微通道换热器复合翅片的传热特性研究

研究了管径对微通道换热器传热性能的影响,并在百叶窗翅片的基础上开发了两种复合翅片。计算结果表明:在同一迎面风速下,1mm管径的百叶窗翅片Nu数分别比1.5mm和1.8mm管径的大4.8%~10.5%和24.6%~25.8%。JF值增加11%~15%和26%~28%,说明管径为1mm时微通道换热器的综合性能更好。与百叶窗翅片相比,百叶窗-三角翼复合翅片的换热系数减小1.9%~5.4%,但压降降低7.8%~12.7%,表明复合翅片是一种高效低阻翅片。     

Hierarchical Co<Subscript>3</Subscript>O<Subscript>4</Subscript>@C hollow microspheres with high capacity as an anode material for lithium-ion batteries

Three-dimensional hierarchical Co₃O₄@C hollow microspheres (Co₃O₄@C HSs) are successfully fabricated by a facile and scalable method. The Co₃O₄@C HSs are composed of numerous Co₃O₄ nanoparticles uniformly coated by a thin layer of carbon. Due to its stable 3D hierarchical hollow structure and uniform carbon coating, the Co₃O₄@C HSs exhibit excellent electrochemical performance as an anode material for lithium-ion batteries (LIBs). The Co₃O₄@C HSs electrode delivers a high reversible specific capacity, excellent cycling stability (1672 mAh g^?1 after 100 cycles at 0.2 A g^?1 and 842.7 mAh g^?1 after 600 cycles at 1 A g^?1), and prominent rate performance (580.9 mAh g^?1 at 5 A g^?1). The excellent electrochemical performance makes this 3D hierarchical Co₃O₄@C HS a potential candidate for the anode materials of the next-generation LIBs. In addition, this simple synthetic strategy should also be applicable for synthesizing other 3D hierarchical metal oxide/C composites for energy storage and conversion.     

Magnetic Dichroism in the Reflectivity of Linearly Polarized Synchrotron Radiation from a Ti(10 nm)/Gd<Subscript>0.23</Subscript>Co<Subscript>0.77</Subscript>(250 nm)/Ti(10 nm) Sample

The dichroic effect (“rotated” polarization) in the reflectivity from a magnetically ordered sample is experimentally studied at the station PHASE of the Kurchatov Synchrotron Radiation Source. The experiments are performed for the Gd_0.23Co_0.77 film, which has a compensation temperature T_comp ≈ 433 K, using linearly polarized radiation of the photon energy of 7930 eV (L₂ absorption edge of gadolinium) at room temperature. The developed theory of reflectivity accounted for the magnetic contributions to the scattering amplitude predicts the appearance of a peak for the orthogonal (to the incident polarization) polarization of the reflected radiation near the critical angle of the total external reflection. The experiment reveals the significant difficulties because of the incomplete σ polarization of the synchrotron beam, the beam instability, and so on. Therefore, a rotated-polarization peak has been detected near the critical angle but at the limits of the measurement accuracy. In principle, our experimental technique could be an alternative to circular polarization experiments, which are widely used at synchrotrons to study magnetic ordering. However, as we have shown, it makes high demands of the radiation source parameters.     

Simulation of current spreading for GaN-based light-emitting diodes

Uniform current spreading is crucial for the performance of light-emitting diodes (LEDs). It has been reported that the reliability and light distribution are affected by non-uniform current spreading. In this paper, the impact of different electrode patterns on the performance of LED chips is investigated. A hybrid modeling method is employed to analyze the electrical and thermal characteristics of LEDs with two different electrode mesa structures. Corresponding experiments are also carried out to validate the calculation results. It is found that increasing amount of p-electrodes in interdigitated electrode patterns is effective in improving the performance of LEDs.     

A Protocol for Bidirectional Quantum Secure Communication Based on Genuine Four-Particle Entangled States

By swapping the entanglement of genuine four-particle entangled states, we propose a bidirectional quantum secure communication protocol. The biggest merit of this protocol is that the information leakage does not exist. In addition, the ideas of the ＂two-step＂ transmission and the block transmission are employed in this protocol. In order to analyze the security of the second sequence transmission, decoy states are used.     

Sono-assisted preparation of highly-efficient peroxidase-like Fe3O4 magnetic nanoparticles for catalytic removal of organic pollutants with H2O2

Fe₃O₄ magnetic nanoparticles (Fe₃O₄ MNPs) with much improved peroxidase-like activity were successfully prepared through an advanced reverse co-precipitation method under the assistance of ultrasound irradiation. The characterizations with XRD, BET and SEM indicated that the ultrasound irradiation in the preparation induced the production of Fe₃O₄ MNPs possessing smaller particle sizes (16.5 nm), greater BET surface area (82.5 m² g^?1) and much higher dispersibility in water. The particle sizes, BET surface area, chemical composition and then catalytic property of the Fe₃O₄ MNPs could be tailored by adjusting the initial concentration of ammonia water and the molar ratio of Fe²⁺/Fe³⁺ during the preparation process. The H₂O₂-activating ability of Fe₃O₄ MNPs was evaluated by using Rhodamine B (RhB) as a model compound of organic pollutants to be degraded. At pH 5.4 and temperature 40 °C, the sonochemically synthesized Fe₃O₄ MNPs were observed to be able to activate H₂O₂ and remove ca. 90% of RhB (0.02 mmol L^?1) in 60 min with a apparent rate constant of 0.034 min^?1 for the RhB degradation, being 12.6 folds of that (0.0027 min^?1) over the Fe₃O₄ MNPs prepared via a conventional reverse co-precipitation method. The mechanisms of the peroxidase-like catalysis with Fe₃O₄ MNPs were discussed to develop more efficient novel catalysts.     

吩噻嗪卤代衍生物的荧光研究

本主要研究了３－溴－Ｎ－乙基吩噻嗪（Ｂｒ－Ｐ）在各种酸度、增敏溶剂、感光效应等条件下的荧光变换现象,并确定了最佳的发光体系。方法简单、准确可靠,其线性范围为１×１０＾－７￣１×１０＾－４ｍｏｌ／Ｌ,检出限为１×１０＾－８ｍｏｌ／Ｌ,ＲＳＤ〈２．８％。     

界面缓蚀剂的吸附稳定性

研究表明：在一定条件下,阳极脱附电位可作为评价缓蚀剂吸附稳定性的一个经验参数：缓蚀剂吸脱附诱导的电化学振荡是缓蚀体系的一种特殊失稳状态,即缓蚀剂吸附过程与电极反应中间吸附态产物耦合的结果;卤素离子的协同作用不仅可以提高某些有机缓蚀剂的吸附复盖度,而且可以增强其吸附稳定性;微分极化曲线是研究吸附稳定性的有效方法。     

Styrene polymerization in ternary microemulsions: effects of water-soluble and oil-soluble initiators

The polymerization of styrene in ternary microemulsions stabilized by the cationic surfactant tetradecyltrimethylammonium bromide was studied as a function of concentrations of water-soluble (potassium persulfate, KPS) and oil-soluble (AIBN) initiators. At a particular molar ratio of the initiators, similar maximum rates of polymerization can be achieved from using both types of the initiators. In addition, both initiated systems produced microlatexes with similar hydrodynamic radius, number of polymer particles, molecular weight of polystyrene and number of polymer chain per latex particle. But the dependencies of these latex parameters on concentrations of KPS and AIBN may not be the same. The polymerization mechanism appears to be similar, irrespective of using KPS or AIBN. It is discussed in terms of effective radicals produced for the polymerization. While the different dependencies of some latex parameters on concentrations of the initiators are attributed to the different efficiencies of the initiators in producing effective radicals.