Articles de revues : « Spiral array »

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de Souza, Júlio Cesar Eduardo, Montserrat Parrilla Romero, Ricardo Tokio Higuti et Óscar Martínez-Graullera. « Design of Ultrasonic Synthetic Aperture Imaging Systems Based on a Non-Grid 2D Sparse Array ». Sensors 21, n^o 23 (30 novembre 2021) : 8001. http://dx.doi.org/10.3390/s21238001.

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This work provides a guide to design ultrasonic synthetic aperture systems for non-grid two-dimensional sparse arrays such as spirals or annular segmented arrays. It presents an algorithm that identifies which elements have a more significant impact on the beampattern characteristics and uses this information to reduce the number of signals, the number of emitters and the number of parallel receiver channels involved in the beamforming process. Consequently, we can optimise the 3D synthetic aperture ultrasonic imaging system for a specific sparse array, reducing the computational cost, the hardware requirements and the system complexity. Simulations using a Fermat spiral array and experimental data based on an annular segmented array with 64 elements are used to assess this algorithm.

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Engebretson, Mark E., et Luis F. Esparza. « Spiral line array loudspeaker ». Journal of the Acoustical Society of America 127, n^o 5 (2010) : 3286. http://dx.doi.org/10.1121/1.3432269.

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Yoon, Hansol, et Tai-Kyong Song. « Sparse Rectangular and Spiral Array Designs for 3D Medical Ultrasound Imaging ». Sensors 20, n^o 1 (27 décembre 2019) : 173. http://dx.doi.org/10.3390/s20010173.

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In three-dimensional (3D) medical ultrasound imaging with two-dimensional (2D) arrays, sparse 2D arrays have been studied to reduce the number of active channels. Among them, sparse 2D arrays with regular or uniform arrangements of elements have advantages of low side lobe energy and uniform field responses over the entire field of view. This paper presents two uniform sparse array models: sparse rectangular arrays (SRAs) on a rectangular grid and sparse spiral arrays (SSAs) on a sunflower grid. Both arrays can be easily implemented on the commercially available or the custom-made arrays. To suppress the overall grating lobe levels, the transmit (Tx) and receive (Rx) array pairs of both the array models are designed not to have grating lobes at the same locations in the Tx/Rx beam patterns, for which the theoretical design rules are also proposed. Computer simulation results indicate that the proposed array pairs for both the SRAs and the SSAs achieve peak grating lobe levels below –40 dB using about a quarter of the number of elements in the dense rectangular array while maintaining similar beam widths to that of the dense array pair.

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Hebib, S., N. Raveu et H. Aubert. « Cantor Spiral Array for the Design of Thinned Arrays ». IEEE Antennas and Wireless Propagation Letters 5 (2006) : 104–6. http://dx.doi.org/10.1109/lawp.2006.872415.

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Yunlin Liu, Yong Wang et Rugui Yang. « A cylindrical spiral patch array ». IEEE Transactions on Antennas and Propagation 49, n^o 2 (2001) : 196–99. http://dx.doi.org/10.1109/8.914275.

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RECIOUI, Abdelmadjid. « Concentric Ring Arrays Optimization Using the Spiral Inspired Technique ». Algerian Journal of Signals and Systems 3, n^o 1 (15 mars 2018) : 10–21. http://dx.doi.org/10.51485/ajss.v3i1.55.

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In this work, concentric ring Arrays (CRA) with non-uniform excitation are investigated, with the objective being to minimize the Sidelobe Level (SLL) for the array and keep the Directivity within an acceptable value. The optimization technique to be used to reach this objective is the spiral inspired optimization technique.. First, the technique is used to minimize the SLL only. Next the array factor is optimized for Directivity only. Then, the excitation is varied for both SLL and Directivity to be optimized. The results show significant improvements with respect to the uniform case, especially for SLL reduction, with different levels of success depending on the employed optimization technique, fitness function, varied parameters, and array size.

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Radó, János, Péter Udvardi, Saeedeh Soleimani, Lucky Kenda Peter, István Bársony, Péter Révész et János Volk. « Low-Frequency Piezoelectric Accelerometer Array for Fully Implantable Cochlear Implants ». Proceedings 2, n^o 13 (26 novembre 2018) : 1059. http://dx.doi.org/10.3390/proceedings2131059.

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We demonstrate a low-volume, stress-free, piezoelectric micro-electromechanical system (MEMS) cantilever array for fully implantable hearing aids. The 12-element spiral-matrix is sensitive to the lower part of audible frequency range (300–700 Hz) through the proper resonant frequency of the individual spirals tuned by dimensions of the cantilevers. The obtained high Q-factors (117–254) provide high frequency selectivity. The generated open circuit voltage signals could be sufficient for the direct analog conversion of the signals for cochlear multielectrode implants. By comparing different geometries we have also demonstrated that the initial stress, which is derived from silicon-dioxide (SiO2) and aluminum-nitride (AlN) layers, could be drastically reduced simply by the spiral geometry. The results of vibration measurements have shown a good agreement with the calculated resonant frequencies.

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Fukuoka, Junya, Matthias D. Hofer, Takashi Hori, Tomonori Tanaka, Shin Ishizawa, Kazuhiro Nomoto, Manami Saito, Takeshi Uemura et Lucian R. Chirieac. « Spiral Array : A New High-Throughput Technology Covers Tissue Heterogeneity ». Archives of Pathology & ; Laboratory Medicine 136, n^o 11 (1 novembre 2012) : 1377–84. http://dx.doi.org/10.5858/arpa.2011-0393-oa.

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Context.—Tissue array is a well-established technique that connects basic research with clinical applications and allows for the validation of many pathobiologic events from gene expression dysregulation to genomic aberrations. However, conventional tissue array has several limitations such as poor representation of tissue heterogeneity, destruction of donor tissue blocks due to coring, and usage of particular specimens that have limited evaluable material (tissue from thin specimens or needle biopsies). Objective.—To show the noninferiority and superiority of the new technique named Spiral Array—which allows for improved representation of the donor tissue while keeping the architectural details of the donor block intact—to that of the conventional tissue array. We compared the morphologic features of both methods. Design.—We created both Spiral Array and conventional tissue array for 25 lung adenocarcinomas and 50 multiple tumors of various organs. The degree of coverage of tissue heterogeneity was examined by observing the range of the staining intensity differences in immunohistochemistry, using cytokeratin 7 and epidermal growth factor receptor (EGFR); the degree of morphologic preservation was tested by level of accurate prediction among 3 pathologists of the histopathologic diagnosis and organ type. Results.—The Spiral Array showed better representations of the range of staining intensity for EGFR (P = .01). The level of accuracy for predicting organ type was significantly higher in Spiral Array than conventional tissue array (P = .047), whereas it was not significantly different between the 2 techniques for the histologic diagnosis. Conclusion.—Our data indicate that Spiral Array has benefits for covering tissue heterogeneity and preserving better morphology.

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Martínez, O., C. J. Martín, G. Godoy et L. G. Ullate. « 2D array based on fermat spiral ». Physics Procedia 3, n^o 1 (janvier 2010) : 399–406. http://dx.doi.org/10.1016/j.phpro.2010.01.052.

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Liu, Z. Q., et Mian Hao Zhang. « Based on Pro/E Construction Method of Spiral Bevel Gear Logarithm ». Advanced Materials Research 215 (mars 2011) : 167–71. http://dx.doi.org/10.4028/www.scientific.net/amr.215.167.

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For a new type of bevel gear named as logarithmic spiral bevel gear, establish its tooth direction curves and the mathematical model of tooth surface equation. With CAD software platform which can intuitive understanding of complex curves and combined with conical logarithmic spiral parameter equation build the logarithmic spiral on cone surface. Then array logarithmic spiral to make them evenly distributed in the cone surface, without any interference and to meet the strength distribution on both ends of circular truncated cone equally. Use two logarithmic spirals from different starpoint as tooth direction curves of lift and right tooth surface. Finally, use space geometric knowledge to build tooth surface equation by tooth direction curves and tooth profile curves.

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Li, Qiang, Zi Liang Wei, Hong Bo Yan et Hai Yan Hu. « A New Method of Constructing Tooth Surface for Logarithmic Spiral Bevel Gear ». Advanced Materials Research 129-131 (août 2010) : 235–40. http://dx.doi.org/10.4028/www.scientific.net/amr.129-131.235.

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For a new type of bevel gear—logarithmic spiral bevel gear, establish its tooth direction curves and the mathematical model of tooth surface equation. With CAD software platform which can intuitive understanding of complex curves and combined with conical logarithmic spiral parameter equation build the logarithmic spiral on cone surface. Then array logarithmic spiral to make them evenly distributed in the cone surface, without any interference and to meet the strength distribution on both ends of circular truncated cone equally. Use two logarithmic spirals from different starpoint as tooth direction curves of lift and right tooth surface. Finally, use space geometric knowledge to build tooth surface equation by tooth direction curves and tooth profile curves.

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Lu, Guo, Lan, Sun, Li et Zhou. « Underwater Spiral Wave Sound Source Based on Phased Array with Three Transducers ». Sensors 19, n^o 14 (19 juillet 2019) : 3192. http://dx.doi.org/10.3390/s19143192.

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This paper realizes an underwater spiral wave sound source by using three omni-directional spherical transducers with three different phases. The pressure distribution of the sound field for a phased array is derived using the superposition theory of sound field. The generation of spiral wave field is presented, the relationship between the performance of phased array sound field and the array parameters is analyzed, and also verified by the finite element method (FEM). A spiral wave sound source with three spherical piezoelectric ceramic transducers is then designed and fabricated based on FEM simulation, and the performance of the sound source is analyzed. Measurements are made in a reverberation pool, and the result shows that the fabricated spiral wave sound source is capable of producing a spiral sound wave. Under a frequency of 3.5 kHz, the phase directivity has a fluctuation of ±21°, and the amplitude directivity range is 4.3 dB, which verifies the realization of the spiral wave sound source.

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Chen, Lin Song, Yue Yun Cao et Wen Yong Guo. « A Rotary Spiral Array Applied in Near-Field Acoustical Holography ». Applied Mechanics and Materials 551 (mai 2014) : 202–9. http://dx.doi.org/10.4028/www.scientific.net/amm.551.202.

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This paper presents a new method to apply a spiral array in near-field acoustical holography (NAH). Usually, a NAH array needs much more microphones than a beamforming array does. Superior to a normal regular planar grid array or linear scanning array, this spiral array rotates to get more measuring data. Without a static referring microphone, a numerical method was designed to estimate the phase information measured at different time. Numerical simulations and a series experiment showed that this method is adequate for the sound below 450Hz. It is especially useful for using a random planar array at NAH mode, while the beamforming mode can only cover the higher frequency band.

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Wang, Hairui, Yao Zhang, Siyu Chen, Yinji Ma, Heling Wang, Ying Chen et Xue Feng. « Mechanics Design of Conical Spiral Structure for Flexible Coilable Antenna Array ». International Journal of Aerospace Engineering 2022 (24 mai 2022) : 1–8. http://dx.doi.org/10.1155/2022/4265384.

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Limited by the effective launch capacity of a rocket, the deployable antenna is very important in the design of spaceborne antenna array. Compared to traditional deployable antenna, flexible coilable antenna array has higher surface precision and better vibration control and therefore is more suitable for high frequency communication. In order to minimize the weight of satellite and reduce cost of its launch, a design guideline to the geometry parameters of flexible coilable antenna array is crucial. Existing models cannot be directly applied to interaction and large deformation between coilable membrane and conical spiral antenna in the flexible coilable antenna array. Hence, the geometry parameters of the conical spiral structure and the thickness of the coilable membrane in the flexible coilable antenna array have not been optimized yet. In this paper, the interaction between the coilable membrane and the concial spiral antenna is analyzed in the antenna array. A concise formula is derived to predict the critical force that flattens the conical spiral antenna by a coiling scroll. Combined with a theoretical model to predict the deformation of the membrane, the model provides an important theoretical support for the lightweight design and mechanical design of flexible coilable antenna array, such as the thickness of the coilable membrane. The proposed design is validated by experiments. The above findings have potential applications in the effective reduction of antenna array weight and satellite launch costs.

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Li, Xiaotong, Anthony Gachagan et Paul Murray. « Design of 2D Sparse Array Transducers for Anomaly Detection in Medical Phantoms ». Sensors 20, n^o 18 (19 septembre 2020) : 5370. http://dx.doi.org/10.3390/s20185370.

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Aperiodic sparse 2D ultrasonic array configurations, including random array, log spiral array, and sunflower array, have been considered for their potential as conformable transducers able to image within a focal range of 30–80 mm, at an operating frequency of 2 MHz. Optimisation of the imaging performance of potential array patterns has been undertaken based on their simulated far field directivity functions. Two evaluation criteria, peak sidelobe level (PSL) and integrated sidelobe ratio (ISLR), are used to access the performance of each array configuration. Subsequently, a log spiral array pattern with −19.33 dB PSL and 2.71 dB ISLR has been selected as the overall optimal design. Two prototype transducers with the selected log spiral array pattern have been fabricated and characterised, one using a fibre composite element composite array transducer (CECAT) structure, the other using a conventional 1–3 composite (C1–3) structure. The CECAT device demonstrates improved coupling coefficient (0.64 to 0.59), reduced mechanical cross-talk between neighbouring array elements (by 10 dB) and improved operational bandwidth (by 16.5%), while the C1–3 device performs better in terms of sensitivity (~50%). Image processing algorithms, such as Hough transform and morphological opening, have been implemented to automatically detect and dimension particles located within a fluid-filled tube structure, in a variety of experimental scenarios, including bespoke phantoms using tissue mimicking material. Experiments using the fabricated CECAT log spiral 2D array transducer demonstrated that this algorithmic approach was able to detect the walls of the tube structure and stationary anomalies within the tube with a precision of ~0.1 mm.

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KLEVECZ, ROBERT R., JAMES BOLEN et OSCAR DURÁN. « SELF-ORGANIZATION IN BIOLOGICAL TISSUES : ANALYSIS OF ASYNCHRONOUS AND SYNCHRONOUS PERIODICITY, TURBULENCE AND SYNCHRONOUS CHAOS EMERGENT IN COUPLED CHAOTIC ARRAYS ». International Journal of Bifurcation and Chaos 02, n^o 04 (décembre 1992) : 941–53. http://dx.doi.org/10.1142/s0218127492000549.

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Large discrete arrays of chaotic attractors, coupled by diffusion, organize into asynchronous periodic spiral waves, synchronous periodic bands, turbulent fields or synchronous chaos as a function of coupling strength and array size. Self-organization of periodic spirals in both two and three dimensional arrays of nonexcitable systems appears to require the early establishment of an antipodal phase relationship between the few cells that will form the vortex. Cells within or close to the vortex maintain low z amplitude, near limit cycle trajectories, with stable, well-defined phase relationships. In periodic banding structures, initial antipodal phase seeds evolve to isochrons that form nested periodic trajectories. The likelihood that biological systems are fundamentally oscillatory and chaotic is discussed.

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Encino, Kleiverg, Marco A. Panduro, Alberto Reyna et David H. Covarrubias. « Novel Design Techniques for the Fermat Spiral in Antenna Arrays, for Maximum SLL Reduction ». Micromachines 13, n^o 11 (17 novembre 2022) : 2000. http://dx.doi.org/10.3390/mi13112000.

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This paper presents novel design techniques for the Fermat spiral, considering a maximum side lobe level (SLL) reduction. The array system based on a Fermat spiral configuration considers techniques based on uniform and non-uniform amplitude excitation. The cases of uniform amplitude excitation are the golden angle and the optimization of the angular separations. The cases of non-uniform amplitude excitations consider a raised cosine distribution and the optimization of the amplitude excitations through the Fermat spiral array. In this study, the method of genetic algorithms (GA) was used in the cases to find the values of the angular separations and the amplitude excitations of the Fermat spiral array. A performance evaluation was conducted for all these design cases, considering the Fermat spiral geometry. These design cases were validated using electromagnetic simulation to take mutual coupling into account and consider the effect of the antenna element pattern in each proposed design case.

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Vallecchi, A., R. J. Langley et A. G. Schuchinsky. « Voltage Controlled Intertwined Spiral Arrays for Reconfigurable Metasurfaces ». International Journal of Antennas and Propagation 2014 (2014) : 1–10. http://dx.doi.org/10.1155/2014/171637.

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Reconfigurable bistate metasurfaces composed of interwoven spiral arrays with embeddedpindiodes are proposed for single and dual polarisation operation. The switching capability is enabled bypindiodes that change the array response between transmission and reflection modes at the specified frequencies. The spiral conductors forming the metasurface also supply the dc bias for controllingpindiodes, thus avoiding the need of additional bias circuitry that can cause parasitic interference and affect the metasurface response. The simulation results show that proposed active metasurfaces exhibit good isolation between transmission and reflection states, while retaining excellent angular and polarisation stability with the large fractional bandwidth (FBW) inherent to the original passive arrays.

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Rossi, Stefano, Alessandro Ramalli, Fabian Fool et Piero Tortoli. « High-Frame-Rate 3-D Vector Flow Imaging in the Frequency Domain ». Applied Sciences 10, n^o 15 (3 août 2020) : 5365. http://dx.doi.org/10.3390/app10155365.

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Ultrasound vector Doppler techniques for three-dimensional (3-D) blood velocity measurements are currently limited by low temporal resolution and high computational cost. In this paper, an efficient 3-D high-frame-rate vector Doppler method, which estimates the displacements in the frequency domain, is proposed. The novel method extends to 3-D an approach so far proposed for two-dimensional (2-D) velocity measurements by approximating the (x, y, z) displacement of a small volume through the displacements estimated for the 2-D regions parallel to the y and x directions, respectively. The new method was tested by simulation and experiments for a 3.7 MHz, 256-element, 2-D piezoelectric sparse spiral array. Simulations were also performed for an equivalent 7 MHz Capacitive Micromachined Ultrasonic Transducer spiral array. The results indicate performance (bias ± standard deviation: 6.5 ± 8.0) comparable to the performance obtained by using a linear array for 2-D velocity measurements. These results are particularly encouraging when considering that sparse arrays were used, which involve a lower signal-to-noise ratio and worse beam characteristics with respect to full 2-D arrays.

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Xu, Jie, Hui Li, You-Ling zhou, Qian Li, Liu-Xun Xue, Chong-Yue Shi et Hou Wang. « Performance analysis of vortex acoustic wave based on uniform circular array ». Journal of Physics : Conference Series 2078, n^o 1 (1 novembre 2021) : 012069. http://dx.doi.org/10.1088/1742-6596/2078/1/012069.

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Abstract As a carrier for information and energy, acoustic waves have been applied in underwater communication widely, however, the narrow band and low transmission speed are the main problems. Whether in the field of optics or electromagnetic waves, the orbital angular momentum (OAM) represents the natural properties of the spiral phase structure. By introducing the OAM into the acoustics field, the transmission capacity and spectrum efficiency of the underwater acoustic communication system can be expanded. Based on the analysis and detection of the vortex acoustic wave generated by the circular array of transducers, we studied the array generation method of the spiral acoustic beam, and gave the characteristics of the vortex acoustic beam when propagating under the water. In the direction of the main axis, the uniform circular array was used to generate different topological acoustic vortex. To determine the relationship between the OAM topology mode and the transducer array, the spiral acoustic waves in different topology modes were generated, and the number of array elements, array radius, transmission frequency, etc. were investigated to give the effects on OAM acoustic vortex.

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Speedie, Jessica, Richard A. Booth et Ruobing Dong. « Observing Planet-driven Dust Spirals with ALMA ». Astrophysical Journal 930, n^o 1 (1 mai 2022) : 40. http://dx.doi.org/10.3847/1538-4357/ac5cc0.

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Abstract Atacama Large Millimeter/submillimeter Array (ALMA) continuum observations of thermal emission from the dust component of protoplanetary disks have revealed an abundance of substructures that may be interpreted as evidence for embedded planets, but planet-driven spiral arms—perhaps one of the most compelling lines of evidence—have proven comparatively elusive. In this work, we test the capabilities of ALMA to detect the planet-driven spiral signal in continuum emission. Carrying out hydrodynamic simulations and radiative transfer calculations, we present synthetic Band 7 continuum images for a wide range of disk and observing conditions. We show that thermal mass planets at tens of astronomical units typically drive spirals detectable within a few hours of integration time, and the detectable planet mass may be as low as ∼Neptune mass (0.3 M th). The grains probed by ALMA form spirals morphologically identical to the underlying gas spiral. The temperature of the dust spiral is crucial in determining its contrast, and spirals are easier to detect in disks with an adiabatic equation of state and longer cooling times. Resolving the spiral is not necessary for its detection; with the help of residual maps, the optimal beam size is a few times the spiral width at a constant noise level. Finally, we show how the presence of gaps and rings can impair our ability to recognize colocated spirals. Our work demonstrates the planet-finding potential of the current design specification of ALMA, and suggests that observing capability is not the bottleneck in searching for spirals induced by thermal mass planets.

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Jafargholi, A., M. Kamyab et M. Veysi. « Spiral array architecture, design, synthesis and application ». IET Microwaves, Antennas & ; Propagation 5, n^o 5 (2011) : 503. http://dx.doi.org/10.1049/iet-map.2010.0301.

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Liu, Yu. « Adaptive Array Reduction in Acoustic Beamforming (Virtual Presentation) ». INTER-NOISE and NOISE-CON Congress and Conference Proceedings 265, n^o 1 (1 février 2023) : 6745–56. http://dx.doi.org/10.3397/in_2022_1021.

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Acoustic beamforming is a widely used source localisation technique where an array of microphones is placed in the acoustic far-field to gather unique contributions of acoustic pressure waves. The spatial and temporal relationship of these pressure contributions are sensitive to the microphone array design. To date, most acoustic beamformers are constructed using a spiral-based array configuration, yet in recent years, a new technique for developing array patterns has emerged that unlocks flexibility and convenient customisation, yielding improved acoustic source imaging to its predecessors. These arrays are developed using an iterative microphone removal process, known as an array reduction method. A cost-function is developed that combines the penalty of spatial aliasing images, known as sidelobes, and the resolution of the acoustic source, known as the main lobe. Microphones are iteratively removed from a larger initial array to arrive at an array with a desired number of microphones, frequency range and spatial constraints. The use of array reduction method arrays has expanded into array designs for o set source locations, irregular areas, and the most recent advancement, array pairing. This paper provides a brief summary of the development of the array reduction techniques and some example results of its application.

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Xu, Wencong, Bingshu Chen, Yandong Li, Yue Hu, Jianxun Li et Zijing Zeng. « Dir-MUSIC Algorithm for DOA Estimation of Partial Discharge Based on Signal Strength Represented by Antenna Gain Array Manifold ». Sensors 22, n^o 14 (20 juillet 2022) : 5406. http://dx.doi.org/10.3390/s22145406.

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Inspection robots are widely used in the field of smart grid monitoring in substations, and partial discharge (PD) is an important sign of the insulation state of equipment. PD direction of arrival (DOA) algorithms using conventional beam forming and time difference of arrival (TDOA) require large-scale antenna arrays and high computational complexity, making them difficult to implement on inspection robots. To address this problem, a novel directional multiple signal classification (Dir-MUSIC) algorithm for PD direction finding based on signal strength is proposed, and a miniaturized directional spiral antenna circular array is designed in this paper. First, the Dir-MUSIC algorithm is derived based on the array manifold characteristics. This method uses strength intensity information rather than the TDOA information, which could reduce the computational difficulty and the requirement of array size. Second, the effects of signal-to-noise ratio (SNR) and array manifold error on the performance of the algorithm are discussed through simulations in detail. Then, according to the positioning requirements, the antenna array and its arrangement are developed and optimized. Simulation results suggested that the algorithm has reliable direction-finding performance in the form of six elements. Finally, the effectiveness of the algorithm is tested by using the designed spiral circular array in real scenarios. The experimental results show that the PD direction-finding error is 3.39°, which meets the need for partial discharge DOA estimation using inspection robots in substations.

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Hyland, Lucas J., Simon P. Ellingsen et Mark J. Reid. « Structure of the Milky Way : View from the Southern Hemisphere ». Proceedings of the International Astronomical Union 13, S336 (septembre 2017) : 154–57. http://dx.doi.org/10.1017/s1743921318000832.

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AbstractThe exclusive association of Class II methanol masers with high mass star formation regions and in turn spiral arms, makes them ideal tracers of spiral structure. The bright and compact nature of masers also makes them good sources for Very Long Baseline Interferometry, with their fluxes visible on some of the longest terrestrial baselines. The success of the BeSSeL (Bar and Spiral Structure Legacy) project has demonstrated the use of masers in large scale high–precision trigonometric parallax surveys. This survey was then able to precisely map the spiral arms visible from the Northern Hemisphere and recalculate the fundamental Milky Way parameters R0 and θ0. The majority of the Milky Way is visible from the Southern Hemisphere and at the present time the Australian LBA (Long Baseline Array) is the only Southern Hemisphere array capable of taking high–precision trigonometric parallax data. We present the progress–to–date of the Southern Hemisphere experiment. We will also unveil a new broadband Southern Hemisphere array, capable of much faster parallax turnaround and atmospheric calibration.

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Chao Kang, Chia, et Chia Yang Kang. « Circularly polarize antenna array for electromagnetic energy harvesting ». International Journal of Engineering & ; Technology 7, n^o 2.29 (22 mai 2018) : 1. http://dx.doi.org/10.14419/ijet.v7i2.29.13114.

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Electromagnetic energy harvesting from ambient sources have been presented more than 50 years. In this paper, electromagnetic energy harvesting by using circular polarize antenna array is presented. The proposed antenna is having 2 similar size of spiral inductor that feed by microstrip feed line. The gain, momentum visualization were investigated. The circular polarize antenna are fabricated on Roger 4003 substrates. Based on the observations, it is expected that the gain obtained by the antenna array is higher than the single element antenna. The simulation results show that 3.22 dBi gain can be achieved for single spiral antenna whereas the antenna array can achieved as high as 5.14dBi at frequency 527MHz. The work concluded that investigations of electromagnetic energy harvesting antenna array is successful.

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Ma, Li, Zijun Zhan, Chao Chen, Chunxiang Liu et Chuanfu Cheng. « Generation of ultrashort vortex pulses by spiral array ». Optics & ; Laser Technology 155 (novembre 2022) : 108354. http://dx.doi.org/10.1016/j.optlastec.2022.108354.

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Jafargholi, Amir, et Manouchehr Kamyab. « PATTERN OPTIMIZATION IN AN UWB SPIRAL ARRAY ANTENNA ». Progress In Electromagnetics Research M 11 (2010) : 137–51. http://dx.doi.org/10.2528/pierm10010302.

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Chew, Elaine, et Yun-Ching Chen. « Real-Time Pitch Spelling Using the Spiral Array ». Computer Music Journal 29, n^o 2 (juin 2005) : 61–76. http://dx.doi.org/10.1162/0148926054094378.

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Saito, Atsushi, Yuhei Ogawa, Daiki Oka, Shigetoshi Ohshima et Kensuke Nakajima. « Investigation of Microwave Crosstalk in Spiral-MKIDs Array ». IEEE Transactions on Applied Superconductivity 27, n^o 4 (juin 2017) : 1–4. http://dx.doi.org/10.1109/tasc.2016.2631940.

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Yao, Yuan, Qiuyue Ge, Junsheng Yu et Xiaodong Chen. « A Novel Antenna for UHF RFID Near-Field Applications ». Electronics 10, n^o 11 (30 mai 2021) : 1310. http://dx.doi.org/10.3390/electronics10111310.

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This paper proposed a novel antenna for ultra-high frequency (UHF) radio frequency identification (RFID) near-field applications with uniform distribution of the electric field along the x-axis (Ex), and the y-axis (Ey). The proposed antenna adopted a spiral structure to achieve broadband and multi-polarization. The novel antenna achieved good impedance matching within 860–960 MHz. Using a ground plate, the proposed antenna achieved low far-field gain and a maximum gain of less than −11 dBi. The component of the excited electric field Ex and Ey parallel to the antenna surface was uniformly distributed, and there was no zero point. The proposed antenna achieved a 100% read rate of tags parallel to its surface in the reading area of 150 mm × 150 mm × 220 mm. Simulation results were consistent with the results of real-world measurements, and the proposed antenna was suitable as a reader antenna in near-field applications. The polarization mode of RFID tags is mostly linear polarization, and the placement of tags in practical applications is diversified. Compared with the traditional RFID reader antenna, the proposed antenna achieves uniform electric field distribution parallel to the antenna surface, but the single-direction electric field has zero-reading points, which is easy to cause the misread of tags. The RFID tags can be read more accurately. To verify the scalability of the reading area of the spiral antenna unit, it was used for array design, and simulations were conducted using 1 × 2, 2 × 2, 1 × 4, and 2 × 4 arrays. The component distribution of the electric field excited by the four array antennas in the x and y directions was uniform and the reading area was controllable. Therefore, the proposed spiral antenna has the expandability of the reading area and can meet the needs of different application scenarios by changing the number of array units. With the array extension, the matching network also extends, and the impedance characteristics of the array antenna are somewhat different, but they also meet the application requirements.

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Luo, Win-Jet, C. Bambang Dwi Kuncoro, Pratikto et Yean-Der Kuan. « Single-Layer Transmitter Array Coil Pattern Evaluation toward a Uniform Vertical Magnetic Field Distribution ». Energies 12, n^o 21 (31 octobre 2019) : 4157. http://dx.doi.org/10.3390/en12214157.

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A uniform magnetic field distribution is a critical aspect in the transmitter array coil design process for achieving a homogenous vertical magnetic field distribution. The free position and orientation features can thus be implemented in the wireless power charging system. This paper presents vertical magnetic field distribution generated by a single-layer circular flat spiral air core transmitter array coil model analysis and evaluation using a numerical analysis method. This method is developed based on the off-symmetry axis magnetic field distribution due to a circular current loop derived from the Biot-Savart law. The proposed evaluation criteria are used to obtain the vertical magnetic field distribution characteristic of the evaluated array coil model. The vertical magnetic field distribution of several circular flat spiral air core coils, in both single and array coil models with different coil geometries were investigated to obtain the relation between the coil parameters and the distance between the adjoining coil centers to generate uniform vertical magnetic field distribution. A case study was also conducted to analyze and evaluate several array coil model patterns (1 × 2 array coil, 1 × 3 array coil, 2 × 2 array coil, 2 × 3 array coil) to meet uniform vertical magnetic field distribution. The array coil model is composed of an identical single circular flat spiral air-core coil. Every single coil has inner coil diameter (Di), outer coil diameter (Do), wire diameter (W), pitch (P) and a number of turns (N) at 25 mm, 47.8 mm, 0.643 mm, 0.03 mm, 17 respectively. The study and evaluation of several array coil pattern models show that the distance between the adjoining coil centers should be defined close to the half of coil outer diameter (1/2Do) to generate close to uniform vertical magnetic field distribution. The vertical magnetic field distribution average and magnetic field effective transmitting areas array coil model with the given coil parameters changing as the effect in variation in distances between the adjoining coil centers.

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Fraundorf, P., et Shuhan Lin. « Spiral Powder Overlays ». Microscopy Today 13, n^o 1 (janvier 2005) : 8–11. http://dx.doi.org/10.1017/s1551929500050781.

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Whether you encounter electron powder diffraction patterns everyday, or run across them only rarely, interpreting them may require a bit of preparation. But it's easy to lose track of the numbers for your microscope's camera constant, not to mention the bewildering array of lattice parameters and symmetries that one may encounter in the microscope. In that context, we describe overlays you might want to assemble for measuring camera constants, and for recognizing crystal systems most likely to yield electron powder diffraction patterns in your lab. Pulling this out of a drawer and/or computer folder thereafter might help you come up with quick answers, even if you haven't thought about analyzing diffraction data for quite a while.

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Mazzolini, Margaret, Janice Long et Rachel Webster. « Radio Continuum Maps of Southern Barred Spiral Galaxies ». International Astronomical Union Colloquium 157 (1996) : 239–41. http://dx.doi.org/10.1017/s0252921100049836.

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AbstractA sample of southern spiral galaxies are being observed at 20 and 13 cm with the Australia Telescope Compact Array in order to look for examples of anomalous outflows from the nuclear region. In this paper we discuss the radio continuum maps of the three barred spiral galaxies observed to date.

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Fan, X. D., et L. A. Bursill. « Stable Divergence Angles of a Magnetic Dipole Spiral Array ». Modern Physics Letters B 11, n^o 24 (20 octobre 1997) : 1069–75. http://dx.doi.org/10.1142/s0217984997001286.

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An analytical model is introduced for the experiment of Douady and Couder [Phys. Rev. Lett.68, 2098 (1992), where phyllotactic patterns appear as a dynamical result of the interaction between magnetic dipoles. The difference equation for the divergence angle (i.e. the angle between successive radial vectors) is obtained by solving the equations of motion with a second nearest neighbor (SNN) approximation. A one-dimensional map analysis as well as a comprehensive analytical proof shows that the divergence angle always converges to a single attractor regardless of the initial conditions. This attractor is approximately the Fibonacci angle(~ 138°) within variations due to a growth factor μ of the pattern. The system is proved to be stable with the SNN approximation. Further analysis with a third nearest neighbor approximation (TNN) shows extra linearly stable attractors may appear around the Lucas angle (~ 99.5°).

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Geng, Jingru, Xueguan Liu, Changrong Liu et Huiping Guo. « A unidirectional ultra‐wideband circularly polarized spiral antenna array ». Microwave and Optical Technology Letters 62, n^o 7 (2 mars 2020) : 2569–75. http://dx.doi.org/10.1002/mop.32340.

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Etellisi, Ehab A., Mohamed A. Elmansouri et Dejan S. Filipovic. « Antenna Systems for Simultaneous Transmit and Receive (STAR) Applications ». International Symposium on Microelectronics 2017, n^o 1 (1 octobre 2017) : 000590–94. http://dx.doi.org/10.4071/isom-2017-tha41_116.

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Abstract Several novel wideband co-polarized circulator-less monostatic antenna and array designs for co-channel simultaneous transmit and receive (STAR) applications are presented. The monostatic STAR apertures are demonstrated first by utilizing multi-arm spiral antennas where a set of arms is used for transmitting (TX) and the other set for receiving (RX). Then, square and hexagonal broadside STAR arrays utilizing closely-spaced spiral antennas are introduced. Finally, (quasi) omnidirectional circular STAR arrays based on phase modes orthogonality principles are realized using four wideband monocone antenna elements. The studied configurations are integrated with the proper beamforming networks to excite the desired modes of TX/RX operations leading to theoretically infinite isolation between TX and RX ports. Practically, the achieved isolation is limited by the electrical asymmetries of the used components. Overall, consistent wideband operation, high isolation, and decent far-field performance are achieved for all proposed STAR approaches.

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Mazzolini, Margaret, et Rachel Webster. « Preliminary Radio Continuum Maps of Three Spiral Galaxies ». Publications of the Astronomical Society of Australia 13, n^o 2 (mai 1996) : 107–20. http://dx.doi.org/10.1017/s1323358000020646.

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AbstractThe Australia Telescope Compact Array has been used in two 6 km configurations to make 12 hour observations of the radio continuum structure of three spiral galaxies at 1380 MHz and 2378 MHz. Radio maps of NGC 1792, 6300 and 1097 are presented here, as part of a survey to find examples of anomalous radio structures in spiral galaxies.

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HUANG, LONG, JUN MA, JUN TANG et FAN LI. « TRANSITION OF ORDERED WAVES IN NEURONAL NETWORK INDUCED BY DIFFUSIVE POISONING OF ION CHANNELS ». Journal of Biological Systems 21, n^o 01 (31 janvier 2013) : 1350002. http://dx.doi.org/10.1142/s0218339013500022.

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Normal physiological activities are often affected by some drugs, and some ion channels are blocked due to the katogene of drugs. This paper investigates the propagation of ordered waves in neuronal networks induced by diffusive poisoning, where the process is measured by increasing the number of neurons in the poisoned area of the networks. A coefficient of poisoning K is defined to measure the time units from one poisoned site to the adjacent site, a smaller K means that more neurons are poisoned in a certain period (a higher poisoning speed). A statistical factor of synchronization R in the two-dimensional array is defined to detect the transition of spiral waves induced by ion channel blocking. It is confirmed that the evolution of the spiral waves depends on the coefficient of poisoning K and number of poisoned neurons. Furthermore, breakup of the spirals is observed when weak channel noise is considered. Finally, the formation of the spiral wave induced by blocking the target wave with line defects is briefly discussed.

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Richter, Bernhard, Antje Aschendorff, Petra Lohnstein, Hartmut Husstedt, Heiner Nagursky et Roland Laszig. « Clarion 1.2® standard electrode array with partial space-filling positioner : radiological and histological evaluation in human temporal bones ». Journal of Laryngology & ; Otology 116, n^o 7 (juillet 2002) : 507–13. http://dx.doi.org/10.1258/002221502760132584.

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The purpose of this study was to evaluate whether use of a positioner for situating the Clarion 1.2® standard electrode array in close proximity to the modiolus, causes damage to fine intra-cochlear structures, and to provide a comparison with results obtained for insertions of the array performed without a positioner. The study was performed in seven freshly frozen human temporal bones. Electrode location and intra-cochlear trauma was analysed using cross-sectional imaging and histological analysis. Insertion of the Clarion® array did not reveal major trauma. The devices inserted with the positioner showed a consistently closer location of the electron array towards the modiolus, however, insertion resulted in significant displacement of both the electrode array and the positioner resulting in severe destruction of the basilar membrane and osseous spiral lamina along the length of the basal and middle turns. The devices inserted with the positioner resulted in major trauma to the basilar membrane and osseous spiral lamina. Therefore, systematic safety studies in larger samples of human temporal bones should be performed and the results carefully evaluated before implantation can be recommended unreservedly.

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Aldeman, Matthew R., et Ganesh Raman. « Experimental determination of the effects of boundary reflection on the angular resolution of microphone arrays ». Building Acoustics 25, n^o 3 (17 avril 2018) : 249–86. http://dx.doi.org/10.1177/1351010x18768746.

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The Rayleigh criterion has long been considered the standard criterion for angular resolution of imaging systems, including microphone arrays. However, advanced beamforming methods have been developed in the past 20 years that have dramatically improved the angular resolution of microphone array systems. In this investigation, the angular resolution performance of three scaled microphone arrays and one alternative array geometry were tested with both approximately free-field and reflective boundary conditions. All of the arrays were subjected to a thorough regimen of testing with broadband acoustic sources. Beamforming analysis was performed with the Delay-and-Sum, TIDY, DAMAS, DAMAS2, and CLEAN-SC algorithms. The Delay-and-Sum algorithm is shown to offer the lowest angular resolution performance because it does not separate the acoustic source map from the point spread function of the array. The DAMAS algorithm offers the greatest angular resolution because it numerically deconvolutes the acoustic source map from the point spread function. However, deconvolution-based algorithms (DAMAS and DAMAS2) were the most negatively affected by boundary reflection effects. The logarithmic spiral array is shown to offer versatile performance across a wide range of frequencies, while an alternative quasi-periodic array yields results that are highly frequency-dependent. It is demonstrated that this is because of gaps in the source-to-element differences coverage, and the gaps in coverage correspond to half-wavelengths of frequency bands with significantly lower angular resolution performance.

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Kuno, N., N. Nakai, K. Nishiyama, K. Sorai, T. Handa et T. Iga. « 5.16. CO mapping of barred spiral galaxies ». Symposium - International Astronomical Union 184 (1998) : 243–44. http://dx.doi.org/10.1017/s0074180900084783.

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We have made CO mapping observations of nearby barred spiral galaxies (NGC253, NGC3504, NGC4303, NGC4321, NGC6951, M83) with the Nobeyama 45-m telescope using the 2×2 SIS focal-plane array receiver. The purpose of this project is to investigate distribution and kinematics of molecular gas in barred spiral galaxies and the relation between star formation and them. We present some of the results (NGC3504 and NGC6951).

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Beck, R., M. Ehle, R. F. Haynes et J. I. Harnett. « ATCA Radio Polarization Observations of NGC 1566 and NGC 1672 ». Symposium - International Astronomical Union 158 (1994) : 358–60. http://dx.doi.org/10.1017/s0074180900107910.

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NGC 1566 and NGC 1672 have successfully been observed in radio continuum at 6 cm (26″ HPBW) with the Australia Telescope Compact Array (ATCA) using a 375-m array. We have detected for the first time with this telescope linearly polarized radio emission from two southern hemisphere spiral galaxies, NGC 1566 and NGC 1672.

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Wu, Yunjing, Zheng Cai, Fengwu Sun, Fuyan Bian, Xiaojing Lin, Zihao Li, Mingyu Li et al. « The Identification of a Dusty Multiarm Spiral Galaxy at z = 3.06 with JWST and ALMA ». Astrophysical Journal Letters 942, n^o 1 (27 décembre 2022) : L1. http://dx.doi.org/10.3847/2041-8213/aca652.

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Abstract Spiral arms serve crucial purposes in star formation and galaxy evolution. In this paper, we report the identification of “A2744-DSG-z3,” a dusty, multiarm spiral galaxy at z = 3.059 using the James Webb Space Telescope (JWST) NIRISS imaging and grism spectroscopy. A2744-DSG-z3 was discovered as a gravitationally lensed submillimeter galaxy with the Atacama Large Millimeter/submillimeter Array (ALMA). This is the most distant stellar spiral structure seen thus far, consistent with cosmological simulations that suggest z ≈ 3 as the epoch when spirals emerge. Thanks to the gravitational lensing and excellent spatial resolution of JWST, the spiral arms are resolved with a spatial resolution of ≈290 pc. Based on spectral energy distribution fitting, the spiral galaxy has a delensed star formation rate of 85 ± 30 M ⊙ yr−1, and a stellar mass of ≈1010.6 M ⊙, indicating that A2744-DSG-z3 is a main-sequence galaxy. After fitting the spiral arms, we find a stellar effective radius (R e,star) of 5.0 ± 1.5 kpc. Combining with ALMA measurements, we find that the effective radii ratio between dust and stars is ≈0.4, similar to those of massive star‐forming galaxies (SFGs) at z ∼ 2, indicating a compact dusty core in A2744-DSG-z3. Moreover, this galaxy appears to be living in a group environment: including A2744-DSG-z3, at least three galaxies at z = 3.05–3.06 are spectroscopically confirmed by JWST/NIRISS and ALMA, residing within a lensing-corrected projected scale of ≈70 kpc. This, along with the asymmetric brightness profile, further suggests that the spiral arms may be triggered by minor-merger events at z ≳ 3.

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LI, FAN, et JUN MA. « SELECTION OF SPIRAL WAVE IN THE COUPLED NETWORK UNDER GAUSSIAN COLORED NOISE ». International Journal of Modern Physics B 27, n^o 21 (30 juillet 2013) : 1350115. http://dx.doi.org/10.1142/s0217979213501154.

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The selection and breakup of spiral wave in a coupled network is investigated by imposing Gaussian colored noise on the network, respectively. The dynamics of each node of the network is described by a simplified Chua circuit, and nodes are uniformly placed in a two-dimensional array with nearest-neighbor connection type. The transition of spiral wave is detected by changing the coupling intensity, intensity and correlation time τ in the noise. A statistical variable is used to discern the parameter region for breakup of spiral wave and robustness to external noise. Spiral waves emerge in the network when the network with structure of complex-periodic and chaotic properties. It is found that asymmetric coupling can induce deformation of spiral wave, stronger intensity or smaller correlation time in noise does cause breakup of the spiral wave.

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Stil, Jeroen M., Marita Krause, Lydia Mitchell, Rainer Beck et A. Russell Taylor. « The integrated polarization of spiral galaxies ». Proceedings of the International Astronomical Union 4, S259 (novembre 2008) : 543–44. http://dx.doi.org/10.1017/s174392130903124x.

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AbstractWe present deep observations of polarized radio emission of distant spiral galaxies with the Effelsberg 100-m telescope† at 4.8 GHz. These cross scans with sensitivity of 50 μJy or better open the possibility of a statistical study of magnetic field properties and internal Faraday rotation as a function of inclination for a large sample of unresolved galaxies. The Square Kilometre Array (SKA) will be able to detect polarization of spiral galaxies to high redshift, probing the evolution of magnetic fields in disk galaxies over cosmic time.

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Zhang, Zhi-Ya, Peng Huang, Shao-Li Zuo, Jia-Yue Zhao et Guang Fu. « Broadband circularly polarized spiral antenna array using sequentially rotated technique ». International Journal of Applied Electromagnetics and Mechanics 48, n^o 4 (31 juillet 2015) : 379–86. http://dx.doi.org/10.3233/jae-140151.

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Serhir, Mohammed, et Regis Guinvarc'h. « A Low-Profile Cavity-Backed Dual-Polarized Spiral Antenna Array ». IEEE Antennas and Wireless Propagation Letters 12 (2013) : 524–27. http://dx.doi.org/10.1109/lawp.2013.2257654.

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Liu, Xingxing, Xiang Li et Zhiying Ren. « Miniaturized Spiral Metamaterial Array for a Ventilated Broadband Acoustic Absorber ». Shock and Vibration 2020 (2 novembre 2020) : 1–6. http://dx.doi.org/10.1155/2020/8887571.

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The high-efficiency and broadband acoustic reduction performance in a miniaturized free-flow structure remains challenging in acoustic engineering applications due to the contradiction of ventilation and acoustic reduction performance. Traditional acoustic absorbers can sufficiently attenuate acoustic wave, but meanwhile, block fluid flow due to the longitudinal nature of acoustic waves that can transmit among any small holes. Although different types of ventilated metamaterial absorbers (VMAs) with proper reduction and ventilation performance have been demonstrated recently, their insufficiencies lie in small open-area ratios, not efficient-enough reduction performance, bulky structure, and narrow working band. To further solve existing defects, a ventilated broadband absorber with the miniaturized metamaterial structure has been proposed. The designed absorber consists of miniaturized Archimedean spiral units, which can be easily stacked to achieve broadband and ventilated performance. This work opens up possibilities for practical acoustic applications where both noise control and ventilation are required, especially in a small space.

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Ling-Ling, Xie, et Gao Ji-Hua. « Size transition of spiral waves using the pulse array method ». Chinese Physics B 19, n^o 6 (juin 2010) : 060516. http://dx.doi.org/10.1088/1674-1056/19/6/060516.

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