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Radio Science Conference, 2007. NRSC 2007. National

Date 13-15 March 2007

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Displaying Results 1 - 25 of 78
  • Recent Progress in Reconfigurable Multi-band Antennas for Switchable and Fixed-Service Laptop Wireless Applications

    Publication Year: 2007 , Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (4107 KB) |  | HTML iconHTML  

    Reconfigurable antennas have been developed to cover various services including (GSM/DCS/UMTS/IMT-2000/WLAN). These potential services cover seven different frequency bands (800 MHz, 900 MHz, 1.8 GHz, 2.1 GHz, 2.4 GHz WLAN, and 5.2 GHz frequency bands)-- and more to come. Developed antennas are compact and should have low profiles especially for laptop implementation. Previously developed antennas (by our group) included a mini-maze, and a mini-nested antenna structures and were reconfigured using MEMS, Here, we will focus on a recently developed one; a twin-folded dipole structure. It utilizes two-branches, and each branch has more than one-resonance. The twin dipole antennas are switchable to provide wider range of operating frequencies, i.e. services. The embedded switches, however, are strategically located next to the ground plane to ease their implementation, and reduce parasitics. The implemented design is described here in detail, and is aimed at simultaneously providing fixed services like Bluetooth at 2.4 GHz, and switchable services (like GSM or PCS for example) at all other frequencies. View full abstract»

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  • Compact broadband microstrip patch antennas

    Publication Year: 2007 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (217 KB) |  | HTML iconHTML  

    We introduce microstrip patch antennas of simple shapes which can exhibit broadband operation and still enjoy relatively compact size. The circular and rectangular patches are considered when shorted to the ground plane via one or two shorting pins. The antenna is analyzed by finding the cavity modes of the structure in terms of their resonant frequencies and field distributions. Depending on the modes excited by the feeder, the patch antenna can operate as a compact antenna, as a broadband or multiband antenna. It is indicated that the suggested patch configuration can also operate as electronically tunable antenna. The theory presented here leads to universal curves for the resonant frequencies of the dominant cavity modes. The theory is supported by simulation results as well as experimental work. View full abstract»

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  • Design and Modeling of a Linear Array of Longitudinal Slots on Substrate Integrated Waveguide

    Publication Year: 2007 , Page(s): 1 - 19
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (13656 KB) |  | HTML iconHTML  

    In SIW structures, side walls are substituted by metal vias and plated holes. In this paper, we present a SIW slot array antenna, which is fed by a corporate type of microstrip power divider. The slot array and the feeding network can be fabricated on a single substrate. As a result, not only the size, weight and cost of the waveguide slot array antennas are reduced, but also the manufacturing repeatability and reliability are enhanced. Meanwhile the gain and efficiency of those antennas have only a little depression because of the dielectric loss. View full abstract»

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  • Advances in Microwave & Millimeter-wave Integrated Circuits

    Publication Year: 2007 , Page(s): 1 - 8
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (660 KB) |  | HTML iconHTML  

    This tutorial paper reports on the state-of-the-art of Monolithic Microwave Integrated Circuits (MMIC) technology. The paper gives an overview of available MMIC semiconductor materials, devices, processes and outlines the steps of a typical MMIC manufacturing process followed by a description of the different technologies used in MMIC assembly and packaging. MMIC design guidelines regarding performance and cost are also presented. A recent literature survey of MMICs used for wireless, microwave and millimeter-wave applications is shown to emphasize the merits of different MMlC technologies. Several examples of novel devices and design techniques are presented and the paper concludes with future trends in this field. View full abstract»

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  • Fast Block-Size Selection Using Residual Texture for VC-1

    Publication Year: 2007 , Page(s): 1 - 7
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (217 KB) |  | HTML iconHTML  

    The SMPTE Standard 421M, commonly known as VC-1, is a slate-of-the-art video compression format that provides highly competitive video quality, from very low through very high bit rates, at a reasonable computational complexity. VC-1 has many differences, one of which is adaptive block size transforms, from previous standards such as MPEG-2 and H.264/AVC. In this paper, we propose an algorithm that is aimed to speed up the choice of the appropriate block size in inter-frame coding. Instead of using the data from the image, we look at data after the residual texture has been calculated. The residual texture of each block is small and uniform, allowing for simplified calculations and faster block choices. Motion estimation is the first step in the process; this is followed by partitioning the residual data. Then we calculate the residual texture, and make a choice of block size using the constraints set forth. The algorithm speeds up block size selection without harming the compression ratio. View full abstract»

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  • Performance Enhancement of the Multi-Modulus Algorithm Based Adaptive Antenna Arrays Using Additional Constraints

    Publication Year: 2007 , Page(s): 1 - 8
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (330 KB) |  | HTML iconHTML  

    The linearly constrained minimum variance (LCMV) algorithm fails to capture the signal if coherent copies (multipath signals) impinge on the array at the same time with the signal. The constant modulus algorithm (CMA) and the multi-modulus algorithm (MMA) techniques solved this problem with the disadvantage of more complicated behavior and the violation of some constraints about null directions staled by the initial weights. This is the main point of interest of the new algorithms proposed in this paper. The proposed algorithms in this paper, namely, the linearly constrained CMA (LCCMA) and linearly constrained MMA (LCMMA) solved this problem and arc able to hold the initial constraints about deep nulls until the adaptation is finished. This property has been successfully used to improve the performance of the MMA algorithm to capture very high signal constellations in multipath and interference environment without having to use the more complicated generalized MMA (GMMA). View full abstract»

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  • Performance Evaluation of Separated Aperture Sensor GPR System for Land Mine Detection

    Publication Year: 2007 , Page(s): 1 - 9
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (367 KB) |  | HTML iconHTML  

    In this paper, the performance of the separated-aperture sensor working as ground- penetrating radar (GPR) is assessed over the operating frequency band. The capability of the separated-aperture sensor to detect buried targets is examined by evaluating and comparing the electromagnetic coupling between the transmitting and receiving antennas in two cases: (i) when the system is placed over an empty ground and (ii) when it is placed over a ground inside which a practical target is buried at the proper depth. The finite-difference time-domain (FDTD) method is used for electromagnetic simulation and the results concerning the coupling between the transmitting and receiving antennas are presented considering various practical parameters such as the operating frequency, the electric properties of the ground soil and the buried target, and the depth at which the target is buried under the ground surface, it is shown that target detectability using the separated-aperture sensor is strongly dependent on all of the above parameters. View full abstract»

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  • 3-D Full Wave Analysis using Spectral Domain Method of Moments for a Ferrite Cross-Patch Antenna

    Publication Year: 2007 , Page(s): 1 - 8
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (4696 KB) |  | HTML iconHTML  

    This paper describes the 3D analysis using spectral domain Method of Moments, MoM, of cross - patch antennas on ferrite substrates and compares its radar cross section (RCS) with respect to the full - patch antenna. The direction of the dc magnetization of the ferrite is assumed arbitrarily in thetas and phi. The Greens function and the excitation vector are formulated in a closed form using the transmission matrix approach. The linearly-varying basis function is used. In general, we notice that the first resonance is almost at the same frequency for both patches, the cross and the full. The cross patch excites less number of modes than the case of full patch. The RCS level is reduced. This reduction might be due to the less number of modes and/or the smaller physical area for the cross-patch element. View full abstract»

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  • Intercell Interference Reduction by the Use of Chebyshev Circular Antenna Arrays with Beam Steering

    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (395 KB) |  | HTML iconHTML  

    Advanced antenna arrays at the base stations are one of the key techniques to reduce interference in WCDMA cellular systems. This paper presents the use of the beam steering method with circular arrays along with Chebyshev current distributions in order to reduce the value of the ratio of intercell interference to received intracell power in WCDMA cellular systems. The intercell to intracell interference ratio of the beam steering case with the proposed arrays is compared to that of the conventional omnidirectional case. The obtained results demonstrate a notable superiority of the proposed antenna arrays. View full abstract»

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  • A Modified E-Shaped Microstrip Antenna for Ultra Wideband Wireless Systems

    Publication Year: 2007 , Page(s): 1 - 6
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (251 KB) |  | HTML iconHTML  

    In this paper, the analysis of a modified E-shaped patch antenna is presented. The purpose of the modification over the original E-shaped structure is to accommodate the operating frequency band and signal bandwidth requirements of the Ultra Wideband (UWB) wireless system. Simulation results show that the modified R-shaped has fulfill the frequency band and signal bandwidth requirements of the UWB system. A resonance frequency of 3.5 GHz and signal bandwidth of 29.3% is achieved for the presented structure. The analysis of the proposed antenna has been done using the finite difference time domain (FDTD) with Perfect Matched layer (PML) approach. Results have been compared with published data and good agreements are found. View full abstract»

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  • An Efficient Computational Approach in the Matrix Pencil Method to Find One Dimensional and Two Dimensional Direction of Arrival

    Publication Year: 2007 , Page(s): 1 - 8
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (283 KB) |  | HTML iconHTML  

    The problem of estimating the direction of arrival (DoA) of the various sources impinging on a phased array has received considerable attention, in many fields including radar, sonar, radio astronomy and mobile communications. A very efficient computational procedure in the Matrix Pencil (MP) method to compute the one dimensional direction of arrival (1D-DoA) of the signals impinging on the linear array operating in the presence of undesired electromagnetic effects is given in this paper. This procedure reduces the complexity of the computation significantly by using a unitary matrix transformation. This technique is applied directly to the corrected data by applying the transformation matrix to compensate the undesired electromagnetic effects such as mutual coupling between the antenna elements without forming a covariance matrix. A unitary transform can convert the complex matrix to a real matrix along with their eigenvectors and thereby reducing the computational cost at least by a factor of four. Finally, a new technique based on the above procedure is proposed and applied to a planar array to find the two dimensional direction of arrival (2D-DoA). Limited numerical examples are presented to illustrate the performance and accuracy of the proposed techniques. View full abstract»

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  • Design of a Compact UWB Planar Antenna with Band-Notch Characterization

    Publication Year: 2007 , Page(s): 1 - 8
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (399 KB) |  | HTML iconHTML  

    A compact ultra-wideband (UWB) antenna with band-notch characteristic of size 28 mm times 29 mm is proposed. This antenna is designed to cover the Federal Communication Commission (FCC) bandwidth for UWB applications (3.1-10.6 GHz) and have a notch- filtering at the IEEE 802.1 Ia frequency band (5.15-5.825 GHz). This notch-filter effect is obtained by introducing a resonant U-shaped slot at this frequency. The design parameters and the performance of the proposed antenna are analyzed by using different techniques to assure the validity of the simulated results. Comparison between measurements and simulation is also presented. View full abstract»

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  • A Hybrid Finite Difference Frequency Domain and Particle Swarm Optimization Techniques for Forward and Inverse Electromagnetic Scattering Problems

    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (302 KB) |  | HTML iconHTML  

    Finite-difference frequency domain (FDFD) is formulated to calculate the scattered field from superquadric dielectric cylinder. A hybrid technique from FDFD and particle swarm optimization technique (PSO) is used to reconstruct both the shape and the relative permittivity of a homogenous dielectric cylinder. The dielectric constants of materials in the solid, liquid, or in the paste forms are considered. View full abstract»

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  • One-Dimensional Electromagnetic Inversion Using Particle Swarm Optimization

    Publication Year: 2007 , Page(s): 1 - 8
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (335 KB) |  | HTML iconHTML  

    An electromagnetic inversion method for the reconstruction of the permittivity profile of a multilayered medium is proposed. The inversion is based on global optimization of a fitness function using particle swarm optimization algorithm. The fitness function describes the error between observed data and synthetic data obtained from solving the forward problem. A gradient based method is used as a second step to obtain better accuracy of the solution with less computation time. Two different reconstructing models for the permittivity profiles are used. The method is applied to dielectric slabs with different permittivity profiles. Random noise is added to the data to study its effect. The reconstruction process is performed in each case with satisfactory results. View full abstract»

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  • LMS Beamforming Using Pre and Post-FFT Processing for OFDM Communication Systems

    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (226 KB) |  | HTML iconHTML  

    The adaptive array antenna is combined with OFDM "orthogonal frequency division multiplexing" as multicarrier technique to combat the flat and frequency selective fading effects at high speed wireless communication. In this paper an optimum weight sets beat informer at time and frequency domain were obtained based on LMS algorithm. Different aspects of these systems were investigated such as different values of delay spread, angle of arrival of interfering sources and number of array elements. View full abstract»

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  • Design and Analysis of Wideband Antenna with Application to Ground Penetrating Radar System

    Publication Year: 2007 , Page(s): 1 - 8
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (359 KB) |  | HTML iconHTML  

    In this paper, a wide band antenna is proposed for ground-penetrating radar (GPR) system. This antenna consists of dipole antenna housed in a rectangular conducting reflector whose inner walls are coated by an absorbing material. The coating is composed of a number of layers with a conductivity profile designed to achieve the minimum voltage standing wave ratio (VSWR) of the dipole antenna over the frequency band of operation. The antenna impedance and VSWR are calculated using the finite-difference time-domain (FDTD) method. The antenna impedance and VSWR are presented over a wide-band of frequency. The capability of buried target detection by the proposed antenna is examined by investigating the coupling between the transmitting and receiving antennas in the presence and absence of buried targets. The operating bandwidth of the antenna is shown to be about 50%. The effect of the ground soil on the antenna characteristics is studied when the GPR system is placed at different heights above such a soil. The GPR system with the proposed antenna is shown to be capable of detecting the existence of buried targets. View full abstract»

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  • Subband Adaptive Array for Faded Signals in Multipath Environment

    Publication Year: 2007 , Page(s): 1 - 8
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (318 KB) |  | HTML iconHTML  

    Subband adaptive arrays (SBAA) have been proposed as an effective mean replacing tapped delay line adaptive array antennas (TDLAA) to mitigate inter-symbol interference (ISI), caused by multipath propagation, and co-channel interference (CCI), caused by frequency reuse in neighbor cells. The subband processing is based on the decomposition of the frequency band of the received signal into a number of subbands, which are analyzed separately for improvement of the signal-to-interfere-ce-plus-noise ratio (SINR). These bands are then recombined to get the output signal with maximum SINR. In this paper, we study the performance of SBAA for faded signals in presence of interference and multipath environment. View full abstract»

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  • Optimization of an Antipodal Vivaldi Antenna using Synthesis Neural Networks and a Novel Genetic Algorithms Approach

    Publication Year: 2007 , Page(s): 1 - 7
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (287 KB) |  | HTML iconHTML  

    Two global optimization techniques, applicable for the optimization of several antennas and microwave components, are presented. The two techniques are explained together with a sample application, which is the optimization of an antipodal Vivaldi antenna. The first technique was found useful in optimizing the design aspects whose physical behavior is known, whereas the second was better for optimizing the design aspects for which the response behavior is unknown, but an adequate performance metric can be defined. The two methods are compared; the limitations and advantages of each method arc presented together with some other optimization techniques. View full abstract»

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  • Wideband Circular Microstrip Antenna For Wireless Communication Systems

    Publication Year: 2007 , Page(s): 1 - 8
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (291 KB) |  | HTML iconHTML  

    In this paper several configurations of circular microstrip antenna fed by coaxial lines are designed to achieve wide bandwidth. An extra dielectric substrate added on top of a conventional circular patch and an air gap added are also designed. A large bandwidth was achieved by all those designs. The analysis was carried out by using the ready made software HFSS. View full abstract»

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  • Analysis of Stacked Rectangular Microstrip Antenna

    Publication Year: 2007 , Page(s): 1 - 11
    Cited by:  Patents (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (856 KB) |  | HTML iconHTML  

    A stacked microstrip antenna with C-type feed is designed in order to enhance the bandwidth. The effect of the various parameters, such as the rotation feed angle (thetas), the variations of relative permittivity of parasitic patch (epsivr2), the distance of the feed point from the center (r), and the separation between two stacked patches (h2), have been discussed. Some designs give a good return loss under -40 dB and wide VSWR bandwidth, such as case#2 with epsivr2=4.26, case#4 with r=6.2 mm, case#5 with h2=6.8 mm, case#1,and case#2 with h2=8.2 mm. The simulated data are obtained using the IE3D simulator with method of moments (MoM) commercial code. An infinite ground plane has been considered for simulations; however, and due to a software constraint, substrate dimensions are infinite. View full abstract»

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  • Microstrip Antenna with Shorting Pins As A sensor for Landmines Detection

    Publication Year: 2007 , Page(s): 1 - 8
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (322 KB) |  | HTML iconHTML  

    A proposed sensor for landmines detection consists of two parallel microstrip antennas placed on same ground plane with shorting pins between the patch and the ground plane has been investigated. The microstrip patch array with shorting pins has the advantage of a low coupling and size reduction compared with classic arrays. The finite-difference time-domain (FDTD) is used to simulate the senor for landmines detection. View full abstract»

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  • Empirical Formulation and Design of a Broadband Enhanced E-Patch Antenna

    Publication Year: 2007 , Page(s): 1 - 9
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (493 KB) |  | HTML iconHTML  

    A broadband probe-fed microstrip antenna with E-shaped patch on a single-layer air substrate is investigated. Bandwidth enhancement of the antenna is achieved by inserting two parallel slots into its radiating patch. The effects of the following design parameters: the slot length (Ls), width (Ws, position (Ps), the substrate height (h), and the position of excitation point (Xf, Yf) are analyzed, followed by an optimization procedure to select the optimum values for broad-band operation. The design parameters are empirically formulated as a function of the center frequency. Empirical equations are validated by simulation. Finally, a 41% Enhanced E-shaped patch antenna for modern wireless communications (PCS, DCS, UMTS, WLAN 802.11 b/g. and Bluetooth) is designed, simulated, fabricated, and measured. A comparison between simulated and measured results is also presented. View full abstract»

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  • A New Combined Scheme for Fast PN Code Acquisition

    Publication Year: 2007 , Page(s): 1 - 7
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (186 KB) |  | HTML iconHTML  

    This paper presents a new combined acquisition scheme, known as "fast serial search sequential estimation" which is applicable to the direct sequence spread spectrum systems with a long period pseudo noise sequences. The proposed scheme is a combination of two basic acquisition schemes which are the serial search acquisition scheme and the rapid acquisition by sequential estimation (RASE) scheme. The proposed scheme gets the advantages of both serial search and RASE schemes, while overcomes their drawbacks. For example, the mean acquisition time of the proposed scheme is reduced 100 times compared with the conventional serial search scheme for PN sequence with period of 215-1. View full abstract»

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  • A New Symmetric Key Quantum Cryptographic Algorithm

    Publication Year: 2007 , Page(s): 1 - 13
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (485 KB) |  | HTML iconHTML  

    Based on the principles of both classical and quantum computation primitives, a new symmetric key quantum cryptographic algorithm is proposed. This algorithm can be used to encrypt classical binary messages as well as quantum information. Encryption and decryption are implemented by the aid of classical and quantum computation which can be realized by suitable technology. Because each encryption process is under the control of the key which is dynamically and recursively changed through each round in both encryption and decryption and the final ciphertext states are non-orthogonal, the eavesdropper can not acquire fixed ciphertext without the keys so the eavesdropping attack is invalid, which is guaranteed with the no-cloning theory in quantum mechanics. Similarly, the non-orthogonality of the ciphertext renders the Trojan horse attack strategy impossible. Also the algorithm applies a pseudo random process from stage to stage. This pseudo randomness hinders the ability of Eve to attack such a cryptographic scheme. View full abstract»

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  • A New Approach for Key Controlled Agreement

    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (299 KB) |  | HTML iconHTML  

    Diffie-Hellman key agreement protocol is the first and most famous protocol, but it has many flaws and drawbacks. Therefore, this paper proposes a new two-pass authenticated key agreement protocol (AK) provides assurance, randomization, and controlling of the key reception, this protocol is based on Dijfie-Hellman problem and also follows - up T. Matumoto, Y. Takashima and H. Imai two-pass Key Agreement Protocols. View full abstract»

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