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    Modules with finitely many submodules

    , Article Algebra Colloquium ; Volume 23, Issue 3 , 2016 , Pages 463-468 ; 10053867 (ISSN) Akbari, S ; Khalashi Ghezelahmad, S ; Yaraneri, E ; Sharif University of Technology
    World Scientific Publishing Co. Pte Ltd  2016
    Abstract
    In this paper, we study modules having only finitely many submodules over any ring which is not necessarily commutative. We try to understand how such a module decomposes as a direct sum. We justify that any module V having only finitely many submodules over any ring A is an extension of a cyclic A-module by a finite A-module. Under some assumptions on A, such as commutativity of A, we prove that an A-module V has finitely many submodules if and only if V can be written as a direct sum of a cyclic A-module having only finitely many A-submodules and a finite A-module  

    Pure-injectivity of tensor products of modules

    , Article Algebra Colloquium ; Vol. 21, issue. 1 , 2014 , pp. 151-156 ; ISSN: 10053867 Pournaki, M. R ; Torrecillas, B ; Tousi, M ; Yassemi, S ; Sharif University of Technology
    Abstract
    A classical question of Yoneda asks when the tensor product of two injective modules is injective. A complete answer to this question was given by Enochs and Jenda in 1991. In this paper the analogue question for pure-injective modules is studied  

    On the complement of the intersection graph of submodules of a module

    , Article Journal of Algebra and its Applications ; Volume 14, Issue 8 , October , 2015 ; 02194988 (ISSN) Akbari, S ; Tavallaee, H. A ; Khalashi Ghezelahmad, S ; Sharif University of Technology
    World Scientific Publishing Co. Pte Ltd  2015
    Abstract
    Let R be a ring with identity and M be a unitary left R-module. The complement of the intersection graph of submodules of M, denoted by Γ(M), is defined to be a graph whose vertices are in one-to-one correspondence with all nontrivial submodules of M and two distinct vertices are adjacent if and only if the corresponding submodules of M have zero intersection. In this paper, we consider the complement of the intersection graph of submodules of a module. We prove that, if Γ(M) is connected and Δ(Γ(M)) < ∞, then M is semisimple, where Δ(Γ(M)) is the maximum degree of Γ(M). We show that, if Γ(M) is a forest, then each component of Γ(M) is a star graph. Moreover, it is proved that, if Γ(M) is a... 

    Some results on the intersection graph of submodules of a module

    , Article Mathematica Slovaca ; Volume 67, Issue 2 , 2017 , Pages 297-304 ; 01399918 (ISSN) Akbari, S ; Tavallaee, H ; Khalashi Ghezelahmad, S ; Sharif University of Technology
    De Gruyter Open Ltd  2017
    Abstract
    Let R be a ring with identity and M be a unitary left R-module. The intersection graph of submodules of M, denoted by G(M), is defined to be a graph whose vertices are in one to one correspondence with all non-trivial submodules of M and two distinct vertices are adjacent if and only if the corresponding submodules of M have non-zero intersection. In this paper, we consider the intersection graph of submodules of a module. We determine the structure of modules whose clique numbers are finite. We show that if 1 < ω(G(M)) < ∞, then M is a direct sum of a finite module and a cyclic module, where ω(G(M)) denotes the clique number of G(M). We prove that if ω(G(M)) is not finite, then M contains... 

    Type based sign modulation for molecular communication

    , Article IWCIT 2016 - Iran Workshop on Communication and Information Theory, 3 May 2016 through 4 May 2016 ; 2016 ; 9781509019229 (ISBN) Mosayebi, R ; Gohari, A ; Mirmohseni, M ; Nasiri Kenari, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    Abstract
    One of the foremost challenges in modulation scheme for molecular communication is positivity of the transmission signal (only a positive concentration of molecules can be released in the environment). This restriction makes handling of the InterSymbol Interference (ISI) a challenge for molecular communication. In this paper, a novel modulation is proposed which introduces use of negative signals to ameliorate the transmission link performance. A precoder scheme based on the diffusion channel model is proposed and shown to have a significant improvement compared to previous modulation schemes such as CSK and MCSK  

    Per Tone equalization analysis in DMT based systems

    , Article IEEE TENCON 2004 - 2004 IEEE Region 10 Conference: Analog and Digital Techniques in Electrical Engineering, Chiang Mai, 21 November 2004 through 24 November 2004 ; Volume A , 2004 , Pages A539-A542 Rezaei, S. S. C ; Pakravan, M. R ; IEEE Region 10 ; Sharif University of Technology
    2004
    Abstract
    Time domain equalizers are used in the receiver of a discrete multitone (DMT) receiver to compensate the channel effects on the received signal. There are a lot of DMT equalization algorithms presented in the literature, but recently a novel Per Tone equalizer structure was proposed which offers some advantages over the previous traditional ones. The objective of this paper is to provide an overview of the important concepts of this technique and evaluate its initialization complexity. The performance of this technique is also compared with typical time-domain equalization algorithms in different simulation environments. © 2004IEEE  

    Discrete multitone modulation with biorthogonal filter bank

    , Article 3rd IEEE International Symposium on Signal Processing and Information Technology, ISSPIT 2003, 14 December 2003 through 17 December 2003 ; 2003 , Pages 34-37 ; 0780382927 (ISBN); 9780780382923 (ISBN) Maleki, A ; Shamsollahi, M. B ; Abdi, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2003
    Abstract
    Discrete multitone (DMT) modulation is used for the efficient transmission of data over nonideal channels. By nonideal channel, we mean that the channel with the frequency response is not flat. Also the noise is present in this kind of channel. In recent years, optimization of filter banks for the DMT systems is considered. Recent researches focused on the orthonormal filter banks have shown that the principal component filter bank (PCFB) is optimal for this application. We focus on one class of biorthogonal filter banks and find the optimum solution for this class. We also have shown that the performance of this structure is better than the optimum orthonormal filter bank. © 2003 IEEE  

    Deformation of outer representations of Galois group

    , Article Iranian Journal of Mathematical Sciences and Informatics ; Volume 6, Issue 1 , 2011 , Pages 35-52 ; 17354463 (ISSN) Rastegar, A ; Sharif University of Technology
    2011
    Abstract
    To a hyperbolic smooth curve defined over a number-field one naturally associates "ananabelian" representation of the absolute Galois group of the base field landing in outer automorphism group of the algebraic fundamental group. In this paper, we introduce several deformation problems for Lie-algebra versions of the above representation and show that, this way we get a richer structure than those coming from deformations of "abelian" Galois representations induced by the Tate module of associated Jacobian variety. We develop an arithmetic deformation theory of graded Lie algebras with finite dimensional graded components to serve our purpose  

    Mass measurement using an intensity-modulated optical fiber sensor

    , Article Optics and Lasers in Engineering ; Volume 38, Issue 6 , 2002 , Pages 537-548 ; 01438166 (ISSN) Golnabi, H ; Sharif University of Technology
    2002
    Abstract
    Design and operation of an opto-mechanical sensor for mass measurements is reported. This device uses a pair of optical fibers and a reflecting coated lens. The light intensity modulation is based on the relative motion of the lens due to a given mass with respect to the optical fibers. The modulated intensity because of the weighing mass has been measured by using a digital voltmeter. A full-range sensitivity of about 11.5 mV/g for a dynamic range of 80 g is obtained. A mass resolution of better than 0.25 g has been measured with this device. The measured output response is checked against the expected theoretical one and a general agreement observed. A comparison with similar experimental... 

    Design of an optical fiber sensor for linear thermal expansion measurement

    , Article Optics and Laser Technology ; Volume 34, Issue 5 , 2002 , Pages 389-394 ; 00303992 (ISSN) Golnabi, H ; Sharif University of Technology
    2002
    Abstract
    Design and operation of an optical fiber device for temperature sensing and thermal expansion measurement are reported. The modulated intensity has been measured by using a pair of 450 μm core fiber, one acting as the source and the other one as receiving fiber. In this design, the light intensity modulation is based on the relative motion of the optical fibers and a reflective coated lens. By using displacement calibration data for this sensor, the linear thermal expansion of the aluminum rod is determined. This sensor shows an average sensitivity of about 11.3 mV/°C for temperature detection and 7 μm/°C for thermal expansion detection. Device resolution for a linear expansion measurement... 

    Design and analysis of the integrated plasma wave micro-optical modulator/switch

    , Article Fiber and Integrated Optics ; Volume 21, Issue 3 , 2002 , Pages 173-191 ; 01468030 (ISSN) Khorasani, S ; Nojeh, A ; Rashidian, B ; Sharif University of Technology
    2002
    Abstract
    Feasibility of a new integrated amplitude modulator/switch operating up to the visible spectrum, based on the absorption of light due to the linear interaction of the incident laser and a two-dimensional plasma layer is demonstrated. Plasma layers are generated via the Muller effect at the waveguide's interfaces. A plasma wave is excited in the two-dimensional gas when it is illuminated by electromagnetic radiation. Thus, due to the energy transfer from the electromagnetic wave to the plasma wave, the output light intensity can be controlled. The device is capable of amplitude modulation of guided beams in dielectric waveguides. Analysis based on both full-classical and semiclassical... 

    Cohen-Macaulayness and Limit Behavior of Depth for Powers of Cover Ideals

    , Article Communications in Algebra ; Volume 43, Issue 1 , Aug , 2015 , Pages 143-157 ; 00927872 (ISSN) Constantinescu, A ; Pournaki, M. R ; Seyed Fakhari, S. A ; Terai, N ; Yassemi, S ; Sharif University of Technology
    Taylor and Francis Inc  2015
    Abstract
    Let K{double-struck} be a field, and let R = K{double-struck}[x1,.., xn] be the polynomial ring over K{double-struck} in n indeterminates x1,.., xn. Let G be a graph with vertex-set {x1,.., xn}, and let J be the cover ideal of G in R. For a given positive integer k, we denote the kth symbolic power and the kth bracket power of J by J(k) and J[k], respectively. In this paper, we give necessary and sufficient conditions for R/Jk, R/J (k), and R/J [k] to be Cohen-Macaulay. We also study the limit behavior of the depths of these rings  

    Design and performance of an optical fiber sensor based on light leakage

    , Article Review of Scientific Instruments ; Volume 77, Issue 6 , 2006 ; 00346748 (ISSN) Golnabi, H ; Jafari, R ; Sharif University of Technology
    2006
    Abstract
    Design and operation of an optical fiber sensor based on the light leakage from one fiber to another one causing intensity modulation are reported. Performance of this sensor is tested as a liquid level sensor for different liquids and the experimental results are reported. The dry and wet signals for this probe are measured for a series of measurements and important factors concerning sensor operation are described. The precision of measured values, reproducibility of the results (1.3%), and the stability of sensing operation as a function of time at different launching powers are also reported (0.8%). The reported results are promising and verify the successful operation of such a device... 

    Various multirate time-hopping UWB systems and performance evaluation

    , Article 2004 IEEE International Symposium on Spread Spectrum Techniques and Applications, ISSSTA 2004, Sydney, 30 August 2004 through 2 September 2004 ; 2004 , Pages 120-124 Shayesteh, M. G ; Nasiri Kenari, M ; Sharif University of Technology
    2004
    Abstract
    We consider multirate time-hopping ultra-wideband (TH-UWB) communication systems where each user can have several multirate services. We investigate both constant spreading factor scheme, which uses multicode, and variable spreading factor scheme, which uses constant chip time and variable frame number. For multicode structure, we consider two methods. In the first, one kind of signature (PN) code is used to distinguish users and their diverse services alike. Whereas in the second one different users and different services of the same user are distinguished through two kinds of signature codes, namely PN code and Walsh code, respectively. For variable spreading factor scheme, one signature... 

    Ion Channel Based Bio-Synthetic Modulator for Diffusive Molecular Communication

    , Article IEEE Transactions on Nanobioscience ; Volume 15, Issue 5 , 2016 , Pages 418-432 ; 15361241 (ISSN) Arjmandi, H ; Ahmadzadeh, A ; Schober, R ; Nasiri Kenari, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    Abstract
    In diffusion-based molecular communication (DMC), a transmitter nanomachine is responsible for signal modulation. Thereby, the transmitter has to be able to control the release of the signaling molecules employed for representing the transmitted information. In nature, an important class of control mechanisms for releasing molecules from cells utilizes ion channels which are pore-forming proteins across the cell membrane. The opening and closing of the ion channels is controlled by a gating parameter. In this paper, an ion channel based modulator for DMC is proposed which controls the rate of molecule release from the transmitter by modulating a gating parameter signal. Exploiting the... 

    Nonlinear FM waveform design to reduction of sidelobe level in autocorrelation function

    , Article 2017 25th Iranian Conference on Electrical Engineering, ICEE 2017, 2 May 2017 through 4 May 2017 ; 2017 , Pages 1973-1977 ; 9781509059638 (ISBN) Ghavamirad, R ; Babashah, H ; Sebt, M. A ; Sharif University of Technology
    Abstract
    This paper will design non-linear frequency modulation (NLFM) signal for Chebyshev, Kaiser, Taylor, and raised-cosine power spectral densities (PSDs). Then, the variation of peak sidelobe level with regard to mainlobe width for these four different window functions are analyzed. It has been demonstrated that reduction of sidelobe level in NLFM signal can lead to increase in mainlobe width of autocorrelation function. Furthermore, the results of power spectral density obtained from the simulation and the desired PSD are compared. Finally, error percentage between simulated PSD and desired PSD for different peak sidelobe level are illustrated. The stationary phase concept is the possible... 

    A 10MHz CTDSM with differential VCO-based quantizer in 90nm

    , Article Proceedings of the 2013 8th International Conference on Design and Technology of Integrated Systems in Nanoscale Era, DTIS 2013 ; 2013 , Pages 128-133 ; 9781467360388 (ISBN) Yousefzadeh, B ; Hajian, A ; Sharifkhani, M ; Sharif University of Technology
    2013
    Abstract
    This paper presents a new architecture for VCO-based Continuous Time Delta Sigma Modulators. This approach is based on the differential configuration for the quantizer while maintains its inherent dynamic element matching property. Consuming no additional power and area compared to the conventional scheme, this architecture can eliminate the even orders of harmonic distortion and achieve higher linearity. Theoretical analysis for signal to quantization noise, power and area consumption and mismatch effect is provided. To illustrate the effectiveness of the new architecture in continuous time modulators, a modulator with 640 MHz sampling rate utilizing the mentioned quantizer is simulated in... 

    Performance improvement of an optimal family of exponentially accurate sigma delta modulator

    , Article International Conference on Signal Processing Proceedings, ICSP, 24 October 2010 through 28 October 2010, Beijing ; 2010 , Pages 1-4 ; 9781424458981 (ISBN) Kafashan, M ; Beygiharchegani, S ; Marvasti, F ; Sharif University of Technology
    2010
    Abstract
    In this paper a new iterative method is used to convert analog signals to digital (A/D) using sigma delta modulator (SDM). If intelligent reconstruction technique is used for decoding, either signals with higher bandwidth can be digitized or simpler circuitry can be utilized. An optimal family of SDM has recently been devised in order to improve performance of A/D converters. In this work, we improve performance of A/D converters even more, by combining this optimal family of SDM with iterative methods  

    A solution to gain attack on watermarking systems: logarithmic homogeneous rational dither modulation

    , Article ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings, 142010 through 19 March 2010 ; March , 2010 , Pages 1746-1749 ; 15206149 (ISSN) ; 9781424442966 (ISBN) Akhaee, M. A ; Amini, A ; Ghorbani, G ; Marvasti, F ; Sharif University of Technology
    2010
    Abstract
    Among the many attacks against watermarked data, the gain attack is less supported with countermeasures. The effectiveness of this attack becomes more evident in quantization-based embedding algorithms such as Dither Modulation (DM). In this paper, the general solution for both block and sample type DM schemes that are robust against gain attacks is considered. Among the solutions, we concentrate on a subclass of the algorithms which are insensitive to additive noise attacks; i.e., we introduce watermarking schemes which are both robust against gain and additive noise attacks. The simulation results confirm the desired performance of the final algorithm against these attacks while outperform... 

    A low-power, second-order Δ/∑ modulator using a single class-AB op-amp for voice-band applications

    , Article Analog Integrated Circuits and Signal Processing ; Volume 49, Issue 2 , 2006 , Pages 199-211 ; 09251030 (ISSN) Safarian, A ; Sahandiesfanjani, F ; Heydari, P ; Atarodi, S. M ; Sharif University of Technology
    2006
    Abstract
    The design of a power-efficient second-order Δ/∑ modulator for voice-band is presented. At system level, a new single-loop, single-stage modulator is proposed. The modulator employs only one class-AB op-amp to realize a second-order noise shaping for voice-band applications. The modulator is designed in a 0.25μm standard CMOS process, and exhibits 86 dB dynamic range (DR) for a 4 kHz voice-bandwidth. The proposed modulator consumes 125μW from a 2.5 V supply. © Springer Science + Business Media, LLC 2006