Mutual Radiation Research Articles

The Mutual Impedance Analysis of a Broadband Dense Plane Array

Due to the mutual radiation impedance may influence acoustics performance of a broadband dense plane array seriously, the expression of mutual radiation impedance among the transducers is developed according to the definition of mutual radiation impedance based on BEM（Boundary Element Method）. BEM model is established for acoustic radiation of a broadband dense plane array with nine elements. Sound pressure distribution of the nine-element array is solved using SYSNOISE software. And mutual radiation impedances are calculated on the condition of knowing surface normal velocity. Acoustic performance of the nine-element array is analysed through mutual radiation impedance. The influence of mutual impedance on acoustics performance for nine-element array is verified by comparing with measured curve of transducer conductance. The results show that it is successful to calculate mutual impedance of the array and predict acoustics performance using BEM.

Development of adsorbent from Teflon waste by radiation induced grafting: Equilibrium and kinetic adsorption of dyes

Mutual radiation grafting technique was employed to graft polyacrylic acid (PAA) onto Polytetrafluoroethylene (Teflon) scrap using high energy gamma radiation. Polyacrylic acid- g-Teflon (PAA- g-Teflon) adsorbent was characterized by grafting extent measurement, FTIR spectroscopy, SEM and wet ability & surface energy analysis. The PAA- g-Teflon adsorbent was studied for dye adsorption from aqueous solution of basic dyes, namely, Basic red 29 (BR29) and Basic yellow 11 (BY11). The equilibrium adsorption data were analyzed by Langmuir and Freundlich adsorption isotherm models, whereas, adsorption kinetics was analyzed using pseudo-first order, pseudo-second order and intra-particle diffusion kinetic models. Equilibrium adsorption of BR29 was better explained by Langmuir adsorption model, while that of BY11 by Freundlich adsorption model. The adsorption capacity for BY11 was more than for BR29. Separation factor ( R L) was found to be in the range 0 < R L < 1, indicating favorable adsorption of dyes. Higher coefficient of determination ( r 2 > 0.99) and better agreement between the q e,cal and q e,exp values suggested that pseudo-second order kinetic model better represents the kinetic adsorption data. The non-linearity obtained for intra-particle diffusion plot indicated, more than one process is involved in the adsorption of basic dyes. The desorption studies showed that ∼95% of the adsorbed dye could be eluted in suitable eluent.

Functionalization of cotton fabrics by radiation induced grafting of quaternary salt to impart antibacterial property

High energy gamma radiation has been used to covalently link polymer chains of a quaternary ammonium salt containing monomer, viz. [2-(Acryloyloxyethyl)]trimethylammonium chloride (AETC) to cotton fabric by mutual radiation grafting using 2-hydroxyethyl methacrylate (2-HEMA) monomer as the grafting facilitator. Grafting yield was found to increase with the radiation dose and monomer concentration. The grafted samples have been characterized for water uptake, surface morphology and thermal stability and for their antibacterial efficacy against various bacteria and were found to possess significant antibacterial activity particularly against gram-positive bacteria.

Modeling time delay in clusters of interacting bubbles.

Modeling the dynamics of large clusters of interacting bubbles requires that the effects of fluid compressibility be taken into account. Compressibility manifests itself through radiation damping and bubble-bubble interactions due to time delays associated with the finite sound speed. The time delays convert the dynamical equations for interacting bubbles in an incompressible fluid from a system of nonlinear ordinary differential equations to one of delay differential equations (DDEs). Special care must be taken when integrating DDEs numerically to maintain acceptable bounds on errors. The dynamical equations determined to be most suitable for solving as DDEs were obtained using Hamiltonian mechanics [Ilinskii et al., J. Acoust. Soc. Am. 121, 786 (2007)]. These first-order differential equations were augmented to include time delays in the bubble interaction terms and then solved numerically using a sixth-order Runge–Kutta method with a continuous interpolant (DDE_SOLVER). The same equations were also solved without the time delays but with correction terms that account for mutual radiation damping. Comparison of the results reveals the importance of time delay in bubble-bubble interactions as a function of the size and density of a bubble cluster. [Work supported by the ARL:UT McKinney Fellowship in Acoustics and NIH Grant No. DK070618.]

Teflon scrap based cation exchanger by radiation grafting: Process parameter standardization and characterization

AbstractHigh‐energy gamma radiation from 60Co‐gamma radiation source has been used to covalently link acrylic acid to teflon by mutual radiation grafting technique. Effect of various experimental parameters viz, dose, dose rate, monomer concentration, backbone thickness effect of additives on grafting extent was investigated in order to optimize the conditions for grafting acrylic acid onto teflon to optimum levels. The grafting extent decreased with increasing dose rate and thickness of the substrate while it increased with concentration of acrylic acid and optimum concentration of Mohr's salt. The grafted product was characterized for grafting yield, surface morphology, bulk morphology, and crystallinity change. The SEM studies indicate significant difference in bulk and interface due to change in thickness of the teflon backbone. Dynamic contact angle measurement studies of the grafted and radiation treated teflon showed that initial grafting as well as radiation treatment of teflon enhances its hydrophilicity. © 2011 American Institute of Chemical Engineers Environ Prog, 2012

Influence of physical parameters on mutual polymer grafting by electron beam irradiation

Grafting is a good method for modifying a polymer matrix and radiation induced grafting is an advantageous technique for chemical grafting because it does not require an initiator. In this work, mutual radiation grafting was performed and physical parameters like vacuum, pressure of air or inert gas and temperature were studied to verify their influences on styrene grafting onto hydrocarbon and fluorinated polymers. We observed that vacuum and temperature are determinant parameters to be considered in mutual radiation grafting besides the backbone polymer, monomer molecules and solvent. The optimization of these parameters for a specific polymer/monomer system contributes to a good performance and allows mutual radiation grafting to be an attractive technique even if it is performed in commercial accelerators.

Analysis of near field sound radiation from a resonant unbaffled plate using simplified analytical models

Near field radiation behavior of an unbaffled square plate with free edges, which is excited by a harmonic force at its midpoint, is analytically, computationally and experimentally studied. Emphasis is on the applicability of simplified analytical models to predict the near field sound pressures and spatially-averaged surface and acoustic intensities. First, the plate is computationally discretized into equal segments that are replaced by simple, phase-correlated discrete acoustic sources. Piston radiator models (with and without mutual radiation impedance terms) as well as pulsating sphere models are employed to exhibit the contribution of mutual impedance terms. The near field pressure and spatially-averaged intensity radiated from phase-correlated discrete sources are calculated based on the premise that their individual phases are obtained from the plate (surface) vibration measurements. The importance of mutual impedance terms on the near field radiation is highlighted. Second, the two-microphone acoustic intensity and the surface intensity techniques are employed to determine the spatially-averaged intensity spectra, like analytical models. Results are examined on both narrow and 1/3 octave band bases up to 1600 Hz covering radiation from several plate vibration modes. Finally, an indirect boundary element model is used to predict spatially-averaged intensity spectra, as well as to simulate the two-microphone method given surface vibration data. All predictions are compared with analogous measurements. Discrepancies between theory and experiments (and even between two intensity measurements) are discussed along with possible sources of error.

Ground Test Investigation of Temperature Distribution in Four Parallel High-Altitude Engines

This paper describes a ground test investigation of temperature distribution in the vacuum cabin of an engine group with four parallel nozzles when subjected to the high-altitude conditions encountered in space. A new scheme was devised to simulate and evaluate the influence of radiative heat transfer on the wall temperature distribution of high-altitude engines in the vacuum cabin. Nozzles used in the ground test were geometrically and physically analogous to the actual ones used in space. Electric heating nozzles, instead of the actual ones, were used in the test unit. Characteristics of the wall temperature distribution were obtained by measuring the wall temperatures of the four- and two-parallel-nozzle configurations. It was shown from the testing data that, due to the mutual radiation among high-temperature nozzles with small gaps, the maximum circumferential temperature rise, A T max , was less than 30K at the throat with high temperature, whereas A T max was less than 250K at the exit with low temperature. Thus, the temperature rise of the whole thrust chamber did not affect the normal working of the set of engines. Comparing the data from numerical simulation, it is indicated that the results from the electric heating test in a vacuum cabin are conservative and reliable.

Interaction of polyoxometalate Mo132 with poly(vinyl alcohol)

Some aspects of the interaction of (NH4)42[Mo 72 VI Mo 60 V O372(H3CCOO)30(H2O)72] · 30H3CCOONH4 · 250H2O (polyoxometalate Mo132) with a water-soluble nonionic polymer (poly(vinyl alcohol) or related poly(vinylpyrrolidone)) were studied in aqueous solutions and in films. A set of methods was used: spectrophotometry, EPR spectroscopy, visual microscopy, X-ray powder diffraction, scanning probe microscopy, and potentiometry. The complex-formation features of the system were revealed. The miscibility of the components and their influence on crystallization phenomena were considered. The effect of UV and X-rays on poly(vinyl alcohol) + polyoxometalate films was studied. Poly(vinyl alcohol) stabilizes the polymer. Mutual radiation and thermal stabilization of the polymer and polyoxometalate was discovered. The utility of ion-sensitive electrodes for Mo132 determination in solution was demonstrated.

Synthesis of antibacterial cotton fabric by radiation-induced grafting of [2-(Methacryloyloxy)ethyl]trimethylammonium chloride (MAETC) onto cotton

Gamma radiation has been used to covalently link polymer chains of [2-(Methacryloyloxy)ethyl]trimethylammonium chloride (MAETC) to cotton fabric by mutual radiation grafting. The grafted samples have been characterized for water uptake, surface morphology and thermal stability. Grafting extent was found to increase with the dose and monomer concentration. However high dose rate, O 2, inorganic salts and alcohols suppressed grafting. Radiation polymerized poly(MAETC) and MAETC-g-cotton samples were tested for their antibacterial efficacy against various bacteria and were found to possess significant antibacterial activity.

Grooves-Assisted Surface Wave Modulation in Two-Slot Array for Mutual Coupling Reduction and Gain Enhancement

In this letter, a method of reducing mutual coupling between the rectangular waveguide end-slot array and improving its gain is presented. In this antenna, the novel surface corrugated structure is symmetrically loaded at both sides of each slot element. Different from the suppression of surface wave in the choke grooves, the proposed corrugated structure would modulate surface wave propagation, resulting in the variation of surface energy strength distribution. The effectiveness of the proposed surface grooves is verified by numerical simulations and experimental testing. It is found that the mutual coupling level between two slot elements is observably decreased to be less than -40 dB after employment of surface grooves, and the gain of two slots array is also greatly enhanced by 4 dB. Furthermore, the influences of groove parameters on the mutual coupling level and radiation performance are discussed, respectively, and physical mechanism of this corrugated structure is investigated and compared to that of choke grooves as well.

Physicochemical and electrochemical characterization of battery separator prepared by radiation induced grafting of acrylic acid onto microporous polypropylene membranes

Mutual radiation grafting technique was used to graft acrylic acid on micrometer thick micro-porous polypropy- lene membrane using high-energy gamma radiation. Grafting could not be achieved in aqueous acrylic acid solution. The presence of Mohr's salt effectively retarded the homopolymerization of acrylic acid but did not lead to grafting enhance- ment. Mohr's salt in presence of acids was found to be effective in enhancing the grafting yield. Contact angle measurement studies of the grafted and radiation treated polypropylene showed that initial grafting as well as radiation treatment of poly(propylene) in aqueous medium and in presence of Mohr's salt enhances its affinity towards the grafting solution. The enhancement in the polar component of surface energy of treated polypropylene membrane is the primary cause of grafting enhancement. The membranes grafted to an extent of ~20% were found to perform comparably with the battery separator presently being used by battery industry.

Variation of Mutual Radiation Impedance with Calculation Area in a Cylindrical Array

Variation of Mutual Radiation Impedance with Calculation Area in a Cylindrical Array J. S. Kim Multimedia Engineering, Tongmyong University, Busan 608-711 M. J. Kim and K. L. Ha Department of Physics, Pukyong National University, Busan 608-737 Heeseon Seo and Cheeyoung Joh 6th R&D Institute, Agency for Defense Development, Jinhae 645-600 (Received 23 April 2008) For e ciency in the analysis of the acoustic elements arrayed on a cylindrical ba e, the total mutual radiation impedance variation with the calculation range and ka was investigated. The total mutual radiation resistance and reactance were calculated for the range of ka from 8 to 50 and for the range of area ratios from 2 % to 100 %. Using this result, we will determine an appropriate calculation range for the required accuracy. This study will provide essential data for the design of a cylindrical transducer array. PACS numbers: 43.58.Bh, 43.30.Jx, 43.30.Yj

Radiation grafting of acrylonitrile on ethylene-propylene diene terpolymer rubber: Optimization of grafting parameters and oil resistance properties

Radiation induced grafting of acrylonitrile (ACN) on ethylene-propene diene terpolymer (EPDM) rubber film was investigated by mutual radiation grafting technique. Effect of experimental variables viz. radiation dose, dose rate, type of solvent and monomer content on extent of grafting was studied. From the kinetic studies a mathematical relation Rgα[M]0.7D0.68 showing non-linear relationship for rate of grafting with monomer concentration and dose was deduced. The grafted samples showed increased hardness and oil resistance.

Acoustic field calculation for a compact barrel‐stave flextensional transducer array

The boundary element method together with the finite element method is used to calculate the radiated acoustic field of a compact array of barrel‐stave flextensional transducers. At first, the surface vibration displacement distribution of one barrel‐stave transducer is obtained by the finite element method using the commercial software ANSYS. The calculation results are then imported into the boundary element calculation software SYSNOISE. At the frequency of 1400Hz, the radiated acoustic field and radiation impedance are calculated by the boundary element method for a planar array which is composed of three identical barrel‐stave flextensional transducers uniformly distributed on a circle with spacing much less than half wavelength. The calculation results show that the mutual interactions among elements are significant for the compact array. The mutual radiation resistance between two transducers is close to the self‐radiation resistance of the transducers. And the transmitting source level of the 3‐element array is 8.7dB higher than that of one transducer if the surface vibration velocities of the transducers in the array are the same as that of one transducer. The proposed technique can be used to predict the performance of a transmitting transducer array at the stage of preliminary design.

Finite element and boundary element modeling of multimodal arrays

Modern active sonar arrays exhibit the following characteristics: low operating frequency, large number of transducers, small transducer spacing compared to wavelength, and in some cases, multimodal transducers. This results in strong, complex acoustic interaction phenomena which can involve both a large number of array elements and multiple transducer modes. To predict the performance of such arrays, this paper presents a modeling approach which is both accurate and computationally economical. First, the generic equivalent circuit for an array of multimodal transducers is described. The field of application of such a model, the definition of the parameters, and the characteristics which can be calculated from it are provided. Second, the computation of the equivalent circuit parameters is performed using commercial finite element and boundary element codes. Specifically, a method is described to compute the mechanical, electrical, self and mutual radiation parameters of the various transducer modes. Finally, the methodology is applied to a 12 element volumetric array of flextensional transducers, with both λ/2 and λ/4 spacings.

Measurements of mutual radiation impedance between baffled cylindrical shell transducers

The mutual radiation impedances between two baffled cylindrical shell transducers, made of PZT-4 piezoelectric rings with one half of the cylindrical surface covered by a compliant baffle, were determined in experiments as a function of separation distance using an experimental technique recently described [B. Aronov, J. Acoust. Soc. Am. 119, 3822-3830 (2006)]. Two baffled cylindrical shell transducers were connected electrically in parallel and the input electrical admittance was measured at different separations when the two transducers were operated in phase and then 180 degrees out-of-phase in both the coaxial and horizontal (side-by-side) alignments. The mutual radiation impedances were then computed using an electrical equivalent circuit to determine the significance of interaction for cylindrical elements in these array geometries.

Modal-Expansion Analysis of Multiple Monopole Antennas

The modal-expansion method is employed to analyze an array of multiple monopole antennas. A perfectly conducting plate is introduced at the top of the monopole array to facilitate the modal-expansion analysis. Expansion coefficients in the field expressions are found by enforcing continuity conditions of the tangential field components across the regional surfaces. Cylindrical function's addition theorem is employed to realize the transformation of field expressions in different coordinate systems. Numerical results for theS-parameters of a two-monopole antenna are presented and they are in good agreement with experimental ones. Also examined is the effect of the distance between two monopoles on the antenna's mutual coupling and radiation pattern. A four-monopole antenna is studied for its beam-steering capability and simulated results for its radiation properties are compared with those obtained by high frequency structure simulator (HFSS).

2-11P-63 Variation of Beam Pattern with Calculation Area of Mutual Radiation Impedance in a Cylindrical Array(Poster session 2)

2-11P-63 Variation of Beam Pattern with Calculation Area of Mutual Radiation Impedance in a Cylindrical Array(Poster session 2)

Radiation-induced grafting of acrylamide onto guar gum in aqueous medium: Synthesis and characterization of grafted polymer guar-g-acrylamide

Mutual radiation grafting technique has been applied to carry out grafting of acrylamide (AAm) onto guar gum (GG) using high-energy Co 60 γ radiation to enhance its flocculating properties for industrial effluents. The grafted product was characterized using analytical probes like elemental analysis, thermal analysis, Fourier transformed infrared (FTIR), X-ray diffraction (XRD) and scanning electron microscope (SEM). The grafting extent was observed to decrease with the dose rate and increase with the concentration of AAm. Thermo gravimetric analysis (TGA) of grafted and ungrafted samples indicated better stability of grafted product. γ and microwave radiation effect on grafted and virgin GG has also been reported.