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<jats:p>Denoising of chaotic signal is a challenge work due to its wide-band and noise-like characteristics. The algorithm should make the denoised signal have a high signal to noise ratio and retain the chaotic characteristics. We propose a denoising method of chaotic signals based on sparse decomposition and K-singular value decomposition (K-SVD) optimization. The observed signal is divided into segments and decomposed sparsely. The over-complete atomic library is constructed according to the differential equation of chaotic signals. The orthogonal matching pursuit algorithm is used to search the optimal matching atom. The atoms and coefficients are further processed to obtain the globally optimal atoms and coefficients by K-SVD. The simulation results show that the denoised signals have a higher signal to noise ratio and better preserve the chaotic characteristics.</jats:p>

<jats:p>An NO<jats:sub>2</jats:sub> photoacoustic sensor system with a high reflective mirror based on a low power blue diode laser is developed in this work. The excitation power is enhanced by increasing the number of reflections. Comparing with a traditional photoacoustic system, the pool constant is improved from 300.24 (Pa⋅cm)/W to 1450.64 (Pa⋅cm)/W, and the signal sensitivity of the photoacoustic sensor is increased from 0.016 μV/ppb to 0.2562 μV/ppb. The characteristics of temperature and humidity of the new photoacoustic sensor are also obtained, and the algorithm is adjusted to provide a quantitative response and drift of the resonance frequency. The results of this research provide a new method and concept for further developing the NO<jats:sub>2</jats:sub> photoacoustic sensors.</jats:p>

<jats:p>We present a state-to-state dynamical calculation on the reaction S<jats:sup>+</jats:sup>+H<jats:sub>2</jats:sub>→ SH<jats:sup>+</jats:sup> + H based on an accurate X<jats:sup>2</jats:sup>A″ potential surface. Some reaction properties, such as reaction probability, integral cross sections, product distribution, <jats:italic>etc.</jats:italic>, are found to be those with characteristics of an indirect reaction. The oscillating structures appearing in reaction probability <jats:italic>versus</jats:italic> collision energy are considered to be the consequence of the deep potential well in the reaction. The comparison of the present total integral cross sections with the previous quasi-classical trajectory results shows that the quantum effect is more important at low collision energies. In addition, the quantum number inversion in the rotational distribution of the product is regarded as the result of the heavy–light–light mass combination, which is not effective for the vibrational excitation. For the collision energies considered, the product differential cross sections of the title reaction are mainly concentrated in the forward and backward regions, which suggests that there is a long-life intermediate complex in the reaction process.</jats:p>

<jats:p>A series of barium pyrophosphate Ba<jats:sub>2</jats:sub>P<jats:sub>2</jats:sub>O<jats:sub>7</jats:sub> (BPO) phosphors doped with Ce<jats:sup>3+</jats:sup> or Tb<jats:sup>3+</jats:sup> ions is synthesized via a co-precipitation method under reducing atmosphere. The phase structures, photoluminescence (PL) properties, and thermal stabilities of the samples are characterized by using powder x-ray diffraction (PXRD) and PL spectra. The emission colors of samples can be tuned from blue (0.1544, 0.0310) to green (0.2302, 0.4229) by changing the doping concentrations of Tb<jats:sup>3+</jats:sup> under ultraviolet excitation. The energy transfer mechanism between Ce<jats:sup>3+</jats:sup> and Tb<jats:sup>3+</jats:sup> in the BPO is dipole–dipole interaction with a critical distance of 25.86 Å and an energy transfer efficiency of about 85%, which are determined through the PL spectrum and the decay curve. Moreover, the Ce<jats:sup>3+</jats:sup>/Tb<jats:sup>3+</jats:sup> co-doped sample has good thermal stability for temperature quenching, and the emission intensity at 423 K is maintained at 95% measured at 298 K. The above results show that the BPO:Ce<jats:sup>3+</jats:sup>, Tb<jats:sup>3+</jats:sup> can serve as a promising candidate of green emitting phosphor for solid-state lighting.</jats:p>

<jats:p>The direct Coulomb explosion of N<jats:sub>2</jats:sub>O<jats:sup>2+</jats:sup> has been investigated experimentally after double-ionization by a single extreme ultraviolet (EUV) photon with an energy of ∼ 38.5 eV. From the ion–ion time-of-flight coincidence spectrum, the de-nitrogenation (N<jats:sub>2</jats:sub> <jats:sup>O<jats:sup>2+</jats:sup> </jats:sup> → N<jats:sup>+</jats:sup> + NO<jats:sup>+</jats:sup>) and de-oxygenation (N<jats:sub>2</jats:sub>O<jats:sup>2+</jats:sup>→ O<jats:sup>+</jats:sup> + N<jats:sub>2</jats:sub> <jats:sup>+</jats:sup>) photodissociation channels of N<jats:sub>2</jats:sub>O<jats:sup>2+</jats:sup> are unequivocally identified. The measured kinetic energy release (KER) distribution of the de-nitrogenation channel presents a major peak accompanied by a shoulder structure. We find that the major peak can be attributed to the direct photodissociation of the 1<jats:sup>1</jats:sup>Δ and 1<jats:sup>1</jats:sup>Σ<jats:sup>+</jats:sup> states, while the shoulder structure should be ascribed to the predissociation of the 1<jats:sup>1</jats:sup>Σ and 1<jats:sup>1</jats:sup>Σ<jats:sup>+</jats:sup> states via 1<jats:sup>3</jats:sup>Π state.</jats:p>

<jats:p>In this paper, we design a one-dimensional anti-<jats:italic>PT</jats:italic>-symmetric ring optical waveguide network (1D APTSPROWN). Using the three-material network equation and the generalized Floquet–Bloch theorem, we investigate its photonic mode distribution, and observe weak extremum spontaneous anti-<jats:italic>PT</jats:italic>-symmetric breaking points (WBPs) and strong extremum spontaneous anti-<jats:italic>PT</jats:italic>-symmetric breaking points (SBPs). Then the transmission spectrum is obtained by using the three-material network equation and the generalized eigenfunction method. The 1D APTSPROWN is found to generate ultra-strong transmission near SBPs and ultra-weak transmission near WBPs and SBPs, with the maximal and minimal transmissions being 4.08× 10<jats:sup>12</jats:sup> and 7.08× 10<jats:sup>−52</jats:sup>, respectively. The maximal transmission has the same order of magnitude as the best-reported result. It is not only because the distribution of photonic modes generated by the 1D APTSROWN results in the coupling resonance and anti-resonance, but also because the 1D APTSROWN composed of materials whose real parts of refractive indices are positive and negative has two kinds of phase effects, which results in the resonance and anti-resonance effects in the same kind of photonic modes. This demonstrates that the anti-<jats:italic>PT</jats:italic>-symmetric and <jats:italic>PT</jats:italic>-symmetric optical waveguide networks are quite different, which leads to a more in-depth understanding of anti-<jats:italic>PT</jats:italic>-symmetric and <jats:italic>PT</jats:italic>-symmetric structures. This work has the potential for paving a new approach to designing single photon emitters, optical amplifiers, and high-efficiency optical energy saver devices.</jats:p>

<jats:p>We investigate a family of radially polarized Pearcey–Gauss vortex beams (RPPGVBs), obtain the general propagation expressions of an RPPGVB, and study the intensity distribution, phase pattern, spin currents as well as the orbital currents when the RPPGVB propagates in free space. The focal plane and the intensity of the focal point can be adjusted by changing the position of the vortex and the scaling factors. We also investigate how the waist size influences the propagation properties.</jats:p>

<jats:p>We derive theoretically and verify experimentally a concise general expression for the normalized intensity correlations (IC) of partially coherent light in a weak atmospheric turbulence in the fast detector measurement regime. The derived relation reveals that the medium turbulence acts, in general, as an additional noise source enhancing the IC of partially coherent beams. The maximum of the beam IC is, in general, enhanced, causing the fields to exhibit super-Gaussian statistics. On the other hand, the relation indicates that turbulence-induced noise is negligible for sufficiently low coherence light, which reveals the condition for the turbulence-free correlation imaging.</jats:p>

<jats:p>We numerically and experimentally demonstrate that a three-Airy autofocusing beam can be generated by superposing three deformed two-dimensional (2D) Airy beams with a triangle symmetry. When the initial angle between two wings of the deformed 2D Airy beams increases, such a three-Airy autofocusing beam exhibits that the focusing length decreases and the intensity contrast at the focal point changes. Moreover, after introducing an optical vortex phase, this three-Airy autofocusing beam displays a transverse rotation in propagation. The rotation angle is determined by the topological charge of the vortex and the initial wing angle. Our results may have some potential applications in optical manipulation.</jats:p>

<jats:p>This paper presents photoacoustic and ultrasonic dual-mode imaging for real-time detection of submucosal gastric cancer with a combination of gastroscopy. The diagnostic capacity was directly addressed via several phantoms and <jats:italic>ex vivo</jats:italic> experiments. Results demonstrated that superficial and submucosal gastric cancer can be diagnosed with a perceptible depth of 6.33 mm, a lateral accuracy of 2.23 mm, and a longitudinal accuracy of 0.17 mm though capturing the morphology of angiogenesis, which is a main character of the therioma-related change. The capability of gastroscopy-conjugated photoacoustic and ultrasonic dual-mode imaging system will own great potential in improving the clinical diagnostic rate of submucosal gastric cancer.</jats:p>