FLASH PYROLYSIS OF BIOMASS PARTICLES IN FLUIDIZED BED FOR BIO-OIL PRODUCTION

Biomass utilization could relieve the pressure caused by conventional energy shortage and environmental pollution. Advantage should be taken of the abundant biomass in China as clean energy source to substitute for traditional fossil fuels. At present, flash pyrolysis appears to be an efficient method to produce high yields of liquids that could either be directly used as fuel or converted to other valuable chemicals. Experiments were carried out of pyrolyzing biomass particles in a hot dense fluidized bed of sand to obtain high-quality bio-oil. Among four kinds of biomass species adopted in our experiment, Padauk Wood had the best characteristics in producing bio-oil. GC-MS analysis showed bio-oil to be a complex mixture consisting of many compounds. Furthermore, an integrated model was proposed to reveal how temperature influences biomass pyrolysis. Computation indicated that biomass particles underwent rapid heating before pyrolysis.     

The Mechanisms of Oxygen Accelerated Low-Temperature Bonding by Ag Nanoparticles

Low-temperature bonding (≤300 ^o C) using Ag nanoparticles (Ag NPs) is considered to be the new generation of bonding technology in power electronics. The oxygen-accelerated sintering has been observed by many researchers which is attributed to the decomposition of organics covered on Ag NPs. In this work, organic-free Ag NPs are fabricated to eliminate the influence of organics, and it is found that the accelerated bonding process by oxygen is strongly correlated to the self-confined amorphous Ag-O compound shell on the surface of Ag NPs. In experiments, the sintering process is apparently accelerated by the elevating oxygen content, and the amorphous shell is observed after sintering, which do not grow thicker even in pure oxygen ambient for a long time while performing active chemical evolutions. In simulations, the results match well with the experiments and indicate that the amorphous shell performed the dynamic oxidation and decomposition process. This dynamic equilibrium is caused by the instability of silver oxides, which would enable the amorphous shell to activate the mobility of the surface mass flow and promote the surface diffusion. The shear strength of SiC chip increased by 354% when bonding in pure oxygen, targeting a broad variety of applications in electronic packaging.     

大规模集成光波导时域有限元差分法仿真的子域合成法

用时域有限元差分的子域合成法(Synthetic subdomain method of FDTD)对大规模的光波导模拟,把仿真的光波导划分成两个或多个区域,在不影响仿真精度的条件下,删除对仿真对象影响不大的区域,并相应改变吸收边界条件进行时域有限元差分法数值模拟,考查光的传播和损耗状况,并与常规方法的运算结果相比较,结果一致且不影响计算精度。与常规方法相比,两段子域合成法所占内存约为前者的55%,时间约为前者的60%,三段子域合成法所占内存约为前者的31%,时间约为前者的28%,可见子域合成法比常规方法更有利于应用于大规模集成光波导的数值模拟仿真,对节省硬件及时间资源具有实际意义,提高工作效率。     

有限束宽下光栅对压缩的理论研究

给出了入射脉冲为有限束宽时,光栅对压缩的理论模型。并据此分析了脉冲高斯光束单次及两次通过光栅对时的变换特性,以及高阶色散对脉冲压缩的影响。     

小型化外腔可调谐THz参量振荡器

基于LiNbO3晶体垂直表面输出技术,设计了一台小型化外腔THz参量振荡器。利用小型化灯1064 nm脉冲激光器泵浦MgO:LiNbO3,通过优化设计三波非共线相位匹配的光学参量振荡腔结构,实现THz垂直晶体表面输出,减少LiNbO3晶体对THz波的吸收,提高了THz波输出光束质量。当在泵浦光能量为128 mJ、重复频率为10 Hz时,获得THz波的调谐范围为0.69~3.01 THz,在1.6 THz处获得THz波最大平均功率为10.8 W,脉冲宽度为10 ns,对应THz波能量转换效率为8.4310-6。     

One‐pot synthesis of carbon dots@ZrO2 nanoparticles with tunable solid‐state fluorescence

In recent years, fluorescent carbon dots (CDs) have been developed and showed potential applications in biomedical imaging and light‐emitting diodes (LEDs) for their excellent fluorescent properties. However, it still remains a challenge to incorporate fluorescent CDs into the host matrix in situ to overcome their serious self‐quenching. Herein, a one‐pot hydrothermal method is used to prepare nano‐zirconia with CDs (CDs@ZrO₂) nanoparticles. During the reaction, CDs and nano‐zirconia are generated simultaneously and connected with silane coupling agent. The CDs@ZrO₂ nanoparticles exhibit tunable emission wavelength from 450 to 535 nm emission by regulating the content of citric acid in the feed. The quantum yield of the CDs@ZrO₂ is up to 23.8%. Furthermore, the CDs@ZrO₂ nanoparticles with regulable fluorescence emission can be used for the fluorescent material to prepare white LEDs. The prepared LED has significant white light emission with color coordinates of (0.30, 0.37) and its color rendering index (CRI) is 67.1. In summary, we have developed the solid‐state CDs@ZrO₂ nanoparticles with tunable emission by a valuable strategy, that is, one‐pot method, for white LEDs.     

Maximum Principle for Markov Regime-Switching Forward–Backward Stochastic Control System with Jumps and Relation to Dynamic Programming

This paper presents a sufficient stochastic maximum principle for a stochastic optimal control problem of Markov regime-switching forward–backward stochastic differential equations with jumps. The relationship between the stochastic maximum principle and the dynamic programming principle in a Markovian case is also established. Finally, applications of the main results to a recursive utility portfolio optimization problem in a financial market are discussed.     

高效离子交换色谱-电化学检测法测定药物合成中间体中的6-磷酸甘露糖

在制备6-磷酸甘露糖过程中,将6-磷酸甘露糖与磷酸根杂质分开是纯化过程和建立质量标准的重要环节。本文建立了6-磷酸甘露糖和磷酸根的离子色谱分离-电化学检测方法。样品经溶解、过滤后进行色谱分析,以IonPac AG18离子交换柱(50 mm×4 mm)为保护柱,在Ionpac AS18离子交换色谱柱(250 mm×4 mm)上分离,以25 mmol/L氢氧化钾溶液为流动相,等度淋洗,流速1.0 mL/min,安培检测器和电导检测器串联检测,外标法定量。先使用安培检测器检测,在碱性条件下,6-磷酸甘露糖在安培检测器上被选择性检出;后使用电导检测器检测,经ASRS型抑制器抑制背景电导后,6-磷酸甘露糖和磷酸根同时被电导检测器检出,二者分离度良好。采用安培检测器检测时,进样量为25 μL, 6-磷酸甘露糖的线性范围为0.06～10.00 mg/L,相关系数为0.9998,回收率为92.1%～103.1%,相对标准偏差均小于3%,检出限(以信噪比为3计)为0.02 mg/L。该方法灵敏度高,无杂质干扰,前处理简便,可用于原料药合成中间体的检测,结果令人满意。     

毛细管离子色谱法测定酒和饮料中阳离子

建立了毛细管离子色谱测定酒、饮料等样品中阳离子的分析方法。使用毛细管离子色谱柱IonPac CS12A(250 mm×0.4 mm, 8 μm),以甲基磺酸淋洗液发生器(EGC-MSA)产生18 mmol/L的甲基磺酸为流动相,进样量0.4 μL,在流速0.01 mL/min的条件下,采用自循环抑制电导检测的方法对啤酒、葡萄酒、白酒、果汁及奶茶等样品中的阳离子含量进行检测。结果表明,毛细管离子色谱法能满足阳离子含量的测定要求,系统稳定不易堵,在灵敏度方面优于常规离子色谱系统。该方法能够快速、准确地测定酒、饮料等样品中的5种阳离子(钠、铵、钾、镁和钙),回归方程的相关系数在0.9997以上,实际样品的加标回收率为95.2%～103.3%。该方法具有灵敏度高,操作简单,环境友好的特点。