查看更多>>摘要：We analyze the modulational instability (MI) of a continuous wave (CW) in saturable fiber systems, including higher-order dispersions, self steepening, and self-frequency shift, cubic, quintic, and septic nonlinearities. We show that whenever the combined effect of higher-order dispersion and non-Kerr nonlinearities with suitable systems meets a wide variety of MI behaviors by mixing different combinations are presented. By modifying the nonlinear Schrodinger equation (NLSE) for MI analysis using Maxwell's theory, the new solution is derived for linear stability analysis to obtain an expression for the MI gain. Among different combinations of higher-order dispersion and non-Kerr nonlinearities, the critical behavior of MI gain suppressed under saturable systems, which leads to affect the nature of soliton stability. Under the activation of self steepening and self-frequency shift in the saturable system, the generated MI behavior regained its original to retain the soliton stability. This kind of new and tuning of MI behavior will be a useful instrument in nonlinear optic communications with straightforward applications.
查看更多>>摘要：The S-Boxes with high nonlinearity and low differential uniformity are highly desirable for designing a secure image encryption scheme to ensure secure communication of digital images over the Internet. This paper presents a novel image cryptosystem using key-dependent bijective S-Boxes based on the Henon map. In this paper, the 2D Henon-map is used to generate key dependent bijective S-Boxes (for confusion) and pseudo-random sequence (for diffusion) to design a color image cryptosystem with high confusion and diffusion capability. We perform the security analysis of the proposed encryption scheme and the experimental results shows that the proposed image encryption scheme is able to resist the statistical attack (entropy and NIST randomness test), differential attack (NPCR and UACI), correlation and chosen-plaintext attack.
Antonio Medina-Vazquez, JoseMurillo-Ramirez, Jose G.Yamel Gonzalez-Ramirez, Evelyn
8页
查看更多>>摘要：A photonic structure built on a Si-ZnO substrate described by a rectangular region with a square lattice of circular cylindrical air-holes presenting a unidirectional transmission of a light beam was studied. The unidirectional transmission was obtained introducing a triangular spatial asymmetry region without air-holes adjacent to a photonic structure using as a starting point the total internal reflection effect. The optical properties of the photonic structure were optimized by numerical calculations and used to build a photonic structure by the FIB technique. Both, the calculated and the experimentally measured value of the forward transmittance of the photonic diode were 94% at the design working wavelength equal to the average backward transmittance of the photonic structure was around 10%. The forward and backward transmittances gave a oneway contrast ratio equal to 0.808. It was found an extraordinary effect of autofocus and confinement of the optical electric field associated with the incident light beam along the central region for forward propagation direction. In the case of backward propagation direction, the amplitude of the optical electric field transmitted through the photonic structure was almost negligible, showing only an appreciable magnitude close to the triangular region.
Khan, FirozAlshahrani, ThamraaFareed, ImranAhmad, Nafis...
9页
查看更多>>摘要：Due to lowering the material cost, the thin film-based photovoltaic (PV) technologies are pro-gressively drawing substantial concentration in the PV community. Among them, Cu(In, Ga)Se-2 (CIGS) is considered a potential absorbing material due to its higher absorption and changeable band-gap. But it produced a low value of current at the short wavelength region. Thus, the short circuit current density (J(sc)) is greatly reduced, which results in a lower value of the conversion efficiency. Here, N-doped graphene quantum dots (N-GQDs) are used as luminescent photon downshifters (LDS). Furthermore, the N-GQDs are embedded in the poly(methylmethacrylate) (PMMA) to enhance the chemical and mechanical stability of the LDS. However, the PMMA creates the photoluminescence (PL) quenching, which lessens the efficacy of the LDS layer. The LDS composite layer is formed in the various solvents. Furthermore, these LDS composites were evaluated via deployment onto the CIGS solar cells. The best performance is obtained in the chlorobenzene solvent. By insertion of the LDS composite layer, the J(sc) was enhanced from 33.58 to 35.32 mA/cm(2,) which resulted in an enhancement in the efficiency from 13.08% to 14.62%. The PV cell parameters analysis revealed that recombination is reduced due to growing the number of photons, which results in the performance enhancement of the CIGS solar cells.
查看更多>>摘要：In this article, we investigate the optical rogue wave structures and phase transitions in a light guide fiber system doped with two-level resonant atoms, which is governed by four-coupled (2+1)-dimensional nonlinear Schrodinger-Maxwell-Bloch (SMB) equations. The analytical rogue wave solutions are derived by utilizing the generalized Darboux transformation. Furthermore, the structures and phase transitions of the rogue waves are systematically studied. We reveal that there coexist four geometric structures: stripe-like, one-leaf-like, three-leaf-like and four-leaf-like rogue waves. The system parameter can be used to generate and control the phase transitions.
查看更多>>摘要：Large scale light field rendering of real scene is very important for the area of image-based modeling and parallax-based 3D display. With this in mind, we tried to use simple cameras, lenses, motion platform and a host PC to capture the light field and render it for 3D display. It extends our ability to capture the 3D information of the real scene in an effective and compact way, elemental image array for 3D display can be generated without the need of any pixel interpolation or virtual view synthesis. Optical experiment verified the validity of the designed system.
查看更多>>摘要：A metamaterial structure with a unit cell made of a metallic slab with two short and two long cut-wires is introduced in a computational work, simulating electromagnetically induced transparency (EIT) at microwave wavelengths. The structure introduced is flexible in applications and, by suitable manipulation of geometrical parameters, can be utilized for different practical purposes. It is shown that the structure can operate as a microwave sensor in a relatively wide temperature range around the room temperature. The sensitivity and figure of merit (FOM) of the sensor is relatively high, with the maximum value of the FOM calculated to be 24. By suitable geometrical tailoring, it is also shown that the proposed structure has the potential to be used in slow light devices as well, with a large value, 436, achieved for the group index. Effects of the slab height on the group index is also studied.
查看更多>>摘要：Optical fiber has been widely employed for intrusion detection in both civilian and military applications. Currently, most intrusion detection systems collect data properties from optical fiber before detecting intrusion via feature analysis. We present two intrusion detection methods based on system identification in this paper to solve the problem of optical fiber intrusion characteristics that are weak and difficult to extract under windy conditions.The first algorithm estimates the noise covariance of the system at each point. The Frobenius norm of the difference between the noise covariance of different points is used to detect the intrusion. The second algorithm applies the state parameters of non-intrusion point to reconstruct the output of each point by using Kalman filter, and the cross reconstruction error is calculated to recognize intrusion. The two algorithms are tested by data collected from field experiments. The results of the tests demonstrate that the proposed algorithms are both effective. When compared, the first algorithm has greater robustness, whereas the second takes less time to compute.
查看更多>>摘要：Eu3+ was ideal red emitter due to its efficient red emitting transitions D-5(0)-> F-7(j) and Ce3+ was most common sensitizer due to its strong parity-allowed absorption bands. However, direct sensitization of Ce3+ on Eu3+ (SCE) in hexagonal NaYF4 was very weak and unpractical. In this work, rate equations were introduced to elaborate the details of energy transfer (ET) among Ce3+, Gd3+ and Eu3+ in NaYF4, and how the SCE was much enhanced. The pure hexagonal phase of all samples were guaranteed by powder XRD patterns and SEM images, despite the morphology was influenced by rare earth components. While increasing Eu3+ concentration over 0.03, SCE was drastically dimished; on the contrary, it could be 60 folds enhanced by trTdoping Gd3+ ions. The rate equations of sensitizers were established and solved by calculating the lifetimes. It was found out that, while increasing Gd3+ concentration to 0.4, ET Ce -> Gd could compete against ET Ce -> Eu to capture 73.8% of energy absorped by Ce3+, which strongly favored SCE. The solution also revealed that SCE originated from ET chain Ce -> Gd -> Eu was much more efficient than direct SCE from ET Ce -> Eu, which originated the significant enhancement.
查看更多>>摘要：Traditional local active contour models mainly depend on the data fitting term to obtain image edge information, which are sensitive to the position of initial contour. In fact, setting an unreasonable initial contour will result in a time-consuming image segmentation process and difficult evolution at weak boundary. To solve this problem, we come up with a second-order edge detection operator which is based on the global gradient image information to replace the traditional data fitting term, and to obtain edge information with higher speed and accuracy. In addition, the anisotropic edge enhancement method has been introduced to improve the robustness to the weak boundary. In this way, an active contour model which is insensitive to initial contour position is proposed to achieve a faster and more accurate image segmentation result.
NSTL
Elsevier