共查询到20条相似文献,搜索用时 172 毫秒
1.
2.
3.
4.
5.
6.
7.
基于美国环境保护局(U.S.Environmental Protection Agency,USEPA)1631方法,自制双柱热脱附装置,以国产AF-610B型原子荧光仪为检测器,搭建吹扫-金柱捕集-(双柱)热脱附-冷原子荧光系统,用于测定环境样品中的总汞。对吹扫流速、吹扫时间和尾吹流速等实验参数进行了优化。双柱热脱附装置的脱附效率为99%—100%。在最优测定条件下,仪器检出限为5.0pg,海水测定的方法检出限为0.50ng/L,土壤、沉积物和红树样等固体样品测定的方法检出限为1.0ng/g。采用基底加标回收率法和参考样,验证了该系统的准确可靠性。结果表明,海水、土壤、沉积物和红树植物组织等样品的基底加标回收率均符合USEPA的限定范围,土壤参考样(ESS-4)和近海海洋沉积物参考样(GBW07314)的测定结果在参考值的可控范围内。该系统可满足环境样品中总汞测定的要求。 相似文献
8.
9.
吹扫捕集-GC-MS法测定木瓜金宝萝青101中的香气成分 总被引:2,自引:0,他引:2
采用吹扫捕集法提取、富集木瓜金宝萝青101中的香气成分,经GC-MS分离与分析,共鉴定出56种化合物,其含量占挥发性成分的99.957%,主要香气物质为酯类(70.009%),还包括醇类、醛类及少量的烃类和其他化合物.其中,主要成分为乙酸乙酯(22.865%)、乙醇(18.010%)、丁酸乙酯(12.704%)、丙酸乙酯(8.754%)、丁酸-2-甲基-乙酯(8.716%)、己酸乙酯(6.275%)等,这些物质的共同作用形成了木瓜独特的香味. 相似文献
10.
在南方某癌症高发县5个乡镇10个村进行布点取样,采集深层地下水与浅层地下水共计20个水样。采用吹扫捕集与气相色谱-质谱联用方法测定水样中13种挥发性有机物(VOCs),检出二氯甲烷、三氯甲烷、苯和四氯化碳4种VOCs,其浓度分别为0.36—13.52、0.41—18.71、0.57—11.75μg/L和1.56—214.62μg/L。1个水样中苯和16个水样中四氯化碳超过GB 5749-2006规定的限值。采用优化的USEPA风险评价模型,对VOCs进行人体健康风险评价,其非致癌风险指数0.0073—0.7100,致癌风险水平1.98×10-6—1.99×10-4,全部水样的致癌风险水平超过10-6水质监控值,1个水样的致癌风险水平超过10-4的可接受水平。四氯化碳对非致癌风险指数和致癌风险水平贡献最大。 相似文献
11.
A.S. Eggeman A.K. Petford-Long P.J. Dobson J. Wiggins T. Bromwich R. Dunin-Borkowski T. Kasama 《Journal of magnetism and magnetic materials》2006
Nanoparticles of cobalt were produced by direct reduction in aqueous solution. These were subsequently coated in silica by a very slow hydrolysis reaction. Electrostatic and magnetic forces between the nanoparticles led to ordered structures forming, which were analysed by high resolution transmission electron microscopy. SQUID magnetometry showed that the nanoparticles were ferromagnetic with an additional magnetic signal from highly disordered surface states. Off-axis electron holography of the structures was undertaken and gives evidence for the mechanism by which the structures form. 相似文献
12.
以S-K和V-W模式生长ZnCdSe和ZnSeS量子点及其特性 总被引:1,自引:1,他引:0
用低压金属有机化学气相外延(LP-MOCVD)技术,以Stranski Krastanow(S-K)模式,在GaAs衬底上生长了CdSe和ZnCdSe量子点(QDs)。用原子力显微镜(AFM),观测到了外延层低于临界厚度时,CdSe自组装量子点的形成过程,并把其机理归结为表面扩散效应和应变弛豫效应的联合作用。依据理论计算外延层临界厚度值的指导,用LP-MOCVD技术在GaAs衬底上生长了ZnCdSe量子点,详细观测了ZnCdSe量子点的形成和演变,这些过程可用Ostwald熟化过程和形成过程的联合作用来解释。用LP-MOCVD技术,以Volmer Weber(V-W)模式,在GaAs衬底上生长了ZnSeS量子点,随着生长时间的增加,量子点尺寸增大,而量子点密度减少,这些现象可用表面自由能来解释。 相似文献
13.
14.
本文采用随机数的方法,发展了一种普适的多层膜设计方法,这种方法除可设计一般的周期多层膜,更重要的是它可以根据选定的评价因子,设计不同要求的非周期多层膜。用磁控溅射方法完成软X射线多层膜制备,X射线衍射、卢瑟福背散射、俄歇电子谱和反射率的相对测试用来表征多层膜结构和特性,所得结果说明多层膜的结构完整,周期参数正确。用离子束溅射方法成功地制备了有一定反射率和透过率的软X射线半反半透分束镜;分析了Ag和Zr衰减膜中的杂质含量与分布及其对衰减膜特性的影响,并对衰减系数进行了修正,为实验提供优质的衰减膜。 相似文献
15.
16.
17.
Songül Akbulut Özen Uğur Çevik Halim Taşkın 《Isotopes in environmental and health studies》2019,55(1):92-109
Radon (222Rn) measurements were conducted in the Pileki Cave with Radim 3A Active Radon Monitor equipment. Measurements were also done with the passive sampling method with CR-39 nuclear track detectors by exposing them for three months in the cave. Radon concentrations obtained from the active and passive sampling methods showed that, firstly, the concentrations inside the cave measured by the latter method differed greatly due to high humidity levels up to 88%. The total inside radon exposure dose equivalent people were subjected to was estimated to be 19?µSv a?1 for visitors and 24,065?µSv a?1 for guides. The gamma absorbed dose rates were determined for inside and outside the cave. The dose rates were calculated by means of using the 226Ra, 232Th and 40K activity concentrations and by means of real-time measurements. The gamma absorbed dose rates were found to be much higher than the value of 55?nGy?h?1 given by UNSCEAR. In addition, the mineralogical compositions and elemental analyses of samples taken from the cave were determined by XRD and WD-XRF methods. 相似文献
18.
Multiphase Polymeric Materials for Rapid Prototyping and Tooling Technologies and Their Applications
《Composite Interfaces》2013,20(2-3):257-271
Rapid prototyping (RP) and tooling (RT) are the technologies for quickly fabricating functional components and tooling inserts directly from CAD data by selectively adding material layer by layer. In this paper, multiphase polymeric materials for RP and RT technologies and their applications, which are developed by the Rapid Manufacturing (RM) Center of Huazhong University of Science and Technology (HUST) in China, were introduced. Selective laser sintering (SLS) is a powder-based RP process. Multi-types of multiphase polymer materials for SLS process were successfully developed in the RM center, and the SLS components were formed from these materials by using the commercial SLS machines HRPS series for various applications. High impact polystyrene (HIPS)/wax blend SLS parts were used as lost patterns for the investment casting process to make complex metal parts rapidly; nylon-12/organically modified rectorite and nylon-12/nanosilica composite powders were used to fabricate functional parts, which showed higher thermal and mechanical properties than neat nylon-12 SLS parts. As a RT application, Fe/epoxy composite tooling inserts were rapidly fabricated by SLS and post-processing. Stereolithography (SLA) uses photocurable resins to rapidly manufacture components with high accuracy and mechanical properties. A freeradical and cationic mixed-type radiation curable composite resin was also successfully developed, and SLA parts without obvious distortion were built on the SLA machines HRPL series from this hybrid resin, successfully and efficiently. 相似文献
19.
Auditory intensity and frequency resolution were studied in three paradigms under masking conditions. Absolute identifications of single stimuli (one-interval paradigm) and 2IFC judgments of fixed- and roving-level pairs of stimuli (two-interval paradigm) were obtained from the same experienced observers. Judgments were made under optimal (no mask) conditions, in the presence of a broadband noise mask (simultaneous mask), and when the stimulus(i) to be judged were either preceded (forward mask) or followed (backward mask) by a broadband noise mask. Substantial masking of intensity resolution was found in all mask conditions. Only a simultaneous mask affected frequency resolution. In the no mask condition, performance was best for fixed-level (or frequency) 2IFC discrimination, followed by roving-level (frequency) 2IFC, and finally absolute identification. These differences were maintained under masking for frequency resolution, but not for intensity resolution. The results are discussed in terms of the Braida and Durlach (1988) model of intensity resolution. A similar model is suggested for frequency resolution with differences suggested by the differences in neural coding of sound intensity and frequency. 相似文献
20.
以蛇纹石这一中国传统的玉材为对象,旨在通过微量元素含量分析来探索古代蛇纹石玉器原料的可能来源。采用无损的外束质子激发X射线荧光技术(PIXE)对来自中国几个典型矿区的蛇纹石样品主量元素和微量元素进行了分析。同时也采用有损的电感耦合等离子体原子发射光谱技术(ICP-AES)对这些蛇纹石样品的微量元素含量进行了比较分析。结果表明,两种分析方法所获取的蛇纹石微量元素含量趋势具有一致性,说明PIXE无损分析技术可以应用于蛇纹石的微量元素分析研究。讨论了蛇纹石的微量元素含量与地质成因之间的关系,这些蛇纹石的微量元素含量存在明显的差异,这种差异可以用来区分不同地质成因的蛇纹石。Ⅰ型地质成因的蛇纹石中微量元素中Ni含量较低,且几乎不含Cr和Co,而Ⅱ型地质成因的蛇纹石中则含有较高微量元素的Cr,Co和Ni。采用PIXE技术分析了来自浙江、江苏、河南、安徽和湖北等省出土的新石器时代至战国时期(4585 BC—221 BC)14个遗址或墓葬出土的18件蛇纹石玉器的化学成分,通过与两种地质成因类型蛇纹石的微量元素比较分析,初步推测了这些蛇纹石玉器原料的可能来源。以蛇纹石微量元素含量与地质成因类型之间的关系来探索古代蛇纹石玉器玉料可能的来源是一种有益的尝试。 相似文献