Qualitative features of matrix pencils and DAEs arising in circuit dynamics

The dynamical behaviour of nonlinear electrical circuits is usually modelled in the time domain by differential-algebraic equations (DAEs). The differential-algebraic formalism drives qualitative analyses based on linearization to a matrix pencil setting. In this context, the present paper performs a spectral analysis of matrix pencils and DAEs arising in nonlinear circuit theory. Specifically, the non-singularity, hyperbolicity and asymptotic stability of equilibria are addressed in terms of circuit topology. The differential-algebraic framework puts the results beyond those already known for state-space models, unfeasible in many actual problems. The topological conditions arising in this qualitative study are proved independent of those supporting the index, and therefore they apply to both index-1 and index-2 configurations. The approach illustrates how graph theory, matrix analysis and DAE theory interact in the dynamical study of nonlinear circuits.     

On the stability of solutions of autonomous index-I tractable and quasilinear index-2 tractable DAEs

Conclusion We have seen that the stationary solutions of the regularized equations are asymptotically stable if the stationary solution of the original quasilinear index-2 tractable DAE is so. In other words, the given regularizations supply a solution sharing the stability properties of the solution of the unperturbed equation.     

Hard and soft magnetic materials for electromagnetic microactuators

An important aspect of the development of electromagnetic microactuators is the search for suitable materials as well as the development of the respective deposition and patterning processes. Within the Collaborative Research Center 516 “Design and Fabrication of Active Microsystems”, it is the task of the subproject B1 “fabrication of magnetic thin films for electromagnetic microactuators” to perform these investigations. The materials of interest can be divided into two groups: hard magnetic materials and soft magnetic materials. Materials with optimized properties and fabrication processes have been developed within both groups. An example is Samarium–Cobalt (SmCo), which can either be deposited using magnetron sputtering as Sm₂Co₁₇ with a very high energy product or in the SmCo₅ phase using gas flow sputtering with very high deposition rates. In the area of soft magnetic materials, investigations on Nickel-Iron (NiFe) especially NiFe81/19 were followed by the evaluation of NiFe45/55, which features a higher saturation flux density B _s and relative permeability μ _r. Furthermore, current investigations focus on Cobalt-Iron (CoFe) and its further increased saturation flux density B _s and relative permeability μ _r. Current tasks include the stabilization of the fabrication processes to achieve good material properties (i.e. electroplating of CoFe) or a shortening (e.g. by using heated substrates during deposition) by using process alternative not used so far. Another topic is the integration into fabrication processes, i.e. the investigation of process stability and compatibility.     

Effect of Ni and SAPO-34 co-additive on enhancing hydrogen storage performance of MgH2

The hydrogen storage performances of MgH₂ improved by the addition of Ni and SAPO-34 were studied in detail. The mixture of MgH₂ with Ni and SAPO-34 was a physical reaction as shown by the X-ray diffraction (XRD) results. The SAPO-34 and Ni were uniformly distributed on the surface of MgH₂. The thermodynamic and kinetic properties of 90MgH₂/5Ni/5SAPO-34 were investigated by differential scanning calorimetry (DSC) and pressure-composition-isothermal (PCI) methods. The results showed that the dehydrogenation activation energy of 90MgH₂/5Ni/5SAPO-34 decreased by 64.3 kJ/mol compared with that of MgH₂. In addition, the relationship between the value of dehydrogenation heat and hydrogen content was also investigated by in-situ calorimetry. The enthalpy value of each sample in the dehydrogenation processes were calculated by in-situ calorimetry measurement. The dehydrogenation enthalpies of as-milled MgH₂ and 90MgH₂/5Ni/5SAPO-34 were 63.2 kJ/mol H₂ and 53.6 kJ/mol H₂, respectively. Thus, the co-doping of Ni and SAPO-34 contributed significantly to decrease the thermodynamic stability and improve the hydrogen sorption kinetic properties of MgH₂.     

Using MCRDR based Agile approach for expert system development

Various expert system development approaches were proposed but most of them cannot deal with two problems: the difficulty of analysis and maintenance. Rather than to spend time waiting any longer, it is better to find an alternative solution from other research fields. In computer software development area, researchers have been suffering from the difficulty of maintenance and analysis, just as the researchers in the expert system development field. To solve this issue, researchers in the software used both agile software development and business rules approach: agile software development is for overcoming the the difficulty of analysis, and business rules approach is for reducing issues in the maintenance. There is a big opportunity that those two approaches can also be solve the two issues in the expert system development field. The paper describes requirements of the approach based on agile software development and the business rules approach. As a result, we consider and specify why the Multiple Classification Ripple Down Rules is the novel approach for the expert system development.     

NGF Enhances CGRP Release Evoked by Capsaicin from Rat Trigeminal Neurons: Differential Inhibition by SNAP-25-Cleaving Proteases

Nerve growth factor (NGF) is known to intensify pain in various ways, so perturbing pertinent effects without negating its essential influences on neuronal functions could help the search for much-needed analgesics. Towards this goal, cultured neurons from neonatal rat trigeminal ganglia—a locus for craniofacial sensory nerves—were used to examine how NGF affects the Ca²⁺-dependent release of a pain mediator, calcitonin gene-related peptide (CGRP), that is triggered by activating a key signal transducer, transient receptor potential vanilloid 1 (TRPV1) with capsaicin (CAP). Measurements utilised neurons fed with or deprived of NGF for 2 days. Acute re-introduction of NGF induced Ca²⁺-dependent CGRP exocytosis that was inhibited by botulinum neurotoxin type A (BoNT/A) or a chimera of/E and/A (/EA), which truncated SNAP-25 (synaptosomal-associated protein with Mr = 25 k) at distinct sites. NGF additionally caused a Ca²⁺-independent enhancement of the neuropeptide release evoked by low concentrations (<100 nM) of CAP, but only marginally increased the peak response to ≥100 nM. Notably, BoNT/A inhibited CGRP exocytosis evoked by low but not high CAP concentrations, whereas/EA effectively reduced responses up to 1 µM CAP and inhibited to a greater extent its enhancement by NGF. In addition to establishing that sensitisation of sensory neurons to CAP by NGF is dependent on SNARE-mediated membrane fusion, insights were gleaned into the differential ability of two regions in the C-terminus of SNAP-25 (181–197 and 198–206) to support CAP-evoked Ca²⁺-dependent exocytosis at different intensities of stimulation.     

Semistate models of electrical circuits including memristors

In this paper we present several semistate or differential‐algebraic models arising in nodal analysis of nonlinear circuits including memristors. The goal is to characterize the tractability index of these models under strict passivity assumptions, a key issue for the numerical simulation of circuit dynamics. We show that the main model, which combines memristors' fluxes and charges, is index two. From a technical point of view, this result is based on the use of a projector along the image of the leading matrix, in contrast to previous index analyses. For charge‐controlled memristors, the elimination of fluxes yields an index one system in topologically nondegenerate circuits, and an index two model otherwise. Analogous results are also proved to hold for flux‐controlled memristors. Our framework accommodates coupling effects among resistors, memristors, capacitors and inductors. Copyright © 2010 John Wiley & Sons, Ltd.     

An investigation on technologies to fabricate microcoils for miniaturized actuator systems

Within the framework of the Collaborate Research Center Design and Fabrication of Active Microsystems (Sonderforschungsbereich 516), one aspect is the development of fabrication technology for driving coil systems to be applied to in electromagnetic microactuators. The two key focus areas are the fabrication of high aspect ratio conductors and insulating them by applying planarizing polymer material. The research activities included the development of technologies like for UV depth lithography, electroplating through lithographic masks (galvanoforming), as well as embedding in and planarization by insulation material. Combining these technologies allows to create high aspect ratio integrated multi-layer coils with integrated magnetic flux guiding structures. The materials applied were copper as a conductor, NiFe for magnetic cores and the negative tone resists SU-8 (MicroChem Corp.) as well as BCB (DOW Chemical) for insulation and embedding purposes. For electroplating molds, the DNQ/Novolak type photoresists AZ4562 and AZ9260 (Clariant) were utilized. The established technologies were integrated into process flows for fabricating thick and high aspect ratio planar and helical coils for electromagnetic linear actuators.This work was sponsored in part by the German Research Foundation as part of their support for the Collaborative Research Center Design and Fabrication of Active Microsystems.     

Acoustic emission (AE) measurements to determine the dynamic flying characteristics of optical sliders

Flying heads carrying a magnetic coil and a high numerical aperture lens for magneto-optic recording or a solid immersion lens for optical phase change recording, respectively, are promising approaches for increasing the data density. A classic approach to dynamically evaluate the flight attitude of flying heads in data storage is acoustic emission (AE) testing of the head/disk interaction using special glide heads. In our paper we introduce the application of AE test heads for measuring the flying characteristics of optical far field and near field sliders. In comparison to conventional external AE sensors, i.e. sensors mounted somewhere in the drive, these AE elements are directly mounted on the sliders thus yielding a higher pulse shape and a better signal to noise ratio. This set-up allows a clear identification of the head disk contact. To calibrate the sensor a bump disk was fabricated and used for AE measurements.