932 research outputs found
Ergodic and fixed point theorems for sequences and nonlinear mappings in a Hilbert space
No full textIn this paper, we introduce the notion of 2-generalized hybrid sequences, extending the notion of nonexpansive and hybrid sequences introduced and studied in our previous work [Djafari Rouhani B., Ergodic theorems for nonexpansive sequences in Hilbert spaces and related problems, Ph.D. thesis, YaleUniversity, 1981; and other published in J. Math. Anal. Appl., 1990, 2002, and 2014; Nonlinear Anal., 1997, 2002, and 2004], and prove ergodic and convergence theorems for such sequences in a Hilbert space H. Subsequently, we apply our results to prove new fixed point theorems for 2-generalized hybrid mappings, first introduced in [Maruyama T., Takahashi W., Yao M., Fixed point and mean ergodic theorems for new nonlinear mappings in Hilbert spaces, J. Nonlinear Convex Anal., 2011, 12, 185-197] and further studied in [Lin L.-J., Takahashi W., Attractive point theorems and ergodic theorems for nonlinear mappings in Hilbert spaces, Taiwanese J. Math., 2012, 16, 1763-1779], defined on arbitrary nonempty subsets of H
Numerical emulation of Thru-Reflection-Line calibration for the de-embedding of Surface Acoustic Wave devices
No full textIn this contribution, a rigorous numerical calibration is proposed to characterize the excitation of propagating mechanical waves by interdigitated transducers (IDTs). The transition from IDT terminals to phonon waveguides is modeled by means of a general circuit representation that makes use of Scattering Matrix (SM) formalism. In particular, the three-step calibration approach called the Thru-Reflection-Line (TRL), that is a well-established technique in microwave engineering, has been successfully applied to emulate typical experimental conditions. The proposed procedure is suitable for the synthesis/optimization of surface-acoustic-wave (SAW) based devices: the TRL calibration allows to extract/de-embed the acoustic component, namely resonator or filter, from the outer IDT structure, regardless of complexity and size of the letter. We report, as a result, the hybrid scattering parameters of the IDT transition to a mechanical waveguide formed by a phononic crystal patterned on a piezoelectric AlN membrane, where the effect of a discontinuity from periodic to uniform mechanical waveguide is also characterized. In addition, to ensure the correctness of our numerical calculations, the proposed method has been validated by independent calculations
Band gap engineering in simultaneous phononic and photonic crystal slabs
No full textWe discuss the simultaneous existence of phononic and photonic band gaps in two types of phononic crystals
slabs, namely periodic arrays of nanoholes in a Si membrane
and of Si nanodots on a SiO2 membrane. In the former
geometry, we investigate in detail both the boron nitride
lattice and the square lattice with two atoms per unit cell
(these include the square, triangular and honeycomb lattices
as particular cases). In the latter geometry, some preliminary
results are reported for a square lattice
Simultaneous guidance of slow photons and slow acoustic phonons in silicon phoxonic crystal slabs
No full textThis paper was published in OPTICS EXPRESS and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/OE.19.009690. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law[EN] We demonstrate theoretically that photons and acoustic phonons can be simultaneously guided and slowed down in specially designed nanostructures. Phoxonic crystal waveguides presenting simultaneous phononic and photonic band gaps were designed in perforated silicon membranes that can be conveniently obtained using silicon-on-insulator technology. Geometrical parameters for simultaneous photonic and phononic band gaps were first chosen for optical wavelengths around 1550 nm, based on the finite element analysis of a perfect phoxonic crystal of circular holes. A plain core waveguide was then defined, and simultaneous slow light and elastic guided modes were identified for some waveguide width. Joint guidance of light and elastic waves is predicted with group velocities as low as c/25 and 180 m/s, respectively. © 2011 Optical Society of America.This research has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement number 233883 (TAILPHOX).Laude, V.; Beugnot, J.; Benchabane, S.; Pennec, Y.; Djafari-Rouhani, B.; Papanikolaou, N.; Escalante Fernández, JM.... (2011). Simultaneous guidance of slow photons and slow acoustic phonons in silicon phoxonic crystal slabs. Optics Express. 19(10):9690-9698. https://doi.org/10.1364/OE.19.009690S969096981910Kushwaha, M. S., Halevi, P., Dobrzynski, L., & Djafari-Rouhani, B. (1993). Acoustic band structure of periodic elastic composites. Physical Review Letters, 71(13), 2022-2025. doi:10.1103/physrevlett.71.2022Maldovan, M., & Thomas, E. L. (2006). Simultaneous localization of photons and phonons in two-dimensional periodic structures. Applied Physics Letters, 88(25), 251907. doi:10.1063/1.2216885Maldovan, M., & Thomas, E. L. (2006). Simultaneous complete elastic and electromagnetic band gaps in periodic structures. Applied Physics B, 83(4), 595-600. doi:10.1007/s00340-006-2241-yAkimov, A. V., Tanaka, Y., Pevtsov, A. B., Kaplan, S. F., Golubev, V. G., Tamura, S., … Bayer, M. (2008). Hypersonic Modulation of Light in Three-Dimensional Photonic and Phononic Band-Gap Materials. Physical Review Letters, 101(3). doi:10.1103/physrevlett.101.033902Sadat-Saleh, S., Benchabane, S., Baida, F. I., Bernal, M.-P., & Laude, V. (2009). Tailoring simultaneous photonic and phononic band gaps. Journal of Applied Physics, 106(7), 074912. doi:10.1063/1.3243276Papanikolaou, N., Psarobas, I. E., & Stefanou, N. (2010). Absolute spectral gaps for infrared light and hypersound in three-dimensional metallodielectric phoxonic crystals. Applied Physics Letters, 96(23), 231917. doi:10.1063/1.3453448Mohammadi, S., Eftekhar, A. A., Khelif, A., & Adibi, A. (2010). Simultaneous two-dimensional phononic and photonic band gaps in opto-mechanical crystal slabs. Optics Express, 18(9), 9164. doi:10.1364/oe.18.009164Pennec, Y., Rouhani, B. D., El Boudouti, E. H., Li, C., El Hassouani, Y., Vasseur, J. O., … Martinez, A. (2010). Simultaneous existence of phononic and photonic band gaps in periodic crystal slabs. Optics Express, 18(13), 14301. doi:10.1364/oe.18.014301Safavi-Naeini, A. H., & Painter, O. (2010). Design of optomechanical cavities and waveguides on a simultaneous bandgap phononic-photonic crystal slab. Optics Express, 18(14), 14926. doi:10.1364/oe.18.014926El Hassouani, Y., Li, C., Pennec, Y., El Boudouti, E. H., Larabi, H., Akjouj, A., … Djafari Rouhani, B. (2010). Dual phononic and photonic band gaps in a periodic array of pillars deposited on a thin plate. Physical Review B, 82(15). doi:10.1103/physrevb.82.155405Khelif, A., Aoubiza, B., Mohammadi, S., Adibi, A., & Laude, V. (2006). Complete band gaps in two-dimensional phononic crystal slabs. Physical Review E, 74(4). doi:10.1103/physreve.74.046610Hussein, M. I. (2009). Reduced Bloch mode expansion for periodic media band structure calculations. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 465(2109), 2825-2848. doi:10.1098/rspa.2008.0471Johnson, S. G., Fan, S., Villeneuve, P. R., Joannopoulos, J. D., & Kolodziejski, L. A. (1999). Guided modes in photonic crystal slabs. Physical Review B, 60(8), 5751-5758. doi:10.1103/physrevb.60.5751Xu, T., Wheeler, M. S., Nair, S. V., Ruda, H. E., Mojahedi, M., & Aitchison, J. S. (2008). Highly confined mode above the light line in a two-dimensional photonic crystal slab. Applied Physics Letters, 93(24), 241105. doi:10.1063/1.3046124Laude, V., Achaoui, Y., Benchabane, S., & Khelif, A. (2009). Evanescent Bloch waves and the complex band structure of phononic crystals. Physical Review B, 80(9). doi:10.1103/physrevb.80.092301Laude, V., Khelif, A., Benchabane, S., Wilm, M., Sylvestre, T., Kibler, B., … Maillotte, H. (2005). Phononic band-gap guidance of acoustic modes in photonic crystal fibers. Physical Review B, 71(4). doi:10.1103/physrevb.71.045107Dainese, P., Russell, P. S. J., Joly, N., Knight, J. C., Wiederhecker, G. S., Fragnito, H. L., … Khelif, A. (2006). Stimulated Brillouin scattering from multi-GHz-guided acoustic phonons in nanostructured photonic crystal fibres. Nature Physics, 2(6), 388-392. doi:10.1038/nphys31
S. Rouhani M. Vesali
No full textWe have investigated the magnetic phases of the random energy model in the presence of an external magnetic field. We have calculated the finite size corrections to the magnetisation and susceptibility in the ferromagnetic phase and the finite size corrections to the free energies within the paramagnetic phase. We give the paramagnetic and ferromagnetic subphases of the random energy model in the finite size.The relationship with coding theory is discussed. 1 Introduction Sourlas has shown how coding theory is connected with spin glasses [?]. He argues that the received message from a noisy channel is simply a spin glass Hamiltonian. If we take a special parity checking algorithm, this means that every symbol of the coded message is a combination of p spins, we arrive at Derrida's Hamiltonian with full connectivity [?]. In this Hamiltonian the coupling constants follow a random gaussian distribution with a non-zero mean. In the context of Derrida's model a nonzero mean can lead to the..
Dual phononic and photonic band gaps in a periodic array of pillars deposited on a thin plate
No full textWe study theoretically the simultaneous existence of phononic and photonic band gaps in a periodic array of
silicon pillars deposited on a homogeneous thin silica plate. Several lattices, namely, square, triangular, and
honeycomb are investigated for a wide range of geometrical parameters. We discuss the most suitable cases for
dual phononic-photonic band gaps, especially in comparison to the more conventional structures constituted by
a periodic array of holes in a membrane
Teoría de funciones de green aplicada a modos de excitación de magnetoplasma en geometrías cilíndricas
No full textExtendiendo la teoría de funciones de Green recientemente desarrollada por M. S. Kushwaha and B. Djafari-Rouhani [1] a un sistema cilíndrico con una y dos interfaces bajo la acción de un campo magnético, estudiamos los modos de excitación de un plasma confinado en la geometría de Faraday. La función de repuesta lineal del sistema se obtuvo explícitamente en el límite no-retardado, lo que permitió obtener varias propiedades físicas, tales como la ley de dispersión y el poder espectral de los modos colectivos
Ethical considerations for remote sensing and open data in relation to the endangered archaeology in the Middle East and North Africa project
No full textThe UK-based Endangered Archaeology in the Middle East and North Africa (EAMENA) project uses remote sensing techniques to rapidly record and evaluate the status of archaeological and cultural heritage sites in the MENA region. Applying remote sensing methods to the archaeological landscapes of 20 countries, EAMENA is one of the largest documentation projects of its kind. Such a scope raises important ethical questions fundamental to the practice of remote-sensed archaeology, and this paper contributes to this discussion by reflecting on EAMENA's unique role in this subfield. We present ethical issues and possible solutions related to remote sensing and archaeology, drawing on models developed within the humanitarian aid sector and postcolonial archaeology. In addition, we consider issues of national sovereignty and their relationship to the engagement of local communities. Finally, this paper examines the roles of data openness and open access policies as ethical factors and how EAMENA has addressed these so far
Evanescent modes in sonic crystals: complex dispersion relation and supercell approximation
No full textEvanescent modes in complete sonic crystals (SCs) and SC with point defects are reported both theoretically and experimentally in this paper. Plane wave expansion (PWE) and in general, ω(k)ω(k) methods have been used to calculate band structures showing gaps that have been interpreted as ranges of frequencies where no real kk exists. In this work, we extend PWE to solve the complex k(ω)k(ω) problem applied to SC, introducing the supercell approximation for studying one vacancy. Explicit matrix formulation of the equations is given. This k(ω)k(ω) method enables the calculation of complex band structures, as well as enabling an analysis of the propagating modes related with real values of the function k(ω)k(ω), and the evanescent modes related with imaginary values of k(ω)k(ω). This paper shows theoretical results and experimental evidences of the evanescent behavior of modes inside the SC band gap. Experimental data and numerical results using the finite elements method are in very good agreement with the predictions obtained using the k(ω)k(ω) method.The authors would like to thank Dr. E. A. Sanchez-Perez for his comments and suggestions and thank Daniel Fenollosa and Talleres Ferriols for their help in building the mechanical part of 3DReAMS. This work was supported by MEC (Spanish government) and the European Regional Development Fund, under Grant Nos. MAT2009-09438 and MTM2009-14483-C02-02.Romero García, V.; Sánchez Pérez, JV.; García Raffi, LM. (2010). Evanescent modes in sonic crystals: complex dispersion relation and supercell approximation. Journal of Applied Physics. 108(4):449071-4490716. doi:10.1063/1.3466988S44907144907161084Martínez-Sala, R., Sancho, J., Sánchez, J. V., Gómez, V., Llinares, J., & Meseguer, F. (1995). Sound attenuation by sculpture. Nature, 378(6554), 241-241. doi:10.1038/378241a0Kushwaha, M. S., Halevi, P., Dobrzynski, L., & Djafari-Rouhani, B. (1993). Acoustic band structure of periodic elastic composites. Physical Review Letters, 71(13), 2022-2025. doi:10.1103/physrevlett.71.2022Sigalas, M., & Economou, E. N. (1993). Band structure of elastic waves in two dimensional systems. Solid State Communications, 86(3), 141-143. doi:10.1016/0038-1098(93)90888-tYablonovitch, E. (1987). Inhibited Spontaneous Emission in Solid-State Physics and Electronics. Physical Review Letters, 58(20), 2059-2062. doi:10.1103/physrevlett.58.2059John, S. (1987). Strong localization of photons in certain disordered dielectric superlattices. Physical Review Letters, 58(23), 2486-2489. doi:10.1103/physrevlett.58.2486Sigalas, M. M., Economou, E. N., & Kafesaki, M. (1994). Spectral gaps for electromagnetic and scalar waves: Possible explanation for certain differences. Physical Review B, 50(5), 3393-3396. doi:10.1103/physrevb.50.3393Economou, E. N., & Sigalas, M. M. (1993). Classical wave propagation in periodic structures: Cermet versus network topology. Physical Review B, 48(18), 13434-13438. doi:10.1103/physrevb.48.13434Kushwaha, M. S., Halevi, P., Martínez, G., Dobrzynski, L., & Djafari-Rouhani, B. (1994). Theory of acoustic band structure of periodic elastic composites. Physical Review B, 49(4), 2313-2322. doi:10.1103/physrevb.49.2313Hernández-Cocoletzi, H., Krokhin, A., & Halevi, P. (1995). Reality of the eigenfrequencies of periodic elastic composites. Physical Review B, 51(23), 17181-17183. doi:10.1103/physrevb.51.17181Sánchez-Pérez, J. V., Caballero, D., Mártinez-Sala, R., Rubio, C., Sánchez-Dehesa, J., Meseguer, F., … Gálvez, F. (1998). Sound Attenuation by a Two-Dimensional Array of Rigid Cylinders. Physical Review Letters, 80(24), 5325-5328. doi:10.1103/physrevlett.80.5325Sanchez-Perez, J. V., Rubio, C., Martinez-Sala, R., Sanchez-Grandia, R., & Gomez, V. (2002). Acoustic barriers based on periodic arrays of scatterers. Applied Physics Letters, 81(27), 5240-5242. doi:10.1063/1.1533112Khelif, A., Choujaa, A., Djafari-Rouhani, B., Wilm, M., Ballandras, S., & Laude, V. (2003). Trapping and guiding of acoustic waves by defect modes in a full-band-gap ultrasonic crystal. Physical Review B, 68(21). doi:10.1103/physrevb.68.214301Khelif, A., Wilm, M., Laude, V., Ballandras, S., & Djafari-Rouhani, B. (2004). Guided elastic waves along a rod defect of a two-dimensional phononic crystal. Physical Review E, 69(6). doi:10.1103/physreve.69.067601Wu, L.-Y., Chen, L.-W., & Liu, C.-M. (2009). Experimental investigation of the acoustic pressure in cavity of a two-dimensional sonic crystal. Physica B: Condensed Matter, 404(12-13), 1766-1770. doi:10.1016/j.physb.2009.02.025Engelen, R. J. P., Mori, D., Baba, T., & Kuipers, L. (2009). Subwavelength Structure of the Evanescent Field of an Optical Bloch Wave. Physical Review Letters, 102(2). doi:10.1103/physrevlett.102.023902Wu, F., Hou, Z., Liu, Z., & Liu, Y. (2001). Point defect states in two-dimensional phononic crystals. Physics Letters A, 292(3), 198-202. doi:10.1016/s0375-9601(01)00800-3Zhao, Y.-C., & Yuan, L.-B. (2008). Characteristics of multi-point defect modes in 2D phononic crystals. Journal of Physics D: Applied Physics, 42(1), 015403. doi:10.1088/0022-3727/42/1/015403Vasseur, J. O., Deymier, P. A., Djafari-Rouhani, B., Pennec, Y., & Hladky-Hennion, A.-C. (2008). Absolute forbidden bands and waveguiding in two-dimensional phononic crystal plates. Physical Review B, 77(8). doi:10.1103/physrevb.77.085415Hsue, Y.-C., Freeman, A. J., & Gu, B.-Y. (2005). Extended plane-wave expansion method in three-dimensional anisotropic photonic crystals. Physical Review B, 72(19). doi:10.1103/physrevb.72.195118Laude, V., Achaoui, Y., Benchabane, S., & Khelif, A. (2009). Evanescent Bloch waves and the complex band structure of phononic crystals. Physical Review B, 80(9). doi:10.1103/physrevb.80.092301Sainidou, R., & Stefanou, N. (2006). Guided and quasiguided elastic waves in phononic crystal slabs. Physical Review B, 73(18). doi:10.1103/physrevb.73.184301Sigalas, M. M. (1998). Defect states of acoustic waves in a two-dimensional lattice of solid cylinders. Journal of Applied Physics, 84(6), 3026-3030. doi:10.1063/1.36845
Perubahan Kebijakan Nuklir Iran di Era Pemerintahan Hassan Rouhani
No full textThis research aimed to describe the changing of Iran nuclear policy era President Hassan Rouhani. This research aims to look at the different policy of the President Iran, be-tween Mahmoud Ahmadinejad (2005-2013) and Hassan Rouhan 2013-present). In 2012, Mahmoud Ahmadinejad has rejected the agreement with P5+1 (America, Russia, England, France, China plus Germany) to stop their uranium enrichment. It cause some sanctions for Iran from United Nations Security Council. The the impact of sanctions on Iran including high inflation, low growth, and coagulation asset in foreign state.The perspective that applied in this research is behavioralist , level analysis of indi-vidual, and also use theory from William D. Coplin about of foreign policy-making, there are three things to be considered by a leader in taking a foreign policy; the domestic political conditions, economic and military conditions, and international context.Hassan Rouhani as a new president of Iran tries to rebuild the economy of Iran, by undertake a nuclear talks with P5+1 state. These negotiations resulted an interim deal for six months (since November 2013 until May 2014). Which Iran agreed to suspend uranium enrichment, willing to dilute the uranium up to five percent of maximum limit, and not build-ing new centrifuges for uranium enrichment. In return, Iran would get liquefaction in foreign asset amounted to US$ 7 billion, their right to export and import oil, and acknowledgment in their nuclear for peace programme.Keywords: Behavioralist, foregin policy-making, Iran, nuclear, P5+
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