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Journal articles on the topic 'Directivity effects'

Author: Grafiati

Published: 4 June 2021

Last updated: 18 February 2022

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1

Xie, Junju. "Strong‐Motion Directionality and Evidence of Rupture Directivity Effects during the Chi‐Chi Mw 7.6 Earthquake." Bulletin of the Seismological Society of America 109, no. 6 (October 29, 2019): 2367–83. http://dx.doi.org/10.1785/0120190087.

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Abstract This article investigates the spatial distribution, predominant direction, and variations in the intensity measures (IMs) with orientation for classified pulse‐like and nonpulse motions during Chi‐Chi Mw 7.6 earthquake. The results show evidence of high polarization for long‐period spectral accelerations at relatively large source‐to‐site distances (50–100 km) north of the Chelungpu fault. The polarization of long‐period motions shows a clear correlation with the directivity parameters’ isochrone directivity predictor and ξ, indicating a connection between directionality and rupture directivity. The variation in strong‐motion directionality with the period is also studied. The discrepancy in directionality caused by strong directivity increases with the period from 1 to 10 s, which confirms a clear correlation of period‐dependent directionality with directivity effects. This study finds stronger directionality of pulse‐like motions than nonpulse motions for long periods over 3 s with higher maximum‐to‐median and maximum‐to‐minimum IM ratios. For periods over 3 s, the maximum‐to‐median ratios of pulse‐like motions are higher than the mean prediction of the Shahi and Baker (2014a) model, whereas those of nonpulse motions are lower than the prediction. However, this study does not find simple and clear results for the directions of the maximum component at different periods for pulse‐like and nonpulse motions. Despite clear differences between the unidirectional fling‐step and bidirectional forward directivity pulses, the effects of fling‐step and forward directivity are actually coupled in the waveforms.

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2

Nakazawa, Toshiyasu, and Naoaki Shinohara. "Study on aircraft noise directivity of behind the start of takeoff roll." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, no. 3 (August 1, 2021): 3202–8. http://dx.doi.org/10.3397/in-2021-2330.

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This paper discusses aircraft noise directivity behind the start of takeoff roll. Aircraft noise has the radiation directivity because of aircraft engine mount position and the engine noise directivity. Thus, lateral noise directivity correction is recommended in airport noise calculation guidelines such as ECAC Doc.29 and ICAO Doc9911. In these guidelines, the directivity of flyover noise and the directivity at the start of takeoff roll on ground are prepared separately. A 90-degree dipole model is used for the directivity of the flyover noise, and another similar directivity is used for the directivity behind the start of takeoff roll. It is necessary to properly evaluate the directivity behind the takeoff roll because it has a large contribution to noise calculation of the vicinity of the airport. Therefore, we measured aircraft noise behind the start of takeoff roll with sound level meters placed half-concentrically around Narita Airport in Japan. From these measurement results, various types of aircraft noise directivity behind the takeoff roll are examined and considered the effects of weather conditions such as wind direction. Finally the differences from existing models are compared.

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3

Sheets, Nathan W., and Lily M. Wang. "Effects of sound source directivity on auralizations." Journal of the Acoustical Society of America 111, no. 5 (2002): 2331. http://dx.doi.org/10.1121/1.4777773.

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4

Tarbali, Karim, Brendon A. Bradley, and Jack W. Baker. "Ground Motion Selection in the Near-Fault Region considering Directivity-Induced Pulse Effects." Earthquake Spectra 35, no. 2 (May 2019): 759–86. http://dx.doi.org/10.1193/102517eqs223m.

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This paper focuses on the selection of ground motions for seismic response analysis in the near-fault region, where directivity effects are significant. An approach is presented to consider forward directivity velocity pulse effects in seismic hazard analysis without separate hazard calculations for ‘pulse-like’ and ‘non-pulse-like’ ground motions, resulting in a single target hazard (at the site of interest) for ground motion selection. The ability of ground motion selection methods to appropriately select records that exhibit pulse-like ground motions in the near-fault region is then examined. Applications for scenario and probabilistic seismic hazard analysis cases are examined through the computation of conditional seismic demand distributions and the seismic demand hazard. It is shown that ground motion selection based on an appropriate set of intensity measures (IMs) will lead to ground motion ensembles with an appropriate representation of the directivity-included target hazard in terms of IMs, which are themselves affected by directivity pulse effects. This alleviates the need to specify the proportion of pulse-like motions and their pulse periods a priori as strict criteria for ground motion selection.

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5

Spudich, Paul, Badie Rowshandel, Shrey K. Shahi, Jack W. Baker, and Brian S. J. Chiou. "Comparison of NGA-West2 Directivity Models." Earthquake Spectra 30, no. 3 (August 2014): 1199–221. http://dx.doi.org/10.1193/080313eqs222m.

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Five directivity models have been developed based on data from the NGA-West2 database and based on numerical simulations of large strike-slip and reverse-slip earthquakes. All models avoid the use of normalized rupture dimension, enabling them to scale up to the largest earthquakes in a physically reasonable way. Four of the five models are explicitly “narrow-band” (in which the effect of directivity is maximum at a specific period that is a function of earthquake magnitude). Several strategies for determining the zero-level for directivity have been developed. We show comparisons of maps of the directivity amplification. This comparison suggests that the predicted geographic distributions of directivity amplification are dominated by effects of the models’ assumptions, and more than one model should be used for ruptures dipping less than about 65 degrees.

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6

Hidayah Muhamad Adnan, Noor, Islam Md. Rafiqul, and AHM Zahirul Alam. "Effects of Inter-Element Spacing and Number of Elements on Planar Array Antenna Characteristics." Indonesian Journal of Electrical Engineering and Computer Science 10, no. 1 (April 1, 2018): 230. http://dx.doi.org/10.11591/ijeecs.v10.i1.pp230-240.

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<p>Planar array antenna is seen as one of the innovative solutions of massive MIMO and 5G networks since they provide directive beams. In this paper, planar array antenna with square and rectangular arrangements based on 2 x 2 antenna elements as one subarray was proposed. Then, array factor for the the planar array antenna with up to 64 antenna elements was calculated to analyze the effects of inter-element spacing and number of elements on the antenna characteristics. Higher values of inter-element spacing contributed to higher number of side lobes, narrower main lobe, higher directivity and lower half power beamwidth (HPBW). Inter-element spacing equals to 0.5λ was found to be the most suitable value for planar array antenna design based on the analysis. Meanwhile, higher number of antenna elements increased the value of directivity of the planar array with narrower HPBW. Therefore, there is a tradeoff between directivity and HPBW in designing planar array antenna for massive MIMO application. </p><p> </p>

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7

Ricketts, Todd. "Directivity Quantification in Hearing Aids: Fitting and Measurement Effects." Ear and Hearing 21, no. 1 (February 2000): 45–58. http://dx.doi.org/10.1097/00003446-200002000-00008.

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8

Shahbazi, Shahrokh, Iman Mansouri, Jong Wan Hu, Noura Sam Daliri, and Armin Karami. "Seismic Response of Steel SMFs Subjected to Vertical Components of Far- and Near-Field Earthquakes with Forward Directivity Effects." Advances in Civil Engineering 2019 (April 3, 2019): 1–15. http://dx.doi.org/10.1155/2019/2647387.

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In the near-field earthquake, forward directivity effects cause long-period pulse with a short effective time and a large domain in the velocity time history. This issue increases the ductility needs of structures, and in recent decades, the destructive effects of these kinds of records have been evaluated in comparison with far-field earthquakes. This brings about the necessity to compare a structure’s behavior subjected to vertical components of near-field (NF) earthquakes, including forward directivity effects vs. the effects of vertical components of far-field (FF) earthquakes. The present study investigated 3-, 5-, 8-, and 20-story steel moment frames with special ductility (SMF) through which modeling effects of panel zone have been applied, subjected to vertical component of near-field (NF) earthquakes with forward directivity and the vertical component of far-field earthquakes. By investigating the results, it can be clearly seen that the average values of the maximum displacement, shear force of the stories, and the velocity of each story under the impact of the near-field earthquake are greater than the amount of that under the effect of a far-field earthquake. However, this comparison is not valid for the amount of acceleration, axial force, and moments in the columns of the structures accurately.

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9

Sugar, Mitchell, and Paul Slaboch. "Directivity of sound propagation from an commercial supersonic engine inlet." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, no. 2 (August 1, 2021): 4211–18. http://dx.doi.org/10.3397/in-2021-2633.

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The effects of mean flow variations on sound propagation from an axisymmetric commercial supersonic engine inlet were studied using numerical methods. A finite element model of the inlet was constructed in Ansys Fluent and used to solve for flow fields given by different initial conditions. Results from this model were fed into the aeroacoustic solver, Actran, and used to calculate far field radiated noise as well as the directivity of that noise. The acoustic source of this noise was a plane wave of a known strength placed at the fan face. In addition to assessing the effects of mean flow on the radiated noise transfer functions, the duct modes of the model were compared across different flow regimes. Relationships between mean flow parameters and the directivity of duct modes are developed. The results of this study will be used in further studies to gain a deeper understanding of how the underlying physics which govern the system create favorable or unfavorable directivity patterns.

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10

Ertuncay, Deniz, Petra Malisan, Giovanni Costa, and Stefano Grimaz. "Impulsive Signals Produced by Earthquakes in Italy and Their Potential Relation with Site Effects and Structural Damage." Geosciences 11, no. 6 (June 21, 2021): 261. http://dx.doi.org/10.3390/geosciences11060261.

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Near fault seismic records may contain impulsive motions in velocity-time history. The seismic records can be identified as impulsive and non-impulsive depending on the features that their waveforms have. These motions can be an indicator of directivity or fling step effect, and they may cause dangerous effects on structures; for this reason, there is increasing attention on this subject in the last years. In this study, we collect the major earthquakes in Italy, with a magnitude large or equal to Mw 5.0, and identify the impulsive motions recorded by seismic stations. We correlate impulsive motions with directivity and fling step effects. We find that most earthquakes produced impulsive signals due to the directivity effect, though those at close stations to the 30 October 2016 Amatrice earthquake might be generated by the fling step effect. Starting from the analyzed impulses, we discuss on the potential influence of site effects on impulsive signals and suggest a characterization based on the main displacement directions of the impulsive horizontal displacements. Finally, we discuss on the damage of three churches in Emilia, which were subject to impulsive ground motion, underlying in a qualitative way, how the characteristics of the pulses may have had influences the structural response of the façades.

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11

Wang, Jishuo, Caibin Xu, Youxuan Zhao, Ning Hu, and Mingxi Deng. "Characterization of Microcrack Orientation Using the Directivity of Secondary Sound Source Induced by an Incident Ultrasonic Transverse Wave." Materials 13, no. 15 (July 25, 2020): 3318. http://dx.doi.org/10.3390/ma13153318.

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In this paper, characterization of the orientation of a microcrack is quantitatively investigated using the directivity of second harmonic radiated by the secondary sound source (SSS) induced by the nonlinear interaction between an incident ultrasonic transverse wave (UTW) and a microcrack. To this end, a two-dimensional finite element (FE) model is established based on the bilinear stress–strain constitutive relation. Under the modulation of contact acoustic nonlinearity (CAN) to the incident UTW impinging on the microcrack examined, the microcrack itself is treated as a SSS radiating the second harmonic. Thus, the directivity of the second harmonic radiated by the SSS is inherently related to the microcrack itself, including its orientation. Furthermore, the effects of the stiffness difference between the compressive and tensile phases in the bilinear stress–strain model, and the UTW driving frequency, as well as the radius of the sensing circle on the SSS directivity are discussed. The FE results show that the directivity pattern of the second harmonic radiated by the SSS is closely associated with the microcrack orientation, through which the microcrack orientation can be characterized without requiring a baseline signal. It is also found that the SSS directivity varies sensitively with the driving frequency of the incident UTW, while it is insensitive to the stiffness difference between the compressive and tensile phases in the bilinear stress–strain model and the radius of the sensing circle. The results obtained here demonstrate that the orientation of a microcrack can be characterized using the directivity of the SSS induced by the interaction between the incident UTW and the microcrack.

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12

Hustedt, Bernhard, and Roger A. Clark. "Source/receiver array directivity effects on marine seismic attenuation measurements." Geophysical Prospecting 47, no. 6 (November 1999): 1105–19. http://dx.doi.org/10.1046/j.1365-2478.1999.00169.x.

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13

Brummitt, J. G. "Source Directivity and its Effects on Resolution and Signature Deconvolution." Exploration Geophysics 19, no. 1-2 (March 1988): 237–40. http://dx.doi.org/10.1071/eg988237.

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14

Every, A. G. "A model for calculating surface directivity effects in phonon imaging." Solid State Communications 57, no. 8 (February 1986): 691–93. http://dx.doi.org/10.1016/0038-1098(86)90352-2.

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15

Tam, Christopher K. W., Sarah A. Parrish, Edmane Envia, and Eugene W. Chien. "Physical processes influencing acoustic radiation from jet engine inlets." Journal of Fluid Mechanics 725 (May 14, 2013): 152–94. http://dx.doi.org/10.1017/jfm.2013.181.

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AbstractNumerical simulations of acoustic radiation from a jet engine inlet are performed using advanced computational aeroacoustics algorithms and high-quality numerical boundary treatments. As a model of modern commercial jet engine inlets, the inlet geometry of the NASA Source Diagnostic Test is used. Fan noise consists of tones and broadband sound. This investigation considers the radiation of tones associated with upstream-propagating duct modes. The primary objective is to identify the dominant physical processes that determine the directivity of the radiated sound. Two such processes have been identified. They are acoustic diffraction and refraction. Diffraction is the natural tendency for an acoustic duct mode to follow a curved solid surface as it propagates. Refraction is the turning of the direction of propagation of a duct mode by mean flow gradients. Parametric studies on the changes in the directivity of radiated sound due to variations in forward flight Mach number, duct mode frequency, azimuthal mode number and radial mode number are carried out. It is found there is a significant difference in directivity for the radiation of the same duct mode from an engine inlet when operating in static condition versus one in forward flight. It will be shown that the large change in directivity is the result of the combined effects of diffraction and refraction.

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16

ROUSE, JERRY, and LINDA FRANZONI. "IMPROVEMENT OF A HIGH-FREQUENCY BROADBAND ENERGY-INTENSITY BOUNDARY ELEMENT METHOD TO INCLUDE HIGH RESOLUTION SPECULAR REFLECTION." Journal of Computational Acoustics 13, no. 01 (March 2005): 99–125. http://dx.doi.org/10.1142/s0218396x05002542.

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The prediction of the spatial mean-square pressure distribution within enclosed high-frequency broadband sound fields is computationally intensive if determined on a frequency-by-frequency basis. Recently an energy-intensity boundary element method (EIBEM) has been formally developed. This method employs uncorrelated broadband directional energy sources to expeditiously predict such pressure distributions. The source directivity accounts for local correlation effects and specular reflection. The method is applicable to high modal density fields, but not restricted to the usual low-absorption, diffuse, and quasi-uniform assumptions. The approach can accommodate fully specular reflection, or any combination of diffuse and specular reflection. This boundary element method differs from the classical version in that element size is large compared to an acoustic wavelength and equations are not solved on a frequency-by-frequency basis. In the earlier EIBEM, the source strength and directivity associated with the energy sources, distributed over enclosure boundaries, were determined in an iterative manner and the directivity was limited to three terms of a Fourier expansion. Here, the original method is improved by eliminating the iteration and allowing for an unlimited number of terms in the Fourier expansion of the directivity function. For verification, the improved EIBEM is compared to experimental measurements and exact analytical solutions; excellent agreement is obtained.

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17

HAYAKAWA, Takashi, and Atsuko OANA. "INCORPORATING RUPTURE DIRECTIVITY EFFECTS INSIDE SUBFAULTS IN STOCHASTIC GREEN'S FUNCTION METHOD." Journal of Structural and Construction Engineering (Transactions of AIJ) 85, no. 775 (2020): 1145–55. http://dx.doi.org/10.3130/aijs.85.1145.

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18

Khoshnoudian, Faramarz, Reza Attarnejad, Ehsan Ahmadi, and Farzane Paytam. "Effects of forward directivity on the response of soil–structure systems." Proceedings of the ICE - Structures and Buildings 168, no. 9 (September 1, 2015): 664–79. http://dx.doi.org/10.1680/stbu.13.00076.

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19

KANNO, Tatsuo, and Kenji MIURA. "NEAR-FAULT RUPTURE DIRECTIVITY EFFECTS ON CHARACTERISTICS OF STRONG GROUND MOTIONS." Journal of Structural and Construction Engineering (Transactions of AIJ) 71, no. 610 (2006): 191–96. http://dx.doi.org/10.3130/aijs.71.191.

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20

Khoshnoudian, Faramarz, Reza Attarnejad, Farzane Paytam, and Ehsan Ahmadi. "Effects of forward directivity on the response of soil–structure systems." Proceedings of the Institution of Civil Engineers - Structures and Buildings 168, no. 9 (September 2015): 664–79. http://dx.doi.org/10.1680/jstbu.13.00076.

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21

Gerami, Mohsen, and Davood Abdollahzadeh. "Vulnerability of steel moment-resisting frames under effects of forward directivity." Structural Design of Tall and Special Buildings 24, no. 2 (March 3, 2014): 97–122. http://dx.doi.org/10.1002/tal.1156.

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22

Sorensen, Kristina M., Nicholas J. Eyring, Timothy W. Leishman, and Nathan G. W. Eyring. "On the directivity of musical instruments: Effects on room acoustics calculations." Journal of the Acoustical Society of America 130, no. 4 (October 2011): 2430. http://dx.doi.org/10.1121/1.3654745.

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23

Gordo-Monsó, Carlos, and Eduardo Miranda. "Significance of directivity effects during the 2011 Lorca earthquake in Spain." Bulletin of Earthquake Engineering 16, no. 7 (January 8, 2018): 2711–28. http://dx.doi.org/10.1007/s10518-017-0301-9.

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24

Berge, Catherine, André Herrero, Pascal Bernard, Myriam Bour, and Pascal Dominique. "The Spectral Source Model: A Tool for Deterministic and Probabilistic Seismic Hazard Assessment." Earthquake Spectra 14, no. 1 (February 1998): 35–57. http://dx.doi.org/10.1193/1.1585987.

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Seismic-hazard assessment at small scales requires the computation of realistic broad-band accelerograms near the sources. Methods that use only natural records are often limited because of the limited data set. Among recently developed methods for source modelling, the spectral-source model, based on the k−2 dislocation distribution seems particularly promising as it enables computation of synthetics for any source-receiver distance and directivity configuration. The spectral model takes into account important source characteristics, such as stress drop and directivity effects predicting acceptable high-frequency levels, whatever the station location (Bernard et al., 1996b). Firstly, some tests to explain the directivity properties of the model are presented, followed by the main results of a deterministic study carried out for the 1992 Erzincan earthquake, Turkey. Finally, results of a probabilistic study in the Moyenne-Durance region (France) are used to demonstrate the ability of this method to produce seismic-hazard maps and spectra linked to a specific return period.

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25

Baumeister, K. J. "Reverberation Effects on Directionality and Response of Stationary Monopole and Dipole Sources in a Wind Tunnel." Journal of Vibration and Acoustics 108, no. 1 (January 1, 1986): 82–90. http://dx.doi.org/10.1115/1.3269307.

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Analytical solutions for the three-dimensional inhomogeneous wave equation with flow in a hardwall rectangular wind tunnel and in the free field are presented for a stationary monopole noise source. Dipole noise sources are calculated by combining two monopoles 180 deg out of phase. Numerical calculations for the modal content, spectral response and directivity for both monopole and dipole sources are presented. In addition, the effect of tunnel alterations, such as the addition of a mounting plate, on the tunnels reverberant response are considered. In the frequency range of practical importance for the turboprop response, important features of the free field directivity can be approximated in a hardwall wind tunnel with flow if the major lobe of the noise source is not directed upstream. However, for an omnidirectional source, such as a monopole, the hardwall wind tunnel and free field response will not be comparable.

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26

Jei, Yang-Gyu, and Young-Ju Kim. "Modal Testing Theory of Rotor-Bearing Systems." Journal of Vibration and Acoustics 115, no. 2 (April 1, 1993): 165–76. http://dx.doi.org/10.1115/1.2930327.

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Since all dynamic characteristics of rotor systems are closely related with rotor rotations, the directivity of modes is very important in rotor dynamics. But the classical modal testing theories which have been applied to nonrotating structures were often applied to rotor systems. Whereas the dynamic characteristics in negative frequency region have no meanings in nonrotating stuctures, the dynamic characteristics of rotor systems in the negative frequency region which are different from those in the positive frequency region have significant physical meanings. Here a new modal testing theory is proposed to separate the rotor vibration into positive and negative frequency regions. In particular, the amplitude and directivity variations of frequency response functions in positive and negative frequency regions are discussed when using complex modal displacement. And a method to identify the directivity of modes such as forward and backward is suggested using the frequency response function obtained by the proposed modal testing theory. The whirl directions of forced responses related with the directivity of modes are also discussed. In addition, even if the anisotropy in bearings and the effects of gyroscopic moments are permitted, the relations between the right and left eigenvectors of general damped anisotropic rotor systems are evaluated under some practical conditions. If the relations between the right and left eigenvectors are given, the necessity of additional modal testing to identify the adjoint modal parameters is relaxed.

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27

Kalkan, Erol, and Sashi K. Kunnath. "Effects of Fling Step and Forward Directivity on Seismic Response of Buildings." Earthquake Spectra 22, no. 2 (May 2006): 367–90. http://dx.doi.org/10.1193/1.2192560.

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This paper investigates the consequences of well-known characteristics of near-fault ground motions on the seismic response of steel moment frames. Additionally, idealized pulses are utilized in a separate study to gain further insight into the effects of high-amplitude pulses on structural demands. Simple input pulses were also synthesized to simulate artificial fling-step effects in ground motions originally having forward directivity. Findings from the study reveal that median maximum demands and the dispersion in the peak values were higher for near-fault records than far-fault motions. The arrival of the velocity pulse in a near-fault record causes the structure to dissipate considerable input energy in relatively few plastic cycles, whereas cumulative effects from increased cyclic demands are more pronounced in far-fault records. For pulse-type input, the maximum demand is a function of the ratio of the pulse period to the fundamental period of the structure. Records with fling effects were found to excite systems primarily in their fundamental mode while waveforms with forward directivity in the absence of fling caused higher modes to be activated. It is concluded that the acceleration and velocity spectra, when examined collectively, can be utilized to reasonably assess the damage potential of near-fault records.

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28

Pasku, Valter, Mario Luca Fravolini, and Antonio Moschitta. "Effects of antenna directivity on RF ranging when using space diversity techniques." Measurement 98 (February 2017): 429–38. http://dx.doi.org/10.1016/j.measurement.2015.11.030.

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29

Esplin, J. James, Brian T. Thornock, and Timothy W. Leishman. "The effects of nonideal microphone directivity patterns on directional impulse response measurements." Journal of the Acoustical Society of America 126, no. 4 (2009): 2287. http://dx.doi.org/10.1121/1.3249376.

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30

Nishiura, Mayu, Yasuko Omori, Fumihito Morimoto, and Toshiro Mizuta. "An effects of the directivity of the empathy gives to heal sadness." Proceedings of the Annual Convention of the Japanese Psychological Association 79 (September 22, 2015): 1PM—106–1PM—106. http://dx.doi.org/10.4992/pacjpa.79.0_1pm-106.

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31

Ghahari, S. Farid, and A. Reza Khaloo. "Considering rupture directivity effects, which structures should be named ‘long-period buildings’?" Structural Design of Tall and Special Buildings 22, no. 2 (December 13, 2010): 165–78. http://dx.doi.org/10.1002/tal.667.

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32

Pasqual, Alexander Mattioli, José Roberto Arruda, and Philippe Herzog. "Effects of enclosure design on the directivity synthesis by spherical loudspeaker arrays." Journal of the Acoustical Society of America 123, no. 5 (May 2008): 3643. http://dx.doi.org/10.1121/1.2934915.

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33

Chen, Y., J. Letort, F. Cotton, and S. Drouet. "High-frequency directivity effects: evidence from analysis of the Les Saintes records." Journal of Seismology 18, no. 3 (February 13, 2014): 457–66. http://dx.doi.org/10.1007/s10950-014-9419-2.

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34

Abimbola, Raji A. "Effects of Spacing and Number of Elements on the Fields Radiated by Linear Arrays of Equally Spaced Elements." Circulation in Computer Science 2, no. 9 (October 20, 2017): 17–22. http://dx.doi.org/10.22632/ccs-2017-252-55.

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This paper examines the effects of spacings and number of elements on the radiation features of linear antenna of uniformly spaced elements, oriented in end fire directions. Use is made of pattern multiplication concept to evaluate the electric field radiated by the antenna when excited with sinusoidal current distribution. It is found that, when the spacings between the elements of the array are , and , respectively, the radiated field patterns of models of the array depict radiations in broadside and end fire directions while at lower spacings of and , radiations exist only along the end fire directions. In addition, it is also observed that, the beam-width of the main lobe of the field patterns reduces as the spacing and number of element increase which suggests better directivity. However, the improvement in the directivity is followed with side lobe levels which seem to be the disadvantage of that benefit. Furthermore, it is discovered that the array factor patterns and radiated electric field patterns of the antenna display characteristics that are largely similar.

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35

Agudo, Òscar Calderón, Philippe Caprioli, and Dirk-Jan van Manen. "A spatially compact source designature filter." GEOPHYSICS 81, no. 2 (March 1, 2016): V125—V139. http://dx.doi.org/10.1190/geo2015-0259.1.

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Source arrays are usually tuned for optimum primary-to-bubble ratio of the output. In addition, they may also be designed to mitigate source ghost effects, but such configurations introduce directivity effects as the generated downgoing wavefield varies with the source angles. We have investigated a practical source signature deconvolution operator, valid for any marine source array, which is able to remove source ghosts, residual bubble, and directivity effects from seismic data. The designature operator was designed to be a small wavenumber approximation of the inverse of the far-field signature of a source array, which involved the array geometry, the notional source signatures, and the firing synchronization of the sources. We have found that such an approximation leads to the design of spatially compact source designature (CSD) filters able to correct for shot-to-shot perturbations of the sources’ output and reduced their smearing due to the limited spatial aperture of the filters. They also had the potential to account for some source directivity and source ghost effects when applied to common receiver gathers. Our method was then further studied for a particular synchronized multilevel source array and azimuthal variations were neglected. First, tests on synthetic data were performed and the benefits and limitations of the approach were analyzed. Second, the method was tested on a field data set under further approximations that simplified the processing flow (1D earth and average notionals) and which enabled the direct application to common shot gathers. Our results have determined that the expected small — but nevertheless observable — improvements of source designature even at the target level improved event continuity, dephasing, and sharpening of the wavelet. Additionally, the CSD filter was used in conjunction and compared with the current best-practice data processing techniques.

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36

Cheng, Yue, Anbang Zhao, Juan Hui, Tiansi An, and Bin Zhou. "Parametric Underwater Transmission Based on Pattern Time Delay Shift Coding System." Mathematical Problems in Engineering 2018 (December 26, 2018): 1–7. http://dx.doi.org/10.1155/2018/8249245.

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The technique of pattern time delay shift coding (PDS) underwater acoustic (UWA) communication based on parametric array is presented in this paper, which is easy to be implemented and robust in the spatiotemporal variable ocean environment. The parametric array can generate low-frequency, broadband, and high-directivity beam with small-aperture. The high directivity reduces the impact of time variant characteristics of UWA channel especially multipath effects and improves the reuse rate of underwater acoustic channel at the same time. The wide bandwidth allows high rate communications. The sea trial results show that it can be employed to combat multipath propagation in shallow water and achieve very low bit error rate (BER). The theoretical research and sea trial verify the feasibility and effectiveness of the proposed UWA method.

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Tahcfulloh, Syahfrizal. "MIMO Radar Array Antenna with Transmit-Receive Subarrays." International Journal of Intelligent Engineering and Systems 13, no. 6 (December 31, 2020): 189–98. http://dx.doi.org/10.22266/ijies2020.1231.17.

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Unlike the PMIMO radar, the transmit-receive (Tx-Rx) subarrays MIMO (TRSM) radar uses overlaping subarrays in Tx and Rx array so that it simultaneously combines the main advantage of the phased array radar (PA) i.e., high directional coherent gain, and the main advantage of the MIMO radar i.e., high waveform diversity gain. This paper has derived the radar performance formula such that Tx-Rx gain and SINR. The approach aims to overcome the beam shape loss, increase the transmit-receive gain, minimize the maximum peak sidelobe levels, narrow the half power beamwidth, increase directivity, and increase signal-to-noise-plus-interference ratio (SINR). This radar's performance is compared to the PMIMO radar in various methods such as equal subarrays, unequal subarrays, and optimum partitioning, the PA radar, and the MIMO radar. The numerical simulation and evaluation results show that the proposed radar has several advantages such as lowest the peak sidelobe level, narrow the half power beamwidth, and high directivity, so it is very robust against interference effects. When compared to the OPPM radar, as representative of the best-performing radars, this radar has an average performance improvement of MPSLL, directivity, and HPBW which are 21.5 dB, 2 dB, and 0.45 deg, respectively.

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Onuma, Naoki, Satoshi Koura, Takehiko Tanabu, Syuhei Konishi, Yuuji Dohi, Ryo Tagami, and Masayuki Misaki. "Directivity controlled loudspeaker system and enhanced effects on TV listening in older adults." Technology and Disability 12, no. 1 (April 1, 2000): 21–28. http://dx.doi.org/10.3233/tad-2000-12104.

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Lewis, M. Samantha, Carl C. Crandell, and Nicole V. Kreisman. "Effects of Frequency Modulation (FM) Transmitter Microphone Directivity on Speech Perception in Noise." American Journal of Audiology 13, no. 1 (June 2004): 16–22. http://dx.doi.org/10.1044/1059-0889(2004/004).

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Frequency modulation (FM) technology can significantly improve the speech perception ability of individuals with sensorineural hearing loss (SNHL) in background noise. Previous investigations have demonstrated that the microphone design of the FM transmitter can have a significant impact on this improved speech perception. The purpose of this investigation was to compare 3 types of FM transmitter microphone designs: (a) wide angle (omnidirectional microphone), which amplifies sounds coming from all directions around the microphone equally; (b) zoom (1 directional microphone), which provides less amplification to signals coming from the rear, and (c) superzoom (2 directional microphones), which provides less amplification to signals originating from the rear and the sides. Fifteen adults with bilateral slight to moderately severe SNHL participated. Speech perception was assessed using the Hearing in Noise Test (M. Nilsson, S. Soli, & J. Sullivan, 1994). Speech spectrum shaped noise served as the noise competition. Results revealed that the best speech perception in noise was obtained when the FM transmitter was used in the zoom setting. The poorest performance was obtained when the FM transmitter was in the wide-angle mode. The clinical implications of these results are discussed.

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Gazi, Hatice, and Cenk Alhan. "Reliability of elastomeric-isolated buildings under historical earthquakes with/without forward-directivity effects." Engineering Structures 195 (September 2019): 490–507. http://dx.doi.org/10.1016/j.engstruct.2019.05.081.

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Yang, Jinping, Peizhen Li, Hang Jing, and Meng Gao. "Near-Fault Ground Motion Influence on the Seismic Responses of a Structure with Viscous Dampers considering SSI Effect." Advances in Civil Engineering 2021 (February 6, 2021): 1–20. http://dx.doi.org/10.1155/2021/6649124.

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This paper studies the influence of the characteristics of the near-fault ground motion on the seismic responses of the structure with energy dissipation devices including soil-structure interaction (SSI). A ten-story reinforced concrete frame rested on soft site is introduced, and the viscous dampers added in the frame are designed. The numerical analysis method of the soil-structure system with viscous dampers is established through ANSYS program. In addition, the response spectra of the main characteristics of the near-fault ground motion, like hanging wall effect, velocity pulse-like effect, and forward-directivity effect, are investigated carefully to learn the features of spectra energy distribution. And then, the dynamic time-history analysis is performed on the SSI system with and without viscous dampers subjected to the selected near-fault ground motion. The study reveals that the seismic responses of the structure subjected to near-fault ground motion with hanging wall effect are obviously larger than those of the footwall effect, indicating the distinct hanging wall effects on the structural dynamic responses. In addition, the performance of the structure with viscous dampers is more influenced by the ground motion containing fling-step effect than that with forward-directivity effect. Moreover, the influence of the horizontal component of forward-directivity ground motion on the seismic responses of the structure is more obvious than that of parallel component ground motion. Consequently, the hanging wall effect, velocity pulse, and horizontal component in forward-directivity effect of the near-fault ground motion have distinct influence on the seismic responses of the structure with energy dissipation devices considering SSI effect, providing insight towards the performance-based seismic design of buildings rested at the near-fault sites considering the seismic SSI effect.

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Sgobba, Sara, Giovanni Lanzano, Francesca Pacor, and Chiara Felicetta. "An Empirical Model to Account for Spectral Amplification of Pulse-Like Ground Motion Records." Geosciences 11, no. 1 (December 29, 2020): 15. http://dx.doi.org/10.3390/geosciences11010015.

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Near-source effects can amplify seismic ground motion, causing large demand to structures and thus their identification and characterization is fundamental for engineering applications. Among the most relevant features, forward-directivity effects may generate near-fault records characterized by a large velocity pulse and unusual response spectral shape amplified in a narrow frequency-band. In this paper, we explore the main statistical features of acceleration and displacement response spectra of a suite of 230 pulse-like signals (impulsive waveforms) contained in the NESS1 (NEar Source Strong-motion) flat-file. These collected pulse-like signals are analyzed in terms of pulse period and pulse azimuthal orientation. We highlight the most relevant differences of the pulse-like spectra compared to the ordinary (i.e., no-pulse) ones, and quantify the contribution of the pulse through a corrective factor of the spectral ordinates. Results show that the proposed empirical factors are able to capture the amplification effect induced by near-fault directivity, and thus they could be usefully included in the framework of probabilistic seismic hazard analysis to adjust ground-motion model (GMM) predictions.

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Rowshandel, Badie. "Ground Motion Hazard and Scenario Design Earthquakes Including Source Rupture Effects, Case in Study: City of San Francisco." Earthquake Spectra 25, no. 2 (May 2009): 379–414. http://dx.doi.org/10.1193/1.3111172.

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Using a probabilistic approach, a directivity model, and the fault and seismicity database of the California Geological Survey, one-second spectral accelerations for a site in the city of San Francisco are computed for several fault rupture types. Five rupture scenarios were investigated. Of these, two cases involve random distribution of hypocenters and two are “limiting cases,” resulting in the lower-bound and the upper-bound ground motions at the site. Deaggregation of hazard in terms of magnitude, distance, epsilon, and directivity for the rupture scenarios studied reveals that three scenario events dominate ground motion hazard at the site. Expressed in terms of modal values of the hazard parameters, these are: (1) [Formula: see text], [Formula: see text], (2) [Formula: see text], [Formula: see text], and (3) [Formula: see text], [Formula: see text]. The relative significance of these scenario events varies mostly with rupture type and to lesser degrees with site condition and return period. The first scenario event is a repeat of the 1906 San Francisco earthquake. The second represents the impact of the San Gregorio fault and North-Coast and Offshore segments of the San Andreas fault, and the third reflects the seismicity mainly on the Peninsula and the Santa Cruz Mountains segments of the San Andreas fault.

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SI, Hongiun, and Saburoh MIDORIKAWA. "EVALUATION OF RUPTURE DIRECTIVITY EFFECTS ON PEAK GROUND MOTION USING STOCHASTIC GREEN'S FUNCTION METHOD." Journal of Structural and Construction Engineering (Transactions of AIJ) 66, no. 546 (2001): 47–53. http://dx.doi.org/10.3130/aijs.66.47_3.

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Krylov, Victor V. "Directivity patterns of laser-generated sound in solids: Effects of optical and thermal parameters." Ultrasonics 69 (July 2016): 279–84. http://dx.doi.org/10.1016/j.ultras.2016.01.011.

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Kompis, Martin, and Norbert Dillier. "Simulating transfer functions in a reverberant room including source directivity and head‐shadow effects." Journal of the Acoustical Society of America 93, no. 5 (May 1993): 2779–87. http://dx.doi.org/10.1121/1.405825.

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Bazarchi, Ehsan, Reza Saberi, and Majid Alinejad. "Seismic hazard assessment of Tehran, Iran with emphasis on near-fault rupture directivity effects." Earthquake Science 31, no. 1 (2018): 1–11. http://dx.doi.org/10.29382/eqs-2018-0001-1.

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Manabe, T., Y. Miura, and T. Ihara. "Effects of antenna directivity and polarization on indoor multipath propagation characteristics at 60 GHz." IEEE Journal on Selected Areas in Communications 14, no. 3 (April 1996): 441–48. http://dx.doi.org/10.1109/49.490229.

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Chang, Zhiwang, Xiaodan Sun, Changhai Zhai, John X. Zhao, and Lili Xie. "An empirical approach of accounting for the amplification effects induced by near-fault directivity." Bulletin of Earthquake Engineering 16, no. 5 (November 27, 2017): 1871–85. http://dx.doi.org/10.1007/s10518-017-0275-7.

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Bezzeghoud, M., J. F. Borges, and B. Caldeira. "Ground motion simulations of the SW Iberia margin: rupture directivity and earth structure effects." Natural Hazards 69, no. 2 (August 17, 2011): 1229–45. http://dx.doi.org/10.1007/s11069-011-9925-2.

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