Measurement technique for the thermal properties of thin-film diaphragms embedded in calorimetric flow sensors

In diaphragm-based micromachined calorimetric flow sensors, convective heat transfer through the test fluid competes with the spurious heat shunt induced by the thin-film diaphragm where heating and temperature sensing elements are embedded. Consequently, accurate knowledge of thermal conductivity, thermal diffusivity, and emissivity of the diaphragm is mandatory for design, simulation, optimization, and characterization of such devices. However, these parameters can differ considerably from those stated for bulk material and they typically depend on the production process. We developed a novel technique to extract the thermal thin-film properties directly from measurements carried out on calorimetric flow sensors. Here, the heat transfer frequency response from the heater to the spatially separated temperature sensors is measured and compared to a theoretically obtained relationship arising from an extensive two-dimensional analytical model. The model covers the heat generation by the resistive heater, the heat conduction within the diaphragm, the radiation loss at the diaphragm’s surface, and the heat sink caused by the supporting silicon frame. This contribution summarizes the analytical heat transfer analysis in the microstructure and its verification by a computer numerical model, the measurement setup, and the associated thermal parameter extraction procedure. Furthermore, we report on measurement results for the thermal conductivity, thermal diffusivity, and effective emissivity obtained from calorimetric flow sensor specimens featuring dielectric thin-film diaphragms made of plasma enhanced chemical vapor deposition silicon nitride.     

Trichloroacetic acid‐imprinted polypyrrole film and its property in piezoelectric quartz crystal microbalance and electrochemical sensors to application for determination of haloacetic acids disinfection by‐product in drinking water

A molecularly trichloroacetic acid (TCAA) imprinted non‐crosslinked polypyrole (TCAA‐MIPpy) has been successfully prepared and evaluated in its properties for both piezoelectric quartz crystal microbalance (QCM) and electrochemical means of detection, and application of such sensors for determination of haloacetic acid concentrations in water. Haloacetic acid selectivity was demonstrated in gravimetric or in electrochemical sensors via either cyclic voltammetric or inter‐digitated conductometric (IDC) analyses studies upon comparison with nonimprinted polypyrrole and TCAA‐imprinted polypyrrole. The measurement results with all these systems revealed that the prepared molecularly imprinted polymer can recognize TCAA well from structurally similar compounds. The TCAA‐MIPpy incorporated with only the IDC transduction system produced the specific signal for TCAA detection in aqueous environment, which is useful for the quantifying TCAA disinfection by‐product in water. The analytical application for determination of TCAA in real‐life samples was readily achieved with the incorporation of TCAA‐MIPpy in the IDC analysis system, the results revealing the high sensitivity and selectivity of the method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

采用遗传算法由电流环的近场测试识别辐射源

针对电大尺寸的电流环,通过遗传算法找到最佳等效基本辐射器.采用EMSCAN电磁干扰扫描系统进行电流环的近磁场测试,从而作出远场预测,并与仿真结果和半电波暗室的测试数据相比较.     

A Study on the Buckling Behaviour of Strips and Plates with Residual Stresses

During and after rolling or flattening of metal strips and plates the permissible deviations from flatness are described by the permissible absolute wave height and the flatness index. Both values can be determined on a measuring table while the material is not subjected to global tension. Because this procedure is expensive, time‐consuming and allows measurement only at discrete positions along the strip length, on‐line flatness measuring systems are used which can detect the distribution of longitudinal tensile stresses distributed across the strip width allowing for the calculation of the flatness index. This value does not always agree with the value obtained directly by measuring on the table even when the measurement of the longitudinal tensile stress distribution operates perfectly. It can be shown that the measurement of the tensile stress distribution does not give a direct indication on the wave height in the tension‐free state determined on the measuring table. To explain the relationship between tensile stress distribution in the strip and the flatness measurement on the measuring table, the buckling behavior is analysed both with and without dead load for simple symmetrical residual stress distributions resulting, e.g., from the rolling process. Based on the knowledge of the distribution of the longitudinal residual stresses across the strip width, the flatness index and the wave height can be determined by using a specialized finite element model. If the direct measurement is performed under action of dead load, large differences between the directly and indirectly obtained flatness index are observed. Below a certain limit of the intensity of the residual stress distribution the strips and plates lie flat on the measuring table. Above this limit the strip lying on the table exhibits post‐bucking deformations. In the latter case, the wave height increases with strip thickness and intensity of residual stresses.     

Experience with a Hybrid Processor: K-Means Clustering

We discuss hardware/software co-processing on a hybrid processor for a compute- and data-intensive multispectral imaging algorithm, k-means clustering. The experiments are performed on two models of the Altera Excalibur board, the first using the soft IP core 32-bit NIOS 1.1 RISC processor, and the second with the hard IP core ARM processor. In our experiments, we compare performance of the sequential k-means algorithm with three different accelerated versions. We consider granularity and synchronization issues when mapping an algorithm to a hybrid processor. Our results show that speedup of 11.8X is achieved by migrating computation to the Excalibur ARM hardware/software as compared to software only on a Gigahertz Pentium III. Speedup on the Excalibur NIOS is limited by the communication cost of transferring data from external memory through the processor to the customized circuits. This limitation is overcome on the Excalibur ARM, in which dual-port memories, accessible to both the processor and configurable logic, have the biggest performance impact of all the techniques studied.     

Dynamic linking of software components

Traditionally, dynamic linkers merely combined previously compiled pieces of code. Faster processors are now making outright code generation at load time practical, leading to cross-platform portability at very little extra cost. While the central idea behind dynamic linking is quite straightforward, it can be implemented through a surprising variety of strategies. The author contrasts three simple dynamic linking schemes with two much more elaborate strategies. The latter represent a workload shift from the compiler to the dynamic linker, just as dynamic linking itself represents a shift that moves the functions of a separate linker into the loader. Because the new techniques promise the profound additional benefit of cross-platform portability, they will most likely displace the currently popular linking-loader approach     

Sliding performance of polymer composites in liquid hydrogen and liquid nitrogen

Outstanding features favour the application of polymers and polymer composites in low-temperature technology. The booming hydrogen technology is a challenge for these materials, which are considered as seals and bearings in cryogenic pumps. In the present study, three types of thermoplastics, i.e., polyetheretherketone (PEEK), polyetherimide (PEI) and polyamide 6,6 (PA6,6), and one epoxy were considered as matrix materials. Micron-sized fillers, i.e., short carbon fibres, graphite flakes, and PTFE powders, were incorporated into these polymers together with nano-sized TiO₂ particles. Optimised compositions of each matrix were selected from our previous works at room temperature in order to be studied at very low temperature conditions. In particular, frictional tests were carried out with polymer composite pins against polished steel surfaces under constant load over a certain distance in liquid hydrogen and liquid nitrogen. Afterwards, worn surfaces were analysed by using scanning electron microscopy (SEM). It was found out that the tribological properties in liquid hydrogen are dominated by the matrix materials, in particular thermoplastics perform generally slightly better than thermosetting resins.     

Two realizations of a general feature extraction framework

A general feature extraction framework is proposed as an extension of conventional linear discriminant analysis. Two nonlinear feature extraction algorithms based on this framework are investigated. The first is a kernel function feature extraction (KFFE) algorithm. A disturbance term is introduced to regularize the algorithm. Moreover, it is revealed that some existing nonlinear feature extraction algorithms are the special cases of this KFFE algorithm. The second feature extraction algorithm, mean-STD¹-norm feature extraction algorithm, is also derived from the framework. Experiments based on both synthetic and real data are presented to demonstrate the performance of both feature extraction algorithms.     

Enhancement of limited water supply network data for deterioration modelling and determination of rehabilitation rate

In the past decades, the main focus of water supply management has moved from construction of new water supply networks to rehabilitation and adaptation of the existing infrastructure. The decision-making process for the rehabilitation management relies heavily on the quality of the applied deterioration model. A recurring problem in the application of such models relates to the quality and availability of network data. These data are often incomplete or unreliable because building measures and damages are only documented properly recently and the recovery of older data is difficult and expensive. A key point in rehabilitation planning is therefore data collection and data reconstruction. Consequently, the aim of this paper is to present a methodology for the enhancement of the available data of water supply networks and the prognosis of the necessary rehabilitation rates under limited data availability. Results indicate that the presented data reconstruction technique has advantages as compared to traditional data extrapolation. It also allows the reconstruction of fragmentary data about existing water supply and wastewater collection systems for the operating utilities. However, it cannot be used for reconstructing failure types as well as the whole information on pipes (e.g. more than two missing information).     

Bewertung von Abfallbehandlungsverfahren: Entscheidungsunterstützung durch die neue VDI‐Richtline 3925

The new VDI guideline 3925 presents assessment tools for the comparison of economic, ecological and also social aspects of different waste treatment processes. Objective of the guideline is to describe the application of suitable scientific and technical assessment methods to waste management strategies. The methods, their applicability, complexity, opportunities and limits are illustrated using practical examples.