A long-period fiber grating (LPFG) sensor functionalized with titanium dioxide-chitosan/poly(acrylic acid) (TiO2-CS/PAA) composite film was proposed for detecting lead ion (Pb2+) concentration. The sensor was fabricated by sequentially coating a TiO2-CS/PAA composite functionalized film on the LPFG surface via the layer-by-layer (LbL) self-assembly method. The Chitosan (CS)/PAA layer acts as a general sensing film, with the abundant amino (-NH2) and hydroxyl (-OH) groups on CS providing sufficient chelation sites for Pb2+. Incorporation of PAA significantly improves both adsorption efficiency and mechanical stability. The sensitivity of the sensor is further enhanced by inserting a TiO2 layer with a high refractive index (RI), which can reduce the RI difference between the fiber and the external environment. Experimental results demonstrated that the resonance wavelength of LPFG exhibited a blue shift with the increase of Pb2+ concentration, achieving a maximum sensitivity of 36.5 nm/ mu M, a limit of detection (LOD) of 9.3 nM (0.00193 mg/L), and a rapid response time of approximately 10 min, along with high selectivity toward Pb2+. The proposed sensor features simple fabrication, excellent selectivity, and robust stability, indicating significant potential for Pb2+ monitoring applications.

The advancement of lithography, mass spectrometry and other technologies is increasingly requiring the highquality focusing of extreme ultraviolet (EUV) beams. Traditional transmissive optics are not suitable for focusing EUV beams due to the strong absorption of most materials. However, rapid developments of metasurfaces have led to breakthroughs in the research of EUV metalenses. Based on the hole-type unit structure proposed recently, we demonstrated the dual-wavelength achromatic metalens in the EUV working for wavelengths of 46.9 and 69.8 nm with a numerical aperture 0.05. Then the dispersion manipulation for the achromatic metalens is extended to three wavelengths 46.9, 60, and 69.8 nm. The simulation results suggest that the maximum relative focal shift from the designed focal length is 0.008 %, and the diffraction-limit focusing is achieved for all working wavelengths. This work could expand the means of the EUV optical field modulation.

Dielectric capacitors put forward higher requirements on the energy storage density, working stability and fatigue resistance of materials with the increasing shortage of energy. Herein, 0.8Na(0.5)Bi(0.5)TiO(3)-0.2Bi(3.25)La(0.75)Ti(3)O(12)-x%Mn (x = 0,2,4,6) thin film capacitors are designed to address above concern. The Mn ions inhibit the valence change of Ti ions and combine with oxygen vacancies to form defect dipoles, which improve breakdown strength and energy density of the films. As a result, high energy storage density of 92.7 J cm(-3) and excellent efficiency of 70.2% are synchronously achieved for the 4% Mn-doped NBT-BLT film. Besides, outstanding stability of energy storage performance also exhibit over a wide range of temperature (25-200 degrees C) and cycle number (10(5)). This result provides a novel strategy for the preparation of dielectric materials with high energy storage performance and high operational stability.

Based on the density functional theory with generalized gradient approximation, the adsorption behavior and optical properties of H2O molecules on the surface of VO2 and Pt loaded on the VO2 surface were calculated. The calculation results show that the adsorption energy of H2O molecules on the surface of VO2 is −0.39 eV, the bond length and bond angle of H2O molecules have not changed significantly, and the adsorption of H2O molecules on VO2 is physisorption. Further research shows that the adsorption energy of H2O molecules on the surface of Pt/VO2 is −1.76 eV, and the bond angle of H2O molecules on the surface of Pt/VO2 has changed significantly, increasing by 4°. The results show that H2O molecules adsorption on the surface of Pt/VO2 is chemisorption. Subsequently, we calculated the optical properties of the entire system and found that its light absorption capacity in the visible light region is ranked as follows: VO2+Pt+H2O>VO2+Pt>VO2+H2O>VO2. Our results demonstrate that Pt loaded on the VO2 surface not only affects the adsorption behavior of VO2, but also significantly modifies the electronic structure by generating impurity-derived states. Our results provide a reference for further study of the optical properties of VO2 and the dissociation reaction of H2O molecules.

ABSTRACT Based on first principles calculations of density functional theory, the adsorption behaviour of H S on the surface of intrinsic and Pd loaded VO was studied. According to the analysis of the adsorption performance of H S gas on intrinsic VO , the adsorption process of H S gas on the surface of intrinsic VO is spontaneous. In addition, we chose to load precious metal Pd on the surface of VO and found the best loading position. We used the best loading Pd site as the adsorption matrix, and calculated the adsorption behaviour of H S gas on the Pd/VO surface. The results showed that the active site was transferred from the B-1 site to the H-1 site due to the loading of the precious metal Pd. Further analysis found that the VO surface loaded with Pd has stronger adsorption performance for H S gas, which changed the adsorption performance of VO for H S gas. Finally, we studied the optical properties of VO before and after adsorbing H S and before and after loading Pd. We found that the order of response to visible light is as follows: VO +Pd+H S> VO +Pd> VO +H S> VO . Our results provide theoretical support for manufacturing suitable optical gas sensors. GRAPHICAL ABSTRACT

Here, we report a strong room-temperature magnetism in Ni-doped BaNbO3. The tetragonal BaNixNb(1-x)O3-delta nano-powders are prepared by the composite-hydroxide-mediated method. The as-prepared BaNixNb(1-x)O3-delta has a saturation magnetization (M-sat) of 2.54 emu/g, a remnant magnetization (M-r) of 0.228 emu/g, and a small coercive field (Hc) of 99.14 Oe at room temperature, presenting as a short-range magnetic order. The Ni-doping leads to an incommensurate valence state of Nb, and the oxidation state of Ni in the matrix is + 2. It brings not only strong local spin polarization to the matrix, but also balances the oxygen defects and gives rise to a more doping content. The strong magnetism originated from the existence of short-range magnetic order and the strong local net spin polarization at the Fermi level (E-F), which are proved by the first-principle calculations.

We study the spin-orbit interaction of two-dimensional electron/hole gas (2DEGs/2DHGs) on quasi-2D potassium niobates (KNs) via first-principles calculations. The strong surface polarity changes the free surface states from 2DEGs to 2DHGs. The in-plane dipole maintained on 2D models leads to giant Zeeman-type spin splitting, as high as 566 meV for the (001)c facet KN and 1.21 eV for the (111)c facet KN. The thickness-dependent Zeeman-type spin splitting shows a linear relation with respect to 1/r, while the corresponding in-plane polarization quantum has a linear relation of 1/(2^0.5)with respect to a decrease in thickness. Interestingly, the 2DHGs with molecular-like orbital character is solely constituted by O 2p states, showing logic switchable behavior at extremely thin samples with enormous Zeeman-type splitting that can switch between insulator and conductor by opposite spin polarization.

The oxidation behaviors of FeCrNiAl high entropy alloy at high temperature were investigated, and the oxidation kinetics model was constructed. The phase structure, morphology and composition of the alloy were characterized by XRD, SEM and EDS, and the oxidation mechanisms were analyzed. The results show that the alloy is fully oxidation-resistant at 800 similar to 1000 degrees C. The average oxidation rate in 100 h increases with increasing temperature at first and then decreases; it at 1000 degrees C is smaller than the one at 800 degrees C. The relationship between mass increment and oxidation time for all temperatures meets the parabola function, and the oxidation active energy is calculated to be 167.507 kJ/mol. The oxidation products in dendrite at 800 degrees C are bar-shaped TiO2 with rutile structure, while the interdendritic products are Cr2O3 and TiO2 which is plate shaped. The oxidation products at 900 degrees C are TiO2, Cr2O3 and Fe2O3, while TiO2 and alpha-Al2O3 at 950 degrees C are observed. Only tight alpha-Al2O3 film is obtained on the surface at 1000 degrees C, which results in excellent oxidation resistance.

A dual-axis reflective continuous-wave terahertz (THz) confocal scanning polarization imaging system was adopted. THz polarization imaging experiments on gaps on film and metallic letters "BeLLE" were carried out. Imaging results indicate that the THz polarization imaging is sensitive to the tilted gap or wide flat gap, suggesting the THz polarization imaging is able to detect edges and stains. An image fusion method based on the digital image processing was proposed to ameliorate the imaging quality of metallic letters "BeLLE." Objective and subjective evaluation both prove that this method can improve the imaging quality. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)

We present a dual-axis reflection confocal scanning microscope operating at 2.52 terahertz with axial resolution of 0.67 mm. The spatial resolution of the system was evaluated by utilizing the resolution test chart. Lateral resolution exceeded 0.314 mm, and the lengthwise resolution was over 0.353 mm. We introduced a 0.3 mm pinhole to improve the resolution. Targets such as the Chinese character "TAI" written on paper with a pencil and the metal letter "G" were scanned to test the imaging quality. To verify the imaging ability of the axial sections, two pairs of metal straps and a combinatorial metal ring were scanned, further revealing the satisfying 3D imaging capability.

In this study, structural, phase and mechanical stabilities as well as elastic, electronic and thermal properties of low cost Fe-based full-Heusler materials Fe2XY (X = Ti, Zr, Y = Si, Sn) were successfully studied by using the first-principles calculations based on density functional theory(DFT). The structural, phase and mechanical stabilities of all the investigated compounds have been verified for the first time. The optimized lattice constants for Fe2TiSi, Fe2TiSn, Fe2ZrSi and Fe2ZrSn are 5.658, 6.033, 5.899 and 6.227 angstrom respectively and the elastic constants C-ij, shear moduli G, bulk moduli B, Young's moduli E, B/G and poission ratios have been calculated. These heusler materials have small band gaps with flat band at the bottom of the conduction band and the calculated electronic properties imply that these alloys could be the very promising candidates of thermoelectric materials. Debye temperatures(Theta(D)), isochoric heat capacities(C-V), minimum thermal conductivities (k(min)) of Fe2XY (X = Ti, Zr, Y = Si, Sn) were predicted. Our result of study is interesting from the fundamental point of view, and it has a great significance when these materials are used in practical fabrications and applications. (C) 2016 Elsevier B.V. All rights reserved.

Phase retrieval algorithms applied to in-line digital holography reconstruction can weaken interference from the region outside the study target and an unstable light source, etc., by adopting the object-plane support domain constraint. Based on threshold segmentation and morphological filtering, a method to directly calculate the object-plane support domain is proposed in this paper. Combined with the above method, an improved support-domain constrained phase retrieval algorithm is presented. Then, imaging simulations and experiments on terahertz in-line digital holography reconstruction of nonisolated objects are conducted. The simulations study the influence of transmittance of the background plate, structural element of morphological filtering, etc., on the reconstruction effect of the improved algorithm without noise interference. Simulation and experiment results suggest that good reconstructed images can be obtained by this algorithm when transmittance of the background plate is greater than 0.90.

Compared with the visible light and infrared, terahertz (THz) radiation can penetrate nonpolar and nonmetallic materials. There are many studies on the THz coaxial transmission confocal microscopy currently. But few researches on the THz dual-axis reflective confocal microscopy were reported. In this paper, we utilized a dual-axis reflective confocal scanning microscope working at 2.52 THz. In contrast with the THz coaxial transmission confocal microscope, the microscope adopted in this paper can attain higher axial resolution at the expense of reduced lateral resolution, revealing more satisfying 3D imaging capability. Objects such as Chinese characters " Zhong-Hua" written in paper with a pencil and a combined sheet metal which has three layers were scanned. The experimental results indicate that the system can extract two Chinese characters " Zhong", " Hua" or three layers of the combined sheet metal. It can be predicted that the microscope can be applied to biology, medicine and other fields in the future due to its favorable 3D imaging capability.

We present a system to measure objective backscattering properties at 2.52 terahertz (THz). The optical setup combining 90° off-axis parabolic mirrors with 15° off-axis parabolic mirror decreases the size of the system and then realizes its compact structure. The calibration object, a conducting sphere with a diameter of 50 mm, was introduced to eliminate the influence of the instability of THz radiation and the background noise on measurement results. The lock-in amplifier was adopted to enhance the signal-to-noise ratio (SNR) and then make it possible to observe delicate backscattering behaviors on the surface of the object. Backscattering properties of four scale models were measured in this paper. Experimental results indicate that the maximal error of our system is less than 1 dB, paving the way for practical measurements of objective backscattering properties at THz frequencies.

With the development of terahertz technology and increasing studies on terahertz target scattering properties, research on terahertz target scattering properties measurements attracts more and more attention. In this paper, to solve problems in the detection process, we design a controlling software for Continuous-Wave (CW) terahertz target scattering properties measurements. The software is designed and programmed based on LabVIEW. The software controls the whole system, involving the switch between the target and the calibration target, the rotation of target, collection, display and storage of the initial data and display, storage of the data after the calibration process. The experimental results show that the software can accomplish the expected requirement, enhance the speed of scattering properties measurements and reduce operation errors.