WorldWideScience

Sample records for broadsides

  1. Noting the Tunes of Seventeenth-Century Broadside Ballads: The English Broadside Ballad Archive (EBBA

    Directory of Open Access Journals (Sweden)

    Patricia Fumerton

    2013-10-01

    Full Text Available This essay focuses on the ways a digital archive of printed, pre-1701 English broadside ballads facilitates and complicates the orality that folklorists have traditionally seen in opposition to print. The English Broadside Ballad Archive (EBBA recaptures the multi-media nature of early broadside ballads—as text, art, and song—providing recordings of all extant tunes for the printed ballads and, in doing so, capturing the ease and difficulties of matching text to tune.

  2. Continuous Beam Steering Through Broadside Using Asymmetrically Modulated Goubau Line Leaky-Wave Antennas.

    Science.gov (United States)

    Tang, Xiao-Lan; Zhang, Qingfeng; Hu, Sanming; Zhuang, Yaqiang; Kandwal, Abhishek; Zhang, Ge; Chen, Yifan

    2017-09-15

    Goubau line is a single-conductor transmission line, featuring easy integration and low-loss transmission properties. Here, we propose a periodic leaky-wave antenna (LWA) based on planar Goubau transmission line on a thin dielectric substrate. The leaky-wave radiations are generated by introducing periodic modulations along the Goubau line. In this way, the surface wave, which is slow-wave mode supported by the Goubau line, achieves an additional momentum and hence enters the fast-wave region for radiations. By employing the periodic modulations, the proposed Goubau line LWAs are able to continuously steer the main beam from backward to forward within the operational frequency range. However, the LWAs usually suffer from a low radiation efficiency at the broadside direction. To overcome this drawback, we explore both transversally and longitudinally asymmetrical modulations to the Goubau line. Theoretical analysis, numerical simulations and experimental results are given in comparison with the symmetrical LWAs. It is demonstrated that the asymmetrical modulations significantly improve the radiation efficiency of LWAs at the broadside. Furthermore, the measurement results agree well with the numerical ones, which experimentally validates the proposed LWA structures. These novel Goubau line LWAs, experimentally demonstrated and validated at microwave frequencies, show also great potential for millimeter-wave and terahertz systems.

  3. Optimal control of the vessel motion process at the broadside slip

    Directory of Open Access Journals (Sweden)

    Anton A. Omelchuk

    2015-12-01

    Full Text Available The main purpose during the mechanized launching or lifting of a vessel using broadside slip is the uniform velocity motion providing of the object (vessel with launching trolleys and the guaranteed prevention of emergencies. Aim: The aim of this work is the formulation and optimal control solution of a slip type vessel-lifting complex for providing the uniform velocity, coordinated, gradual relocation of the large vessels. Materials and Methods: The paper studies the matters of real-time control optimization of vessel-lifting complex during launching or lifting the vessel. Results: It is proposed to control the relocation of large object by funicular forces matching of the steel wire ropes of different motorized drives with account of current situation. The model in state space is obtained. This model describes the vessel relocation during the launching/lifting process. The optimal control solution of motorized multidrive system with goal functional is formulated. This solution allows minimizing the divergence of movement parameter values from given ones. It is substantiated the advisability of the use of adaptive control methods with observer to provide the corresponding reliability of vessel-lifting complex functioning.

  4. Broadside at the Pirates

    Science.gov (United States)

    Lowens, Irving

    1972-01-01

    Public Law 92-140 marks an important step forward in the history of copyright in the U.S., giving the copyright owner exclusive right to duplicate the sound recording in a tangible form that directly or indirectly captures the actual sounds fixed in the recording." (Author)

  5. Russia coordinates new broadside against OSCE / Liz Fuller

    Index Scriptorium Estoniae

    Fuller, Liz

    2004-01-01

    SRÜ maade poolt 8. juulil 2004 Viinis tehtud avaldusest, mille kohaselt sekkub Euroopa Julgeoleku- ja Koostööorganisatsioon (OSCE) riikide siseasjadesse ning rakendab topeltstandardeid. Avaldusega ei ühinenud Gruusia ja Aserbaidžaan

  6. Design of a rectenna system for GSM-900 band using novel broadside 2 × 1 array antenna

    Directory of Open Access Journals (Sweden)

    Manish Singh

    2017-05-01

    Full Text Available In this study, a rectenna operating at the GSM-900 frequency band has been fabricated and tested. This rectenna composed of a 2 × 1 T-shaped monopole array antenna and an energy processing circuit. In order to reduce the gap between adjacent antenna elements in the array structure, the proposed array antenna uses a ground stub. Compared with other array antennas, the proposed array antenna with the ground stub reduces the size up to 50% without affecting the gain and bandwidth. An antenna prototype is fabricated and experimentally tested. The measured antenna's gain and bandwidth are 3.2 and 152 MHz, respectively, hence showing its suitability for radio-frequency (RF energy harvesting application. For this to be feasible, the developed array antenna is matched with the rectifier at GSM-900 using a single stub matching network. The measured result demonstrates that the proposed rectifier circuit offers the conversion efficiency of 21.2 and 63.6% for an input power of −20 and 0 dBm, respectively. Finally, the rectifier performance is attested experimentally with the developed array antenna. The rectenna's measured RF-to-dc conversion efficiency was found to be 60% at the far-field distance from the transmitting antenna.

  7. Viajando sobre hojas volanderas: representaciones del viaje en pliegos sueltos del siglo XVIII = Travelling on broadsides: representations of travels in 18th-century Spanish chapbooks

    Directory of Open Access Journals (Sweden)

    Juan Gomis Coloma

    2016-12-01

    Full Text Available ResumenEl tema que aborda este trabajo son las representaciones del viaje y de los viajeros en los romances del siglo XVIII. Los objetivos son, en primer lugar, dar a conocer una fuente “popular” en relación a un tema, el viaje, que para el siglo XVIII ha sido generalmente estudiado desde la perspectiva de la alta cultura, como ingrediente clave para la formación e instrucción de cualquier espíritu ilustrado. Rastreando los aspectos asociados al viaje que, numerosos, asoman en los pliegos sueltos, se muestran otras representaciones de viajes y viajeros, que contribuyan a enriquecer nuestra comprensión sobre la diversidad de concepciones que el tema pudo suscitar en la época. En segundo lugar, a partir de una muestra representativa de romances publicados en el siglo XVIII, se analizan distintos rasgos de los relatos de viajes: periplos, lugares de destino, tipos de viajes, identidad de los viajeros, causas para emprender el itinerario, descripción de espacios, éxito o fracaso de la empresa, etc. Finalmente, se seleccionan algunos textos representativos para indagar los valores asociados al viaje y al encuentro con “el otro”, con el fin de explorar los miedos e ilusiones que, según los relatos, llevaba aparejado aventurarse hacia lo desconocido.AbstractThis paper focuses on 18th century romances’ representations of travels and travellers. Its aims are: firstly, to shed light on a «popular» source about a topic like travels, which has been studied traditionally from the perspective of high culture, as an element linked to the education of enlightened people. Through the analysis of different features about travels which are found in «pliegos sueltos», another representations of travels and travellers are shown, which can enrich our understanding about this topic. Secondly, different features of travelling stories published as popular prints in the 18th century are analysed: journeys, destinations, travellers and their aims, descriptions of places, success or failure of the trip, and so on. Finally, some representative texts have been selected in order to study values linked to travels and to the meeting with «the other». Thus, fears and dreams associated with travels in this stories are explored.

  8. Direct identification of early synthetic dyes: FT-Raman study of the illustrated broadside prints of José Gaudalupe Posada (1852-1913)

    Science.gov (United States)

    Casadio, F.; Mauck, K.; Chefitz, M.; Freeman, R.

    2010-09-01

    Fourier Transform (FT)-Raman spectroscopy was used for the non-invasive, direct identification of colorants used to dye historical printed papers, overcoming obstacles such as low concentration of the dye, faded colors and fluorescence interference of the aged paper substrate. Based on a newly created FT-Raman reference database of 20 widely used dyes in the 19th century paper industry, the detectability of these dyes on aged biomaterials was determined by studying dyed paper samples from contemporary dye manuals, and identifying diagnostic peaks detectable on those substrates. Lastly, the method was applied to analyze the colorants used to dye the papers of a group of prints illustrated by the influential Mexico City artist José Guadalupe Posada, active 1876-1913. Unambiguous identification of the synthetic organic colorants Malachite Green (a triarylmethane dye), Orange II and Metanil Yellow (two acid monoazo dyes), Cotton Scarlet (an acid diazo dye), Phloxine (a xanthene dye) and Victoria Blue (a triarylmethane dye) in several of Posada’s prints challenged previous art-historical assumptions that these artworks were colored with natural dyes. The acquired knowledge has important conservation implications given that aniline dyes are sensitive to light and to aqueous treatments otherwise commonly carried out on works of art on paper.

  9. Worst-case tolerance optimization of antenna systems

    DEFF Research Database (Denmark)

    Schjær-Jacobsen, Hans

    1980-01-01

    The application of recently developed algorithms to antenna systems design is demonstrated by the worst-case tolerance optimization of linear broadside arrays, using both spacings and excitation coefficients as design parameters. The resulting arrays are optimally immunized against deviations...

  10. Numerical study of rowing hydrofoil performance at low Reynolds numbers

    Science.gov (United States)

    Chung, M.-H.

    2008-04-01

    In this paper, the hydrodynamic performance of a 2-D flat-plate hydrofoil in rowing motion is numerically studied by a Cartesian grid method with the cut-cell approach. Adaptive mesh refinement is used to save on the number of mesh cells without harming spatial resolution in critical regions. The rowing kinematics of the hydrofoil is the same for all simulations in this work. The design parameters studied are the reduced frequency of the rowing motion, the heave amplitude, and the time lags of the feathered-to-broadside rotation and the broadside-to-feathered rotation. Results show that larger thrust and efficiency can be attained if the feathered-to-broadside rotation is started right after the beginning of the power stroke and the broadside-to-feathered rotation is finished right before the end of the power stroke. Finally, both the thrust and the efficiency increase with Reynolds number.

  11. Metamaterial-inspired SRR-based Small Antenna

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.; Breinbjerg, Olav

    2009-01-01

    A self-resonant miniaturized antenna composed of a broadside-coupled split ring resonator (SRR) and an excitation truncated loop is presented. Being λ0/17 in size the antenna is tuned to 50 Ohms without any matching network.......A self-resonant miniaturized antenna composed of a broadside-coupled split ring resonator (SRR) and an excitation truncated loop is presented. Being λ0/17 in size the antenna is tuned to 50 Ohms without any matching network....

  12. An Improved Electro-Optical Image Quality Summary Measure.

    Science.gov (United States)

    1981-10-01

    photo- graphing the display of a vidicon camera system viewing silhouettes of the broadside view of a Soviet KOTLIN class destroyer. Observers were...series ,: hard mages. Transparencies of the broadside KOTLIN silhouette were made with the scale :actor ranqin,, from 13b to 1810 meters per picture...3 warship rather than a merchant ship, and (c) the warsh-,;, is identifiable as beinq )f the nDTLIN class. Obviously, since only KOTLIN images were

  13. Internetová databáze kramářských tisků Etnologického ústavu Akademie věd České republiky, v. v. i. v Praze

    Czech Academy of Sciences Publication Activity Database

    Holubová, Markéta

    2017-01-01

    Roč. 5, č. 1 (2017), s. 147-158 ISSN 1339-2204 Grant - others:AV ČR(CZ) StrategieAV21/12 Program:StrategieAV Institutional support: RVO:68378076 Keywords : popular culture * Czechia * chapbooks * broadsides ballads * electronic databases * format MARC 21 Subject RIV: AC - Archeology, Anthropology, Ethnology OBOR OECD: Antropology, ethnology

  14. Glenn Ligon: Re-Visioning Change

    Science.gov (United States)

    Rhoades, Mindi; Sanders, Jim

    2007-01-01

    Glenn Ligon is a multifaceted artist working across multiple media, including painting, sculpture, printmaking, photography, video, and digital media. He is a conceptual artist, often working to include text with visuals and as visuals in his work. He appropriates text from classic authors, like Homer, from runaway slave broadsides, from Richard…

  15. Investigation of TV Signal Strength at Kwaluseni Campus ...

    African Journals Online (AJOL)

    A field strength meter (an instrument for measuring the strength of television (TV) signals) was designed, built and tested. It was then used in conjuction with a broadside array ultra-high frequency (UHF) antenna to measure the Swazi TV signal strength at different points around the Kwaluseni Campus of the University of ...

  16. Estimates of Crustal Transmission Losses Using MLM Array Processing.

    Science.gov (United States)

    1982-07-01

    about the z axis, (broadside case) 31 b 2 uniform1 a liud an linea 5i8 l an -2.0, e7., Th patresrttoal symti abu hezai 31 c 10 log B 2 ,dB e5-82 0 e... algebraic , expression for the estimated covariance matrix term (i,j) is: wnere M is the number of frequency components and 4 (i,j) is the phase shift

  17. Low-profile antennas based on aperiodic and compact meta-surfaces

    OpenAIRE

    Mateos Navarro, Rosa Maria

    2009-01-01

    Artificial magnetic ground planes enable the placement of horizontal antennas close to the ground plane. However, their behaviour as AMCs (Artificial Magnetic Conductor) is valid only over a small frequency band. Hence, their use in wideband antenna applications remains a challenge. The antenna-AMC combination can be optimized to maximize the impedance bandwidth, thanks to the coupling between the antenna and the AMC. However, we have observed that the radiation patterns split at broadside...

  18. HYBRID SILICON-ON-SAPPHIRE/SCALED CMOS INTERFERENCE MITIGATION FRONT END BASED ON SIMULTANEOUS NOISE CANCELLATION, ACTIVE-INTERFERENCE CANCELLATION AND N-PATH-MIXER FILTERING

    Science.gov (United States)

    2017-04-01

    orthogonal frequency-division multiplexing (OFDM)-like modulated TX signal. Conventional reciprocal ANT interfaces, such as surface acoustic wave (SAW...RF interconnections at board-level. A wireless imaging demo shows two of the implemented ICs tiled on board to form an eight-element MIMO receiver...Measured spatial responses show >30dB of spatial notch suppression in the broadside direction. Two ICs can be tiled on printed circuit board (PCB) to

  19. Maximum Constrained Directivity of Oversteered End-Fire Sensor Arrays

    Directory of Open Access Journals (Sweden)

    Andrea Trucco

    2015-06-01

    Full Text Available For linear arrays with fixed steering and an inter-element spacing smaller than one half of the wavelength, end-fire steering of a data-independent beamformer offers better directivity than broadside steering. The introduction of a lower bound on the white noise gain ensures the necessary robustness against random array errors and sensor mismatches. However, the optimum broadside performance can be obtained using a simple processing architecture, whereas the optimum end-fire performance requires a more complicated system (because complex weight coefficients are needed. In this paper, we reconsider the oversteering technique as a possible way to simplify the processing architecture of equally spaced end-fire arrays. We propose a method for computing the amount of oversteering and the related real-valued weight vector that allows the constrained directivity to be maximized for a given inter-element spacing. Moreover, we verify that the maximized oversteering performance is very close to the optimum end-fire performance. We conclude that optimized oversteering is a viable method for designing end-fire arrays that have better constrained directivity than broadside arrays but with a similar implementation complexity. A numerical simulation is used to perform a statistical analysis, which confirms that the maximized oversteering performance is robust against sensor mismatches.

  20. Miniaturised self-resonant split-ring resonator antenna

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.; Breinbjerg, Olav

    2009-01-01

    A self-resonant miniaturized antenna composed of a broadside-coupled split-ring resonator (SRR) and an excitation arc-shaped monopole is presented. The size of the antenna and its resonance frequency is essentially defined by the SRR dimensions and geometry, while the input resistance...... at the resonance is governed by the arc length of the monopole. Numerical and experimental results are presented for an antenna configuration of 1/23.4 wavelength in diameter (ka~0.134). The antenna is tuned to 50 ohms without any matching network, and its efficiency is measured to be 17.5%....

  1. Smart antennas based on graphene

    Energy Technology Data Exchange (ETDEWEB)

    Aldrigo, Martino; Dragoman, Mircea, E-mail: mircea.dragoman@imt.ro [National Institute for Research and Development in Microtechnology (IMT), P.O. Box 38-160, 023573 Bucharest (Romania); Dragoman, Daniela [Physics Faculty, University of Bucharest, P.O. Box MG-11, 077125 Bucharest (Romania)

    2014-09-21

    We report two configurations of smart graphene antennas, in which either the radiation pattern of the antenna or the backscattering of the periodic metallic arrays is controlled by DC biases that induce metal-insulator reversible transitions of graphene monolayers. Such a transition from a high surface resistance (no bias) to a low surface resistance state (finite bias voltage) causes the radiation pattern of metallic antennas backed with graphene to change dramatically, from omnidirectional to broadside. Moreover, reflectarrays enhance the backscattered field due to the same metal-dielectric transition.

  2. Silicon-Based Technology for Integrated Waveguides and mm-Wave Systems

    DEFF Research Database (Denmark)

    Jovanovic, Vladimir; Gentile, Gennaro; Dekker, Ronald

    2015-01-01

    IC processing is used to develop technology for silicon-filled millimeter-wave-integrated waveguides. The front-end process defines critical waveguide sections and enables integration of dedicated components, such as RF capacitors and resistors. Wafer gluing is used to strengthen the mechanical...... insertion loss is only 0.12 dB/mm at 105 GHz. The optimized planar transition, the components of a beam-forming network, and a slotted waveguide antenna array are fabricated as further technology demonstrators. The broadside radiation of the antenna array has a beam steering of 63° using a frequency...

  3. Disputatio and Dedication. Seventeenth-century thesis prints in the southern Low Countries

    Directory of Open Access Journals (Sweden)

    Gwendoline de Mûelenaere

    2015-12-01

    Full Text Available This article analyzes the tradition of thesis prints in universities and Jesuit colleges of the Spanish Low Countries. It focuses on the origins and the iconography of these engraved broadsides in order to highlight their intellectual, artistic and socio-political dimensions. Being a direct source about teaching in Louvain and Douai, this visual material can provide insight into the learning practices in the Southern Netherlands, in particular the tradition of public defences and the significance of courtly patronage and dedications in an academic environment. The investigated examples are part of the aesthetics developed in Antwerp in the first half of the seventeenth century.

  4. Application of the marine Ex-Bz transient system for delineating near shore resistive targets

    Science.gov (United States)

    Levi, Eldad; Goldman, Mark

    2017-09-01

    Under certain conditions, multidimensional coastal effect significantly enhances relative target response of the broadside transient marine Ex-Bz system. The effect is caused by a redistribution of the induced currents between the resistive target and the sea bottom compared to that existing in a 1-D geometry. As a result, the effect strongly depends on specific geoelectric conditions in the near-shore environment. The first study of the effect in the Mediterranean coast of central Israel was addressing shallow groundwater problem under specific geoelectric, hydrogeological and geomorphological conditions. Under different conditions (e.g. deep targets and sharp near-shore bathymetry), the influence of the effect on target response might be significantly different. More general analysis carried out in this study comprises various geoelectric scenarios that include both shallow and deep resistive targets at different distances from the shore line as well as various geometries of the target and the near-shore bathymetry. The study includes three major exploration aspects of the system, namely signal detectability, lateral and vertical resolution. Taking into account poor lateral resolution of the classical frequency domain CSEM and the limited application in shallow sea, the described broadside transient Ex-Bz system might represent a desired alternative for delineating shallow and deep resistive targets in transition zone.

  5. Chapter 3 – Phenomenology of Tsunamis: Statistical Properties from Generation to Runup

    Science.gov (United States)

    Geist, Eric L.

    2015-01-01

    Observations related to tsunami generation, propagation, and runup are reviewed and described in a phenomenological framework. In the three coastal regimes considered (near-field broadside, near-field oblique, and far field), the observed maximum wave amplitude is associated with different parts of the tsunami wavefield. The maximum amplitude in the near-field broadside regime is most often associated with the direct arrival from the source, whereas in the near-field oblique regime, the maximum amplitude is most often associated with the propagation of edge waves. In the far field, the maximum amplitude is most often caused by the interaction of the tsunami coda that develops during basin-wide propagation and the nearshore response, including the excitation of edge waves, shelf modes, and resonance. Statistical distributions that describe tsunami observations are also reviewed, both in terms of spatial distributions, such as coseismic slip on the fault plane and near-field runup, and temporal distributions, such as wave amplitudes in the far field. In each case, fundamental theories of tsunami physics are heuristically used to explain the observations.

  6. GPR Imaging of Prehistoric Animal Bone-beds

    Science.gov (United States)

    Schneider, Blair Benson

    effects of GPR antenna orientation relative to the survey line (broad-side mode versus end-fire mode) and polarization effects of the buried bone targets were investigated. The results reveal that animal bone does exhibit polarization effects. However, the polarization results are greatly affected by the irregular shape and size of the bone, which ultimately limits the potential usefulness of trying to utilize polarization data to determine the orientation of buried bone targets. In regard to antenna orientation, end-fire mode was found to have little difference in amplitude response as compared to the more commonly used broad-side mode and in fact sometimes outperformed the broad-side mode. Future GPR investigations should consider utilizing multiple antenna orientations during data collection.

  7. Micromachined On-Chip Dielectric Resonator Antenna Operating at 60 GHz

    KAUST Repository

    Sallam, Mai

    2015-06-01

    This paper presents a novel cylindrical Dielectric Resonator Antenna (DRA) suitable for millimeter-wave on-chip systems. The antenna was fabricated from a single high resistivity silicon wafer via micromachining technology. The new antenna was characterized using HFSS and experimentally with good agreement been found between the simulations and experiment. The proposed DRA has good radiation characteristics, where its gain and radiation efficiency are 7 dBi and 79.35%, respectively. These properties are reasonably constant over the working frequency bandwidth of the antenna. The return loss bandwidth was 2.23 GHz, which corresponds to 3.78% around 60 GHz. The antenna was primarily a broadside radiator with -15 dB cross polarization level.

  8. Miniaturized Planar Split-Ring Resonator Antenna

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.; Breinbjerg, Olav

    2009-01-01

    A miniaturized planar antenna based on a broadside-coupled split ring resonator excited by an arc-shaped dipole is presented. The excitation dipole acts as a small tuning capacitor in series with a parallel RLC circuit represented by the SRR. The antenna resonance frequency and dimensions...... a essentially determined by the SRR, while by varying the dipole arm length the input resistance is changed in a wide range, thus matching the antenna to a feed line and compensating for simulation and manufacturing inaccuracies. No additional matching network is required. Theoretically, there is no limit...... on how small this antenna can be. In practice, the lower bound is set by losses in utilized materials and manufacturing inaccuracies. As an example, an antenna of ka=0.09 was designed, fabricated and tested. Although the initially fabricated antenna prototype had the input impedance of 43 ohms...

  9. Single- and double-sided sensor applications of metamaterials based on square-ring and diamond resonators for terahertz region

    Science.gov (United States)

    Shawky, Najlaa; Adnan Taha, Salah Al-Deen; Altan, Hakan; Sabah, Cumali

    2017-03-01

    This study investigates the sensing applications of metamaterial (MTM) structures in the terahertz (THz) region and is based on a broadside-coupled diamond and square-ring resonator (DSRR) structures. The resonators are designed and simulated as sensors in detail. Compared with single-sided sensors, the sensing capability of double-sided sensors provide an enhancement with respect to the sensitivity. To analyze the structure as sensor, the changes in the transmission resonance are investigated as a function of the permittivity and thickness of overlayer for the single- and double-sided MTM. The results demonstrate that this design can provide good sensitivity when sensing the chemical or biological agents that are resonant in the terahertz region of the electromagnetic spectrum. These types of designs can be employed in the many sensing applications that are of interest in the THz region.

  10. Laterally Placed CDRA with Triangular Notches for Ultra Wideband Applications

    Science.gov (United States)

    Sankaranarayanan, Dileep; Venkata Kiran, Duggirala; Mukherjee, Biswajeet

    2017-12-01

    In this paper, a Coaxial probe-fed Laterally placed Cylindrical Dielectric Resonator Antenna (LCDRA) with symmetrical triangular notches is presented. The lateral surface of the Cylindrical Dielectric Resonator Antenna (CDRA) is kept on the ground plane with its longitudinal axis parallel to the ground plane. LCDRA has a lower resonant frequency than the CDRA and it offers considerably wider impedance bandwidth than CDRA. Finally, two symmetrical triangular notches are introduced on the two edges of LCDRA which is perpendicular to the axis to further improve the impedance bandwidth. The proposed antenna offers a wide impedance bandwidth (S_{11} <-10 dB) of 76.7 % (4.5-10.1 GHz). The radiation pattern of the proposed antenna is stable and broadside throughout the impedance bandwidth of operation. The prototype of the proposed antenna is fabricated and measured results are found to be in good agreement with the simulated one.

  11. Low profile conformal antenna arrays on high impedance substrate

    CERN Document Server

    Singh, Hema; Jha, Rakesh Mohan

    2016-01-01

    This book presents electromagnetic (EM) design and analysis of dipole antenna array over high impedance substrate (HIS). HIS is a preferred substrate for low-profile antenna design, owing to its unique boundary conditions. Such substrates permit radiating elements to be printed on them without any disturbance in the radiation characteristics. Moreover HIS provides improved impedance matching, enhanced bandwidth, and increased broadside directivity owing to total reflection from the reactive surface and high input impedance. This book considers different configurations of HIS for array design on planar and non-planar high-impedance surfaces. Results are presented for cylindrical dipole, printed dipole, and folded dipole over single- and double-layered square-patch-based HIS and dogbone-based HIS. The performance of antenna arrays is analyzed in terms of performance parameters such as return loss and radiation pattern. The design presented shows acceptable return loss and mainlobe gain of radiation pattern. Thi...

  12. Spectral analysis of bistatic scattering from underwater elastic cylinders and spheres.

    Science.gov (United States)

    Gunderson, Aaron M; España, Aubrey L; Marston, Philip L

    2017-07-01

    Far field sound scattering from underwater elastic spheres and finite cylinders is considered over the full range of scattering angles. Three models for the frequency response of the scattered field are evaluated: a hybrid finite element/propagation simulation for a finite cylinder with broadside illumination, an approximate solution for the finite cylinder, and the exact solution for a sphere. The cylinder models are shown to give comparable results, attesting to the strength of the finite cylinder approximate solution. Interference and resonance structure present in the frequency response of the targets is identified and discussed, and the bistatic spectra for a variety of elastic sphere materials are presented. A thorough understanding of the complicated angle and frequency dependence of the scattering from simple elastic targets is helpful for interpretation of backscattering data from targets at or near an interface, or for scattering data taken by moving automated underwater vehicles, acoustic arrays, or other forms of data collection involving bistatic scattering.

  13. A Novel Wideband Magneto-Electric Dipole Antenna with Improved Feeding Structure

    Directory of Open Access Journals (Sweden)

    N. Marwah

    2016-08-01

    Full Text Available A novel feeding structure in magneto-electric dipole antenna is proposed and analyzed, which is simpler and better in performance than previous designs, involving differential feeding.  Due to this improved feeding structure, the antenna has achieved an impedance bandwidth of 133.3% ( 0.5 GHz – 2.5 GHz, resulting into an ultra-wide band antenna. The maximum broadside gain 7.5dBi with unidirectional radiation pattern has also been reported for the entire the range of operation. Symmetry in E-plane and H-plane radiation patterns has been observed due to the symmetry in structure and excitation of antenna. The antenna has also been able to achieve cross polarization levels.

  14. “A most detestable crime”. Representations of Rape in the Popular Press of Early Modern England

    Directory of Open Access Journals (Sweden)

    Donatella Pallotti

    2013-03-01

    Full Text Available In early modern England the legal definition of rape underwent an important revision and gradually, from crime against property, rape became a crime against the person. While reflecting the classical, medieval and biblical assumptions, the period brought about new concerns. The purpose of this article is to explore representations of rape in a variety of popular texts of the English early modern period, by focussing attention on broadside ballads, cheap pamphlets as well as accounts of trials that took place at the Old Bailey. These texts constitute valuable sources of information about people’s attitudes and beliefs and help us construct the views of rape circulating in early modern English culture.

  15. Isotropic Single Negative Metamaterials

    Directory of Open Access Journals (Sweden)

    P. Protiva

    2008-09-01

    Full Text Available This paper presents the application of simple, and therefore cheap, planar resonators for building 3D isotropic metamaterials. These resonators are: a broadside-coupled split ring resonator with a magnetic response providing negative permeability; an electric dipole terminated by a loop inductor together with a double H-shaped resonator with an electric response providing negative permittivity. Two kinds of 3D isotropic single negative metamaterials are reported. The first material consists of unit cells in the form of a cube bearing on its faces six equal planar resonators with tetrahedral symmetry. In the second material, the planar resonators boxed into spherical plastic shells and randomly distributed in a hosting material compose a real 3D volumetric metamaterial with an isotropic response. In both cases the metamaterial shows negative permittivity or permeability, according to the type of resonators that are used. The experiments prove the isotropic behavior of the cells and of the metamaterial specimens.

  16. Initial assessment of a waveguide with dielectric-filled corrugations as a technology for slot antennas with backward-to-forward scanning capabilities

    Science.gov (United States)

    Navarro-Tapia, M.; Esteban, J.; Camacho-Peñalosa, C.

    2009-11-01

    The frequency-scanning capabilities of continuous-type leaky-wave antennas have usually been restricted to main-beam pointing angles within the forward quadrant. With the appearance of metamaterial concepts, wave propagation with negative and zero phase constant has made it possible to spread the scanning directions, allowing main-beam angles into the backward quadrant, as well as the broadside direction. In this paper, a straight long slot antenna, implemented in a rectangular waveguide with dielectric-filled corrugations, is analyzed, constructed and measured, and an analysis method, based on an equivalent homogeneized waveguide, is proposed. Some features of the antenna, such as losses, radiation pattern and gain are studied, in order to assess the performance and suitability of the composite right/left-handed waveguide technology used. The obtained results highlight the limiting factors for the applicability of the corrugated waveguide in antenna applications, while confirm the validity of the analysis technique proposed.

  17. Thermal engineering research. [Runge-Kutta investigation of gas flow inside multilayer insulation system for rocket booster fuel tanks

    Science.gov (United States)

    Shih, C. C.

    1973-01-01

    A theoretical investigation of gas flow inside a multilayer insulation system has been made for the case of the broadside pumping process. A set of simultaneous first-order differential equations for the temperature and pressure of the gas mixture was obtained by considering the diffusion mechanism of the gas molecules through the perforations on the insulation layers. A modified Runge-Kutta method was used for numerical experiment. The numerical stability problem was investigated. It has been shown that when the relaxation time is small compared with the time period over which the gas properties change appreciably, the set of differential equations can be replaced by a set of algebraic equations for solution. Numerical examples were given, and comparisons with experimental data were made.

  18. Corporate array of micromachined dipoles on silicon wafer for 60 GHz communication systems

    KAUST Repository

    Sallam, M. O.

    2013-03-01

    In this paper, an antenna array operating at 60 GHz and realized on 0.675 mm thick silicon substrate is presented. The array is constructed using four micromachined half-wavelength dipoles fed by a corporate feeding network. Isolation between the antenna array and its feeding network is achieved via a ground plane. This arrangement leads to maximizing the broadside radiation with relatively high front-to-back ratio. Simulations have been carried out using both HFSS and CST, which showed very good agreement. Results reveal that the proposed antenna array has good radiation characteristics, where the directivity, gain, and radiation efficiency are around 10.5 dBi, 9.5 dBi, and 79%, respectively. © 2013 IEEE.

  19. Dual-Band Operation of a Circularly Polarized Four-Arm Curl Antenna with Asymmetric Arm Length

    Directory of Open Access Journals (Sweden)

    Son Xuat Ta

    2016-01-01

    Full Text Available This paper presents dual-band operation of a single-feed composite cavity-backed four-arm curl antenna. Dual-band operation is achieved with the presence of the asymmetrical arm structure. A pair of vacant-quarter printed rings is used in the feed structure to produce a good circular polarization (CP at both bands. The cavity-backed reflector is employed to improve the CP radiation characteristics in terms of the 3-dB axial ratio beamwidth and broadside gain. The proposed antenna is widely applicable in dual-band communication systems that have a small frequency ratio. Examples of such a system are global positioning systems.

  20. Analysis and design of a composite left-/right-handed leaky wave antenna based on the H10 rectangular waveguide mode

    Directory of Open Access Journals (Sweden)

    T. F. Eibert

    2008-05-01

    Full Text Available The presented "open" composite left-handed/right-handed (CRHLH substrate integrated waveguide performs well as a low-profile leaky wave antenna. This design is distinguished due to the fact that it is derived from the approved equivalent circuit model of the H10 rectangular hollow waveguide mode. The wave propagation behaviour is visualised by the dispersion diagram calculated by two different methods, infinite periodic full-wave simulation and Matrix-Pencil analysis of driven field solutions. The periodic configuration is also analysed in terms of the Bloch impedance. Although FR-4 serves as substrate the antenna features an efficiency of about 50% to 60%. The radiation performance demonstrates nearly backfire to almost endfire scanning capability of the antenna by mere frequency variation. Broadside radiation is possible due to the balanced state at 4 GHz.

  1. 16th century European earthquakes described in some contemporary woodcuts

    Science.gov (United States)

    Deresiewicz, H.

    1985-01-01

    In the middle of the 15th century, shortly after Gutenberg’s invention of printing using individual lead type, the first illustrated broadsides (or broadsheets) began appearing in southern Germany.  Usually printed on one side of a sheet of paper, they consisted of a woodcut illustration, sometimes colored, either by hand or by stencil, and several columns of text, often in verse.  The appeal of the publications to the mass reader was often stimulated by sensationalism in word and picture, somewhat like that purveyed today’s tabloid press.  What follows are woodcuts and portions of the text from 16th to 17th century broadsheets that describe earthquakes and volcanic eruptions.

  2. A Novel Compact Wideband TSA Array for Near-Surface Ice Sheet Penetrating Radar Applications

    Science.gov (United States)

    Zhang, Feng; Liu, Xiaojun; Fang, Guangyou

    2014-03-01

    A novel compact tapered slot antenna (TSA) array for near-surface ice sheet penetrating radar applications is presented. This TSA array is composed of eight compact antenna elements which are etched on two 480mm × 283mm FR4 substrates. Each antenna element is fed by a wideband coplanar waveguide (CPW) to coupled strip-line (CPS) balun. The two antenna substrates are connected together with a metallic baffle. To obtain wideband properties, another two metallic baffles are used along broadsides of the array. This array is fed by a 1 × 8 wideband power divider. The measured S11 of the array is less than -10dB in the band of 500MHz-2GHz, and the measured gain is more than 6dBi in the whole band which agrees well with the simulated results.

  3. Genetic Algorithm Optimization of a High-Directivity Microstrip Patch Antenna Having a Rectangular Profile

    Directory of Open Access Journals (Sweden)

    J.W. Jayasinghe

    2013-09-01

    Full Text Available A single high-directivity microstrip patch antenna (MPA having a rectangular profile, which can substitute a linear array is proposed. It is designed by using genetic algorithms with the advantage of not requiring a feeding network. The patch fits inside an area of 2.54lambda x 0.25lambda, resulting in a broadside pattern with a directivity of 12 dBi and a fractional impedance bandwidth of 4%. The antenna is fabricated and the measurements are in good agreement with the simulated results. The genetic MPA provides a similar directivity as linear arrays using a corporate or series feeding, with the advantage that the genetic MPA results in more bandwidth.

  4. High efficiency on-chip Dielectric Resonator Antennna using micromachining technology

    KAUST Repository

    Sallam, Mai O.

    2015-10-26

    In this paper, a novel cylindrical Dielectric Resonator Antenna (DRA) operating at 60 GHz is introduced. The antenna is fabricated using a high-resistivity silicon wafer. The DR is defined in the wafer using micromachining technology. The feeding network is located at the other side of the wafer. The proposed antenna is simulated using HFSS and the results are verified by measurements. The antenna radiation is mainly along the broadside direction. The measured gain, radiation efficiency, and bandwidth are 7 dBi, 74.65%, and 2.23 GHz respectively. The antenna is characterized by high polarization purity where the maximum cross-polarization is -15 dB. © 2015 IEEE.

  5. Target Strength of Southern Resident Killer Whales (Orcinus orca): Measurement and Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Jinshan; Deng, Zhiqun; Carlson, Thomas J.; Moore, Brian

    2012-04-04

    A major criterion for tidal power licensing in Washington’s Puget Sound is the management of the risk of injury to killer whales due to collision with moving turbine blades. An active monitoring system is being proposed for killer whale detection, tracking, and alerting that links to and triggers temporary turbine shutdown when there is risk of collision. Target strength (TS) modeling of the killer whale is critical to the design and application of any active monitoring system. A 1996 study performed a high-resolution measurement of acoustic reflectivity as a function of frequency of a female bottlenose dolphin (2.2 m length) at broadside aspect and TS as a function of incident angle at 67 kHz frequency. Assuming that killer whales share similar morphology structure with the bottlenose dolphin, we extrapolated the TS of an adult killer whale 7.5 m in length at 67 kHz frequency with -8 dB at broadside aspect and -28 dB at tail side. The backscattering data from three Southern Resident killer whales were analyzed to obtain the TS measurement. These data were collected at Lime Kiln State Park using a split-beam system deployed from a boat. The TS of the killer whale at higher frequency (200 kHz) was estimated based on a three-layer model for plane wave reflection from the lung of the whale. The TS data of killer whales were in good agreement with our model. In this paper, we also discuss and explain possible causes for measurement estimation error.

  6. Understanding and optimizing microstrip patch antenna cross polarization radiation on element level for demanding phased array antennas in weather radar applications

    Science.gov (United States)

    Vollbracht, D.

    2015-11-01

    The antenna cross polarization suppression (CPS) is of significant importance for the accurate calculation of polarimetric weather radar moments. State-of-the-art reflector antennas fulfill these requirements, but phased array antennas are changing their CPS during the main beam shift, off-broadside direction. Since the cross polarization (x-pol) of the array pattern is affected by the x-pol element factor, the single antenna element should be designed for maximum CPS, not only at broadside, but also for the complete angular electronic scan (e-scan) range of the phased array antenna main beam positions. Different methods for reducing the x-pol radiation from microstrip patch antenna elements, available from literature sources, are discussed and summarized. The potential x-pol sources from probe fed microstrip patch antennas are investigated. Due to the lack of literature references, circular and square shaped X-Band radiators are compared in their x-pol performance and the microstrip patch antenna size variation was analyzed for improved x-pol pattern. Furthermore, the most promising technique for the reduction of x-pol radiation, namely "differential feeding with two RF signals 180° out of phase", is compared to single fed patch antennas and thoroughly investigated for phased array applications with simulation results from CST MICROWAVE STUDIO (CST MWS). A new explanation for the excellent port isolation of dual linear polarized and differential fed patch antennas is given graphically. The antenna radiation pattern from single fed and differential fed microstrip patch antennas are analyzed and the shapes of the x-pol patterns are discussed with the well-known cavity model. Moreover, two new visual based electromagnetic approaches for the explanation of the x-pol generation will be given: the field line approach and the surface current distribution approach provide new insight in understanding the generation of x-pol component in microstrip patch antenna radiation

  7. Space-Variant Post-Filtering for Wavefront Curvature Correction in Polar-Formatted Spotlight-Mode SAR Imagery

    Energy Technology Data Exchange (ETDEWEB)

    DOREN,NEALL E.

    1999-10-01

    Wavefront curvature defocus effects occur in spotlight-mode SAR imagery when reconstructed via the well-known polar-formatting algorithm (PFA) under certain imaging scenarios. These include imaging at close range, using a very low radar center frequency, utilizing high resolution, and/or imaging very large scenes. Wavefront curvature effects arise from the unrealistic assumption of strictly planar wavefronts illuminating the imaged scene. This dissertation presents a method for the correction of wavefront curvature defocus effects under these scenarios, concentrating on the generalized: squint-mode imaging scenario and its computational aspects. This correction is accomplished through an efficient one-dimensional, image domain filter applied as a post-processing step to PF.4. This post-filter, referred to as SVPF, is precalculated from a theoretical derivation of the wavefront curvature effect and varies as a function of scene location. Prior to SVPF, severe restrictions were placed on the imaged scene size in order to avoid defocus effects under these scenarios when using PFA. The SVPF algorithm eliminates the need for scene size restrictions when wavefront curvature effects are present, correcting for wavefront curvature in broadside as well as squinted collection modes while imposing little additional computational penalty for squinted images. This dissertation covers the theoretical development, implementation and analysis of the generalized, squint-mode SVPF algorithm (of which broadside-mode is a special case) and provides examples of its capabilities and limitations as well as offering guidelines for maximizing its computational efficiency. Tradeoffs between the PFA/SVPF combination and other spotlight-mode SAR image formation techniques are discussed with regard to computational burden, image quality, and imaging geometry constraints. It is demonstrated that other methods fail to exhibit a clear computational advantage over polar-formatting in conjunction

  8. Boundary effects on the drag of a cylinder in axial motion at low Reynolds number

    Energy Technology Data Exchange (ETDEWEB)

    Wehbeh, E.G.

    1987-01-01

    This work is an experimental study of the Stokes drag on a right circular cylinder moving with constant velocity through a Newtonian viscous fluid. The cylinder velocity is parallel to its longitudinal axis, and the fluid is bounded on the outside by a fixed coaxial cylindrical tube of circular cross section. The length-to-diameter ratio of the moving cylinder ranges from 1.0 to 390, the ratio of the width of the annular gap to the cylinder length ranges from 0.0077 to 0.86, and the ratio ..cap alpha.. of the cylinder diameter to the tube diameter ranges from 0.022 to 0.91. Experimental values of the drag are compared with a theoretical expression which assumes a flow entirely axial in the annular region and a drag that is due entirely to the viscous stress on the cylinder side plus the effect of the dynamic pressure difference on the ends of the cylinder. A second problem is considered in which a thin circular disk moves broadside through a viscous fluid toward a plane wall that is parallel to the disk. An expression obtained for the Stokes drag agrees with the experiment and reduces to known theoretical results at extremes of large and small distances form the disk to the plane.

  9. Directionality and maneuvering effects on a surface ship underwater acoustic signature.

    Science.gov (United States)

    Trevorrow, Mark V; Vasiliev, Boris; Vagle, Svein

    2008-08-01

    This work examines underwater source spectra of a small (560 tons, 40 m length), single-screw oceanographic vessel, focusing on directionality and effects of maneuvers. The measurements utilized a set of four, self-contained buoys with GPS positioning, each recording two calibrated hydrophones with effective acoustic bandwidth from 150 Hz to 5 kHz. In straight, constant-speed runs at speeds up to 6.2 m s(-1), the ship source spectra showed spectral levels in reasonable agreement with reference spectra. The broadband source level was observed to increase as approximately speed to the fourth power over the range of 2.6-6.1 m s(-1), partially biased at low speeds by nonpropulsion machinery signals. Source directionality patterns were extracted from variations in source spectra while the ship transited past the buoy field. The observed spectral source levels exhibited a broadside maximum, with bow and stern aspect reduced by approximately 12-9 dB, respectively, independent of frequency. An empirical model is proposed assuming that spectral source levels exhibit simultaneous variations in aspect angle, speed, and turn rate. After correction for source directionality and speed during turning maneuvers, an excess of up to 18 dB in one-third octave source levels was observed.

  10. A Novel Manufacturing Process for Compact, Low-Weight and Flexible Ultra-Wideband Cavity Backed Textile Antennas.

    Science.gov (United States)

    Van Baelen, Dries; Lemey, Sam; Verhaevert, Jo; Rogier, Hendrik

    2018-01-03

    A novel manufacturing procedure for the fabrication of ultra-wideband cavity-backed substrate integrated waveguide antennas on textile substrates is proposed. The antenna cavity is constructed using a single laser-cut electrotextile patch, which is folded around the substrate. Electrotextile slabs protruding from the laser-cut patch are then vertically folded and glued to form the antenna cavity instead of rigid metal tubelets to implement the vertical cavity walls. This approach drastically improves mechanical flexibility, decreases the antenna weight to slightly more than 1 g and significantly reduces alignment errors. As a proof of concept, a cavity-backed substrate integrated waveguide antenna is designed and realized for ultra-wideband operation in the [5.15-5.85] GHz band. Antenna performance is validated in free space as well as in two on body measurement scenarios. Furthermore, the antenna's figures of merit are characterized when the prototype is bent at different curvature radii, as commonly encountered during deployment on the human body. Also the effect of humidity content on antenna performance is studied. In all scenarios, the realized antenna covers the entire operating frequency band, meanwhile retaining a stable radiation pattern with a broadside gain above 5 dBi, and a radiation efficiency of at least 70%.

  11. A Multiband Proximity-Coupled-Fed Flexible Microstrip Antenna for Wireless Systems

    Directory of Open Access Journals (Sweden)

    Giovanni Andrea Casula

    2016-01-01

    Full Text Available A multiband printed microstrip antenna for wireless communications is presented. The antenna is fed by a proximity-coupled microstrip line, and it is printed on a flexible substrate. The antenna has been designed using a general-purpose 3D computer-aided design software (CAD, CST Microwave Studio, and then realized. The comparison between simulated and measured results shows that the proposed antenna can be used for wireless communications for WLAN systems, covering both the WLAN S-band (2.45 GHz and C-band (5.2 GHz, and the Wi-Max 3.5 GHz band, with satisfactory input matching and broadside radiation pattern. Moreover, it has a compact size, is very easy to realize, and presents a discrete out-of-band rejection, without requiring the use of stop-band filters. The proposed structure can be used also as a conformal antenna, and its frequency response and radiated field are satisfactory for curvatures up to 65°.

  12. Using Huygens Multipole Arrays to Realize Unidirectional Needle-Like Radiation

    Directory of Open Access Journals (Sweden)

    Richard W. Ziolkowski

    2017-07-01

    Full Text Available For nearly a century, the concept of needle radiation has captured the attention of the electromagnetics communities in both physics and engineering, with various types of contributions reoccurring every decade. With the near-term needs for highly directive, electrically small radiators and scatterers for a variety of communications and sensor applications, superdirectivity has again become a topic of interest. While it is well known that superdirective solutions exist and suffer ill-posedness issues in principle, a detailed needle solution has not been reported previously. We demonstrate explicitly, for the first time, how needle radiation can be obtained theoretically from currents driven on an arbitrary spherical surface, and we explain why such a result can only be attained in practice with electrically large spheres. On the other hand, we also demonstrate, more practically, how broadside radiating Huygens source multipoles can be combined into an end-fire array configuration to achieve needle-like radiation performance without suffering the traditional problems that have previously plagued superdirectivity.

  13. A Novel Manufacturing Process for Compact, Low-Weight and Flexible Ultra-Wideband Cavity Backed Textile Antennas

    Directory of Open Access Journals (Sweden)

    Dries Van Baelen

    2018-01-01

    Full Text Available A novel manufacturing procedure for the fabrication of ultra-wideband cavity-backed substrate integrated waveguide antennas on textile substrates is proposed. The antenna cavity is constructed using a single laser-cut electrotextile patch, which is folded around the substrate. Electrotextile slabs protruding from the laser-cut patch are then vertically folded and glued to form the antenna cavity instead of rigid metal tubelets to implement the vertical cavity walls. This approach drastically improves mechanical flexibility, decreases the antenna weight to slightly more than 1 g and significantly reduces alignment errors. As a proof of concept, a cavity-backed substrate integrated waveguide antenna is designed and realized for ultra-wideband operation in the [5.15–5.85] GHz band. Antenna performance is validated in free space as well as in two on body measurement scenarios. Furthermore, the antenna’s figures of merit are characterized when the prototype is bent at different curvature radii, as commonly encountered during deployment on the human body. Also the effect of humidity content on antenna performance is studied. In all scenarios, the realized antenna covers the entire operating frequency band, meanwhile retaining a stable radiation pattern with a broadside gain above 5 dBi, and a radiation efficiency of at least 70%.

  14. Un testimonio temprano de la lira popular chilena: «Dos poetas de poncho» de Zorobabel Rodríguez

    Directory of Open Access Journals (Sweden)

    Cornejo C., Tomás

    2013-12-01

    Full Text Available In 1873 the journalist, academic and Chilean writer Zorobabel Rodríguez published an article about a striking and novel cultural event in the country: the broadside poetry. His text provides substantial information on the distribution of these, the most common themes of the poems, their preferred public and the creative process of the poets, particularly the famous Bernardino Guajardo. In addition, the position taken by Rodriguez highlights the distance between the nineteenth-century men of letters and the culture of the urban poor.En 1873 el periodista, académico y escritor chileno Zorobabel Rodríguez publicó un artículo acerca de una manifestación cultural llamativa y novedosa en el país: los pliegos sueltos de poesía. Su texto aporta cuantiosa información sobre la distribución de estos, los temas más comunes de las poesías, su público preferente y el proceso creativo de los poetas, particularmente el célebre Bernardino Guajardo. Además, la posición adoptada por Rodríguez resalta la distancia entre el mundo letrado decimonónico y las formas culturales de los sectores populares urbanos.

  15. Radar Imaging of Spheres in 3D using MUSIC

    Energy Technology Data Exchange (ETDEWEB)

    Chambers, D H; Berryman, J G

    2003-01-21

    We have shown that multiple spheres can be imaged by linear and planar EM arrays using only one component of polarization. The imaging approach involves calculating the SVD of the scattering response matrix, selecting a subset of singular values that represents noise, and evaluating the MUSIC functional. The noise threshold applied to the spectrum of singular values for optimal performance is typically around 1%. The resulting signal subspace includes more than one singular value per sphere. The presence of reflections from the ground improves height localization, even for a linear array parallel to the ground. However, the interference between direct and reflected energy modulates the field, creating periodic nulls that can obscure targets in typical images. These nulls are largely eliminated by normalizing the MUSIC functional with the broadside beam pattern of the array. The resulting images show excellent localization for 1 and 2 spheres. The performance for the 3 sphere configurations are complicated by shadowing effects and the greater range of the 3rd sphere in case 2. Two of the three spheres are easily located by MUSIC but the third is difficult to distinguish from other local maxima of the complex imaging functional. Improvement is seen when the linear array is replace with a planar array, which increases the effective aperture height. Further analysis of the singular values and their relationship to modes of scattering from the spheres, as well as better ways to exploit polarization, should improve performance. Work along these lines is currently being pursued by the authors.

  16. A High Resolution, Light-Weight, Synthetic Aperture Radar for UAV Application

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, A.W.; Hensley, W.H.; Stence, J.; Tsunoda, S.I. Pace, F.; Walker, B,C.; Woodring, M.

    1999-05-27

    (U) Sandia National Laboratories in collaboration with General Atomics (GA) has designed and built a high resolution, light-weight, Ku-band Synthetic Aperture Radar (SAR) known as "Lynx". Although Lynx can be operated on a wide variety of manned and unmanned platforms, its design is optimized for use on medium altitude Unmanned Aerial Vehicles (UAVS). In particular, it can be operated on the Predator, I-GNAT, and Prowler II platforms manufactured by GA. (U) The radar production weight is less than 120 lb and operates within a 3 GHz band from 15.2 GHz to 18.2 GHz with a peak output power of 320 W. Operating range is resolution and mode dependent but can exceed 45 km in adverse weather (4 mm/hr rain). Lynx has operator selectable resolution and is capable of 0.1 m resolution in spotlight mode and 0.3 m resolution in stripmap mode, over substantial depression angles (5 to 60 deg) and squint angles (broadside ±45 deg). Real-time Motion Compensation is implemented to allow high-quality image formation even during vehicle turns and other maneuvers.

  17. Nonuniformly Spaced Linear Antenna Array Design Using Firefly Algorithm

    Directory of Open Access Journals (Sweden)

    Mohammad Asif Zaman

    2012-01-01

    Full Text Available A nonuniformly spaced linear antenna array with broadside radiation characteristics is synthesized using firefly algorithm and particle swarm optimization. The objective of the work is to find the optimum spacing between the radiating antenna elements which will create a predefined arbitrary radiation pattern. The excitation amplitudes of all the antenna elements are assumed to be constant. The optimum spacing between the array elements are obtained using firefly algorithm. The minimum allowed distance between the antenna elements is defined in such a way that mutual coupling between the elements can be ignored. Numerical analysis is performed to calculate the far-field radiation characteristics of the array. Two numerical examples are shown to form two different desired predefined radiation patterns. The performance of the firefly algorithm and particle swarm optimization is compared in terms of convergence rate and global best solution achieved. The performances of the optimized nonuniformly spaced arrays are analyzed. Finally, contour plots of the radiated power from the optimized array in the horizontal plane and vertical plane in the far-field region are provided.

  18. Cylindrical sound wave generated by shock-vortex interaction

    Science.gov (United States)

    Ribner, H. S.

    1985-01-01

    The passage of a columnar vortex broadside through a shock is investigated. This has been suggested as a crude, but deterministic, model of the generation of 'shock noise' by the turbulence in supersonic jets. The vortex is decomposed by Fourier transform into plane sinusoidal shear waves disposed with radial symmetry. The plane sound waves produced by each shear wave/shock interaction are recombined in the Fourier integral. The waves possess an envelope that is essentially a growing cylindrical sound wave centered at the transmitted vortex. The pressure jump across the nominal radius R = ct attenuates with time as 1/(square root of R) and varies around the arc in an antisymmetric fashion resembling a quadrupole field. Very good agreement, except near the shock, is found with the antisymmetric component of reported interferometric measurements in a shock tube. Beyond the front r approximately equals R is a precursor of opposite sign, that decays like 1/R, generated by the 1/r potential flow around the vortex core. The present work is essentially an extension and update of an early approximate study at M = 1.25. It covers the range (R/core radius) = 10, 100, 1000, and 10,000 for M = 1.25 and (in part) for M = 1.29 and, for fixed (R/core radius) = 1000, the range M = 1.01 to infinity.

  19. Wavenumber Domain Focusing of Squinted SAR Data with a Curved Orbit Geometry

    Science.gov (United States)

    Thierry, Michal; Hensley, Scott

    2008-01-01

    Synthetic Aperture Radar systems provide raw data that need focusing to achieve full-resolution imaging. Current SAR applications, including interferometry, require accurate, phase-preserving, and precisely co-registered coherent images over large ground swaths with the highest achievable resolution. In addition to these challenges, stripmap SAR data may be acquired with an off-broadside (squinted) geometry, either by design or through platform motion. The precise batch focusing of these large aperture and wide bandwidth data sets is known to require a 2D frequency processing approach. The standard wave domain focusing algorithm, however, is only exact for data acquired on a rectilinear trajectory. We investigate a generalization of the standard omega-k focusing formulation that allows curved data acquisition tracks. The new formulation can be used in conjunction with a known extension for conical, squinted imaging grids. The approximations necessary to allow the generalized geometry are analyzed to determine the range of applicability of the proposed algorithm. The theory is validated using data simulated with parameters similar to the UAVSAR L-band SAR system.

  20. Acoustic Measurements of Rectangular Nozzles With Bevel

    Science.gov (United States)

    Bridges, James E.

    2012-01-01

    A series of convergent rectangular nozzles of aspect ratios 2:1, 4:1, and 8:1 were constructed with uniform exit velocity profiles. Additional nozzles were constructed that extended the wide lip on one side of these nozzles to form beveled nozzles. Far-field acoustic measurements were made and analyzed, and the results presented. The impact of aspect ratio on jet noise was similar to that of enhanced mixing devices: reduction in aft, peak frequency noise with an increase in broadside, high frequency noise. Azimuthally, it was found that rectangular jets produced more noise directed away from their wide sides than from their narrow sides. The azimuthal dependence decreased at aft angles where noise decreased. The effect of temperature, keeping acoustic Mach number constant, was minimal. Since most installations would have the observer on the wide size of the nozzle, the increased high frequency noise has a deleterious impact on the observer. Extending one wide side of the rectangular nozzle, evocative of an aft deck in an installed propulsion system, increased the noise of the jet with increasing length. The impact of both aspect ratio and bevel length were relatively well behaved, allowing a simple bilinear model to be constructed relative to a simple round jet.

  1. A Model of Double-Directional Indoor Channels for Multiterminal Communications

    Directory of Open Access Journals (Sweden)

    Puji Handayani

    2013-01-01

    Full Text Available We propose a model of double-directional indoor nonline of sight (NLOS channels for multiterminal communications. We derive a simple channel matrix that describes input-output relationship for such channels. The multiterminal systems may consist of several terminals that act as amplify-and-forward (AF relays, where source, relays, and destination have arbitrary numbers of antennas. We complete our model by characterizing the parameters of double-directional channel impulse response of such channels through measurements in indoor environment using 3D synthetic array antenna at 2.5 GHz band. To find out the relation between spatial characteristic of channels in each hop, we observe the direction of arrival (DOA and direction of departure (DOD of multipath component signals at the terminal that acts as relay. We find that there are several closely matched azimuths of DOAs and azimuths of DODs which follow uniform distribution in the range of −180° to 180° for elevation around the broadside direction of vertical omnidirectional elements of arrays.

  2. Observations of CMEs and Models of the Eruptive Corona

    Science.gov (United States)

    Gopalswamy, Nat

    2012-01-01

    It is now realized that coronal mass ejections (CMEs) are the most energetic phenomenon in the heliosphere. Although early observations (in the 1970s and 19805) revealed most of the properties of CMEs, it is the extended and uniform data set from the Solar and Heliospheric Observatory (SOHO) mission that helped us consolidate our knowledge on CMEs. The Solar Terrestrial Relations Observatory (STEREO) mission has provided direct confirmation of the three-dimensional structure of CMEs. The broadside view provided by the STEREO coronagraphs helped us estimate the width of the halo CMEs and hence validate CME cone models. Current theoretical ideas on the internal structure of CMEs suggest that a flux rope is central to the CME structure, which has considerable observational support both from remote-sensing and in-situ observations. The flux-rope nature is also consistent with the post-eruption arcades with high-temperature plasma and the charge states observed within CMEs arriving at Earth. The quadrature observations also helped us understand the relation between the radial and expansion speeds of CMEs, which were only known from empirical relations in the past. This paper highlights some of these results obtained during solar cycle 23 and 24 and discusses implications for CME models.

  3. Advances in GPR data acquisition and analysis for archaeology

    Science.gov (United States)

    Zhao, Wenke; Tian, Gang; Forte, Emanuele; Pipan, Michele; Wang, Yimin; Li, Xuejing; Shi, Zhanjie; Liu, Haiyan

    2015-07-01

    The primary objective of this study is to evaluate the applicability and the effectiveness of ground-penetrating radar (GPR) to identify a thin burnt soil layer, buried more than 2 m below the topographic surface at the Liangzhu Site, in Southeastern China. The site was chosen for its relatively challenging conditions of GPR techniques due to electrical conductivity and to the presence of peach tree roots that produced scattering. We completed the data acquisition by using 100 and 200 MHz antennas in TE and TM broadside and cross-polarized configurations. In the data processing and interpretation phase, we used GPR attribute analysis, including instantaneous phase and geometrical attributes. Validation analysis ground-truthing performed after the geophysical surveys, validated the GPR imaging, confirmed the electrical conductivity and relative dielectric permittivity (RDP) measurements performed at different depths, and allowed a reliable quantitative correlation between GPR results and subsurface physical properties. The research demonstrates that multiple antenna configurations in GPR data acquisition combined with attribute analysis can enhance the ability to characterize prehistoric archaeological remains even in complex subsurface conditions.

  4. Enhanced-gain printed slot antenna using an electric metasurface superstrate

    Science.gov (United States)

    Sarkhel, Abhishek; Bhadra Chaudhuri, Sekhar Ranjan

    2016-10-01

    In this article, a method to enhance the radiation characteristics of a slot antenna by using an electric metasurface as a high refractive index superstrate has been presented. The gain enhancement mechanism described here uses the phenomena of enhanced space field by increasing the effective aperture of the antenna, resulting from increase in effective refractive index of the metasurface. As a fundamental constituent of the superstrate, a unit cell of the metasurface composed of symmetrically placed triple pairs of split-ring resonators is introduced. The unit cell of such metasurface has been configured to realize a high refractive index by using the principle of nearest-neighbor coupling. An equivalent circuit model is developed to understand the influence of coupling on the effective refractive index of the metasurface. The presence of the metasurface as a superstrate enhances the broadside gain of the slot by 8.71 dB and the efficiency by 20.35 %. The total height of the proposed configuration is 0.237 λ 0 where λ 0 is the free space wavelength at the resonance frequency of the slot antenna.

  5. The Resolving Capabilities of Marine CSEM for a TIV Anisotropic Earth: Practical Implications for Data Acquisition and Inversion

    Science.gov (United States)

    Ray, A.; Key, K. W.; Constable, S.

    2011-12-01

    The marine controlled source electromagnetic (CSEM) method has been commercially used over the last ten years to map resistive hydrocarbons under the seafloor in deepwater environments and to a lesser extent in shallow water. The use of CSEM depends on the conductivity contrasts between relatively conductive porous marine sediments and resistive hydrocarbon reservoirs. However, the role of anisotropy in marine sediment conductivity has not been well studied in the context of CSEM's resolving capabilities. The constitutive relations used by Maxwell's equations in the presence of anisotropy lead to EM field responses, which, depending upon the geology can be quite different from the isotropic response. This work undertakes a systematic study of the ability to resolve sediment and reservoir level anisotropy using different transmitter types (electric and magnetic dipoles), transmitter orientations (horizontal and vertical), receiver components (horizontal and vertical electric and magnetic fields) and receiver locations (inline and broadside). To better illustrate the physics involved, a modeling code based on a 1D earth that exhibits transverse isotropy with a vertical symmetry axis (TIV anisotropy) has been employed to comprehensively examine the response-misfit space for the anisotropic layer parameters. This study helps determine which EM field components are most important to acquire in practice, in addition to clarifying if there are any redundancies in the information contained among a suite of field components. Since anisotropy is a phenomenon present in varying degrees in most marine sediments, from a practical point of view, this work provides a template for designing a successful hydrocarbon mapping technique.

  6. Red blood cell orientation in pulmonary capillaries and its effect on gas diffusion.

    Science.gov (United States)

    Nabors, L Karina; Baumgartner, William A; Janke, Steven J; Rose, James R; Wagner, Wiltz W; Capen, Ronald L

    2003-04-01

    When alveoli are inflated, the stretched alveolar walls draw their capillaries into oval cross sections. This causes the disk-shaped red blood cells to be oriented near alveolar gas, thereby minimizing diffusion distance. We tested these ideas by measuring red blood cell orientation in histological slides from rapidly frozen rat lungs. High lung inflation did cause the capillaries to have oval cross sections, which constrained the red blood cells within them to flow with their broad sides facing alveolar gas. Low lung inflation stretched alveolar walls less and allowed the capillaries to assume a circular cross section. The circular luminal profile permitted the red blood cells to have their edges facing alveolar gas, which increased the diffusion distance. Using a finite-element method to calculate the diffusing capacity of red blood cells in the broad-side and edge-on orientations, we found that edge-on red blood cells had a 40% lower diffusing capacity. This suggests that, when capillary cross sections become circular, whether through low-alveolar volume or through increased microvascular pressure, the red blood cells are likely to be less favorably oriented for gas exchange.

  7. Using Huygens Multipole Arrays to Realize Unidirectional Needle-Like Radiation

    Science.gov (United States)

    Ziolkowski, Richard W.

    2017-07-01

    For nearly a century, the concept of needle radiation has captured the attention of the electromagnetics communities in both physics and engineering, with various types of contributions reoccurring every decade. With the near-term needs for highly directive, electrically small radiators and scatterers for a variety of communications and sensor applications, superdirectivity has again become a topic of interest. While it is well known that superdirective solutions exist and suffer ill-posedness issues in principle, a detailed needle solution has not been reported previously. We demonstrate explicitly, for the first time, how needle radiation can be obtained theoretically from currents driven on an arbitrary spherical surface, and we explain why such a result can only be attained in practice with electrically large spheres. On the other hand, we also demonstrate, more practically, how broadside radiating Huygens source multipoles can be combined into an end-fire array configuration to achieve needle-like radiation performance without suffering the traditional problems that have previously plagued superdirectivity.

  8. Improvement of RF Wireless Power Transmission Using a Circularly Polarized Retrodirective Antenna Array with EBG Structures

    Directory of Open Access Journals (Sweden)

    Son Trinh-Van

    2018-02-01

    Full Text Available This paper presents the performance improvement of a circularly polarized (CP retrodirective array (RDA through the suppression of mutual coupling effects. The RDA is designed based on CP Koch-shaped patch antenna elements with an inter-element spacing as small as 0.4 λ for a compact size ( λ is the wavelength in free space at the designed frequency of 5.2 GHz. Electromagnetic band gap (EBG structures are applied to reduce the mutual coupling between the antenna elements, thus improving the circular polarization characteristic of the RDA. Two CP RDAs with EBGs, in the case 5 × 5 and 10 × 10 arrays, are used as wireless power transmitters to transmit a total power of 50 W. A receiver is located at a distance of 1 m away from the transmitter to harvest the transmitted power. At the broadside direction, the simulated results demonstrate that the received powers are improved by approximately 11.32% and 12.45% when using the 5 × 5 and 10 × 10 CP RDAs with the EBGs, respectively, as the transmitters.

  9. QPSO for failure correction of linear array of mutually coupled parallel dipole antennas with desired side lobe level and return loss

    Directory of Open Access Journals (Sweden)

    R. Muralidharan

    2017-04-01

    Full Text Available A method based on quantum particle swarm optimization is proposed for correcting radiation pattern of a uniformly spaced linear array of parallel half-wavelength vertical very thin dipole antennas when more than one element of the array is completely defective. The generated pattern is broadside in the horizontal plane. Mutual coupling between the half-wavelength parallel dipole antennas has been taken care of by induced EMF method considering the current distribution on each dipole to be sinusoidal. Side lobe level and minimum return loss of the corrected pattern with defective elements are also calculated and an attempt is made that these parameters be equal to their respective specified values. This is usually done by changing excitation current amplitude of the non-defective elements without replacing the faulty elements. The element pattern of half-wavelength dipole antenna has been assumed omni-directional in the horizontal plane. Two examples are presented to show the effectiveness of the proposed approach.

  10. A Compact Dual-Band Printed Antenna Design for LTE Operation in Handheld Device Applications

    Directory of Open Access Journals (Sweden)

    Ding-Bing Lin

    2014-01-01

    Full Text Available A novel internal printed antenna suitable for triple long-term evolution (LTE bands for handheld devices is presented. The operating bandwidths of the design are LTE700 (698~800 MHz, LTE2300 (2300~2400 MHz, and LTE2500 (2500~2690 MHz. Through the use of a C-shape broadside coupled feed structure, full operation in the lower band is achieved. The antenna itself uses two unequal path lengths to produce a low frequency band with two resonant modes. The required bandwidth is then adjusted using a couple feed, and finally placed over a ground plane via another C-type coupling element in order to enhance the two low-frequency matches. In the definition of the −6 dB reflection coefficient, the bandwidth of two basic modes in the low frequency band is 0.689~0.8 GHz. We adopt the definition of the −10 dB reflection coefficient for the high frequency mode, and its working frequency bands are shown to be 2.3~2.72 GHz. The antenna size is only 40 × 12 × 0.8 mm3 with a ground plane of 98 × 40 mm2.

  11. Dual-Vivaldi wideband nanoantenna with high radiation efficiency over the infrared frequency band.

    Science.gov (United States)

    Iluz, Zeev; Boag, Amir

    2011-08-01

    A dual-Vivaldi nanoantenna is proposed to demonstrate the possibility of wideband operation at IR frequencies. The antenna geometry design is guided by the material properties of metals at IR frequencies. According to our numerical results, this nanoantenna has both high radiation efficiency and good impedance-matching properties over a wide frequency band (more than 122%) in the IR frequency band. The design is based on the well-known Vivaldi antenna placed on quartz substrate but operating as a pair instead of a single element. Such a pair of Vivaldi antennas oriented in opposite directions produces the main lobe in the broadside direction (normal to the axes of the antennas) rather than the usual peak gain along the axis (end fire) of a single Vivaldi antenna. The dual-Vivaldi nanoantenna is easy to fabricate in a conventional electron-beam lithography process, and it provides a large number of degrees of freedom, facilitating design for ultra-wideband operation. © 2011 Optical Society of America

  12. Boundary Effects on the Drag of a Cylinder in Axial Motion at Low Reynolds Number.

    Science.gov (United States)

    Wehbeh, Elias George

    1987-09-01

    This work is an experimental study of the Stokes drag on a right circular cylinder moving with constant velocity through a Newtonian viscous fluid. The cylinder velocity is parallel to its longitudinal axis, and the fluid is bounded on the outside by a fixed coaxial cylindrical tube of circular cross section. The length to diameter ratio of the moving cylinder ranges from 1.0 to 390, the ratio of the width of the annular gap to the cylinder length ranges from 0.0077 to 0.86, and the ratio alpha of the cylinder diameter to the tube diameter ranges from 0.022 to 0.91. Experimental values of the drag are compared with a theoretical expression which assumes a flow that is entirely axial in the annular region and a drag that is due entirely to the viscous stress on the cylinder side plus the effect of the dynamic pressure difference on the ends of the cylinder. An end correction term is obtained which is found to be proportional to the annular gap width and to the square root of alpha . This term is found to be consistent with previous numerical studies of the narrow gap case and with experimental studies of the wide gap case. Drag values are also presented for the situation in which the bottom of the tube is open to a larger fluid reservoir. A second problem is considered in which a thin circular disk moves broadside through a viscous fluid toward a plane wall that is parallel to the disk. An expression for the Stokes drag is obtained which agrees with the experiment and reduces to known theoretical results at extremes of large and small distances from the disk to the plane.

  13. Self-diffusion in the non-Newtonian regime of shearing liquid crystal model systems based on the Gay-Berne potential

    Energy Technology Data Exchange (ETDEWEB)

    Sarman, Sten, E-mail: sarman@ownit.nu; Wang, Yong-Lei; Laaksonen, Aatto [Arrhenius Laboratory, Department of Materials and Environmental Chemistry, Stockholm University, 106 91 Stockholm (Sweden)

    2016-02-07

    The self-diffusion coefficients of nematic phases of various model systems consisting of regular convex calamitic and discotic ellipsoids and non-convex bodies such as bent-core molecules and soft ellipsoid strings have been obtained as functions of the shear rate in a shear flow. Then the self-diffusion coefficient is a second rank tensor with three different diagonal components and two off-diagonal components. These coefficients were found to be determined by a combination of two mechanisms, which previously have been found to govern the self-diffusion of shearing isotropic liquids, namely, (i) shear alignment enhancing the diffusion in the direction parallel to the streamlines and hindering the diffusion in the perpendicular directions and (ii) the distortion of the shell structure in the liquid whereby a molecule more readily can escape from a surrounding shell of nearest neighbors, so that the mobility increases in every direction. Thus, the diffusion parallel to the streamlines always increases with the shear rate since these mechanisms cooperate in this direction. In the perpendicular directions, these mechanisms counteract each other so that the behaviour becomes less regular. In the case of the nematic phases of the calamitic and discotic ellipsoids and of the bent core molecules, mechanism (ii) prevails so that the diffusion coefficients increase. However, the diffusion coefficients of the soft ellipsoid strings decrease in the direction of the velocity gradient because the broadsides of these molecules are oriented perpendicularly to this direction due the shear alignment (i). The cross coupling coefficient relating a gradient of tracer particles in the direction of the velocity gradient and their flow in the direction of the streamlines is negative and rather large, whereas the other coupling coefficient relating a gradient in the direction of the streamlines and a flow in the direction of the velocity gradient is very small.

  14. Self-diffusion in the non-Newtonian regime of shearing liquid crystal model systems based on the Gay-Berne potential.

    Science.gov (United States)

    Sarman, Sten; Wang, Yong-Lei; Laaksonen, Aatto

    2016-02-07

    The self-diffusion coefficients of nematic phases of various model systems consisting of regular convex calamitic and discotic ellipsoids and non-convex bodies such as bent-core molecules and soft ellipsoid strings have been obtained as functions of the shear rate in a shear flow. Then the self-diffusion coefficient is a second rank tensor with three different diagonal components and two off-diagonal components. These coefficients were found to be determined by a combination of two mechanisms, which previously have been found to govern the self-diffusion of shearing isotropic liquids, namely, (i) shear alignment enhancing the diffusion in the direction parallel to the streamlines and hindering the diffusion in the perpendicular directions and (ii) the distortion of the shell structure in the liquid whereby a molecule more readily can escape from a surrounding shell of nearest neighbors, so that the mobility increases in every direction. Thus, the diffusion parallel to the streamlines always increases with the shear rate since these mechanisms cooperate in this direction. In the perpendicular directions, these mechanisms counteract each other so that the behaviour becomes less regular. In the case of the nematic phases of the calamitic and discotic ellipsoids and of the bent core molecules, mechanism (ii) prevails so that the diffusion coefficients increase. However, the diffusion coefficients of the soft ellipsoid strings decrease in the direction of the velocity gradient because the broadsides of these molecules are oriented perpendicularly to this direction due the shear alignment (i). The cross coupling coefficient relating a gradient of tracer particles in the direction of the velocity gradient and their flow in the direction of the streamlines is negative and rather large, whereas the other coupling coefficient relating a gradient in the direction of the streamlines and a flow in the direction of the velocity gradient is very small.

  15. Shielded Micro-Coplanar CRLH TL Zeroth-Order Resonator Antenna: Critical Performance Evaluation

    Directory of Open Access Journals (Sweden)

    M. Polivka

    2009-12-01

    Full Text Available The attention of this paper is focused on the four unit cell zeroth-order resonator antenna (ZORA, manufactured on a shielded micro-coplanar composite right/left-handed (CRLH transmission line structure. The antenna was designed to achieve a broadside patch-type radiation pattern. The dimensions of the antenna element follow: 15.6 x 9.35 x 3.1 mm (i.e. 0.27 x 0.16 x 0.05 λ0 at the measured zeroth-order resonance f0 = 5.14 GHz with the shielded plane of the size of 60 x 40 mm (approx. 1.0 x 0.7 λ0. The measured gain and the antenna efficiency are equal to 4.6 dBi and 48 %, respectively. The performance of the proposed ZORA is subject to critical evaluation based on the comparison with the reference quarter-wavelength patch antenna (QWPA that has the same dimensions. It has been found that ZORA provides comparable or even better parameters to those of QWPA, except of the bandwidth, which is much narrower in case of ZORA. In comparison to QWPA, the main advantage of the proposed ZORA might be then seen in the possibility to produce the entire ZORA structure by means of the integrated microstrip technology with air bridges. In contrary to it, the fabrication of the QWPA requires the use of either the foam substrate or plastic support pins or the application of ridged self-supporting metal plates.

  16. GPR amplitude reflection coefficient estimates from reflected amplitude obtained from Common Mid-Point surveys

    Science.gov (United States)

    Kana, A. A.; West, J. L.; Clark, R.

    2009-12-01

    Ground penetrating radar offers the potential to image individual rock fractures, and can potentially provide much-needed information on fracture aperture and hence permeability. However, estimation of fracture properties from radar requires determination of the reflection co-efficient (R) of individual fractures. The reflected amplitude measured at the receiver is related to reflection coefficient, but it is also affected by other factors including transmitter power and coupling with the ground, the antenna radiation pattern, incident angle, geometric spreading and intrinsic attenuation within the rock matrix (and hence the ray path length). Hence, obtaining absolute R values for fractures is a non-trivial exercise. Here we present an approach for the estimation of bedding plane fracture R based on the variation in reflection amplitude with incident angle and polarization determined in CMP (Common Mid-Point) surveys. A 500MHz radar Common Offset (CO) profile was acquired on Carboniferous Limestone in West Yorkshire, United Kingdom. CMP data were acquired at specific points along the profile using both broadside (TE) and endfire (TM) acquisition modes. Attenuation characteristics for the limestone and antenna radiation pattern in this lithology were estimated from transillumination surveys. The variation in reflected amplitude with incident angle was determined for bedding plane fractures identified in the CMP data. After correcting these reflected amplitudes for attenuation, radiation pattern and geometric spreading, reflection amplitude versus incident angle curves were compared with theoretical predictions expected for thin water-filled parallel-sided fractures. Preliminary analysis indicate that TE and TM mode responses match theoretical predictions which suggests this approach can be used to obtain R values from CMP surveys.

  17. Design of a wide-gain-bandwidth metasurface antenna at terahertz frequency

    Science.gov (United States)

    Hussain, Niamat; Park, Ikmo

    2017-05-01

    This paper presents the design of a planar low-profile, wide-gain-bandwidth metasurface antenna at terahertz frequency. The proposed antenna consists of a metasurface and a planar feeding structure, both of which are patterned on an electrically thin, high-permittivity GaAs substrate. The metasurface, which is printed on the top of the substrate, consists of a periodic array of 5×5 square patches, while the planar feeding structure, which is printed on the bottom of the substrate, is a wideband, leaky-wave, open-ended slotline, which is fed at the center. The antenna with a single feeding structure showed a maximum broadside gain of 9.8 dBi, a radiation efficiency of 69%, and a 3-dB gain bandwidth of 16% (0.34-0.4 THz). The antenna gain performance was significantly improved by exciting the antenna with an array of slit feeding and without changing the antenna size. The antenna with a multiple (five) feeding structure showed a gain of 15.5 dBi, a 3-dB gain bandwidth of 17.3%, and a radiation efficiency of 73%. This antenna achieved a size reduction of 31 times in terms of device thickness in comparison with the design of the lens coupled antenna while achieving a comparable gain. In addition to its high gain and wide-gain-bandwidth characteristics, the proposed antenna design exhibits a low-profile mechanical robustness, easy integration into circuit boards, and excellent low-cost mass production suitability.

  18. Radiation forces and torque on a rigid elliptical cylinder in acoustical plane progressive and (quasi)standing waves with arbitrary incidence

    Energy Technology Data Exchange (ETDEWEB)

    Mitri, F. G., E-mail: F.G.Mitri@ieee.org [Chevron, Area 52 Technology—ETC, Santa Fe, New Mexico 87508 (United States)

    2016-07-15

    This paper presents two key contributions; the first concerns the development of analytical expressions for the axial and transverse acoustic radiation forces exerted on a 2D rigid elliptical cylinder placed in the field of plane progressive, quasi-standing, or standing waves with arbitrary incidence. The second emphasis is on the acoustic radiation torque per length. The rigid elliptical cylinder case is important to be considered as a first-order approximation of the behavior of a cylindrical fluid column trapped in air because of the significant acoustic impedance mismatch at the particle boundary. Based on the rigorous partial-wave series expansion method in cylindrical coordinates, non-dimensional acoustic radiation force and torque functions are derived and defined in terms of the scattering coefficients of the elliptic cylinder. A coupled system of linear equations is obtained after applying the Neumann boundary condition for an immovable surface in a non-viscous fluid and solved numerically by matrix inversion after performing a single numerical integration procedure. Computational results for the non-dimensional force components and torque, showing the transition from the progressive to the (equi-amplitude) standing wave behavior, are performed with particular emphasis on the aspect ratio a/b, where a and b are the semi-axes of the ellipse, the dimensionless size parameter, as well as the angle of incidence ranging from end-on to broadside incidence. The results show that the elliptical geometry has a direct influence on the radiation force and torque, so that the standard theory for circular cylinders (at normal incidence) leads to significant miscalculations when the cylinder cross section becomes non-circular. Moreover, the elliptical cylinder experiences, in addition to the acoustic radiation force, a radiation torque that vanishes for the circular cylinder case. The application of the formalism presented here may be extended to other 2D surfaces of

  19. Geodynamics and The Evolution of Continental Lithosphere

    Science.gov (United States)

    Hamilton, W. B.

    roll back into subducting plates, and slabs sink broadside, pushing sub-lithospheric mantle back into the oceans from whence they came, forcing spreading therein. Slabs are plated down on, and de- press, the 660-km discontinuity, and are overpassed by overriding plates, like tanks above basal treads, transferring mantle to passively spreading oceans. No compelling evidence indicates plate-tectonic circulation to extend deeper than the 660-km discon- tinuity, and cosmologic and thermodynamic data are incompatible with deep circula- tion. Post-2.0 Ga circulation, with lessening re-fractionation, has made crust gradually more mafic, and upper mantle gradually more felsic.

  20. The killing efficiency of soft iron shot

    Science.gov (United States)

    Andrews, R.; Longcore, J.R.

    1969-01-01

    A cooperative research effort between the ammunition industry and the Bureau of Sport Fisheries and Wildlife is aimed at finding a suitable non-toxic substitute for lead shot. A contract study by an independent research organization evaluated ways of coating or detoxifying lead shot or replacing it with another metal. As a result of that study, the only promising candidate is soft iron. Previous tests of hard iron shot had suggested that its killing effectiveness was poor at longer ranges due to the lower density. In addition, its hardness caused excessive damage to shotgun barrels. A unique, automated shooting facility was constructed at the Patuxent Wildlife Research Center to test the killing effectiveness of soft iron shot under controlled conditions. Tethered game-farm mallards were transported across a shooting point in a manner simulating free flight. A microswitch triggered a mounted shotgun so that each shot was 'perfect.' A soft iron shot, in Number 4 size, was produced by the ammunition industry and loaded in 12-gauge shells to give optimum ballistic performance. Commercial loads of lead shot in both Number 4 and Number 6 size were used for comparison. A total of 2,010 ducks were shot at ranges of 30 to 65 yards and at broadside and head-on angles in a statistically designed procedure. The following data were recorded for each duck: time until death, broken wing or leg bones, and number of embedded shot. Those ducks not killed outright were held for 10 days. From these data, ducks were categorized as 'probably bagged,' 'probably lost cripples,' or survivors. The test revealed that the killing effectiveness of this soft iron shot was superior to its anticipated performance and close to that obtained with commercial lead loads containing an equal number of pellets. Bagging a duck, in terms of rapid death or broken wing, was primarily dependent on the probability of a shot striking that vital area, and therefore a function of range. There was no indication

  1. Stitch and hem and line and flight

    Science.gov (United States)

    Thorp, John Daniel

    Stitch and hem and line and flight appears in four formats. There is this present one, which adheres to the manuscript design requirements as outlined by The Graduate School at The University of Utah; there is another which is a book six inches high by nine inches wide, printed in three colors, with text aligned to its gutter; and there is a broadside printed from the same forms of standing metal type on a single twelve-inch-high by nineteen-inch-wide page, where all spreads are registered to the same points so that all lines of all sections overlap exactly, excluding the last lines of the longest section, which are left immediately readable. The second and the third formats were produced in editions of fifty each, and copies are available to the reader through the Special Collections Library at the J. Willard Marriott Library. The text in the book you're holding is built from scans taken from the original letterpress pages, and so honors typos not caught before production during proofreading, but does not honor the final runs of production which overprint eight typos and overprint one duplicated "no." The text here stands as an uncorrected and reformatted transcript of the letterpress-printed pages, since all "characters must be clear and sharp. Smudged, indistinct, or blurred letters are not acceptable." The present format cannot ask (at least not in the same way) if the techniques and repetitive labor of hand printing can be read just as one might read any of the other more familiar small crises in a work: the line break, the influence of a culture or history on that work, anagnorisis, exegesis, etc. The present format doesn't seem to ask questions like: what happens to a love song when you can't read it or hear it? How does a line or letter make itself mean when cast in metal, stood up and pressed onto paper? Still, the present format is concerned with how a line sits on a page and how a line is like love is like highs is like sand. The text all these formats

  2. A Geometric Analysis to Protect Manned Assets from Newly Launched Objects - COLA Gap Analysis

    Science.gov (United States)

    Hametz, Mark E.; Beaver, Brian A.

    2012-01-01

    period is also not practical due to the limiting effects of these large orbit state uncertainties. An estimated upper bound for Pc for a typical spent upper stage if nominally aligned for a direct broadside collision with the ISS is only on the order of 10-6. For a smaller manned object such as a Soyuz capsule, the risk level decreases to an order of 10'8 . In comparison, the Air Force Range policy (AFI 91-217) for launch COLAs would only eliminate launch opportunities when conjunctions with objects exceed a Pc of 10'5 This paper demonstrates a conservative geometry-based methodology that may be used to determine if launch opportunities pose a threat to the ISS during the COLA gap period. The NASA Launch Services Program at Kennedy Space Center has developed this COLA gap analysis method and employed it fQr three NASA missions to identify potential ISS conjunctions and corresponding launch window closures during the 56-hour at-risk period. In the analysis, for each launch opportunity, the nominal trajectory of the spent upper stage and the orbit state of the ISS are propagated over the 56 hour period. Each time the upper stage crosses the orbit plane of the ISS, the relative radial and argument of latitude separations are calculated. A window cutout is identified if these separation differences fall within a mission-specific violation box, which is determined from the evaluation of a Monte Carlo dispersions analysis that quantifies the potential variation in the upper stage radial and argument of latitude differences. This paper details the results of these analyses and their impacts to each mission.

  3. Theory of a Traveling Wave Feed for a Planar Slot Array Antenna

    Science.gov (United States)

    Rengarajan, Sembiam

    2012-01-01

    Planar arrays of waveguide-fed slots have been employed in many radar and remote sensing applications. Such arrays are designed in the standing wave configuration because of high efficiency. Traveling wave arrays can produce greater bandwidth at the expense of efficiency due to power loss in the load or loads. Traveling wave planar slot arrays may be designed with a long feed waveguide consisting of centered-inclined coupling slots. The feed waveguide is terminated in a matched load, and the element spacing in the feed waveguide is chosen to produce a beam squinted from the broadside. The traveling wave planar slot array consists of a long feed waveguide containing resonant-centered inclined coupling slots in the broad wall, coupling power into an array of stacked radiating waveguides orthogonal to it. The radiating waveguides consist of longitudinal offset radiating slots in a standing wave configuration. For the traveling wave feed of a planar slot array, one has to design the tilt angle and length of each coupling slot such that the amplitude and phase of excitation of each radiating waveguide are close to the desired values. The coupling slot spacing is chosen for an appropriate beam squint. Scattering matrix parameters of resonant coupling slots are used in the design process to produce appropriate excitations of radiating waveguides with constraints placed only on amplitudes. Since the radiating slots in each radiating waveguide are designed to produce a certain total admittance, the scattering (S) matrix of each coupling slot is reduced to a 2x2 matrix. Elements of each 2x2 S-matrix and the amount of coupling into the corresponding radiating waveguide are expressed in terms of the element S11. S matrices are converted into transmission (T) matrices, and the T matrices are multiplied to cascade the coupling slots and waveguide sections, starting from the load end and proceeding towards the source. While the use of non-resonant coupling slots may provide an

  4. Mode Theory of Multi-Armed Spiral Antennas and Its Application to Electronic Warfare Antennas

    Science.gov (United States)

    Radway, Matthew J.

    Since their invention about 55 years ago, spiral antennas have earned a reputation for providing stable impedance and far-field patterns over multi-decade frequency ranges. For the first few decades these antennas were researched for electronic warfare receiving applications, primarily in the 2-18 GHz range. This research was often done under conditions of secrecy, and often by private contractors who did not readily share their research, and now have been defunct for decades. Even so, the body of literature on the two-armed variant of these antennas is rich, often leading non-specialists to the misconception that these antennas are completely understood. Furthermore, early work was highly experimental in nature, and was conducted before modern data collection and postprocessing capabilities were widespread, which limited the range of the studies. Recent research efforts have focused on extending the application of spirals into new areas, as well as applying exotic materials to `improve' their performance and reduce their size. While interesting results have been obtained, in most instances these were incomplete, often compromising the frequency independent nature of these antennas. This thesis expands the role of the multi-armed spiral outside of its traditional niche of receive-only monopulse direction finding. As a first step, careful study of the spiral-antenna mode theory is undertaken with particular attention paid to the concepts of mode filtering and modal decomposition. A technique for reducing the modal impedance of high arm-count spirals is introduced. The insights gained through this theoretical study are first used to improve the far-field performance of the coiled-arm spiral antenna. Specifically, expanding the number of arms on a coiled arm spiral from two to four while providing proper excitation enables dramatically improved broadside axial ratio and azimuthal pattern uniformity. The multiarming technique is then applied to the design of an antenna

  5. Traffic accidents with motorcycles and their relationship to mortality Ocurrencias de tránsito con motocicleta y su relación con la mortalidad Ocorrências de trânsito com motocicleta e sua relação com a mortalidade

    Directory of Open Access Journals (Sweden)

    Nelson Luiz Batista de Oliveira

    2011-04-01

    Full Text Available This study characterizes traffic accidents involving motorcycles according to local conditions, data concerning the type of accident, date and time, and identifies among these variables those associated with the death of victims. This retrospective study uses data from traffic collision reports from 2004 and death records from the institute of forensic medicine. A total of 99.4% of the events occurred in urban areas, where illumination (87.4%, weather conditions (80.6%; and traffic signs (70.6% were satisfactory. Collisions between motorcycles and cars or pickup trucks prevailed (55.5%, followed by motorcycle falls (18.0%. In relation to the type of collision, the highest percentage was observed in broadside collision category (35.2%. There were differences between the groups of fatalities and survivors in relation to the area and illumination in the collision’s site, in addition to the types of collision and impact. The conclusion is that local conditions and types of collision and impact stand out among the multiple variables defining the severity of accidents involving motorcycles.Se tuvo por objetivo caracterizar las ocurrencias de tránsito con motocicleta, según condiciones locales, datos relacionados al tipo de accidente, fecha y hora, además de identificar entre esas variables las que se asociaron con la muerte de las víctimas. Se trata de un estudio retrospectivo utilizando datos de los Boletines de Ocurrencia de Tránsito referentes al año de 2.004 y los registros de muerte del Instituto Médico Legal. El 99,4% de las ocurrencias sucedieron en área urbana, en locales donde las condiciones de luminosidad (87,4%, condición meteorológica (80,6% y señalización (70,6% eran satisfactorias. Predominó la colisión de motocicleta con automóvil o camioneta (55,5% y las caídas de motocicleta fueron las más frecuentes (18,0%. En el tipo de impacto, el mayor porcentaje fue observado en la categoría colisión transversal (35,2%. El