一种改进型超宽带喇叭天线

基于TEM喇叭天线的结构特点,用两根弯曲的窄带代替基本模型中的上板,设计了一种飘带喇叭天线。该设计不仅有效地提高了天线的低频利用率,并且实现了天线的轻量化。通过对飘带结构进行进一步改进,利用AnsoftHFSS仿真软件对模型进行了分析。结果表明,改进后的飘带喇叭天线不但有较好的超宽带性能,而且其辐射性能也有了较大提高。...     

Determination of Mixing Times with Helical Ribbon Impeller for Non‐Newtonian Viscous Fluids Using an Advanced Imaging Method

New results on mixing times for viscous Newtonian and non‐Newtonian fluids being homogenized with a helical ribbon impeller are presented. In particular, a recently developed technique to determine the macromixing kinetics of an impeller in a transparent vessel was applied to investigate the effects of rheological properties on mixing times. Significant differences were observed in the mixing times for viscous Newtonian and non‐Newtonian fluids. Based on the new data obtained in this work, a correlation incorporating the elastic effects is proposed in terms of a Weissenberg number for predicting the mixing time as a function of the Reynolds number and the system geometry.     

多芯片组件中金丝金带键合互连的特性比较

金丝、金带键合已经广泛应用于毫米波多芯片组件的互连之中。本文讨论了在20－40GHz 频率范围内,单根、两根、三根金丝和金带连接的性能。测试结果表明两根和三根金丝连接的性能优于金带连接的性能,金带连接的性能优于单金丝连接的性能。     

新型绕带式压力容器技术的突出发展优势

指出了21世纪压力容器构造技术发展的要求和方向,对德国的整体夹钳包扎高压容器构造技术进行了评价,着重论述了我国的新型线带式压力容器在具有抗爆安全特性、降低成本达40％以及钢复合结构设计灵活等方面所占的突出竞争优势。     

Spatially resolved investigations of lifetime enhancement in vertically grown, multicrystalline silicon ribbons

The influence of gettering or defect passivation steps on recombination activity in the vertically grown, multicrystalline ribbon materials edge-defined film-fed growth and string ribbon silicon has been investigated with the help of photoconductance decay. In contrast to well-known results of integral measurements, spatially resolved lifetime mappings have been obtained by applying microwave detection technique.This aspect of spatial resolution has been found to be indispensable for investigating the impact of different processing steps on material quality in an accurate way. Apart from strong variations in as-grown lifetimes that have been found throughout vertically grown silicon wafers, this is due to areas of comparable starting lifetimes which have been revealed to react very differently to applied processing steps. After processing, some of them reach minority charge carrier lifetimes of more than 300 μs whereas others just show values of a few microseconds. As a consequence, the results of integral measurements strongly depend on the nature of areas incorporated in the specific sample. An impression of the corresponding uncertainties inherent to integral measurements has been obtained by statistical evaluation of spatially resolved lifetime data.     

带状光缆接续中的有关问题

讨论了带状光缆接续中的一些技术和操作上的问题，指出了一些应注意的事项。     

Characterization of the thermal and fluid flow behavior of industrial ribbon burners

This study focuses on the key parameters that enhance the stability of ribbon burners used in various industrial processes, characterizing the flame environment and flow regimes that the burner creates under changing operating conditions. The research includes the exploration of ribbon-pack configurations in order to define the effects of separation distance and port arrangement on flame stability and thermal and fluid flow. Flow visualization studies reveal that burners having a 1.5–2.0 mm division between rows appear to be the most stable. More than four rows of ports in the ribbon-pack are required to resist entrainment of ambient air as a result of impinging surface motion. The flame environment created by the ribbon burner experiences higher levels of mixing, at a lower Reynolds number in comparison to a single non-reacting jet due to combustion-induced turbulence and jet interaction. Under these high flow velocity conditions there is little entrainment of ambient air along the impingement surface and a very stable flame environment is created.     

Rheology and sedimentation velocity of alkaline suspensions of hematite particles at elevated temperature

This study aims to characterize the sedimentation velocity and the rheology of suspensions of hematite particles suspended in strongly alkaline media at 100 and 110 °C, as done for an alternative electrochemical process in development for iron production by direct electrode reduction of hematite. Considering the medium used in the process, i.e. 12% (v/v) suspension of hematite particles in 50% sodium hydroxide aqueous, the sedimentation velocity of hematite particle at 110 °C is 0.010 mm/s, which is very slow because the average size of the solid particles is around 10 μm and the significant collisions and interactions occuring between the particles in the concentrated suspension. Two geometries were used to characterize the rheological behavior of the apparent viscosity of the suspension of 12% (v/v) (i.e. 33 wt%) at 100 °C: a conventional Couette geometry and a helical ribbon mixer. The suspension was found shear thinning in the range of shear rate studied. The rheological behavior of the suspension can be described by a power-law model. The apparent viscosity of the hematite suspension estimated at a shear rate between 0.5 and 10 s⁻¹ is between 100 and 20 mPa s for the two geometries. The apparent viscosity calculated from the terminal velocity of 10 μm particles is of the same order of magnitude of the results obtained with the two rheometer configurations. The effect of the particle concentration on the sedimentation velocity and viscosity of the hematite suspensions was also studied.     

ANN Analysis of a Roller Compaction Process in the Pharmaceutical Industry

Dry granulation via a roller compactor was simulated based on the artificial neural network (ANN) methodology. Two process parameters, including roll force and screw speed, were considered as input of the simulation whereas ribbon density was considered as output. Experimental work was carried out using an industrial‐scale roller compactor. The results showed an excellent agreement between simulation and experiments. The findings were compared as well with the results obtained in a previous study employing the Johanson model, which is the predominant model for the simulation of a roller compaction process. The overall deviation observed for the developed ANN model was found to be significantly improved in comparison with the deviation obtained for the Johanson model. The results demonstrated a very good capability and robustness of the developed ANN model in design and optimization of the roller compaction process.