共查询到20条相似文献，搜索用时 46 毫秒
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张文旭张铭昊蒋伊琳陈涛 《实验室研究与探索》2023,(4):5-9
基于Zedboard开发板,以雷达梳状谱干扰波形合成设计为出发点,提出了一种基于随机相位多频点循环叠加的梳状谱干扰波形设计方法,使用单个DDS IP核生成完成叠加任务,并通过Zynq-7000系列FPGA对该方法进行编程设计与算法实现。同时使用MATLAB仿真与FPGA硬件实现对实验效果进行测试,结果表明,该实验能够成功生成宽带梳状谱干扰波形,干扰频率范围为0~600 MHz,有4、8、16三种干扰频点模式,同时其干扰频点误差不超过0.1%,由此验证了方法的有效性。实验中提出以m序列作为干扰信号的相位控制,改善时域叠加条件下梳状谱干扰信号峰均比。该方案可用于实际被动侦察干扰设备,为其提供一种遮盖式干扰方式。 相似文献
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用循环伏安法研究了在不同的电解质溶液及不同扫速下,多壁碳纳米管修饰电极对抗坏血酸(AA)的电催化作用。实验表明在MWCNT电极上,AA的氧化峰电位负移,氧化峰电流显著增加,AA的电极过程呈现扩散控制的特征,且AA浓度在1.0×10-5-5.0×10-1moL·dm-3范围内,其浓度与峰电流有良好的线性关系,检测下限达1.0×10-6moL·dm-3,一些常见物质对其测定无干扰。 相似文献
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目的考察样品浓度对凝胶色谱法低分子透明质酸分子量的影响。方法色谱条件为:0.71%Nacl溶液作流动相,流速1ml/min;柱温35℃;进样量20μl。在此条件下,改变标准品及样品的浓度。结果实验结果表明:浓度对多糖标准品的色谱峰形影响不大,分子量较低的标准品浓度越低,基线不平稳造成的干扰越明显;浓度对分子量较低的透明质酸钠样品的色谱峰形影响不大;浓度对分子量较高的透明质酸钠样品的色谱峰形影响很大,浓度越小,峰形越好。改变浓度,对分子量的测定结果基本没有影响。结论重均分子量高于1.7×105透明质酸钠,采用的浓度应低于0.1%。样品分子量越大,采用的浓度应越低。 相似文献
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探讨了双色素饮料中两种色素在各自吸收峰干扰较少的情况下,不进行色素的分离,对两种色素同时进行测定的分析方法.结果表明,本法测定柠檬黄和亮蓝的相对标准偏差分别为0.8%和3.3%,回收率分别为99.5%和100.3%,方法准确可靠,而且不需分离,简便快速. 相似文献
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在pH6～ 8范围内 ,PAN -S与Ni(Ⅱ )形成 1∶1的红色络合物 ,最大吸收峰在 5 35nm ,镍量在 0～ 2 5 μg/2 5ml符合比尔定律 ,摩尔吸光系数为 2 .84× 10 4。掩蔽干扰离子后 ,可以直接测定钢铁中的镍。 相似文献
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《实验室研究与探索》2016,(1)
验证了硝酸根最大吸收峰波长能否作为总氮测定波长及不同波长对总氮测定结果的影响。结果表明,通过波长扫描0.08~2.8 mg/L硝酸根,发现最大吸收峰并非在220 nm,而出现在200~210 nm。采用碱性过硫酸钾法测定水体中的总氮含量,200~210 nm存在盐酸吸收峰干扰,但在211~220 nm波长范围内均有良好的线性关系。不同波长对加标回收率、重现性、精密度及方法检出限检验影响不大。随着测定波长的减小,标准曲线的斜率、相关系数R、摩尔吸光系数依次增加。211 nm处摩尔吸光系数达6.8×103(mol/L)-1/cm,远高于220 nm。同时,211 nm处标准曲线拟合斜率K更大。在实际地表水的测定中,以最大吸收峰(211nm)处测定总氮,与国标220 nm处测定相比较,结果并无明显差异。 相似文献
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目的 考察样品浓度对凝胶色谱法低分子透明质酸分子量的影响。方法 色谱条件为：O．71％Nacl溶液作流动相，流速lml／min；柱温35℃；进样量20μ1。在此条件下，改变标准品及样品的浓度。结果实验结果表明：浓度对多糖标准品的色谱峰形影响不大，分子量较低的标准品浓度越低，基线不平稳造成的干扰越明显；浓度对分子量较低的透明质酸钠样品的色谱峰形影响不大；浓度对分子量较高的透明质酸钠样品的色谱峰形影响很大，浓度越小，峰形越好。改变浓度，对分子量的测定结果基本没有影响。结论重均分子量高于1、7×105透明质酸钠，采用的浓度应低于0．1％。样品分子量越大，采用的浓度应越低。 相似文献
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利用循环伏安法(CV)以中性红为聚合物直接制备修饰电极,同时对亚硝酸盐在中性红修饰玻碳电极上的电化学行为进行研究.结果表明:亚硝酸根在中性红修饰电极上的氧化峰电位与在玻碳电极上的氧化峰电位相比左移了164 m V,这充分说明了中性红修饰电极对亚硝酸根的氧化具有很好的电催化性能.利用差分脉冲伏安法(DPV)研究了亚硝酸根的平均峰电流值与浓度之间的关系,检出限可达5.18×10-7 mol/L(信噪比为3),回收率为94.3%～104.5%.该修饰电极不受外界杂质干扰、制备方法简单、灵敏度高,在测定食品中的亚硝酸盐含量时效果良好. 相似文献
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紫外分光光度法测定果蔬中的维生素C 总被引：21，自引：0，他引：21
李军 《河北职业技术师范学院学报》2000,14(1):41-44
还原型维生素Ｃ在２４３．８ｎｍ下有最大吸收峰,在０～４５０μｇ／ｍＬ范围内具有良好的线性。本研究以Ｃｕ＾２＋作催化剂,利用溶解氧,将在２４３．８ｎｍ处有最大吸收的还原型维生素Ｃ选择性的氧化为２４３．８ｎｍ处无吸收峰的氧化型维生素Ｃ,实现了对样品中各种紫外干扰成分的本底校正,建立了一种测定果蔬中还原型维生素Ｃ的新方法。运用该方法实际测定了草莓、西红柿等样品的还原型维生素Ｃ的含量,回收率在９７．６％～ 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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罗艳萍 《读与写:教育教学刊》2008,5(6)
The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity. 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
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Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
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Richard Denner 《海外英语》2007,(4):14-15
Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose. 相似文献
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Given a graph G,a subgraph C is called a clique of G if C is a complete subgraph of G maximal under inclusion and |C|≥2. A clique-transversal set S of G is a set of vertices of G such that S meets all cliques of G. The clique-transversal number, denoted as TC (G), is the minimum cardinality of a clique-transversal set in G. The clique-graph of G, denoted as K (G), is the graph obtained by taking the cliques of G as vertices, and two vertices are adjacent if and only if the corresponding cliques in G have nonempty intersection. Let F be a class of graphs G such that F={G|K(G) is a tree}. In this paper the graphs in F having independent clique-transversal sets are shown and thus TC (G)/|G|≤1/2 for all G ∈ F. 相似文献
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Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献