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کاربرد نوع شرط:
- جایگاه : پژوهشی
- مجله: Amirkabir (Journal of Science and Technology)
- نوع مقاله: Journal Article
- کلمات کلیدی:
- چکیده:
- چکیده انگلیسی:
- انتشار مقاله: 16-05-1396
- نویسندگان: S.A. HOSSEINI RAVANDI,S.A. HOSSEINI RAVANDI,
- مشاهده
- جایگاه : پژوهشی
- مجله: Wavelet and Linear Algebra
- نوع مقاله: Journal Article
- کلمات کلیدی: Schur multiplier,Numerical radius,Schur product,Geometric product,Positive semidefinite matrix
- چکیده:
- چکیده انگلیسی: For A ∈ M n, the Schur multiplier of A is defined as S A(X) = A ◦ X for all X ∈ M n and the spectral norm of S A can be state as ∥S A∥ = supX,0 ∥A ∥X ◦X ∥ ∥. The other norm on S A can be defined as ∥S A∥ω = supX,0 ω(ω S( AX (X ) )) = supX,0 ωω (A (X ◦X ) ), where ω(A) stands for the numerical radius of A. In this paper, we focus on the relation between the norm of Schur multiplier of product of matrices and the product of norm of those matrices. This relation is proved for Schur product and geometric product and some applications are given. Also we show that there is no such relation for operator product of matrices. Furthermore, for positive definite matrices A and B with ∥S A∥ω ⩽ 1 and ∥S B∥ω ⩽ 1, we show that A♯B = n(I − Z)1/2C(I + Z)1/2, for some contraction C and Hermitian contraction Z.
- انتشار مقاله: 16-06-1394
- نویسندگان: M. Khosravi,A. Sheikhhosseini
- مشاهده
- جایگاه : پژوهشی
- مجله: The ISC International Journal of Information Security
- نوع مقاله: Journal Article
- کلمات کلیدی: Encryption,QTRU,NTRU,Quaternion Algebra,Public-Key Cryptography
- چکیده:
- چکیده انگلیسی: In this paper we will construct a lattice-based public-key cryptosystem using non-commutative quaternion algebra, and since its lattice does not fully fit within Circular and Convolutional Modular Lattice (CCML), we prove it is arguably more secure than the existing lattice-based cryptosystems such as NTRU. As in NTRU, the proposed public-key cryptosystem relies for its inherent security on the intractability of finding the shortest vector in a certain non-convolutional modular lattice, yet it is efficient and cost effective, contrary to cryptosystems such as RSA or ECC. The detailed specification of the proposed cryptosystem, including the underlying algebraic structure, key generation, encryption and decryption process and also the issues regarding key security, message security, and probability of successful decryption are explained. We will further show, based on the existing results for lattice-reduction algorithms, that the proposed cryptosystem with a dimension of 41 will have a security equal to NTRU-167.
- انتشار مقاله: 15-05-1389
- نویسندگان: E. Malekian,A. Zakerolhosseini,A. Mashatan
- مشاهده
- جایگاه : پژوهشی
- مجله: The ISC International Journal of Information Security
- نوع مقاله: Journal Article
- کلمات کلیدی: blindness,Blind Signature,Elliptic Curves Cryptosystems,Untraceability
- چکیده:
- چکیده انگلیسی: Elliptic Curve Cryptosystems (ECC) have recently received significant attention by researchers due to their high performance such as low computational cost and small key size. In this paper a novel untraceable blind signature scheme is presented. Since the security of proposed method is based on difficulty of solving discrete logarithm over an elliptic curve, performance of the proposed scheme is quite commendable in comparison with the previous work in terms of security and time complexity.
- انتشار مقاله: 24-08-1387
- نویسندگان: M. Nikooghadam,A. Zakerolhosseini
- مشاهده
- جایگاه : پژوهشی
- مجله: Progress in Color, Colorants and Coatings
- نوع مقاله: Journal Article
- کلمات کلیدی: Wavelet Analysis,Electrochemical,Electrochemical noise,Nanocomposite Polyvinyl butyral,mpedance Spectroscopy
- چکیده:
- چکیده انگلیسی: In this work, polypyrrole/ZnO nanocomposite (PPy/ZnO NC) was produced through synthesis of polypyrrole polymer in the presence of ZnO nanoparticles. The corrosion behavior of polyvinyl butyral coatings without and with different weight percentages of nanocomposite on the surface of 7075 Al alloy was investigated in 3.5% NaCl solution at different immersion times using electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN) techniques. The coating with 0.025% PPy/ZnO NC revealed the highest corrosion resistance. In order to analysis of EN data, wavelet transform was used to obtain the standard deviation of partial signal (SDPS) plots. The good agreement between the EIS and EN results indicates that the EN technique, as well as the EIS method, can be used successfully for the corrosion evaluation of coatings.
- انتشار مقاله: 11-10-1348
- نویسندگان: G.S. Sajadi,S.M.A. Hosseini,M.J. Bahrami,M. Shahidi
- مشاهده
- جایگاه : پژوهشی
- مجله: Progress in Color, Colorants and Coatings
- نوع مقاله: Journal Article
- کلمات کلیدی: Phosphoric acid,Polarization,Corrosion inhibitor,Electrochemical Impedance Spectroscopy (EIS),Scanning Electron Microscopy (SEM),Electrochemical noise resistance
- چکیده:
- چکیده انگلیسی: The inhibitive effect of apricot gum AG on mild steel in 0.5 M phosphoric acid solution was investigated by potentiodynamic polarization, electrochemical impedance spectroscopy EIS, linear polarization resistance and electrochemical noise EN techniques. The inhibition efficiency increased with increasing AG concentration up to a certain value and decreased with increasing temperature. Polarization curves indicated that AG acts as a mixed type inhibitor. The EN data were analyzed by statistical and wavelet methods. The results obtained from analysis of EN data was in good agreement with those arising from the polarization and EIS measurements. The adsorption of the inhibitor on the alloy surface in 0.5 M H3PO4 followed the Langmuir isotherm. According to the calculated values of free energy and enthalpy adsorption it was revealed that the adsorption of inhibitor on the steel surface was a combination of physical and chemical adsorption. The morphologies of the uninhibited and inhibited mild steel surfaces in 0.5 M H3PO4 were analyzed by scanning electron microscope SEM. SEM images showed that the alloy surface damage is significantly decreased in presence of the inhibitor.
- انتشار مقاله: 11-10-1348
- نویسندگان: A. Mohammadi,S.M.A. Hosseini,M.J. Bahrami,M. Shahidi
- مشاهده
- جایگاه : پژوهشی
- مجله: Progress in Color, Colorants and Coatings
- نوع مقاله: Journal Article
- کلمات کلیدی: Black,lightness,Blackness preference,Visual assessment
- چکیده:
- چکیده انگلیسی: In this paper, the effect of lightness on blackness preference of 216 black fabrics prepared by printing method is investigated. 18 observers including of 9 males and 9 females are asked to firstly rank order black fabrics with the same lightness values according to their preference. In the next step, observers are asked to define their blackness preference for blacks with different L values. Results show that while there are some neutral black fabrics, observers mostly prefer bluish-cyanish blacks. Besides, samples with the higher values of lightness and chroma are not preferred by observers especially if their hue angles lie in the first quarter of the hue area, i.e., 0-90o. Meanwhile, samples with the lowest lightness values are not preferred by most of observers because of their high chroma values. This achievement proves that lightness is not the only colorimetric attributes which influences on blackness preference.
- انتشار مقاله: 06-11-1392
- نویسندگان: S. H. Amirshahi,S. A. Hosseini Ravandi
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Solid Mechanics
- نوع مقاله: Journal Article
- کلمات کلیدی: AFM,Vibration analysis,Nonlocal elasticity theory,U-shaped probe,Euler–Bernoulli beam theory
- چکیده:
- چکیده انگلیسی: Atomic force microscope (AFM) has been developed at first for topography imaging; in addition, it is used for characterization of mechanical properties. Most researches have been primarily focused on rectangular single-beam probes to make vibration models simple. Recently, the U-shaped AFM probe is employed to determine sample elastic properties and has been developed to heat samples locally. In this study, a simplified analytical model of these U-shaped AFM is described and three beams have been used for modelling this probe. This model contains two beams are clamped at one end and connected with a perpendicular cross beam at the other end. The beams are supposed only in bending flexure and twisting, but their coupling allows a wide variety of possible dynamic behaviors. In the present research, the natural frequency and sensitivity of flexural and torsional vibration for AFM probes have been analyzed considering influence of scale effect. For this purpose, governing equations of dynamic behavior of U-shaped AFM probe are extracted based on Eringen's theory using Euler–Bernoulli beam theory and an analytical method is employed to solve these equations. The results in this paper have been extracted for different values of nonlocal parameters; it is shown that for a special case, there is a good agreement between reported results in available references and our results. The obtained results show that the frequencies of U-shaped AFM decrease with increasing the nonlocal parameter.
- انتشار مقاله: 22-11-1396
- نویسندگان: M Ghadiri,S.A.H Hosseini,M Karami,M Namvar
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Solid Mechanics
- نوع مقاله: Journal Article
- کلمات کلیدی: parametric excitation,Multiple Scales Method,Rotating Shaft
- چکیده:
- چکیده انگلیسی: Dynamic behavior of a circular shaft with geometrical nonlinearity and constant spin, subjected to periodic axial load is investigated. The case of parametric combination resonance is studied. Extension of shaft center line is the source of nonlinearity. The shaft has gyroscopic effect and rotary inertia but shear deformation is neglected. The equations of motion are derived by extended Hamilton principle and discretized by Galerkin method. The multiple scales method is applied to the complex form of equation of motion and the system under parametric combination resonance is analyzed. The attention is paid to analyze the effect of various system parameters on the shape of resonance curves and amplitude of system response. Furthermore, the role of external damping on combination resonance of linear and nonlinear systems is discussed. It will be shown that the external damping has different role in linear and nonlinear shaft models. To validate the perturbation results, numerical simulation is used.
- انتشار مقاله: 01-11-1396
- نویسندگان: M.S Qaderi,S.A.A Hosseini,M Zamanian
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Solar Energy Research
- نوع مقاله: Journal Article
- کلمات کلیدی: Concentrated solar power,Turbocharger,Solar thermal power system,Cavity receiver
- چکیده:
- چکیده انگلیسی: The aim of this paper is to introduce a design and build of a small low cost CSP system with simplicity in construction as a means of power generator for remote areas and residential buildings. Advantages of the designed device are: There are no curvatures, instead of that some flat mirrors are installed in a rectangular Aluminum frame. In order to reach higher efficiency, a cavity receiver and a two axial sun detector system is used. Also a modified turbocharger is playing role as an expander. By making required number of the collector panels parallel (or series) the requested output power or mass flow rate can be achieved. The results show that the maximum temperature of empty cavity receiver (without working fluid) is around 710 degrees Centigrade. Hence, the effectiveness of the receiver is about 92% by calculations. For 6.2 m2 collector panel, output is 1 KW and the cost is estimated to be roughly around $1350. Also there is another output which provides hot water for heating purposes.
- انتشار مقاله: 03-05-1396
- نویسندگان: H. Shokouhmand,S. Ebadi,A. Pournadali Khamseh,M. Negahban,A. Sattari,S.A. Hosseini-Doost
- مشاهده