A novel ultracompact two-mode-interference wavelength division multiplexer for 1.5-/spl mu/m operation

A novel ultracompact 2/spl times/2 wavelength division multiplexer (WDM) for 1.55-/spl mu/m operation based on highly dispersive two-mode interference (TMI) was designed, theoretically modeled, and verified using a finite-difference-time-domain (FDTD) method. A two-moded waveguide assisted with a dispersive tooth-shaped grating provided a mode-dependent reflection band of central wavelength at 1.55 /spl mu/m. The wavelengths of 1538 and 1572 nm that were at the band edges and had the lowest reflection losses and relatively high dispersion were selected for wavelength multiplexing. The result showed that the wavelengths were separated by grating dispersion in a coupler length of 75 /spl mu/m which was much shorter than the required length of 1.1 mm in a regular TMI multiplexer of no grating. Insertion loss of about 1.7 dB and channel contrast of about 12 dB were achieved.     

Synthesis of nanophase tungsten carbide by electrical discharge machining

Tungsten carbide nanopowders were synthesized successfully by electric discharge machining followed by annealing under a nitrogen atmosphere. The tungsten workpieces were initially melted and evaporated on the working surface during the electric discharge machining process, and then the tungsten powders were reacted with the carbon electrode and the working medium of kerosene to form the nanocrystalline WC_1−x powders. The powders produced were characterized by XRD, SEM, and TEM. When annealing the powders under an N₂ atmosphere, the cubic phases of WC_1−x gradually changed to hexagonal W₂C and then were transformed fully to nanocrystalline hexagonal WC at 1200 °C, with the nanocrystalline tungsten carbide encapsulated in a carbon shell. On the other hand, under an H₂ atmosphere, the WC_1−x phase changed via a W₂C phase to reduced powders of pure tungsten at 1000 °C or were reduced directly from WC_1−x to elemental W.     

Photolamination bonding for PMMA microfluidic chips

Finding out a rapid and reliable bonding method for plastic microfluidic chips with PCR functions is challenging for analytical chemistry and biochemistry. A rapid, reliable covalent bonding method is introduced for fabricating PMMA PCR biochips with long channels and thin walls. The bonding strength of ~5 MPa was obtained and bulk cohesive failure occurred during tensiling tests. Preliminary leaking tests indicate that photolamination bonding can be implemented readily in the fabrication of PMMA PCR biochips.     

Manufacture and characterization of sol–gel V1−x−yWxSiyO2 films for uncooled thermal detectors

V_1−x−yW_xSi_yO₂ films for uncooled thermal detectors were coated on sodium-free glass slides with sol–gel process, followed by the calcination under a reducing atmosphere (Ar/H₂ 5%). The V_1−x−yW_xSi_yO₂ films as prepared inherit various phase transition temperatures ranging from 20 to 70 °C depending on the dopant concentrations and the fabrication conditions. Compared to the hysteresis loop of plain VO₂ films, a rather steep loop was obtained with the addition of tungsten components, while a relaxed hysteresis loop with the tight bandwidth was contributed by Si dopants. Furthermore, the films with switching temperature close to room temperature were fabricated to one-element bolometers to characterize their figures of merit. Results showed that the V_0.905W_0.02Si_0.075O₂ film presented a satisfactory responsivity of 2600 V/W and detectivity of 9 × 10⁶ cm  Hz^1/2/W with chopper frequencies ranging from 30 to 60 Hz at room temperature. It was proposed that with appropriate amount of silicon and tungsten dopants mixed in the VO₂, the film would characterize both a relaxed hysteresis loop and a fair TCR value, which effectively reduced the magnitude of noise equivalent power without compromising its performance in detectivity and responsivity.     

一种基于矩和支配点检测的多边形拟合算法

提出一种基于几何矩和支配点检测的多边形拟合算法.支配点检测法可以最大范围地保留原始轮廓特征,但拟合后顶点数偏多.而基于几何矩的多边形拟合算法虽然可以将拟合后的顶点数控制在指定范围内,但是却容易使拟合结果陷入局部最优.本文对这两种算法进行关键步骤和参数的改进,并将它们有机结合起来,使得本文算法可以将绝大多数闭合曲线在全局最优的情况下将其拟合成任意顶点数的多边形.     

无机微颗粒絮凝剂NFAO的制备及性能研究

介绍了FeCl3溶胶制备方法、由FeCl3溶胶和AlCl3溶液制备絮凝剂NFAC的方法及所得NFAC的物化特性.以加量5 mg/L的絮凝剂对高岭土悬浮液浊度的去除率为评价指标筛选FeCl3与ACl3的反应条件,结果如下:AlCl3、FeCl3摩尔比5∶1,反应体系pH值2.0,反应温度25℃,反应时间30 min.用所筛选的工艺条件制备的NFAC处理胜利油田桩西联合站浊度130.47 NTU、含油24.13 mg/L的采油污水,加量20 mg/L,浊度和含油去除率分别为78.19%和81.02%,在相同条件下工业聚合氯化铝的浊度和舍油去除率分别为49.11%和57.14%.表2参6.     

γ-Ray radiolysis of acetohydroxamic acid in HNO_3 and its radiolytic product

Acetohydroxamic acid(AHA) is a novel saltfree reagent used for the separation of Pu and Np from U in the advanced Purex process. This paper reports the c-ray damage of AHA in HNO_3 and its radiolytic product. For 0.2 mol L~(-1) AHA in 0.2–2.0 mol L~(-1) HNO_3 irradiated at a dose of 5–25 kGy, the radiolytic rate of AHA is6.63–77.5%, and it increases with the HNO_3 concentration and absorbed dose. The main radiolytic gases are N_2O and H_2, with volume fractions of(0.500–16.2) 9 10~(-2) and(1.30–11.8) 9 10~(-3), respectively, and they increase with the absorbed dose; the H_2 volume fraction decreases with increasing HNO_3 concentration. The main liquid radiolytic products are CH_3 COOH and HNO_2, and their concentrations are(3.40–19.7) 9 10~(-2) and(0.200–4.80) 9 10~(-3)-mol L~(-1), respectively, which increase with the HNO_3 concentration. Since a significant concentration of HNO_2 is present in the irradiated AHA-HNO_3 solution, a holding reductant must be used to destroy HNO_2 and stabilize Pu(Ⅲ) and Np(Ⅴ) when AHA is applied for the separation of Pu and Np from U.     

Underlying reasons for waxy rice flours having different pasting properties

The underlying reasons for three waxy rice varieties, Yang-fu-nuo (Y), Su-yu-nuo (S), and Guang-ling-xiang-nuo (G), having different flour pasting properties were examined. The pasting properties of the isolated waxy rice starches did not correlate with those of the corresponding waxy rice flours. Examining the pasting properties of the flours in 0.5 mM AgNO₃ solution, treated with dithiothreitol and protease, suggested that rice protein and amylase activity were the main causes of the pasting property differences among the rice starches and flours. Starch isolated from Y flour had a larger proportion of A and B₁ chains, longer average chain length and longer exterior chain length, which explained its higher gelatinisation temperature, higher pasting consistency, greater extent of retrogradation, and the firm texture of cooked Y rice.