processing is proposed. First, we analyze the characteristics of the RIFC-LFM signal and ISRJ using the ambiguity function and cross ambiguity function, respectively. Next, taking advantage of the property that most of the false targets formed by ISRJ will be whitened after range-Doppler processing, a false target range-Doppler (RD) spectrum reconstruction method is proposed. Using the reconstructed false target RD spectrum, we can obtain the positions of the unwhitened false targets in the RD spectrum and distinguish the true and false targets. Finally, we design the suppression matrix based on the reconstructed false target RD spectrum to suppress the false targets. The simulation results demonstrate that the proposed approach can effectively suppress three different ISRJs without estimating the ISRJ parameters.

Cooling Characteristic of an Infrared Suppression Device With Single Perforated Funnel: A Computational Fluid Dynamics Approach

Abstract An infrared suppression (IRS) device is integral to any gas turbine used in naval and cargo ships. Estimating an IRS device’s cooling characteristics is essential to start the maintenance operation. Thus, this article presents a computational investigation of the cooling characteristics of an infrared suppression device with a single cylindrical funnel with or without circular perforations. All simulations have been carried out in a steady and laminar environment. The numerical procedure adopted in this work has been validated with the existing correlations and achieved satisfactory agreement. The effect of the Rayleigh number and the length-to-diameter ratio of the funnel have been varied within the practical range to observe their effects on the averaged Nusselt number, heat transfer rate, mass suction rate, velocity fields, and thermal plumes. Moreover, the cooling performance has been compared for funnels without and with circular perforations. It is observed that the average Nu and the heat transfer rate increase with an increase in the Ra. Conversely, the average Nu first increases and then reduces with an increase in L/D. On the contrary, the heat transfer rate decreases monotonically with an increase in the L/D. The suction of fresh air into the funnel increases with Ra, whereas it reduces with an increase in L/D. The perforated funnels have better heat dissipation capacity than the unperforated ones.

Organic-Inorganic Modification of Magnesium Borate Rod by Layered Double Hydroxide and 3-Aminopropyltriethoxysilane and Its Effect on the Properties of Epoxy Resin.

To alleviate the safety hazards associated with the use of epoxy resin (EP), a multifunctional filler was designed. This study firstly combines the superior mechanical properties of magnesium borate rods (MBR) with the excellent smoke suppression and flame-retardant characteristics of layered double hydroxide (LDH). H2PO4− intercalated LDH (LDHP) was coated on the MBR surface to obtain inorganic composite particles MBR@LDHP. Subsequently, MBR@LDHP was modified with 3-aminopropyltriethoxysilane (APES) to obtain organic-inorganic composite particles MBR@LDHP-APES. Eventually, the hybrid particles were added to EP to prepare the composite materials. Thereafter, the morphology, composition, and structure of MBR@LDHP-APES were characterized utilizing scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and X-ray diffraction (XRD). The results indicated the successful preparation of MBR@LDHP-APES, after which we investigated the effects of MBR@LDHP-APES on the smoke suppression, flame retardancy, and mechanical characteristics of EP. As observed, the EP composites containing 7.5 wt% MBR@LDHP-APES exhibited superior smoke suppression and flame retardancy abilities. The limiting oxygen index reached 33.5%, which is 36.73% greater than pure EP, and the lowest values of total heat and smoke release were observed for the composite materials. In addition, the mechanical properties test revealed that MBR@LDHP-APES considerably enhanced the tensile strength as well as the flexural strength of the composites. Furthermore, mechanistic studies suggested that the barrier effect of MBR, endothermic decomposition of LDHP, and the synergistic effect of LDHP and APES contributed essentially to the smoke suppression and flame-retardant properties of the material. The findings of this research point to a potential method for enhancing the EP’s ability to suppress smoke and flames while enhancing its mechanical properties.

Study on the Effect of KHCO3 Particle Size and Powder Spraying Pressure on the Methane Explosion Suppression Characteristics of Pipe Networks.

To achieve the best explosion suppression effect of an active powder spraying system, the KHCO3 powder suppression test for a 9.5% methane–air premixed methane explosion was studied based on an independent test platform consisting of a pipe network. The suppression effect of KHCO3 powder particle size and powder spraying pressure on the methane explosion shock wave pressure, flame wave velocity, and flame wave temperature were studied, and the explosion suppression mechanism was analyzed. The results indicated that both the particle size of the KHCO3 powder and powder spraying pressure had a significant effect on the explosion inhibition. When the spraying pressure was in the range of 0.1–0.2 MPa, the increase in KHCO3 powder spraying pressure on the effect of explosion suppression was significantly enhanced, and when the powder spraying pressure exceeded 0.2 MPa, the explosion suppression effect did not obviously increase. With a reduction in the KHCO3 powder particle size, the effect of explosion suppression significantly improved, and when the KHCO3 powder particle size was reduced to 50–75 μm, we observed the best shock wave pressure, flame wave velocity, and flame wave temperature suppression effect.

Fast frequency relocking for synchronization enhanced resonant accelerometer

Synchronization, as a unique phenomenon, has been extensively studied in biology, chaotic systems, nonlinear dynamics, quantum information, and other fields. Benefiting from the characteristics of frequency amplification, noise suppression, and stability improvement, synchronization has been gradually applied in sensing, communication, time keeping, and other applications. In the sensing field, synchronization provides a new strategy to improve the performance of sensors. However, the performance improvement is only effective within the synchronization range, and the narrow synchronization range has become a great challenge for the wide application of synchronization-enhanced sensing mechanism. Here, we propose a frequency automatic tracking system (FATS) to widen the synchronization range and track the periodic acceleration signals by adjusting the frequency of the readout oscillator in real time. In addition, a high-precision frequency measurement system and fast response control system based on FPGA (Field Programmable Gate Array) are built, and the tracking performance of the FATS for static and dynamic external signals is analyzed to obtain the optimal control parameters. Experimental results show that the proposed automatic tracking system is capable of static acceleration measurement, the synchronization range can be expanded to 975 Hz, and the relocking time is shortened to 93.4 ms at best. By selecting the optimal PID parameters, we achieve a faster relocking time to meet the requirements of low-frequency vibration measurements, such as seismic detection and tidal monitoring.

Respiratory and systemic monocytes, dendritic cells, and myeloid-derived suppressor cells in COVID-19: Implications for disease severity.

Since the beginning of the SARS‐CoV‐2 pandemic in 2020, researchers worldwide have made efforts to understand the mechanisms behind the varying range of COVID‐19 disease severity. Since the respiratory tract is the site of infection, and immune cells differ depending on their anatomical location, studying blood is not sufficient to understand the full immunopathogenesis in patients with COVID‐19. It is becoming increasingly clear that monocytes, dendritic cells (DCs), and monocytic myeloid‐derived suppressor cells (M‐MDSCs) are involved in the immunopathology of COVID‐19 and may play important roles in determining disease severity. Patients with mild COVID‐19 display an early antiviral (interferon) response in the nasopharynx, expansion of activated intermediate monocytes, and low levels of M‐MDSCs in blood. In contrast, patients with severe COVID‐19 seem to lack an early efficient induction of interferons, and skew towards a more suppressive response in blood. This is characterized by downregulation of activation markers and decreased functional capacity of blood monocytes and DCs, reduced circulating DCs, and increased levels of HLA‐DRloCD14+ M‐MDSCs. These suppressive characteristics could potentially contribute to delayed T‐cell responses in severe COVID‐19 cases. In contrast, airways of patients with severe COVID‐19 display hyperinflammation with elevated levels of inflammatory monocytes and monocyte‐derived macrophages, and reduced levels of tissue‐resident alveolar macrophages. These monocyte‐derived cells contribute to excess inflammation by producing cytokines and chemokines. Here, we review the current knowledge on the role of monocytes, DCs, and M‐MDSCs in COVID‐19 and how alterations and the anatomical distribution of these cell populations may relate to disease severity.

Characterization of two-dimensional cellular elastic topological insulators based on regular-hexagon carriers

An elastic topological insulator with pseudo-spin characteristics is designed based on honeycomb lattice phononic crystals with positive hexagonal carriers, which can realize path defect immunity and backscattering suppression transmission characteristics. By introducing a positive hexagon carrier with a certain size at the narrow diameter junction of the two-dimensional honeycomb structure to achieve symmetry breaking, a four-fold accidental degeneracy point can be obtained by adjusting the cell parameters. The main variable of the primitive cell is the hexagonal carrier side length [Formula: see text]. It is found that the four-fold Dirac point can be opened and a band gap can be formed by contracting the positive hexagonal carrier. Inversion of the energy band occurred in the separated two-fold degenerate state, for which the transformation of mediocre state and nonmediocre state had been realized so that the structure with acoustic pseudo-spin and topological edge state could be obtained. Based on the principle of body-edge state correspondence, the topologically protected edge acoustic transmission is simulated by the construction of the edge states combined with the connection of different structural systems. Further, different elastic phonon crystal structures are constructed, and the characteristics of path defect immunity and back-scattering suppression of elastic wave propagation by topological edge states are verified. The designed elastic topological insulators have great application prospects in the regulation of elastic waves.

Role of Exosomes in Immunotherapy of Hepatocellular Carcinoma

Simple SummaryHepatocellular carcinoma is one of the most lethal malignancies, having a significantly poor prognosis. Immunotherapy, as an emerging tumor treatment option, provides new hope for many cancer patients. However, a large proportion of patients do not benefit from immunotherapy. As a critical cell-to-cell communication mediator in the tumor immune microenvironment, exosomes may play a unique role in hepatocellular carcinoma immune response and thus affect the efficiency of immunotherapy. In this review, we discuss related research on the roles of exosomes in the current immunotherapy resistance mechanism of hepatocellular carcinoma. Furthermore, we also clarify the excellent predictive value of exosomes and the roles they play in improving immunotherapy efficacy for hepatocellular carcinoma patients. We hope that our review can help readers to gain a more comprehensive understanding of exosomes’ roles in hepatocellular carcinoma immunotherapy.Hepatocellular carcinoma (HCC) is one of the most lethal malignancies, having a significantly poor prognosis and no sufficiently efficient treatments. Immunotherapy, especially immune checkpoint inhibitors (ICIs), has provided new therapeutic approaches for HCC patients. Nevertheless, most patients with HCC do not benefit from immunotherapy. Exosomes are biologically active lipid bilayer nano-sized vesicles ranging in size from 30 to 150 nm and can be secreted by almost any cell. In the HCC tumor microenvironment (TME), numerous cells are involved in tumor progression, and exosomes—derived from tumor cells and immune cells—exhibit unique composition profiles and act as intercellular communicators by transporting various substances. Showing the dual characteristics of tumor promotion and suppression, exosomes exert multiple functions in shaping tumor immune responses in the crosstalk between tumor cells and surrounding immune cells, mediating immunotherapy resistance by affecting the PD-1/PD-L1 axis or the anti-tumor function of immune cells in the TME. Targeting exosomes or the application of exosomes as therapies is involved in many aspects of HCC immunotherapies (e.g., ICIs, tumor vaccines, and adoptive cell therapy) and may substantially enhance their efficacy. In this review, we discuss the impact of exosomes on the HCC TME and comprehensively summarize the role of exosomes in immunotherapy resistance and therapeutic application. We also discuss the potential of exosomes as biomarkers for predicting the efficacy of immunotherapy to help clinicians in identifying HCC patients who are amenable to immunotherapies.

Synergistic effects of Al/Si double oxide on flame-retardant and smoke-suppressant wooden materials

Wooden materials have many advantages, but they easily burn and release CO, CO2, and harmful volatile organic compounds (VOCs), which pose threats to health and safety. This work adopted a low-cost method, using environmentally friendly silicate (Na2SiO3), aluminum sulfate (Al2(SO4)3), and water-borne epoxy resin to prepare composite poplar wood (Al–Si-EPW), which synergistic displayed flame retardancy, smoke suppression, and self-extinguishing characteristics. The time of peak heat release rate (HRR) and peak smoke production rate (SPR) of Al–Si-EPWwere 340 s and 315 s, which were delayed by about 105 s and 100 s compared with untreated wood (UW), respectively. This provides more security for controlling the fire spread and evacuating people. The peak value of heat release rate and smoke production of Al–Si-EPW decreased by 39.04% and 34.68%, and the peak CO2 production (CO2P) and CO production (COP) were reduced by 69.75% and 74.74%. Moreover, the main category and the amount of VOCs released during the combustion process decreased significantly. With the increase in aluminum sulfate dosage, it showed better flame retardant and smoke suppression effects. This indicated that Al–Si-EPW only released a small amount of toxic smoke, greatly reducing the possibility of suffocation and damage. Therefore, this material can be widely used as a flame-retardant wood building material.

Free convection heat transfer with surface radiation from infrared suppression system and estimation of cooling time

• The thermo-fluid characteristics of the full-scale infrared suppression (IRS) system used in the marine gas turbine as an exhaust system are numerically investigated here. • The combined impact of conduction, convection, and radiation on the cooling of the IRS system is intended to be explored. • Various relevant parameters are taken for the analysis, viz., Rayleigh number (Ra), number of funnels, funnel wall temperature, diameter ratio (DR), funnel overlapping (OL), and emissivity of the surface (ε). • A generalized correlation for Nusselt number is developed, considering surface emissivity and the number of funnels as an independent parameter that can be used for academic and industrial applications. • The novelty of the work lies in finding the heat transfer rate and cooling time of the IRS device with varying numbers of funnels (3 to 6 funnels) subjected to the combined effect of free convection and surface radiation. A numerical study is performed on Infrared Suppression (IRS) system having finite wall thickness to observe the combined effect of free convection and surface radiation. The main focus of this work is to obtain thermo-fluid characteristics of natural convection phenomena from the IRS system due to conjugate heat transfer and surface radiation. In addition, the time required to cool down the hot IRS system to atmospheric temperature is also estimated. For the numerical analysis, different governing equations (Navier-Stokes equation, energy equation, and radiation equation) are solved using the finite volume method (FVM) based solver of ANSYS Fluent v 15. Several pertinent parameters, viz., the number of funnels, Rayleigh number, inner surface temperature, geometric ratio, funnel overlapping, and surface emissivity, are varied to elucidate the heat transfer behavior. It is evident from the research that surface radiation has a significant influent on total heat transfer and should not be ignored. In addition, the total heat transfer rate rises with the number of funnels. Both non-dimensional induced mass flow rate and total heat transfer rate have maximum value for zero overlapping cases. At constant temperature contribution of radiative heat transfer varies from 10 to 38% with the rise in emissivity. The inclusion of radiation with convection lowers the cooling time significantly compared to convection alone.

Prediction of EMI Filter Attenuation in Power-Electronic Converters via Circuit Simulation

This article investigates the conducted-emission (CE) suppression characteristics of electromagnetic interference (EMI) filters used in power-electronic equipment by time-domain circuit simulation. An operational definition of insertion attenuation is introduced by comparing the CE in the absence and in the presence of the EMI filter. For the sake of exemplification, the analysis focuses on switched-mode dc–dc converters. It is shown that the EMI-filter attenuation behaves differently from the standard insertion loss (IL) and exhibits peculiar properties in these circuits. Namely, its response is known at discrete frequencies where the converter generates CE and may strongly depend on the harmonic index so to jump between quite different levels from a harmonic component to the next one, with a pseudoperiodic behavior, which can be related to the duty cycle. This effect is caused by circuit nonlinearity and is partially mitigated if the simulation accounts for two practically relevant aspects: random instability of the duty cycle and resolution bandwidth of the EMI receiver. The dependence of the common-mode (CM) and differential-mode attenuations on the loading conditions and duty cycle is analyzed, and it is shown that linear IL models provide reasonable predictions of CM attenuation only. Finally, experimental evidence of the unveiled phenomena is presented.

SuperFormer: Enhanced Multi-Speaker Speech Separation Network Combining Channel and Spatial Adaptability

Speech separation is a hot topic in multi-speaker speech recognition. The long-term autocorrelation of speech signal sequences is an essential task for speech separation. The keys are effective intra-autocorrelation learning for the speaker’s speech, modelling the local (intra-blocks) and global (intra- and inter- blocks) dependence features of the speech sequence, with the real-time separation of as few parameters as possible. In this paper, the local and global dependence features of speech sequence information are extracted by utilizing different transformer structures. A forward adaptive module of channel and space autocorrelation is proposed to give the separated model good channel adaptability (channel adaptive modeling) and space adaptability (space adaptive modeling). In addition, at the back end of the separation model, a speaker enhancement module is considered to further enhance or suppress the speech of different speakers by taking advantage of the mutual suppression characteristics of each source signal. Experiments show that the scale-invariant signal-to-noise ratio improvement (SI-SNRi) of the proposed separation network on the public corpus WSJ0-2mix achieves better separation performance compared with the baseline models. The proposed method can provide a solution for speech separation and speech recognition in multi-speaker scenarios.

Drag reduction of a generic transport vehicle model using a fluidic oscillator

Base blowing is performed using a sweeping jet actuator centrally located at the base of a square-back Ahmed body. Drag reduction along with a significant effect in terms of wake RSB mode suppression is reported for such fluid injection. All three scales of fluidic actuation exhibit similar wake bistability suppression characteristics. RSB mode suppression is also corroborated through independent force measurements. For all scales of actuators, the optimal blowing coefficient Cqopt is found to scale with bleed-to-base area ratio as (Sj/S)3/4, whereas the blowing coefficient corresponding to the minimum magnitude of wake asymmetry scales as Cqopt(Sj/S)5/12. The small-scale actuator also presents a more energy-efficient base blowing in terms of the amount of drag reduction achieved per energy consumed.

Fire extinguishing and explosion suppression characteristics of explosion suppression system with N2/APP after methane/coal dust explosion

The study aims to examine the suppression performance of an inhibitor after a methane/coal dust explosion. The design of an explosion suppression system included the carrier gas of nitrogen (N2) with an inhibitor of ammonium polyphosphate (APP). The study investigated fire extinguishing and explosion suppression of methane/coal dust by N2/APP in a vertical pipe. Flame propagation characteristics were measured by a high-speed camera, micro-thermocouple, and pressure sensor. The residues after the explosion were characterized chemically by X-ray photoelectron spectroscopy, and the thermal decomposition characteristics of coal dust and APP in the N2 atmosphere were analyzed by synchronous thermal analysis. Experimental results show that the explosion suppression system can effectively hinder the flame propagation of methane/coal dust explosion. The flame height, bottom velocity, and temperature were all weakened significantly. The optimum level of suppressant minimizes the explosion pressure and suppresses the flame significantly. In addition, the fire extinguishing and explosion suppression mechanisms of N2/APP were summarized. The suppression method used in this study blocks the explosion after it occurs rather than preventing it through premixed inerting.

Unique characteristics of lung-resident neutrophils are maintained by PGE2/PKA/Tgm2-mediated signaling

AbstractLung-resident neutrophils need to be tightly regulated to avoid degranulation- and cytokine-associated damage to fragile alveolar structures that can lead to fatal outcomes. Here we show that lung neutrophils (LNs) express distinct surface proteins and genes that distinguish LNs from bone marrow and blood neutrophils. Functionally, LNs show impaired migratory activity toward chemoattractants and produce high levels of interleukin-6 (IL-6) at steady state and low levels of tumor necrosis factor-α in response to lipopolysaccharide (LPS) challenge. Treating bone marrow neutrophils with bronchoalveolar lavage fluid or prostaglandin E2 induces LN-associated characteristics, including the expression of transglutaminase 2 (Tgm2) and reduced production of inflammatory cytokines upon LPS challenge. Neutrophils from Tgm2−/− mice release high levels of inflammatory cytokines in response to LPS. Lung damage is significantly exacerbated in Tgm2−/− mice in an LPS-induced acute respiratory distress syndrome model. Collectively, we demonstrate that prostaglandin E2 is a key factor for the generation of LNs with unique immune suppressive characteristics, acting through protein kinase A and Tgm2, and LNs play essential roles in protection of the lungs against pathogenic inflammation.

Systematic study of nuclear effects in p+Al, p+Au, d+Au , and He3+Au collisions at sNN=200 GeV using π0 production

The PHENIX Collaboration presents a systematic study of inclusive π0 production from p+p, p+Al, p+Au, d+Au, and He3+Au collisions at sNN=200GeV. Measurements were performed with different centrality selections as well as the total inelastic, 0–100%, selection for all collision systems. For 0–100% collisions, the nuclear-modification factors, RxA, are consistent with unity for pT above 8GeV/c, but exhibit an enhancement in peripheral collisions and a suppression in central collisions. The enhancement and suppression characteristics are similar for all systems for the same centrality class. It is shown that for high-pT−π0 production, the nucleons in the d and He3 interact mostly independently with the Au nucleus and that the counterintuitive centrality dependence is likely due to a physical correlation between multiplicity and the presence of a hard scattering process. These observations disfavor models where parton energy loss has a significant contribution to nuclear modifications in small systems. Nuclear modifications at lower pT resemble the Cronin effect—an increase followed by a peak in central or inelastic collisions and a plateau in peripheral collisions. The peak height has a characteristic ordering by system size as p+Au>d+Au>He3+Au>p+Al. For collisions with Au ions, current calculations based on initial-state cold nuclear matter effects result in the opposite order, suggesting the presence of other contributions to nuclear modifications, in particular at lower pT.6 MoreReceived 11 November 2021Accepted 3 May 2022DOI:https://doi.org/10.1103/PhysRevC.105.064902©2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasHadronic decaysLeptonic, semileptonic & radiative decaysParticle & resonance productionParticle decaysRelativistic heavy-ion collisionsPhysical SystemsMesonsTechniquesHadron collidersNuclear Physics

Investigation of signal-to-noise ratio performance of microwave photonic links enhanced by optical injection locking and channelized spectrum stitching.

A signal-to-noise ratio (SNR) improvement method for microwave photonic (MWP) links enhanced by optical injection locking (OIL) and channelized spectrum stitching (CSS) is investigated and experimentally demonstrated. By exploiting the resonant amplification characteristics of OIL, both optical gain and in-band noise suppression of the input radio frequency signal can be achieved. The injection bandwidth is channelized to further suppress noise during OIL, and the input signal can be well reconstructed by spectrum stitching in the digital domain. Experimental results show that the optimal improvement in SNR of 3.6 dB is achieved for linear frequency modulated signals and at least an additional improvement of 7.2 dB can be obtained by adopting CSS. Other broadband signals for radar and communication are used to further verify the ability to improve SNR. The potential for application scenarios with large operating bandwidth and high optical gain is also demonstrated.

An experimental study on the backfire occurrence and combustion stabilization of high-efficiency hydrogen-fueled free-piston linear power systems

A scavenging method suitable for high-efficiency hydrogen (H2)-fueled two-stroke free-piston linear power systems as a next-generation alternative engine is experimentally studied, investigating the driving and backfire suppression characteristics of various scavenging methods by using a rapid compression expansion machine. A simple structured loop-scavenging method which was expected to be unfavorable for suppressing backfire in H2-fueled power systems is more advantageous than the valve-driven scavenging methods when the system performance is evaluated together. For the loop-scavenging method, no backfire is observed at the fuel-equivalence ratio φ ≤ 0.6 when the ignition timing IGT is set for the maximum pressure (MPT) and the backfire limit can be extended to φ = 0.8 if IGT is advanced than MPT, showing the maximum indicated thermal efficiency of 48%. The performance test using a single-type H2-fueled free-piston linear power system adopting the loop-scavenging successfully demonstrates stable continuous operation with no backfire at φ ≤ 0.8.

Stochastic Bifurcation and Energy Transfer in an Inerter-Based Pendulum Vibration Absorber

Abstract In this theoretical study, the vibration suppression, energy transfer, and bifurcation characteristics, as a function of dimensionless parameters, are investigated for an inerter-based pendulum vibration absorber (IPVA) attached to a linear single-degree-of-freedom spring-mass-damper system (primary structure), subject to white noise excitation. A perturbation method is introduced to detect and track the bifurcation points of the system. It is shown that the marginal probability density function of the pendulum angular displacement undergoes a P-bifurcation at critical parameter values, transitioning from monomodality to bi-modality. A cumulant-neglect technique is used to predict the mean squares of the system, which are compared to the response of a linear system without the IPVA to quantify the vibration suppression. It is shown that the IPVA leads to effective vibration mitigation of the structure in the neighborhood of the P-bifurcation, which is achieved by transferring the kinetic energy of the structure to the pendulum. The results are validated by a Monte Carlo simulation that is used to numerically approximate the marginal probability density function for the pendulum angle as well as the mean squares.