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1.
基于喷雾冷却时液滴撞击壁面现象,本文采用CLSVOF(coupled level set and volume of fluid)方法对不同工况下单液滴撞壁过程进行数值模拟,获得了单液滴撞击热壁面动态特性;分析了初始速度、液滴直径等初始参数对液滴撞壁后的动态铺展规律以及壁面换热特性的影响规律,获得了上述参数变化时液滴铺展系数和热流密度的变化趋势;探讨了场协同效应、液滴内部气泡以及三线接触点对壁面换热的影响。碰壁现象的研究对于大型制冷机组室外机散热、高热流电子器件散热等领域优化与控制喷雾有重要意义。  相似文献   
2.
本文利用电子动量谱仪在1200 eV电子碰撞能量下测量了碘甲烷分子内层轨道电子束缚能谱和电子动量分布. 在能谱上观测到自旋-轨道耦合作用导致的两个分裂峰,得到了它们对应的电子动量分布. 采用相对论密度泛函理论方法计算了自旋-轨道分裂成分的电子动量分布,计算结果在电子动量大于1.0 a.u.区域内与实验测量符合很好,但在动量小于1.0 a.u.区域内严重低估了实验. 扭曲波理论计算很好地解释了低动量区的实验结果.  相似文献   
3.
Antibiotics, once being released into the environment, become recalcitrant organic pollutants, which pose a potential risk to ecological balance and human health. In this study, a Z-scheme heterojunction of bismuth oxyiodide (BiOI)/exfoliated g-C3N4 (BiOI/ECN hereafter) was synthesized by the combination of thermal exfoliation of g-C3N4 and chemical precipitation of BiOI for efficient photocatalytic degradation of tetracycline in aqueous solutions under visible light irradiation. The optimized BiOI/ECN delivered an outstanding degradation rate at circa 0.0705 min?1, which was 10 times higher than that of the bulk g-C3N4. The photocatalytic degradation efficiency of tetracycline remained almost unchanged in a pH range of 3–11, and the BiOI/ECN displayed an excellent photostability upon recycled usage. The photocatalytic mechanism of tetracycline was ascribed to the main reactive oxidation species of photogenerated holes and superoxide radicals. In addition, the possible degradation pathways of tetracycline were investigated by HPLC-MS to identify intermediates. The toxicity of photocatalytic-generated intermediates of tetracycline was found significantly alleviated according to the calculation of quantitative structure–activity relationship prediction. This work not only provides an attractive photocatalyst for the removal of tetracycline but also opens a new avenue for rational design of Z-scheme heterojunction composites for tetracycline degradation.  相似文献   
4.
Addressing arsenite pollution in groundwater has drawn great attention. It is attractive to pre-oxidize highly mobile As(III) to relatively low-toxic As(V) with a subsequent adsorption separation process. Herein, BiOI anchoring on γ-Fe2O3 is performed to synthesize BiOI/γ-Fe2O3 core–shell nanoparticles for efficient removal of As(III) via a simultaneous photocatalytic oxidization–adsorption process. The physical and chemical structures of BiOI/γ-Fe2O3 are investigated by transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction measurements. The photoluminescence and electron spin resonance (ESR) characterization were employed to ascertain the possible reaction mechanism of visible-light-driven photocatalytic oxidation of As(III). Such BiOI/γ-Fe2O3 delivers a superior As(III) removal capability under visible light irradiation with an arsenic removal efficiency of 99.8% within 180 min, higher than those of BiOCl/γ-Fe2O3 (81.7%) and BiOBr/γ-Fe2O3 (98.9%). The optimal BiOI/γ-Fe2O3 (molar ratio of 2:1) is obtained by rationally adjusting the molar ratio of BiOI to γ-Fe2O3. The as-synthesized BiOI/γ-Fe2O3 performs well in a wide pH range of 2–8. Only coexisting PO43? anions have a significant effect on the As(III) removal. The free radical trapping experiment and ESR results demonstrate that the ?O2? and h+ are the main active substances for the photocatalytic oxidation of As(III) on BiOI/γ-Fe2O3. This work not only gives a novel magnetic core–shell nanoparticle photocatalyst for efficient photocatalytic oxidation and adsorption of As(III) but also offers a new strategy to rationally design BiOX for its related practical applications.  相似文献   
5.
With the development of green chemistry, it is still a challenge to maintain the unstable valence state of the metal in heterogeneous catalysts and realize new catalytic synthesis methods. In this paper, it is reported that an univalent copper nanocomposite (Cu@Al/SBA-15) can efficiently catalyze the formation of novel amino-containing benzotriazoles with great fluorescence properties in a new synthetic strategy. Subsequently, its application is further verified by an acylation reaction to produce a series of novel benzotriazoles derivatives with high yield. It is worth noting that the Cu@Al/SBA-15 nanocomposites not only enable the reaction completed with high yield in a short time, but can also be recycled many times without a significant reduction in activity, and the leaching of copper and aluminum species in reaction system is negligible. Finally, the detailed and feasible reaction mechanism is also provided.  相似文献   
6.
Chemistry of Natural Compounds - A new carotane sesquiterpenoid, methyl gymnabloate (1), was isolated from the fermentation broth of the wild macrofungus Gymnopus sp. 0612-9. Its structure was...  相似文献   
7.
近年来,半导体光催化在环境净化和有机合成领域的研究引起了广泛的重视.其中,在有机合成领域中,光催化技术已经应用在醇类、环己烷以及芳香族化合物的选择性氧化研究.而另一类具有特殊结构的有机物——N-杂环芳烃,在药物化学和材料科学中具有重要意义.而传统用于合成N-杂化芳烃的脱氢催化氧化反应通常需要高温高压的苛刻环境,传统方法通常还需要使用贵金属催化剂,这也增加了N-杂化芳烃的合成成本;另外,如果合成是均相催化过程,则催化剂难以实现回收利用.因此,开发室温常压条件下的非贵金属多相光催化技术具有巨大的应用前景.本文以能够被可见光驱动的钼酸铋半导体为催化剂,利用氧缺陷策略来提升钼酸铋的光催化氧化性能.不同于传统氧缺陷制备方法(氢气还原热处理、离子掺杂等),本文采用一种低成本的乙二醛辅助溶剂热的方法合成具有可调控的含氧空位Bi2MoO6催化剂(OVBMO).通过X射线粉末衍射(XRD)、扫描电镜、透射电镜、紫外可见漫反射吸收光谱、氮气物理吸附脱附、X射线光电子能谱(XPS)、电子自旋共振光谱、光致发光光谱及电化学测试等技术对制备的OVBMO材料进行了物理化学性质及能带研究.XPS,XRD,Raman和FT-IR结果表明,氧空位存在于[Bi2O2]2+和MoO6八面体的层间.紫外可见漫反射结果表明,随着氧空位的引入,Bi2MoO6的光吸收范围扩大,带隙变窄.结合莫特肖特基和VBXPS分析获得OVBMO的能带位置,发现氧空位的存在不仅会导致禁带中出现缺陷带能级,还会导致价带顶位置上移,促进光生空穴的迁移.PL和电化学结果表明,氧空位的存在使得载流子浓度、载流子的分离能力与界面电荷迁移能力都有较大提升,这是因为氧空位引入的缺陷能级可以浅势捕获电子,抑制光催化剂中的电子与空穴的复合,改变化学反应的速率.同时,氧空位有助于捕获分子氧,分子氧与捕获的光生电子发生反应,产生更多的超氧自由基(·O2)和空穴(h+),从而极大地提升光催化剂的氧化性能.因此,OVBMO在1,2,3,4-四氢喹啉脱氢氧化产生喹啉及系列抗生素(环丙沙星、四环素、盐酸土霉素)的降解反应中,表现出较好的光催化氧化性能.结合多种表征分析,本文还进一步阐明了OVBMO催化剂将1,2,3,4-四氢喹啉脱氢氧化为喹啉的自由基参与的多相催化反应机理.  相似文献   
8.
Continuous microporous membranes are widely studied for gas separation, due to their low energy premium and strong molecular specificity. Porous aromatic frameworks (PAFs) with their exceptional stability and structural flexibility are suited to a wide range of separations. Main-stream PAF-based membranes are usually prepared with polymeric matrices, but their discrete entities and boundary defects weaken their selectivity and permeability. The synthesis of continuous PAF membranes is still a major challenge because PAFs are insoluble. Herein, we successfully synthesized a continuous PAF membrane for gas separation. Both pore size and chemistry of the PAF membrane were modified by ion-exchange, resulting in good selectivity and permeance for the gas mixtures H2/N2 and CO2/N2. The membrane with Br? as a counter ion in the framework exhibited a H2/N2 selectivity of 72.7 with a H2 permeance of 51844 gas permeation units (GPU). When the counter ions were replaced by BF4?, the membrane showed a CO2 permeance of 23058 GPU, and an optimized CO2/N2 selectivity of 60.0. Our results show that continuous PAF membranes with modifiable pores are promising for various gas separation situations.  相似文献   
9.
Separation of microparticle in viscoelastic fluid is highly required in the field of biology and clinical medicine. For instance, the separation of the target cell from blood is an important prerequisite step for the drug screening and design. The microfluidic device is an efficient way to achieve the separation of the microparticle in the viscoelastic fluid. However, the existing microfluidic methods often have some limitations, including the requirement of the long channel length, the labeling process, and the low throughput. In this work, based on the elastic-inertial effect in the viscoelastic fluid, a new separation method is proposed where a gradually contracted microchannel is designed to efficiently adjust the forces exerted on the particle, eventually achieving the high-efficiency separation of different sized particles in a short channel length and at a high throughput. In addition, the separation of WBCs and RBCs is also validated in the present device. The effect of the flow rate, the fluid property, and the channel geometry on the particle separation is systematically investigated by the experiment. With the advantage of small footprint, simple structure, high throughput, and high efficiency, the present microfluidic device could be utilized in the biological and clinical fields, such as the cell analysis and disease diagnosis.  相似文献   
10.
Journal of Radioanalytical and Nuclear Chemistry - This study presents a time-efficient method of analysing 210Pb, 210Bi, and 210Po in natural waters. The optimum pH (1.00), temperature...  相似文献   
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