21,756 research outputs found
AN INTEGRATION OF HEURISTIC AND MODEL-BASED REASONING IN FAULT-DIAGNOSIS
No full textA human expert utilizes various pieces of diagnostic knowledge very dynamically in problem solving. Recently a few integrated reasoning systems have been proposed to use various types of knowledge in an integrated way, but they have shortcomings in reasoning control and reasoning interactions. To overcome these shortcomings, a diagnostic reasoning system with dynamic interactions that uses diverse types of knowledge with cooperation is proposed. The integrated diagnostic reasoning system contains heuristic and model-based reasoning modes. A type of knowledge in one reasoning mode is shared with another via transformation knowledge. In the integrated diagnostic reasoning system, the heuristic reasoning mode plays a major role in reasoning, and the model-based one fills the gaps in the heuristic reasoning mode. The model-based reasoning mode helps the heuristic one by supporting primitive-level testing, and by generating symptoms and hypotheses. In addition, it undertakes the remaining tasks if the heuristic reasoning mode fails. The heuristic reasoning mode, also, aids the model-based one by pruning the candidate set. By applying the integrated reasoning system to diagnosis of a computer printer circuit the system is shown to be appropriate for the domain that calls for the cooperative use of heuristic and detailed system description knowledge. With the criteria of efficiency and coverage, it has been shown that the proposed system is appropriate when insufficient symptoms and heuristic rules are provided
Lee Cruce
No full textPhotograph of L to R: WE Ledbetter, Eliza Cruce, Mrs. WG Cruce, Gene Cruce, Lee Cruce, Sallie Joe Dustin, Mrs. Lee Cruce, Gail Cruse, Mrs. WO Dustin, Lollie Dustin, Mrs. WA Ledbetter, Coraline Wynn Ledbetter, Birdie Dustin, Harold Young, Mrs. Young, Mr. Young, Colorado Springs, CO. Photo by JM Havis, Colorado Springs, CO, c. 1895
Choice of approximator and design of penalty function for an approximate dynamic programming based control approach
No full textThis paper investigates the choice of function approximator for an approximate dynamic programming (ADP) based control strategy. The ADP strategy allows the user to derive an improved control policy given a simulation model and some starting control policy (or alternatively, closed-loop identification data), while circumventing the 'curse-of-dimensionality' of the traditional dynamic programming approach. In ADP, one fits a function approximator to state vs. 'cost-to-go' data and solves the Bellman equation with the approximator in an iterative manner. A proper choice and design of function approximator is critical for convergence of the iteration and the quality of final learned control policy, because an approximation error can grow quickly in the loop of optimization and function approximation. Typical classes of approximators used in related approaches are parameterized global approximators (e.g. artificial neural networks) and nonparametric local averagers (e.g. k-nearest neighbor). In this paper, we assert on the basis of some case studies and a theoretical result that a certain type of local averagers should be preferred over global approximators as the former ensures monotonic convergence of the iteration. However, a converged cost-to-go function does not necessarily lead to a stable control policy on-line due to the problem of over-extrapolation. To cope with this difficulty, we propose that a penalty term be included in the objective function in each minimization to discourage the optimizer from finding a solution in the regions of state space where the local data density is inadequately low. A nonparametric density estimator, which can be naturally combined with a local averager, is employed for this purpose. (c) 2005 Elsevier Ltd. All rights reserved
Development of a markerless gene knock-out system for Mannheimia succiniciproducens using a temperature-sensitive plasmid
No full textA temperature-sensitive derivative of the Mannheimia varigena plasmid pMVSCS1 was constructed by hydroxylamine treatment for use in the development of a markerless gene knock-out system for Mannheimia succiniciproducens. The temperature-sensitive plasmid pMVSCS1-ts was stably maintained at 30 degrees C, but failed to replicate at 42 degrees C. DNA sequencing of the replication origin revealed a single base substitution as being responsible for its temperature sensitivity. The region of replication origin was amplified by PCR to construct an Escherichia coli-M. succiniciproducens shuttle vector pME19-ts to further examine the thermosensitivity. To make markerless mutants of M. succiniciproducens, the Cre-lox system with the variant lox66 and lox71 sites was used to prevent the instability caused by multiple loxP sites in the genome. The transient cre expression was carried out using the temperature-sensitive plasmid pCRX5, which was consequently cured after the verification of the markerless mutant by growing cells at 42 degrees C. For the demonstration of the markerless deletion of multiple genes using this method, the ldhA gene and the oadGAB operon of M. succiniciproducens encoding lactate dehydrogenase and oxaloacetate decarboxylase, respectively, were successfully deleted sequentially. This markerless deletion method should be useful for further metabolic engineering of M. succiniciproducens, which is a promising industrial bacterium for succinic acid production from renewable resources.The authors thank Stefan Schwarz and Oh Suk Kwon for
providing the plasmids pMVSCS1 and pMS3, respectively.
The authors also thank Hyohak Song and Seh Hee Jang for
their helpful discussion. This work was supported by the
Genome-Based Integrated Bioprocess Development Project
of the Ministry of Science and Technology through the
Korea Science and Engineering Foundation (KOSEF).
Further support by the LG Chem Chair Professorship and
the Center for Ultramicrochemical Process Systems sponsored
by KOSEF is appreciated
Experimental observation of flow instability in a semi-closed two-phase natural circulation loop
No full textIn this experimental study, the flow instabilities within a semi-closed two-phase natural circulation loop were examined, with an emphasis placed on the role of the expansion-tank-line resistance. Six different modes of loopwise natural circulation were identified: the single-phase natural circulation, periodic two-phase natural circulation with a nonboiling period between the cycles, two-phase continuous circulation (stable circulation), and three other modes of the two-phase natural circulation characterized by different ranges of the cyclic period. The results were also shown in the instability map in the plane of the heat Aux and the heater-inlet subcooling. When the frictional resistance at the expansion-tank line becomes larger, the circulation becomes stable, especially at the high heat-flux and high inlet-subcooling conditions, and, as a whole, the stable operation region becomes larger in the instability map. Similarly, the longer expansion-tank line stabilizes the system. However, unlike the analytical prediction, the excursive instability was not identified with the semi-closed loop due to the flow restriction at the expansion-tank line. (C) 2000 Elsevier Science S.A. All rights reserved
Genetic Engineering for Xenotransplantation （Transgenic Pigs for HLA-II in the Study of Xenotransplantation）.
No full textThe role of video-assisted thoracic surgery in the diagnosis and treatment of indeterminate pulmonary lesion.
No full textCO2 hydrate behavior in the deep ocean sediments; phase equilibrium, formation kinetics, and solubility
No full textThree-phase equilibria (H-L-W-V) for CO2 and NaCl solutions containing clay were measured to examine both electrolyte and capillary effect inside interlayer pores. Equilibrium line of 3 wt% NaCl and 10 wt% clay system was a little shifted to left side of 3 wt% NaCl solutions, which indicated that the injection of carbon dioxide into ocean sediments required higher pressure. CO2 hydrate formation kinetics was also attempted at 274.15 K and 30 bar. When clay minerals were added, the final consumption of CO2 decreased, but initial formation rate increased. Two-phase equilibria of CO2 hydrate and water solution eliminating gas phase particularly measured to simulate more closely actual deep sea condition. The overall results of this study would be used for estimating carbon dioxide injection depth and formation rate in sequestration process and making out solubility tendency in the deep sea
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