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排序方式: 共有462条查询结果,搜索用时 15 毫秒
91.
在硫酸介质中,以硼氢化钠(NaBH4)为还原剂,可将As(Ⅲ)还原为砷化氢(AsH3)气体使其逸出,用Ce(SO4)2-H2SO4-KI混合液做吸收液,在催化剂KI存在下四价铈与AsH3气体反应生成具有共振瑞利散射(RRS)的砷微粒和具有荧光的三价铈,导致体系在370 nm处的RRS信号和在351 nm处的荧光强度增大。在选定条件下,As(Ⅲ)浓度分别在0.006~0.76 mg·L-1和0.006~0.28 mg·L-1范围内与RRS增加值ΔI和荧光强度增大值ΔF351呈线性关系,检出限均为3.0 μg·L-1。据此可建立新的检测As(Ⅲ)的催化RRS和荧光光谱法。 相似文献
92.
Xiaoyu Li Fei Chen Chengjiang Lian Shizheng Zheng Quanhong Hu Shuwang Duo Wenkui Li Changyuan Hu 《Journal of Cluster Science》2016,27(6):1877-1892
Au/TiO2/graphene composite was synthesized by the combination of electrostatic attraction and photo-reduction method. In the composite, graphene sheets act as an adsorption site for dye molecules to provide a high concentration of dye near to the TiO2 and Au nanoparticles (NPs), and work as an excellent electron transporter to separate photoinduced e ?/h + pairs. Under UV irradiation, photogenerated electrons of TiO2 are transferred effectively to Au NPs and graphene sheets, respectively, retarding the recombination of electron–hole pairs. Under visible light irradiation, the Au NPs are photo-excited due to the surface plasmon resonance effect, and charge separation is accomplished by the interfacial electron injection from the Au NPs to the conduction band of TiO2 and then transfer further to graphene sheets. As a result, compared with pure TiO2, Au/TiO2/graphene composite exhibited much higher photocatalytic activity for degradation of methylene blue under both UV and visible light irradiation, based on the synergistic effect of Au, graphene in contact with TiO2, allowing response to the visible light, effective separation of photoinduced charges, and better adsorption of the dye molecules. 相似文献
93.
The properties and reactivity of Si-doped hexagonal boron nitride (h-BN) sheets were studied using density functional theory (DFT) methods. We find that Si impurity is more likely to substitute the boron site (SiB) due to the low formation energy. Si-doping severely deforms h-BN sheet, resulting in the local curvature changes of h-BN sheet. Moreover, Si-doping introduces two spin localized states within the band gap of h-BN sheet, thus rendering the two doped systems exhibit acceptor properties. The band gap of h -BN sheet is reduced from ∼4.70 eV to 1.24 (for SiB) and 0.84 eV (for SiN), respectively. In addition, Si-doped one exhibits higher activity than pristine one, endowing them wider application potential. 相似文献
94.
高准确度自动跟踪系统是太阳能聚光器必不可少的组成部分,而信号采集器能否精确可靠地采集到阳光照射方向的信号又是自动跟踪准确度的关键.本文提出了一种粗细调互补信号采集器的设计方案,在正常工作期间通过软件能够根据需要不断地自动调整选择二组光电传感器中其中一组输出的差模信号作为有效信号,从而有效地解决了大范围寻找太阳和高准确度跟踪之间的矛盾|而在此基础上改进为对聚光后的阳光信号进行采集的新结构,又彻底解决了光电传感器本身在光照强度很大时进入饱和区与光照强度很弱时输出的差模信号太小的问题,有效延长了聚光器在早晚时段的正常工作时间.据此原理制作的聚光型粗细调互补信号采集器应用于某公司的CPV型1200W砷化镓发电系统中,取得了很好的跟踪效果,其实际跟踪误差≤0.1°(立体角). 相似文献
95.
Influence of screw length and diameter on tibial strain energy density distribution after anterior cruciate ligament reconstruction 总被引:1,自引:0,他引:1
Jie Yao Guan-Ming Kuang Duo Wai-Chi Wong Wen-Xin Niu Ming Zhang Yu-Bo Fan 《Acta Mechanica Sinica》2014,30(2):241-249
Postoperative tunnel enlargement has been frequently reported after anterior cruciate ligament(ACL)reconstruction.Interference screw,as a surgical implant in ACL reconstruction,may influence natural loading transmission and contribute to tunnel enlargement.The aims of this study are(1)to quantify the alteration of strain energy density(SED)distribution after the anatomic single-bundle ACL reconstruction;and(2)to characterize the influence of screw length and diameter on the degree of the SED alteration.A validated finite element model of human knee joint was used.The screw length ranging from 20 to 30 mm with screw diameter ranging from 7 to 9 mm were investigated.In the post-operative knee,the SED increased steeply at the extra-articular tunnel aperture under compressive and complex loadings,whereas the SED decreased beneath the screw shaft and nearby the intra-articular tunnel aperture.Increasing the screw length could lower the SED deprivation in the proximal part of the bone tunnel;whereas increasing either screw length or diameter could aggravate the SED deprivation in the distal part of the bone tunnel.Decreasing the elastic modulus of the screw could lower the bone SED deprivation around the screw.In consideration of both graft stability and SED alteration,a biodegradable interference screw with a long length is recommended,which could provide a beneficial mechanical environment at the distal part of the tunnel,and meanwhile decrease the bone-graft motion and synovial fluid propagation at the proximal part of the tunnel.These findings together with the clinical and histological factors could help to improve surgical outcome,and serve as a preliminary knowledge for the following study of biodegradable interference screw. 相似文献
96.
Fang FANG Shuwen TANG Shitao WANG Xueheng ZHANG Zhiyu SUN Yuhong YU Duo YAN Shuya JIN Yixuan ZHAO Shaobo MA Yongjie ZHANG 《原子核物理评论》2022,39(1):65-72
为了提升兰州重离子加速器冷却存储环(HIRFL-CSR)中放射性次级束流装置(RIBLL2)的粒子鉴别能力,在其F1色散面上研发、安装了一套可测量核反应产物起始时间和位置等信息的新型高性能探测器,并发展了一种利用测量的位置及飞行时间等实验数据提取束线光学参数从而修正粒子磁刚度的实验方法。使用F1色散面上的新型探测器,再结合粒子磁刚度修正方法,首次在RIBLL2-ETF分离器上实现了全动量接收度下300 MeV/nucleon 78Kr弹核碎裂产物的清楚鉴别,结果显示:对于较重的75As33+,其电荷分辨σZ~0.19、质核比分辨σA/Z~5.8×10?3。这一结果,有效提升了RIBLL2粒子鉴别能力,增加了奇异核收集效率,使研究范围由低质量核区(A<40)拓展到了中等质量核区(A~80),这将有效促进RIBLL2上放射性次级束物理实验的发展。 相似文献
97.
Several imidazolium ionic liquid(IL)-supported sulfonic acids with different anions,[C3SO3Hmim]HSO4,[C3SO3Hmim]BF4, [C3SO3 Hmim]PF6,and[C3SO3Hmim]CF3SO3,were synthesized and applied as catalysts for esterification reaction of benzoic acid. The experimental results indicate that imidazolium IL-supported sulfonic acid containing anion of HSO4- shows the best catalytic activity.Only when less[C3SO3Hmim]HSO4(0.3 equiv.) applied,was the product obtained with high yield of 97%.Furthermore, the produced esters could be separated by decantation,and the catalyst could be reused after the removal of water. 相似文献
98.
Xingchao Wang Yudai Huang Dianzeng Jia Zaiping Guo Duo Ni Ming Miao 《Journal of Solid State Electrochemistry》2012,16(1):17-24
Olivine LiFePO4/C nanocomposite cathode materials with small-sized particles and a unique electrochemical performance were successfully prepared
by a simple solid-state reaction using oxalic acid and citric acid as the chelating reagent and carbon source. The structure
and electrochemical properties of the samples were investigated. The results show that LiFePO4/C nanocomposite with oxalic acid (oxalic acid: Fe2+= 0.75:1) and a small quantity of citric acid are single phase and deliver initial discharge capacity of 122.1 mAh/g at 1
C with little capacity loss up to 500 cycles at room temperature. The rate capability and cyclability are also outstanding
at elevated temperature. When charged/discharged at 60 °C, this materials present excellent initial discharge capacity of
148.8 mAh/g at 1 C, 128.6 mAh/g at 5 C, and 115.0 mAh/g at 10 C, respectively. The extraordinarily high performance of LiFePO4/C cathode materials can be exploited suitably for practical lithium-ion batteries. 相似文献
99.
The determination of α-lactalbumin in various dairy products attracts wide attention in multidiscipline fields because of its nutritional and biological functions. In the present study, we quantified the bovine α-lactalbumin in various infant formulas and whey protein concentrates using ultra-high performance liquid chromatography coupled to tandem mass spectrometer in multiple reaction monitoring mode. Bovine α-lactalbumin was quantified by employing the synthetic internal standard based on the molar equivalent relationship among the internal standard, bovine α-lactalbumin and their signature peptides. This study especially focused on the recovery rates of the sample preparation procedure and robust quantification of total bovine α-lactalbumin in its native and thermally denatured form with a synthetic internal standard KILDKVGINNYWLAHKALCSE. The observed recovery rates of bovine α-lactalbumin ranged from 95.8 to 100.6% and the reproducibility was excellent (RSD < 6%) at different spiking levels. The limit of quantitation is 10 mg/100 g for infant formulas and whey protein concentrates. In order to validate the applicability of the method, 21 brands of infant formulas were analyzed. The acquired contents of bovine α-lactalbumin were 0.67–1.84 g/100 g in these infant formulas in agreement with their label claimed values. The experiment of heat treatment time showed that the loss of native α-lactalbumin enhanced with an increasing intensity of heat treatment. Comparing with Ren's previous method by analysis of only native bovine α-lactalbumin, the present method at the peptide level proved to be highly suitable for measuring bovine α-lactalbumin in infant formulas and whey protein concentrates, avoiding forgoing the thermally induced denatured α-lactalbumin caused by the technological processing. 相似文献
100.
微沟槽结构注塑成形的充型过程计算方法 总被引:2,自引:0,他引:2
微注塑成形制造方法适合于热塑性材料微小型器件大批量加工,对微注塑关键步骤——充型进行分析计算,有助于微注塑工艺参数和模具结构优化。目前研究表明,微尺度聚合物熔体流动与常规流动存在显著差异,采用常规尺度流动计算分析工具会带来较大偏差。本文以开源计算代码OpenFOAM为基础,综合由实验获得的熔体表面特性规律和粘度变化规律等,采用面向对象编程方法构建了熔体填充微结构型腔流动过程的计算模块,以微流体器件中的典型微结构——微沟槽注塑充型过程为例进行数值模拟,分析了表面力和粘度作用对其注塑充型填充率的影响。 相似文献