Monolithic integration of a 5.3 GHz regenerative frequency divider using a standard bipolar technology

A monolithic microwave frequency divider IC with an operating range of 1.4?5.3 GHz was developed and fabricated in a standard bipolar technology. The circuit operates on the principle of `regenerative frequency division?. Compared to the most popular divider concepts based on a master-slave D-flip-flop, an almost twice as high input frequency can be divided, provided that the same technology is used. A further advantage is the low power consumption.     

Numerical modeling of multiphase flows in microfluidics and micro process engineering: a review of methods and applications

This article presents a comprehensive review of numerical methods and models for interface resolving simulations of multiphase flows in microfluidics and micro process engineering. The focus of the paper is on continuum methods where it covers the three common approaches in the sharp interface limit, namely the volume-of-fluid method with interface reconstruction, the level set method and the front tracking method, as well as methods with finite interface thickness such as color-function based methods and the phase-field method. Variants of the mesoscopic lattice Boltzmann method for two-fluid flows are also discussed, as well as various hybrid approaches. The mathematical foundation of each method is given and its specific advantages and limitations are highlighted. For continuum methods, the coupling of the interface evolution equation with the single-field Navier–Stokes equations and related issues are discussed. Methods and models for surface tension forces, contact lines, heat and mass transfer and phase change are presented. In the second part of this article applications of the methods in microfluidics and micro process engineering are reviewed, including flow hydrodynamics (separated and segmented flow, bubble and drop formation, breakup and coalescence), heat and mass transfer (with and without chemical reactions), mixing and dispersion, Marangoni flows and surfactants, and boiling.     

Photometer measurement of polydisperse aerosols

The photometer measurement of respirable aerosol mass concentration is widely employed in air pollution monitoring. Using the Mie theory of light scattering and the built-in optical parameters of some photometers, the output signal was theoretically calculated and related to the real aerosol mass concentration.. The definition of the mass sensitivity in combination with the device calibration constants enables the photometer response bias calculation as a function of the main aerosol parameters (index of refraction, particle density, particle size distribution). The respirable fraction (Soderholm (1989) Ann. occup. Hyg. 33, 301–320; Comité Européen de Normalisation (1993) EN 481; International Standards Organisation (1993) DIS 7708; American Conference of Governmental Industrial Hygienists (1994) Cincinnati, OH, pp. 42–45) of the ambient aerosol was used as a reference concentration for the calculation of the bias. The photometer response bias maps were built for four mineral dusts and a wide range of their aerosol distributions. The method makes possible an estimation of the photometer response bias in measuring various aerosols when the instrument is calibrated against any other aerosol.     

Map‐based Visualizations Increase Recall Accuracy of Data

We investigate the memorability of data represented in two different visualization designs. In contrast to recent studies that examine which types of visual information make visualizations memorable, we examine the effect of different visualizations on time and accuracy of recall of the displayed data, minutes and days after interaction with the visualizations. In particular, we describe the results of an evaluation comparing the memorability of two different visualizations of the same relational data: node‐link diagrams and map‐based visualization. We find significant differences in the accuracy of the tasks performed, and these differences persist days after the original exposure to the visualizations. Specifically, participants in the study recalled the data better when exposed to map‐based visualizations as opposed to node‐link diagrams. We discuss the scope of the study and its limitations, possible implications, and future directions.     

Stiction issues and actuation of RF LIGA-MEMS variable capacitors

High aspect ratio variable capacitors have been fabricated using deep X-ray lithography and electroplating. Stiction phenomena applicable to high aspect ratio devices are presented, including the conditions for stiction to occur and the critical dimensions of structures. Actuation tests at 3 GHz are also presented and show a maximum capacitance of 0.86 pF with no actuation voltage and a minimum capacitance of 0.70 pF with an actuation voltage of 20 V just before pull-in, which gives a tuning range of 1.23:1. Corresponding Q-factor values are 49.3 and 70.8 respectively. After pull-in, the measured capacitance is 0.61 pF, corresponding to a tuning range of 1.41:1, with a maximum Q-factor of 102.9.     

Ultralow Expansion Glass as Material for Advanced Micromechanical Systems

Ultralow expansion (ULE) glasses are of special interest for temperature stabilized systems for example in precision metrology. Nowadays, ULE materials are mainly used in macroscopic and less in micromechanical systems. Reasons for this are a lack of technologies for parallel fabricating high-quality released microstructures with a high accuracy. As a result, there is a high demand in transferring these materials into miniaturized application examples, realistic system modeling, and the investigation of microscopic material properties. Herein, a technological base for fabricating released micromechanical structures and systems with a structure height above 100 μm in ULE 7972 glass is established. Herein, the main fabrication parameters that are important for the system design and contribute thus to the introduction of titanium silicate as material for glass-based micromechanical systems are discussed. To study the mechanical properties in combination with respective simulation models, microcantilevers are used as basic mechanical elements to evaluate technological parameters and other impact factors. The implemented models allow to predict the micromechanical system properties with a deviation of only ±5% and can thus effectively support the micromechanical system design in an early stage of development.     

Using Selective Electron Beam Melting to Enhance the High-Temperature Strength and Creep Resistance of NiAl–28Cr–6Mo In Situ Composites

By increasing the density of interfaces in NiAl–CrMo in situ composites, the mechanical properties can be significantly improved compared to conventionally cast material. The refined microstructure is achieved by manufacturing through electron beam powder bed fusion (PBF-EB). By varying the process parameters, an equiaxed or columnar cell morphology can be obtained, exhibiting a plate-like or an interconnected network of the (Cr,Mo) reinforcement phase which is embedded in a NiAl matrix. The microstructure of the different cell morphologies is investigated in detail using scanning electron microscope, transmission electron microscopy, and atom probe tomography. For both morphologies, the mechanical properties at elevated temperatures are analyzed by compression and creep experiments parallel and perpendicular to the building direction. In comparison to cast NiAl and NiAl–(Cr, Mo), the yield strength of the PBF-EB fabricated specimens is significantly improved at temperatures up to 1,027 °C. While the columnar morphology exhibits the best improved mechanical properties at high temperatures, the equiaxial morphology shows nearly ideal isotropic mechanical behavior, which is a substantial advantage over directionally solidified material.     

Domain science and engineering from computer science to the sciences of informatics. Part I: Engineering

In this paper, we wish to advocate that departments of computer science put emphasis on teaching programming and software engineering based on formal methods; and more emphasis on research into formal methods for the trustworthy development of software. We also wish to advocate that the concepts of domain science and domain engineering become an indispensable part of the science of informatics and of software engineering.