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In the present work, the effects of Dy (dysprosium) additions (0, 0.05, 0.1, 0.15, 0.2, and 0.3wt%) on the microstructure and mechanical properties of hypereutectic Al–Si alloy have been studied. An inductively coupled plasma optical emission spectrometry (ICP-OES) apparatus was employed to measure the alloy composition. The specimens were examined using optical microscopy (OM) and scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDS). In the as-cast state, increasing the Dy content to 0.15% resulted in the refinement of the primary Si morphology from irregular polyhedral and branched shapes to fine polyhedral shapes, with the average size decreasing by 21% from 48 to 38 μm. Additionally, the eutectic Si transformed from coarse, uneven short rod-like structures to fibrous ones. Moreover, the tensile strength increased to 233 MPa, marking an 18.8% improvement, while the elongation reached 1.1%, indicating a significant increase of 267%. After T6 heat treatment, with a Dy content of 0.2%, the size of primary Si and eutectic Si did not change significantly compared with the 0.15% Dy addition. However, the mechanical properties of the alloy were optimized at this Dy content due to the fragmentation of the Al–Si-Fe-Mn phase and Al2Cu phase. The tensile strength increased to 242 MPa, reflecting a 14.7% improvement, and the elongation improved to 1.28%, representing a 60% enhancement compared with the alloy without Dy addition.Graphical Abstract: In the present work, the effects of Dy (dysprosium) additions (0, 0.05, 0.1, 0.15, 0.2, and 0.3wt%) on the microstructure and mechanical properties of hypereutectic Al–Si alloy have been studied. An inductively coupled plasma optical emission spectrometry (ICP-OES) apparatus was employed to measure the alloy composition. The specimens were examined using optical microscopy (OM) and scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDS). In the as-cast state, increasing the Dy content to 0.15% resulted in the refinement of the primary Si morphology from irregular polyhedral and branched shapes to fine polyhedral shapes, with the average size decreasing by 21% from 48 to 38 μm. Additionally, the eutectic Si transformed from coarse, uneven short rod-like structures to fibrous ones. Moreover, the tensile strength increased to 233 MPa, marking an 18.8% improvement, while the elongation reached 1.1%, indicating a significant increase of 267%. After T6 heat treatment, with a Dy content of 0.2%, the size of primary Si and eutectic Si did not change significantly compared with the 0.15% Dy addition. However, the mechanical properties of the alloy were optimized at this Dy content due to the fragmentation of the Al–Si-Fe-Mn phase and Al2Cu phase. The tensile strength increased to 242 MPa, reflecting a 14.7% improvement, and the elongation improved to 1.28%, representing a 60% enhancement compared with the alloy without Dy addition. [ABSTRACT FROM AUTHOR]

We report the design of ultra-broadband, highly reflective all-dielectric reflectors covering the entire visible regime based on two cascaded subwavelength high-index-contrast gratings (HCGs). We find that the spectral distance between the two gratings’ reflective bandwidths, which should be appropriately designed in order to extend the overall bandwidth for high reflectivity, is analogous to the well-known Rayleigh, Abbe and Sparrow criteria for resolution limits. Results illustrated with TM-polarized normal incidence show that high reflectivity above 98.5% covering 400–800 nm can be achieved for two cascaded HCGs with an appropriate spectral distance. The effects of key structural parameters on the bandwidth extension are discussed with physical insights. We expect this work will advance the engineering and applications of HCGs as ultra-thin, ultra-broadband and all-dielectric reflectors. [ABSTRACT FROM AUTHOR]

In this paper, some new continued fraction approximations, inequalities and rates of convergence of Glaisher-Kinkelin's and Bendersky-Adamchik's constants are provided. To demonstrate the superiority of our new convergent sequences over the classical sequences and Mortici's sequences, some numerical computations are also given at the end of this paper. [ABSTRACT FROM AUTHOR]

In this paper, we provide some new logarithm and polynomial approximations, inequalities and rates of convergence of Glaisher-Kinkelin's and Bendersky-Adamchik's constants. To demonstrate the superiority of our new convergent sequences over the classical sequences and Mortici's sequences, some numerical computations are also given at the end of this paper. [ABSTRACT FROM AUTHOR]

A surface plasmon resonance sensor based on a U-shaped photonic crystal fiber with a rectangular lattice has been designed through finite element method. The U-shaped fiber exhibits not only stronger mechanical strength but also better sensor performance than our previous scheme. The upper detection limit extends to higher analyze refractive index, 1.384, for phase interrogation. We introduce a ratio to evaluate the impact of higher order plasmonic mode. For wavelength modulation scheme, the parameter to describe the performance of a sensor is chosen to be the figure of merit, which can be up to 533.8[RIU] around complete coupling condition. [ABSTRACT FROM AUTHOR]

The radiotherapy-related types of nasopharyngeal carcinoma (NPC) have been established, which give the most effective treatment for NPC patients using the individual therapy. To diagnose the types of NPC, we assess the general NPC cell lines CNE1, CNE2 and normal nasopharyngeal cell line NP69 using optical coherence tomography (OCT) in two steps: firstly, the OCT images of the three different types of cell pellets are captured. Secondly, by fitting Beer's law to the averaged A-scans in these OCT datasets, the attenuation coefficients ( μ) of the cells can be extracted. The median attenuation coefficients (interquartile range) of CNE1, CNE2, and NP69 are 5.58 mm (IQR 5.55 to 5.65 mm), 5.91 mm (IQR 5.82 to 5.88 mm), and 8.96 mm (IQR 8.80 to 9.47 mm), respectively. The distinguishable quantitative OCT analysis (by μ) shows that the types of NPC could potentially be differentiated in real time and noninvasive. [ABSTRACT FROM AUTHOR]

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Photobiomodulation (PBM) is a modulation of laser irradiation or monochromatic light (LI) on biosystems, which stimulates or inhibits biological functions but does not result in irreducible damage. LI might be of low intensity LI (LIL) (about 10 mW/cm2), or moderate intensity LI (MIL) (102-103 mW/cm2). PBM of LIL or MIL (LPBM or MPBM) is studied from the homeostatic viewpoint in this paper. Homeostasis is rede.ned as the function-specific homeostasis (FSH), a negative-feedback response of a biosystem which maintains the function-specific conditions inside it. PBM is classified into two kinds, the FSH-specific PBM (fPBM) and developmental PBM (dPBM). For fPBM, there is no PBM of LI on the function in FSH, but there is PBM of LI on the function far from FSH. dPBM can disrupt FSH. It can be found that LPBM is an fPBM, and whether MPBM is fPBM or dPBM depends on MIL dose and cell sensitivity. Low level LI therapy is just clinical applications of fPBM, so that it is a cellular rehabilitation. [ABSTRACT FROM AUTHOR]

Based on the constant coefficients of Ginzburg-Landau equation that considers the influence of the doped fiber retarded time on the evolution of self-similar pulse, the parabolic asymptotic self-similar solutions were obtained by the symmetry reduction algorithm. The parabolic asymptotic amplitude function, phase function, strict linear chirp function and the effective temporal pulse width of self-similar pulse are given in this paper. And these theoretical results are consistent with the numerical simulations. [ABSTRACT FROM AUTHOR]

A novel scheme to compress optical pulses is proposed and demonstrated numerically, which is based on a nonlinear optical loop mirror constructed from dispersion decreasing fiber (DDF). We show that, in contrast to the conventional soliton-effect pulse compression in which compressed pulses are always accompanied by pedestals and frequency chirps owning to nonlinear effects, the proposed scheme can completely suppress pulse pedestals and frequency chirps. Unlike the adiabatic compression technique in which DDF length must increase exponentially with input pulsewidth, the proposed scheme does not require adiabatic condition and therefore can be used to compress long pulses by using reasonable fiber lengths. For input pulses with peak powers higher than a threshold value, the compressed pulses can propagate like fundamental solitons. Furthermore, the scheme is fairly insensitive to small variations in the loop length and is more robust to higher-order nonlinear effects and initial frequency chirps than the adiabatic compression technique. [ABSTRACT FROM AUTHOR]

The imaging theory of nonlinear second harmonic generation (SHG) and third harmonic generation (THG) in confocal microscopy is presented in this paper. The nonlinear effect of SHG and THG on the imaging properties of confocal microscopy has been analyzed in detail by the imaging theory. It is proved that the imaging process of SHG and THG in confocal microscopy, which is different from conventional coherent imaging or incoherent imaging, can be divided into two different processes of coherent imaging. The three-dimensional point spread functions (3D-PSF) of SHG and THG confocal microscopy are derived based on the nonlinear principles of SHG and THG. The imaging properties of SHG and THG confocal microscopy are discussed in detail according to its 3D-PSF. It is shown that the resolution of SHG and THG confocal microscopy is higher than that of single-and two-photon confocal microscopy. [ABSTRACT FROM AUTHOR]

A simple strain method is used to change uniform gratings into chirped gratings. The correspondent theory is presented. It is deduced that the product of the maximum bandwidth and the corresponding dispersion is nearly equal to a constant. The dispersion compensation distance for standard single-mode fiber G.652,10 Gb/s systems over 100 km is realized by using this method. [ABSTRACT FROM AUTHOR]

The nonlinear Schrödinger equation with variable parameters is solved by means of variational technique. A set of evolution equations for the solitary-wave solution is derived. The propagation properties of the solitons in an adiabatic amplification system and in a dispersion-decreasing fiber are analyzed. An explicit analytical approximate soliton solution in the exponentially dispersion-decreasing fiber is obtained using the derived dynamical equations. [ABSTRACT FROM AUTHOR]