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Journal articles on the topic 'Very Small Array'

Author: Grafiati

Published: 4 June 2021

Last updated: 10 February 2022

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1

Scott, Paul F. "The Very Small Array." Symposium - International Astronomical Union 201 (2005): 17–22. http://dx.doi.org/10.1017/s0074180900216057.

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The VSA is a 14-element aperture-synthesis telescope for mapping structure in the Cosmic Microwave Background which is now being commissioned at the Teide Observatory, Tenerife. It operates at frequencies between 26 and 36 GHz, with a bandwidth of 1.5GHz. Its elements track the sky, providing fringe-rate discrimination of any instrumental effects such as antenna cross-talk or ground radiation. The instrument incorporates a single-baseline interferometer comprising two large (3.7m) dishes, which is used to provide concurrent (and same frequency) pointed flux measurements of point sources in the VSA fields, the positions of these source having been obtained previously from survey observations made with the Cambridge Ryle Telescope at 15 GHz. The VSA is now completing its commissioning programme and it will start routine observations in September 2000.

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2

Rusholme, Ben. "Commissioning the Very Small Array." Symposium - International Astronomical Union 201 (2005): 512–13. http://dx.doi.org/10.1017/s0074180900216914.

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The Very Small Array (VSA) is a fourteen-element interferometer for sensitive measurement of the CMB anisotropies on scales of three degrees to ten arcminutes. The telescope is now observing on site in Tenerife after a period of commissioning, including the first map of the Sunyaev-Zel'dovich effect in the Coma cluster.A distinguishing feature of the instrument is that each antenna in the array tracks quasi-independently, providing a characteristic fringe rate per baseline which can be used to reject many systematics. This effect has been optimised in the antenna array design.

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3

Slosar, Anže, and Clive Dickinson. "The Very Small Array: Observations and Latest Results." Symposium - International Astronomical Union 216 (2005): 67–74. http://dx.doi.org/10.1017/s0074180900196512.

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The Very Small Array (VSA) is a unique interferometric telescope operating at 33 GHz at Tenerife. It has the ability to measure fluctuations in the CMB over a large range of angular scales by means of three main array configurations: compact, extended and super-extended. These angular scales correspond to the multipole range ℓ = 150 —2500. Here we present new results from further observations of the extended array (February 2002 - June 2003). We cover ℓ-values up to ℓ ∼ 1600, thus doubling the ℓ-range of WMAP. The resulting power spectrum in the ℓ-range 800 – 1600 has very low noise coupled with good ℓ-resolution (Δℓ ∼ 80). Furthermore, the use of independently tracking aerials along with the dedicated source subtraction baseline allows unprecedented control of systematics. The latter is essential, since discrete sources are the dominant foreground at these angular scales. These measurements over larger ℓ-ranges are important in confirming the present cosmological paradigm and breaking degeneracies in the extraction of cosmological parameters.

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4

Smith, Sarah, Graça Rocha, Anthony Challinor, Richard A. Battye, Pedro Carreira, Kieran Cleary, Rod D. Davies, et al. "Estimating the bispectrum of the Very Small Array data." Monthly Notices of the Royal Astronomical Society 352, no. 3 (August 11, 2004): 887–902. http://dx.doi.org/10.1111/j.1365-2966.2004.07885.x.

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5

GRAINGE, KEITH. "THE VERY SMALL ARRAY: LATEST RESULTS AND FUTURE PLANS." Modern Physics Letters A 19, no. 13n16 (May 30, 2004): 1009–18. http://dx.doi.org/10.1142/s021773230401429x.

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The VSA is an aperture synthesis array dedicated to measuring anisotropies in the Cosmic Microwave Background (CMB). It has observed in two configurations to measure the CMB power spectrum from ℓ=150–1600, detecting the first three acoustic peaks at good signal-to-noise. We now plan to enhance the telescope to allow observation at higher ℓ. This will allow measurement of the fourth and subsequent peaks and will allow us to break degeneracies that exist at present between cosmological parameters. In addition we will investigate the excess power detected by CBI at ℓ > 2000 and will conduct high-sensitivity searches for topological defects.

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6

Kramer, Olivier, Tarek Djerafi, and Ke Wu. "Very Small Footprint 60 GHz Stacked Yagi Antenna Array." IEEE Transactions on Antennas and Propagation 59, no. 9 (September 2011): 3204–10. http://dx.doi.org/10.1109/tap.2011.2161562.

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7

Portuondo, M. M. "An Introduction to the Very Small Peripheral Array (VSPA™)." Microelectronics International 12, no. 2 (May 1995): 60–61. http://dx.doi.org/10.1108/eb044565.

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8

Watson, R. A., P. Carreira, K. Cleary, R. D. Davies, R. J. Davis, C. Dickinson, K. Grainge, et al. "First results from the Very Small Array -- I. Observational methods." Monthly Notices of the Royal Astronomical Society 341, no. 4 (June 1, 2003): 1057–165. http://dx.doi.org/10.1046/j.1365-8711.2003.06338.x.

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9

Heaney, Kevin D., and W. A. Kuperman. "Very long-range source localization with a small vertical array." Journal of the Acoustical Society of America 104, no. 4 (October 1998): 2149–59. http://dx.doi.org/10.1121/1.423727.

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10

Savage, Richard, Richard A. Battye, Pedro Carreira, Kieran Cleary, Rod D. Davies, Richard J. Davis, Clive Dickinson, et al. "Searching for non-Gaussianity in the Very Small Array data." Monthly Notices of the Royal Astronomical Society 349, no. 3 (April 2004): 973–82. http://dx.doi.org/10.1111/j.1365-2966.2004.07578.x.

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11

Bachrach, Ran, and Tapan Mukerji. "Portable dense geophone array for shallow and very shallow 3D seismic reflection surveying: Part 2—3D imaging tests." GEOPHYSICS 69, no. 6 (November 2004): 1456–69. http://dx.doi.org/10.1190/1.1836819.

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In part I of this paper we demonstrate how the use of a portable dense geophone array increases S/N ratio and the ability to record faint near‐surface reflections. The dense array can also be used as an approximate acoustical lens with appropriate prestack imaging techniques, similar to those used in medical imaging and nondestructive testing. Such use of the array provides flexibility when imaging with sparse shot distributions and improves the overall resolution of the array. We show how, with prestack focusing, one can extend the subsurface coverage beyond conventional common‐midpoint (CMP) coverage. We study optimal imaging configurations and show that although the effective aperture of the array is reduced when focusing off‐center targets, we can still image small targets adequately. Maximum aperture and therefore best target definition occur when the source and geophone arrays are on top of the target. Both synthetic and field results show that the limited‐aperture array can image very small targets with resolution of 0.25 m in three dimensions. We also demonstrate that different acquisition geometries should be used when imaging continuous geological targets versus small point diffractors.

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12

Malkin, Robert A., and Bradford D. Pendley. "Construction of a very high-density extracellular electrode array." American Journal of Physiology-Heart and Circulatory Physiology 279, no. 1 (July 1, 2000): H437—H442. http://dx.doi.org/10.1152/ajpheart.2000.279.1.h437.

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Cellular activation mapping (specifying in time and space the electrical activation sequence of cells) is a well-established basic research tool in cardiac, neural, and gastric physiology. Much recent research in cardiac mapping has focused on large arrays (>200 electrodes) with small electrodes (<500 μm). Construction of such arrays using standard techniques is tedious and yields irregular electrode spacing. We present a novel construction technique that rapidly produces large arrays with regularly spaced small electrodes. For methods, fine-pitch copper ribbon cables, insulated with either polyvinylchloride (PVC) or polyimide (flexible printed circuit; FPC), were assembled together such that the active surface was the cut end of the cable. The cut end was sanded and polished, then coated with silver and sometimes silver chloride. Once completed, the alternating current (AC) root-mean-square (rms) potential was measured between two adjacent, individual electrodes. Polarization testing was conducted according to a previously reported protocol (Witkowski FX and Penkoske PA. J Electrocardiol 21: 273–282, 1988). Activation mapping was conducted in the open-chest guinea pig with both pacing- and defibrillation- strength stimuli. In terms of results, four PVC and three FPC arrays were constructed, ranging from 4 to 400 electrodes. Two hours of labor were needed to create a complete electrode array, independent of the number of electrodes, including connectors and silver/silver chloride coating. As expected, the addition of a silver/silver chloride coating significantly reduced (0.76–0.42 mV, P < 0.001) the AC rms potential difference between two electrodes. A nearly immediate recovery of the potential difference between adjacent pairs of silver/silver chloride electrodes was observed after defibrillation stimuli.

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13

Rubino-Martin, J. A., R. Rebolo, P. Carreira, K. Cleary, R. D. Davies, R. J. Davis, C. Dickinson, et al. "First results from the Very Small Array -- IV. Cosmological parameter estimation." Monthly Notices of the Royal Astronomical Society 341, no. 4 (June 1, 2003): 1084–92. http://dx.doi.org/10.1046/j.1365-8711.2003.06494.x.

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14

Manges, John B., John W. Silvestro, and Kezhong Zhao. "Finite-element analysis of infinite and finite arrays." International Journal of Microwave and Wireless Technologies 4, no. 3 (May 24, 2012): 357–64. http://dx.doi.org/10.1017/s1759078712000463.

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This paper considers and compares the numerical characterization of regular planar antenna arrays from two viewpoints. In the case where the array is sufficiently large, the well-known infinite array idealization applies and a very efficient simulation method is presented which combines array theory with a specialized form of the finite-element method called the transfinite element method (TFEM). Alternatively, a more direct approach is discussed in which the entire antenna array is simulated as a finite structure using recent advances in the domain decomposition method (DDM). Taken together, the two methods provide a comprehensive simulation method for regular arrays from small order to very large order.

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15

Pourmohammadi, Peyman, Vladimir Volski, and Guy A. E. Vandenbosch. "Medium-Sized Highly Coupled Planar Arrays with Maximum Aperture Efficiency." Sensors 21, no. 17 (September 3, 2021): 5925. http://dx.doi.org/10.3390/s21175925.

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This paper presents a technique to design strongly coupled planar arrays with very high aperture efficiency. The key innovation is that, based on an irregular 2 × 1 array, very compact medium-sized arrays of size 2 × 2, 2 × 4, and 2 × 6 are constructed with very strong and constructive mutual coupling between the elements. In this way, a maximum aperture efficiency is reached for a given footprint of the array. The occupied space of the antenna in comparison with conventional linear patch arrays is studied. A prototype 2 × 4 array operating around 5.8 GHz is designed, fabricated, built, and measured. The results show a large bandwidth of 20% and a very high aperture efficiency of 100%, which is the largest found in the literature for similarly sized arrays. These results are important in view of the future Internet of Things, where small and medium-sized arrays are planned to be mounted on numerous devices where a very limited physical area is available.

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16

Slosar, A., P. Carreira, K. Cleary, R. D. Davies, R. J. Davis, C. Dickinson, R. Genova-Santos, et al. "Cosmological parameter estimation and Bayesian model comparison using Very Small Array data." Monthly Notices of the Royal Astronomical Society 341, no. 4 (June 1, 2003): L29—L34. http://dx.doi.org/10.1046/j.1365-8711.2003.06564.x.

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17

Hara, S., and T. Tokumitsu. "Very small control modules with line unified FET configuration for array processing." IEEE Transactions on Microwave Theory and Techniques 39, no. 1 (1991): 117–23. http://dx.doi.org/10.1109/22.64614.

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18

Rebolo, Rafael, Richard A. Battye, Pedro Carreira, Kieran Cleary, Rod D. Davies, Richard J. Davis, Clive Dickinson, et al. "Cosmological parameter estimation using Very Small Array data out to ℓ= 1500." Monthly Notices of the Royal Astronomical Society 353, no. 3 (August 23, 2004): 747–59. http://dx.doi.org/10.1111/j.1365-2966.2004.08102.x.

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19

Szalai, S., K. Szokoli, E. Prácser, M. Metwaly, M. Zubair, and L. Szarka. "An alternative way in electrical resistivity prospection: the quasi-null arrays." Geophysical Journal International 220, no. 3 (December 13, 2019): 1463–80. http://dx.doi.org/10.1093/gji/ggz518.

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SUMMARY While traditional geoelectric array configurations, such as the Wenner–Schlumberger or the dipole–dipole, can provide very good images of 1-D or robust 2-D structures, they are not sufficiently sensitive to those inhomogeneities that have a small effect on the surface electrical potential distribution. The detection and description of such inhomogeneities become possible by applying quasi-null arrays, which provide very small (close to zero) signals above a homogeneous half-space. The imaging properties of the members of an array series containing such arrays, the so-called γ11n arrays (n = 1–7), are demonstrated and compared to those of the most popular traditional arrays. Although the field applicability of the quasi-null arrays has been heavily questioned, it was demonstrated by our quasi-field analogue modelling experiments. The quasi-field tests also validated all of the numerical modelling results as follows: (1) many or all of the γ11n arrays were able to detect prisms and vertical sheets located at depths larger than those detectable by traditional geoelectric arrays, including the optimized Stummer configuration; (2) the horizontal resolution of the γ11n arrays proved to be better than the horizontal resolution of traditional arrays; (3) with n increasing, the γ11n arrays proved to be less sensitive to 1-D, but more sensitive to 2-D bodies. In case of high n values, the γ11n arrays may even be entirely insensitive to any 1-D structure. On the basis of the quasi-field experiments, γ11n arrays are expected to be very efficient to indicate bodies, or variations in time that only have a small impact on the surface electrical potential distribution (e.g. caves, mines, tunnels, tubes, cables, fractures, dykes), or small changes in the subsurface conditions (monitoring of dams or waste deposits). Data acquisition by both a traditional and a γ11n array, individual inversion of their data, and a joint interpretation of the results are recommended to obtain both a robust image and fine details of the subsurface.

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20

Demierre, Michel, Sergio Pesenti, Javad Frounchi, Pierre-André Besse, and Radivoje S. Popović. "Reference magnetic actuator for self-calibration of a very small Hall sensor array." Sensors and Actuators A: Physical 97-98 (April 2002): 39–46. http://dx.doi.org/10.1016/s0924-4247(01)00857-3.

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21

Tibbs, Christopher T., Robert A. Watson, Clive Dickinson, Rodney D. Davies, Richard J. Davis, Simon Buckmaster, Carlos del Burgo, et al. "Very Small Array observations of the anomalous microwave emission in the Perseus region." Monthly Notices of the Royal Astronomical Society 402, no. 3 (March 1, 2010): 1969–79. http://dx.doi.org/10.1111/j.1365-2966.2009.16023.x.

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22

Lancaster, K., R. Genova-Santos, N. Falcon, K. Grainge, C. Gutierrez, R. Kneissl, P. Marshall, et al. "Very Small Array observations of the Sunyaev-Zel'dovich effect in nearby galaxy clusters." Monthly Notices of the Royal Astronomical Society 359, no. 1 (May 1, 2005): 16–30. http://dx.doi.org/10.1111/j.1365-2966.2005.08696.x.

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23

Teklehaimanot, Yemane Ghebremedhin, Sinshaw Bekelle, and Mohammed Ismail. "Performance Evaluation of Fractal Array Antenna for Small Satellite Applications." Indonesian Journal of Electrical Engineering and Computer Science 3, no. 2 (August 1, 2016): 356. http://dx.doi.org/10.11591/ijeecs.v3.i2.pp356-368.

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<p class="Default">The possible antenna which can be integrated with relatively large flat structure of solar panel of small satellites is patch antenna. The main problem of common Microstrip patch antennas is that they only operate at one or two frequencies, restricting the number of bands that equipment is capable of supporting. Another issue is that, due to the very strict space that a solar panel has, setting up more antenna array is very difficult. To reduce these problems, the use of fractal shaped antennas integrated on solar cells will be analyzed. The small satellite applications demand a high efficient multi-band antenna with a very compact size. A 2x2 Sierpinski Fractal antenna array is modeled and simulated using HFSS. The proposed work has resulted in multiband operation 10.2 GHz and 18.3GHz with increased bandwidth and radiation characteristics betterment, with added advantage of light weight and smaller dimension which is important where cost to payload is a constraint in satellites.</p>

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24

Xu, Rui, Sheng Ma, Yaohua Wang, Xinhai Chen, and Yang Guo. "Configurable Multi-directional Systolic Array Architecture for Convolutional Neural Networks." ACM Transactions on Architecture and Code Optimization 18, no. 4 (December 31, 2021): 1–24. http://dx.doi.org/10.1145/3460776.

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The systolic array architecture is one of the most popular choices for convolutional neural network hardware accelerators. The biggest advantage of the systolic array architecture is its simple and efficient design principle. Without complicated control and dataflow, hardware accelerators with the systolic array can calculate traditional convolution very efficiently. However, this advantage also brings new challenges to the systolic array. When computing special types of convolution, such as the small-scale convolution or depthwise convolution, the processing element (PE) utilization rate of the array decreases sharply. The main reason is that the simple architecture design limits the flexibility of the systolic array. In this article, we design a configurable multi-directional systolic array (CMSA) to address these issues. First, we added a data path to the systolic array. It allows users to split the systolic array through configuration to speed up the calculation of small-scale convolution. Second, we redesigned the PE unit so that the array has multiple data transmission modes and dataflow strategies. This allows users to switch the dataflow of the PE array to speed up the calculation of depthwise convolution. In addition, unlike other works, we only make a few changes and modifications to the existing systolic array architecture. It avoids additional hardware overheads and can be easily deployed in application scenarios that require small systolic arrays such as mobile terminals. Based on our evaluation, CMSA can increase the PE utilization rate by up to 1.6 times compared to the typical systolic array when running the last layers of ResNet-18. When running depthwise convolution in MobileNet, CMSA can increase the utilization rate by up to 14.8 times. At the same time, CMSA and the traditional systolic arrays are similar in area and energy consumption.

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25

Li, Yuan Xun, Huai Wu Zhang, Ying Li Liu, and Jie Li. "A Magnetic Array Fabricated by a Novel Process Constructed with Photosensitive Polyimide-Ferrite Nanocomposite." Advanced Materials Research 499 (April 2012): 3–6. http://dx.doi.org/10.4028/www.scientific.net/amr.499.3.

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The authors report an approach to the fabrication of a periodic magnetic array using photosensitive polyimide-barium ferrite nanocomposite. These patterns are shaped by a some-like imprint technique, under the interactions between the magnetic nanoparticles and permanent magnetic mold. Scanning electron microscopy has been used to characterize the magnetic array and well-defined structures with magnetic arrays are obtained. The diameter of each dot is as small as 52um. The presented concept leads to a realization of a magnetic array, which offers advances in achieving micrometer-scale patterns with a very low cost and simple process.

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26

Hollis, J. M., J. A. Pedelty, L. E. Snyder, P. R. Jewell, F. J. Lovas, Patrick Palmer, and S. ‐Y Liu. "A Sensitive Very Large Array Search for Small‐Scale Glycine Emission toward OMC‐1." Astrophysical Journal 588, no. 1 (May 2003): 353–59. http://dx.doi.org/10.1086/373945.

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27

Scott, P. F., P. Carreira, K. Cleary, R. D. Davies, R. J. Davis, C. Dickinson, K. Grainge, et al. "First results from the Very Small Array -- III. The cosmic microwave background power spectrum." Monthly Notices of the Royal Astronomical Society 341, no. 4 (June 1, 2003): 1076–83. http://dx.doi.org/10.1046/j.1365-8711.2003.06354.x.

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28

Taylor, A. C., P. Carreira, K. Cleary, R. D. Davies, R. J. Davis, C. Dickinson, K. Grainge, et al. "First results from the Very Small Array -- II. Observations of the cosmic microwave background." Monthly Notices of the Royal Astronomical Society 341, no. 4 (June 1, 2003): 1066–75. http://dx.doi.org/10.1046/j.1365-8711.2003.06493.x.

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29

Maisinger, Klaus, M. P. Hobson, Richard D. E. Saunders, and Keith J. B. Grainge. "Maximum-likelihood astrometric geometry calibration of interferometric telescopes: application to the Very Small Array." Monthly Notices of the Royal Astronomical Society 345, no. 3 (November 2003): 800–808. http://dx.doi.org/10.1046/j.1365-8711.2003.06995.x.

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30

Cleary, Kieran A., Angela C. Taylor, Elizabeth Waldram, Richard A. Battye, Clive Dickinson, Rod D. Davies, Richard J. Davis, et al. "Source subtraction for the extended Very Small Array and 33-GHz source count estimates." Monthly Notices of the Royal Astronomical Society 360, no. 1 (June 2005): 340–53. http://dx.doi.org/10.1111/j.1365-2966.2005.09037.x.

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31

Thomas, E. V., K. H. Phillippy, B. Brahamsha, D. M. Haaland, J. A. Timlin, L. D. H. Elbourne, B. Palenik, and I. T. Paulsen. "Statistical Analysis of Microarray Data with Replicated Spots: A Case Study withSynechococcusWH8102." Comparative and Functional Genomics 2009 (2009): 1–11. http://dx.doi.org/10.1155/2009/950171.

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Until recently microarray experiments often involved relatively few arrays with only a single representation of each gene on each array. A complete genome microarray with multiple spots per gene (spread out spatially across the array) was developed in order to compare the gene expression of a marine cyanobacterium and a knockout mutant strain in a defined artificial seawater medium. Statistical methods were developed for analysis in the special situation of this case study where there is gene replication within an array and where relatively few arrays are used, which can be the case with current array technology. Due in part to the replication within an array, it was possible to detect very small changes in the levels of expression between the wild type and mutant strains. One interesting biological outcome of this experiment is the indication of the extent to which the phosphorus regulatory system of this cyanobacterium affects the expression of multiple genes beyond those strictly involved in phosphorus acquisition.

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Dong, Jian, Ronghua Shi, Wentai Lei, and Ying Guo. "Minimum Redundancy MIMO Array Synthesis by means of Cyclic Difference Sets." International Journal of Antennas and Propagation 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/323521.

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Antenna array synthesis is an important issue in MIMO radars. By judiciously designing antenna positions, one can create a very long virtual array steering vector with a small number of antennas and therefore achieve very high spatial resolution at a small cost. This paper presents a combinatorial methodology based on cyclic difference sets (CDSs) for minimum redundancy (MR) MIMO array synthesis which seeks to maximize the virtual array aperture for a given number of antennas. First, the key features of CDSs and the CDS-based MR-MIMO layouts are described. Then, the analytical expression of the maximum contiguous virtual array aperture is derived. Further, based on this expression, an enumerative shifting procedure is developed for identifying the optimal CDS-based MR-MIMO layout. Selected examples are analyzed to point out the computational effectiveness of the CDS-based MR-MIMO array synthesis.

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Dyadyuk, Val, Xiaojing Huang, Leigh Stokes, and Joseph Pathikulangara. "Implementation of wideband digital beam forming in the E-band." International Journal of Microwave and Wireless Technologies 3, no. 3 (April 19, 2011): 259–66. http://dx.doi.org/10.1017/s1759078711000468.

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This paper reports the test results of a small-scale prototype that implements a digitally beam-formed phased antenna array in the E-band. A four-channel dual-conversion receive RF module for 71–76 GHz frequency band has been developed and integrated with a linear end-fire antenna array. Wideband frequency-domain angle-of-arrival estimation and beam-forming algorithms were developed and implemented using Orthogonal Frequency Division Multiplexing (OFDM) with Quadrature Phase-Shift Keying (QPSK) at 1 Gbps. Measured performance is very close to the simulated results and experimental data for an analogue-beam-formed array. This work is a stepping stone toward practical realization of larger hybrid arrays in the E-band.

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34

Grainge, K., P. Carreira, K. Cleary, R. D. Davies, R. J. Davis, C. Dickinson, R. Genova-Santos, et al. "The cosmic microwave background power spectrum out to = 1400 measured by the Very Small Array." Monthly Notices of the Royal Astronomical Society 341, no. 4 (June 1, 2003): L23—L28. http://dx.doi.org/10.1046/j.1365-8711.2003.06563.x.

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35

Cleary, Kieran A., Angela C. Taylor, Elizabeth Waldram, Richard A. Battye, Clive Dickinson, Rod D. Davies, Richard J. Davis, et al. "Erratum: Source subtraction for the extended Very Small Array and 33-GHz source count estimates." Monthly Notices of the Royal Astronomical Society 386, no. 3 (May 2008): 1759–60. http://dx.doi.org/10.1111/j.1365-2966.2008.13184.x.

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36

Wen-Long, Tian, Li Gao-Peng, Zhao Bin, and Xu Rongqing. "Target Bearing Estimation for Ship-Borne HFSWR Using Doppler Effect and Very Small Antenna Array." IEEE Journal of Oceanic Engineering 46, no. 3 (July 2021): 919–26. http://dx.doi.org/10.1109/joe.2020.3039354.

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37

Caton, Ross C., Gary L. Pavlis, David J. Thomson, and Frank L. Vernon. "Methods for the robust computation of the long-period seismic spectrum of broad-band arrays." Geophysical Journal International 222, no. 3 (May 20, 2020): 1480–501. http://dx.doi.org/10.1093/gji/ggaa218.

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SUMMARY We describe array methods to search for low signal-to-noise ratio (SNR) signals in long-period seismic data using Fourier analysis. This is motivated by published results that find evidence of solar free oscillations in the Earth's seismic hum. Previous work used data from only one station. In this paper, we describe methods for computing spectra from array data. Arrays reduce noise level through averaging and provide redundancy that we use to distinguish coherent signal from a random background. We describe two algorithms for calculating a robust spectrum from seismic arrays, an algorithm that automatically removes impulsive transient signals from data, a jackknife method for estimating the variance of the spectrum, and a method for assessing the significance of an entire spectral band. We show examples of their application to data recorded by the Homestake Mine 3-D array in Lead, SD and the Piñon Flats PY array. These are two of the quietest small aperture arrays ever deployed in North America. The underground Homestake data has exceptionally low noise, and the borehole sensors of the PY array also have very low noise, making these arrays well suited to finding very weak signals. We find that our methods remove transient signals effectively from the data so that even low-SNR signals in the seismic background can be found and tested. Additionally, we find that the jackknife variance estimate is comparable to the noise floor, and we present initial evidence for solar g-modes in our data through the T2 test, a multivariate generalization of Student's t-test.

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Waldrop, Lindsay D., Miranda Hann, Amy K. Henry, Agnes Kim, Ayesha Punjabi, and M. A. R. Koehl. "Ontogenetic changes in the olfactory antennules of the shore crab, Hemigrapsus oregonensis , maintain sniffing function during growth." Journal of The Royal Society Interface 12, no. 102 (January 2015): 20141077. http://dx.doi.org/10.1098/rsif.2014.1077.

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Malacostracan crustaceans capture odours using arrays of chemosensory hairs (aesthetascs) on antennules. Lobsters and stomatopods have sparse aesthetascs on long antennules that flick with a rapid downstroke when water flows between the aesthetascs and a slow return stroke when water is trapped within the array (sniffing). Changes in velocity only cause big differences in flow through an array in a critical range of hair size, spacing and speed. Crabs have short antennules bearing dense arrays of flexible aesthetascs that splay apart during downstroke and clump together during return. Can crabs sniff, and when during ontogeny are they big enough to sniff? Antennules of Hemigrapsus oregonensis representing an ontogenetic series from small juveniles to adults were used to design dynamically scaled physical models. Particle image velocimetry quantified fluid flow through each array and showed that even very small crabs capture a new water sample in their arrays during the downstroke and retain that sample during return stroke. Comparison with isometrically scaled antennules suggests that reduction in aesthetasc flexural stiffness during ontogeny, in addition to increase in aesthetasc number and decrease in relative size, maintain sniffing as crabs grow. Sniffing performance of intermediate-sized juveniles was worse than for smaller and larger crabs.

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Zalipaev, V. V., and S. Yu Kosulnikov. "Guided electromagnetic waves for periodic arrays of thin metallic wires near an interface between two dielectric media." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 475, no. 2227 (January 16, 2019): 20180399. http://dx.doi.org/10.1098/rspa.2018.0399.

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Guided localized electromagnetic waves propagating along one-dimensional (1D) arrays of thin metallic parallel wires, finite and infinite, are studied. The arrays are embedded into the upper dielectric half-space close to the interface separating it from the lower dielectric medium with different permittivity and the same permeability. Firstly, a dependence of resonance frequencies of excited wave modes for finite array with respect to the array height above the interface is studied. The array is excited by a normally incident plane wave. It is important that the order of the resonance modes changes if the distance between the array and the interface becomes small. An analysis, based on the Pocklington system of integral equations to evaluate resonance frequencies and compute the fields of excited modes above the array, was applied. This approach is based on the longwave approximation of thin wires. Secondly, the waves propagating along infinite 1D array of thin metallic wires that is close to the interface are studied. Dispersion curves are presented for the lowest case of half-wave resonance for different heights of the array over the interface. When the array approaches very close to the interface an anomalous dispersion is observed. The results of the numerical analysis were tested against computations obtained by means of other independent CST Studio Suite simulations.

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40

Waldram, E. M., and G. G. Pooley. "Surveying the foreground sources for the Very Small Array, with the Ryle Telescope at 15 GHz." Symposium - International Astronomical Union 201 (2005): 525–26. http://dx.doi.org/10.1017/s0074180900216975.

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The three fields chosen for the first observations with the Very Small Array (VSA), a total area of ˜ 200 deg2, are being surveyed with the Ryle Telescope at 15 GHz. This is the only wide-field survey at a comparable radio frequency; its purpose is to investigate the source population and to define a catalogue of the foreground sources which must be monitored by the VSA during its observations. We present preliminary source counts.

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HARRISON, BRIAN F. "BROADBAND MATCHED-FIELD LOCALIZATION PERFORMANCE IN UNCERTAIN ENVIRONMENTS USING A SHORT ARRAY." Journal of Computational Acoustics 09, no. 03 (September 2001): 957–72. http://dx.doi.org/10.1142/s0218396x01000863.

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Typical applications of matched-field localization use low frequency signals received on large aperture vertical-arrays. However, small aperture arrays are much more practical for real-world systems and must be considered. Additionally, any practical localization algorithm must also be robust to environmental mismatch. In this paper, we present the broadband L∞-norm estimator for robust matched-field localization of mid-frequency signals (e.g., 800–4000 Hz) received on very short aperture vertical-arrays. Realistic simulation results are presented using broadband signals in the band of 1000–3000 Hz received on a 3 m vertical array which demonstrate the substantial performance gains in using the L∞-norm estimator over the asymptotically-optimal maximum a posteriori estimator and the conventional Bartlett processor. Experimental data results in an uncertain shallow-water environment using a 2.13 m vertical array in the band of 3000–4000 Hz are also presented.

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Dickinson, Clive, Richard A. Battye, Pedro Carreira, Kieran Cleary, Rod D. Davies, Richard J. Davis, Ricardo Genova-Santos, et al. "High-sensitivity measurements of the cosmic microwave background power spectrum with the extended Very Small Array." Monthly Notices of the Royal Astronomical Society 353, no. 3 (August 23, 2004): 732–46. http://dx.doi.org/10.1111/j.1365-2966.2004.08206.x.

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43

Genova-Santos, R., J. A. Rubino-Martin, R. Rebolo, K. Cleary, R. D. Davies, R. J. Davis, C. Dickinson, et al. "A Very Small Array search for the extended Sunyaev-Zel'dovich effect in the Corona Borealis supercluster." Monthly Notices of the Royal Astronomical Society 363, no. 1 (October 11, 2005): 79–92. http://dx.doi.org/10.1111/j.1365-2966.2005.09405.x.

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44

Beaujean, Pierre-Philippe J., Antoine Bon, and Edgar An. "Motion-Compensated Acoustic Positioning in Very Shallow Waters Using Spread-Spectrum Signaling and a Tetrahedral Ultrashort Baseline Array." Marine Technology Society Journal 44, no. 5 (September 1, 2010): 50–66. http://dx.doi.org/10.4031/mtsj.44.5.4.

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AbstractUltrashort baseline acoustic positioning systems (APSs) are well suited for unmanned underwater vehicle operations because of their small space requirement and ease of deployment. This type of positioning system estimates the relative phases between signals measured by an array of transducers, each a half wavelength from the others. The accuracy of these relative-phase estimates is limited by several factors. Reverberation may cause major signal distortion in the acoustic signals received by the array and limit the accuracy of time-delay estimation during position estimation. Another limiting factor is the ambient noise present in shallow and deep waters generated by waves, rain, boat traffic, and biological life. A motion-compensated ultrashort baseline APS operable in shallow water and port environment has been implemented at Florida Atlantic University. Multitones signal modulation and log-likelihood maximization enable this APS to operate in highly reverberant environments. The motion compensation system estimates the array position and orientation by merging inertial and differential GPS measurements using Kalman filtering techniques. Experiments show 0.67 and 2.67 degrees of error for the array tilt and heading estimates and 0.74 m for the array position estimate at a range of 23 m.

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González, José R., Ekaterina Zhecheva, Radostina Stoyanova, Diana Nihtianova, Pavel Markov, Régis Ravelle Chapuis, Ricardo Alcántara, Francisco Nacimiento, José L. Tirado, and Gregorio F. Ortiz. "A fractal-like electrode based on double-wall nanotubes of anatase exhibiting improved electrochemical behaviour in both lithium and sodium batteries." Physical Chemistry Chemical Physics 17, no. 6 (2015): 4687–95. http://dx.doi.org/10.1039/c4cp04572f.

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Zamłyński, Mariusz, and Piotr Słobodzian. "Influence of the Aperture Edge Diffraction Effects on the Mutual Coupling Compensation Technique in Small Planar Antenna Arrays." International Journal of Electronics and Telecommunications 57, no. 1 (March 1, 2011): 115–20. http://dx.doi.org/10.2478/v10177-011-0017-8.

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Influence of the Aperture Edge Diffraction Effects on the Mutual Coupling Compensation Technique in Small Planar Antenna Arrays In this paper the quality of a technique to compensate for mutual coupling (and other phenomena) in small linear antenna arrays is investigated. The technique consists in calculation of a coupling matrix, which is than used to determine corrected antenna array excitation coefficients. Although the technique is known for more than 20 years, there is still very little information about how different phenomena existing in a real antenna arrays influence its performance. In this paper two models of antenna arrays are used. In the first model the effect of mutual coupling is separated from the aperture edge diffraction. In the second model antenna both mutual coupling and aperture edge diffraction effects are included. It is shown that mutual coupling itself can be compensated very well and an ultralow sidelobe level (i.e. -50 dB) could be achieved in practice. In the presence of diffraction effects -46.3 dB sidelobe level has been attained, but radiation pattern can be controled only in narrow angle range (i.e. up to ±60°).

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47

González Álvarez, Itahisa N., Sebastian Rost, Andy Nowacki, and Neil D. Selby. "Small-scale lithospheric heterogeneity characterization using Bayesian inference and energy flux models." Geophysical Journal International 227, no. 3 (July 29, 2021): 1682–99. http://dx.doi.org/10.1093/gji/ggab291.

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SUMMARY Observations from different disciplines have shown that our planet is highly heterogeneous at multiple scale lengths. Still, many seismological Earth models tend not to include any small-scale heterogeneity or lateral velocity variations, which can affect measurements and predictions based on these homogeneous models. In this study, we describe the lithospheric small-scale isotropic heterogeneity structure in terms of the intrinsic, diffusion and scattering quality factors, as well as an autocorrelation function, associated with a characteristic scale length (a) and RMS fractional velocity fluctuations (ε). To obtain this characterization, we combined a single-layer and a multilayer energy flux models with a new Bayesian inference algorithm. Our synthetic tests show that this technique can successfully retrieve the input parameter values for 1- or 2-layer models and that our Bayesian algorithm can resolve whether the data can be fitted by a single set of parameters or a range of models is required instead, even for very complex posterior probability distributions. We applied this technique to three seismic arrays in Australia: Alice Springs array (ASAR), Warramunga Array (WRA) and Pilbara Seismic Array (PSAR). Our single-layer model results suggest intrinsic and diffusion attenuation are strongest for ASAR, while scattering and total attenuation are similarly strong for ASAR and WRA. All quality factors take higher values for PSAR than for the other two arrays, implying that the structure beneath this array is less attenuating and heterogeneous than for ASAR or WRA. The multilayer model results show the crust is more heterogeneous than the lithospheric mantle for all arrays. Crustal correlation lengths and RMS velocity fluctuations for these arrays range from ∼0.2 to 1.5 km and ∼2.3 to 3.9 per cent, respectively. Parameter values for the upper mantle are not unique, with combinations of low values of the parameters (a < 2 km and ε < ∼2.5 per cent) being as likely as those with high correlation length and velocity variations (a > 5 km and ε > ∼2.5 per cent, respectively). We attribute the similarities in the attenuation and heterogeneity structure beneath ASAR and WRA to their location on the proterozoic North Australian Craton, as opposed to PSAR, which lies on the archaean West Australian Craton. Differences in the small-scale structure beneath ASAR and WRA can be ascribed to the different tectonic histories of these two regions of the same craton. Overall, our results highlight the suitability of the combination of an energy flux model and a Bayesian inference algorithm for future scattering and small-scale heterogeneity studies, since our approach allows us to obtain and compare the different quality factors, while also giving us detailed information about the trade-offs and uncertainties in the determination of the scattering parameters.

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Kondo, Kazunobu, Yusuke Mizuno, Takanori Nishino, and Kazuya Takeda. "Practically Efficient Blind Speech Separation Using Frequency Band Selection Based on Magnitude Squared Coherence and a Small Dodecahedral Microphone Array." Journal of Electrical and Computer Engineering 2012 (2012): 1–11. http://dx.doi.org/10.1155/2012/324398.

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Small agglomerative microphone array systems have been proposed for use with speech communication and recognition systems. Blind source separation methods based on frequency domain independent component analysis have shown significant separation performance, and the microphone arrays are small enough to make them portable. However, the level of computational complexity involved is very high because the conventional signal collection and processing method uses 60 microphones. In this paper, we propose a band selection method based on magnitude squared coherence. Frequency bands are selected based on the spatial and geometric characteristics of the microphone array device which is strongly related to the dodecahedral shape, and the selected bands are nonuniformly spaced. The estimated reduction in the computational complexity is 90% with a 68% reduction in the number of frequency bands. Separation performance achieved during our experimental evaluation was 7.45 (dB) (signal-to-noise ratio) and 2.30 (dB) (cepstral distortion). These results show improvement in performance compared to the use of uniformly spaced frequency band.

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Rubiño-Martín, José Alberto, Antonio M. Aliaga, R. B. Barreiro, Richard A. Battye, Pedro Carreira, Kieran Cleary, Rod D. Davies, et al. "Non-Gaussianity in the Very Small Array cosmic microwave background maps with smooth goodness-of-fit tests." Monthly Notices of the Royal Astronomical Society 369, no. 2 (May 5, 2006): 909–20. http://dx.doi.org/10.1111/j.1365-2966.2006.10341.x.

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Migenes, V., J. A. Yates, R. J. Cohen, M. C. Shepherd, and P. F. Bowers. "High Resolution & High Sensitivity Spectral-Line Imaging with Multiple Arrays." Symposium - International Astronomical Union 158 (1994): 334–36. http://dx.doi.org/10.1017/s0074180900107843.

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At present there are several radio interferometer arrays ranging from the low-resolution (0.1–1″) high-sensitivity arrays such as the Very Large Array (VLA) to the high-resolution (0.0005–0.1″) low-sensitivity arrays such as MERLIN (though MERLIN, in the UK, is really in between this broad category), EVN, VLBA and SHEVE. Combining high sensitvity and high resolution is prohibitively expensive, because to have the u–v sampling of small arrays would require more and larger antenna elements. Hence high- resolution arrays have poor u–v coverage, decreasing the sensitivity of the instrument. This has a serious effect on spectral-line work, where sensitivity has already been sacrificed in the pursuit of spectral resolution.

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