无线技术拓展过程控制的视野

使用新型的无线技术，能够方便快捷地采集和传递以往难以访问的现场数据，这无疑为现代过程控制领域打开了一个视野更为开阔的窗口。     

Micromechanical modeling of grain boundary resistance to cleavage crack propagation in ferritic steels

In ferritic steels a propagating cleavage microcrack changes its propagation direction as it advances from grain to grain. This is due to differences in the orientation of the cleavage planes of two neighboring grains. In order to reach a cleavage plane in a new grain, a microcrack must first penetrate the grain boundary. Grain boundaries therefore act as natural barriers in cleavage fracture. The influence of a grain boundary and the associated misorientation in cleavage planes on crack arrest is here examined using a 3D finite element model with axisymmetric periodicity, representing two grains whose cleavage planes are tilted and twisted relative to each other. The temperature dependent mechanical properties of ferrite are modeled using a temperature dependent viscoplastic response. The development of the crack front as the microcrack penetrates through a grain boundary is here presented. The influence of the twist misorientation on the critical grain size, defined as the largest grain size that can arrest a rapidly propagating microcrack, is examined in a temperature range corresponding to the ductile to brittle transition (DBT) region. It is shown that when both tilt and twist misorientation are present, the influence of tilt and twist, respectively, on crack growth resistance can be decoupled.     

Wideband Low‐Reflection Transmission Lines for Bare Chip on Multilayer PCB

The pad pitch of modern radio frequency integrated circuits is in the order of few tens of micrometers. Connecting a large number of high‐speed I/Os to the outside world with good signal fidelity at low cost is an extremely challenging task. To cope with this requirement, we need reflection‐free transmission lines from an on‐chip pad to on‐board SMA connectors. Such a transmission line is very hard to design due to the difference in on‐chip and on‐board feature size and the requirement for extremely large bandwidth. In this paper, we propose the use of narrow tracks close to chip and wide tracks away from the chip. This narrow‐to‐wide transition in width results in impedance discontinuity. A step change in substrate thickness is utilized to cancel the effect of the width discontinuity, thus achieving a reflection‐free microstrip. To verify the concept, several microstrips were designed on multilayer FR4 PCB without any additional manufacturing steps. The TDR measurements reveal that the impedance variation is less than 3 Ω for a 50 Ω microstrip and S11 better than –9 dB for the frequency range 1 GHz to 6 GHz when the width changes from 165 µm to 940 µm, and substrate thickness changes from 100 µm to 500 µm.     

Reversibly erasable nanoporous anti-reflection coatings from polyelectrolyte multilayers

For nearly two centuries, researchers have sought novel methods to increase light transmission in optical systems, as well as to eliminate unwanted reflections and glare. Anti-reflection coatings and surfaces have enabled the increasing performance demands of optical components fabricated from glass-based optical materials. With the current trend of technology moving towards optically transparent polymeric media and coatings, the need for anti-reflection technology and environmentally benign processing methods for polymeric materials independent of shape or size has become quite apparent. We describe an economical, aqueous-based process controlled at the molecular level that simultaneously coats all surfaces of almost any material. Systematically designed nanoporous polymer films are used, which are suitable for optical applications operating at both visible and near-infrared wavelengths. These high-efficiency anti-reflection coatings are created from phase-separated polyelectrolyte multilayer films that undergo a reversible pH-induced swelling transition. Furthermore, such films, easily patterned by an inkjet printing technique, possess potential for pH-responsive biomaterial and membrane applications.     

Self-contained microelectrochemical immunoassay for small volumes using mouse IgG as a model system

A self-contained, microelectrochemical immunoassay on the smallest volumes reported to date (1 microL for the antigen, 1 microL for the secondary antibody-enzyme conjugate, and 200 nL for the electrochemically detected species) has been developed using mouse IgG as a model system in a sandwich-type enzyme-linked immunosorbant assay, which takes less than 30 min to both complete the assembly of immunoassay components onto the antibody-modified surface and detect enzymatically generated species (excluding time for electrochemical cleaning of electrodes). These studies demonstrate the advantage of the close proximity of electrodes to modified surfaces and their application in the analysis of small volumes. Using a 50 microm diameter x 8 microm deep cavity with individually addressable electrodes on a microfabricated chip, the primary antibody was selectively and covalently attached at a gold, recessed microdisk (RMD) at the bottom of the microcavity to the free end of SAMs of either 11-mercaptoundecanoic acid or 11-mercapto-1-undecanol using 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide hydrochloride. Nonspecific adsorption to the surrounding material, polyimide, of the microcavity device was eliminated. Electrochemical desorption was used to confine the immunoassay activity at the RMD. Enzymatic conversion of the substrate p-aminophenyl phosphate top-aminophenol is detectable in less than 30 s using cyclic voltammetry at a gold, tubular nanoband electrode, which is on the wall of the microcavity and immediately adjacent to the modified RMD. A third electrode, also within the region of the microcavity, served as the pseudoreference/auxiliary electrode. Calibration curves obtained for 1-microL solutions of 5-100 ng/mL of IgG and for 200 nL-solutions of 5 microM to 4 mM of PAPR gave detection limits of 4.4 nM (6.4 ng/mL) or 880 fmol (129 pg) for PAPR and 56 fM (9 pg/mL) or 56 zmol (9 fg) for IgG. It is expected that the device may be suitable for analysis with volumes down to tens of picoliters.     

Prediction of chromatographic retention and protein identification in liquid chromatography/mass spectrometry

Liquid chromatography coupled on- or off-line with mass spectrometry is rapidly advancing as a tool in proteomics capable of dealing with the inherent complexity in biology and complementing conventional approaches based on two-dimensional gel electrophoresis. Proteins can be identified by proteolytic digestion and peptide mass fingerprinting or by searching databases using short-sequence tags generated by tandem mass spectrometry. This paper shows that information on the chromatographic behavior of peptides can assist protein identification by peptide mass fingerprinting in liquid chromatography/mass spectrometry. This additional information is significant and already available at no extra experimental cost.     

Uzawa Conjugate Gradient Domain Decomposition Methods for Coupled Stokes Flows

This paper deals with nonoverlapping domain decomposition methods for two coupled Stokes flows, based on the duality theory. By introducing a fictitious variable in the transmission condition and using saddle-point equations, the problem is restated as a linearly constrained maximization problem. According to whether constraints are uncoupled Stokes problems or uncoupled Poisson problems, two Uzawa-type domain decomposition algorithms are proposed. The results of some numerical experiments on a model problem are given.