圆极化波反射聚焦超表面

基于圆极化波入射条件下的高效同极化反射超表面实现了对圆极化反射波相位的自由调控, 设计了一维圆极化波反射聚焦超表面. 在中心频率f=16 GHz附近, 右旋圆极化平面波入射时, 反射波聚焦于焦距L=200 mm的实焦点; 左旋圆极化波入射时, 反射波近似聚焦于焦距L=-200 mm的虚焦点. 仿真计算得到聚焦波束的波束宽度、焦深. 结果表明, 这种圆极化反射聚焦超表面具有很好的聚焦效果, 同时具有长焦深和宽带特性.     

Comparative studies for different proximity potentials applied to α decay

The European Physical Journal A - The energy-weighted integrated cross-section for photon absorption --known as sum rule $ \sigma_{-1}$ -- is under certain conditions proportional to the mean...     

One‐pot Synthesis of Nitrogen and Phosphorus Co‐doped Graphene and Its Use as High‐performance Electrocatalyst for Oxygen Reduction Reaction

In this study, N,P co‐doped graphene (NPG) was prepared by a one‐step pyrolysis using a mixture of graphene oxide and hexachlorocyclotriphosphazene (HCCP), in which HCCP was used as both the N and P source. Furthermore, it is shown that NPG electrodes, as efficient metal‐free electrocatalysts, have a high onset potential, high current density, and long‐term stability for the oxygen reduction reaction.     

Photoinitiated crosslinking of EPDM/inorganic filler blends and characterization of related properties

<正>Photoinitiated crosslinking of ethylene-propylene-diene terpolymer(EPDM) blends filled with calcium carbonate, talc and calcined kaolin(CK) in the presence of benzil dimethyl ketal as photoinitiator and trimethylolpropane triacrylate as crosslinker and their related properties have been studied by different analytical methods.The results from gel content and heat extension determination show that the efficiency of photocrosslinking of EPDM increases with increasing the content of diene and its molecular weight.The EPDM blends with 100 phr different inorganic fillers can be photocrosslinked to gel content of above 60%by 5 s UV-irradiation under optimum conditions.Under the same conditions of irradiation,the orders of photocrosslinking rate and final gel content are EPDM/CaCO_3EPDM/talcEPDM/CK.The data from thermogravimetric analysis,dynamic mechanical thermal analysis,electrical properties,mechanical tests and scanning electron microscopy show that UV irradiation crosslinking apparently enhances the thermal stability,mechanical properties and electrical properties of the photocrosslinked EPDM/inorganic filler samples.Although the attenuated total-reflection FTIR data show that inorganic fillers can promote the surface photo-oxidation of EPDM/inorganic filler samples with increasing the irradiation time,the above related properties of the photocrosslinked EPDM blends irradiated within 5 s are enough to satisfy many applications in the cable industry.     

三维有序大孔交联聚苯乙烯的功能化及其吸附性能

本研究采用二氧化硅胶体晶模板法制备了孔径为890nm的三维有序大孔交联聚苯乙烯(3DOMCLPS),通过亲核取代反应将亲水性悬臂(二缩三乙二醇,TEG)接枝到3DOMCLPS孔壁,利用TEG另一端的活性羟基,将2-巯基苯并噻唑(MBZ)引入到TEG链段末端.利用红外光谱及元素分析对产物进行了表征.扫描电镜分析表明功能化后的3DOMCLPS保留了结构有序、孔与孔之间相互连通的微观结构特点.测定了该功能化3DOMCLPS对Ag+和Hg2+离子的饱和吸附容量,饱和吸附容量分别为0.78和0.39mmol/g.研究了不同温度下的吸附动力学,相互连通的有序大孔结构有利于引入长链亲水性悬臂,促进孔内外的物质交换.     

Spin-Hamiltonian parameters and angular distortion for the trigonal Nd3+ center in congruent LiNbO3

The 52 × 52 energy matrix related to the ground multiplet ⁴I_9/2 and the first to third excited multiplets ⁴I_11/2, ⁴I_13/2 and ⁴I_15/2 for 4f³ ions in trigonal crystal field under an external magnetic field is established. By diagonalizing the energy matrix, the spin-Hamiltonian parameters (g factor g_//, g_⊥ and hyperfine structure constants ¹⁴³A_//, ¹⁴³A_⊥, ¹⁴⁵A_//, ¹⁴⁵A_⊥) of the trigonal Nd³⁺ center in congruent LiNbO₃ crystal are calculated. The calculated results are in reasonable agreement with the experimental values. From the calculations, the negative signs of hyperfine structure constants are suggested and the angular distortion of the trigonal Nd³⁺ center in LiNbO₃, which is unable to be determined by EXAFS measurement, is obtained. The results are discussed.     

Photocrosslinking of EVA/inorganic filler blends and characteristics of related properties

The blends of EVA filled with talc, calcium carbonate, and glass ball (GB) have been photocrosslinked by UV irradiation in the presence of benzophenone (BP) as a photoinitiator and triallyl isocyanurate (TAIC) as a crosslinker. The various factors affecting the crosslinking process and the related properties have been studied by gel determination, heat extension test, mechanical and thermal aging test, UV spectroscopy, and scanning electron microscopy. The results show that the EVA/talc, EVA/CaCO₃, and EVA/GB samples of 1 mm thickness filled with 25 phr inorganic filler can be photocrosslinked to gel content of above 70 wt% by 5 sec UV‐irradiation under optimum conditions, which is sufficient for some applications of EVA blend materials. The crosslinking rate and final gel content level are in the order of EVA/GB > EVA/talc > EVA/CaCO₃. The data from mechanical and thermal aging tests give evidence that the photocrosslinked EVA/talc, EVA/CaCO₃, and EVA/GB samples are of much better tensile strength and thermal aging properties than those of the unphotocrosslinked ones. Copyright © 2009 John Wiley & Sons, Ltd.     

Micellar and aqueous‐organic liquid chromatography using sub‐2 μm packings for fast separation of natural phenolic compounds

The objective of the present work was to investigate the chromatographic behavior of natural phenolic compounds in micellar and aqueous‐organic LC using a short column packed with 1.8 μm particles. Firstly, the effect of ACN and SDS on elution strength and selectivity was examined by isocratic submicellar (0–30% ACN/5% 1‐butanol/1–6 mM SDS) and micellar (0–30% ACN/5% 1‐butanol/40–60 mM SDS) systems. The varied concentrations of two modifiers in the mobile phases revealed different eluting power. Then, the application of organic modifier gradient was discussed in both submicellar and micellar LC using mobile phases of 4 mM SDS/5% 1‐butanol or 50 mM SDS/5% 1‐butanol containing ACN gradient from 0 to 30%, respectively. For micellar system, the separation was found to be better in gradient than isocratic elution. Additionally, the sensitivity of aqueous‐organic LC was examined. The mobile phase was a mixture of ACN and water employing gradient elution at a flow rate of 0.5 mL/min, with analysis time below 9 min. It was found that separation efficiency was significantly better compared with micellar LC. Besides, the aqueous‐organic LC has been applied to separation of various phenolic compounds in Yangwei granule or Radix Astragali samples.     

First results on Fe solid-phase extraction from coastal seawater using anatase TiO2 nano-particles

This paper describes the application of TiO₂ nano-particles (anatase form) for the solid-phase extraction of iron from coastal seawater samples. We investigated the adsorption processes by infra-red spectroscopy. We compared in batch and on-(mini)column extraction approaches (0.1 and 0.05 g TiO₂ per sample, respectively), combined to external calibration and detection by inductively coupled plasma mass spectrometry at medium mass resolution. Globally, this titania phase was slightly more efficient with seawater than with ultra-pure water, although between pH 2 and pH 7, the Fe retention efficiency progressed more in ultra-pure water than in seawater (6.9 versus 4.8 times improvement). Different reaction schemes are proposed between Fe(III) species and the two main categories of titania sites at pH 2 (adsorption of [FeL _x ]^{(3 − x)+} via possibly the mediation of chlorides) and at pH 7 (adsorption of [Fe(OH)₂]⁺ and precipitation of [Fe(OH)₃]⁰). Under optimised conditions, the inlet system was pre-cleaned by pumping 6% HCl for ∼2 h, and the column was conditioned by aspirating ultra-pure water (1.7 g min⁻¹) and 0.05% ammonia (0.6 g min⁻¹) for 1 min. Then 3 g seawater sample was loaded at the same flow rate while being mixed on-line with 0.05% ammonia at 0.6 g min⁻¹ to adjust the pH to 7. The iron retained on the oxide powder was then eluted with 3 g 6% HCl (<0.002% residual salinity in the separated samples). The overall procedural blank was 220 ± 46 (2 s, n = 16) ng Fe kg⁻¹ (the titania was renewed in the column every 20 samples, with 2-min rinsing in between samples with 6% HCl at 1.5 g min⁻¹). The recovery estimated from the Canadian certified reference material CASS-2 was 69.5 ± 7.6% (2 s, n = 4). Typically, the relative combined uncertainty (k = 2) estimated for the measurement of ∼1 μg Fe kg⁻¹ (0.45 μm filtered and acidified to pH 1.5) of seawater was ∼12%. We applied our method to a similar sample, from the coastal region of the North Sea. The agreement well within stated uncertainties of our result with the value obtained independently by isotope dilution mass spectrometry further validated our method.     

Influence of fluorescent dye on the linear polarization direction of stimulated Raman Stokes scattering in liquid‐core optical fibers

We present a simple analytical model to describe the stimulated Raman Stokes scattering (SRS) linear polarization spectroscopy of fluorescent dye solutions in liquid‐core optical fibers (LCOFs). In this scheme, the linear polarization direction of the pump pulse is set parallel to the y‐axis through a straight polarization‐maintaining LCOF, in which the energy of the total optical field is kept invariant, and different fluorescence dyes are used to generate different first‐order Stokes intensities. We demonstrate the SRS of all‐trans‐β‐carotene and fluorescein in carbon disulfide (CS₂) solutions due to the optical field‐induced reorientation effect, which makes the first‐order Stokes polarization direction rotate by an angle of 88° or 61°, respectively. This demonstrates the good agreement between the theory presented and the experiment. Copyright © 2010 John Wiley & Sons, Ltd.