Exponential ARX model-based long-range predictive control strategy for power plants

For nonlinear thermal power plants whose dynamics vary with load demand, a load-dependent exponential ARX (Exp-ARX) model, which can effectively describe the nonlinear properties of the plants, is presented. The Exp-ARX model requires only off-line identification. Based on the model, a constrained multivariable generalized predictive control (CMGPC) strategy is designed and implemented in a simulation of 375 MW thermal power plants. This CMGPC algorithm does not resort to on-line parameter estimation and can more exactly predict the future outputs of the nonlinear plants, so it shows better reliability and control performance than the usual GPC algorithm.     

Angular resolution of the Ohya air shower detector

Accurate measurements of the total number of muons in an air shower are important for the discrimination of showers produced by astronomical gamma rays from those produced by protons. In order to perform this discrimination, muon detectors with a total area of about 400 m² have been constructed in the Ohya stone mine. At ground level, scintillation detectors have been distributed for determining the total number of electrons in the air shower. The arrival direction of the air shower determined by usual timing information was examined using independent data on the arrival direction determined by muons in the shower. The angular resolution thus obtained at the shower maximum is 1.7° in the south-north plane and 2° in the east-west plane. The difference of the resolution is due to the asymmetric arrangement of scintillation detectors.     

Enhanced path smoothing based on conjugate gradient descent for firefighting robots in petrochemical complexes*

The firefighting robot system (FFRS) comprises several autonomous robots that can be deployed to fire disasters in petrochemical complexes. For autonomous navigation, the path planner should consider the robot constraints and characteristics. Specifically, three requirements should be satisfied for a path to be suitable for the FFRS. First, the path must satisfy the maximum curvature constraint. Second, it must be smooth for robots to easily execute the trajectory. Third, it must allow reaching the target location in a specific heading. We propose a path planner that provides smooth paths, satisfy the maximum curvature constraint, and allows a suitable robot heading. The path smoother is based on the conjugate gradient descent, and three approaches are proposed for this path planner to meet all the FFRS requirements. The effectiveness of these approaches is qualitatively and quantitatively evaluated by examining the generated paths. Finally, the path planner is applied to an actual robot to verify the suitability of the generated paths for the FFRS, and planning is applied to another type of robot to demonstrate the wide applicability of the proposed planner.     

Depressions of superfluid density and transition temperature of3he confined in small pores

Using fourth-sound techniques, the superfluid density of³He confined in three separately packed alumina powders having volume-averaged pore radius equal to 1.9, 0.44, and 0.18 µm were measured as a function of temperature at 10 pressures between 11 and 31 bar. Systematically larger depressions of superfluid density were observed as the pore size decreased. The measured pressure dependence of the depression of the superfluid transition temperature is consistent with that of the BCS expression for the coherence length. The quality factor of fourth-sound resonance was measured as a function of temperature at 20.5 and 30.9 bar. The highest quality factor measured was 40. The temperature dependence of the quality factor is in qualitative agreement with a theory by Jensen et al.     

Spatial indexing of high-dimensional data based on relative approximation

We propose a novel index structure, the A-tree (approximation tree), for similarity searches in high-dimensional data. The basic idea of the A-tree is the introduction of virtual bounding rectangles (VBRs) which contain and approximate MBRs or data objects. VBRs can be represented quite compactly and thus affect the tree configuration both quantitatively and qualitatively. First, since tree nodes can contain a large number of VBR entries, fanout becomes large, which increases search speed. More importantly, we have a free hand in arranging MBRs and VBRs in the tree nodes. Each A-tree node contains an MBR and its children VBRs. Therefore, by fetching an A-tree node, we can obtain information on the exact position of a parent MBR and the approximate position of its children. We have performed experiments using both synthetic and real data sets. For the real data sets, the A-tree outperforms the SR-tree and the VA-file in all dimensionalities up to 64 dimensions, which is the highest dimension in our experiments. Additionally, we propose a cost model for the A-tree. We verify the validity of the cost model for synthetic and real data sets. Edited by T. Sellis. Received: December 8, 2000 / Accepted: March 20, 2002 Published online: September 25, 2002     

A manufacturing XML schema definition and its application to a data management system on the shop floor

Digitization for sharing knowledge on the shop floor in the machinery industry has been given much attention recently. To help engineers use digitization practically and efficiently, this paper proposes a method based on manufacturing case data that has a direct relation to manufacturing operations. The data are represented in XML schema, as it can be easily applied to Web-based systems on the shop floor. The definitions were made for eight manufacturing methods including machining and welding. The derived definitions consist of four divisions of metadata, work-piece, process and evaluation. Three divisions except for the “process” division are common to the manufacturing methods. The average number of elements for a manufacturing method is about 200. The represented schema is also used to convey knowledge such as operation standards and manufacturing troubleshooting on the shop floor. Using the definitions, a data management system is developed. It is a Web-based Q&A system, in which the engineers specify the manufacturing case data mainly by selecting from the candidates. Then, the system fills in the blank portions and/or shows messages to help complete the case data. The proposed method is evaluated through practical scenarios of arc welding and machining.     

Reduced order model predictive control for constrained discrete‐time linear systems

A reduced order model predictive control (MPC) is discussed for constrained discrete‐time linear systems. By employing a decomposition method for finite‐horizon linear systems, an MPC law is obtained from a reduced order optimization problem. The decomposition enables us to construct pairs of initial state and control sequence which have large influence on system responses, and it also characterizes the standard LQ control. The MPC law is obtained based on a combination of the LQ control and dominant input sequences over the prediction horizon. The proposed MPC method is illustrated with numerical examples. Copyright © 2011 John Wiley & Sons, Ltd.     

Nanopillar array chip integrated with on-line stacking for fast DNA separation with high sensitivity and high resolution

Recent developments of nanofabrication techniques have created a trend switching from randomly ordered polymeric matrices, such as gel, to highly ordered sieving nanostructures in the separation of biomolecules. These nanostructures have enormous potential for fast separation of biomolecules, while nanostructure-based separation techniques suffer from critical scaling problems; they are efficient in handling less than nanoliter amounts of sample fluids, but most biomolecule samples are available in a liquid volume that is over several microliter, leading to a reduction in sensitivity and resolution. In this study, we developed a nanopillar array chip integrated with an easy and rapid on-line stacking method and achieved fast DNA separation with high sensitivity and high resolution. The developed on-line stacking method is based on the balance of two forces driven by electric fields: electroosmotic flow (EOF) and electrophoresis. The EOF mobility from the microchannel to the nanopillar-channel is drastically decreased, while, on the other hand, electrophoresis has constant mobilities in the whole length of the channels. The on-line stacking was realized at the well-balanced position of the two forces, and the on-line stacking using the nanopillar array chip can also be achieved within 10 s by just applying electric voltages without any other special reagents and materials. After applying on-line stacking using the nanopillar array chip, the relative fluorescence intensity increased 1,000-fold, and the resolution was twice as good as that without on-line stacking.     

Origin of coercivity changes during the oxidation of Fe3O4to γ-Fe2O3

Oxidation kinetics and x-ray diffraction of the intermediate products have been investigated for several kinds of Fe3O4powders during the oxidation to γFe2O3. From these results, a two-components-hypothesis as an intermediate state of the Fe3O4- γFe2O3system is proposed, instead of a homogenious solid solution which has been widely recognized. The effect of the changes in particle size caused by the two phases oxidation products on the variations of magnetic coercivity was emphasised.     

TEM,XPS and SIMS Analyzes on Grain Boundary of Lanthanum Chromites

The morphological characteristics, chromium valence state, and cation transport in the vicinity of grain boundary in La_1-xCa_xCrO₃ were investigated by using TEM/EDS, XPS and SIMS techniques. The width of grain boundary was around 1 nm where anomalous enrichment of calcium was observed. Higher valence state of chromium such as Cr⁶⁺(d⁰) was detected in the grain boundaries whereas Cr³⁺(d³) and Cr⁴⁺(d²) were dominant in the bulk. Very fast interdiffusion of alkaline earths was observed in the Sr²⁺-La_0.75Ca_0.25CrO₃ system. All observed phenomena were correlated by assuming the A-site vacancy which may be induced by the formation of Cr⁶⁺ at grain boundaries.