排序方式: 共有46条查询结果,搜索用时 15 毫秒
11.
顶空吸附萃取-气相色谱法分析小麦中部分风味物质 总被引:1,自引:0,他引:1
采用顶空吸附萃取法(headspace sorptive extraction, HSSE)建立了小麦中部分风味物质的分析方法。以硅橡胶为原料,采用溶胶-热空气硫化法,在模具中定型制得硅橡胶萃取棒。萃取棒的硅橡胶层体积约为87 μL,热稳定性好,耐热温度达到390 ℃。萃取棒吸附的风味物质经自制热解吸装置热脱附,被吹扫进入气相色谱仪进行分析。考察了萃取温度及时间、相比、热解吸条件对该方法萃取效率的影响。在优化条件下分析小麦粉标准样品,结果表明:方法的线性关系良好(r>0.9979),检出限为0.09~1.00 μg/kg,标准物质的平均添加回收率为95%~121%,相对标准偏差在2.2%~7.8%之间。对小麦粉实际样品进行分析,采用外标法得到了7种风味物质的绝对含量。该方法简便快捷,检出限低,适用于小麦中风味物质的快速定量分析。 相似文献
12.
Xiaojing Zhang Zhigang Shen Chujiang Cai Xiaozheng Yu Jun Du Yushan Xing Shulin Ma 《Particuology》2012,10(4):480-486
Superfine spherical fire-extinguishing powder, ammonium dihydrogen phosphate (ADP, NH4H2PO4), was prepared by spray drying and modified in situ with methyl hydrogen silicone oil (MHSO) emulsion and the fluorinated surfactant FK-510. The influences of the MHSO mass ratio on the hydrophobicity, surface composition, surface morphology, dispersion and particle-size distribution of the NH4H2PO4 were studied, and the influence of the drying air temperature on the decomposition of the NH4H2PO4 was also researched. The results indicate that the MHSO and FK-510 congregate on the particle surfaces and then form a hydrophobic shell. This shell improves the particle hydrophobicity and leads to a fine dispersion of the particles. During the process of preparing the precursor solution, 3 wt% (based on the weight of NH4H2PO4) was chosen as the optimum value of the MHSO mass ratio. During the spray drying, a low absolute humidity of the air should be maintained, and it is very important to keep the exit-air temperature below 100 °C to avoid decomposition. 相似文献
13.
14.
Xia Yang Li Jiaojiao Wang Hongjie Ye Zhangjun Zhou Xiaozheng Huang Hui Gan Yongping Liang Chu Zhang Jun Zhang Wenkui 《Journal of Solid State Electrochemistry》2019,23(2):519-527
Journal of Solid State Electrochemistry - In this work, a series of rationally designed hybrid membranes composed of poly(vinylidene fluoride) (PVDF) as polymer matrix and silica nanoparticles... 相似文献
15.
16.
Linjie Zhu K. A. Narh Xiaozheng Geng 《Journal of Polymer Science.Polymer Physics》2001,39(20):2461-2468
Particle‐dispersed melting is a complex but important melting mechanism in the corotating twin‐screw extruder. In this study, the complex multi‐particle‐dispersed system was simplified into a single‐particle melting model. The finite‐difference method was introduced to solve this problem. The simulation results show that the melting of a particle may involve two steps: the heating stage and melting stage. The heating time and melting time depend on solid concentration, initial melt and solid temperature, and shear rate. Calculations indicate that high solid concentration and solid temperature, low melt temperature and shear rate will result in a more uniform temperature distribution after polymer melting. The model offers valuable information for designing the melting zone in a corotating twin‐screw extruder, especially at high screw speed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2461–2468, 2001 相似文献
17.
生物碱类天然产物通常具有复杂多样的化学结构和广泛的生物活性,因此备受生物学、化学、药学领域研究者的关注。微生物是仅次于植物的生物碱类天然产物重要来源,微生物尤其是放线菌产生的众多次生代谢产物中,也包括很多生物碱。对放线菌来源生物碱的骨架结构和药效基团生物合成研究,不仅能够丰富人们对天然产物结构形成原理的理解,还可以为运用合成生物学技术人工合成此类化合物提供重要的遗传元件。本文从模块化生物合成和非模块化生物合成两种方式,综述放线菌来源生物碱的生物合成基因簇、途径及其酶催化反应过程。 相似文献
18.
Vuong Phan Tu He Xiaozheng Thong Duong Viet 《Journal of Optimization Theory and Applications》2021,190(3):915-930
Journal of Optimization Theory and Applications - We investigate the convergence properties of a projected neural network for solving inverse variational inequalities. Under standard assumptions,... 相似文献
19.
The electromagnetic shielding of Ni films deposited on cenosphere particles by magnetron sputtering method 总被引:2,自引:0,他引:2
Ni-coated cenosphere particles were successfully fabricated by an ultrasonic-assisted magnetron sputtering equipment. Their surface morphology and microstructure were analyzed using field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). FE-SEM results indicate that the Ni films coated by magnetron sputtering are uniform and compact. Ni film uniformity was related with the sputtering power and a large uniform film could be achieved at lower sputtering power. XRD results imply that the Ni film coated on cenospheres was a face-centered cubic (fcc) structure and the crystallization of film sample increases with increasing the sputtering power. The electromagnetic interference (EMI) shielding effectiveness (SE) of Ni-coated cenosphere particles were measured to be 4-27 dB over a frequency range 80-100 GHz, higher than those of uncoated cenosphere particles. The higher sputtering power and Ni film thickness are the higher EMI SE of the specimens. Ni-coated cenosphere particles are most promising alternative candidates for millimeter wave EMI shielding due to their lightweight, low cost, ease of processing, high floating time, good dispersion and tunable conductivities as compared with typical electromagnetic wave countermeasure materials. 相似文献
20.
宽带准连续光纤激光在周期极化铌酸锂中倍频特性的研究 总被引:3,自引:2,他引:1
双包层光纤激光器和非线性光学材料(如周期性极化的铌酸锂晶体,PPLN)相结合,开辟了实用性非线性光学器件的一个新领域。研究了准相位匹配周期性极化反转铌酸锂晶体对宽带准连续光纤激光倍频的温度特性和频谱特性。在理论上,从准相位匹配相位失配关系出发,推导了晶体温度与抽运源中心波长的关系以及温度响应带宽,并和已报道实验结果进行了比较,二者符合得很好。此外,还推导了倍频周期极化铌酸锂晶体对抽运基频光源的响应谱线带宽。在实验上,采用长度20mm,极化周期6.5μm,厚度0.5mm的周期极化铌酸锂晶体光纤激光器准连续宽带输出进行了倍频,获得了在不同控制温度下的倍频光光谱,并对此进行了详细分析。 相似文献