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排序方式: 共有117条查询结果,搜索用时 15 毫秒
21.
YU Xianglin QU Hao HU Qihui HOU Kun YAN Yushi WU Dan ZHANG Pian LI Junbo 《武汉大学学报:自然科学英文版》2014,19(2):129-136
A rhodamine-benzimidazole conjugate(RB) as a probe was investigated.UV-Vis analysis showed that a strong absorption band at 552 nm was formed with the addition of Cu~(2+),while other transition metal ions induced a little more absorption.The absorption value of RB solution at 552 nm has a linear correlation with Cu~(2+) concentration between 35-70 μmol/L;the detection limit reached 6.82×10~(-2) μmol/L,which is lower than the settled limitation for copper in the drinking water(~30 μmol/L) standardized by World Health Organization(WHO).Moreover,FL analysis showed that only Fe~(3+) could induce large fluorescence intensity enhancement at 582 nm;other common metal ions including Cu~(2+) cannot induce the enhancement.There was a good linear correlation between relative fluorescence intensity and Fe~(3+) concentration ranging from 2 μmol/L to 20 μmol/L,and the detection limit reached1.70×10~(-2) μmol/L.The results showed that RB could detect Cu~(2+)and Fe~(3+) simultaneously,with the UV-Vis and fluorescence spectroscopy,respectively. 相似文献
22.
Fitting function representation for strain fields and its application to the optimizing process
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A fitted function method to describe the strain fields during forging was discussed to optimize the homogeneous distribution of strain in the axial forging zones during successive stretching. The results are verified by experiment and numerical simulation, and the deviations between experiment and simulation are less than 24%. Therefore, the fitted function method can be applied to optimize the stretching process for large forgings. The optimal value of feed determined by the analytic method ensures that the degree of inhomogeneity in strain in the axial ingot zone is less than 6%. This work provides a mathematic model to optimize technological parameters in stretch forging of large ingots. 相似文献
23.
This article summarizes the comparison between the preparation,structure and mechanical properties of long fiber reinforced thermoplastics(LFT) and short fiber reinforced thermoplastics(SFT).Both of the experiment and theory results showed that the mechanical properties of long glass fiber reinforced thermoplastics pellets(LGFRT) have been enhanced better than that of short glass fiber reinforced thermoplastics pellets(SGFRT) manufactured by molding procession.After regulation of the relative humidity by 50%,the mechanical properties of 30%(weight percent) short glass fiber content in SFT(SFT-PA6-SGF30) are similar to that of 40%long glass fiber content in LFT.However, the density of the latter is about 17%lower than that of the former.Thus,the corresponding weight of products is reduced by 13%;output rate is increased by 21%,and the cost is therefore significantly lowered.And it has the following advantages;impact strength is increased by 87%;the proportion is reduced by 20%;molding cycle is shortened by 10%;materials cost is saved by 20%~ 30%and the final total cost is saved by 30%~ 40%.So LFT (LFT-PP-LGF40 ) can replace SFT(SFT-PA6-SGF30) with the similar basic mechanical properties under normal temperature or 160℃lower. 相似文献
24.
Realtime speech communications require high efficient compression algorithms to encode speech signals. As the compressed speech parameters are highly sensitive to transmission errors, robust source and channel decoding and demodulation schemes are both important and of practical use. In this paper, an iterative joint source-channel decoding and demodulation algorithm is proposed for mixed excited linear prediction (MELP) vocoder by both exploiting the residual redundancy and passing soft information throughout the receiver while introducing systematic global iteration process to further enhance the performance. Being fully compatible with existing transmitter structure, the proposed algorithm does not introduce additional bandwidth expansion and transmission delay. Simulations show substantial error correcting performance and synthesized speech quality improvement over conventional separate designed systems in delay and bandwidth constraint channels by using the joint source-channel decoding and demodulation (JSCCM) algorithm. 相似文献
25.
Yttrium iron garnet (YIG) is widely used for microwave ferrite devices,especially for optical isolators. In this paper,ferrite ceramic target using cerium (Ce)-substituted YIG was made using ferric oxide (Fe2O3), cerium oxide (CeO2) and yttrium oxide (Y2O3) powders as raw material. Ce:YIG thin films were fabricated by radio frequency (RF) magnetron sputtering. The experimental result showed that the polycrystalline YIG was obtained after sintering at 1350℃ for 6h,and the polycrystalline Ce:YIG thin films were achieved annealing up to 700℃ in the air. 相似文献
26.
YUAN Kun ;ZHU YuanCheng ;LIU YanZhi ;LI ZhiFeng ;DONG XiaoNing ;WANG XiaoFeng ;LI HuiXue ;ZHANG Ji 《科学通报(英文版)》2008,53(20):3151-3158
The optimized geometries of the complexes between HnY (n=2, 3; Y=O, S, N) and LiNH2 have been calculated at the B3LYP/6-311++G^** and MP2/6-311++G^** levels. Three stable complexes were obtained. Frequency analysis showed that the enlarged 2N-4Li presents the abnormal blue shift in three complexes. The calculated binding energy with basis set super-position error (BSSE) and zero-point vibrational energy (ZPE) corrections of complex Ⅰ-Ⅲ is -58.65, -31.66 and -69.59 kJ·mol^-1 (MP2), respectively. Natural bond orbital theory (NBO) analysis has been performed, and the results revealed that the H2O…LiNH2 (complex I) and H3N…LiNH2 (complex Ⅲ) are formed with coexisting σ-s and n-s type lithium bond interactions, complex Ⅱ is formed with ττ-s type lithium bond interaction between HnY (n=2,3; Y=O, N) and LiNH2, and H2S…LiNH2 (complex Ⅱ) is formed with n-s type lithium bond interaction between H2S and LiNH2. Natural resonance theory (NRT) and atom in molecule (AIM) theory have also been studied to investigate the bond order and topological properties of the lithium bond structures. 相似文献
27.
28.
生长调节剂对金边玉簪丛生芽诱导影响的研究 总被引:1,自引:0,他引:1
以芽为外植体建立了金边玉簪组织培养的技术体系,重点研究了激素配比对玉簪丛生芽诱导的影响,并有效防止外植体褐变、玻璃化的问题。结果表明,金边玉簪的培养条件为:温度(26±1)℃,光照12 h/d,光照强度2 500 lx左右,pH值5.8~6.0,丛生芽诱导培养基以MS NAA4.0 BA0.1(mg/L)为好,30 d后启动率可达95%。 相似文献
29.
Rockafellar的一个择一定理的简证 总被引:1,自引:1,他引:0
徐增Kun 《浙江师范大学学报(自然科学版)》1993,16(3):12-14
本文为Rockafcllar的一个含有凸函数不等式和线性不等式的择一定理给出了简证,所用的工具只是凸集弱分离定理。 相似文献
30.
PBT/PET共混体系是一种结晶/结晶聚合物共混体系,除熔融状态外,通过骤冷或其他处理,还可得到玻璃体等非结晶态。本文研究它们处于非结晶态的相溶性问题,用动态粘弹谱仪、差示扫描量热等进行考察,取得处于非晶状态下的PBT/PET体系彼此相溶的实验判据。 相似文献