低喷淋密度超亲水表面水平管降液膜温度分布

水平管降液膜蒸发广泛应用在石油、化工、海水淡化等领域,对低喷淋密度温度演化规律的研究有助于拓宽其应用范围,理解其微观机理。本文在超亲水表面上结合红外热追踪技术,对水平管降液膜表面的温度演化规律进行了研究,分析了温度分区现象和温升规律。实验中首次发现了马鞍形液膜内部的高温环状结构,并结合三维数值模拟揭示了掺混作用导致的局部高温环状结构形成的内部机理。     

GOSs-稀土配合物紫外增强材料的光谱分析与稳定性研究

氧化石墨烯薄片(GOSs)作为一种新型的二维片状材料,具有较高的比表面积、丰富的表面含氧官能团以及良好的光热稳定性。而稀土配合物通过无机稀土元素与有机配体的结合表现出优异的荧光特性。为了将两类材料具有的物化特性结合起来应用于紫外光谱探测领域。选取了合适的有机配体啉菲罗啉(1,10-邻二氮杂菲,phen)、2’2-联嘧啶(bpm)作为桥联分子,把氧化石墨烯(GOSs)与稀土配合物通过氢键自组装作用进行复合,制备了高效稳定可调的GOSs-稀土配合物复合荧光材料GOSs-Eu(BA)3phen和GOSs-Eu(TTA)3bpm,并且制备了相应的聚乙烯醇(PVA)共混紫外增强薄膜,对其光谱特性与稳定性进行了深入的研究。采用红外光谱、扫描电镜和金相显微镜等方法,对紫外增强材料进行了性能表征。采用吸收光谱,荧光光谱等方法,对紫外增强薄膜进行了性能表征。此外,通过热重测试(TGA)表征了GOSs氢键复合前后紫外增强材料的热稳定性,通过荧光强度-紫外光照次数表征了GOSs氢键复合前后紫外增强薄膜的光稳定性。红外光谱分析发现,进行配位前后有机配体的特征峰产生了频移,表明稀土配合物中Eu 3+与配体之间存在着明显的配位作用。在进行复合之后,桥联配体的特征峰也产生了偏移,表明GOSs与稀土配合物通过桥联分子的氢键作用进行了进行复合。吸收光谱与荧光光谱测定结果表明增强薄膜吸收峰在200~400 nm,荧光主峰在612 nm左右,为Eu 3+特征红色荧光峰,且不同配体可以实现不同范围的吸收产生差异化的荧光表现。扫描电镜和金相显微镜清晰地展示了稀土配合物复合前后的微观形貌,即颗粒状稀土配合物附着在石墨烯薄片上。光稳定性测试表明经过GOSs氢键复合之后,Eu(BA)3phen和Eu(TTA)3bpm稀土配合物荧光材料在进行25次荧光强度测试后光漂白程度分别下降了4.26%和6.41%,提高了其光稳定性。热重测试也表明在经过GOSs氢键复合之后,稀土配合物的热稳定性有了很大提高。总之,得益于GOSs和稀土配合物的特性结合,所制备的紫外增强材料表现出优异的荧光特性与稳定性,必将在紫外探测方面有着广阔的应用前景。     

Light-induced interaction between graphene and magnetic film in a cavity

An interaction mechanism between graphene and magnetic film in cavity is presented in this work. The pseudospin in graphene can indirectly interact with the spins in magnetic film by the media of a circularly polarized photons under the conditions of high temperature and intense laser field. The interaction energy as well as the average values of pseudospin and spin components are calculated according to a generating functional approach. This interaction mechanism provides a scheme of detecting the pseudospin polarization effect.     

Evolution of Classical and Quantum States in the Groupoid Picture of Quantum Mechanics

The evolution of states of the composition of classical and quantum systems in the groupoid formalism for physical theories introduced recently is discussed. It is shown that the notion of a classical system, in the sense of Birkhoff and von Neumann, is equivalent, in the case of systems with a countable number of outputs, to a totally disconnected groupoid with Abelian von Neumann algebra. The impossibility of evolving a separable state of a composite system made up of a classical and a quantum one into an entangled state by means of a unitary evolution is proven in accordance with Raggio’s theorem, which is extended to include a new family of separable states corresponding to the composition of a system with a totally disconnected space of outcomes and a quantum one.     

An Improved Composite Multiscale Fuzzy Entropy for Feature Extraction of MI-EEG

Motor Imagery Electroencephalography (MI-EEG) has shown good prospects in neurorehabilitation, and the entropy-based nonlinear dynamic methods have been successfully applied to feature extraction of MI-EEG. Especially based on Multiscale Fuzzy Entropy (MFE), the fuzzy entropies of the τ coarse-grained sequences in τ scale are calculated and averaged to develop the Composite MFE (CMFE) with more feature information. However, the coarse-grained process fails to match the nonstationary characteristic of MI-EEG by a mean filtering algorithm. In this paper, CMFE is improved by assigning the different weight factors to the different sample points in the coarse-grained process, i.e., using the weighted mean filters instead of the original mean filters, which is conductive to signal filtering and feature extraction, and the resulting personalized Weighted CMFE (WCMFE) is more suitable to represent the nonstationary MI-EEG for different subjects. All the WCMFEs of multi-channel MI-EEG are fused in serial to construct the feature vector, which is evaluated by a back-propagation neural network. Based on a public dataset, extensive experiments are conducted, yielding a relatively higher classification accuracy by WCMFE, and the statistical significance is examined by two-sample t-test. The results suggest that WCMFE is superior to the other entropy-based and traditional feature extraction methods.     

微织构超声振动铣削系统的研究

为了在金属切削过程中在7075铝合金表面形成稳定的微织构以提高其服役性能,提出一种微织构超声铣削加工工艺。为此,该文首先基于运动合成原理获得了刀尖的运动轨迹特征和工件表面的织构形貌特征。然后,基于等效电路原理和传输矩阵法建立了超声铣削系统的频率方程,并应用牛顿迭代法获得了准确的数值解,通过有限元软件对建立的超声振动系统分别进行模态分析和谐响应分析,获得了具有微织构特征的纵扭复合超声铣削系统。最后,对加工制造出的微织构纵扭复合超声铣削系统进行振动测试、切削力测试和加工测试,结果表明:工件表面形成的"鱼鳞网纹"微观织构能够改变其润湿性能。     

A solvent-governed surface state strategy for rational synthesis of N and S co-doped carbon dots with multicolour fluorescence

ABSTRACT

Multicolour emissive carbon dots (CDs) are widely investigated by virtue of their merits on fluorescent properties. Method on heteroatom doping assisted with various solvents has been proved efficient in achieving multiple-colour-emissive CDs, especially long-wavelength emission. Herein, a synthesis of multicolour-emissive CDs by controlled surface function is reported. By tuning the thermal-pyrolysis temperature and molar ratio of reactants, optimal emission of the resulted CDs gradually shifts from blue to yellow light with the assistance of different solvents. According to the emissive relationship dependent on excitation, fluorescence lifetimes, and FT-IR of these CDs, the different surface states participated with S and N elements on the surface of carbogenic core govern fluorescent colours of the CDs. In terms of the applications, blue CDs (B-CDs) exhibits high sensitivity for ion detections of Ag⁺ and Fe³⁺, which is further illustrated to have different quenching mechanisms each other because that these ions have the affinity interaction with different surface groups of the CDs. Moreover, blue and yellow CDs solutions are mixed with PVP water solution to fabricate white-light CDs/PVP film, which exhibits stable fluorescence with a CIE coordinate of (0.32, 0.33) and endows these CDs as potentially fluorescent nanomaterial in the solid state lighting field.     

TracePro在“光的偏振实验”中的应用

为提高光的偏振实验教学效果和教学质量,在教学中引入专业的光学设计软件--TracePro,利用该软件仿真了光的双折射过程和现象,以及偏振片的原理;建立光的偏振实验系统实体模型,完成光的偏振态判断实验;仿真光通过波片后的偏振态转换现象;验证马吕斯定律,并仿真了多层介质膜对光的分离和旋光现象.结果表明该方法可以提高教学效率,激发学生探索科学的主观能动性,仿真结论与理论推导和实际实验结果一致.     

工质对微通道沸腾液膜瞬态变化的影响

本文采用去离子水和无水乙醇两种工质,利用微通道流动沸腾同步测量实验系统,研究了液膜厚度的瞬态变化规律,实验发现流动沸腾形成的初始液膜厚度在毛细数Ca很宽的范围内都遵循Taylor流动原理;液膜形成后,在蒸发和蒸汽流动携带的耦合作用下,厚度迅速减薄直至蒸干;由于水的汽液黏度比小,速度梯度小,剪切作用带来的液膜厚度减少量小,且水的汽化潜热大,吸收相同热量时蒸发量小,导致水的液膜厚度变化斜率较小,通过理论分析提出了沸腾液膜厚度变化的计算模型,计算结果与实验结果的误差小于20%。     

Measurement and analysis of excitation functions for alpha-induced reactions in copper

Excitation functions for the production of⁶⁸Ga,⁶⁷Ga,⁶⁶Ga,⁶⁵Ga +⁶⁵Zn and⁶¹Cu fromα-induced reactions in natural copper have been measured in the energy range ≈ 10–40 MeV using the stacked foil technique. A stack of nine copper foils was irradiated by a 40 MeVα-beam. Theγ-rays emitted from the irradiated samples were recorded. Excitation functions have also been calculated theoretically using a statistical model with and without the inclusion of pre-equilibrium emission of particles. Pre-equilibrium component simulated by exciton model shows that the inclusion of pre-equilibrium emission gives better agreement between experimental and theoretical excitation functions. Pre-equilibrium fraction depends on the incident energy and the target mass number.