scholarly journals Impact of coherence decay on wavepacket models for broadband shock-associated noise in supersonic jets

2019 ◽  
Vol 863 ◽  
pp. 969-993 ◽  
Author(s):  
Marcus H. Wong ◽  
Peter Jordan ◽  
Damon R. Honnery ◽  
Daniel Edgington-Mitchell
Keyword(s):  
Dynamic Models ◽  
Critical Role ◽  
Coherence Function ◽  
Supersonic Jets ◽  
Far Field ◽  
Shock Cell ◽  
Acoustic Spectrum ◽  
Flow Mechanisms ◽  
The Relationship ◽  
Field Sound

Motivated by the success of wavepackets in modelling the noise from subsonic and perfectly expanded supersonic jets, we apply the wavepacket model to imperfectly expanded supersonic jets. Recent studies with subsonic jets have demonstrated the importance of capturing the ‘jitter’ of wavepackets in order to correctly predict the intensity of far-field sound. Wavepacket jitter may be statistically represented using a two-point coherence function; accurate prediction of noise requires identification of this coherence function. Following the analysis of Cavalieri & Agarwal (J. Fluid Mech., vol. 748, 2014. pp. 399–415), we extend their methodology to model the acoustic sources of broadband shock-associated noise in imperfectly expanded supersonic jets using cross-spectral densities of the turbulent and shock-cell quantities. The aim is to determine the relationship between wavepacket coherence-decay and far-field broadband shock-associated noise, using the model as a vehicle to explore the flow mechanisms at work. Unlike the subsonic case where inclusion of coherence decay amplifies the sound pressure level over the whole acoustic spectrum, we find that it does not play such a critical role in determining the peak sound amplitude for shock-cell noise. When higher-order shock-cell modes are used to reconstruct the acoustic spectrum at higher frequencies, however, the inclusion of a jittering wavepacket is necessary. These results suggest that the requirement for coherence decay identified in prior broadband shock-associated noise (BBSAN) models is in reality the statistical signature of jittering wavepackets. The results from this modelling approach suggest that nonlinear jittering effects of wavepackets need to be included in dynamic models for broadband shock-associated noise.

Noisefield of Underexpanded Notched Circular-Slot Jets

2002 ◽  
Vol 33 (6) ◽  
pp. 9-23
Author(s):  
S.B. Verma ◽  
E. Rathakrishnan
Keyword(s):  
Acoustic Emission ◽  
Aspect Ratio ◽  
Cell Length ◽  
Emission Characteristics ◽  
Far Field ◽  
Shock Cell ◽  
Acoustic Spectrum ◽  
Compression Waves ◽  
Noise Field ◽  
Notch Geometry

The effect of notches on the flow and noise field of jets from circular-slots is experimentally investigated. Three types of slot geometries, namely, semicircular, triangular and square are studied. The results demonstrate that the presence of the notch introduces a slight aspect-ratio in the initial circular-slot geometry so that the notched jet exhibits characteristics, similar to jets exiting from non-circular geometries. At underexpanded condition, additional expansion and compression waves are observed to emanate from the region of notches that modifies the jet development and results in a reduction in the average shock-cell length, which is accompanied by a reduction in far-field shock associated noise. The acoustic spectrum of the radiated shock noise indicates that notch geometry variation strongly alters the acoustic emission characteristics of these jets both in the screech component and broadband shock associated noise.

Coherence decay and its impact on sound radiation by wavepackets

2014 ◽  
Vol 748 ◽  
pp. 399-415 ◽  
Author(s):  
André V. G. Cavalieri ◽  
Anurag Agarwal
Keyword(s):  
Coherence Function ◽  
Sound Radiation ◽  
Turbulent Jets ◽  
Sufficient Condition ◽  
Far Field ◽  
Mean Flow ◽  
Spectral Densities ◽  
Flow Fluctuations ◽  
Order Of Magnitude ◽  
Field Sound

AbstractWavepackets obtained by a linear stability analysis of the turbulent mean flow were shown in recent works to agree closely with some relevant statistics of turbulent jets, such as power spectral densities and averaged phases of flow fluctuations. However, when such wavepacket models were used to calculate the far-field sound, satisfactory agreement was only obtained for flows that were supersonic relative to the ambient speed of sound; attempts with subsonic flows led to errors of more than an order of magnitude. We investigate here the reasons for such discrepancies by developing the integral solution of the Helmholtz equation in terms of the cross-spectral densities of turbulent quantities. It is shown that agreement of a statistical source, such as would be obtained by the above-mentioned wavepacket models, in averaged amplitudes and phases in the near field is not a sufficient condition for exact agreement of the far-field sound. The sufficient condition is that, in addition to the amplitudes and phases, the statistical source should also match the coherence function of the flow fluctuations. This is exemplified in a model problem, where we show that the effect of coherence decay on sound radiation is more prominent for subsonic convection velocities, and its neglect leads to discrepancies of more than an order of magnitude in the far-field sound. For supersonic flows errors are reduced for the peak noise direction, but for other angles the coherence decay is also seen to have a significant effect. Coherence decay in the model source is seen to lead to similar decays in the coherence of two points in the far acoustic field, these decays being significantly faster for higher Mach numbers. The limitations of linear wavepacket models are illustrated with another simplified problem, showing that superposition of time-periodic solutions can lead to a correlation decay between two points. However, the coherence between any pair of points in such models remains unity, and cannot thus represent the behaviour observed in turbulent flows.

XIST: A Meaningful Long Noncoding RNA in NSCLC Process

2020 ◽  
Vol 26 ◽  
Author(s):  
Yujie Shen ◽  
Yexiang Lin ◽  
Kai Liu ◽  
Jinlan Chen ◽  
Juanjuan Zhong ◽  
...  
Keyword(s):  
Therapeutic Target ◽  
Long Noncoding Rna ◽  
Noncoding Rna ◽  
Critical Role ◽  
Biological Functions ◽  
Potential Therapeutic Target ◽  
Considerable Evidence ◽  
Lncrna Xist ◽  
Nsclc Patients ◽  
The Relationship

Background: A number of studies have proposed that lncRNA XIST plays a role in the development and chemosensitivity of NSCLC. Besides, XIST may become a potential therapeutic target for NSCLC patients. The aim of this review is to reveal the biological functions and exact mechanisms of XIST in NSCLC. Methods: In this review, relevant researches involving in the relationship between XIST and NSCLC are collected through systematic retrieval of PubMed Results: XIST is an oncogene in NSCLC and is abnormally upregulated in NSCLC tissues. Considerable evidence has shown that XIST exerts a critical role in the proliferation, invasion, migration, apoptosis and chemosensitivity of NSCLC cells. XIST mainly functions as a ceRNA in NSCLC process, while XIST also functions at transcriptional levels. Conclusion: LncRNA XIST has potential to become a novel biomolecular marker of NSCLC and a therapeutic target for NSCLC.

scholarly journals Online Reviews and Product Sales: The Role of Review Visibility

2021 ◽  
Vol 16 (4) ◽  
pp. 638-669
Author(s):  
Miriam Alzate ◽  
Marta Arce-Urriza ◽  
Javier Cebollada
Keyword(s):  
Decision Making ◽  
Dynamic Models ◽  
Generalized Method Of Moments ◽  
Online Reviews ◽  
Consumer Decision Making ◽  
Product Sales ◽  
The Impact ◽  
The Relationship ◽  
The Empirical Analysis

When studying the impact of online reviews on product sales, previous scholars have usually assumed that every review for a product has the same probability of being viewed by consumers. However, decision-making and information processing theories underline that the accessibility of information plays a role in consumer decision-making. We incorporate the notion of review visibility to study the relationship between online reviews and product sales, which is proxied by sales rank information, studying three different cases: (1) when every online review is assumed to have the same probability of being viewed; (2) when we assume that consumers sort online reviews by the most helpful mechanism; and (3) when we assume that consumers sort online reviews by the most recent mechanism. Review non-textual and textual variables are analyzed. The empirical analysis is conducted using a panel of 119 cosmetic products over a period of nine weeks. Using the system generalized method of moments (system GMM) method for dynamic models of panel data, our findings reveal that review variables influence product sales, but the magnitude, and even the direction of the effect, vary amongst visibility cases. Overall, the characteristics of the most helpful reviews have a higher impact on sales.

scholarly journals Relationship between Emotional Intelligence and Violence Exerted, Received, and Perceived in Teen Dating Relationships

2021 ◽  
Vol 18 (5) ◽  
pp. 2284
Author(s):  
Cordelia Estevez-Casellas ◽  
Mª Dolores Gómez-Medina ◽  
Esther Sitges
Keyword(s):  
Emotional Intelligence ◽  
Social Relationships ◽  
Violent Behavior ◽  
Critical Role ◽  
Dating Relationships ◽  
Significant Relation ◽  
Violent Behaviors ◽  
Teen Dating ◽  
The Relationship

Emotional intelligence plays a critical role in adolescence since it involves a change towards psychological, social, and sexual maturity; a stage in which the foundations of intimate social relationships are established. Emotional competences regulate the quality of these relationships in adolescence and can provide protection against or facilitate the use of violence within them. Based on the above, this study aims to analyze the relationship between emotional intelligence and violence exercised, received, and perceived by adolescents in dating relationships. A sample of 254 subjects (43.1% men and 56.9% women) between 12 and 18 years old was analyzed through the Emotional Intelligence Questionnaires of BarOn ICE:NA and Violence Exercised Perceived and Received by Adolescents VERA. The results of the research have shown that there is a significant and inverse relation between the dimensions of emotional intelligence and the violence exercised by adolescents in their dating relationships, and a positive and significant relation between emotional intelligence and the perception of violent behavior. For this reason, the importance of educating people about emotional intelligence from childhood within both the academic and family sphere is highlighted. This is fundamental to preventing the appearance of such violent behaviors and promoting an adequate adaptation to the environment.

scholarly journals Potential mechanisms involving the immobilization of Cd, As and Cr during swine manure composting

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Hao-Nan Guo ◽  
Li-Xia Wang ◽  
Hong-Tao Liu
Keyword(s):  
Cation Exchange Capacity ◽  
Physicochemical Parameters ◽  
Redundancy Analysis ◽  
Critical Role ◽  
Swine Manure ◽  
Exchange Capacity ◽  
Bulking Agent ◽  
Initial Carbon ◽  
Acid Ratio ◽  
The Relationship

Abstract This study aims to investigate the relationship between key physicochemical parameters related to composting process and bioavailability of Cd, As and Cr during swine manure composting through regulating different initial carbon to nitrogen (C/N) ratios (15:1, 20:1, 25:1) and bulking agent types (straw, green waste). Results showed that higher initial C/N ratio of 20:1 or 25:1 and straw as bulking agent were optimal to reduce the bioavailability of Cd, As and Cr (62.4%, 20.6% and 32.2% reduction, respectively). Redundancy analysis implied that the bioavailability of Cd was significantly associated with total phosphorus and total nitrogen, deducing the formation of phosphate precipitation and biosorption might participated in the reaction process, while that of As and Cr were mainly influenced by organic matter (OM), cation exchange capacity (CEC) and OM, CEC, electric conductivity, respectively. A total of 48.5%, 64.6% and 62.2% of Cd, As and Cr redistribution information could be explained by the above parameters. Further correlation analysis revealed that bioavailable As and Cr were negatively correlated with humic acid to fulvic acid ratio. In summary, this study confirms that the mechanisms of phosphate precipitation, biosorption and humification played critical role in reducing Cd, As and Cr bioavailability during swine manure composting.

The gray matter volume of the right insula mediates the relationship between symptoms of depression/anxiety and sleep quality among college students

2019 ◽  
pp. 135910531986997 ◽  
Author(s):  
Huazhan Yin ◽  
Li Zhang ◽  
Dan Li ◽  
Lu Xiao ◽  
Mei Cheng
Keyword(s):  
College Students ◽  
Sleep Quality ◽  
Gray Matter ◽  
Emotional Processing ◽  
Gray Matter Volume ◽  
Critical Role ◽  
Symptoms Of Depression ◽  
Matter Volume ◽  
The Right ◽  
The Relationship

This study investigated the neuroanatomical basis of the association between depression/anxiety and sleep quality among 370 college students. The results showed that there was a significant correlation between sleep quality and depression/anxiety. Moreover, mediation results showed that the gray matter volume of the right insula mediated the relationship between depression/anxiety and sleep quality, which suggested that depression/anxiety may affect sleep quality through the right insula volume. These findings confirmed a strong link between sleep quality and depression/anxiety, while highlighting the volumetric variation in the right insula associated with emotional processing, which may play a critical role in improving sleep quality.

scholarly journals Structural and Acoustic Responses of a Submerged Stiffened Conical Shell

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Meixia Chen ◽  
Cong Zhang ◽  
Xiangfan Tao ◽  
Naiqi Deng
Keyword(s):  
Conical Shell ◽  
Element Model ◽  
Analytical Models ◽  
Superposition Method ◽  
Far Field ◽  
Fluid Loading ◽  
Low Frequencies ◽  
Structural Responses ◽  
The Individual ◽  
Field Sound

This paper studies the vibrational behavior and far-field sound radiation of a submerged stiffened conical shell at low frequencies. The solution for the dynamic response of the conical shell is presented in the form of a power series. A smeared approach is used to model the ring stiffeners. Fluid loading is taken into account by dividing the conical shell into narrow strips which are considered to be local cylindrical shells. The far-field sound pressure is solved by the Element Radiation Superposition Method. Excitations in two directions are considered to simulate the loading on the surface of the conical shell. These excitations are applied along the generator and normal to the surface of the conical shell. The contributions from the individual circumferential modes on the structural responses of the conical shell are studied. The effects of the external fluid loading and stiffeners are discussed. The results from the analytical models are validated by numerical results from a fully coupled finite element/boundary element model.

Medullary lateral tegmental field: control of respiratory rate and vagal lung inflation afferent influences on sympathetic nerve discharge

2005 ◽  
Vol 288 (5) ◽  
pp. R1396-R1410 ◽  
Author(s):  
Shaun W. Phillips ◽  
Gerard L. Gebber ◽  
Susan M. Barman
Keyword(s):  
Respiratory Rate ◽  
Sympathetic Nerve ◽  
Artificial Ventilation ◽  
Critical Role ◽  
Lung Inflation ◽  
Chemical Inactivation ◽  
A Value ◽  
Relationship Of ◽  
The Relationship ◽  
Nerve Discharge

We used spectral analysis and event-triggered averaging to determine the effects of chemical inactivation of the medullary lateral tegmental field (LTF) on 1) the relationship of intratracheal pressure (ITP, an index of vagal lung inflation afferent activity) to sympathetic nerve discharge (SND) and phrenic nerve activity (PNA) and 2) central respiratory rate in paralyzed, artificially ventilated dial-urethane-anesthetized cats. ITP-SND coherence value at the frequency of artificial ventilation was significantly ( P < 0.05; n = 18) reduced from 0.73 ± 0.04 (mean ± SE) to 0.24 ± 0.04 after bilateral microinjection of muscimol into the LTF. Central respiratory rate was unexpectedly increased in 12 of these experiments (0.28 ± 0.03 vs. 0.95 ± 0.25 Hz). The ITP-PNA coherence value was variably affected by chemical inactivation of the LTF. It was unchanged when central respiratory rate was also not altered, decreased when respiratory rate was increased above the rate of artificial ventilation, and increased when respiratory rate was raised from a value below the rate of artificial ventilation to the same frequency as the ventilator. Chemical inactivation of the LTF increased central respiratory rate in four of six vagotomized cats but did not significantly affect the PNA-SND coherence value. These data demonstrate that the LTF 1) plays a critical role in mediating the effects of vagal lung inflation afferents on SND but not PNA, 2) helps maintain central respiratory rate in the physiological range, but 3) is not involved in the coupling of central respiratory and sympathetic circuits.

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