Structural protection using MR dampers with clipped robust reliability-based control

Magnetorheological (MR) damper is one of the most promising semi-active control devices for mitigating seismic response, and so, it has received significant attention in recent years. Because of the inherent nonlinear nature of MR damper devices, one challenge to effectively utilize this technology is the development of an appropriate control algorithm. A semi-active control methodology is presented to control structural systems using MR dampers that addresses structural modeling uncertainties. Based on the same idea as the clipped-optimal linear controller, the proposed semi-active control law uses a robust reliability-based active linear control methodology to calculate the reference control forces that the MR dampers attempt to produce approximately. These reference control forces can be calculated using incomplete response measurements at the current and/or previous time steps without any state estimation. The main purpose of the proposed approach is to achieve a more robust performance for uncertain structural systems subjected to uncertain strong-motion excitation. The performance of the proposed approach is demonstrated through a simulated example of a ten-story building with MR dampers installed. Y. Shi formerly from the Department of Civil and Environmental Engineering, University of Macau, Macau SAR, China.     

Assessment of Microarray Data Clustering Results Based on a New Geometrical Index for Cluster Validity

A measurement of cluster quality is often needed for DNA microarray data analysis. In this paper, we introduce a new cluster validity index, which measures geometrical features of the data. The essential concept of this index is to evaluate the ratio between the squared total length of the data eigen-axes with respect to the between-cluster separation. We show that this cluster validity index works well for data that contain clusters closely distributed or with different sizes. We verify the method using three simulated data sets, two real world data sets and two microarray data sets. The experiment results show that the proposed index is superior to five other cluster validity indices, including partition coefficients (PC), General silhouette index (GS), Dunn’s index (DI), CH Index and I-Index. Also, we have given a theorem to show for what situations the proposed index works well.     

Super-resolution reconstruction in a computational compound-eye imaging system

From consumer electronics to biomedical applications, device miniaturization has shown to be highly desirable. This often includes reducing the size of some optical systems. However, diffraction effects impose a constraint on image quality when we simply scale down the imaging parameters. Over the past few years, compound-eye imaging system has emerged as a promising architecture in the development of compact visual systems. Because multiple low-resolution (LR) sub-images are captured, post-processing algorithms for the reconstruction of a high-resolution (HR) final image from the LR images play a critical role in affecting the image quality. In this paper, we describe and investigate the performance of a compound-eye system recently reported in the literature. We discuss both the physical construction and the mathematical model of the imaging components, followed by an application of our super-resolution algorithm in reconstructing the image. We then explore several variations of the imaging system, such as the incorporation of a phase mask in extending the depth of field, which are not possible with a traditional camera. Simulations with a versatile virtual camera system that we have built verify the feasibility of these additions, and we also report the tolerance of the compound-eye system to variations in physical parameters, such as optical aberrations, that are inevitable in actual systems.     

New Versions of Bounded Real Lemmas for Continuous and Discrete Uncertain Systems

New bounded real lemmas for linear systems with parameter uncertainties belonging to a convex bounded-polyhedral domain are established in this paper. Both continuous- and discrete-time uncertain systems are investigated. The derived conditions are expressed in terms of a set of linear matrix inequalities defined at the vertices of the uncertainty polytope. Numerical comparisons with those appearing recently in the literature show that the proposed conditions provide less conservative results.     

Comparison of Weibull small samples using Monte Carlo simulations

The evaluation of the functional reliability of different designs is a common task and times to failure can be compared using the likelihood ratio test. In the microelectronics industry, as in many others, the high cost of testing places severe restrictions on the sample size. Moreover, the products in these tests are often new and do not have previous reliability histories. These factors make the selection of the Type I and Type II errors in comparison tests very difficult. This paper presents the Monte Carlo simulation results of Type II errors for the likelihood ratio test of comparison as a function of the Type I error and the (small) sample size. Our conclusions are summarized as follows: (1) the common microelectronics industry standard sample size of 32 is often insufficient to reach satisfactory conclusions; (2) small sample tests should only be used for prescreening for significant differences; and (3) when only small samples are available, the Type I and the Type II errors must be selected carefully to prevent misleading conclusions. Copyright © 2006 John Wiley & Sons, Ltd.     

Thermal debinding modeling of mass transport and deformation in powder-injection molding compact

A two-dimensional model of mass transport and deformation in thermal debinding for the powder-injection molding (PIM) compact, based on mass and heat transfer in deformable porous media and elasticity theory, is proposed. The primary mechanisms of mass transport, i.e., liquid flow, gas flow, vapor diffusion, and convection, as well as heat transfer, polymer pyrolysis, powder-particle packing, compact deformation, and their interactions are simultaneously included in the model. A computer code, in which integrated control-volume finite-difference and finite-element methods are employed, is developed to simulate the process. The simulated results revealed that the nonuniform distribution of polymer residue, which results from the nonuniform flow of the polymer, causes the nonuniform deformation in the compact. Severe nonuniform deformation in the compact might lead to cracking, distortion, and failure of the compact during the polymer-removal process.     

Diagnosis of Trypanosoma evansi in Saudi Arabian camels (Camelus dromedarius) by the passive haemagglutination test and Ag-ELISA

The passive haemagglutination test and Ag-ELISA were employed to monitor antibody titres and antigenaemia levels in 4 Najdi camels experimentally infected with Trypanosoma evansi. The two tests were also used to determine the prevalence of trypanosomiasis in a total of 218 Najdi camels in the Gassim region, Central Saudi Arabia, during the period from October 1992 to September 1993. Trypanosoma evansi antibodies in the experimentally infected camels rose after 14-21 days and reached a maximum of between 1:64 and 1:128 by the 12th week post infection. Circulating antigens were detected in the experimentally infected camels one week post infection and antigenaemia levels fluctuated but generally remained above preinfection OD values. The results obtained from the field survey showed that 5.5% of the sampled camels were parasitologically positive for trypanosomes, while 19.7% were serologically positive by the passive haemagglutination test and 13.8% by Ag-ELISA. No significant age difference in seropositivity was observed in the tested camels.     

Horizontal gas pressure and temperature distribution responses to OSB flake alignment during hot-pressing

This study examines the effect of different flake alignments and densities on horizontal heat and gas flow from the mat centre to the edges. Robot-formed 660×660 mm single layer oriented-strandboard (OSB) mats, with various flake alignment distributions, were hot-pressed at 180°C to 10 mm thickness. Fine gauge thermocouple wire and steel capillary tubes were built into the mat to monitor core temperatures and gas pressures at ten locations across the board-plane. Results confirm the existence of lateral temperature and gas pressure gradients across the mat, with its edges having lower temperatures and pressures than its interior. Flake alignment was seen to skew the lateral gradients in the alignment directions, the extent being strongly influenced by interactions with mat density and the proximity to the edge. In highly aligned mats, lower temperatures and pressures were measured along the alignment direction than perpendicular to it, thus indicating greater heat and mass transfer along the flake alignment axis. These horizontal temperature and pressure distributions have practical implications on panel uniformity and quality as mat consolidation is dependent on internal conditions during hot-pressing.

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Horizontaler Gasdruck und Temperaturverteilungsreaktionen auf OSB-Spanausrichtung während Heißpressung

Zusammenfassung Diese Studie untersucht die Auswirkung von unterschiedlichen Spanausrichtungen und Dichten auf den horizontalen Hitze- und Gasfluss vom Mattenzentrum zu den Kanten. Roboter-geformte 660×660 mm einschichtige OSB-Matten mit unterschiedlichen Spanausrichtungsverteilungen wurden bei 180°C zu 10 mm Dicke heißgepresst. Dünne Temperaturfühler und Stahlkapillarröhren wurden in die Matte eingebaut, um an 10 Stellen über die Plattenebene verteilt Kerntemperaturen und Gasdrucke aufzuzeichnen. Die Ergebnisse bestätigen das Vorhandensein von lateralen Temperatur- und Gasdruck-Gradienten über die Matte, wobei an den Kanten niedrigere Temperaturen und Drucke vorherrschen als im Inneren. Es wurde beobachtet, dass die Spanausrichtung die lateralen Gradienten in den Ausrichtungsrichtungen abweicht, wobei die Ausdehnung stark durch Interaktionen zwischen Mattendichte und der Nähe zur Kante beeinflusst wurde. In hoch ausgerichteten Matten wurden entlang der Ausrichtung niedrigere Temperaturen und Drucke gemessen als senkrecht dazu, auf diese Weise wurden eine größere Hitze- und Masseübertragung entlang der Spanausrichtungsachse angezeigt. Diese horizontalen Temperatur- und Druckverteilungen haben praktische Implikationen auf Platten-Uniformität und Qualität, da die Matten-Konsolidierung von inneren Bedingungen während der Heißpressung abhängt.

     

Atomistic observation and simulation analysis of spatio-temporal fluctuations during radiation-induced amorphization

We performed a dynamical-atomistic study of radiation-induced amorphization in the NiTi intermetallic compound using in situ high-resolution high-voltage electron microscopy and molecular dynamics simulations in connection with image simulation. Spatio-temporal fluctuations as non-equilibrium fluctuations in an energy-dissipative system, due to transient atom-cluster formation during amorphization, were revealed by the present spatial autocorrelation analysis.