Highest Frequency Of Interest Research Articles

Prevalent personality traits in psychology students: a decade of study. Analysis of associated transversal professional skills

Introduction: The knowledge of personality in university students and the professional skills necessary for adequate development and performance in professional settings are essential to implement more effective academic interventions that enhance successful professionals.Objective: Analyze prevalent personality traits according to: Motivational goals, Cognitive modes and Interpersonal behaviors corresponding to ten cohorts of psychology students (2010-2020).Method: longitudinal trend design, with descriptive-correlational scope. We worked with two intentional, non-probabilistic samples, psychology students: MI 2010-2020: 945 students, MII 2020: 48 students. Instruments: Million Inventory of Personality Styles (MIPS) and Questionnaire for the Evaluation of Transversal Competencies in University Students.Results: A personality profile was observed with the sustained presence of the traits of Modification, Communicativeness and Control, and absence of Accommodation. In the Professional Competencies, very high frequencies of Interest in Quality, Work Responsibility and Teamwork are evident; and very low frequencies of Social Responsibility. The Modification and Control traits are those that present associations with Transversal Professional Competencies.Conclusions: The profile that characterizes a cohort of psychology students during 10 years of study has been communicativeness and control in the interpersonal, the active and energetic attitude (modification) in the motivational, and the sustained absence of passivity and accommodation. Relationships were found with transversal professional competencies. The implication of the results is discussed

Top Coating Anti-Erosion Performance Analysis in Wind Turbine Blades Depending on Relative Acoustic Impedance. Part 2: Material Characterization and Rain Erosion Testing Evaluation

Under droplet impingement, surface leading edge protection (LEP) coating materials for wind turbine blades develop high-rate transient pressure build-up and a subsequent relaxation in a range of strain rates. The stress-strain coating LEP behavior at a working frequency range depends on the specific LEP and on the material and operational conditions, as described in this research in a previous work. Wear fatigue failure analysis, based on the Springer model, requires coating and substrate speed of sound measurements as constant input material parameters. It considers a linear elastic response of the polymer subjected to drop impact loads, but does not account for the frequency dependent viscoelastic effects for the materials involved. The model has been widely used and validated in the literature for different liquid impact erosion problems. In this work, it is shown the appropriate definition of the viscoelastic materials properties with ultrasonic techniques. It is broadly used for developing precise measurements of the speed of sound in thin coatings and laminates. It also allows accurately evaluating elastic moduli and assessing mechanical properties at the high frequencies of interest. In the current work, an investigation into various LEP coating application cases have been undertaken and related with the rain erosion durability factors due to suitable material impedance definition. The proposed numerical procedures to predict wear surface erosion have been evaluated in comparison with the rain erosion testing, in order to identify suitable coating and composite substrate combinations. LEP erosion performance at rain erosion testing (RET) technique is used widely in the wind industry as the key metric, in an effort to assess the response of the varying material and operational parameters involved.

Computer-Aided Design of a Switchable True Time Delay (TTD) Line With Shunt Open-Stubs

This paper presents a new technique to design switchable true time delay (TTD) lines using periodic shunt open-stubs, shorter than a quarter wavelength at the highest frequency of interest. Structural parameters are obtained by minimizing the group delay variation and maximizing the return loss over the operating band. Advantages of the proposed design are low insertion loss, higher 1 dB compression point, and less number of switches compared to the conventional designs. To verify the proposed technique, 2-states and 8-states TTD lines are fabricated for L- and S-band applications. For the 8-states delay networks, measured insertion losses are smaller than 1.9 dB at 3 GHz. Return losses are more than 10 dB over 1–4 GHz band. Measured maximum time delay is 84 ps for the 8-states delay lines with a step size of 10 ps. All the TTDs operate as linear device at least up to 23 dBm.

Hamilton’s principle and normal mode coupling in an aspherical planet with a fluid core

Seismic free oscillations, or normal modes, provide a convenient tool to calculate low-frequency seismograms in heterogeneous Earth models. A procedure called ‘full mode coupling’ allows the seismic response of the Earth to be computed. However, in order to be theoretically exact, such calculations must involve an infinite set of modes. In practice, only a finite subset of modes can be used, introducing an error into the seismograms. By systematically increasing the number of modes beyond the highest frequency of interest in the seismograms, we investigate the convergence of full-coupling calculations. As a rule-of-thumb, it is necessary to couple modes 1–2 mHz above the highest frequency of interest, although results depend upon the details of the Earth model. This is significantly higher than has previously been assumed. Observations of free oscillations also provide important constraints on the heterogeneous structure of the Earth. Historically, this inference problem has been addressed by the measurement and interpretation of splitting functions. These can be seen as secondary data extracted from low frequency seismograms. The measurement step necessitates the calculation of synthetic seismograms, but current implementations rely on approximations referred to as self- or group-coupling and do not use fully accurate seismograms. We therefore also investigate whether a systematic error might be present in currently published splitting functions. We find no evidence for any systematic bias, but published uncertainties must be doubled to properly account for the errors due to theoretical omissions and regularization in the measurement process. Correspondingly, uncertainties in results derived from splitting functions must also be increased. As is well known, density has only a weak signal in low-frequency seismograms. Our results suggest this signal is of similar scale to the true uncertainties associated with currently published splitting functions. Thus, it seems that great care must be taken in any attempt to robustly infer details of Earth's density structure using current splitting functions.

Exact free oscillation spectra, splitting functions and the resolvability of Earth's density structure

Seismic free oscillations, or normal modes, provide a convenient tool to calculate low-frequency seismograms in heterogeneous Earth models. A procedure called ‘full mode coupling’ allows the seismic response of the Earth to be computed. However, in order to be theoretically exact, such calculations must involve an infinite set of modes. In practice, only a finite subset of modes can be used, introducing an error into the seismograms. By systematically increasing the number of modes beyond the highest frequency of interest in the seismograms, we investigate the convergence of full-coupling calculations. As a rule-of-thumb, it is necessary to couple modes 1–2 mHz above the highest frequency of interest, although results depend upon the details of the Earth model. This is significantly higher than has previously been assumed. Observations of free oscillations also provide important constraints on the heterogeneous structure of the Earth. Historically, this inference problem has been addressed by the measurement and interpretation of splitting functions. These can be seen as secondary data extracted from low frequency seismograms. The measurement step necessitates the calculation of synthetic seismograms, but current implementations rely on approximations referred to as self- or group-coupling and do not use fully accurate seismograms. We therefore also investigate whether a systematic error might be present in currently published splitting functions. We find no evidence for any systematic bias, but published uncertainties must be doubled to properly account for the errors due to theoretical omissions and regularization in the measurement process. Correspondingly, uncertainties in results derived from splitting functions must also be increased. As is well known, density has only a weak signal in low-frequency seismograms. Our results suggest this signal is of similar scale to the true uncertainties associated with currently published splitting functions. Thus, it seems that great care must be taken in any attempt to robustly infer details of Earth's density structure using current splitting functions.

Efficient wave propagation simulation on quadtree meshes using SBFEM with reduced modal basis

SummaryWe apply a combination of the transient scaled boundary finite element method (SBFEM) and quadtree‐based discretization to model dynamic problems at high frequencies. We demonstrate that the current formulation of the SBFEM for dynamics tends to require more degrees of freedom than a corresponding spectral element discretization when dealing with smooth problems on regular domains. Thus, we improve the efficiency of the SBFEM by proposing a novel approach to reduce the number of auxiliary variables for transient analyses. Based on this improved SBFEM, we present a modified meshing procedure, which creates a quadtree mesh purely based on the geometry and allows arbitrary sizes and orders of elements, as well as an arbitrary number of different materials. The discretization of each subdomain is created automatically based on material parameters and the highest frequency of interest. The transition between regions of different properties is straightforward when using the SBFEM. The proposed approach is applied to image‐based analysis with a particular focus on geological models. Copyright © 2016 John Wiley & Sons, Ltd.

Wideband analysis of planar scalable antennas and PEC bodies using CBFM

In this paper, scattering and radiation from scalable planar bodies are investigated in a wide frequency band. Characteristic basis functions (CBFs) are utilized for this purpose with a different approach. The CBFs for the body are calculated at the highest frequency of interest and reused at other frequencies. As the frequency decreases, the unnecessary CBFs are removed from the basis set. The reduced impedance matrices generated at lower frequencies are also used for the calculation of the ones at higher frequencies. As a result, a signicant reduction in CPU time is obtained with the proposed method. Numerical results for the problems of scattering from a square plate and radiation from a bowtie antenna are presented to demonstrate the accuracy and efficiency of the proposed method.

Development of a Second-Generation Underwater Acoustic Ambient Noise Imaging Camera

A nominally circular 2-D broadband acoustic array of 1.3-m diameter, comprising 508 sensors and associated electronics, was designed, built, and tested for ambient noise imaging (ANI) potential in Singapore waters. The system, named Remotely Operated Mobile Ambient Noise Imaging System (ROMANIS), operates over 25–85 kHz, streaming real-time data at 1.6 Gb/s over a fiber optic link. By using sensors that are much larger than half-wavelength at the highest frequency of interest, so with some directionality, good beamforming performance is obtained with a small number of sensors compared to a conventional half-wavelength-spaced array. A data acquisition system consisting of eight single-board computers enables synchronous data collection from all 508 sensors. A dry-coupled neoprene cover is used to encapsulate the ceramic elements as an alternative to potting or oil filling, for easier maintenance. Beamforming is performed in real-time using parallel computing on a graphics processing unit (GPU). Experiments conducted in Singapore waters yielded images of underwater objects at much larger ranges and with better resolution than any previous ANI system. Although ROMANIS was designed for ANI, the array may be valuable in many other applications requiring a broadband underwater acoustic receiving array.

Correcting EM system bandwidth limitations

All EM transmitters, sensors and data acquisition systems have bandwidth limitations. Transmitters have upper bandwidth limitations due to finite slew rate issues, and systems have a lower bandwidth set by the base frequency used. Receivers and data acquisition systems ideally should have a flat bandwidth response that spans the transmitted signal bandwidth. The data acquisition system should sample fast enough to capture the highest frequencies of interest, with anti-alias filters to prevent data contamination from unwanted signals. Sensors however may have physical bandwidth limitations, for example fluxgates and feedback MT sensors may have an upper corner frequency of a few kHz, and ARMIT and feedback MT sensors have lower corner frequencies in the sub 1 Hz range. In many cases, the sensor corner frequency can be mathematically described as a single- or multi-pole response. In this case, it is possible to exactly deconvolve the data to exactly correct for the sensor imperfection. A limitation of this process is that noise as well as signal may be amplified in this correction process. Without correction, data may be incorrectly modelled or interpreted. This paper illustrates the correction of fluxgate (mostly a time delay of hundred or more microseconds), ARMIT 2 (where a significant but exact correction is required), ANT23 feedback and 3D3 dBdt data.

Next generation full-wave ultrasound simulation: Exploiting parallelism in the move toward exascale

In recent years, the capability of performing 3D full-wave nonlinear ultrasound simulations in tissue-realistic media has been demonstrated by a number of groups. These models have since underpinned a range of interesting studies into the interaction of ultrasound fields with the human body. However, simulations have thus far been limited to domain sizes on the order of 1 billion grid points. This limitation usually means either the spatial area or highest frequency of interest is truncated. Looking toward the exascale era, where supercomputers integrating over 1M cores are predicted to appear before 2020, there is a significant opportunity to use models to gain new insight into ultrasound-tissue interaction with unprecedented detail. The challenge is to develop suitable numerical methods that map to these massively parallel architectures, in particular, that minimize data movement, allow the exploitation of co-processors, and minimize the accumulation of numerical errors. Here, we show a novel domain decomposition approach for the Fourier collocation spectral method that allows ultrasound simulations to be distributed across up to 32k CPU cores or hundreds of accelerators with reasonable efficiency. Using this model, we demonstrate for the first time the possibility of ultrasound simulations exceeding 70 billion grid points.

A combined method for computing frequency responses of proportionally damped systems

Frequency response analysis requires the evaluation of an associated function for a typically large number of frequencies. Direct method for performing these calculations is time-consuming. In this paper, a method is proposed for solving frequency responses of a mechanical system with proportional damping. The method combines modal superposition with a model order reduction. Only the modes corresponding to a frequency range which is a little bigger than that of interest are used for modal superposition. Complementary part of contribution of computed modes for frequency response is calculated by a model order reduction method. Basis vectors are obtained by applying preconditioned conjugate gradient method to a modified undamped system at the highest frequency of interest. The existing factorized stiffness matrix developed for partial eigensolutions is used as preconditioner. This computational methodology is illustrated by its applications to two frequency response problems. It is shown that the present method can remarkably reduce the CPU time required by the direct method to frequency response analysis.

Optimization of a 100 MHz fiber optic hydrophone for medical ultrasound applications using nanometer scale gold coating.

This work describes a novel numerical model developed to optimize the design of a broadband, spatial averaging free fiber optic hydrophone probe (FOHP) for characterization of ultrasound fields in the frequency range 1–100 MHz. The design included minimization of the active sensor dimensions, so its cross-section is comparable with the half acoustic wavelength at the highest frequency of interest and improvement of voltage-to-pressure sensitivity of the probe measured in V/Pa. Initial simulations based on the assumption that bulk refractive index of sputtered material could be used indicated that a thin film gold coating (1–35 nm) could indeed enhance the voltage sensitivity of the FOHP by 16–30 dB; however, a follow up analysis revealed that determination of the coating thickness influence on the FOHP performance would require an introduction of the complex (as opposed to bulk) index of refraction of the sputtered film. The input parameters to the model, their selection criteria, and implementation of the coupled acousto-optic interaction of gold layer will be discussed. The measured prototypes produced unprecedented voltage sensitivity between −234 and −245 dB re 1 V per uPa or 2 and 560 mV/MPa, respectively. [The authors wish to acknowledge support of the NIH R01EB007117 grant.]

Best Practices for Accurate Measurement of Pure Jet Noise

This paper focuses on the best practices that would ensure the vital requirement of accurate measurements of clean jet noise spectra at all frequencies. Issues that are important for jet aeroacoustic tests and the critical role of good data in the development of jet noise technology are examined. Problems with both the jet rig and the instrumentation system could severely compromise the data quality, thereby rendering the measured data unsuitable for scientific and technical applications. The limitations of the instrumentation system are discussed, and a set of recommendations that would lead to clean measurements at the higher frequencies of interest in model tests is provided. Methods for verifying the quality of data, from both single and dual-stream jets, are described in depth. Some of the existing beliefs and approaches for checking data quality are shown to be without merit. It is more difficult to measure pure jet noise from very large nozzles especially at low jet velocities, with a given compact rig. The objectives of an aeroacoustic test should be understood clearly and proper choice of nozzle configurations made to avoid acquiring data corrupted by extraneous noise. This is especially so for typical dual-stream geometries, where the secondary jet generates the high-frequency noise. The consequences of contaminated data in the development of noise reduction technology and theories are highlighted. The results from a major effort for improving the quality of aeroacoustic data acquired at the Boeing Low Speed Aeroacoustic Facility (LSAF) are reported: significant improvements have been made to the flow quality and acoustics. The high quality of noise measurements, as a result of the refurbishment, is established through good spectral agreement with data obtained with a blow-down jet, for a wide range of nozzle conditions. Much of the existing data have been found to be corrupted; it is incumbent upon the experimental community to produce unambiguous data that would advance the state-of-the-art in jet noise technology.

Age- and Fatigue-related Markers of Human Faces: An Eye-Tracking Study

To investigate the facial cues that are used when making judgments about how old or tired a face appears. Experimental study. Forty-seven subjects: 15 male and 32 female participants, ranging from age 18 to 30 years. Forty-eight full-face digital images of "normal-appearing" patients were collected and uploaded to an eye-tracking system. We used an Applied Science Laboratories (Bedford, MA) Eye Tracker device associated with gaze-tracking software to record and calculate the gaze and fixation of the participants' left eye as they viewed images on a computer screen. After seeing each picture, participants were asked to assess the age of the face in the picture by making a selection on a rating scale divided into 5-year intervals; for fatigue judgments we used a rating scale from 1 (not tired) to 7 (most tired). The main outcome measure was gaze fixation, as assessed by tracking the eye movements of participants as they viewed full-face digital pictures. For fatigue judgments, participants spent the most time looking at the eye region (31.81%), then the forehead and the nose regions (14.99% and 14.12%, respectively); in the eye region, participants looked most at the brows (13.1%) and lower lids (9.4%). Participants spent more time looking at the cheeks on faces they rated as least tired than they did on those they rated as most tired (t = 2.079, P<0.05). For age judgments, the eye region (27.22%) and then the forehead (15.71%) and the nose (14.30%) had the highest frequencies of interest; in the eye region, the brows and lower lids also had the highest frequencies of interest (11.40% and 8.90%, respectively). Participants looked more at the brows (t = -2.63, P<0.05) and glabella (t = -3.28, P<0.01) in those faces they rated as looking the oldest. This study supports the hypothesis that age and fatigue judgments are related to preferential attention toward the eye region. Consequently, these results suggest that aesthetic or functional surgery to the eye region may be one of the most effective interventions in enhancing the appearance of an individual. The author(s) have no proprietary or commercial interest in any materials discussed in this article.

The low-frequency sound speed of fluid-like gas-bearing sediments

The low-frequency sound speed in a fluid-like kaolinite sediment containing air bubbles was measured using an acoustic resonator technique and found to be 114 ms with negligible dispersion between 100 and 400 Hz. The sediment's void fraction and bubble size distribution was determined from volumetric images obtained from x-ray computed tomography scans. A simplified version of Wood's effective medium model, which is dependent only upon the ambient pressure, the void fraction, the sediment's bulk mass density, and the assumption that all the bubbles are smaller than resonance size at the highest frequency of interest, described the measured sound speed.

Does a Model-Scale Nozzle Emit the Same Jet Noise as a Jet Engine?

A careful experimental study has been carried out to verify whether a model-scale nozzle produces the same jet noise as a jet engine, with the twin goals of 1) validating the practice of carrying out jet noise research at model scale for full-scale applications, and 2) aiding the identification of jet noise in measured total spectra from jet engines, which have contributions from several noise sources. A special test was carried out to measure pure jet noise from a low-bypass ratio jet engine at all the angles. Aeroacoustic measurements were made from model-scale nozzles at the Boeing Low-Speed Aeroacoustic Facility at the same operating conditions as the jet engine. Many issues that are pertinent for the comparison of scaled model data with engine data have been investigated thoroughly. These include the requirements of the instrumentation system for model and engine tests, suitable methodology for the calculation of the atmospheric attenuation coefficients, propagation effects, data repeatability, scaling of jet noise spectra, effects of the disparate Reynolds numbers and mixing perimeters between model nozzles and engines, etc. The data indicate that the weather corrections are accurate even at very high frequencies of interest in model tests. A new phenomenon of nonlinear propagation effects is identified for subsonic heated jets when the convective Mach number exceeds unity. The convective Mach number is shown to be a better indicator of nonlinear processes than high sound amplitudes,as has been believed in the past As demonstrated, with the proper scaling factors, both narrowband and one-third-octave jet spectra can be collapsed. The concept of increasing the shear perimeter for achieving better mixing and hence reducing noise has no merit, even at supercritical pressure ratios. Excellent agreement between scaled model and engine spectra is demonstrated at all angles and frequencies for a variety of power levels; thus, it is possible to acquire high-quality spectra at high frequencies, provided proper care is taken. Finally, the major conclusion from the preceding results is that jet noise research carried out at model scale is applicable to jet engines.

Cable transient voltages due to microphonics

Expressions for the voltage generated by tribocharging between a cable's dielectric and outer conductor, and the maximum voltage across a resistive load of a cable, are derived as a function of time. For a reasonably large load resistance and cable capacitance, the expressions reduce to simple single-time-constant equations that can be used to estimate the highest frequency of interest of the generated noise. The derived expressions can also assist the designer in weighing the tradeoffs associated with changing the ohmic resistance and capacitance of low-noise cables.

Effect of Probe Tube Insertion Depth on Spectral Measures of Speech

This study investigated how depth variations in the tip of the probe tube affected spectral measures of speech recorded in the external ear canal. Consonant-vowel nonsense syllables were recorded with a probe tube microphone system in 10 adult participants with normal middle ear function. Recordings were made with the probe tube tip placed 1 mm, 5 mm, and 10 mm beyond the medial tip of a custom earmold. The effect of probe depth was evaluated on spectral levels (one-third octave and one- twelfth octave band). Extending the probe tube 10 mm past the medial tip of the earmold gave the most accurate results, with relatively lower sound levels for either the 1-mm or 5-mm insertion depth. In general, the effect of insertion depth was minimal at frequencies below 3 to 4 kHz, although this varied with the specific phoneme and the width of the analysis bands. The authors found no significant difference between 1- and 5-mm insertion depths, suggesting that as long as the tip of the probe tube is sufficiently close to the tympanic membrane to capture the highest frequency of interest, it makes little difference if it is less than 5 mm beyond the earmold tip.

A derived physically expressive circuit model for multilayer RF embedded passives

In this paper, a derived physically expressive circuit model is presented for automatically deriving an equivalent-circuit model of a multilayered embedded RF passive. The scheme is based on the partial-element equivalent-circuit (PEEC) model and a simple circuit transformation. By defining an appropriate cutoff criterion that is related to the highest frequency of interest, most of the internal nodes in the coupling circuit generated by the PEEC model can be approximately absorbed by the remaining frequency-independent LC elements progressively. The model is very simple to implement and has apparent physical meaning. Mathematically, this model progressively recombines the least significant system pole with other less significant poles. The resultant physically expressive circuit model will be very useful in designing multilayer embedded RF circuits. Four examples are given for demonstrating the validity and effectiveness of the scheme.

Modeling of received signals from annular array ultrasound transducers due to extended reflectors.

This paper describes a computationally efficient numerical technique for calculating the received signal from a broadband annular array transducer operating in pulse-echo mode, due to a specified reflector. The technique is referred to as the Diffraction Response from Extended Area Method (DREAM) and operates by tessellating the reflector into planar tiles with a dimension of several wavelengths (at the highest frequency of interest) and finding the contribution from a given tile by a temporal low-pass filtering rather than spatial integration. In particular, this paper formulates the theory for the DREAM for tessellation into triangular tiles and demonstrates the improved performance with triangular tiles relative to square tiles. This paper also analyzes the mean square error of the received signal as a function of the diameters of the transmitting and the receiving transducers and the radial position and orientation of the tile. Based on this, a set of rules for the optimal tile size is developed. The power of the modeling technique is demonstrated by calculating the received signal from an annular array transducer due to three given extended reflectors in which the effect of the focal point location on the received signal is readily demonstrated.