有限存贮空间内可燃多孔介质流动和传热的研究

对通风条件下可燃多孔介质库房内的流动和传热特性进行了数值模拟,得到了库房有限空间内的温度场和速度场.通过比较不同的来流温度和入口流速,得到的结果表明:可燃多孔介质(弹药)内部发生化学反应并产生热量,其温度由中心向四周逐渐降低;来流流速越大,越有利于弹药的冷却;在来流速度相同的情况下,来流温度越低,越有利于散热,对于可燃多孔介质(弹药)的贮存越安全;在左侧进风口的上下两边以及可燃多孔介质(弹药)的上方,会形成漩涡.     

Study of shear transfer in Al/epoxy joint by digital photoelasticity

An improved six-step phase-shifting method is proposed for calculating full-field shear stress based on a four-step color phase-shifting method in digital photoelasticity. The method was verified using a disk under diametral compression and then applied to an aluminum alloy/epoxy joint for studying the shear transfer behavior. Experimental results revealed that the isochromatic fringe order and shear stress at the bonding interface are distributed continuously and increased with compression. In particular, an antisymmetric thermal residual shear stress appears at the bonding interface, because of the difference in the thermal expansion coefficients of Al and the resin. This indicates that the thermal residual shear stress at the bonding interface is self-balanced and reaches a peak at the edges of the bonding interface. The load transfer is realized by the shear band from the bonding interface to the bottom support. Basically, the bonding interfacial shear stress is balanced with the load.     

Relativistic Mean Field Study of the Z=117 Isotopic Chain

The properties of the Z = 117 isotopic chain are studied within the framework of the axially deformed relativistic mean field theory （RMFT） in the blocked BCS approximation. The ground-state properties, such as hinging energies, deformations as well as the possible α decay energies and lifetimes are calculated with the parameter set of NL-Z2 and compared with results from the finite range droplet model. The analysis by RMFT shows that the isotopes in the range of mass number A =291 ~ 300 exhibit higher stability, which suggests that they may be promising nuclei to be hopefully synthesized in the lab among the nuclei Z = 117.     

300GHz超导SIS接收机系统的设计与构建

超导SIS(Superconductor-Insulator-Superconductor)混频技术是新兴的低噪声检测技术.其卓越的低噪声性能已使其成为毫米波和亚毫米波频段灵敏度最高的谱线接收设备,接收机的自动控制和稳定性有更高的要求,研制能够长期稳定工作的接收机有很重要的意义.本文主要讨论了我们自行研究设计工作在4K温度,准光学系统的毫米波超导SIS接收机的组成部件,根据我们制备的超导SIS隧道结器件的特性指标,计算设计了300GHz波段的超导接收机天线和结的集成芯片.     

Entropy Generation for Negative Frictional Pressure Drop in Vertical Slug and Churn Flows

It is widely accepted that the frictional pressure drop is impossible to be negative for pipe flow. However, the negative frictional pressure drops were observed for some cases of two-phase slug and churn flows in pipes, challenging the general sense of thermodynamic irreversibility. In order to solve this puzzling problem, theoretical investigations were performed for the entropy generation in slug and churn flows. It is found that the frictional pressure drop along with a buoyancy-like term contributes to the entropy generation due to mechanical energy loss for steady, incompressible slug and churn flows in vertical and inclined pipes. Experiments were conducted in a vertical pipe with diameter as 0.04 m for slug and churn flows. Most of the experimental data obtained for frictional pressure drop are negative at high gas–liquid ratios from 100 to 10,000. Entropy generation rates were calculated from experimental data. The results show that the buoyancy-like term is positive and responsible for a major part of entropy generation rate while the frictional pressure drop is responsible for a little part of entropy generation rate, because of which the overall entropy generation due to mechanical energy loss is still positive even if the frictional pressure drop is negative in vertical slug and churn flows. It is clear that the negative frictional pressure drops observed in slug and churn flows are not against the thermodynamics irreversibility.     

Research on Preparation Methods of Carbon Nanomaterials Based on Self-Assembly of Carbon Quantum Dots

Here, based on self-assembly of carbon quantum dots (CDs), an innovative method to prepare nanomaterials under the action of a metal catalyst was presented. CDs were synthesized by a one-step hydrothermal method with citric acid (CA) as the carbon source, ethylenediamine (EDA) as the passivator and FeSO₄•7H₂O as the pre-catalyst. In the experiment, it was found that the nano-carbon films with a graphene-like structure were formed on the surface of the solution. The structure of the films was studied by high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FT-IR), etc. The results demonstrated that the films were formed by the self-assembly of CDs under the action of the gas–liquid interface template and the metal catalyst. Meanwhile, the electrochemical performance of the films was evaluated by linear cyclic voltammetry (CV) and galvanostatic charge discharge (GOD) tests. In addition, the bulk solution could be further reacted and self-assembled by reflux to form a bifunctional magnetic–fluorescent composite material. Characterizations such as X-ray diffractometer (XRD), fluorescence spectra (FL), vibrating sample magnetometer (VSM), etc. revealed that it was a composite of superparamagnetic γ-Fe₂O₃ and CDs. The results showed that self-assembly of CDs is a novel and effective method for preparing new carbon nanomaterials.     

Label free DNA detection based on gold nanoparticles quenching fluorescence of Rhodamine B

A novel and sensitive label free DNA detection method using gold nanoparticles (GNPs) and Rhodamine B (RB) has been developed. The assay is based on the following two properties. One is the different adsorption properties of single-stranded and double-stranded DNA on GNPs in colloidal solution. The other is the different quenching ability of aggregated GNPs and dispersed GNPs on RB. Un-aggregated GNPs could effectively quench the fluorescence of RB. However, the quenching ability greatly decreases after GNPs aggregated. The hybridization of probe DNA and target DNA is monitored by the fluorescence detection after the RB is added to the solution. Under the optimal experimental conditions, the detection limit of this assay is 2.9×10(-13) mol L(-1).     

Anionic-cationic switchable amphoteric monodisperse mesoporous silica nanoparticles

Anionic-cationic switchable monodisperse mesoporous silica nanoparticles were synthesized by one-pot amino and carboxylic acid bifunctionalization based on the self-assembly of the surfactant, two types of co-structure-directing agents containing amino and carboxylic groups, and silica sources. These nanoparticles revealed properties of dispersity and reversibility, with the advantage of the pH-responsive anionic-cationic/acid-base switchability. It was demonstrated that the extracted materials achieved reutilization and controllable dispersity in aqueous solution by adjusting the static electric power among the particles during the switching process.