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排序方式: 共有1250条查询结果,搜索用时 31 毫秒
31.
Xiaohuan Miao Lijun Xu 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2018,35(7):1257-1265
Olaquindox, carbadox, and cyadox are chemically synthesised antibacterial and growth-promoting agents for animals. At high doses they may exert mutagenicity and hepatic and adrenal toxicities in animals. Regrettably, these substances are frequently abused or misused when added into animal feeds. Thus, developing a sensitive and reliable method for simultaneous determination of olaquindox, carbadox, and cyadox in different kinds of animal feeds is crucially important for food safety monitoring. In this paper we optimised instrumental conditions, extraction solvents, solid phase extraction cartridges, and pH of the loading solvents on the Oasis HLB cartridge. Under the optimal conditions, mean recoveries ranged from 74.1 to 111%, and intra-day and inter-day variations were lower than 14.6% and 10.8%, respectively. The limits of quantification for olaquindox, carbadox, and cyadox were 0.05 mg kg?1, 0.10 mg kg?1, and 0.025 mg kg?1, respectively. The proposed method uses ultra-performance liquid chromatography tandem mass spectrometry and is sensitive and reliable for the simultaneous determination of olaquindox, carbadox, and cyadox in three kinds of animal feeds (specifically, mixed feed, concentrated feed, and additive premixed feed). This method has good precision, high sensitivity, and good reproducibility, and thus it can be used for convenient and accurate determination of olaquindox, carbadox, and cyadox in different kinds of animal feeds. 相似文献
32.
论述了超高加筋土挡墙的设计过程与建造及挡墙的变形特征。较大墙高宜采用加筋土挡墙,其对地基的适应性强,占地少,建造周期短。行洛坑钨矿原矿运输铁路跨越深沟谷,与栈桥相比较后,采用了加筋土挡墙方案,设计建造了二级30 m超高加筋土挡墙作为路基,1 a累计最大水平位移16~83 mm,最大沉降24~115 mm,建成5 a来运行正常。 相似文献
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作为21世纪最具潜力的绿色金属材料,镁合金在航空航天、轨道交通、3C、纺织印刷、体育器材等领域得到越来越广泛的应用。本文研究了产业化生产的超宽镁合金中厚板和薄板的组织和性能,结果发现,通过调整热处理制度,可以获得再结晶等轴组织,中厚板性能可满足ASTMB90/B90M-2007标准要求,薄板性能可满足GBT5154—2010标准要求。 相似文献
34.
Sophisticated portable infrared imagers developed for surveillance, reconnaissance, targeting and navigation play a vital role in the modern tactics used for carrying out military and antiterrorist operations. Their superior performance relies on novel optronic technologies and maintaining the infrared focal plane arrays at cryogenic temperatures using close cycle mechanical Stirling cryogenic coolers.Such coolers are well known sources of high-frequency interference contaminating the image signal and causing essential degradation in the overall imagery performance. This phenomenon is generally referred to as microphonics, which mostly manifests itself at the resonant frequencies of sensitive mechanical components of infrared packages.The ruggedizing of these components involves stiffening and dampening which are, evidently, not the best solutions to implement inside, say, an evacuated envelope, where the issues of added heat load, thermal mass, ageing, vacuum contamination due to outgassing are of the primary concern.The paper examines the idea of using externally mounted wideband dynamic absorbers for suppressing the above resonant responses and associated microphonic noise. The suggested analytical model relies on a set of complex frequency response functions experimentally captured on the original infrared package. The optimised dynamic absorber yields about a tenfold suppression of the resonant responses and a threefold attenuation of the overall RMS level of microphonic noise. The results of the analytical prediction are in fair agreement with experimental data. 相似文献
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随着社会安全意识的提高,政府、企业集团客户视频监控传输类需求呈现快速的上升趋势,尽管视频传输业务在有线通信资源满足的条件下已经有较为成熟的解决方案,但是在无法铺设有线管道或现有管线资源无法满足的场景如河坝、山区等仍然面临很大的设计实施困难,尚未形成有效的解决措施。针对以上问题,结合TD-LTE无线通信的传输特点,研究了通过TD-LTE无线通信方式实现集团客户视频传输业务的方法,并结合TD-LTE无线通信的特点给出了相应的解决方案。 相似文献
37.
From supercritical carbon dioxide to gas expanded liquids in extraction and chromatography of lipids
Charlotta Turner 《Lipid Technology》2015,27(12):275-277
Analytical‐scale extraction and chromatography of oils, fats and other liposoluble compounds can be achieved by using supercritical carbon dioxide as a solvent. Since the 90's when supercritical fluid chromatography (SFC) was a hot topic, this technology has developed into a robust, modern analytical technique that uses any proportions of compressed CO2 mixed with an organic solvent. Supercritical fluid extraction (SFE) on the other hand is only recently starting to reform in a similar way, towards the use of more robust extraction system and enabling mixing of compressed CO2 with larger proportions of organic solvents. In this Feature article, the development of SFC and SFE into what options we have today is described, including the latest trend of using CO2‐expanded liquid (CXL) as extraction solvent for lipids. 相似文献
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39.
为了解决弯管内表面精密抛光困难的问题,设计了一种弯管内表面自动抛光装置。该抛光装置总体结构由抛光头、绕线机构、传动机构、夹紧机构以及连接机构等部分组成。整个装置与圆截面弯管零件连成一容腔,可向零件内腔充入用于对零件内表面进行抛光加工的抛光液,控制器控制步进电机带动两端的绕线装置工作,从而实现对弯管内表面的精密抛光加工。利用软件Fluent进行流体仿真,仿真结果表明:流体出口的流速很高,使旋转喷射抛光作用发挥得较好,能够很好地对圆形截面弯管内表面进行抛光加工。 相似文献
40.
《CIRP Annals》2019,68(1):385-388
A novel semi-active joint for connecting mechanical (i.e., sliding/rolling) bearings or guideways to an ultra-precision motion stage is presented. The semi-active joint enables the benefits of bearing/guideway friction on in-position stability while avoiding its adverse effects on rapid ultra-precision positioning. The joint is equipped with solenoids that switch its stiffness from low, during settling, to high once the stage gets into position. A two-step scheme is implemented to mitigate adverse effects of switching on positioning performance. Experiments demonstrate up to 81% and 60% improvements in settling time and in-position stability, respectively, compared to cases with solely low- or high-stiffness joints. 相似文献